Page 294 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Musculoskeletal system: 1.7b The axial skeleton – thoracolumbar region 269

VetBooks.ir 1.510 1.511

Fig. 1.510 Intraoperative view of surgery to remove Fig. 1.511 Interspinous ligament desmotomy is
several thoracic dorsal spinous process (DSP) tips. The a minimally invasive alternative surgical treatment
surgeon has removed a wedge of bone from the cranial for kissing spines. The spinal needle is placed in the
aspect of the caudal DSP and the caudal aspect of the space to aid triangulation, while Mayo scissors are
cranial DSP, thereby removing the bony interference used to cut the interspinous ligament in the area of
at this point. (Photo courtesy Graham Munroe) impingement.

triangular profile and preventing further impinge- Aetiology/pathophysiology
ment. Interspinous ligament desmotomy, whereby The pathogenesis of chronic supraspinous and
impinging DSPs are surgically divided in the area of interspinous desmitis is not clearly defined, nor
impingement is a minimally invasive alternative with separated from that of other thoracolumbar pathol-
lower morbidity and cost (Fig. 1.511), allowing as ogies, such as DSP impingement, facet disease and
many as 13 impinging spaces to be treated simulta- ventral spondylosis. Like most known ligaments,
neously. The technique is often associated with star- the supraspinous ligament is biologically active,
tlingly rapid resolution of symptomatic back pain, growing in size in response to tension and weak-
leading some to suggest that it is a neurectomy. There ening with immobilisation, with increased osteo-
is no evidence that this is the case and the mechanism clastic activity at the ligament–bone interface,
of action is currently unknown. Operated spaces the enthesis (Fig. 1.512). This may predispose to
frequently widen after surgery and treated horses DSP avulsion injury or ligament tearing if loaded
can return to riding in as little as 4 weeks. Horses suddenly (Fig. 1.513).
undergoing traditional surgery require significantly
longer time off to allow for increased duration of Clinical presentation
wound healing. Regardless of the surgical technique, There is likely to be little or no difference in clini-
a period of active non-ridden rehabilitation is consid- cal presentation to the other forms of back pain
ered vital before riding restarts. described in this chapter. Acute supraspinous desmi-
tis can present as a discrete focal firm swelling over
SUPRASPINOUS DESMITIS one to five DSPs in the dorsal midline. More exten-
sive chronic desmitis is much harder to identify due
Definition/overview to generalised thickening, potentially limiting the
The supraspinous ligament is conjoined physically palpation of DSPs.
and functionally with the interspinous ligament.
Injuries broadly fall into two subtypes: acute trauma Differential diagnosis
and chronic overuse. Overlap exists, however, since Soft-tissue and bone trauma; saddle pinch or pres-
chronic desmitis may weaken ligaments and predis- sure; vertebral facet disease; supraspinous desmitis;
pose to acute injury. DSP impingement; and ventral spondylosis.