Disorders of the thoracolumbar spine of the horse--a survey of 443 cases.

The survey comprised 443 horses, referred to the clinical department of the Equine Research Station, with a history of a thoracolumbar (TL) complaint. A wide range of lesions were capable of producing back problems and more than one condition or site of injury was found in 75 animals (17 per cent). There were 103 horses (19.7 per cent) with no evidence of damage to the TL spine or its associated structures. In 66 of these cases, clinical signs were attributed to a variety of hindlimb lamenesses and, in 37, no specific diagnosis could be made. Soft tissue injury was diagnosed in 203 cases (38.8 per cent), the most frequent sites being the longissimus dorsi muscles and/or the supraspinous ligament in the caudal withers and cranial lumber regions. Chronic sacroiliac strain or mild sacroiliac instability was also a frequent cause of low back trouble in competitive horses. Other conditions included tying-up, subluxation of a lumbar vertebra and neuritis of the cauda equina. Fifteen cases (2.9 per cent) of vertebral malformations were found including scoliosis, lordosis and kyphosis. Vertebral lesions accounted for 202 (38.6 per cent) of the diagnoses. The most common condition was associated with crowding and overriding of the dorsal spinous processes in the caudal thoracic and cranial lumbar regions. This was most often diagnosed in competitive jumping horses (173 cases) and caused a loss of suppleness and spinal flexibility resulting in lowered performance and bouts of back pain. There was a comparatively low incidence of fractures (13 cases) and degenerative spondylosis (14 cases).