TRANSVERSE PLANE EVALUATION OF THE EFFECTS OF SURGICAL TECHNIQUE ON STEM POSITIONING AND GEOMETRY OF RECONSTRUCTION IN CANINE TOTAL HIP-REPLACEMENT

Objectives-To test whether femoral ostectomy level, subtrochanteric bo ne mass removal, and stem-size selection significantly affect stem pos itioning in canine total hip replacement, and to determine ability of the femoral stem component to restore geometry of the normal femoral h ead and neck. Sample population-Femurs from 8 adult mixed-breed canine cadavers. Procedure-Femurs were systematically prepared, using 8 comb inations of 3 surgical preparation techniques that included level of o stectomy (cervical isthmus vs lesser trochanter), subtrochanteric bone block removal, and femoral stem size (recommended, undersized). Compu ter-aided analysis of specimen photographs was used to evaluate femora l head offset and position and variability of femoral stem positioning for each of the preparation combinations. Results-Original femoral he ad offset and position were reconstructed to within a mean of 0.052 an d 0.031 cm, respectively, using an undersized femoral stem after ostec tomy at the level of the lesser trochanter. Implantation of an undersi zed femoral stem after subtrochanteric bone block removal improved abi lity to centralize the distal tip of the implant and reduce the angle between the femoral diaphyseal and implant axes. Ostectomy at the leve l of the cervical isthmus tended to force femoral implants into a varu s position, and ostectomy at the level of the lesser trochanter tended to force implants into a valgus position. Conclusions-Geometry of nor mal canine femurs was most closely reconstructed by implantation of an undersized femoral component after ostectomy at the revel of the less er trochanter. Implantation of an undersized femoral component after s ubtrochanteric bone block removal resulted in the best alignment and c entralization of the stem.