Resection Guide For the ARC™ Tissue Conserving (Neck Sparing) Total Hip Stem - Case Report

Abstract

Neck sparing total hip designs have been advocated as the next step in tissue preserving total hip arthroplasty1,2,3. In the proximal femur, the femoral neck and the adjoining medial aspect of the femur in the calcar region show the strongest bone structure (Fig. 1) with a high load capacity to support the stem. There are considerable short-term biomechanical advantages concerning reduced bending and torsional moments of the femoral implant/bone interface4 with resection at that level, however, historical review has demonstrated less than desirable bone maintenance over time5. According to Wolff’s Law, the reduction of stresses relative to the pre-implant anatomy would cause bone to adapt itself by reducing its mass, either by becoming more porous (internal remodeling) or by getting thinner (external remodeling)7. The ARC™Neck Sparing stem has a novel internal conical flair that engages the medial calcar and is designed to offload compressive loads maintaining a positive stress transfer to the medial calcar6. The combination of neck resection level and angle are important considerations for neck preserving stem designs. This case report demonstrates a new resection guide that has proven to be simple and reliable. Key Words: femoral neck, stress transfer, resection guide, conical flair