Denervating the Pelvic Suspensory Ligaments of Horses Causes Morphological and Histological Changes in the Ligaments

OBJECTIVE To examine changes occurring in normal pelvic suspensory ligaments (SLs) of horses after denervating these ligaments and to investigate the effect chronic inflammation might have on these changes. ANIMALS 10 horses. PROCEDURES The SL of 1 randomly selected pelvic limb of each of 5 horses was injected with collagenase to induce desmitis, and 42 days later, the proximal aspect of both pelvic SLs were denervated. The SLs were harvested 120 days after being denervated, and the morphological and histological characteristics of each collagenase-injected, denervated SL were compared with those of the contralateral, non-injected, denervated SL. All denervated SLs were compared with non-denervated pelvic SLs harvested from 5 horses similar in weight and age. RESULTS The mean width and the cross-sectional area of the musculature of all denervated SLs were significantly less than that of the non-denervated ligaments. The mean thickness of collagenase-injected denervated ligaments, but not that of the non-injected denervated ligaments, was significantly less than that of the non-denervated ligaments. Histological abnormalities typical of neurogenic muscular atrophy were observed in all denervated ligaments. CLINICAL RELEVANCE Loss of motor neuronal input to the proximal aspect of the SL of the pelvic limb of horses causes neurogenic atrophy of the musculature in that portion of the ligament. Denervating a SL of a pelvic limb may weaken the ligament, increasing its risk of injury. Chronic inflammation of the SL before neurectomy may exacerbate atrophy of the musculature after neurectomy.