Abstract
BACKGROUND: Conversion total hip arthroplasty (cTHA) after prior proximal femoral fracture fixation can be performed using different femoral stems. This study aimed to (1) determine if initial fracture fixation or pattern associated with stem design in cTHA, (2) evaluate whether stem type was associated with survivorship and outcomes, and (3) propose a radiographic measurement to guide femoral stem selection. METHODS: We retrospectively reviewed 51 patients who underwent cTHA from 2016 to 2020, including 44 patients with previous cephalomedullary nail (CMN; 86.3%) and 9 patients with previous sliding hip screw (SHS; 13.7%). Stems included 32 uncemented diaphyseal-engaging (62.7%), 10 uncemented metaphyseal-engaging (19.6%), and 9 cemented (17.6%). Outcomes assessed were fracture pattern, fixation construct, stem type, survivorship, post-operative complications, and patient-reported outcome measures. Preoperative radiographs were evaluated for diaphyseal width (D), distance from greater trochanter to most distal pre-isthmic screw (GS), and ratio of GS/D (GSD). These measures were used to construct an algorithm for stem selection at the time of cTHA. Mean follow-up was 69 months. Survivorship free from stem-related and all-cause failure was calculated using Kaplan-Meier analysis. RESULTS: Diaphyseal-engaging uncemented stems were used more often after CMN fixation, while metaphyseal-engaging uncemented stems predominated after SHS fixation. Diaphyseal-engaging stems predominated in previous intertrochanteric, subtrochanteric, or complex fractures, while metaphyseal-engaging uncemented stems were more common in femoral neck fractures. Survivorship free from stem-related failure was 100% and from all-cause reoperation was 89%. Patients who received cemented stems were older, more likely to require transfusion or prolonged use of an assistive walking device. No significant differences were observed in complications, clinical outcomes or PROMs between stem groups. Higher GSD ratios correlated with diaphyseal-engaging stem use in SHS and long-CMN cases. CONCLUSION: Femoral stem fixation type in cTHA correlated with prior fracture pattern and fixation construct. Survivorship free from stem-related failure requiring stem revision was 100% and survivorship free from all-cause failure was 89%. We propose a novel algorithm that may assist surgeons in selecting femoral stem at the time of cTHA using different patient-specific and radiographic factors.