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Factors affecting the potential for posterior bony impingement after total hip arthroplasty
T Shoji1, T Yamasaki1, S Izumi1
1Graduate School of Biomedical Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8551, Japan.
Insights
Posterior bony impingement after total hip arthroplasty (THA) is linked to wider ischium and narrow ischiofemoral space. High femoral offset and posterior pelvic tilt are also identified risk factors.
Area of Science:
- Orthopedic surgery
- Radiology
- Biomechanical analysis
Background:
- Posterior bony impingement can occur after total hip arthroplasty (THA).
- Understanding radiographic predictors is crucial for preventing impingement.
- CT simulations offer a method to evaluate bony structures preoperatively.
Purpose of the Study:
- To assess radiographic characteristics associated with posterior bony impingement in THA patients.
- To investigate the influence of pelvic tilt, femoral offset, and other parameters on impingement.
Main Methods:
- Analysis of virtual CT data from 112 THA patients.
- Evaluation of associations between radiographic features and posterior bony impingement.
- Investigation of external rotation range, pelvic tilt, and femoral component parameters.
Main Results:
- Patients with posterior bony impingement had lower external rotation and ischiofemoral length.
- Higher femoral anteversion, ischial ratio, and ischial angle were observed in impingement cases.
- Posterior pelvic tilt and high femoral offset correlated with reduced external rotation due to impingement.
Conclusions:
- Wider ischium and narrow ischiofemoral space increase the likelihood of posterior bony impingement post-THA.
- High femoral offset and posterior pelvic tilt are identified risk factors.
- Radiographic assessment can help identify patients at risk for posterior bony impingement.
Aims:
Our aim was to evaluate the radiographic characteristics of patients undergoing total hip arthroplasty (THA) for the potential of posterior bony impingement using CT simulations.
Patients And Methods:
Virtual CT data from 112 patients who underwent THA were analysed. There were 40 men and 72 women. Their mean age was 59.1 years (41 to 76). Associations between radiographic characteristics and posterior bony impingement and the range of external rotation of the hip were evaluated. In addition, we investigated the effects of pelvic tilt and the neck/shaft angle and femoral offset on posterior bony impingement.
Results:
The range of external rotation and the ischiofemoral length were significantly lower, while femoral anteversion, the ischial ratio, and ischial angle were significantly higher in patients with posterior bony impingement compared with those who had implant impingement (p < 0.05). The range of external rotation positively correlated with ischiofemoral length (r = 0.49, p < 0.05), and negatively correlated with ischial length (r = -0.49, p < 0.05), ischial ratio (r =- 0.49, p < 0.05) and ischial angle (r = -0.55, p < 0.05). The range of external rotation was lower in patients with posterior pelvic tilt (p < 0.05) and in those with a high offset femoral component (p < 0.05) due to posterior bony impingement.
Conclusion:
Posterior bony impingement after THA is more likely in patients with a wider ischium and a narrow ischiofemoral space. A high femoral offset and posterior pelvic tilt are also risk factors for this type of impingement. Cite this article: Bone Joint J 2017;99-B:1140-6.
