Does Automated Impaction Improve Femoral Component Sizing and Alignment in Total Hip Arthroplasty?

Abstract

Background: While automated impaction can provide a more standardized process for femoral canal preparation, little is known regarding its effect on femoral component sizing and position. The purpose of our study was to directly compare femoral component canal fill ratio (CFR) and coronal alignment between primary total hip arthroplasty (THA) procedures performed with automated impaction versus manual mallet impaction.

Methods: A retrospective analysis was performed on 184 patients who underwent primary THA by a single arthroplasty surgeon between 2017 and 2021 with a modern cementless femoral component using either the direct anterior or posterolateral approach. The final cohort was divided into 2 groups based on impaction technique during broaching: automated (N = 122) or manual (N = 62). A propensity score match was used to match for age, body mass index, sex, high versus standard offset stem, and preoperative femoral bone quality. Radiographic review was performed to measure intramedullary prosthetic CFR and coronal alignment.

Results: The automated cohort trended toward the use of a larger stem (5.67 versus 4.82, P = .006) and had a larger CFR at all 4 levels within the proximal femur (P = .004). The automated cohort had a more valgus and reliable coronal alignment (-0.57 (SD 1.50) versus -0.03 (SD 2.17) degrees, P = .03) and significantly shorter operative time (mean 78 versus 90 minutes, P < .001). There were no intraoperative or postoperative periprosthetic fractures in either cohort.

Conclusion: Automated impaction in primary THA is a safe technique for femoral preparation, which resulted in improved stem coronal alignment, optimized canal fill within the proximal femur, and reduced operative times.

Keywords: THA; automated impaction; canal fill ratio; component alignment; total hip arthroplasty.