A Study of Articular Surfaces and Synovial Fossae of the Pectoral Limb of Swine C. Doige and A. Horowitz*
ABSTRACT
INTRODUCTION
Articular surfaces of the pectoral limb were studied in 50 swine and are described in detail. Synovial fossae were not present at birth but were found commonly on the articular surface of the scapula, distal humerus, proximal radius, distal radius and distal surface of the intermediate carpal bone after four to five months of age. When present, they were bilaterally symmetrical and were located at the depth of a concavity of the articular surface. Microscopically, synovial fossae appeared as an invagination of articular cartilage extending into subchondral bone. Evidence of endochondral bone formation was less apparent at the depth of synovial fossae than in areas of weight bearing cartilage.
Familiarity with the normal gross and histological appearance of articular structures is a basic necessity if one is to recognize and evaluate pathological changes. This study was undertaken in an attempt to establish the normal gross appearance of articular surfaces of the pectoral limb of swine. Special attention was directed to synovial fossae (nonarticulating depressions), their size, histological appearance and presence or absence in various age groups. Joint capsule attachments and contours of articular surfaces were also studied. Descriptions of synovial fossae or nonarticulating depressions on articular surfaces of ungulates exist in the literature (5,8,10,11). In most cases they are regarded as normal structures. Their importance lies in distinguishing them from pathological changes in articular cartilage. Communication between carpal joints and sites of attachment of joint capsules anci ligaments of the pectoral limb of swine have been described (7,12).
RESUME Les auteurs ont etudie les surfaces articulaires du membre pectoral, chez 50 pores, et ils en donnent une description detaillee. Les fosses synoviales n'etaient pas encore presentes chez les nouveau-nes, tandis que, chez les sujets ages de quatre a cinq mois, on les retrouvait regulierement sur la surface articulaire de l'omoplate, de l'humerus distal, du radius proximal et distal, ainsi que sur la surface distale de l'os interm6diaire du carpe. Une fois developpees, elles etaient bilat6rales et symetriques, et se situaient au fond d'une concavite de la surface articulaire. Leur aspect microscopique se traduisait par une invagination du cartilage articulaire se prolongeant dans l'os sous-chondral. L'ossification endochondrale s 'avera moins apparente au fond des fosses synoviales qu'aux endroits oiu le cartilage supporte le poids de l'animal. *Department of Veterinary Pathology, Western College of Veterinary Medicine, Saskatoon, Canada. Present address of A. Horowitz: Department of Veterinary Anatomy, College of Veterinary Medicine, Columbus, Ohio. Submitted April 3, 1974.
Vol. 39 -January, 1975
MATERIALS AND METHODS Joints of the pectoral limb of 50 swine were studied. Shoulder, elbow, antebrachiocarpal, intercarpal and carpometacarpal joints were examined in each case. The majority of limbs examined was from market weight swine (five to eight months of age). Limbs from other age groups ranging from two weeks to three years were examined as well. Limbs were recovered from a local abattoir or from a diagnostic laboratory. In the latter case death was due to a variety of causes. Many of the limbs examined were from animals whose health and nutritional status were unknown. Not all joints examined were considered to be normal. Lesions of inflammatory, degenerative and nutritional origin were observed. These were discarded from the sample.
7
Portions of bone and cartilage for histological examination were fixed in 10% neutral buffered formalin and later decalcified in 20% formic acid. Sections were cut at 6t± and stained with hematoxylineosin.
Fig. 1. Articular surface of distal right scapula. Pig six months of age. There is a centrally located synovial fossa present (arrow).
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older animals. A ring of fibrocartilage surrounded the articular cartilage and added to the depth of the concavity. This was comparable to the labrum glenoidale in man and was most prominent caudally. In the newborn animal the articular surface was concave, smooth and uninterrupted. A central, cartilage lined synovial fossa (Fig. 1) became evident in most swine between four and six months of age. Its shape and time of appearance varied. It was most often stellate and became linear or S-shaped in older animals. In most cases it was deep and prominent at six to eight months of age.
Proximal humerus (Fig. 2) - The joint capsule attached at the edges of the articular cartilage except at the caudal margin where it sometimes attached slightly below the margin of articular cartilage. It sheathed the biceps tendon as it passed through the intertuberal groove. The biceps tendon was supported proximally by a thin mesotendon. The articular surface was smooth, convex and almost spherical in outline. This spherical outline was most perfect at birth but irregularities appeared and increased with age. Articular cartilage extended cranially beyond the main convex surface onto the greater and lesser tubercles (Fig. 2). This
RESULTS GROSS FINDINGS
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SHOULDER JOINT
Distal scapZula (Fig. 1) - The joint capsule was inserted at the edge of the articular cartilage on all aspects of the joint except in the caudomedial area where it was inserted slightly proximal to the margin of the articular cartilage. At the craniolateral border it was reinforced by the attachment of two elastic bands. The joint capsule tended to bulge into the joint cavity on its lateral border. The articular outline was almost circular in the newborn, was roughly oval at five to six months of age and more irregular in older sows and boars. In newborn animals the line of union of the supraglenoid tubercle to the body of the scapula was visible. The articular surface was slightly flattened at the periphery in the lateral and craniomedial areas. This was most prominent in
8
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1
2
3
4
5
Fig. 2. Articular surface of proximal right humerus. Pig- six months of age. Articular outline is spherical. Cartilage in cranial area (A) is thin.
Can. J. comp. Med.
extension was lacking in some animals. The margin of the articular cartilage in this area was smooth and regular or irregular. In many animals two or three strands of connective tissue passed proximally from the cranial articular margin to the neighbouring synovial membrane. The articular cartilage extended cranially and distally to form the floor and walls of the intertuberal groove. In a six month old pig this groove was 2.0 - 2.5 cm in length. Tiny vascular canals penetrated the margins of the articular cartilage in the cranial, caudomedial and caudolateral areas. At five to six months of age thin areas of cartilage with a distinct blue appearance (2.0 - 2.5 cm in diameter) were often present on the cranial portion of the humeral head. In animals two to three years of age this area of cartilage remained very thin and the surface was often irregular.
ELBOW JOINT
Distal humerns (Fig. 3) - The joint capsule attached at or very close to the margins of the articular cartilage at the cranial and caudal borders. The medial and lateral portions were inserted on the medial and lateral epitrochlear surface at the edge of the articular cartilage. Articular cartilage extended onto the medial and lateral surfaces of the trochlea.
It also extended cranially to the margins of the coronoid and radial fossae and caudally to the edge of the olecranon fossa. Tiny vascular canals penetrated the medial and lateral surfaces of the trochlea. The articular surface formed a trochlea with a sagittal central groove. A narrow, deep, linear, nonarticulating depression often developed at the deepest part of this groove at four to five months of age (Fig. 3). It was absent in newborn animals and somewhat indistinct and variable in older animals (three years). It arose at the cranial margin of the articular surface and followed the depth of the central groove for one half to three quarters of the circumference of the trochlea. The medial half of the trochlea was smooth. The lateral part was divided by a low, broad, sagittal ridge. The resulting grooves and ridges were rather sharp at five to six months of age but were less prominent and well rounded at birth. Slight irregularities of the articular cartilage on the lateral part of the trochlea were commonly present in adult animals. Thin areas of cartilage (blue areas) were frequently observed caudally on the lateral part of the trochlea.
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Fig. 4. Articular surface of proximal right radius and ulna. Pig - six months of age. There is a deep synovial fossa on the surface of the proximal radius (arrow).
S
.
Fig. 3. Articular surface of distal right humerus. Pig months of age. Trochlear surface is divided by (arrow).
- six
a deep linear groove
Vol. 39 -January, 1975
Proximal radius and ulna (Fig. 4) - The joint capsule attached at or slightly distal to the margins of the articular cartilage of the proximal radius in the medial, lateral
9
and cranial region. It attached somewhat beyond the edge of the articular cartilage of the ulna on the proximal, medial and lateral aspect of the trochlear notch. Here the articular cartilage extended well beyond the weightbearing articular surface, especially on the medial border. On the medial surface of the trochlear notch the joint capsule formed a pouch which underlay the deep digital flexor. Tiny vascular canals penetrated the cranial border of the articular cartilage of the radius. The articular surface of the proximal radius consisted of two main facets divided in the sagittal plane by a low ridge. The medial facet was smooth and slightly concave. The lateral facet was subdivided into two areas by a blunt sagittal ridge. Immediately medial to this ridge was a narrow concave facet which contained a deep, distinct, nonarticulating depression (Fig. 4). This fossa became evident at three to five months of age and persisted. Most older animals (two to three years) had deep well defined fossae at this site. Others had only a narrow linear depression. Lateral to this area was a smooth facet that was slightly concave from side to side. The curvature of these facets appeared greatest in the young and the surfaces appeared more flattened in aged sows. These facets articulate with the trochlea of the distal humerus. The articular surface of the proximal ulna consisted of the trochlear notch and the lateral facet. At the age of six months the distal one third of the articular surface of the notch was incompletely (sometimes completely) separated from the proximal two thirds by a narrow transverse line. A nonarticulating area was present immediately lateral to the distal one third of the trochlear notch. The lateral articular facet of the ulna (1.0 cm x 1.0 cm in size at six months of age) was lateral to the above nonarticulating area. In very young animals and in mature sows the articular surface of the proximal ulna was relatively more extensive and the nonarticulating area was reduced in size. ANTEBRACHIOCARPAL JOINT Distal radius and ulna (Fig. 5) - The joint capsule was inserted at the edge of the articular cartilage which extended well beyond the main weight bearing surface on the dorsal surface of the distal radius and
10
Fig. 5. Articular surface of distal right radius and ulna. Pig - six months of age. There is a linear depression (synovial fossa) on the articular surface of the distal radius (arrow).
ulna and to a lesser degree on the medial surface of the distal radius and lateral surface of the distal ulna. The articular surface of the distal radius and ulna was continuous. It consisted of three main facets. The lateral facet was deeply concave from side to side and convex in the craniocaudal direction. It was narrow craniocaudally and consisted of the articular surface of the distal ulna and a neighbouring part of the distal radius. This facet articulated with the accessory carpal bone and the ulnar carpal bone. The two remaining facets (central and medial facets) constituted the main articular surface of the distal radius. Both of these facets were concavoconvex with the concavity being cranial. A narrow, often branching linear depression that was nonarticulating was present in the dorsal concave portion of the medial facet (Fig. 5). It often extended into the concavity of the central facet. It was not present at birth but was present in most swine at five months of age. It was prominent at five to six months of age and sometimes indistinct and sometimes circular and very distinct in sows (two to three years). Two main ridges separated the three main articular facets. These passed obliquely across the joint in a craniolateral direction. As a result, when the carpus is flexed the portion of the limb distal to the carpus moves slightly medial-
Can. J. comp. Med.
ly. The two medial facets articulate with the radial carpal and intermediate carpal bones. Proximnal articutlar surface of the proximal row of carpa-l bones (Fig. 6) - The joint capsule attached at the margin of the articular cartilage which extended beyond the weightbearing articular surface on the entire dorsal aspect, on the palmar aspect of the ulnar, intermediate and radial carpal bones and on the medial surface of the radial carpal bone. The articular surface was formed by the proximal surface of the accessory carpal, ulnar carpal, intermediate carpal and radial carpal bones. A small facet on the dorsoproximal surface of the accessory carpal bone articulated with the palmar surface of the distal ulna. The proximal surface of the ulnar carpal bone was irregular (Fig. 6). It was concave from dorsal to palmar and convex mediolaterally. There was a high ridge on its dorsal and palmar ex-
slightly convex dorsally and concave in the palmar region. The proximal articular surface of the radial carpal bone was similar. The concavity and convexity were more pronounced. These two bones (intermediate and radial carpal) articulated with the corresponding concavoconvex facets of the distal radius. Nonarticulating fossae were not evident on these surfaces in any age group. Tiny linear depressions were occasionally present on the ulnar carpal bone. Ligaments securing the carpal bones appeared to be loosely attached in very young animals.
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Fig. 7. Distal articular surface of proximal row of carpal bones, right pectoral limb. Pig - six months of age. A synovial fossa is present (arrow) on the surface of the accessory carpal bone.
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Fig. 6. Proximal articular surface of the proximal row of carpal bones, right pectoral limb. Pig - six months of age.
tremities. The main concavity articulated with the distal ulna. A narrow flat articular surface on its medial boundary articulated with a similar facet on the lateral surface of the distal radius. The proximal articular surface of the intermediate carpal bone was elongated from dorsal to palmar. It was
Vol. 39 -January, 1975
INTERCARPAL JOINT Distal articular surface of the proximal row of carpal bones (Fig. 7) - The joint capsule attached at the margin of the articular cartilage which extended slightly beyond the weight bearing surface except in the palmar region. The ulnar, intermediate and radial carpal bones contribute to the articular surface. The distal articular surface of the ulnar carpal bone consisted mainly of an
elongated, slightly convex (mediolateral) facet which was concave in the sagittal plane. It articulated with the fourth carpal bone. There was also a small, slightly con-
11
vex facet on its palmar extremity that articulated with the palmar extremity of the fourth carpal bone. The articular surface of the intermediate carpal bone was extensive and irregular. There were two main articular facets, medial and lateral. These two facets were separated by a ridge passing in a dorsopalmar direction. Both facets were concave in the sagittal plane and articulated with convex facets of the proximal surface of the third and fourth carpal bones. There were two small additional facets. One was located dorsomedially and articulated with a dorsal facet on the proximal surface of C3. The smaller lateral and palmar facet articulated with a similar facet on the palmar aspect of the proximal surface of C4. A nonarticulating area, about 3 mm in diameter, was present in the central ridge mentioned above (Fig. 7). This fossa was not present at birth but was commonly present in animals four to five months of age or older. The fossa was usually deep and distinct. Its position and size were the least variable of the synovial fossae observed on the articular surfaces of the joints of the pectoral limb. The distal articular surface of the radial carpal bone was usually divided into medial and lateral facets. Both facets were continuous and were not sharply divided. The lateral facet was concavoconvex with the convexity dorsal. It articulated with a convexoconcave facet of C3. The medial facet was smaller, only slightly concave and occupied the medial palmar aspect of the joint surface. It articulated with the convex surface of C2. In some swine, tiny branching linear depressions were present in the depth of the concavity of the medial facet.
Proximal articular surfacae of the distal row of the carpal bones (Cl, C2, C3 and C4) (Fig. 8) - The joint capsule attached at the margins of the articular cartilages which extended slightly beyond the main weight bearing surface in the dorsal, medial and lateral areas. Synovial fluid can flow freely from the intercarpal to the carpometacarpal joint between the dorsally opposed surfaces of C3 and C4. Cl did not always contribute to the surface of this joint. In most animals, there was a tiny facet on the proximal surface of Cl. It articulated with the palmar extremity of the radial carpal bone (distal surface). The articular surface of C2 was triangular and relatively small and convex. It articulated with the medial facet
12
of the radial carpal bone. The surface of the C3 was large and was divided into two main facets (Fig. 8). The medial facet was triangular with the base dorsal. It was concave mediolaterally and concavoconvex in the sagittal plane with the concavity dorsal. This concavity sometimes had fine linear depressions. It articulated with the larger of the two facets of the radiocarpal bone. A sagittal ridge passing from dorsal to palmar separated this facet from the lateral facet. The dorsal area of the lateral facet was concave and continuous with the palmar portion which was convex. The dorsal, concave area occasionally had tiny linear nonarticulating depressions. The proximal articular surface of the C4 was the largest of the three carpal bones. Its surface was made up of medial and lateral facets separated by a sagittal ridge. The medial facet was smooth and convex in the sagittal plane and often revealed a narrow palmar facet. It articulated with the intermediate carpal bone. The lateral facet was concave in the dorsal and palmar region. The two facets were separated by a central convex area which articulated with the ulnar carpal bone. Tiny linear depressions or infoldings of articular cartilage were seen occasionally in the palmar facet.
Fig. 8. Proximal articular surface of distal row of carpal bones, right pectoral limb. Pig - six months of age.
Can. J. comp. Med.
concave in the sagittal plane and received the convex surface of Mc4. Small oblique facets were present on the dorsomedial and palmarlateral extremities of this bone. These were both slightly concave and articulated with the dorsal and palmar extremities of Mc3 and Mc5 respectively. A small triangular dorsal facet was present also. It was slightly convex and articulated with the dorsal concavity of Mc4. Small linear depressions in the cartilage of the main concavity of C4 were observed in some animals two to three years of age.
Fig. 9. Distal articular surface of distal row of carpal bones, right pectoral limb. Pig - six months of age.
CARPOMETACARPAL JOINT Distal articular siurface of the distal rowv of carpal bones (C2, C3 and C4) (Fig. 9) The jolint capsule attached to the margins of the articular cartilage which extended slightly beyond the main weightbearing surface, especially on the dorsal surface of the joint. Cl had no distal articular surface. The distal articular surface of C2 was divided into two small facets. The palmar facet was elongated, slightly concave and articulated with the proximal surfa-ce of Mc2. The dorsal facet faced obliquely dorsolaterally and distally and articulated with the medial oblique facet of Mc3 (Fig. 9). The articular surface of C3 was extensive and consisted of two main facets, a larger dorsal facet and a smaller facet on the palmar lateral extremity. The dorsal facet was smooth and concave (dorsopalmar). It articulated with the smooth convex surface of Mc3. The palmar facet was small, flat and faced obliquely in a lateral and distal direction. It articulated with a small facet on the palmar surface of Mc3. Some animals had small depressions or nonarticulating areas in the depth of the concavity of C3. The articular surface of C4 consisted of four articular facets. The main facet was deeply
Vol. 39-January, 1975
Proximal articular surface of metacarpal bones (Mc 2, 3, 4 and 5) (Fig. 10) - The joint capsule attached at the margins of the articular cartilage which extended slightly beyond the main articular surface in the entire dorsal area and in the palmar aspect of Mc5. Metacarpal bones 2, 3, 4 and 5 contributed to the joint surface (Fig. 10). The proximal articular surface of Mc2 was divided into two tiny facets. The medial facet was almost circular, slightly convex and articulated with the palmar concavity of C2. The lateral facet was smaller and oblique. It faced proximolaterally and articulated with the palmar medial extremity of C3. The proximal articular surface of Mc3 was extensive. The central facet was the largest. It was convex from dorsal to palmar and concave from side to side. It articulated with the distal surface of C3.
CM
1
2
3
4:
Fig. 10. Proximal articular surface of metacarpal bones, right pectoral limb. Pig - two years of age.
13
A small flat facet on its medial extremity faced proximomedially and articulated with the dorsal portion of the distal surface of C2. A similar small facet in the palmar region faced obliquely proximomedially and articulated with the palmar extremity of C3 (distal surface). A third small facet was present on the lateral and dorsal aspect of the third metacarpal bone (proximal surface). It was almost flat and articulated with the dorsal medial extremity of the distal surface of C4. The proximal articular surface of Mc4 was concavoconvex with the concavity dorsal. Tiny linear depressions were present in the dorsal concavity and near the palmar border in some adult animals. Mc4 articulated with the coneavoconvex surface of C4. The articular surface of Mc5 faced obliquely proximally and medially. It was small and slightly concavoconvex (or convex only) with the concavity dorsally. It articulated with the oblique facet on the palmar lateral surface of C4. MICROSCOPIC FINDINGS
Histologically, synovial fossae were represented as an invagination or infolding of articular cartilage (Figs. 11 and 12). The depth and width were variable. In animals six months of age the entire surface was covered with cartilage, in older animals fossae present on the proximal radius and the proximal surface of the intermediate carpal bone sometimes lacked a cartilaginous covering at the depth of the depression. The thickness of cartilage
Fig. 12. Histological appearance of synovial fossa on the articular surface of the proximal radius. Pic six months of age. H & E. X15.
lining synovial fossae was variable but was often less than the thickness of articular cartilage on weightbearing surfaces. There was no evidence of collapse of underlying bone (e.g. fractured trabeculae, fibrosis, etc.). Evidence of endochondral bone formation (aligned, proliferating, hypertrophic, chondrocytes) was less apparent in the depth of synovial fossae than in areas of articular cartilage on the weight bearing surface.
DISCUSSION
Fig. 11. Histological appearance of linear groove which divides the trochlear surface of the distal humerus. Pig - six months of age. H & E. X10.
14
Artictular cartilage on the weightbearing surfaces of synovial joints is the final recipient of mechanical forces acting on the skeleton. It is elastic to intermittent pressure due to exudation and resorption of fluid (1). In the immature animal two areas of growth exist, the upper midzonal area is responsible for maintaining the thickness of articular cartilage whereas the deep zone provides for growth of the epiphysis (1). Although normal articular cartilage grows throughout life it does so with less vigor in old age (6). Regeneration is limited if injuries are confined to articular cartilage. Injuries which extend into subchondral bone are repaired by fi-
Can. J. comp. Med.
!1 _> ~ ~ ~ ~(1, 6, 9).
ness of articular cartilage whereas prolonged continuous compression results in degenerative changes or pressure necrosis
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Synovial fossae were absent in all cases birth but were present in a high percentage of swine at 90 kg body weight. They were bilaterally symmetrical. Most were located at the depth of an articular concavity. The time of appearance, size, "-i shape and persistence of any given fossa varied considerably. The absence of syno- ~vial fossae -at birth suggested that they are llot remnants of embryological processes. It is possible that they develop in the normal process of bone and cartilage formation due *:._.:to a lack of or a reduction of weight bearing stimuli in these areas. Differences in rate of growth and nutritional status of the animal as well as differences in physical stresses acting on any given joint surface may account for variation observed in size, shape and time of appearance of synovial
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Fig. 13. Humeral head of pig (five months of age)
w ith multiple, linear areas of articular collapse secondary to nutritional osteodystrophy.
brous tissue or fibrocartilage (1). In the present study considerable variation in contours of articular surfaces was observed among randomly selected swine. This is consistent with reports by other workers (1, 3) who observed that although articular surfaces develop according to an inherited pattern they may be altered by physical stresses. Variations in thickness of articular cartilage observed between individual animals and within a single joint may be the result of different rates of attrition and cartilage formation. It has been established that functional stimuli facilitate growth of articular cartilage (1) and that the apposition of articular surfaces is important in the maintenance of normal articular cartilage (2). Since articular cartilage is avascular (9) and receives its nutrition
fossae. It is important to distinguish synovial fossae from areas of articular collapse due
.
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intercellular substance (1, 4, 9), intermittent compression associated with normal movement and weightbearing is important in the maintenance of normal articular cartilage (3). Vigorously exercised cartilage has been shown to be thicker than
unusued cartilage. Excessive, intermittent
*. compression may result in increased thlckin
increased
Vol. 39 -January, 1975
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.,
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Fig. 14. Microscopic appearance of areas of articular in Fig. 13. Note the disruption of subcollapse chondral shown bone. H & E. X15.
is
to weakness of underlying bone (Figs. 13 and 14). Synovial fossae may be distinguished by anatomical site and histological appearance. REFERENCES 1. BAUER, W., M. W. ROPES and H. WAINE. The physiology of articular str-uctures. Physiol. Rev. 20: 272-312. 1940. 2. BENNETT, G. A., W. BAUER and S. J. MADDOCK. A study of repair of articular cartilage and the reaction of normal joints of adult dogs to surgically created defects of articular cartilage, "joint mice" and patellar displacement. Am. J. Path. 8: 499-524. 1932. 3. BOLLET, A. J. An essay on the biology of osteoarthritis. Arthritis Rheum. 12: 152-163. 1969. 4. BROWER, T. D. and WAN-YI HSU. Normal articular cartilage. Clin. Orthop. and Related Res. 64: 9-17. 1969.
16
5. COHRS, P. and G. MESSOW. Musculoskeletal system. In Joest's Handbook of the Special Pathological Anatomy of Domestic Animals. Edited by J. Dobberstein, G. Pallaske and H. Stiinzi. 3rd Ed. Vol. 1. p. 221. Berlin and Hamburg: Verlag Paul Parey. 1969. 6. JOHNSON, L. C. Kinetics of osteoarthritis. Lab. Invest. 8: 1223-1241. 1959. 7. KOSTYRA, J. Joints of the extremeties of the pig. Part I. The foreleg. Annals Univ. Mariae CurieSklodowska 14: 240-265. 1959. 8. NICKEL, R., A. SCHUMMER and E. SEIFERLE. Lehrbuch der Anatomie der Haustiere. Vol. I. p. 178. Berlin and Ham-burg: Paul Parey. 1961. 9. SALTER, R. B. and P. FIELD. The effects of continuous compression on living articular cartilage. J. Bone Jt Surg. 42A: 31-49. 1960. 10. SCHWARZE, E. and L. SCHRODER. Kompendium der Veterinar-Anatomie. Vol. 1. p. 127. Jena: Veb Gustav Fischer Verlag. 1960. 11. SISSON, S. and J. D. GROSSMAN. The Anatomy of the Domestic Animals. 4th Edition. p. 210. Philadelphia and London: W. B. Saunders Co. 1953. 12. WISSDORF, H. and K. NEURAND. Das Karpalgelenk des Schweines-Grundlagen fur die Gelenkinjektion. Dt. tierarztl. Wschr. 73: 396-404. 1966.
Can. J. comp. Med.
ABSTRACT
INTRODUCTION
Articular surfaces of the pectoral limb were studied in 50 swine and are described in detail. Synovial fossae were not present at birth but were found commonly on the articular surface of the scapula, distal humerus, proximal radius, distal radius and distal surface of the intermediate carpal bone after four to five months of age. When present, they were bilaterally symmetrical and were located at the depth of a concavity of the articular surface. Microscopically, synovial fossae appeared as an invagination of articular cartilage extending into subchondral bone. Evidence of endochondral bone formation was less apparent at the depth of synovial fossae than in areas of weight bearing cartilage.
Familiarity with the normal gross and histological appearance of articular structures is a basic necessity if one is to recognize and evaluate pathological changes. This study was undertaken in an attempt to establish the normal gross appearance of articular surfaces of the pectoral limb of swine. Special attention was directed to synovial fossae (nonarticulating depressions), their size, histological appearance and presence or absence in various age groups. Joint capsule attachments and contours of articular surfaces were also studied. Descriptions of synovial fossae or nonarticulating depressions on articular surfaces of ungulates exist in the literature (5,8,10,11). In most cases they are regarded as normal structures. Their importance lies in distinguishing them from pathological changes in articular cartilage. Communication between carpal joints and sites of attachment of joint capsules anci ligaments of the pectoral limb of swine have been described (7,12).
RESUME Les auteurs ont etudie les surfaces articulaires du membre pectoral, chez 50 pores, et ils en donnent une description detaillee. Les fosses synoviales n'etaient pas encore presentes chez les nouveau-nes, tandis que, chez les sujets ages de quatre a cinq mois, on les retrouvait regulierement sur la surface articulaire de l'omoplate, de l'humerus distal, du radius proximal et distal, ainsi que sur la surface distale de l'os interm6diaire du carpe. Une fois developpees, elles etaient bilat6rales et symetriques, et se situaient au fond d'une concavite de la surface articulaire. Leur aspect microscopique se traduisait par une invagination du cartilage articulaire se prolongeant dans l'os sous-chondral. L'ossification endochondrale s 'avera moins apparente au fond des fosses synoviales qu'aux endroits oiu le cartilage supporte le poids de l'animal. *Department of Veterinary Pathology, Western College of Veterinary Medicine, Saskatoon, Canada. Present address of A. Horowitz: Department of Veterinary Anatomy, College of Veterinary Medicine, Columbus, Ohio. Submitted April 3, 1974.
Vol. 39 -January, 1975
MATERIALS AND METHODS Joints of the pectoral limb of 50 swine were studied. Shoulder, elbow, antebrachiocarpal, intercarpal and carpometacarpal joints were examined in each case. The majority of limbs examined was from market weight swine (five to eight months of age). Limbs from other age groups ranging from two weeks to three years were examined as well. Limbs were recovered from a local abattoir or from a diagnostic laboratory. In the latter case death was due to a variety of causes. Many of the limbs examined were from animals whose health and nutritional status were unknown. Not all joints examined were considered to be normal. Lesions of inflammatory, degenerative and nutritional origin were observed. These were discarded from the sample.
7
Portions of bone and cartilage for histological examination were fixed in 10% neutral buffered formalin and later decalcified in 20% formic acid. Sections were cut at 6t± and stained with hematoxylineosin.
Fig. 1. Articular surface of distal right scapula. Pig six months of age. There is a centrally located synovial fossa present (arrow).
-
older animals. A ring of fibrocartilage surrounded the articular cartilage and added to the depth of the concavity. This was comparable to the labrum glenoidale in man and was most prominent caudally. In the newborn animal the articular surface was concave, smooth and uninterrupted. A central, cartilage lined synovial fossa (Fig. 1) became evident in most swine between four and six months of age. Its shape and time of appearance varied. It was most often stellate and became linear or S-shaped in older animals. In most cases it was deep and prominent at six to eight months of age.
Proximal humerus (Fig. 2) - The joint capsule attached at the edges of the articular cartilage except at the caudal margin where it sometimes attached slightly below the margin of articular cartilage. It sheathed the biceps tendon as it passed through the intertuberal groove. The biceps tendon was supported proximally by a thin mesotendon. The articular surface was smooth, convex and almost spherical in outline. This spherical outline was most perfect at birth but irregularities appeared and increased with age. Articular cartilage extended cranially beyond the main convex surface onto the greater and lesser tubercles (Fig. 2). This
RESULTS GROSS FINDINGS
-
SHOULDER JOINT
Distal scapZula (Fig. 1) - The joint capsule was inserted at the edge of the articular cartilage on all aspects of the joint except in the caudomedial area where it was inserted slightly proximal to the margin of the articular cartilage. At the craniolateral border it was reinforced by the attachment of two elastic bands. The joint capsule tended to bulge into the joint cavity on its lateral border. The articular outline was almost circular in the newborn, was roughly oval at five to six months of age and more irregular in older sows and boars. In newborn animals the line of union of the supraglenoid tubercle to the body of the scapula was visible. The articular surface was slightly flattened at the periphery in the lateral and craniomedial areas. This was most prominent in
8
-0F.F1 Y.-T cm
1
2
3
4
5
Fig. 2. Articular surface of proximal right humerus. Pig- six months of age. Articular outline is spherical. Cartilage in cranial area (A) is thin.
Can. J. comp. Med.
extension was lacking in some animals. The margin of the articular cartilage in this area was smooth and regular or irregular. In many animals two or three strands of connective tissue passed proximally from the cranial articular margin to the neighbouring synovial membrane. The articular cartilage extended cranially and distally to form the floor and walls of the intertuberal groove. In a six month old pig this groove was 2.0 - 2.5 cm in length. Tiny vascular canals penetrated the margins of the articular cartilage in the cranial, caudomedial and caudolateral areas. At five to six months of age thin areas of cartilage with a distinct blue appearance (2.0 - 2.5 cm in diameter) were often present on the cranial portion of the humeral head. In animals two to three years of age this area of cartilage remained very thin and the surface was often irregular.
ELBOW JOINT
Distal humerns (Fig. 3) - The joint capsule attached at or very close to the margins of the articular cartilage at the cranial and caudal borders. The medial and lateral portions were inserted on the medial and lateral epitrochlear surface at the edge of the articular cartilage. Articular cartilage extended onto the medial and lateral surfaces of the trochlea.
It also extended cranially to the margins of the coronoid and radial fossae and caudally to the edge of the olecranon fossa. Tiny vascular canals penetrated the medial and lateral surfaces of the trochlea. The articular surface formed a trochlea with a sagittal central groove. A narrow, deep, linear, nonarticulating depression often developed at the deepest part of this groove at four to five months of age (Fig. 3). It was absent in newborn animals and somewhat indistinct and variable in older animals (three years). It arose at the cranial margin of the articular surface and followed the depth of the central groove for one half to three quarters of the circumference of the trochlea. The medial half of the trochlea was smooth. The lateral part was divided by a low, broad, sagittal ridge. The resulting grooves and ridges were rather sharp at five to six months of age but were less prominent and well rounded at birth. Slight irregularities of the articular cartilage on the lateral part of the trochlea were commonly present in adult animals. Thin areas of cartilage (blue areas) were frequently observed caudally on the lateral part of the trochlea.
I
4cm I-
w.
I
-:!. .1-I _......
2 ...
I
3
I
4
I IV
I
S
4.
S
Fig. 4. Articular surface of proximal right radius and ulna. Pig - six months of age. There is a deep synovial fossa on the surface of the proximal radius (arrow).
S
.
Fig. 3. Articular surface of distal right humerus. Pig months of age. Trochlear surface is divided by (arrow).
- six
a deep linear groove
Vol. 39 -January, 1975
Proximal radius and ulna (Fig. 4) - The joint capsule attached at or slightly distal to the margins of the articular cartilage of the proximal radius in the medial, lateral
9
and cranial region. It attached somewhat beyond the edge of the articular cartilage of the ulna on the proximal, medial and lateral aspect of the trochlear notch. Here the articular cartilage extended well beyond the weightbearing articular surface, especially on the medial border. On the medial surface of the trochlear notch the joint capsule formed a pouch which underlay the deep digital flexor. Tiny vascular canals penetrated the cranial border of the articular cartilage of the radius. The articular surface of the proximal radius consisted of two main facets divided in the sagittal plane by a low ridge. The medial facet was smooth and slightly concave. The lateral facet was subdivided into two areas by a blunt sagittal ridge. Immediately medial to this ridge was a narrow concave facet which contained a deep, distinct, nonarticulating depression (Fig. 4). This fossa became evident at three to five months of age and persisted. Most older animals (two to three years) had deep well defined fossae at this site. Others had only a narrow linear depression. Lateral to this area was a smooth facet that was slightly concave from side to side. The curvature of these facets appeared greatest in the young and the surfaces appeared more flattened in aged sows. These facets articulate with the trochlea of the distal humerus. The articular surface of the proximal ulna consisted of the trochlear notch and the lateral facet. At the age of six months the distal one third of the articular surface of the notch was incompletely (sometimes completely) separated from the proximal two thirds by a narrow transverse line. A nonarticulating area was present immediately lateral to the distal one third of the trochlear notch. The lateral articular facet of the ulna (1.0 cm x 1.0 cm in size at six months of age) was lateral to the above nonarticulating area. In very young animals and in mature sows the articular surface of the proximal ulna was relatively more extensive and the nonarticulating area was reduced in size. ANTEBRACHIOCARPAL JOINT Distal radius and ulna (Fig. 5) - The joint capsule was inserted at the edge of the articular cartilage which extended well beyond the main weight bearing surface on the dorsal surface of the distal radius and
10
Fig. 5. Articular surface of distal right radius and ulna. Pig - six months of age. There is a linear depression (synovial fossa) on the articular surface of the distal radius (arrow).
ulna and to a lesser degree on the medial surface of the distal radius and lateral surface of the distal ulna. The articular surface of the distal radius and ulna was continuous. It consisted of three main facets. The lateral facet was deeply concave from side to side and convex in the craniocaudal direction. It was narrow craniocaudally and consisted of the articular surface of the distal ulna and a neighbouring part of the distal radius. This facet articulated with the accessory carpal bone and the ulnar carpal bone. The two remaining facets (central and medial facets) constituted the main articular surface of the distal radius. Both of these facets were concavoconvex with the concavity being cranial. A narrow, often branching linear depression that was nonarticulating was present in the dorsal concave portion of the medial facet (Fig. 5). It often extended into the concavity of the central facet. It was not present at birth but was present in most swine at five months of age. It was prominent at five to six months of age and sometimes indistinct and sometimes circular and very distinct in sows (two to three years). Two main ridges separated the three main articular facets. These passed obliquely across the joint in a craniolateral direction. As a result, when the carpus is flexed the portion of the limb distal to the carpus moves slightly medial-
Can. J. comp. Med.
ly. The two medial facets articulate with the radial carpal and intermediate carpal bones. Proximnal articutlar surface of the proximal row of carpa-l bones (Fig. 6) - The joint capsule attached at the margin of the articular cartilage which extended beyond the weightbearing articular surface on the entire dorsal aspect, on the palmar aspect of the ulnar, intermediate and radial carpal bones and on the medial surface of the radial carpal bone. The articular surface was formed by the proximal surface of the accessory carpal, ulnar carpal, intermediate carpal and radial carpal bones. A small facet on the dorsoproximal surface of the accessory carpal bone articulated with the palmar surface of the distal ulna. The proximal surface of the ulnar carpal bone was irregular (Fig. 6). It was concave from dorsal to palmar and convex mediolaterally. There was a high ridge on its dorsal and palmar ex-
slightly convex dorsally and concave in the palmar region. The proximal articular surface of the radial carpal bone was similar. The concavity and convexity were more pronounced. These two bones (intermediate and radial carpal) articulated with the corresponding concavoconvex facets of the distal radius. Nonarticulating fossae were not evident on these surfaces in any age group. Tiny linear depressions were occasionally present on the ulnar carpal bone. Ligaments securing the carpal bones appeared to be loosely attached in very young animals.
~~~~~~~~
.. '''
...
...
.'7'1'''
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'''
Fig. 7. Distal articular surface of proximal row of carpal bones, right pectoral limb. Pig - six months of age. A synovial fossa is present (arrow) on the surface of the accessory carpal bone.
*-1'
cM
I1
1
.
2I
3I
I
4
'-
1
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Fig. 6. Proximal articular surface of the proximal row of carpal bones, right pectoral limb. Pig - six months of age.
tremities. The main concavity articulated with the distal ulna. A narrow flat articular surface on its medial boundary articulated with a similar facet on the lateral surface of the distal radius. The proximal articular surface of the intermediate carpal bone was elongated from dorsal to palmar. It was
Vol. 39 -January, 1975
INTERCARPAL JOINT Distal articular surface of the proximal row of carpal bones (Fig. 7) - The joint capsule attached at the margin of the articular cartilage which extended slightly beyond the weight bearing surface except in the palmar region. The ulnar, intermediate and radial carpal bones contribute to the articular surface. The distal articular surface of the ulnar carpal bone consisted mainly of an
elongated, slightly convex (mediolateral) facet which was concave in the sagittal plane. It articulated with the fourth carpal bone. There was also a small, slightly con-
11
vex facet on its palmar extremity that articulated with the palmar extremity of the fourth carpal bone. The articular surface of the intermediate carpal bone was extensive and irregular. There were two main articular facets, medial and lateral. These two facets were separated by a ridge passing in a dorsopalmar direction. Both facets were concave in the sagittal plane and articulated with convex facets of the proximal surface of the third and fourth carpal bones. There were two small additional facets. One was located dorsomedially and articulated with a dorsal facet on the proximal surface of C3. The smaller lateral and palmar facet articulated with a similar facet on the palmar aspect of the proximal surface of C4. A nonarticulating area, about 3 mm in diameter, was present in the central ridge mentioned above (Fig. 7). This fossa was not present at birth but was commonly present in animals four to five months of age or older. The fossa was usually deep and distinct. Its position and size were the least variable of the synovial fossae observed on the articular surfaces of the joints of the pectoral limb. The distal articular surface of the radial carpal bone was usually divided into medial and lateral facets. Both facets were continuous and were not sharply divided. The lateral facet was concavoconvex with the convexity dorsal. It articulated with a convexoconcave facet of C3. The medial facet was smaller, only slightly concave and occupied the medial palmar aspect of the joint surface. It articulated with the convex surface of C2. In some swine, tiny branching linear depressions were present in the depth of the concavity of the medial facet.
Proximal articular surfacae of the distal row of the carpal bones (Cl, C2, C3 and C4) (Fig. 8) - The joint capsule attached at the margins of the articular cartilages which extended slightly beyond the main weight bearing surface in the dorsal, medial and lateral areas. Synovial fluid can flow freely from the intercarpal to the carpometacarpal joint between the dorsally opposed surfaces of C3 and C4. Cl did not always contribute to the surface of this joint. In most animals, there was a tiny facet on the proximal surface of Cl. It articulated with the palmar extremity of the radial carpal bone (distal surface). The articular surface of C2 was triangular and relatively small and convex. It articulated with the medial facet
12
of the radial carpal bone. The surface of the C3 was large and was divided into two main facets (Fig. 8). The medial facet was triangular with the base dorsal. It was concave mediolaterally and concavoconvex in the sagittal plane with the concavity dorsal. This concavity sometimes had fine linear depressions. It articulated with the larger of the two facets of the radiocarpal bone. A sagittal ridge passing from dorsal to palmar separated this facet from the lateral facet. The dorsal area of the lateral facet was concave and continuous with the palmar portion which was convex. The dorsal, concave area occasionally had tiny linear nonarticulating depressions. The proximal articular surface of the C4 was the largest of the three carpal bones. Its surface was made up of medial and lateral facets separated by a sagittal ridge. The medial facet was smooth and convex in the sagittal plane and often revealed a narrow palmar facet. It articulated with the intermediate carpal bone. The lateral facet was concave in the dorsal and palmar region. The two facets were separated by a central convex area which articulated with the ulnar carpal bone. Tiny linear depressions or infoldings of articular cartilage were seen occasionally in the palmar facet.
Fig. 8. Proximal articular surface of distal row of carpal bones, right pectoral limb. Pig - six months of age.
Can. J. comp. Med.
concave in the sagittal plane and received the convex surface of Mc4. Small oblique facets were present on the dorsomedial and palmarlateral extremities of this bone. These were both slightly concave and articulated with the dorsal and palmar extremities of Mc3 and Mc5 respectively. A small triangular dorsal facet was present also. It was slightly convex and articulated with the dorsal concavity of Mc4. Small linear depressions in the cartilage of the main concavity of C4 were observed in some animals two to three years of age.
Fig. 9. Distal articular surface of distal row of carpal bones, right pectoral limb. Pig - six months of age.
CARPOMETACARPAL JOINT Distal articular siurface of the distal rowv of carpal bones (C2, C3 and C4) (Fig. 9) The jolint capsule attached to the margins of the articular cartilage which extended slightly beyond the main weightbearing surface, especially on the dorsal surface of the joint. Cl had no distal articular surface. The distal articular surface of C2 was divided into two small facets. The palmar facet was elongated, slightly concave and articulated with the proximal surfa-ce of Mc2. The dorsal facet faced obliquely dorsolaterally and distally and articulated with the medial oblique facet of Mc3 (Fig. 9). The articular surface of C3 was extensive and consisted of two main facets, a larger dorsal facet and a smaller facet on the palmar lateral extremity. The dorsal facet was smooth and concave (dorsopalmar). It articulated with the smooth convex surface of Mc3. The palmar facet was small, flat and faced obliquely in a lateral and distal direction. It articulated with a small facet on the palmar surface of Mc3. Some animals had small depressions or nonarticulating areas in the depth of the concavity of C3. The articular surface of C4 consisted of four articular facets. The main facet was deeply
Vol. 39-January, 1975
Proximal articular surface of metacarpal bones (Mc 2, 3, 4 and 5) (Fig. 10) - The joint capsule attached at the margins of the articular cartilage which extended slightly beyond the main articular surface in the entire dorsal area and in the palmar aspect of Mc5. Metacarpal bones 2, 3, 4 and 5 contributed to the joint surface (Fig. 10). The proximal articular surface of Mc2 was divided into two tiny facets. The medial facet was almost circular, slightly convex and articulated with the palmar concavity of C2. The lateral facet was smaller and oblique. It faced proximolaterally and articulated with the palmar medial extremity of C3. The proximal articular surface of Mc3 was extensive. The central facet was the largest. It was convex from dorsal to palmar and concave from side to side. It articulated with the distal surface of C3.
CM
1
2
3
4:
Fig. 10. Proximal articular surface of metacarpal bones, right pectoral limb. Pig - two years of age.
13
A small flat facet on its medial extremity faced proximomedially and articulated with the dorsal portion of the distal surface of C2. A similar small facet in the palmar region faced obliquely proximomedially and articulated with the palmar extremity of C3 (distal surface). A third small facet was present on the lateral and dorsal aspect of the third metacarpal bone (proximal surface). It was almost flat and articulated with the dorsal medial extremity of the distal surface of C4. The proximal articular surface of Mc4 was concavoconvex with the concavity dorsal. Tiny linear depressions were present in the dorsal concavity and near the palmar border in some adult animals. Mc4 articulated with the coneavoconvex surface of C4. The articular surface of Mc5 faced obliquely proximally and medially. It was small and slightly concavoconvex (or convex only) with the concavity dorsally. It articulated with the oblique facet on the palmar lateral surface of C4. MICROSCOPIC FINDINGS
Histologically, synovial fossae were represented as an invagination or infolding of articular cartilage (Figs. 11 and 12). The depth and width were variable. In animals six months of age the entire surface was covered with cartilage, in older animals fossae present on the proximal radius and the proximal surface of the intermediate carpal bone sometimes lacked a cartilaginous covering at the depth of the depression. The thickness of cartilage
Fig. 12. Histological appearance of synovial fossa on the articular surface of the proximal radius. Pic six months of age. H & E. X15.
lining synovial fossae was variable but was often less than the thickness of articular cartilage on weightbearing surfaces. There was no evidence of collapse of underlying bone (e.g. fractured trabeculae, fibrosis, etc.). Evidence of endochondral bone formation (aligned, proliferating, hypertrophic, chondrocytes) was less apparent in the depth of synovial fossae than in areas of articular cartilage on the weight bearing surface.
DISCUSSION
Fig. 11. Histological appearance of linear groove which divides the trochlear surface of the distal humerus. Pig - six months of age. H & E. X10.
14
Artictular cartilage on the weightbearing surfaces of synovial joints is the final recipient of mechanical forces acting on the skeleton. It is elastic to intermittent pressure due to exudation and resorption of fluid (1). In the immature animal two areas of growth exist, the upper midzonal area is responsible for maintaining the thickness of articular cartilage whereas the deep zone provides for growth of the epiphysis (1). Although normal articular cartilage grows throughout life it does so with less vigor in old age (6). Regeneration is limited if injuries are confined to articular cartilage. Injuries which extend into subchondral bone are repaired by fi-
Can. J. comp. Med.
!1 _> ~ ~ ~ ~(1, 6, 9).
ness of articular cartilage whereas prolonged continuous compression results in degenerative changes or pressure necrosis
a-^
Synovial fossae were absent in all cases birth but were present in a high percentage of swine at 90 kg body weight. They were bilaterally symmetrical. Most were located at the depth of an articular concavity. The time of appearance, size, "-i shape and persistence of any given fossa varied considerably. The absence of syno- ~vial fossae -at birth suggested that they are llot remnants of embryological processes. It is possible that they develop in the normal process of bone and cartilage formation due *:._.:to a lack of or a reduction of weight bearing stimuli in these areas. Differences in rate of growth and nutritional status of the animal as well as differences in physical stresses acting on any given joint surface may account for variation observed in size, shape and time of appearance of synovial
"@ i IIat
_'g:Es Y':\ ........................................................
Am
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...
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Fig. 13. Humeral head of pig (five months of age)
w ith multiple, linear areas of articular collapse secondary to nutritional osteodystrophy.
brous tissue or fibrocartilage (1). In the present study considerable variation in contours of articular surfaces was observed among randomly selected swine. This is consistent with reports by other workers (1, 3) who observed that although articular surfaces develop according to an inherited pattern they may be altered by physical stresses. Variations in thickness of articular cartilage observed between individual animals and within a single joint may be the result of different rates of attrition and cartilage formation. It has been established that functional stimuli facilitate growth of articular cartilage (1) and that the apposition of articular surfaces is important in the maintenance of normal articular cartilage (2). Since articular cartilage is avascular (9) and receives its nutrition
fossae. It is important to distinguish synovial fossae from areas of articular collapse due
.
iv
\;
intercellular substance (1, 4, 9), intermittent compression associated with normal movement and weightbearing is important in the maintenance of normal articular cartilage (3). Vigorously exercised cartilage has been shown to be thicker than
unusued cartilage. Excessive, intermittent
*. compression may result in increased thlckin
increased
Vol. 39 -January, 1975
tk
.,
:
--
Fig. 14. Microscopic appearance of areas of articular in Fig. 13. Note the disruption of subcollapse chondral shown bone. H & E. X15.
is
to weakness of underlying bone (Figs. 13 and 14). Synovial fossae may be distinguished by anatomical site and histological appearance. REFERENCES 1. BAUER, W., M. W. ROPES and H. WAINE. The physiology of articular str-uctures. Physiol. Rev. 20: 272-312. 1940. 2. BENNETT, G. A., W. BAUER and S. J. MADDOCK. A study of repair of articular cartilage and the reaction of normal joints of adult dogs to surgically created defects of articular cartilage, "joint mice" and patellar displacement. Am. J. Path. 8: 499-524. 1932. 3. BOLLET, A. J. An essay on the biology of osteoarthritis. Arthritis Rheum. 12: 152-163. 1969. 4. BROWER, T. D. and WAN-YI HSU. Normal articular cartilage. Clin. Orthop. and Related Res. 64: 9-17. 1969.
16
5. COHRS, P. and G. MESSOW. Musculoskeletal system. In Joest's Handbook of the Special Pathological Anatomy of Domestic Animals. Edited by J. Dobberstein, G. Pallaske and H. Stiinzi. 3rd Ed. Vol. 1. p. 221. Berlin and Hamburg: Verlag Paul Parey. 1969. 6. JOHNSON, L. C. Kinetics of osteoarthritis. Lab. Invest. 8: 1223-1241. 1959. 7. KOSTYRA, J. Joints of the extremeties of the pig. Part I. The foreleg. Annals Univ. Mariae CurieSklodowska 14: 240-265. 1959. 8. NICKEL, R., A. SCHUMMER and E. SEIFERLE. Lehrbuch der Anatomie der Haustiere. Vol. I. p. 178. Berlin and Ham-burg: Paul Parey. 1961. 9. SALTER, R. B. and P. FIELD. The effects of continuous compression on living articular cartilage. J. Bone Jt Surg. 42A: 31-49. 1960. 10. SCHWARZE, E. and L. SCHRODER. Kompendium der Veterinar-Anatomie. Vol. 1. p. 127. Jena: Veb Gustav Fischer Verlag. 1960. 11. SISSON, S. and J. D. GROSSMAN. The Anatomy of the Domestic Animals. 4th Edition. p. 210. Philadelphia and London: W. B. Saunders Co. 1953. 12. WISSDORF, H. and K. NEURAND. Das Karpalgelenk des Schweines-Grundlagen fur die Gelenkinjektion. Dt. tierarztl. Wschr. 73: 396-404. 1966.
Can. J. comp. Med.
