Meniscal lesions in knee joints of broiler fowls.

Post-mortem examination of the knee joints of 28 broiler type fowls revealed abnormalities in one or both medial menisci. Certain abnormalities appeared to be associated with knee ligament disruption. These included torn or frayed menisci and those which were displaced, usually in a mesial direction. Histopathological studies revealed that each of these abnormalities was normally associated with degenerative meniscal lesions. Other meniscal abnormalities showed no association with knee ligament disruption. Such menisci can be regarded as being of aberrant shape and most commonly the medial meniscus was enlarged and "discoid". Discoid medial menisci frequently showed histological abnormalities. As in other species, it is suggested that discoid menisci are predisposed to injury probably because of their larger contact area.

Further studies of degenerative hip disease; antitrochanteric degeneration in turkeys and broiler type chickens.

Postmortem examination revealed antitrochanteric degeneration in turkeys (8 male, 2 female) and broiler type chickens (5 male, 1 female). Antitrochanteric degeneration was detected in birds aged 20 weeks or older but histological examination identified lesions in others with grossly normal antitrochanters. Normal and abnormal antitrochanteric development was studied in male, skeletally immature, turkeys and broilers. Differential subchondral bone growth occurred, with relatively delayed ilial bone development. As a result, hyaline cartilage was retained dorsally and persisted even in adult birds. Retained hyaline, and in younger birds growth plate, cartilage was prone to osteochondrosis. When cartilage flap formation involved fissures traversing retained hyaline cartilage, the term osteochondrosis dissecans was appropriate. In other cases of antitrochanteric degeneration, changes typical of osteoarthrosis were present with, in some instances, no evidence of pre-existing osteochondrosis. Certain sites of antitrochanteric cartilage may be susceptible to fatigue failure in these cases.

Dyschondroplasia/osteochondrosis of the femoral trochanter in the fowl.

Of 104 lame broilers, 12 birds with femoral trochanteric abnormalities were identified by post-mortem and radiographic examination. Defects occurred in ossification of either the trochanteric zenith or its medial aspect. Lesions were identified as dyschondroplasia, osteochondrosis or osteochondrosis dissecans affecting the articular surface of the femoral trochanter. In the absence of concomitant musculoskeletal disease, degrees of lameness can be attributed to trochanteric lesions. Breaches in the medial trochanteric bone plate permit granulation tissue repair of the articular surface. This repair process, however, did not compensate for the loss of articular surface contour and the junction of reparative and normal tissue may be prone to subsequent degeneration.

Hip instability in young adult, broiler fowls.

In a study of spontaneous orthopaedic disease in 104 broiler-type birds fed ad lib, 14 cases of hip instability were detected. Female birds were commonly affected and all were aged between 20 and 30 weeks. Although hip luxation was not identified, in most cases the gait abnormality could be attributed to capital femoral ligament failure. There were two main patterns of capital femoral ligament disruption; either the ligament was avulsed, together with a cartilage fragment, from its foveal attachment, or the ligament itself was partially or totally ruptured. Histological evidence suggests that repetitive trauma or acute trauma of sufficient magnitude may be necessary for ligament disruption. It is likely that the excessive weight gain of ad-lib fed birds predisposes to ligament damage.

Avulsion of muscles from the femoral trochanter in the fowl.

Post-mortem examination revealed lateral femoral trochanteric defects in 14 out of 104 broiler type chickens. All birds were severely lame, and in the absence of concomitant musculoskeletal disease trochanteric lesions were implicated in their clinical signs. Trochanteric muscle insertions had avulsed and the lateral metaphyseal defect was usually lined with granulation tissue. Examination of normal trochanteric development identified endochondral ossification at sites of muscle attachment. In some skeletally immature, proximal femurs evidence of osteochondrosis was detected at sites of trochanteric muscle attachment. It is deduced that broiler femoral trochanters are susceptible to muscle avulsion by virtue of their known predisposition to osteochondrosis and the pattern of muscle insertion.

Cruciate ligament rupture in young adult broiler knee joints.

Derangement of the caudal cruciate ligament was identified in 11 broiler fowls aged between 18 and 38 weeks. In some cases, the caudal cruciate ligament alone was ruptured, whereas, in others, the caudal meniscofemoral and meniscotibial ligaments and medial meniscus were also deranged. In some birds, ligaments were only partially ruptured but, in 5 cases, complete rupture had occurred in both knee joints. All birds showed severe lameness which, in 2 cases, could only be ascribed to caudal cruciate derangement. Degenerative changes were present in many of the ligaments which suggested that rupture may be a consequence of primary ligamentous change. Proximal tibiotarsal osteochondrosis was a frequent concomitant finding which may affect the integrity of the ligament attachment. A number of other factors including postural abnormality, obesity, and relative inactivity may predispose broilers to caudal cruciate ligament rupture.

Fractured fibulae in broiler fowls.

Fibular diaphyseal fractures were identified bilaterally or unilaterally in 15 broilers aged between 13 and 105 days. Incomplete cortical defects were also identified on radiographs in a further 8 birds. Fractures and incomplete defects always occurred at the Tuberculum M. iliofibularis of fibulae. The character of bone at this site differed from bone elsewhere in the diaphysis. Following fracture, cartilaginous callus united the diaphyseal segments and pseudarthrosis or fibrous non-union were common sequelae. The concept that fibular fractures in broilers are always a consequence of abnormal proximal tibiotarsal curvature is not supported by this study. It is suggested that differential growth of the paired crural bones is of primary importance.

Disturbed endochondral ossification in the axial skeleton of young broiler fowls.

Physeal lesions have been studied in thoracic vertebrae (T3, T4 and T5) of 51 broiler fowls between 28 and 53 days old. Vascular perfusion studies performed on 10 birds confirmed that the cartilaginous epiphyses of T3, T4 and T5 were essentially avascular and thus differ from those of the major long bones. Findings confirm the observation that a number of morphologically distinct lesions of osteochondrosis occur in broiler fowls and that, when physeal clefts can be implicated in their aetiology, the term "osteochondrosis" is inappropriate. Although the location of clefts often differs in long bone and vertebral physes, when metaphyseal vessels are disrupted, the end-result on endochondral ossification is the same in both the axial and appendicular skeleton. Other lesions were observed both independently and in association with osteochondrosis. Such lesions include necrotic seams devoid of haemorrhage, acellular foci and chondrolysis, all of which were most frequently observed in the same vertebral end-plates. Because osteochondrosis was also most common in the same vertebral end-plates, a common aetiology is suggested. Surface regressive changes were common in the articular cartilage of T3, T4 and T5, and it is noteworthy that such changes, although common in older birds, are present in birds so young.

Vascular changes in induced abnormal bone growth in lambs.

In lambs, unilateral hip excision arthroplasty induced angular and torsional deformities in the contralateral limb and the vascular changes associated with abnormal bone growth in distal tibiae and metatarsi have been studied. Eosinophilic septa separating physeal cartilage columns were more frequent and prominent in association with physeal osteochondrosis. Epiphyseal vessels traversed thickened physeal cartilage to an abnormal depth and resulted in protrusions of epiphyseal bone and an irregular epiphyseal bone plate. In some cases, epiphyseal vessels crossed the whole physis and arboresced after turning through 180 degrees. This vascular pattern appears to occur as a reparative response.

Histopathology of growth plate changes in induced abnormal bone growth in lambs.

Unilateral hip excision arthroplasty in lambs resulted in osteochondrosis developing in distal tibiae and metatarsi of the contralateral pelvic limb. The physeal cartilage of distal tibiae and metatarsi developed clefts which probably represent shear failure. The histopathology of the meataphyseal defects differed between the medial and lateral growth plate sectors. Medially, the lesions were typical of physeal osteochondrosis in other mammals, with disorganized chondrocyte columns, cell death and matrix necrosis. Laterally, metaphyseal defects were predominantly fibrous, and islands of bone formed in physeal cartilage from re-established endochondral ossification. Both medial and lateral metaphyseal defects were associated with disturbed primary spongiosa formation. It is suggested that, in some instances at least, traumatic physeal clefts, resulting from shear failure in previously normal growth cartilage, may interfere with endochondral ossification and produce osteochondrosis.

Morphological and radiological findings in induced abnormal bone growth in lambs.

Unilateral hip excision arthroplasty in skeletally immature lambs resulted in altered load bearing and posture in the contralateral limb. Derangement of endochondral bone growth occurred in distal tibiae and metatarsi and both angular and torsional deformities developed. There was no absolute correlation between torsional and angular deformities. Although femoral torsion was variable, the unoperated pelvic limbs frequently developed exaggerated internal torsion of tibiae and metatarsi. Tibiae of operated limbs developed less torsion than was seen in control animals. These findings suggest that functional limb loading can modify developing bone torsion and that torsional deformities in lambs may be a consequence of increased functional torque.

Windswept deformities in poultry.

"Windswept deformities", involving valgus angulation of one intertarsal joint and varus angulation in the contralateral limb, were identified in 75 of 120 turkeys and 24 of 120 broiler fowls which had been culled because of lameness, so that windswept limb angulation was more common in turkeys than broilers. A proportion of cases can be more accurately described as unilateral intertarsal varus deformities with physiological valgus angulation of the contralateral limb. In other cases, marked angulation of one limb probably results from adoption of an altered posture secondary to deformity of the contralateral limb. No correlation was found between abnormal bone torsion, limb angulation and dyschondroplastic lesions. In broilers, almost 70 per cent of windswept limbs with 20 degrees or more intertarsal angulation showed physeal disturbance in the distal tibiotarsus or proximal transometatarsus or both. This finding supports the concept that windswept deformities are commonly associated with physeal lesions but whether the two conditions are causally related is uncertain.

Rupture of the intercondylar ligament in intertarsal joints of broiler fowls.

On examination of the intertarsal joints of approximately 150 lame broiler fowls, the intercondylar ligament was found to be ruptured, either partially or totally, in 22 birds. In some cases, rupture of the intercondylar ligament occurred in joints with gross angulation and usually in association with collateral ligament instability. In other birds, intercondylar ligament rupture occurred in limbs with minimal angulation but often with concomitant ligament or tendon failure in the same or contralateral limb. A fibrovascular layer was frequently identified between collateral ligaments and their distal tibiotarsal attachment. Haemorrhage in the fibrovascular tissue appears to be responsible for the establishment of the cyst-like structures which were present in some distal tibiotarsi.

Destructive cartilage loss in the joints of adult male broiler breeding fowls.

Patterns of destructive cartilage loss were studied in 60 male broiler breeding fowls. All showed destructive lesions in their hip or intertarsal joints and were between 18 and 62 weeks old when killed. Although surface regressive changes in articular cartilage were common, deep fibrillation, as seen in human and mammalian osteoarthrosis, was not identified. This difference probably reflects the more fibrous nature of articular cartilage in birds, but a number of similarities to hyaline cartilage degeneration were noted. Destructive cartilage loss resulted from partial or full thickness detachment of uncalcified cartilage. Clefts in deep cartilage preceded segmental detachment and occurred in cartilage with an intact articular surface. Detachment of segments of uncalcified cartilage may be the principal method of destructive cartilage loss in all avian species. It is concluded that clefts and destructive cartilage loss in adult broiler fowls can be a consequence of articular osteochondrosis or may result from osteoarthrosic lesions.

Thinning of articular cartilage in the domestic fowl.

Thinning of articular cartilage was identified in pelvic limb joints of broiler and Leghorn-type fowls. Almost all of 100 fowls examined showed cartilage thinning or loss in hip and knee joints. Particular attention was paid to proximal femora; in these, the principal mechanism of cartilage loss involved processes described as "peripheral remodelling". From the edge of cartilage sheets, fibrovascular tissue removed articular cartilage by two mechanisms. Either a pannus of fibrovascular tissue covered the articular surface or non-osseous tissue invaded through discontinuities in the bone plate. As in man, peripheral remodelling appears to be age-related and unrelated to regressive or destructive cartilage loss.

Further studies on knee ligament failure in broiler breeding fowls.

A group of 88, predominantly male, broiler breeding fowls was examined and, in 38, knee ligament failure was identified. All birds were aged between 15 and 60 weeks when examined. Although derangement of the caudal cruciate ligament was the most frequent finding (25 birds), partial or total rupture of the cranial cruciate ligament was also identified (10 birds). Medial (10 birds) and lateral (5 birds) collateral ligament failure was also noted. Knee ligament failure may, in part, be age related. The most frequent concomitant finding in individual birds was tendon or ligament failure elsewhere in the same skeleton. It can therefore be assumed that male broiler breeding fowls are predisposed to ligament and tendon failure and a high proportion will have lesions at more than one skeletal site.

Physeal clefts and disturbed endochondral ossification in broiler fowls.

Histopathological studies have been conducted on 35 physes from 19 broiler type fowls of different ages in order to elucidate the pathogenesis of dyschondroplasias. Findings support the suggestion that different forms of dyschondroplasia occur in broiler fowls and that histopathological studies are required if each is to be distinguished. It is concluded that physeal clefts produce one form of dyschondroplasia when epiphyseal blood vessels are occluded. A unifying concept is proposed that implicates epiphyseal and/or metaphyseal vascular disturbances in the differing morphology of some lesions, at least. This concept is supported by findings in this and other studies and is proposed as a possible explanation for morphological differences between avian dyschondroplasia and mammalian osteochondrosis.

Osteochondrosis dissecans in turkeys.

The lesions in 3 turkeys with articular cartilage flap formation and associated osteoarthrosis are described. Since cartilage flap formation was accompanied by a disturbance in endochondral ossification, the diagnosis of osteochondrosis dissecans could be made. The site of lesions in 2 of the cases demonstrated that an adjacent ossific nucleus is not a necessary prerequisite for animal osteochondrosis dissecans. In addition, the site of the lesion in these 2 cases support the suggestion that the junctions of contact and non-contact areas of an articular surface are predisposed to pathological change.

The histopathology of degenerative hip disease in male breeding turkeys.

Age-related degenerative changes are present in the antitrochanteric cartilage of male turkeys at 1 year of age. More severe change involved areas of matrix necrosis and fissures which were even detected in antitrochanters which appeared superficially normal. Superficial matrix necrosis produced cartilage surface changes which were observed in fresh specimens before histological preparation. Degenerative hip disease with stages of cartilage flap formation and osteoarthrosis showed a pronounced matrix necrosis of both hyaline and fibrecartilage. Matrix failure may represent a response to excessive forces which the intercellular collagen cannot withstand. In male turkeys, excessive loading could provide repetitive trauma of a magnitude which produces irreparable joint damage.

The morphology of degenerative hip disease in male breeding turkeys.

A form of degenerative joint disease in male breeding turkeys has been studied. Initial lesions occurred in the antitrochanteric region of the acetabulum. A surface cleft appeared in antitrochanteric cartilage and free cartilage bodies were subsequently released into the joint cavity. Secondary osteoarthrosis developed, involving both the femoral and acetabular components of the coxofemoral joint. Lesions of the antitrochanter were graded according to their severity and provide a pathological sequence. Of 59 male breeding turkeys examined at approximately one year of age, antitrochanteric lesions were present in all but 5 of them. The disease was not seen in 20 females of comparable age.