A Biomechanical Investigation of Implant Alignment and Femoral Neck Notching With the Birmingham Mid-Head Resection

Abstract

The Birmingham Mid-Head Resection (BMHR) is a bone-conserving, short-stem alternative to hip resurfacing for patients with compromised femoral head anatomy. The current study examined the effect of coronal implant alignment and femoral neck notching on proximal femoral strength with the BMHR. Neither relative valgus nor varus implant alignment had a significant impact on femoral strength compared to neutrally aligned, matched, paired cadaveric specimens. A 5-mm superior neck notch significantly weakened BMHR-implanted synthetic femurs compared to unnotched controls, whereas a 2-mm notch did not significantly affect ultimate failure load. Relative valgus alignment had a protective effect on a full-cortical-thickness superior neck notch. Mid-head resection arthroplasty may be more forgiving to minor preparatory errors than a typical hip resurfacing.