ith severe DSP lesions were more likely to have osteoarthritis in the IVAs. But there were also horses with radiographic evidence of ‘kissing spines’ that had no IRU associated with DSPs on bone scan images. Moderate or severe IRU associated with the IVAs was more likely seen in horses with clinical signs of back pain than in normal horses in a study from Gillen et al (2009).
The advantage of applying scintigraphy is the ability to identify dynamic processes of bone modeling and remodeling associated with the entire spine. These processes are either adaptive or pathologic and require careful interpretation, as findings are not necessarily associated with pain. Bone scan is a useful diagnostic tool to help ruling out other regions possibly mimicking back pain, such as the sacroiliac joint region.
Diagnostic local anaesthesia is considered the most important test to confirm that clinical signs of back dysfunction are associated with impingement of DSPs (Walmsley et al 2002). Horses that tolerate injections, are safe to ride and show a consistent, repeatable problem or behaviour are most suitable candidates. The effect of diagnostic local anaesthesia is usually assessed by performing a ridden examination (or other exercise test) before and 10-20 minutes after infiltration of the local anaesthetic solution (Marks 1999; Walmsley et al 2002; Denoix and Dyson 2003). The test is considered positive, if a marked improvement of performance can be recognised by both the rider and the veterinary surgeon. Interpretation difficulties without objective measurements such as interpretation bias should be borne in mind.
In a study of Roethlisberger Holm et al (2006) the back of horses without clinical signs of back pain or lameness was infiltrated with local anaesthetic solution. Kinematics of the back were measured showing an affect on the function of the back. An increased range of motion for dorsoventral flexion-extension resulting in improved flexibility was possibly due to an altered neuromuscular activity by injections made into the multifidus muscle. These findings should be taken into account to avoid false interpretation.
Possible causes of back pain
Underlying causes for back pain can be grouped into three main categories: Pathology-causing primary back pain; pathology causing secondary back pain; and rider/tack-inflicted back pain. Furthermore, problems such as sacroiliac joint region pain, neck pain or rib fractures may result in clinical symptoms similar to the ones of back pain.
Pathology causing primary back pain
• Impinging dorsal spinous processes (‘kissing spines’)
• Arthropathy of the articular process joints in the thoracolumbar spine
• Ventral spondylosis
• Desmopathy of the supra- and intraspinous ligament
Pathology causing secondary back pain
• Lameness (particularly hindlimb lameness)
Rider or tack-inflicted back pain
• Poor saddle fit
• Unsuitable riding or training techniques (eg. rollkur, overuse of draw reins)
• Poor riding skills (novice, unbalanced riders)
• Lack of fitness/strength of the horse
• Excessive rider weight
An important part of successfully treating back pain is to include physiotherapy in the rehabilitation and to establish a suitable exercise programme depending on the individual case and underlying cause.
There are a number of conservative and surgical treatment options available for primary conditions of back pain. Corticosteroid injections can be employed by infiltrating areas of DSP impingement or by ultrasound-guided periarticular injection of the articular process joints. Other treatment options such as acupuncture, mesotherapy, bisphosphonate medication and extracorporeal shockwave therapy may be considered by some practitioners. Surgical treatment options such as DSP resection or interspinous ligament desmotomy have been described and are available to treat ‘kissing spine’ syndrome.
If lameness has been identified, it is important to diagnose and treat the lameness prior to treating the back in order to achieve successful and long-lasting results.