In Vivo Evaluation of Intramedullary Interlocking Nail Fixation of Transverse Femoral Osteotomies in Foals

Objective—To evaluate an intramedullary interlocking nail for stabilization of transverse femoral osteotomies in foals.
Study Design—A transverse osteotomy and restabilization with an intramedullary interlocking nail was performed on the right femur in three foals and the left femur in three foals. Animals—Six foals weighing 149 to 207 kg.
Methods—The femur was destabilized with a transverse middiaphyseal osteotomy and repaired with a 0.5-in (12.7 mm) interlocking nail. The implanted femurs were radiographed monthly until completion of the study 6 months after surgery. At the completion of the study, all foals were observed for evidence of lameness, gluteal thickness was determined by ultrasonographic 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 foal had postoperative infection but was healed radiographically in 5 months. 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 complication. Two foals were lame at the completion of the project; one foal with varus deformities of the contralateral limb was mechanically lame, and another was grade 2/5 lame on the operated limb. On necropsy, there was circumferential enlargement of the diaphysis of all operated limbs with the majority of the callus at the cranial and medial aspects of the cortex. All nails were solid within the medullary cavity.
Conclusions —The intramedullary interlocking nail provided adequate stabilization for repair of the transverse osteotomy.
Clinical Relevance —Further investigation is warranted before use for stabilization of spontaneously occurring fracture configurations.