Location of radiological lesions of the thoracolumbar column in French trotters with and without signs of back pain.

The radiographs of 102 French trotters presented with signs of back pain were reviewed retrospectively, and a control group of 16 French trotters without back pain was analysed. The age, sex, type of race, number of starts, earnings and index of performance were recorded. Radiological evaluation was performed from the 14th thoracic (T14) to the third lumbar (L3) vertebra. Impingement of the spinous processes (ISP), periarticular proliferation of synovial intervertebral articulations (PP-SIA) and sclerosis of SIA (S-SIA) were located and graded. Radiological lesions were identified in 10 (62 per cent) of horses in the control group and 98 (96 per cent) of horses in the clinical group. The number of affected horses, the number of radiological lesions per horse and the mean number of affected intervertebral spaces were significantly higher in the clinical group. For ISP, the number of affected horses was not significantly different between the groups, but the number of affected interspinous spaces and the grade of lesions were significantly higher in the clinical group. For PP-SIA, the number of affected horses, the number of affected SIA and the grade of lesions were significantly higher in the clinical group. For S-SIA, the number of affected horses and the number of affected SIA were not significantly different between the groups but the grade of lesions was significantly higher in the clinical group. In both groups, ISP was most commonly encountered between T15-T18 and PP-SIA and S-SIA were most commonly encountered between T17-L2. Radiographic lesions of the back were less severe and more localised in horses without back pain than in those with back pain.