Femoral stem subsidence after uncemented total or hemiarthroplasty for femoral neck fractures does not correlate with local femoral bone quality evaluated by Dorr and cortical thickness index

Abstract

Introduction

The increase in femoral neck fractures in elderly individuals is primarily attributable to reduced bone mineral density (BMD). Dual-energy X-ray absorptiometry (DEXA), has been demonstrated to be a reliable bone mineral density (BMD) estimate. Femoral cortical thickness index (CTI), and Dorr classification are reliable assessment methods of the femoral cortical thickness. Patients with low BMD, low CTI or Dorr C who undergo uncemented total hip arthroplasty (THA) or hemiarthroplasty (HA) are at an increased risk of early femoral stem subsidence (FSS). Dual-energy X-ray absorptiometry (DEXA), femoral cortical thickness index (CTI), and Dorr classification have been demonstrated to be reliable bone mineral density (BMD) estimates. Patients with low BMD who undergo uncemented total hip arthroplasty (THA) or hemiarthroplasty (HA) are at an increased risk of early femoral stem subsidence (FSS). The objective of this study was to investigate the relationship between CTI, Dorr classification, and early FSS, hypothesizing that these indicators can predict stem subsidence.

Material and methods

A retrospective analysis was conducted on patients with femoral neck fractures treated by uncemented THA or HA using the direct anterior approach (DAA). Preoperative radiographs were utilized to assess CTI and Dorr classification. Postoperative FSS was the primary outcome measure, with follow-up X-rays averaging 403 days (range 38–3371). The canal fill ratio (CFR) was observed at four levels postoperatively. A subsequent statistical analysis was conducted to examine the correlation between CTI, Dorr classification, CFR, BMI, age, and FSS.

Results

The study’s sample population included 64 patients (20 male, 44 female) with a mean age of 73 ± 9 years, who were treated between June 2020 and February 2024. The mean femoral CTI was 0.51 ± 0.08 on the fractured side and 0.54 ± 0.06 on the contralateral unaffected side. The mean FSS was 1.02 ± 1.49 mm. A subsidence of at least 5 mm was identified in a mere two patients, both of whom were classified as Dorr B. A modest correlation (r = 0.27) was noted between FSS and CRF 2.

Conclusion

Neither decreased BMD nor cortical thickness correlated with femoral stem subsidence.

Level of evidence

Level III, Therapeutic study.