High field (4.7 T) magnetic resonance imaging of feline hip joints

Magnetic resonance imaging (MRI) is a non-invasive technique widely used to investigate degenerative joint disease (DJD). In this study, we obtained magnetic resonance images of feline hip joints, using a high magnetic field MRI unit (4.7 tesla) with proton density (PD)-weighted and T2-weighted fast spin-echo (FSE). PD-weighted FSE provided detailed anatomical images of feline hip joints with superb depiction of subchondral bones of the femoral head and acetabulum. Articular cartilage (AC) was also visualized with PD-weighted and T2-weighted FSE; however, mild AC lesions noted on gross examination were not detectable with these sequences.     

PREVALENCE OF COMPUTED TOMOGRAPHIC SUBCHONDRAL BONE LESIONS IN THE SCAPULOHUMERAL JOINT OF 32 IMMATURE DOGS WITH THORACIC LIMB LAMENESS

Osteochondrosis is a common developmental abnormality affecting the subchondral bone of immature, large breed dogs. The purpose of this retrospective study was to describe CT lesions detected in scapulohumeral joints of 32 immature dogs undergoing CT for thoracic limb lameness. Eight dogs (14 scapulohumeral joints) had arthroscopy following imaging. Thirteen dogs (19 scapulohumeral joints) were found to have CT lesions, including 10 dogs (16 scapulohumeral joints) with subchondral bone lesions and 3 dogs with enthesopathy of the supraspinatus tendon. In one dog, subchondral bone lesions appeared as large oval defects within the mid‐aspect of the glenoid cavities, bilaterally. These lesions resembled osseous cyst‐like lesions commonly identified in the horse. This is the first report of such a presentation of a subchondral bone lesion in the glenoid cavity of a dog. In all dogs, small, focal, round or linear lucent defects were visible within the cortical bone at the junction of the greater tubercle and intertubercular groove. These structures were thought to represent vascular channels. Findings from this study support the use of CT as an adjunct modality for the identification and characterization of scapulohumeral subchondral bone lesions in immature dogs with thoracic limb lameness.     

Subchondral bone density and cartilage degeneration patterns in osteoarthritic metacarpal condyles of horses

OBJECTIVE: To evaluate and correlate patterns of subchondral bone density and articular cartilage degeneration (derived by use of gross, histologic, and computed tomographic [CT] examinations) in equine third metacarpal condyles with and without osteoarthritis. SAMPLE POPULATION: 8 metacarpophalangeal (MCP) joints (n = 4 horses) without osteoarthritis and 6 osteoarthritis-affected MCP joints (4). PROCEDURES: Horses were euthanized. The third metacarpal condyles of the joints were examined grossly and via CT (3 slice images/condyle). For 6 condylar zones, mean bone density and pattern of density distribution were determined. Data for osteoarthritis-affected and control joints were compared. Histomorphometric point count analyses identified areas of bone density for comparison with CT density measurements. RESULTS: Osteoarthritis-affected condyles had heterogeneous subchondral bone with focal resorptive lesions and patterned sclerosis, whereas control condyles had symmetric bone density distribution. In osteoarthritis-affected condyles, bone density determined via gray scale image density analysis was greater (dorsal and medial pattern), compared with control condyles, and differed among zones because of resorption and sclerosis. With regard to bone density in osteoarthritis-affected condyles, histologic findings correlated with CT images, and bone lesions were significantly correlated with cartilage lesions. CONCLUSIONS AND CLINICAL RELEVANCE: In horses, heterogeneous distribution and greater subchondral bone density were characteristic of osteoarthritis-affected condyles, compared with control condyles. Subchondral bone lesions correlated with overlying cartilage lesions in osteoarthritis-affected MCP joints. Identification of CT image characteristics appears to predict the presence of a cartilage lesion in MCP joints of horses with osteoarthritis.     

Primary degenerative joint disease of the shoulder in a colony of beagles

Shoulder joints of 149 Beagles over 8 years old at the time of death (mean age, 13.8 years +/- 3.21), were examined radiographically throughout their life-times for the frequency of degenerative joint disease (DJD). Clinical histories revealed no underlying cause for DJD. The shoulder joints of a subgroup of 18 dogs were examined at necropsy, and thin sections of the joints were evaluated radiographically and histologically. Serial clinical radiographic studies indicated that normal shoulder joint development during the first year of life was followed by the appearance of subchondral bone sclerosis and bony remodeling of normal joint contour, and by the formation of periarticular osteophytes and enthesiophytes. All changes were progressive with age and typical for DJD in dogs. Bilateral involvement was common. Evaluation of specimens obtained at necropsy revealed: articular cartilage change with roughening of the surface layer, degeneration and death of superficial chondrocytes, exposure of deeper layers of chondrocytes that had proliferated with fissuring of the damaged cartilage, total cartilage loss with polishing of the exposed subchondral bone, mixed patterns of subchondral bone sclerosis and osteoporosis, change in contour of the articular surfaces, and formation of periarticular osteophytes and enthesiophytes. Joint capsule thickening, synovitis, pannus formation, and synovial chondroma formation were observed. Because of the available clinical information, in addition to the typical changes of DJD, it was thought that the changes were primary. Instability appeared to play a role in the pathogenesis of the joint disease described; however, it was not clear whether the instability caused abnormal forces on healthy cartilage or whether the primary cartilage wear caused the instability.     

Effect of computed tomography display window and image plane on diagnostic certainty for characteristics of dysplastic elbow joints in dogs

OBJECTIVE: To test the effects of computed tomography (CT) image plane and window settings on diagnostic certainty for CT characteristics associated with dysplastic elbow joints (elbow joint dysplasia) in dogs and to provide optimal display guidelines for these CT characteristics. SAMPLE POPULATION: CT images of 50 dysplastic elbow joints from 49 lame dogs and 10 elbow joints from 5 sound dogs. PROCEDURES: CT image data were obtained in transverse, sagittal, and dorsal planes. Each plane was examined by use of 3 Hounsfield unit (HU) window settings. Two veterinary radiologists independently evaluated sets of CT images for evidence of 7 CT characteristics. Effect of elbow joint status, image plane, and window settings on diagnostic certainty for these CT characteristics was tested by use of a visual analogue scale. RESULTS: Diagnostic certainty for abnormalities of the medial coronoid process (MCP) and radial incisure was highest in the transverse plane, subchondral defects or sclerosis of the trochlea humeri was highest in the dorsal plane, and joint incongruity was highest in the sagittal plane. Certainty for hypoattenuating subchondral defects or fissures was highest at 2,500 or 3,500 HUs, whereas certainty for subchondral sclerosis was highest at 1,500 HUs and lowest at 3,500 HUs. CONCLUSIONS AND CLINICAL RELEVANCE: Diagnostic certainty for CT characteristics of elbow joint dysplasia in dogs was affected by image display variables. Diagnostic certainty for altered subchondral bone density was primarily influenced by window settings, whereas structural MCP abnormalities and joint incongruity were influenced most by image plane.     

COMPARISON BETWEEN SHOULDER COMPUTED TOMOGRAPHY AND CLINICAL FINDINGS IN 89 DOGS PRESENTED FOR THORACIC LIMB LAMENESS

Computed tomography (CT) is an established technique for detecting shoulder lesions in dogs, however the clinical significance of shoulder CT lesions often remains uncertain. The purposes of this retrospective study were to describe the prevalence of CT lesions in both shoulder joints for 89 dogs presenting with thoracic limb lameness and to compare CT lesions with clinical characteristics. For all included dogs, results of a full orthopedic examination, other diagnostic tests, and signalment data were available in medical records. Multilevel, multivariable logistic regression was used to test clinical significance of the most prevalent CT lesions and determine factors associated with their presence. Computed tomographic lesions were detected in one or both shoulder joints for 51/89 dogs (57.3%). Mineralization of one or more surrounding peri‐articular soft‐tissue structures was identified in 31.5% of dogs, with supraspinatus muscle/tendon mineralization being the most frequently identified (24.7%). The prevalence of humeral head osteochondrosis was 9 and 21.3% of dogs had shoulder osteoarthritis. Border collies (odds ratio [OR] 9.3; 95% CI 1.39–62.1, P = 0.02) and dogs with shoulder pain (OR 4.3; 95% CI 1.08–17.1, P = 0.04) had increased risk of osteochondrosis lesions. Border collies (OR 8.4; 95% CI 1.27–55.6; P = 0.03) and older animals (OR 1.04; 95% CI 1.02–1.1, P < 0.001) had increased risk of osteoarthritis lesions. Female entire dogs had an increased risk of supraspinatus mineralization lesions (OR 6.8; 95% CI 1.55–29.5, P = 0.01). Findings indicated that shoulder CT lesions are common in dogs with thoracic limb lameness, and that some CT lesions are not associated with shoulder pain.     

Pathologic changes in the lumbosacral vertebrae and pelvis in Thoroughbred racehorses

OBJECTIVE: To describe the prevalence, characteristics, and severity of soft-tissue and osseous lesions in the caudal portion of the thoracic and lumbosacral vertebral column and pelvis in Thoroughbred racehorses. ANIMALS: 36 Thoroughbred racehorses that died or were euthanatized at California racetracks between October 1993 and July 1994. PROCEDURE: Lumbosacral and pelvic specimens were collected and visually examined for soft-tissue and osseous lesions. RESULTS: Acute sacroiliac joint injury was observed in 2 specimens. Signs of chronic laxity or subluxation of the sacroiliac joint were not observed in any specimens. Impingement of the dorsal spinous processes and transverse processes was observed in 92 and 97% of specimens, respectively. Thoracolumbar articular processes had variable degrees of degenerative change in 97% of specimens. Degenerative changes were observed at lumbar intertransverse joints and sacroiliac articulations in all specimens. Some degenerative changes were widespread and severe. CONCLUSIONS: Numerous degenerative changes affected vertebral processes, intervertebral articulations, and sacroiliac joints in these Thoroughbred racehorses. CLINICAL RELEVANCE: Various types of vertebral and pelvic lesions need to be considered during clinical evaluation of the back and pelvis in horses. Undiagnosed vertebral or pelvic lesions could be an important contributor to poor performance and lameness in athletic horses.     

Spinal arthropathy associated with Ochrobactrum anthropi in free-ranging cane toads (Chaunus [Bufo] marinus) in Australia

Inflammatory or degenerative pathology involving the vertebral bodies and/or ventral intervertebral joints has been described in numerous species, both captive and free ranging, including mammals, birds, and snakes, although never in amphibians. We described 15 cases of a newly recognized spinal arthropathy in adult cane toads (Chaunus [Bufo] marinus), an invasive species in Australia. Grossly appreciable lesions consisted primarily of ventral proliferation of bone and cartilage that resulted in ankylosis. Histologic examination of the entire vertebral columns of the 15 affected toads revealed 13 toads to have lesions at multiple intervertebral sites, totalling 41 intervertebral joints with lesions. Most lesions involved bone and cartilage proliferation that resulted in fusion of the joint, with (n = 15) or without (n = 9) associated pyogranulomatous inflammation. In the remaining 17 affected joints, histologic lesions were characterized by degeneration of articular cartilage without joint fusion. In addition, in one of these joints, there was also hemorrhage and pyogranulomatous inflammation. Bacterial culture of affected joints in 9 toads and grossly normal joints in 4 control toads resulted in isolation of Ochrobactrum anthropi in 7 affected toads but in none of the controls (P < .01). We proposed an interaction between degenerative and bacterial etiologies in the pathogenesis of this condition. Invasive toads may be predisposed to this condition because of their large size; increased rates of movement; and, possibly, immunosuppression resulting from inhabiting a novel environment.     

MRI features of cervical articular process degenerative joint disease in Great Dane dogs with cervical spondylomyelopathy

Cervical spondylomyelopathy or Wobbler syndrome commonly affects the cervical vertebral column of Great Dane dogs. Degenerative changes affecting the articular process joints are a frequent finding in these patients; however, the correlation between these changes and other features of cervical spondylomyelopathy are uncertain. We described and graded the degenerative changes evident in the cervical articular process joints from 13 Great Danes dogs with cervical spondylomyelopathy using MR imaging, and evaluated the relationship between individual features of cervical articular process joint degeneration and the presence of spinal cord compression, vertebral foraminal stenosis, intramedullary spinal cord changes, and intervertebral disc degenerative changes. Degenerative changes affecting the articular process joints were common, with only 13 of 94 (14%) having no degenerative changes. The most severe changes were evident between C4-C5 and C7-T1 intervertebral spaces. Reduction or loss of the hyperintense synovial fluid signal on T2-weighted MR images was the most frequent feature associated with articular process joint degenerative changes. Degenerative changes of the articular process joints affecting the synovial fluid or articular surface, or causing lateral hypertrophic tissue, were positively correlated with lateral spinal cord compression and vertebral foraminal stenosis. Dorsal hypertrophic tissue was positively correlated with dorsal spinal cord compression. Disc-associated spinal cord compression was recognized less frequently.     

Comparison between magnetic resonance imaging,computed tomography,and arthrography to identify artificially induced cartilage defects of the equine carpal joints

While articular cartilage changes are considered to be one of the initial events in the pathological cascade leading to osteoarthritis, these changes remain difficult to detect using conventional diagnostic imaging modalities such as plain radiography. The aim of this prospective, experimental, methods comparison study was to compare the sensitivity of magnetic resonance imaging (MRI), magnetic resonance arthrography, computed tomography (CT), and CT arthrography in the detection of artificially induced articular cartilage defects in the equine carpal joints. Defects were created in the antebrachiocarpal and middle carpal joint using curettage by a board‐certified equine surgeon. Normal articular cartilage thickness varied from a maximum of 1.22 mm at the level of the distal aspect of the radius to a minimum of 0.17 mm in the proximal articular surface of the third carpal bone. Regarding cartilaginous defect measurements the remaining cartilaginous bed range from a maximum of 0.776 mm in the partial thickness defects, and 0 mm (defect reaches the subchondral bone) when total thickness defect were made. Computed tomography and magnetic resonance imaging were performed followed by CT arthrography and magnetic resonance arthrography after antebrachiocarpal and middle carpal intraarticular contrast administration. All images were reviewed by two board‐certified veterinary radiologists, both of whom were blinded to the location, presence of, and thickness of the cartilage defects. A total number of 72 lesions in nine limbs were created. Mean sensitivity for localizing cartilage defects varied between imaging modalities with CT arthrography showing the best sensitivity (69.9%), followed by magnetic resonance arthrography (53.5%), MRI (33.3%), and CT (18.1%) respectively. The addition of contrast arthrography in both magnetic resonance and CT improved the rate of cartilage lesion detection although no statistical significance was found. Computed tomographic arthrography displayed the best sensitivity for detecting articular cartilage defects in the equine antebrachiocarpal and middle‐carpal joints, compared to magnetic resonance arthrography, MRI, and CT.     

European veterinary dissertations

Diseases affecting synovial joints are a major cause of chronic disability both in humans and in companion animal species, most notably dogs and horses. As progressive deterioration of the articular cartilage is the hallmark of degenerative joint disease or osteoarthritis, research efforts traditionally tended to focus primarily on cartilage pathology. However, in recent years it has become clear that synovial joints should be considered intricate organs in their own right, with each of the constituent tissues (cartilage, bone, and synovial membrane) interacting with each other both in health and disease. Moreover, with the advent of modern molecular biology techniques, the importance of synovial inflammation in disease development and progression has become increasingly recognized. These realizations have spurred the need for tools that allow a more comprehensive, integral study of synovial joint homeostasis. This review provides a brief overview of synovial joint biology and the concept of joint homeostasis, followed by a discussion of methods that may be used to study joint homeostasis (varying from in vitro tissue culture to in vivo imaging) including specific advantages and limitations of each approach. It then zooms in on one such approach, synovial fluid biomarker analysis, as a promising avenue in synovial joint research, highlighting some results from equine studies performed in the author's own laboratory that illustrate how such studies may help shed light on in vivo joint homeostasis and therapeutic modulation thereof. The review concludes with some future perspectives and promising developments in the field.     

SUBCLINICAL CT ABNORMALITIES IN THE LUMBOSACRAL SPINE OF OLDER LARGE-BREED DOGS

Computed tomography (CT) of the L5-S3 vertebral levels was performed in six, large-breed dogs presented for problems unrelated to the lumbosacral spine. All dogs were asymptomatic for lumbosacral stenosis on neurologic examination. Breeds included German Shepherd, Golden Retriever, Boxermix and Belgian Malinois. Ages ranged from 5-12 years. Five out of six dogs exhibited CT abnormalities. Among the 18 disc levels examined, the most common findings were idiopathic stenosis, loss of vertebral canal epidural fat, and nerve tissue displacement. Less common abnormalities were vertebral canal or foraminal bone proliferation, loss of intervertebral foramen fat, vertebral canal disc bulging, degenerative articular process joint disease, transitional vertebra, dural ossification, foraminal disc bulging, Schmorl's nodes, calcified extruded disc fragment, and sacroiliac joint osteophytes. Vertebral subluxation was absent in all dogs. Findings indicate that some lumbosacral CT abnormalities may be clinically insignificant, especially in older dogs.     

Temporomandibular joint ankylosis in cats and dogs. A report of 10 cases.

Temporomandibular joint (TMJ) ankylosis is characterized by difficulty or inability to open the mouth. The ankylosis may be articular ('true') or extra-articular ('false'). Clinical signs, radiographic studies, treatment and follow-up are presented in a retrospective study involving five cats and five dogs. The findings were compared with TMJ ankylosis in humans. CT imaging with three-dimensional reconstruction proved to be of great value in determining the extent of the abnormalities and helped with preoperative planning. Articular TMJ ankylosis occurred in six animals and extra-articular TMJ ankylosis was found in the other four cases. In three cats and in three dogs, the TMJ ankylosis was trauma related; the remaining patients were diagnosed with a tumour. Resection of ankylosing tissue in false ankylosis or gap arthroplasty in true ankylosis was successful in all of the trauma induced cases. In the two cats, with tumour related ankylosis, the ankylosis was caused by an osteoma and resection had a good prognosis, whereas the two dogs had to be euthanatized.     

COMPARISON OF GROSS AND HISTOPATHOLOGIC FINDINGS WITH QUANTITATIVE COMPUTED TOMOGRAPHIC BONE DENSITY IN THE DISTAL THIRD METACARPAL BONE OF RACEHORSES

Comparison of subchondral bone density determined by quantitative computed tomography (CT) with gross and histopathologic changes have not been made in horses. The goal of this study was to determine if mean quantitative CT density and mean voxel standard deviation are associated with the presence and severity of osteochondral lesions in the palmar aspect of the distal third metacarpal bone in racing horses. Metacarpophalangeal joints from nine racehorses were imaged using CT and scored for gross damage. Four-millimeter-thick sagittal and 30 degrees palmar dorsal plane sections were cut, decalcified and stained with hematoxylin and eosin from the distal third metacarpal bone. Microscopic osteochondral lesions and subchondral remodeling were scored on a scale of 0-3. Percent subchondral bone, expressed as the ratio of bone volume to tissue volume, was also measured. Mean quantitative CT density and mean voxel standard deviation were measured from three-dimensional models of CT images comparable with histologic sections. Mean quantitative CT density was not associated with lesion severity or number of lesions. A weak correlation between mean quantitative CT density and gross score was found, but mean quantitative CT density was not predictive for gross score. Mean voxel standard deviation was not correlated with gross or histopathologic measures, but was predictive of mild osteochondral lesions. Results support the association of subchondral remodeling with the development of palmar metacarpal lesions. However, there was not a strong correlation between mean quantitative CT density or mean voxel standard deviation and histopathologic lesions of the distal third metacarpal bone.     

COMPARISONS AMONG RADIOGRAPHY,ULTRASONOGRAPHY AND COMPUTED TOMOGRAPHY FOR EX VIVO CHARACTERIZATION OF STIFLE OSTEOARTHRITIS IN THE HORSE

A better understanding of imaging characteristics of equine stifle osteoarthritis (OA) may allow earlier detection and improve prognosis. Objectives of this ex vivo, prospective, methods comparison study were to (1) describe the location and severity of naturally acquired OA lesions in the equine stifle using ultrasound (US), radiography (XR), computed tomography (CT), and macroscopic evaluation (ME); (2) compare the diagnostic performance of each imaging modality with ME; and (3) describe subchondral bone mineral density (BMD) in equine stifle joints with OA using CT. Radiographic, CT, and US evaluations were performed on 23 equine cadaver stifles and compared with ME. Significant associations were found between osteophyte global scores for all imaging modalities (CT, P ? 0.0001; XR, P = 0.005; US, P = 0.04) vs. ME osteophyte global scores. Osteophytes were detected most frequently in the medial femorotibial (MFT) joint. A specific pattern of osteophytes was observed, with a long ridge of new bone at the insertion of the MFT joint capsule cranially on the medial femoral condyle. A novel caudo‐10°proximo‐5°lateral‐cranio‐disto‐medial oblique radiographic projection was helpful for detection of intercondylar osteophytes. Multiplanar CT reformatted images were helpful for characterizing all osteophytes. Osteophyte grades at most sites did not differ among modalities. Low sensitivity/specificity for subchondral bone sclerosis and flattening of femoral condyles suggested that these signs may not be reliable radiographic and CT indicators of equine stifle OA. Equine stifle OA was associated with a decrease in BMD and specific sites of focal subchondral bone resorption/cyst formation were found in some specimens.     

The use of advanced vs. conventional imaging modalities for the diagnosis of subchondral bone injuries

Damage to the subchondral bone has been associated with a number of orthopaedic diseases. Diagnostic imaging is, therefore, critical in identifying disease and damage of the subchondral bone, not only for the diagnosis of joint and subchondral bone disease causing lameness, but also for identifying early/pre-symptomatic damage. The aims of this Critically Appraised Topic (CAT) were to assess the published evidence for the use of advanced imaging techniques (magnetic resonance imaging [MRI] and computed tomography [CT]) in the diagnosis of subchondral bone disease in the distal limb joints (metacarpo/metatarsophalangeal and interphalangeal joints) of the adult horse, and to compare the diagnostic value of these techniques with radiography. In the studies reviewed in this CAT, advanced imaging modalities (MRI and CT) were superior to routine radiography for the diagnosis of subchondral bone injury of the distal limb joints. In a small percentage of horses, post-MRI reevaluation of the initial radiographs or acquiring further lesion-orientated radiographs allowed the identification of the subchondral bone injury. Extended radiographic examinations, including non-standard views, might increase the sensitivity of radiography to detect subchondral bone injuries, however, currently CT and MRI may be considered the “gold standard” imaging modalities. More studies comparing the identification of subchondral bone lesions on imaging and by histopathological/gross examination would be useful to assess more precisely the sensitivity and specificity of the different modalities.     

Functional Anatomy and Biomechanics of the Canine Hip Joint

Introduction: In many breeds osteoarthrosis of the hip joint is the most typical orthopaedic disease. Numerous studies concerning etiology, pathogenesis and therapy of this disease still consider an exact congruity to be the basis of a physiological joint function. No data, however, are available as far as the distribution of load in the articular surfaces is concerned. Aims: It was the aim of this investigation to describe the biomechanical features of the canine hip joint as exactly as possible with respect to long‐term and momentary loading. Material and Methods: Hip joints from 43 dogs (bodyweight >20 kg) with an average age of 6 years were investigated. The subchondral bone density was determined with the method of CT‐osteoabsorptiometry. With help of cartilaginous and osseus split lines the preferential orientation of the collagen fibres could be determined. In an in vitro experimental setup the contact areas and the contact pressure distribution within the joint have been measured. Results: In the acetabulum, maxima of subchondral bone density were distributed tricentrically: cranially, dorsally and caudally. In the femoral head, only the area close to the attachment of the ligament was highly mineralized. Cartilagineous and osseous split lines within the acetabulum gave evidence of a long‐term tensile stress. In contrast to these findings, there was no clear preferential orientation in the caput ossis femoris. With load increasing initially isolated contact areas extended and became confluent at a loading force of 75% body weight. Values of maximal joint pressure (maximal joint reaction force applied: 400% bodyweight) reached 8–10 MPa. Discussion: The findings clearly show that the articular surfaces of the hip joint are loaded inhomogeneously. For the first time, it was possible to demonstrate that the healthy canine hip joint is physiologically incongruent. Furthermore, areas of cartilage degeneration within the joint surface coincide with regions that are loaded to a higher extent a priori. From the biomechanical point of view it is recommended that all kinds of acetabular fractures – even those affecting the caudal third of the acetabulum – should be surgically repaired in an adequate way.     

Sacroiliac Joint of the Horse 1. Gross morphology

A total of 22 morphological features were described in the sacroiliac joints of 41 horses which had no history of any low back condition. Some dramatic differences in both sacral and iliac aspects of joint shape and articular surfaces were seen according to age. These findings were thought to be due to progressive cartilaginous degeneration. Only minor significant differences were seen between left and right sacroiliac joints or between breeds and sex. The iliac surface was more prone to degenerative change. Ankylosis of the joints was not recorded and the incidence of articular or para-articular spur formation was low.