Chapter 52Thoracolumbar Spine
Back problems are a major cause of altered gait or performance (see Chapters 50, 51, and 97). Both identification and documentation of vertebral lesions are difficult in horses; therefore treating back pain is a challenge for the equine clinician. The equine back is a large area covered by thick muscles. Therefore assessment of the bony elements is limited. Every joint in the thoracolumbar region has restricted mobility; therefore detecting changes in restricted movement when the horse is working is difficult. Diagnostic imaging of the thoracolumbar region is also limited, and radiological assessment requires special equipment. Specific treatment of back pain can only be performed after complete identification of the site and nature of the lesions.
Diagnosis of Back Pain
Back pain may also be manifest by abnormal behavior, for example, bucking (see page 992).
Physical Examination
Examination during Movement
Evaluation of the horse moving at walk, trot, and canter is essential to assess whether pain is present and to identify functional disorders, such as limitation of regional intervertebral mobility (Figure 52-5). The clinician should always bear in mind that impinging spinous processes can be present asymptomatically. Therefore the clinical significance of impinging spinous processes should not be overinterpreted, unless clinical signs of back pain are evident. The horse should be assessed moving in straight lines and in small circles at a walk and trot on a hard surface and moving at a trot and canter on the lunge to determine whether any reduction of back mobility is apparent (Table 52-1).
Examination of the Horse Being Ridden or in Harness
The presence and the degree of back pain may be underestimated unless the horse is evaluated under its normal working conditions, that is, ridden or in harness. The influence of a rider on mobility of the horse’s back has recently been quantified.16 The clinician should watch carefully as the tack or harness is applied, particularly as the girth is tightened. However, the clinician should bear in mind that cold-back behavior (see Chapter 97) is not necessarily a reflection of back pain, although it may be. The fit of the saddle for the horse and the rider should be evaluated. Back mobility,3 the movements that the horse finds difficult, and the horse’s attitude toward work should all be assessed (see Chapter 97). The clinician should pay attention also to the observations of the rider because the horse may feel considerably worse than it appears. The rider may describe lack of hindlimb power, lateral stiffness of the back to the left or right, unwillingness of the horse properly to take the bit, or loss of fluidity in the paces. The rider may complain of back pain induced by riding the horse.