Outcome and radiographic assessment of the development of osteoarthritis in 15 horses with rupture of collateral ligaments and joint instability in metacarpophalangeal or metatarsophalangeal joints

Abstract

In this study, the long-term outcome and the development of osteoarthritis (OA) after collateral ligament (CL) rupture in metacarpophalangeal (MCP) or metatarsophalangeal (MTP) joints with either open or closed MCP / MTP joints was evaluated. Horses were included in the study on the basis of radiographic evidence of subluxation or luxation in stressed MCP / MTP joints in the dorsopalmar / dorsoplantar (DP) view. Horses were clinically and radiographically evaluated at first presentation in the clinc as well as at follow-up examination. Fifteen horses met the inclusion criteria. Lameness varied between 2 / 5 to non-weightbearing lameness. Three horses presented with a clinically severely instable fetlock. Opening of the MCP / MTP joint as consequence of associated wounds or lacerations was diagnosed in 4 horses. In 11 horses CL rupture without opening of the associated MCP / MTP joint was diagnosed (no wounds communicating with the MCP / MTP joint). Six of these horses were treated conservatively, 5 were treated surgically. Three months after admission 11 horses were sound at walk and trot. Three horses showed a grade 3-4 / 5 lameness. One of these was euthanatized 6 weeks later because severe OA had developed in the injured MTP joint. Another horse had been euthanized because of laminitis. In 12 horses long-term follow-up examination (9 months – 12 years) was possible. All horses showed radiographic signs of OA in the affected MCP / MTP joint. In 6 horses there was also mild to moderate OA in the PIP joint of the affected limb. 67% (n = 10) of the horses returned to be used for pleasure riding as prior to injury, 13% (n = 2) of the horses remained pasture sound, 20% (n=3) were euthanatized because of persistent lameness. The study shows the long-term prognosis of CL ruptures with open and closed MCP / MTP joints. In horses with chronic lamness after CL rupture in MCP / MTP joint the PIP joint should also be considerd as a potential source of pain.