Key Takeaways & Executive Findings
- •• Neck-shaft angle ≤ 127.6° and greater trochanter-diaphysis offset ratio > 0.52 are independent risk factors for coronal varus positioning of cementless femoral stems in total hip arthroplasty. • The combined prediction model using neck-shaft angle and greater trochanter-diaphysis offset ratio achieves superior predictive efficacy (AUC = 0.772) compared to single parameters. • Preoperative measurement of these anatomical parameters can guide prosthesis selection and surgical strategy to reduce the risk of varus stem placement. • The study introduces a novel parameter, greater trochanter-diaphysis offset ratio, expanding the assessment of proximal femoral morphology.
Abstract
BACKGROUND: Coronal prosthetic alignment of femoral stems significantly influences the prognosis of total hip arthroplasty. Currently, systematic analysis of the relationship between proximal femoral anatomical parameters and femoral stem prosthetic alignment remains insufficiently explored, and the quantitative impact of critical anatomical parameter thresholds on coronal varus implantation remains unelucidated. OBJECTIVE: To explore the effects of proximal femoral morphology and angular parameters on coronal varus alignment of uncemented femoral stems in total hip arthroplasty, determine predictive thresholds for key parameters, and construct a risk assessment model to provide clinical decision-making support for preoperative planning and surgical strategies of total hip arthroplasty. METHODS: Medical records of 276 cases undergoing primary total hip arthroplasty between January 2022 and December 2024 were retrospectively enrolled. Uncemented femoral stems were implanted via an anterolateral approach. Preoperative anatomical parameters of the affected proximal femur were measured: neck-shaft angle, femoral cortical index, canal flare index, and greater trochanter-diaphysis offset ratio. One month postoperatively, cases were divided into varus group (< -3°) and non-varus group (≥ -3°) based on the angle between the femoral stem axis and the femoral medullary canal axis. Univariate analysis, receiver operating characteristic curve, and multivariate logistic regression were used to evaluate the relationship between anatomical parameters and varus alignment. RESULTS AND CONCLUSION: A total of 139 patients were included, with 32 in the varus group and 107 in the non-varus group. Univariate analysis showed that the varus group had a smaller neck-shaft angle (P < 0.001) and a higher greater trochanter-diaphysis offset ratio (P < 0.001). Receiver operating characteristic curve analysis determined that neck-shaft angle ≤ 127.6° (area under the curve = 0.713) and greater trochanter-diaphysis offset ratio > 0.52 (area under the curve = 0.724) were predictive thresholds for varus. The combined prediction of neck-shaft angle and greater trochanter-diaphysis offset ratio yielded an area under the curve of 0.772, which was superior to either parameter alone. Multivariate logistic regression confirmed that neck-shaft angle ≤ 127.6° and greater trochanter-diaphysis offset ratio > 0.52 were independent risk factors. In conclusion, neck-shaft angle and greater trochanter-diaphysis offset ratio are independent risk factors for coronal varus alignment of cementless femoral stems in total hip arthroplasty, and their combined prediction model has higher predictive efficacy than single parameters. Preoperative precise measurement of neck-shaft angle and greater trochanter-diaphysis offset ratio can guide prosthesis selection, optimize femoral prosthesis alignment strategies, and reduce the risk of varus implantation.
1. Introduction
Total hip arthroplasty is an effective treatment for end-stage hip joint diseases and femoral neck fractures [1-3]. With the acceleration of population aging, its demand has significantly increased [4-6]. Studies have shown that the long-term efficacy of total hip arthroplasty depends not only on the patient's primary disease and postoperative complications [7-10], but also on the position of the prosthesis [11-13]. The position of the femoral stem directly affects the stability, stress distribution, and postoperative complications (such as periprosthetic fractures, aseptic loosening, etc.) [14-15]. Clinical studies have confirmed that coronal varus alignment of the femoral stem (> 3°) significantly increases the risk of loosening by altering stress distribution patterns [16-17].
Previous studies have shown that proximal femoral morphology, such as neck-shaft angle, femoral cortical index, and canal flare index, is significantly correlated with coronal alignment of the femoral stem [18-19]. However, current research still has limitations: first, systematic analysis of the relationship between proximal femoral morphology and femoral stem prosthetic alignment has not been fully conducted, and most studies focus on a single parameter; second, the quantitative impact of critical anatomical parameter thresholds on coronal varus implantation remains unclear.
This study retrospectively analyzed imaging data of patients undergoing total hip arthroplasty to explore the correlation between multiple proximal femoral parameters, namely neck-shaft angle, femoral cortical index, canal flare index, and the custom parameter greater trochanter-diaphysis offset ratio, with coronal varus alignment of cementless femoral stems. The greater trochanter-diaphysis offset ratio quantifies the spatial relationship between the base of the greater trochanter and the lateral femoral cortex, compensating for the lack of assessment of greater trochanter morphology in traditional parameters. The thresholds of these parameters affecting coronal varus alignment were determined, and a prediction model was established to evaluate the independent and combined predictive value of key anatomical parameters, providing clinical decision support for preoperative planning and surgical strategies of total hip arthroplasty.
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Song Yang, Yuan Liufeng, Guo Zheng, Shen Dahui, Sun Shoukang, Xu Xiangjun, Guo Dongsheng, Dong Yuefu (2026). Effect of proximal femoral morphology on coronal varus positioning of cementless femoral stems. Chinese Journal of Tissue Engineering Research. https://doi.org/10.12307/2026.21621
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Frequently Asked Questions
What are the independent risk factors for coronal varus positioning of cementless femoral stems in total hip arthroplasty?
The independent risk factors are neck-shaft angle ≤ 127.6° and greater trochanter-diaphysis offset ratio > 0.52, as confirmed by multivariate logistic regression.
How does the combined prediction model perform compared to single parameters?
The combined prediction model using neck-shaft angle and greater trochanter-diaphysis offset ratio achieves an area under the curve (AUC) of 0.772, which is superior to either parameter alone (AUC = 0.713 for neck-shaft angle and 0.724 for greater trochanter-diaphysis offset ratio).
What is the greater trochanter-diaphysis offset ratio?
The greater trochanter-diaphysis offset ratio is a novel imaging parameter introduced in this study to quantify the spatial relationship between the base of the greater trochanter and the lateral femoral cortex, providing additional assessment of proximal femoral morphology.
Why is coronal varus alignment of the femoral stem a concern in total hip arthroplasty?
Coronal varus alignment of the femoral stem (> 3°) alters stress distribution patterns, significantly increasing the risk of periprosthetic fractures, loosening, dislocation, wear, and pain, thereby compromising surgical outcomes and implant longevity.
How can preoperative measurement of these parameters guide clinical practice?
Precise preoperative measurement of neck-shaft angle and greater trochanter-diaphysis offset ratio can help surgeons select appropriate prostheses and optimize surgical strategies to minimize the risk of varus stem placement, moving toward data-driven personalized treatment.
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