Summary
Two young adult endurance horses were presented for investigation of sudden‐onset forelimb lameness during competition. Clinical examination revealed a severe forelimb lameness and pain on palpation of the proximal palmar metacarpal area. Initial radiographic survey of the affected forelimb was unremarkable in both cases. A week of box rest resulted in only a mild improvement in the lameness. A second radiographic examination did not reveal any significant abnormalities. In both cases, scintigraphic examination was suggested, but was declined by the owner, and the lameness had significantly improved after local infiltration of 3 mL of anaesthetic solution in the proximal suspensory region. Radiographic and ultrasonographic examinations of the carpus and proximal suspensory region were unremarkable in Case 2. Case 1 had increased thickness of the medial lobe of the proximal aspect of the suspensory ligament. A computed tomographic examination was performed and an incomplete longitudinal (fatigue) fracture of the proximal third metacarpal bone was detected. After 8 months of box rest and rehabilitation, re‐examination revealed resolution of the lameness in both cases. Advanced diagnostic imaging should be considered in young endurance horses with severe lameness during competition or training, in which radiographic and ultrasonographic examinations are unremarkable or do not explain the severity of the lameness. Computed tomography imaging is considered a useful diagnostic imaging technique to detect incomplete longitudinal palmar metacarpal cortical (fatigue) fractures due to its ability to provide excellent bone detail.
OBJECTIVE
The purpose of this prospective study was to investigate the prevalence and severity of radiographic abnormalities of the interspinous spaces (ISSs) in the thoracolumbar vertebral column of unbroken yearlings and to compare these findings with a group of older trained Thoroughbred horses without perceived back pain.
ANIMALS
Yearlings (n = 47) and trained horses (55); 102 total.
PROCEDURES
Each horse underwent a digital radiographic study of the thoracolumbar vertebral column (T7–L3) and each space graded for narrowing of the ISSs, increased opacity, radiolucency, and modeling of the cranial and caudal margins of 2 contiguous dorsal spinous processes (DSPs). This generated both an individual anatomical space score for each space and a total score for each horse for subsequent comparison. Statistical analysis of the results was then undertaken.
RESULTS
Narrowing and impingement were detected in a third of the examined ISSs, while DSP increased opacity, radiolucencies, and modeling were found in over half of the yearlings. The median total score per horse was 33 (0 to 96) in the yearlings and 30 (0 to 101) in trained horses, indicating no significant difference in radiographic abnormalities (P = .91). Likewise, the median total score per anatomical space was 112 (25 to 259) and 127.5 (24 to 284) in the yearlings and trained horses (P = .83). No differences were found between the groups for number of radiographic abnormalities, scores, and total score.
CLINICAL RELEVANCE
This study reported the incidence of DSP radiographic abnormalities in Thoroughbred horses. The absence of difference in occurrence between yearlings and older horses supported a developmental rather than acquired etiology.
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