ANTEREOR CRUCZATE LESAMENT
PROSTf'EESiS 3% THE BUG

Thesis for the Degree of M S;
MECHIfiAN STATE UNI‘J‘ERSW
BHOLA i‘éATH GUPTA

1967

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ABSTRACT A
ANTERIOR CRUCIATE LIGAMENT
PROSTHESIS.IN THE DOG

by Bhola Nath Gupta

Replacement of the anterior cruciate ligament with a synthetic
prosthesis was performed on 10 experimental dogs. The proSthesis con-
sisted of a cord of braided dacron coated with silicone rubber as insu-
lating material. The outer covering of silicone rubber was made radio-
paque by incorporating barium sulfate.

After the 4th postOperative week, all dogs gained functional use,
without lameness, of the leg with a prosthetic anterior cruciate liga—
ment. Disuse atrOphy of the muscles of the hind legs was not noticed in
any case. Very slight to moderate anterior drawer movement of the tibia
could be produced when the dogs were anesthetized. Rupture of the pros-
theses occurred in 7 dogs between the 2nd and 4th postOperative month.
Confirmatory diagnoses were obtained by radiographs and post-mortem
examination.

At the time of necrOpsy, the joint operated on appeared identical
to the control joint, with the exception of some thickening of the
joint capsule and, in a few cases, a cloudy appearance of the synovial
There was regeneration of the anterior cruciate ligament in 3 dogs.
Histologically, the regenerated ligaments were identical to normal cru-
ciate ligaments; however, evidence of chronic foreign body tissue reaction

was present.

Bhola Nath Gupta

Superficial horizontal flaking of the articular cartilage, vertical
splitting of the medial meniscus and chronic inflammatory foreign body
tissue reaction of the joint capsule were observed microsc0pically.

Breaking strengths of normal cruciate ligaments, fascia lata, skin
and braided dacron were determined on a tensile testing instrument; the
average breaking load for the anterior or posterior cruciate ligament
was similar. The breaking load of the braided dacron was less than for
the anterior cruciate ligament, and it decreased after moist heat steri-
lization.

It was concluded that the prosthesis made of dacron covered with
silicone rubber was unsatisfactory due to loosening of the coating and
rupture of the dacron, even though the prosthesis appeared to function

in a satisfactory manner initially.

ANTERIOR CRUCIATE LIGAMENT

PROSTHESIS IN THE DOG

By

Bhola Nath Gupta

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

'MASTER OF SCIENCE

Department of Veterinary Surgery and Medicine

1967

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(j'gygi2;/¢n

Dedicated to my brother

Teknarayan

ii

ACKNOWLEDGEMENTS

The author wishes to express his sincere.appreciation to Dr. W. O.
Brinker, his major advisor, for his encouragement, supervision and
assistance throughout this investigation. Appreciation is also expressed
to Dr. G. H. Conner for his constructive criticism and critical reading
of this manuscript.

My sincere thanks and appreciation are expressed to Dr. R. G.
Schirmer and Dr. D. A. Schmidt for their guidance as teacher and friend
and for their ever-readiness to assist. Appreciation and thanks are
due to Dr. R. W. Van Pelt, Dr. U. V. Mostosky, and Dr. K. N. Subramanian
for their generous assistance with various aspects of this investiga-
tion. Special thanks are also extended to Dr. Patricia Fales for her
assistance during surgery.

For a successful completion of research and graduate training,
numerous people are involved who have assisted, advised, trained, and
encouraged in every phase of this research. The author is indebted to
Dr. J. A. Moore, Dr. K. K. Keahey, Dr. June H. Platt, Dr. K. M. Prasad,
Dr. R. D. Prasad, Miss Dixie L. Middleton, Miss Irene J. Brett, Miss
Rachel J. Rich, and Mrs. Janet Sharon.

My sincere appreciation and thanks are extended to Dow Corning
Center for Aid to Medical Research, Midland, Michigan, for the prepara-

tion and supply of the prostheses for this study.

iii

TABLE OF CONTENTS

INTRODUCTION. . . . . . . . . . . . . . . . . .
REVIEW OF THE LITERATURE. . . . . . . . . . o .

Veterinary Literature. . . . . . . . . . .

The Tensile Strength of Selected Body Tissues. . . . . .

Pathologic Changes . . . . . . . . . .
Anatomy of the Cruciate Ligaments. . . . .
MATERIALS AND METHODS . . . . . . . . . . . . .
Hematologic Study. . . . . . . . . . . . .
Radiologic Study . . . . . . . . . . . . .

POSt-Mortem Examination. 0 o o o o o o o 0

Determination of Breaking Strength of Cruciate Ligaments

Strips of Fascia Lata. . . . . . . . . . .
Strips of Skin . . . . . . . . . . . . . .
Braided Dacron . . . . . . . . . . . . . .
RESULTS . . . . . . . . . . . . . . . . . . . .
Gait . . . . . . . . . . . . . . . . . . .
Drawer Sign and Range of Movement. . . . .
Radiographic Observations. . . . . . . . .
Gross Pathologic Observations. . . . . . .
Histopathologic Observations . . . . . .

Breaking Strength of the Combined Anterior
Cruciate Ligaments . . . . . . . . . . . .

and Posterior

O O O O O 0 0

Breaking Strength of Anterior Cruciate Ligaments . . . .

iv

Page

13
15
l6
19
27
35
35
36
46
46
46
47
47
49
49
61

65

69

76

Breaking Strength of Posterior Cruciate Ligaments.

Breaking Loads of Strips of Fascia Lata, Skin and
Braided Dacron . . .

DISCUSSION. .

SUMMARY .

CONCLUSIONS .

BIBLIOGRAPHY.

Page

76

76
80
83
85

86

Table

10

LIST OF TABLES

Breed, sex, estimated age and body weight of experi-
mental dogs used for cruciate ligament surgery. . . . . .

Interval between cruciate ligament operation and

euthanas 18 O O O I O O O O O O O O O O O O O O O O O O O O '

Postoperative swelling and tenderness of the stifle
jaint O O O O O O O O O O O O O O ‘0 O O O ’0 O O O O O O O

Postoperative functional recovery evaluated during a
8 low walk 0 O O O O O O O O O O O O O Q C I I O O O I O I

The condition of the silicone covering of the prosthesis
as observed by radiography. . . . . . . . . . . . . . . .

Gross examination of the stifle joints with prostheses
after euthanas 1a 0 O O O O O O O A. O O O O 0 O I '0 O O I 0

Breaking load of the combined anterior and posterior
cruciate ligaments. . . . . . . . . . . . . . . . . . . .

Anterior cruciate ligament breaking loads . . . . . . . .
Posterior cruciate ligament breaking loads. . . . . . . .

Breaking load of braided dacron . . . . . . . . . . . .

vi

Page

20

28

48

50

52

62

75
77
78

79

LIST OF FIGURES
Figure Page

1 Sagittal section of the stifle joint, showing the
attachments of the anterior (A) and posterior (B)
cruciate ligaments. . . . . . . . . . . . . . . . . . . . l7

2 Surgical instruments used in cruciate ligament pros—
theSiS O O O O O O O O O O O O C O O O O O O O O O O O O I 23

3 (A) Prosthesis stored in a plastic bag; (B) piece of
prosthesis, the outer coating of silicone rubber
removed at both ends to show the central dacron cord;
(C) the same piece kept in petri dish; and (D) ready
for sterilization . . . . . . . . . . . . . . . . . . . . 24

4 Skin incision over the anterio-lateral aspect of the
stifle jOintI O O C I O O O O O O O O O O O O O O I O O O 29

5 The patella displaced medially to expose the stifle
joint . . . . . . . . . . . . . . . . . . . . . . . . . . 30
6 Application of the drill guide to the femur . . . . . . . 31
7 The pilot hole made into the femur is being enlarged
to accommodate the prosthesis . . . . . . ._. . . . . . . 32
8 The prosthesis passed through the femoral tunnel. . . . . 33
9 Application of the drill guide to the tibia . . . . . . . 34
10 Lateral radiograph of normal stifle joint . . . . . . . . 37
ll Lateral radiograph of the right stifle immediately

after surgery. Prosthesis in situ. . . . . . . . . . . . 38

12 Radiograph of the right stifle (postero-anterior view
immediately after surgery. Prosthesis ig_situ. . . . . . 39

13 Lateral radiograph of the right stifle taken post-
operatively. Prosthesis ig_situ. . . . . . . . . . . . . 40

14 Radiograph, postero-anterior view, of the right stifle
after surgery, showing the prosthesis in place. . . . . . 41

15 The tensile testing instrument, "Instron" . . . . . . . . 43

vii

Figure Page

16 The specimen, showing stretched cruciate ligaments

(arrow) under strain while the cross-heads (A) were

mOVing apart 0 C O I O O O O O O O O O O O O O O O 0 O O 45
17 Position for testing for anterior drawer movement of

the tibia O O O O O O O O 0 O O O O 0 O O 0 O O O O O O 51

18 Lateral radiograph of the right stifle, 2 months post-
0peratively. Note the broken prosthesis (arrows) . . . 54

19 Radiograph, postero-anterior view, of the right stifle,
2 months after surgery, showing the broken pros-
thesis (arrow). . . . . . . . . . . . . . . . . . . . . 55

20 Lateral radiograph of the right stifle taken 7 months
after surgery. Note the pieces of silicone rubber
within the joint (arrow). . . . . . . . . . . . . . . . 56

21 Radiograph, postero-anterior view, of the right
stifle, 7 months postoperatively. Note the broken
prosthesis (arrows) . . . . . . . . . . . . . . . . . . 57

22 Lateral radiograph of the right stifle 12 months after
surgery. Two pieces of silicone rubber within the
jOint (arrOW) O O O O O O O O O O O O O O O O O O O O O 58

23 Radiograph, postero-anterior view, of the stifle joint
6 months after surgery. . . . . . . . . . . . . . . . . 59

24 Radiograph, postero-anterior view, of the right stifle,
9 months post0peratively. Note the separation of the
radiOpaque silicone rubber (arrow) within the joint . . 6O

25 Two pieces of silicone rubber (outer covering of the
prosthesis) found inside the stifle joint at post-
mortem examination. 0 O O O 0 O O O 0 O O O O O O O O O 64

26 One end of the broken dacron cord inside the stifle
joint noticed at post-mortem examination. . . . . . . . 64

27 Regenerated anterior cruciate ligament (arrow) noticed
at pOSt-mortem examination. 0 o o o o o o o o o o o o o 64

28 Horizontal flaking (arrow) of the articular cartilage
Of the femur O O O O O O O 0 O I O I O O O O O O O O I O 66

29 Horizontal flaking (arrow) and shredding (a) of the
articular cartilage of the femur. . . . . . . . . . . . 66

.30 Pitting (arrow) in the stratum superficialis of articu-
lar cartilage of the femur. . . . . . . . . . . . . . . 67

31: Vertical splitting (arrow) in the medial meniscus
(arrOW) O O I O O O O 0 O O C O O O O O C O O C O 0 0 O 67
viii

Figure Page

32 Normal medial meniscus. Note the interwoven colla-
gen fiber bundles. Longitudinal section (1) and
transverse section (2) of collagen fiber bundles. . . . 68

33 Normal joint capsule. Stratum synoviale (A) and
stratum fibrosum (B). . . . . . . . . . . . . . . . . . 68

34 Joint capsule from the stifle joint. Note the edema
of the stratum fibrosum and numerous Villi in the
stratum.synoviale . . . . . . . . . . . . . . . . . . . 70

35 A higher magnification of synovial villi and frag-
mented dacron fiber (1) shown in Figure 34. Note the
Langhans' type giant cells (a) and foreign body giant
cells (b) . . . . . . . . . . . . . . . . . . . . . . . 70

36 A higher magnification of synovial membrane from the
stifle joint. Note the Langhans' type giant cell
(A) with fragmented dacron (arrow). . . . . . . . . . . 71

37 A higher magnification of foreign body type giant cell
(A) in the stratum synoviale. Note the phagocytized
fragmented dacron fibers (arrow). . . . . .'. . . . . . 71

38 Regenerated anterior cruciate ligament. Note the
numerous blood vessels (a), proliferated synovial
intimal cells (b) at the perimeter, phagocytized
dacron fibers (c), and collagen fibers and fibro-
blasts (d). . . . . . . . . . . . . . . . . . . . . . . 72

39 A higher magnification of regenerated anterior cru—

ciate ligament shown in Figure 38. Note the blood

vessels (a) O O O O O O O O O O O O O O O O O O O O O O 72
4O Regenerated anterior cruciate ligament. Note the

Langhans' type giant cells (a) with phagocytized
dacron fibers, loosely arranged collagen fibers and
fibroblasts (b) . . . . . . . . . . . . . . . . . . . . 73

41 Normal anterior cruciate ligament. Synovial fibro-
blasts (A); fibroblasts and collagen fibers (B) . . . . 73

42 Transverse section of the dacron cord from the stifle

joint. Note the infiltration of fibroblasts and

collagen fibers in between the dacron fibers (A). . . . 74
43 A higher magnification of the dacron cord shown in

Figure 42. Note the infiltration of fibroblasts and

collagen fibers (arrow) in between the dacron fibers
(A) O O O O O I O O O O O O O I O O O O O O O O O O O O 7 4

ix

INTRODUCTION

Rupture of the anterior cruciate ligament is the most common serious
derangement of the canine stifle joint. Recent advancements in canine
surgery have made repair of the ligament possible, but the exploration
for better ligament repair and for more sophisticated techniques remains
a major challenge. While the necessity for surgical repair of the liga-
ments of the stifle joint has been debated for a number of years, the
fact that ruptured cruciate ligaments produce functional disturbances,
which often prediSpose the joint to trauma and subsequent osteoarthritis,
cannot be denied.

The usual methods of repairing the cruciate ligaments are well
known. Strips of fascia, skin, ligament, tendon, and synthetic materials
like nylon, teflon or dacron have been used for ligament replacement
in experimental and clinical cases by different workers.

This study was designed to determine the tensile strength of cru-
ciate ligaments, skin, fascia, and a synthetic material selected for
its replacement. A clinical evaluation of a prosthesis for the anterior
cruciate ligament was also conducted in experimental animals. Labora-
tory evaluations included: histopathologic study of the different
structures involved and radiologic and hematologic studies after using

the prosthesis.

2
The synthetic material used in this study to replace the anterior
cruciate ligament in the dog was braided dacron* (polyethylene glycol

terephthalate) insulated with silicone rubber.**

 

*Dacron Round Suture, Size D 1—6, American Silk Sutures, Inc.,
Roslyn Heights, N.Y.

**Silastic,R Dow Corning, Midland, Michigan.

REVIEW OF THE LITERATURE

Veterinary Literatggg,

‘Among the earlier references to rupture of the anterior cruciate
ligament in veterinary literature was a case recorded by Brook (1932)
in which a 9-1/2-year-old Scottish Terrier was struck by a car in its
early puppyhood. Following the accident, the dog had intermittent pain
in the stifle joint and did not use the leg completely. On physical
and radiographic examinations, a diagnosis of ruptured anterior cruciate
ligament was made which was confirmed on postwmortem examination.

In a discussion of the internal derangement of the stifle joint in
dogs, Paatsama (1952) cited the following authors: Mgller and Frick
(1899), name: (1908), Uebele.(l910), Handel (1910), Carlin (1926),
Schwerdtfeger (1937), Forssell (1938), and Jarosch (1940).

According to Schroeder and Schnelle (1936), rupture of the cruciate
ligaments may not be repaired completely. They reported that fixation
of the joint for 3 to 6 weeks resulted in good functional recovery. A
padded bandage was passed around the anterior surface of the proximal
end of the tibia and fastened to the posterior bar ofna Thomas splint.
The leg was fixed with forward lift of the thigh towards the anterior
bar and backward pull on the proximal end of the tibia to the posterior
bar. For rupture of both cruciate ligaments, the same plan was followed.
In addition, the tarsal joint was also fixed in more acute flexion.

Osteoarthritis of the stifle joint was reported by Schnelle (1941).
Injuries to the ligaments within the.joint which allowed extra motion,

3

4
caused increased wear of the joint surface and resulted in osteoarthri-
tis. He further stated that the stifle joint was the most frequent site
for arthritis.

During 1941, Schroeder and Schnelle again reported a case of rup-
tured anterior cruciate ligament. Their conservative treatment consisted
of fixing the limb in a semiflexed position under moderate traction in
a Thomas splint for 3 to 6 weeks.

Nilsson (1949) published a detalied account of the lesions of the
menisci and osteoarthritis on the basis of etiology, pathology, diag-
nosis, therapy and the prognosis of the stifle joint injuries.

Paatsama (1952) was the first to closely study canine stifle in—
juries. He devised a method for replacement of the ligament with a
strip of fascia. This technique has become accepted universally, al-
though more recently different materials have been suggested for the
replacement. A l-cm. wide strip of fascia lata was used as a substi-
tute for the anterior cruciate ligament. The fascial strip retaining its
distal attachment was pulled through the femoral and tibial tunnels and
was then slightly twisted. The free end of the strip was sutured to the
insertion of the straight patellar ligament on the tibial tuberosity.

The leg was fixed in a Thomas splint for 15 days. In studying this
problem experimentally in dogs, he incised the anterior cruciate liga-
ment and observed the resulting clinical and pathologic changes. Pro-
gressive osteoarthritic changes occurred in the joint which were readily
observed after 2 to 3 weeks.

Autogenous and homogeneous transplantation of the whole stifle
joint was performed in dogs by Herndon and Chase (1952). In this experi-

ment, the deeper layers of cartilage cells remained viable but some

5
degeneration of the articular cartilages of the femur and tibia resulted.
Aseptic necrosis began superficially and peripherally to the weight
bearing surface of the joint. These cartilages were eventually replaced
by fibrous tissue. They concluded that good results may be expected in
non-weight bearing joints. ‘

Paatsama (1954) further made a survey of the structures of the
meniscus from the canine stifle joint. He obtained menisci from dogs
having internal derangements of the stifle joint and examined them
grossly as well as microscopically. In experimental dogs, the cruciate
ligaments and menisci were removed partially or completely to study the
pathologic changes due to the development of osteoarthritis. Large dogs
developed the pathologic changes in a much shorter time than did the
smaller ones. Increase of chromotropic substance, hyalinization, slit
formation, fatty degeneration and colliquative necrosis were found in
old dogs, particularly in cases of joint injuries. These changes were
observed within 50 days after cutting the cruciate ligament.

New tendons and articular ligaments were prepared from fascial
strips by Markowitz (1954). He reported that dog fascia was thinner and
more difficult to manipulate than human fascia. An anterior cruciate
ligament was prepared from a fascial strip and passed through the oblique
tunnels drilled into the femur and tibia. The free ends were stitched
to the periosteum and bone with silk.

Singleton (1957) briefly described the general and functional
anatomy of the stifle joint in the dog. Methods for the diagnosis and
treatment of some stifle abnormalities were also included with particu-
lar reference to anterior cruciate ligament repair. He used a 1-cm.

wide strip of fascia lata to repair the ruptured anterior cruciate

6
ligament. The fascial strip was rolled in gauze and soaked in physiologi-
cal saline solution until used. It was threaded through the first
tunnel made in the femoral condyle, passed across the joint and through
the second tunnel in the tibial crest. The free end of the strip was
secured by 2 screws, one of which passed through the tunnel and the
other through the ligament as it emerged from the distal end of the
tibial tunnel. The limb was placed in a plaster cast for 2 weeks.
Usually, the dogs started using the limb 3 weeks after removal of the
cast.

A thin strip of skin from the parapatellar area was used by Gibbens
(1957) as a substitute for the anterior cruciate ligament. The strip
was placed in 1:1000 quaternary ammonia solution to inhibit hair growth.
The strip of skin was passed through the joint and the proximal end was
turned downward along the lateral collateral ligament. The joint was
slightly flexed and the transplant was pulled taut and anchored with
steel wire to the lateral collateral ligament and fascia above and
below the joint. The leg was kept in a Thomas splint for 14 days.
Satisfactory recovery was reported after 6 months.

Titkemeyer and Brinker (1958) used a 3/8-inch wide fascial strip
for replacement of the anterior cruciate ligament. The primary skin
incision was continued medially below the joint. The distal attachment
of the fascial strip remained intact and the free end of the strip was
passed through the drilled holes in the femur and tibia and securely
sutured to the patellar (quadriceps femoris) tendon. Good results were
reported after keeping the limb in a Thomas splint for 3 weeks.

Rathor (1959) reported on a comparative study using the tendon of

the peroneus longus muscle, skin and strips of fascia lata as substitutes

7
for the anterior cruciate ligament. After surgery the leg was fixed in
a Thomas splint for 3 weeks. On clinical examination after 8 to 9
weeks, most of the dogs had a normal gait while walking or running but
a moderate degree of anterior drawer movement was noticed in all dogs.
In some cases, arthritic changes were seen and the articular cartilage
underwent aseptic necrosis. Rathor concluded that the transplantation
of tendon in the stifle joint was superior to fascia or skin.

Chastain (1959) used a strip of skin for the repair of anterior
cruciate and medial collateral ligaments in experimental dogs. The
skin strip was kept in 1:1000 aqueous quaternary ammonia solution until
used. The femoral tunnel was drilled from the medial side at the origin
of the medial collateral ligament. The skin strip was passed through
the femoral and tibial tunnels. The distal and proximal ends of the
transplant were sutured with femoral and tibial insertions of the medial
collateral ligament, respectively. The leg was immobilized in a Thomas
splint for 14 days.

Johnson (1960) described an operation in which braided nylon was
substituted for the anterior cruciate ligament. The prosthesis con—
sisted of several strands of braided nylon which were passed through
holes drilled in the femur and tibia. The proximal and distal ends of
the prosthesis were anchored to Sherman type vitallium screws suitably
fixed transversely to the lateral femoral condyle and the medial sur-
face of the tibia below the tibial tuberosity. The leg was immobilized
in a Thomas splint for 2 to 3 weeks.,

Leonard (1960) modified Paatsama's technique of fascial replacement
for rupture of the anterior cruciate ligament. The tibial hole was

drilled at the tibial insertion of the anterior cruciate ligament and

8
was directed toward the flat surface of the tibia just medial to the
tibial crest and slightly distal to the medial condyle. The joint cap-
sule and the fascial opening were closed with stainless steel wire.
The leg was not splinted.

Emery and Rostrup (1960) used teflon fabric woven material for the
replacement of the anterior cruciate ligament in experimental dogs.
After passing the teflon prosthesis through the femoral and tibial tun-
nels, the upper end of the teflon was knotted to itself and the lower
end was stapled to bone on the medial side and then sutured to itself
with silk. Using this technique, slight drawer movement was detected
postsurgically. The leg was immobilized in a single hip spica for 3
weeks. After 3 months, anterior drawer movement was still present in
all operated stifle joints. At post-mortem examination, fraying of the
teflon was noticed in some dogs.

Berge and Westhues (1961) reported the use of braided nylon as the
anterior cruciate ligament prosthesis. A set of 2 converging tunnels,
l'cm. apart, were drilled into the femoral and tibial condyles laterally
and medially, respectively. The 2 sets of tunnels converged at the,
origin and insertion of the anterior cruciate ligament. Two to 4 folds
of nylon filament were passed through the tibial tunnel, then to the
femoral tunnel and again to the 2nd femoral tunnel and finally pulled
through the 2nd tibial tunnel. The ends were pulled taut and a few
square knots were placed medially.

In dogs and cats, Leighton (1961) used a strip of skin to replace
the ruptured anterior cruciate ligament. After passing the skin strip
through the femoral and tibial tunnels, the free ends were sutured to

fascia with wire. The leg was fixed in a Schroeder-Thomas splint. A

9
reasonably functional joint resulted. In his experience, skin proved
to be better than fascia transplantation.

Foster E£m§l° (1963) reported on closed joint repair of anterior
cruciate ligament rupture in dogs. A l/4-inch wide strip of skin was,
taken from the edge of the incision and used as the prosthetic ligament
without opening the joint capsule. A pin was directed ventromedially
so as to drill through the lateral condyle of the femur into the joint
cavity and exit from the tibia, medial to the tibial crest. A strip of
skin was passed through femoral and tibial tunnels. A 2nd hole was
drilled through the tibial crest and the distal end of the strip was
passed through it. Finally, both ends of the strip were sutured on the
lateral aspect of the stifle joint.

Vaughan (1963) replaced the anterior cruciate ligament with fascia,
skin and nylon separately on 3 groups of dogs. No external support was.
provided to the operated limb. The dogs were observed for only 3 months.
Radiographs of the treated joints were taken every month, and no untoward
bone or joint changes were detected. He made a comparative study of 3
types of prostheses and found that the whole thickness skin was superior
to either fascia or nylon as a replacement material for the anterior
cruciate ligament.

Ormrod (1963) made reference to an ingenious method of Singleton
for repair of the anterior cruciate ligament rupture. The latter used
a multistrand monofilament nylon prosthesis without recourse to screws.
The ends of the nylon strands were passed through converging tunnels
drilled in the lateral femoral condyle and emerging at the proximal'
attachment of the anterior cruciate ligament into the intercondyloid

fossa. A 100p was thus formed that bore against the lateral surface of

10
the bone when the prosthesis was drawn tight. A 2nd system of tunnels
was drilled from 2 points on the medial aspect of the tibia below the
level of the tibial tuberosity. The 2 tunnels converged at the normal
point of distal attachment of the anterior cruciate ligament. The ends
of the 100p were passed through these tunnels and tied against the bone.

Stainless steel buttons were used by Ormrod (1963) to hold the
multistrand monofilament nylon as the anterior cruciate ligament pros-
thesis. Both ends of the monofilament nylon, previously passed through
the 2 holes of a small stainless steel button, were threaded through
the femoral tunnel and drawn anteriorly through the Open stifle joint.
This button served the purpose of a toggle against the lateral femoral
condyle, laterally. The free ends of the prosthesis were passed through
the tibial tunnel and finally through a transverse tunnel below the
tibial crest. Another stainless steel button was threaded onto the
nylon filaments and tied off against the button on the lateral side of
the tibia.

Pearson and Garret (1964) used a modification of Paatsama's tech-
nique employing a strip of fascia lata. They did not feel it essential
to fix the leg in a Thomas splint when nonabsorbable suture material had
been used to close the joint capsule and fascia.

Teflon mesh was used by Butler (1964) as a prosthetic material for
repair of ruptured anterior cruciate ligaments.' In this experiment 9
dogs (4 were clinic cases) and 6 cats (1 was a clinic case) were used.

A teflon strip was passed through femoral and tibial tunnels. Its proxi-
mal end was sutured with stainless steel wire to the tendon of origin of
the long digital extensor muscle laterally. The distal end of the teflon

strip was then passed through the transverse hole made through the tibial

ll
crest and was brought forward and around the anterior aSpect of the
tibial crest to a point where it originally entered the hole on the
medial aspect. At this point the teflon was tied to itself so as to
anchor the distal end of the prosthesis. No external splint was applied.
Butler mentioned that the teflon prosthesis was completely infiltrated
with fibroblasts and connective tissue fibers between the teflon fibers
and that 6 months after surgery it appeared as a smooth glistening ligament.

Strande (1964) made a study of the replacement of the anterior cru-
ciate ligament in the dog by the tendon of flexor digitalis pedis longus.
The tendon was dissected free and cut through outside the medial malleolus.
The free end of the tendon was passed through the tunnels made in the
tibia and femur, respectively, and finally sutured to the lateral col-
lateral ligament with size 00 silk. The leg was fixed in a Thomas splint
for 14 days.

Leighton (1964) reported the rupture of the feline anterior cruciate
ligament, but this condition was not found as commonly as in the dog.

He used strips of skin for repair, followed by immobilization with a
Thomas splint for 1 week.

A drill guide for use in repair of ruptured cruciate ligaments in
the dog was designed by Brinker g; 31. (1965). They concluded that it
aided materially in accomplishing the main objective of replacing the
substitute for the ruptured anterior cruciate ligament in its proper
anatomical position.

In an article pertaining to the diagnosis of stifle lameness in the
dog, Keller (1965) pointed out that etiological factors such as luxation
or subluxation, fractures, torn ligaments, congenital abnormalities and
chronic arthritis must be considered. He also described the different

methods of examination of the stifle joint.

12

Dueland (1966) introduced a new surgical technique for replacement
of the anterior cruciate ligament in dogs based upon a procedure developed
for man by Jones (1963). Dueland used a strip of tissue composed of
quadriceps tendon, a V-shaped piece of anterior patella and the middle
third of the patellar tendon to replace the anterior cruciate ligament.

A 1/4 to 3/8-inch wide strip of tendon was separated by 2 parallel
incisions. This strip was left attached to the patella in the middle and
tibia distally. A rotary dental drill unit was used to cut a wedge-
shaped piece of bone from the anterior middle third of the patella with-
out disturbing the articular surface. This new ligament was passed
through the drilled hole in the femur. Ideally the patellar piece
wedged firmly within the femoral tunnel. The free end of the strip was
sutured to the lateral femoral fascia. The leg was fixed in a Thomas
splint for 4 weeks. Functional recovery was achieved in 5 to 12 weeks.

Ryan and Drompp (1966) also used the patellar tendon to replace the
anterior cruciate ligament in dogs. They used the same technique as
described by Dueland (1966). After surgical Operation, the leg was fixed.
in a cylinder cast of wire screen.

Strande (1966a, b) made a further report for repair of the anterior
cruciate ligament using the patellar tendon and a triangular piece of
patella. He employed the same technique as develOped by Jones (1963).

The free end of the newly constructed ligament was sutured to the lateral
collateral ligament with size 00 stainless steel wire. The limb was
immobilized in a Thomas splint for 14 days.

Childers (1966) described a simple surgical procedure for repair of
the ruptured anterior cruciate ligament without Opening the joint capsule.

After making skin incision, lO interrupted Lembert inverting sutures

13
were placed 5 mm. apart in the underlying fascia over the lateral sur-
face Of the stifle joint. Chromic cat gut was used and maximum tension
was applied over the sutured fascia. The use Of the Thomas splint to
fix the leg after surgery was advised. Encouraging results have been

reported using this technique.

The Tensile Strength of Selected Body Tissues

Gratz (1931) first reported on the tensile strength and elasticity
of human fascia lata. Test material was obtained from the thighs Of
patients who were at the time undergoing Operations. A small piece Of
fascia lata was kept in saline-moistened gauze and the tensile strength
determined on a standard tension machine used for the general testing
of engineering materials. Elapsed time between removal Of the test
piece Of fascia lata and actual testing Of the material varied from 2
to 18 hours. A 66-pound pull was enough to break an 0.6 inch wide and
0.014 inch thick piece Of fascia lata.

Mason and Allen (1941) studied extensively the rate Of tendon
healing in dogs. Their evaluations were based on the tensile strength
Of the healing tendon. Tendons of the extensor carpi radialis and flexor
carpi ulnaris muscles were divided transversely and then sutured with
silk. The leg was immobilized in a plaster cast to hold the sutured
tendon in relaxation. The tensile strength Of the sutured tendon was
determined on a spring scale at intervals varying from 2 to 68 days.

Kernwein (1942) implanted tendon into bone in dogs and then measured
its tensile strength. The tendon of the extensor carpi radialis longus
muscle was transplanted bilaterally into the radius. The breaking

strength Of its natural insertion into the bone was also tested and more

14
than 50 pounds was required to separate the tendon from bone. The musculo—
tendinous junction separated in some dogs with a pull of 27 to 38 pounds.
It was deduced that the tensile strength Of the normal physiological
fixation Of the tendon to bone was greater than the musculo-tendinous
junction.

Mathur and McDonald (1949) determined the breaking strength Of the
lateral and medial menisci of the knee Of man and dog. They used a
specially designed instrument which held the ends Of the meniscus with
metal clamps. One end was fixed to the horizontal bar on the tOp Of the
instrument and weights were added gradually to the platform at its
bottom. In most Of the cases, the medial meniscus Of the stifle joint
of dogs was found weaker than the lateral one. The breaking strength of
the lateral and medial menisci varied from 21 to 60 pounds.

Harrison and Adler (1956) tested the tensile strength Of calendered
weave of nylon before and after use as a vascular prosthesis in experi-
mental dogs. The tensile strength was determined with an "Instron" appa-
ratus. There was a loss of 83% Of tensile strength Of nylon after 6 months'
use. They stated that,

"One would expect hydrolysis to occur when the ma-
terial is subjected to the body fluids and slightly
elevated temperatures over a long period of time.
Proteolytic enzymes might aid in the hydrolysis by
attacking the amide group Of the nylon polymer. The
loss in strength of nylon is thought to be due more
to the chemical degradation than the physical force
to which it is subjected."

Gort and Rostrup (1959) tested the breaking strength Of the medial
collateral ligament Of canine stifle joints. They used teflon fabric

for its reconstruction. The breaking strength Of normal and reconstructed

medial collateral ligaments was determined on a Baldwin Hydraulic Tester

15

NO. 6-35. The femur and tibia were amputated from the proximal and distal
third, respectively. The joint capsule and all the ligaments Of the
stifle joint were divided except the teflon prosthetic ligament in one
limb and the medial collateral ligament Of the Opposite limb.

The tensile strength Of the canine anterior cruciate ligament was
tested by Emery and Rostrup (1960). The hind legs were amputated from
the proximal and distal third of the femur, tibia, and fibula, respectively.
The soft tissues around the bones were excised and all the femoro-tibial
attachments were divided except the anterior cruciate ligament. Its
breaking strength was tested with a Baldwin Hydraulic Tester NO. 6-35.
The ligament was torn free from its tibial attachment when 70 to 100
pounds Of tension were applied.

An attempt was made by Ryan and Drompp (1966) to evaluate the weight
which would be required to break the normal anterior cruciate ligament
Of dogs. In 3 cases, a total weight Of 181 pounds was not sufficient
to break the ligament. Unfortunately, the weight platform Of the test-
ing machine, used in the experiment, could not hold more than 181 pounds.
However, they were able to determine the breaking strength of recon-

structed anterior cruciate ligament which varied from 4 to 79 pounds.

Pathologic'Changgg
Pathologic changes in the stifle joint following rupture Of the
cruciate ligaments have been studied in both experimental and clinical
cases.- Experimentally, the first degenerative changes after sectioning
Of the anterior cruciate ligament were observed within 25 days and mild
to severe osteoarthritis within 51 to 78 days (Paatsama, 1952). In
larger and more active breeds, these changes were markedly extensive

(Brinker, 1965).

16

Usually the joint fluid increased in amount and xanthochromia was
present due to hemorrhage. The volume of the joint fluid continued to
increase in the next several weeks and the fluid became straw colored.
The ends Of the ruptured ligament appeared rounded and shrunken. The
articular cartilage became dull, granular and yellowish white in appear—
ance. Elevated osteoid tissue or fibrocartilage pearls called osteo-
phytes may have been present on each side Of the trochlear ridges. The
synovial membrane was markedly congested and the menisci may have begun
to show evidence of abnormal wear and tear (Brinker, 1965).

After several months without treatment, the joint capsule became
thickened, The synovial membrane was markedly congested and sometimes
appeared villous. The articular cartilage became more granular, duller,
and elevations of fibrocartilagenous osteoid tissue were more extensive
and larger. Evidence Of abnormal wear was present on the weight bearing
surface Of the articular cartilage covering the condyles and the menisci.
The medial meniscus usually showed more wear than the lateral one (Nilsson,
1949; Brinker, 1965).

After long-standing rupture Of the anterior cruciate ligament,
chronic proliferative changes of the joint capsule and supporting struc-
tures may partially stabilize the joint. The free anterior sliding move—
ment Of the tibia may be difficult to demonstrate if stabilization has

.taken place (Rudy, 1965).

Anatomy Of the Cruciate Liggments
The anatomy of the cruciate ligaments is Of great surgical importance
for their repair by substitution. As their name implies, they cross

each other on both the frontal and sagittal planes (Figure 1). In their

17

 

 

 

1;.GUP'I

Figure l. Sagittal section Of the stifle joint, showing the

attachments of the anterior (A) and posterior (B) cruciate ligaments.

l8
passage from origin to insertion, the ligaments wind around one another
by slight twisting, a phenomenon which is more distinct in large than in

small breeds (Paatsama, 1952).

Theiggterior (cranial or lateral) cruciate ligament. This ligament arises
by a broad origin from the anterior'intercondyloid fossa Of the tibia,
anterior to the tibial spine and between the anterior horns Of the
menisci. It passes obliquely and finds insertion on the medial surface

of the lateral condyle of the femur. It is crossed by the posterior

cruciate ligament medially (Dyce et al., 1952; Rudy, 1965).

The posterior (caudal or medial) cruciate ligament. The posterior cru-
ciate ligament is slightly heavier, stronger and definitely longer than
the anterior cruciate ligament. It arises from the medial surface Of
the pOpliteal notch Of the tibia and is inserted on the lateral surface
Of the medial femoral condyle. It lies medial to the anterior cruciate
ligament (Miller gtugl., 1964).

These ligaments are 2 powerful intra-articular bands serving to
connect the femur with the tibia and thus acting as a central fixation
apparatus (Titkemeyer and Brinker, 1958). In flexion, the forward dis-
placement Of the tibia is inhibited by the anterior cruciate ligament‘
and bakcward displacement is inhibited by the posterior cruciate ligament
(Dyce 3231., 1952).

The fact that the cruciate ligaments are set in the joint in both.
an antero-posterior and a medio-lateral Oblique plane accOunts for their
importance in stabilizing the joint, not only in an antero-posterior plane

but also against forces affecting rotation (Paatsama, 1952).

MATERIALS AND METHODS

The 10 dogs used as surgical subjects for this study were Of mixed
breeds as recorded in TABLE 1. Since they were Obtained from a pound,
each was kept in isolation for 15 days prior to transfer to the experi-
mental ward. All surgical patients were subjected to a complete physical
examination, including general appearance, integumentary, musculoskele-
tal, circulatory, respiratory, digestive tract, genito-urinary tract,
eyes, ears, lymph nodes, tonsils, and mucous membrane. The stifle joint
was examined for abnormal movement or evidence of previous injury.

Using a qualitative sugar concentration method (Modified.Sheather's
Sugar Flotation Technique, Benbrook and $1033, 1961), fecal samples were
examined for parasite ova. Those dogs harboring hookworms, ascarids or
whipworms were treated with disophenol,* piperzine citrate,** and
phthalofyne*** according to the recommended dosage. Examinations for
internal parasites were performed at regular intervals during the study.

Commercial dog food# was fed once a day and water was provided at
all times. Each dog was kept in a separate cage, but was permitted to
exercise for half an hour every morning and evening in separate indoor

runs .

 

*D.N.P., American Cyanamid Company, Princeton, N.J.
**Pipcide, Haver—Lockhart Loaboratories, Kansas City, Mo.
***Whipcide, Pitman-MOore, Indianapolis.

#Purina Dog Chow, Ralston Purina Company, Checkerboard Square,

St. Louis, Mo.
19

20

TABLE 1. Breed, sex, estimated age and body weight Of experimental
dogs used for cruciate ligament surgery.

 

 

 

Serial Case Age Body weight

NO. NO. Breed Sex (yr.) . (kg.)
1 104854 Cocker Spaniel F 3 . . 12.7
2 104888 Beagle M 3 14.5
3 106626 Airedale F 2.5 8.0
4 106627 Cocker Spaniel F 2 8.0
5 106629 Mongrel ‘ F 1 9.5
6 106630 Mongrel F l 9.5
7 106631 Beagle F 4 9.0
8 106632 MOngrel F 1.5 11.0
9 106634 Beagle M 2 13.0

10 107191 Cocker Spaniel F 3 6.3

 

21

Instruments used in the surgical procedure are shown in Figure 2.
All instruments and materials used during the surgical procedure were
sterilized in a High-Vac Sterilizer* at 275 F. for 3 minutes with pressure
varying from 29 to 32 pounds. The material used for prosthesis consisted
Of braided dacron coated with silicone rubber, cut in 8- to lO-inch
lengths (Figure 3). The outer coating was previously incorporated with
10% barium sulfate to render the prosthesis radiopaque.

Food was withheld from dogs for 12 hours prior to the surgical
Operation. The anesthetic was Pentobarbital sodium solution** (1 grain
in each ml.) given intravenously in the amount Of 1 ml. per.5 pounds Of
body weight or in amounts sufficient to produce surgical anesthesia.
Completeness of anesthesia was judged by eye and toe pinch reflexes.

The surgical site was prepared by clipping (Oster clipper, size 40
blade)*** the hair on the hind leg from the point of hip to the hock joint.
The leg was held in an upright position by means Of a gauze bandage tied
around the phalanges and secured to a transfusion stand. The entire
clipped-area was scrubbed 4 times with a surgical soap containing an
aqueous preparation of high molecular weight alkylaminehydrochlorides
composed of benzethonium chloride,# diluted 1:3 with water. Finally the
area was left wet with the surgical soap solution. Care was taken to

protect the scrotum or vulva from surgical soap contact.

 

*Wilmot Castle Company, Rochester, N.Y.
**Halata1 solution, Jensen-Salsbery Laboratories, Kansas City, Mo.
***John Oster Manufacturing Company, Milwaukee, Wisconsin.

#Liquid Germicidal Detergent, Parke, Davis & Company, Detroit,
Michigan.

22

Figure 2. Surgical instruments used in cruciate ligament prosthesis.
(l)-MayO scissors; (2) Halstead mosquito hemostats, curved; (3) Halstead
mosquito hemostats, straight; (4) Mayo-Heger needle holder; (5) Thumb
forceps; (6) Allis tissue forceps; (7) Backhaus towel forceps; (8), Bard
Parker handle #3 with Bard Parker blade #10; (9) Suturator with type 'A'
nylon; (10) Kirschner pin chuck with key; (11) Steinman stainless steel
pin with trocar point; (12) Cruciate drill guide with Steinman pin; (13)

Hairpin wire; (14) Half circle cutting needle.

23

 

Figure 2

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wafiumoo Houao onu .mfiwonumoue mo woman Amy ”won OHummHQ m OH monoum mHmosumoum A<v .m madman

 

25

Throughout the surgical procedure strict aseptic precautions were
Observed. These included the use Of caps, masks, surgical gowns and
surgeon's hand gloves, and the Operative site adequately covered-with
sterile drapes.

A 4-inch incision was made through the skin extending from the distal
fourth Of the shaft of the femur to below the tibial crest over the
antero-lateral aspect of the femoro-tibial joint (Figure 4). The bleed-
ing vessels were ligated with type "A" nylon. Subcutaneous tissue and
fascia were separated with scissors exposing the joint capsule. Another
incision was made into the joint capsule from above the lateral condyle
of the femur to the tibial crest. The patella was displaced medially
and the leg was flexed so that the stifle joint was thoroughly exposed
(Figure 5). The limb was flexed so that the shafts Of the femur and tibia
formed a 60° angle.

A curved mosquito hemostatic forceps was placed under the anterior
cruciate ligament and slightly pushed upward. Its proximal attachment
was severed taking maximum care not to damage the posterior cruciate liga-
ment. The free end Of the ligament was secured with a pair Of thumb
forceps, and the distal end was also severed at its distal attachment.

For drilling, the curved end Of the drill guide, attached to a
Kirschner pin chuck, was placed in the small depression Of the proximal
attachment Of the anterior cruciate ligament on the medial surface Of
the lateral condyle.with the trocar pointed pin positioned just above the
lateral condyle of the femur (Figure 6). The pin was directed ventro-
medially and a guide hole was drilled through the femur. Following this,
the hole was enlarged with another Steinman pin (Figure 7) with a diameter

large enough to accommodate the prosthesis used as the substitute for the

26
anterior cruciate ligament. A hairpin wire was passed through one end
of the prosthesis and a loop was made out of this wire. Then the pros-
thesis was pulled through the femoral tunnel with the help of the wire
loop (Figure 8).

Next, the point Of the drill guide was located at the anterior inter-
condyloid fossa Of the tibia (the distal attachment Of the anterior cru-
ciate ligament) and the trocar pointed pin was positioned below the
tibial crest antero-medially (Figure 9). A guide hole made through the
tibia was enlarged with a pin, and the other end Of the prosthesis was
passed through it as described above. A 3rd hole was then drilled trans-
versely through the tibial crest and the prosthesis was likewise passed
through it.

The leg was extended and the patella was brought back to its normal
position. The silicone rubber coating of the prosthesis was removed
from both ends to facilitate tying a square knot. With the femoro-tibial
joint simulating the standing position, the prosthesis was drawn taut.
One-half square knot was tied. The stifle joint was examined for anterior
drawer movement by grasping femur with one hand and tibia with the other,
placing one thumb on the posterior aspect Of the distal femur and one
thumb on the posterior aspect of the tibia. The stifle joint was also
tested for easy movement or unusual tightness of the prothesis by moving
the tibia back and forth. When the prosthesis was adjusted so that there
was easy and free normal movement of the joint and an absence Of anterior
drawer movement, it was fixed in place with another square knot reinforced

with Vetafil* to prevent slipping.

 

*Vetafil, Bengen and Company, Hannover, West Germany.

27

After again testing for normal movement of the stifle joint, the
joint capsule was closed with simple interrupted nonabsorbable synthetic
sutures.* Sutures were placed outside the synovial lining Of the joint
capsule to prevent irritation Of the lateral femoral condyle. The sub—
cutaneous tissue was sutured with type "A" nylon.‘ The skin was closed
with "split-thickness" interrupted sutures using type "A" nylon.

Using an elastic gauze bandage, a protective covering was placed
around the stifle joint from the middle of the femur to the middle Of
the tibia. The bandage and adjacent area of skin was then covered with
adhesive tape. Ether was applied to the tape to increase its adhesive-
ness. Recovery from anesthesia was usually in 3 to 4 hours.

After surgery, dogs were kept in their respective cages and-were
maintained on the same diet as prior to surgical Operation. Rectal
temperature was taken with a clinical thermometer every morning for
one month. The bandage covering the stifle joint was Observed regularly
and readjusted if tOO tight or loose. On the 6th postOperative day the
bandage was removed. Skin sutures were removed on the 10th day. Clini-

cal Observations persisted until dogs were euthanatized (TABLE 2).

Hematologic Study
Blood for hematologic examination was collected from the cephalic
vein on the days preceding and following surgery. Subsequent collections
were at an interval of one month. Collections were in a vacutainer-con-
taining EDTA.** The hemogram consisted Of hemoglobin content, packed cell

volume, total and differential leukocyte counts.

 

*Vetafil, Bengen and Company, Hannover, West Germany.

**Tripotassium salt Of Ethylenediaminetetraacetic acid.

28

TABLE 2. Interval between cruciate ligament surgery and euthanasia.

 

—: I
— -;

Serial Case Interval

 

No. NO. Date of Operation IDate Of euthanasia _ _ (wk.)
1 104854 April 29, 1965 August 21, 1965 16
2 104888 May 19, 1965 August 19, 1965 13
3 106626 November 11, 1965 April 25, 1966 24
4 106627 November 29, 1965 April 30, 1966 22
5 106629 November 20, 1965 May 27, 1966 27
6 106630 October 28, 1965 December 1, 1966 57
7 106631 October 19, 1965 April 22, 1966 27
8 106632 November 20, 1965 May 27, 1966 27
9 106634 October 25, 1965 April 30, 1966 27

10 107191 November 30, 1965 August 28, 1966 39

 

29

 

Figure 4. Skin incision over the antero-lateral aspect
of the stifle joint.

30

 

Figure 5. The patella displaced medially to expose the
stifle joint.

31

 

Figure 6. Application Of the drill guide to the femur.
The attachment of the anterior cruciate ligament on the medial
surface of the lateral condyle is usually depicted by a small

depression. The curved end Of the drill guide is located at
this point.

 

Figure 7. The pilot hole made into the femur is being
enlarged to accommodate the prosthesis.

 

Figure 8. The prosthesis passed through the femoral
tunnel.

34

13"., ’ .I'.‘CI'- ‘ . '1 .d‘ .
,1” I 1*“ l"¢‘w;f*‘ ¢ 7| I,

l I
If)"
‘..

 

Figure 9. Application of the drill guide to the tibia.

35

Radiologic Study
Radiographs of both stifle joints in lateral (Figures 10, 11, and 12)
and postero-anterior (Figures 13 and 14) projections were taken after
surgery while the dog was still anesthetized. Follow-up radiographs
(dog anesthetized with a short-acting drug, Thiamylal sodium*) were also

taken once a month.

Post-Mortem Examination.

At varying periods Of time following surgery (3 months to 13 months,
TABLE 2), dogs were euthanatized with pentobarbital sodium solution**
intravenously. A longitudinal incision in the parapatellar area was made
through the skin, fascia and joint capsule. The insertion of the patel-
lar tendon to the tibial tuberosity was severed and the patella reflected
dorsomedially. Both stifle joints (Operated and control) were examined
for gross pathologic changes.

The color and amount Of the synovial fluid was noted. The synovial
’membrane, fibrous part of the joint capsule, and other adjoining liga-
ments were examined for inflammatory changes. The articular surfaces of
the femoral condyles, trochlea and patella were Observed for signs of.
abnormal wear or erosion. The lateral surfaces Of the femoral trochlea
were examined for the development Of the marginal osteophytes. The

lateral and medial menisci were examined for any abnormal wear or splitting.

 

*Surital, Parke, Davis & Company, Detroit, Michigan.

**Toxital, Jensen-Salsbery Laboratories, Kansas City, MO.

36

Specimens of the medial meniscus and the opposing articular cartilage
of the femoral condyle, the regenerated anterior cruciate ligament and
the joint capsule were collected from both stifle joints. All specimens
were fixed immediately in 10% buffered neutral formalin. Sections of
articular cartilage and the adjoining subchondral bone were decalcified*
and washed in running water for 3 hours prior to further tissue processing.

Joint capsule and regenerated anterior cruciate ligament were sec-
tioned at a thickness of 6 microns and stained** as follows: (1) Harris'
hematoxylin and Eosin Y (H & E); (2) the periodic acid-Schiff (PAS)
reaction employing Schiff's leuko-fuchsin solution and counterstained
with Harris' hematoxylin; and (3) May—GrUnwald-Giemsa. Specimens of the
articular cartilage and medial meniscus were cut 6 microns thick and
stained with (1) Harris' hematoxylin and Eosin Y (H & E) and (2) toluidin

blue 0.

Determination Of Breaking Strength of Cruciate Ligaments
Dogs for this part of the study were received from the student sur-
gery laboratory in the Department Of Veterinary Surgery and Medicine.
They were euthanatized with pentobarbital sodium solution administered
intravenously. The breed, sex, body weight and approximate age of each
dog was noted.
A tensile testing instrument*** (Figure 15) was used to determine

the breaking load of the cruciate ligaments. Both the anterior and posterior

 

*Decal, Omega Chemical Company, Garden City, N.Y.

**Armed Forces Institute of Pathology: Manual Of Histologic and
Special Staininngechnics, AFIP, Washington, D.C., 1960.

***Instron, Instron Engineering Corp., Canton, Massachusetts.

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.zuowuom momma maoumfivmafifi ABOH> Howuoucmloumumoev OHMHum uswwa Ono mo nemquHomm .NH ouomflm

 

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.mumeOm Hmumm mawflum Osman ozu wo .3mfl> uoauoucmlouoOmoe .nemqumem .Hmanoae ammo .qa ousmflm

 

42

Figure 15. The tensile testing instrument, "Instron", incorporates
a highly sensitive electronic weighing system employing bonded wire
strain gauges for detecting and recording the tensile load applied to
the sample under test. The chart of the recorder is driven synchronously
at a wide variety of speed ratios and a stress-strain curve is plotted.
By the use of readily interchangeable "load cells", full scale sensi—
tivity may be Obtained extending from 2 Gm. up to 10,000 pounds. The
accuracy is independent of the range in use and is better than‘i.0.5%.*

 

*Operating Instructions for the Instron: Tensile Testing Instru-
ments Manual #10-29—1. Instron Engineering Corporation, Canton, Mass.

If...“ ’ 9’?”

43

 

'.n "J. ‘

' '- '7" Warrant.- I
— ' ' -—"'5"

v:

 

Figure 15

44
cruciate ligaments were tested separately and, in some instances, simule
taneously. Strips of fascia lata, skin, and braided dacron for ligament
prosthesis were also tested in the same manner.

A longitudinal incision was made through the skin, extending from
the trochanter major proximally to the tarsus distally. Using a pair of
scissors for blunt dissection, skin was separated from the subcutaneous
tissue. Soft tissues around the femur, stifle joint, tibia and fibula
were removed. The quadriceps femoris muscle was severed at the musculo-
tendinous junction, leaving the patella with its straight patellar tendon
and joint capsule intact. The tibia, fibula and femur were amputated
through the middle third with an electric saw.- Finally, the fibula was
separated from the lateral tibial condyle. With a power drill, holes
large enough to accommodate a 3/8-inch pin were made transversely through
the proximal and distal ends of the femoral and tibial pieces.

Maximum care was taken so that the stifle joint was not subjected
to any unusual strain during preparation of the bones for the tension
test. The specimen was wrapped with gauze and kept moist with physio-
logical saline solution until used. From One-half to one hour's time
elapsed between the removal Of the Specimen and actual testing of the
breaking strength.

The joint capsule and all the femoro-tibial attachments were divided
except the cruciate ligaments before setting the specimens into the
machine. A steady and constant pull was applied until the ligament

broke (Figure 16).

45

C
Figure 16. The specimen, showing stretched cruciate ligaments
(arrow) under strain while the cross-heads (A) were moving apart.

 

46
For breaking strength Of the anterior cruciate ligament, all the
femoro-tibial attachments were severed except the anterior cruciate liga-
ment. While testing the breaking strength of the posterior cruciate

ligament, it was left intact and other attachments were divided.

Strips.of Fascia Lata
Strips Of fascia lata approximately 1.0 cm. wide and 8.0 cm. long.
were removed from the parapatellar area of several dogs. The test pieces
were kept moistened with physiological saline solution. The elapsed
time between the removal of the test piece and the actual testing of the

material for breaking strength was approximately 30 minutes.

Strips ofgSkin
After clipping the hair closely, skin strips 0.6 cm. wide and.about
8.0 cm. long were Obtained from the lateral surface Of the thigh Of‘
several dogs. The test Specimens were kept moistened with physiological

saline solution.

Braided Dacron
The breaking load Of the braided dacron used as the central cord of
the prosthesis was determined before and after moist heat sterilization
(High-Vac Sterilizer).. Pieces 8.0 cm. long were cut and the ends fastened
to hooks.' Then the hooks were attached to the cross-heads of the machine

and a steady, constant pull was applied until the dacron cord broke.

RESULTS

A postsurgical rise in rectal-temperature of l to 2 degrees was
noted. Normal body temperature values were attained in 2 to 3 days. In
all cases there was first intention healing of the incisional wound. In
2 cases a postOperative swelling around the stifle joint was noticed
which subsided within 10 days. All dogs evinced pain on palpation of
the operated stifle joint during the lst and 2nd week. NO swelling or
tenderness of the joint was noticed in any case after 3 weeks (TABLE 3).
Eight dogs attained complete recovery, and the other 2 showed signs of
lameness after strenuous exercise.

There was no significant change-in hemoglobin values or in packed
cell volume after surgery. However, there was a significant rise in
the total leukocyte count with a shift to the left in all cases. Leuko-
cyte counts returned to normal within 3 to 4 days.‘ Marked lymphocytic
depression was noticed 24 hours after surgery in 8 cases. There was no
significant change in relative or absolute monocyte values. EosinOphils
either disappeared completely from the peripheral circulation or decreased
in number for 2 to 3 days, following which their numbers returned to
normal. During the later period of Observation, no abnormality was

detected in the individual hemograms.

.Ga_1_t.
All dogs walked with a marked lameness during the first postOperative

week. They refused to bear weight on the limb with a prosthesis and held

47

48

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49
it up during walking. By the end of the 4th week all dogs attained a
normal gait (TABLE 4).

Thirty minutes of strenuous exercise, such as running and jumping,
occasionally elicited pain, evidenced by failure to use the limb for as
long as the 4th postsurgical week. In 8 dogs no lameness was detected
after exercise by the end of the 2nd month. Two dogs occasionally limped
after exercise, but there was no detectable lameness or disability when
walking. In neither Of the rear limbs was there disuse atrophy of

muscles in any of the dogs.

Drawer Sign and Range of Movement
Very slight to moderate anterior drawer movement (Figure 17) was
noticed in all dogs. NO posterior drawer sign was detected in any dog,
nor were there any crepitation or clicking sounds in the stifle joint.
There was free movement in the joint, and the leg could be completely
extended. The extent of flexion was also normal.~ The only physical
abnormality detected was a slight to moderate anterior drawer sign Of

the tibia.

Radiggraphic Observations
The outer coating of the dacron prosthesis (silicone rubber), which
was made radiopaque by incorporating barium sulfate, was clearly visible
in radiographs (Figures 18 through 23). During the 2nd month, the pros-
theses were found broken in 3 dogs and by the end of the 4th month, 4

additional dogs had broken their prostheses (TABLE 5).

50

 

 

 

TABLE 4. PostOperative functional recovery evaluated during a slow walk.
Serial Case
No. No. lst week 2nd week 3rd week 4th week
1 104854 lame lame normal gait normal gait.
2 104888 lame lame normal gait normal gait
3 106626 lame normal gait normal gait normal gait
4 106627 lame normal gait normal gait normal gait
5 106629 lame lame lame. normal gait'
6 106630 lame normal gait normal gait normal gait
7 106631 lame lame normal gait normal gait
8 106632' lame normal gait normal gait normal gait
9 106634 lame lame normal gait normal gait
10 107191 lame lame lame normal gait

 

‘
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51

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vocauoa mm .uomuaa mos vuoo

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III III III III sumac“ sumac“ III III III enmqoa H
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53
The prostheses of 2 dogs, 3 and 4 months postOperatively, were found
intact. This observations was confirmed at necrOpsy. The prosthesis of
one dog, case #107191, showed evidence Of fraying at 9 months (Figure 24).
However, at necrOpsy, the central dacron cord was still intact but the

outer covering of the silicone rubber was frayed.

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58

038

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.Azouumv oaHOn mzu canuHB umnnsu mOOOHme mo mmomfie
mo Leequfivmu Hmumumq .omoooae memo .NN madman

 

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Immoe mnucoa m .mawaum unwfiu mLu mo .BmH> uoaumuamIoumumoe .Lemquflwmm .Hmamoae mmmo .qm muomflm

 

61

Gross Pathologic Observations

A thickening of the joint capsule Of the Operated limb was evident
at post-mortem examination. The joint capsule of the control stifle joint
was normal. In 7 cases the joint fluid was clear; in 3 cases it was
cloudy (TABLE 6). The femoro—patellar synovial sac appeared slightly
edematous and ranged in color from brown to reddish brown. Wear or
tear was not seen grossly on the lateral or medial menisci. The articu-
lar surfaces of the femoral condyles were bluish white, smooth and
glistening except for 2 joints which were slightly congested. There was
no evidence Of the development of marginal osteoarthritic pearls along
the edges of the femoral trochlea. The lateral and medial collateral
ligaments were normal and intact.

The prosthesis was found broken in all but 3 dogs (TABLE 6). The
outer covering of the silicone rubber was ripped longitudinally and
transversely and, in a few cases, fragments of it were found inside the
joint (Figure 25). The central dacron cord broke in the middle of the
joint. The broken ends appeared to be either pulled inside the femoral
cu: tibial. tunnels or hanging inside the joint (Figure 26). The knot in
the dacron cord on the lateral side of the joint was completely intact’
and tight'and encapsulated with fibrous tissue. The intact prostheses
were not as taut as when they were originally inserted. The points of
origin and insertion of the anterior cruciate ligament were joined with
.a white, flat fibrous band in 3 cases (Figure 27). This newly formed liga-
ment was not as taut or tough as the original (normal) anterior cruciate
ligament. There was no gross pathologic change in the corresponding

normal stifle joint.

62

 

 

 

 

 

TABLE 6. Gross examination Of the stifle joints with prostheses after
euthanasia.

Serial Case §ynovial fluid

NO. No. Color Amount Joint capsule Prosthesis
1 104854 Clear Scant* Thickened Intact
2 104888 Clear Scant Slightly thickened Intact
3 106626 Yellow 0.5 m1. Slightly thickened Broken
4 106627 Cloudy 0.8 ml. Thickened Broken
5 106629 Clear 0.75 ml. Thickened Broken
6 106630 Clear 0.9 ml. Thickened Broken
7 106631 Clear Scant Thickened Broken
8 106632 Clear 0.5 ml. Thickened Broken
9 106634 Cloudy 0.75 ml. Thickened Broken

10 107191 Clear 0.6 ml. Thickened Intact

* Scant - insufficient amount to measure.

63

uter-covering.of the

Figure 25. Two pieces of silicone rubber (o
-mortem examination.

prosthesis) found inside the stifle joint at post
Case #106630.

Figure 26. One end of the broken dacron cord inside-the stifle
joint noticed at post—mortem examination. Case #106630.

Figure 27. Regenerated anterior cruciate ligament (arrow) noticed
at post-mortem examination. Case #106630. (1) Thickened joint capsule,

(m) patella, (n) femoral trochlea.

 

64

 

 

Figure 25

6
2
e
r
U
00
.1
F

Figure 27

65
HistOpathologic Observations

Articular cartilage: While the articular cartilage appeared to be normal
grossly, there were, in some cases, a microscopic horizontal flaking
(Figures 28 and 29) of its superficial layers (stratum superficialis).
Vertical splitting was also present in a few cases. In such cases,
clusters Of chondrocytes in the stratum radialis and in the stratum
calcificatum were noticed. In one dog (case #106630), there was early
cartilagenous fibrillation with hydropic degeneration of chondrocytes.
Pitting of the stratum superficialis (Figure 30) was also noticed. The
articular cartilages of control stifle joints were comparatively normal,
although some early horizontal flaking and fibrillation (absence of

superficial layer of chondrocytes) were noticed in a few cases.

Medial meniscus. There was vertical splitting of the medial meniscus in
one case (Figure 31). Transverse flaking and folding of superficial
layers were noticed. There was some evidence of clustering of chondro-
cytes near the areas of flaking. The collagen fibers in superficial
layers were arranged parallel to the articular surfaces. In the center
of the meniscus, collagen fiber bundles were interwoven. The menisci of

the control stifle joints were comparatively normal (Figure 32).

Joint capsule. The stratum synoviale was composed of 2 to 3 layers of
cells with small folds at certain places in the control stifle joints
(Figure 33). Synovial cells were pleomorphic, and they varied from round
or spindle shaped to polygonal and epithelioid. Synovial intimal cells
were PAS positive due to the presence of nonsulfated mucOpolysaccharides.
Moderate to strong PAS—positive granules were present in intimal and sub-

intimal'layers.

66

 

 

 

 

Figure 28. Horizontal flaking (arrow) of the articular
cartilage of the femur. Case #107191. Hematoxylin and
eosin. x 375.

 

 

 

Figure 29. Horizontal flaking (arrow) and shredding
(a) of the articular cartilage of the femur. Case #107191.
Hematoxylin and eosin. x 375.

67

 

 

Figure 30. Pitting (arrow) in the stratum superficialis
of articular cartilage of the femur. Case #107191. Hema-
toxylin and eosin. x 375.

 

 

_
—_——— ..-_

Figure 31. Vertical splitting (arrow) in the medial
meniscus. Case #106630. Hematoxylin and eosin. x 375.

68

 

 

 

' (o ' ~. \‘;:4‘
i O ”i ' ' 'o"‘ ‘
\ I '.Q
— u -~
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I o -/.‘ “by/
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’ ' ‘0‘ ~.' ‘0
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Figure 32. Normal medial meniscus. Note the interwoven
collagen fiber bundles. Longitudinal section (1) and trans-
verse section (2) of collagen fiber bundles. Hematoxylin and

eosin. x 375.

 

 

 

 

 

Figure 33. Normal joint capsule. Stratum synoviale
(A) and stratum fibrosum (B). Hematoxylin and eosin. x 375.-

69
In the stifle joints bearing the prosthesis there was minimal to
moderate villus hypertrophy (Figure 34). Large numbers of Langhans'
type giant cells and foreign body giant cells were observed in both inti-
mal and subintimal layers (Figures 35 through 37). The cytoplasm of
giant cells contained fragmented dacron and PAS-positive granules. There
was moderate edema of the stratum fibrosum and the subintimal layer of

the synovial membrane. Plasma cells and a few mast cells were noticed.

Regenerated cruciate ligament. In the regenerated ligaments, collagen
fibers were loosely infiltrated with fibroblasts. Synovial fibroblasts
and synovial fringes were noticed in several places. Numerous synovial
villi had formed around regenerated cruciate ligaments, with a prolifera-
tion of synovial intimal cells and numerous blood vessels at the perimeter
(Figures 38 and 39). Large numbers of Langhans' type giant cells with
phagocytized foreign material (fragmented dacron) were seen primarily

in the superficial layers (Figure 40). These giant cells contained PAS-
positive granules. Plasma cells and mast cells were scattered throughout
regenerated tissue. The cellular structure appeared to be identical with
normal cruciate ligament (Figure 41); however, the cells and fiber bundles
were loosely arranged. The broken dacron cord inside the stifle joint

was infiltrated with fibroblasts and collagen fibers (Figures 42 and 43).

BreakingTStrength of the Combined Anterior and Posterior Cruciate Ligaments
Of the 30 specimens tested for breaking strength of the combined
anterior and posterior cruciate ligaments, 12 separated from the epiphyseal
line of either the femur or tibia without breaking the ligaments (TABLE 7).

When this happened, it was always in dogs under 2 years of age. The

total load to break both the anterior and posterior cruciate ligaments

70

 

 

 

 

_ _— _ _ __ .—

Figure 34. Joint capsule from the stifle joint (case
#106626). Note the edema of the stratum fibrosum and
numerous villi in the stratum synoviale. Hematoxylin and
eosin. x 94.

  
   

 

 

Figure 35. A higher magnification of synovial villi
and fragmented dacron fiber (1) shown in Figure 34. Note
the Langhans' type giant cells (a) and foreign body giant
cells (b). Hematoxylin and eosin. x 375.

 

71

 

 

Figure 36. A higher magnification of synovial membrane
from the stifle joint (case #106631). Note the Langhans'

type giant cell (A) with fragmented dacron (arrow). Hema-
toxylin and eosin. x 1500.

‘

 

 

 

Figure 37. A higher magnification of foreign body type
giant cell (A) in the stratum synoviale (case #106626). Note
the phagocytized fragmented dacron fibers (arrow). Hematoxy-
lin and eosin. x 1500.

 

72

 

.‘ .4. 3“. L “'49:. . V" U a, '
fl, ’ I'J . (é 4‘61“ , . {iv {“dfi .\:";

 

." "I fl
C
' MI I:

' '* \’ U.
_ {A

 

Figure 38. Regenerated anterior cruciate ligament (case
#106630). Note the numerous blood vessels (a), proliferated
synovial intimal cells (b) at the perimeter, phagocytized
dacron fibers (c), and collagen fibers and fibroblasts (d).
Hematoxylin and eosin. x 375.

 

 

 

 

-._.-_.__- .-.__.— _.___ ___

Figure 39. A higher magnificiation of regenerated anterior
cruciate ligament shown in Figure 38. Note the blood vessels
(a). Hematoxylin and eosin. x 1500.

 

 

73

 

 

__

 

- .—.—

Figure 40. Regenerated anterior cruciate ligament (case
#106630). Note the Langhans' type giant cells (a) with phago-
cytized dacron fibers, loosely arranged collagen fibers and
fibroblasts (b). Hematoxylin and eosin. x 375.

 

 

Figure 41. Normal anterior cruciate ligament. Synovial
fibroblasts (A); fibroblasts and collagen fibers (B). Hema-
toxylin and eosin. x 1500.

 

 

 

74

 

Figure 42. Transverse section of the dacron cord from
the stifle joint (case #106630). Note the infiltration of
fibroblasts and collagen fibers in between the dacron fibers
(A). Hematoxylin and eosin. x 375.

.1

1: 1‘
. ’ I". ~ \.r..
‘ Ad 59'. . " 1
‘. . ~, 9“ .z ' ' ‘ I Y"
.. r I... 3.? lg.
,7. 0‘ I v. J l ,
.. . -- I
0).; 4 ‘

V .-
. ,5b.‘ ‘_ ‘“*

Figure 43. A higher magnification of the dacron cord
shown in Figure 42. Note the infiltration of fibroblasts and
collagen fibers (arrow) in between the dacron fibers (A).
Hematoxylin and eosin. x 1500.

’

 

 

 

 

75

 

 

 

 

 

TABLE 7. Breaking load of the combined anterior and posterior cruciate
ligaments.
Breaking load (kg,)
Body Right anterior Left anterior
Serial Age wt. & posterior & posterior
NO. Breed Sex (yr.) (kg.) Cruciate lig. cruciate lig.
1 Mongrel F l 6.8 66.0 81.0
2 Brit. Spaniel F 4 9.5 98.5 98.2
3 Siberian Husky M 0.5 9.5 67.0* 77.0*
4 Beagle M 2 9.0 133.0* 146.0*
5 Beagle M 1.5 11.3 110.0* 110.0*
6 Beagle M 7 11.8 107.0 126.0
7 Mongrel M 1.5 8.0 75.0* 92.0*
8 Cocker Spaniel M 1.5 6.8 63.0* 69.0*
9 MOngrel M 1.5 12.7 91.0* 100.0*
10 Mongrel M 6.5 11.3 111.0 105.0
11 Mongrel M 2.5 9.5 82.0 68.0
12 Mongrel F 7 7.7 99.0 69.-
13 Poodle M 1.5 6.8 80.0 86.0
14 Beagle F 7 11.3 90.0 76.0
15 Ital. Greyhound M 7.5 5.5 87.0 96.0
Average 90.63 93.28

 

*Separated either from the femoral or tibial epiphyseal line
without breaking the cruciate ligaments.

76
together varied from 66.0 kg. to 126.0 kg. In one case, a 146.0 kg. load
was not enough to break both ligaments, but instead they separated from

the tibial epiphyseal line.

Breakigg Strength Of Anterior Cruciate Ligaments
The breaking load varied from 24.5 kg. to 51.0 kg. The breaking
load was remarkably similar for the right and left anterior cruciate liga-
ments from the same dog (TABLE 8). In most cases, the stress train graphs
of anterior cruciate ligaments of right and left stifle joints of the

same dog were superimposable.

Breaking Strength of Posterior Cruciate Ligaments
The breaking load of posterior cruciate.1igaments in different dogs
varied from 24.0 kg. to 51.0 kg. The maximum difference in breaking
load of the ligaments of right and left stifle joints Of the same dog was
4.75 kg. (TABLE 9). Much similarity was found in stress strain graphs of
posterior cruciate ligaments of right and left stifle joints of the same

dog.

Breaking;Loads of Strips of FaSCia Lata, Skin and Braided Dacron

The breaking load of the fascia lata strips (1.0 cm. wide and 8.0 cm.
long) varied from 16.5 kg. to 24.5 kg., with an average of 20.5 kg. The
skin strips (0.6 cm. wide and 8.0 cm. long) broke at loads varying from
25.5 kg. to 31.7 kg., with an average of 28.5 kg. The average breaking
load of the braided dacron was found to be 16.84 kg. A marked decrease
in the breaking load was observed after moist heat sterilization of the

dacron cord (TABLE 10).

77

 

 

 

 

 

TABLE 8. Anterior cruciate ligament breaking loads.
Breaking_loadg(kg.)
Body Right anterior Left anterior
Serial Age wt. cruciate cruciate
NO. Breed Sex (yr.) (kg.) ligament ligament
l Mongrel F 1 8.2 35.50 38.00
2 Mongrel M 4 7.7 33.50 26.75
3 Mongrel M 2 7.3 43.00 39.75
4 Mongrel M 1.5 10.0 47.75 51.00
5 Cocker Spaniel M 2 10.9 24.50 24.50
6 Mongrel M 6 9.5 40.75 44.75
7 Mongrel F 9 mo. 6.0 24.75 27.50
Average 35.68 35.96

 

78

 

 

 

 

 

TABLE 9. Posterior cruciate ligament breaking loads.
Breaking load (kgL)
Body Right pos- Left pos-
Serial Age wt. terior cru- terior cru—
NO. Breed Sex (yr.) (kg.) ciate lig. ciate lig.
1 Mongrel M 2 8.2 24.00 24.50
2 Schnauzer F 2 7.7 31.50 36.25
3 Mongrel M 2 8.2 51.00 48.00
4 Cocker Spaniel M 3 11.4 27.75 27.50
5 Cocker Spaniel M 9 14.5 34.25 35.00
6 Cocker Spaniel F 2 11.4 47.25 46.00
7 Mongrel F 1.5 8.2 35.50 32.25
Average 35.90 35.64

 

79

TABLE 10. Breaking load of braided dacron.

 

 

Breaking load (kg.) Breaking load (kg.)

 

 

Test NO. before sterilization after sterilization
l 16.40 11.60
2 16.30 14.30
3 15.90 15.50
4 17.90 13.90
5 17.70 15.30
Average 16.84 14.12

 

DISCUSSION

The main Objectives in repair Of anterior cruciate ligaments are to
eliminate the anterior drawer movement and to stabilize the stifle joint.
Anterior sliding movement Of the tibia during ambulation causes micro-
trauma to the articulating cartilage Of the femur and menisci, which are
the chief articulating weight bearing surfaces. Continuous microtrauma,
during a period of time, is responsible for the pathologic changes result—
ing in osteoarthritis of the stifle joint.

In this experimental study of the replacement of the anterior cruciate
ligament, braided dacron coated with silicone rubber was used as the
prosthetic material. The coating of simple silicone rubber is not physi-
cally modified by soft tissue and is chemically inert (Braley, 1965).

It does not cause any inflammatory or foreign body tissue reaction and
can be sterilized. It can be molded to the apprOpriate size and shape of
a tendon or ligament. Furthermore, it seems to possess a physiologic
bounce that complements soft tissue during motion (Hunter, 1965). This
material has many desirable characteristics. However, it does lack
strength and is susceptible to tearing.

The idea Of coating the dacron cord with silicone rubber was to pro-
tect the central piece from coming in contact with the joint fluid. In
this way the integrity and strength of the dacron cord should be main-
tained with only minimal foreign body tissue reaction in the stifle

joint.

80

81

Due to constant mechanical pressure on the prosthesis and the normal:
back-and-forth movement Of the stifle joint, the silicone rubber broke
at several places, permitting the dacron cord to come in direct contact
with the joint fluid. The combined effects of the joint fluid, body
temperature and mechanical wear after tearing of the silicone rubber might
be the contributory factors in fragmentation of the dacron cord.

Two months following surgery, 8 of the 10 dogs had a normal gait
and 2 dogs occasionally favored their legs after strenuous exercise.

No functional disability was observed, even after the prosthesis broke.
Of the 10 prostheses, 7 were found broken after a period varying from 2
to 4 months. Very slight to moderate anterior drawer movement of the
tibia could be produced when the dogs were anesthetized.

At post-mortem examination, there was no evidence Of osteoarthritis
in the stifle joint. But foreign body tissue reaction was clearly Ob-
served on histopathologic examination. There was also some wear and
tear of articular cartilages and of the menisci of the stifle joint which
could be seen microscopically. Probably the foreign body tissue reaction
was due to the dacron fibers. The microscopic wear and tear was due to
constant microtrauma caused by anterior drawer movement Of the tibia.

In this study, the functional recovery, anterior drawer sign, reduc—
tion in the breaking strength and fraying of.the prostheses, microscopic
wear and tear in the articular cartilages and menisci, chronic foreign
body inflammatory changes, and the thickening of the joint capsule of the
stifle joints appeared to support the results of Harrison and Adler (1956),
Rathor (1959), Emery and Rostrup (1960), Leighton (1961), Vaughan (1963),

Butler (1964), Ryan and Drompp (1966), Strande (l966a,b) and Childers (1966).

82

It was interesting to note that there was regeneration of the anterior
cruciate ligament in 3 cases. On histopathologic examination the regenera-
ted structure was found tO be similar to the normal anterior cruciate
ligament. However, there was some chronic inflammatory reaction, as
evidenced by the presence of giant and plasma cells. Bassett and Carroll
(1963), Ashley (1963) and Hunter (1965) reported similar results. They
reported formation of a new sheath around a substitute tendon made Of
polyester fiber and silicone rubber. During surgical repair Of the
ruptured anterior cruciate ligament, partially or completely broken
stumps should not be removed, as there is a possibility of ligament re-
generation and reunion.

The average breaking strength of the combined anterior and posterior
cruciate ligaments was found to be 91.9 kg., whereas breaking loads of
anterior and posterior cruciate ligaments separately were 35.8 kg. and
35.7 kg., respectively. Breaking strengths of strips of fascia lata
(1.0 cm. wide) and skin (0.6 cm. wide) were 20.5 kg. and 28.5 kg.,
respectively. These are the usual widths of fascia lata and skin strips
used for anterior cruciate ligament substitutes in dogs weighing approxi-
mately 10.0 kg., even though their breaking strengths are considerably
less than that of anterior cruciate ligament. The dacron cord used in
this experiment had a breaking strength less than that of fascia or skin
strips and approximately only one-half of that of the original anterior

cruciate ligament.

SUMMARY

A study of the replacement of anterior cruciate ligaments with
synthetic material (braided dacron coated with silicone rubber) was
performed on 10 dogs. Breaking strength Of the cruciate ligaments,
fascia, skin and braided dacron was also determined.

PreOperative procedures consisted of standard routines preparatory
to the use Of sterile techniques. After making a skin incision in the
parapatellar area, the stifle joint was exposed. The prosthesis was
passed through Oblique tunnels made in the femur and tibia. Finally,
it was passed through a 3rd hole made below the tibial crest and the 2
ends were tied on the lateral side of the joint.

Dogs were kept under observation for variable periods of time, rang-
ing from 3 to 13 months. Postoperative recovery was uneventful. Some
of the dogs started using their legs as early as 2 weeks after surgery.
PostOperative functional recovery was evaluated during a slow walk. All
dogs attained normal gait after 4 weeks. After strenuous exercise, 2
dogs occasionally favored the leg with a prosthesis. Very slight to
moderate anterior drawer movement could be produced in all cases when
examined during anesthetization. Of 10 prostheses, 7 broke after 2 to
4 months. Broken prostheses were visible in radiographs.

Post—mortem examinations of joints bearing prostheses did not reveal
osteoarthritic changes. Some wear and tear of the articular surfaces of
the femu; and the menisci was evident on histopathologic examination.

Chronic inflammatory changes with foreign body tissue reaction were

83

84
Observed in the joint capsule. In 3 cases, the anterior cruciate liga-
ment regenerated.

A tensile testing instrument, "Instron", was used to determine the
breaking strength of normal cruciate ligaments. Both the anterior and
posterior cruciate ligaments were tested separately and, in some cases,
simultaneously. Breaking strength of fascia lata, skin and braided dacron

were also tested in the same manner.

CONCLUSIONS

After reviewing all available literature concerning repair of the
anterior cruciate ligaments, it appears that all authors claim superiority
for their individual techniques. Every claim for superiority is based
upon experiments conducted on dogs. There is, however, agreement that
the main objective is to stabilize the stifle joint.

In this experiment, the prosthesis broke and a slight to moderate
anterior drawer movement was present. Even regenerated anterior cruciate
ligaments were not as taut as the original ones. Nevertheless, the dogs
were able to walk or run without functional disability. NO disuse atrophy
of the muscles was evident in any case.

It is concluded that dacron cord coated with silicone rubber when used
as a substitute for the anterior cruciate ligament, did give temporary'
stability to the stifle joint. It appears that during this period Of sta-
bility there is a compensatory strengthening and thickening Of the joint
capsule, thus permitting functional recovery Of the affeCted limb. There
may be, however, some anterior drawer movement of the tibia following
attainment Of functional recovery. The dacron used as a prosthetic an—
terior cruciate ligament does cause chronic inflammatory changes in the
joint capsule. When a prosthesis is used as a substitute for a removed
anterior cruciate ligament, there is a possibility of its regeneration.
The prosthesis made of dacron covered with silicone rubber is unsatisfactory
due to loosening of the coating and rupture of the dacron, even though the
prosthesis may appear to function in a satisfactory manner initially.

85

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