Horses are commonly treated for proximal suspensory ligament (SL) desmitis of the hindlimb with neurectomy of the Deep Branch Lateral Plantar Nerve (neur-DBLPN). We hypothesized that denervating the SL would cause atrophy of the muscle fibers of the SL. The hindlimbs of 5 horses were used. One had a neur-DBLPN performed 120 days before tissue harvest. The other had SL desmitis induced by collagenase injection 42 days prior to a neur-DPLPN (as above). The hind SLs of 10 untreated horses were used as controls. The morphological characteristics (width and thickness) of the proximal aspect of SLs were determined using calipers and the muscle cross-sectional area from microphotographs using computer-software. Results showed that width, thickness and cross-sectional area from both treatment groups were significantly less than the controls. Limbs undergoing collagenase injection had statistically greater changes relative to those that had neur-DBLPN alone. When compared to control horses, muscle fibers of DBLPN-treated horses had nuclei located centrally; nuclear rowing and clusters; and infiltration of the ligament with fat and connective tissue. Our study showed that the muscular portion of the proximal aspect of the SL atrophies significantly more when the DBLPN is excised beyond that of collagenase-induced disease alone. Studies are needed to determine the clinical consequences of surgical intervention as the changes may predispose the horse to re-injury.
