INTRODUCTION: Proximal check ligament desmotomy has been used to treat superficial digital flexor (SDF) tendinitis. However, suspensory ligament desmitis has been observed after desmotomy. Cadaveric biomechanical studies demonstrated higher SDF tendon and suspensory ligament strains after desmotomy. Perhaps clinical improvement is unrelated to desmotomy. This study further explored the effects of proximal check ligament desmotomy on soft tissue strains using simulations of the entire stance phase of the gallop. MATERIALS AND METHODS: A musculoskeletal model (8 linked-segments, 6 joints, 9 muscle-tendon units, 16 ligament sets) was implemented (SIMM). Bone geometries, muscle-tendon and ligament paths, and segment inertial properties were obtained from MRI/CT data (4 yr female TB). Joint kinematics were obtained from MRI/CT data and mechanical testing of cadaveric limbs. Muscle-tendon forces were directly measured or based on a Hill type model. Software (SD/FAST, Dynamics Pipeline) was used to simulate the stance phase of gallop, and desmotomy. RESULTS: Desmotomy reduced overall limb stiffness and redistributed forces between remaining intact structures. Peak fetlock hyperextension angle increased by 5 degrees at 23% stance. Peak vertical ground reaction force was 375N less at 27% stance. The pastern joint flexed less (8 degrees at 20% stance) and the coffin joint flexed more (7 degrees at 55% stance). Suspensory ligament and SDF tendon strains increased by 0.2% and 0.8%, respectively, for 25-70% of stance. DISCUSSION: These results provide supporting evidence that proximal check ligament desmotomy does not decrease strain in the SDF tendon and it may predispose the suspensory ligament to injury. A case-control study of 1) recovery from SDF tendinitis and 2) incidence of suspensory ligament injury, after proximal check ligament desmotomy, is warranted in clinical cases.
Effects of simulated proximal check ligament desmotomy on fetlock support structures of the equine forelimb fetlock throughout stance phase of gallop.
ZARUCCO, Laura;
2004-01-01
Abstract
INTRODUCTION: Proximal check ligament desmotomy has been used to treat superficial digital flexor (SDF) tendinitis. However, suspensory ligament desmitis has been observed after desmotomy. Cadaveric biomechanical studies demonstrated higher SDF tendon and suspensory ligament strains after desmotomy. Perhaps clinical improvement is unrelated to desmotomy. This study further explored the effects of proximal check ligament desmotomy on soft tissue strains using simulations of the entire stance phase of the gallop. MATERIALS AND METHODS: A musculoskeletal model (8 linked-segments, 6 joints, 9 muscle-tendon units, 16 ligament sets) was implemented (SIMM). Bone geometries, muscle-tendon and ligament paths, and segment inertial properties were obtained from MRI/CT data (4 yr female TB). Joint kinematics were obtained from MRI/CT data and mechanical testing of cadaveric limbs. Muscle-tendon forces were directly measured or based on a Hill type model. Software (SD/FAST, Dynamics Pipeline) was used to simulate the stance phase of gallop, and desmotomy. RESULTS: Desmotomy reduced overall limb stiffness and redistributed forces between remaining intact structures. Peak fetlock hyperextension angle increased by 5 degrees at 23% stance. Peak vertical ground reaction force was 375N less at 27% stance. The pastern joint flexed less (8 degrees at 20% stance) and the coffin joint flexed more (7 degrees at 55% stance). Suspensory ligament and SDF tendon strains increased by 0.2% and 0.8%, respectively, for 25-70% of stance. DISCUSSION: These results provide supporting evidence that proximal check ligament desmotomy does not decrease strain in the SDF tendon and it may predispose the suspensory ligament to injury. A case-control study of 1) recovery from SDF tendinitis and 2) incidence of suspensory ligament injury, after proximal check ligament desmotomy, is warranted in clinical cases.
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