Metacarpophalangeal joint injury patterns on magnetic resonance imaging: A comparison in racing Standardbreds and Thoroughbreds

Abstract

The metacarpal condyle has received extensive attention as a predominant site of overload arthropathy in racehorses. However, detailed descriptions of MRI lesion patterns for the metacarpophalangeal joint and comparisons between types of racing horses are currently lacking. Aims of this retrospective, cross-sectional study were to describe and compare standing low-field magnetic resonance findings in the metacarpophalangeal joints for groups of Standardbreds and Thoroughbreds using systematic semiquantitative scores. Data archives at the Clinique Vétérinaire Equine de Chantilly and Imavet were searched during the period from June 2010 to February 2016. Images were retrieved and reviewed by one reader. A total of 30 Standardbreds and 77 Thoroughbreds were sampled. The Thoroughbreds developed a much higher rate of stress fractures (40.3% vs. 10%) and overall more severe scores of subchondral sclerosis and bone marrow lesions than Standardbreds. The Standardbreds had more sites of subchondral bone defect and resorption, as well as higher synovitis and joint capsule thickening scores. Both Standardbreds and Thoroughbreds frequently developed multifocal subchondral lesions not limited to the distal palmar condyle. The Standardbreds had a higher tendency to develop dorsomedial joint pole subchondral injuries. Both Standardbreds and Thoroughbreds developed a noticeably high rate of periarticular soft tissue injuries (36.7% in Standardbreds and 20.8% in Thoroughbreds), which were rarely considered as the main contributors to the lameness. Findings supported the use of low-field MRI as a whole-organ assessment tool for Standardbreds and Thoroughbreds with suspected metacarpophalangeal joint injuries.

Bone marrow lesions of the distal condyles of the third metacarpal bone are common and not always related to lameness in sports and pleasure horses

“…The prevalence of bone marrow lesions in the distal condyles of the third metacarpal bone in this population of sports and pleasure horses (76.5%) was surprisingly high in comparison with previous reports …”

“…Bone marrow lesions were noted and graded in six different anatomical locations of the distal condyle of third metacarpal bone: the palmar and dorsal portions of the lateral condyle, the palmar and dorsal portions of the sagittal ridge area and the palmar and dorsal portion of the medial condyle of the distal aspect of the third metacarpal bone (Figure ). Lesions were graded from 0 to 3 according to the extent of signal change . For grading the extent of lesions in sagittal and transverse planes, the dorsal and palmar halves of distal third metacarpal bone were divided into three equal thirds, while the height of the condyle was divided into three equal thirds for grading lesions in the dorsal plane (Figures and ).…”

“…Injury of the metacarpophalangeal joint is a frequent cause of pain causing lameness and poor performance in sports horses . While conventional diagnostic imaging techniques like radiography and ultrasonography often fail to identify any abnormalities, the increased use of MRI and scintigraphy have highlighted the importance of bone mineral densification and bone marrow lesions in subchondral bone injury. Subchondral bone injuries of the metacarpophalangeal joint are well recognized in Thoroughbred racehorses, and are also described as a significant cause of pain causing lameness in mature sports horses …”

“…Degenerative lesions may be characterized by osteonecrosis, fibrosis, vascular congestion, and edema while traumatic injuries may be characterized by bone contusion with interstitial edema and/or interstitial hemorrhage . Two recent studies have evaluated subchondral injury of the metacarpophalangeal joint in Thoroughbred racehorses with low field MRI . Bone marrow lesions were most commonly seen in association with palmar osteochondral disease in Thoroughbred racehorses and severity of palmar osteochondral disease increased with age and with the number of races run .…”

“…Bone marrow lesions were most commonly seen in association with palmar osteochondral disease in Thoroughbred racehorses and severity of palmar osteochondral disease increased with age and with the number of races run . A recent study comparing osseous injury patterns of the metacarpophalangeal joint in Thoroughbred and Standardbred racehorses with low field MRI, showed that bone marrow lesions in Standardbred racehorses occur more frequently in the dorsal aspect of the medial condyle of the third metacarpal bone. Others have evaluated metacarpophalangeal joint injury of sports and racehorses using high‐field MRI, and have found subchondral bone injury to be a frequent cause of pain causing lameness.…”