What question did this study set out to answer?

The study aims to explore how proximal femoral anatomy affects varus alignment of femoral stems in total hip arthroplasty and establish predictive thresholds.

February 28, 2026Journal of Medical and Biological Engineering0 citationsOpen Access

Risk Stratification for Varus Stem Positioning in Cementless THA: A Dual-Parameter Diagnostic Tool Based on Proximal Femoral Morphology

YSYang SongXuzhou Medical College LYLiufeng YuanXuzhou Medical College ZGZheng GuoXuzhou Medical College

Key Points

The study aims to explore how proximal femoral anatomy affects varus alignment of femoral stems in total hip arthroplasty and establish predictive thresholds.
Conducted a retrospective analysis of 315 primary THA cases from 2022 to 2024
Measured Neck-Shaft Angle, Femoral Cortical Index, Canal Flare Index, and Trochanteric-Diaphyseal Offset Ratio using preoperative pelvic radiographs
Categorized postoperative stem alignment as varus or non-varus based on stem-canal axis angle
22.01% of patients exhibited varus alignment after surgery
The varus group had a significantly smaller Neck-Shaft Angle compared to the non-varus group (127.10 ± 1.48 vs. 128.07 ± 1.17)
ROC analysis identified NSA ≤ 127.85° and TDOR > 0.53 as predictive thresholds with AUCs of 0.700 and 0.699, respectively
Combined use of NSA and TDOR achieved a higher AUC of 0.771
Both parameters were confirmed as independent risk factors for varus alignment with ORs of 4.725 and 4.468, respectively

Abstract

Abstract Purpose This study aimed to investigate the influence of proximal femoral anatomical parameters on coronal varus alignment of cementless femoral stems in total hip arthroplasty (THA) and to determine predictive thresholds. Methods A retrospective analysis of 315 primary THA cases (2022–2024) receiving a cementless stem (Polarstem) via an anterolateral approach was conducted. Preoperative pelvic radiographs were used to measure the Neck-Shaft Angle (NSA), Femoral Cortical Index (FCI), Canal Flare Index (CFI), and Trochanteric-Diaphyseal Offset Ratio (TDOR). Postoperative stem alignment was categorized as varus ( 0.53 (AUC = 0.699) as predictive thresholds. Their combination achieved a higher AUC of 0.771. Multivariate logistic regression confirmed NSA ≤ 127.85° (OR = 4.725) and TDOR > 0.53 (OR = 4.468) as independent risk factors for varus alignment (both P 0.05). Conclusion NSA (≤ 127.85°) and TDOR (> 0.53) are independent risk factors for coronal varus alignment in cementless THA. Their combined use provides superior predictive performance compared to either parameter alone.

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