Iliopsoas impingement after total hip arthroplasty: Does the CT-scan have any role? Our Algorithm proposal

Introduction: The first surgical option considered in managing iliopsoas impingement following THA is endo-scopic/arthroscopic iliopsoas tenotomy, because of its low risk and minimal invasiveness. Acetabular revision is a much more aggressive surgery, recommended only in cases of substantial cup malposition. However, there are no clear indications for this procedure. The purpose of this article is to analyse the role of CT-scan measurement of acetabular cup positioning in a therapeutic algorithm for iliopsoas impingement. Methods: In this retrospective observational study, we reviewed 25 patients treated for iliopsoas impingement following THA between 2011 and 2019. We studied acetabular cup positioning using CT-scan. We compared radiological parameters of patients who presented with significant clinical improvement with conservative treatment and with tenotomy against those who did not. Finally, we developed a proposed therapeutic algorithm. Results: Forty-eight percent of patients presented a significant clinical improvement following conservative treatment. Patients who did not improve were found to have greater acetabular cup axial and sagittal overhang (p-values 0.016 and 0.003). These patients were considered for tenotomy. Of this group, those who did not improve with surgery (38%) showed greater axial overhang (p-value 0.005). Conclusions: Conservative management should be the first line of treatment. In cases of non-operative treatment failure, axial acetabular cup overhang measured by CT-scan can be a useful tool in choosing between iliopsoas tenotomy or cup-revision surgery in selected cases of very severe acetabular malposition. A cut-off point of 10 mm of axial overhang is a reliable predictor of higher failure risk with iliopsoas tenotomy.