IN-VIVO EVALUATION OF INTRAMEDULLARY INTERLOCKING NAIL FIXATION OF TRANSVERSE FEMORAL OSTEOTOMIES IN FOALS

Objective-To evaluate an intramedullary interlocking nail for stabiliz ation of transverse femoral osteotomies in foals. Study Design-A trans verse osteotomy and restabilization with an intramedullary interlockin g nail was performed on the right femur in three foals and the left fe mur in three foals. Animals-Six foals weighing 149 to 207 kg. Methods- The femur was destabilized with a transverse middiaphyseal osteotomy a nd repaired with a 0.5-in (12.7 mm) interlocking nail. The implanted f emurs were radiographed monthly until completion of the study 6 months after surgery. At the completion of the study, all foals were observe d for evidence of lameness, gluteal thickness was determined by ultras onographic measurement, and a necropsy was performed. Results-Healing was satisfactory in all foals. Five of the six had osseous bridging of the osteotomy apparent radiographically by 3 to 4 months. The sixth f oal had postoperative infection but was healed radiographically in 5 m onths. There was a mean decrease in gluteal muscle thickness of 6.6 mm (P =.04) in the operated limb of the five foals that healed without c omplication. Two foals were lame at the completion of the project; one foal with varus deformities of the contralateral limb was mechanicall y lame, and another was grade 2/5 lame on the operated limb. On necrop sy, there was circumferential enlargement of the diaphysis of all oper ated limbs with the majority of the callus at the cranial and medial a spects of the cortex. All nails were solid within the medullary cavity . Conclusions-The intramedullary interlocking nail provided adequate s tabilization for repair of the transverse osteotomy. Clinical Relevanc e-Further investigation is warranted before use for stabilization of s pontane ously occurring fracture configurations. (C) Copyright 1998 by The American College of Veterinary Surgeons.