Could the tendon degeneration and the fatty infiltration of the gluteus medius affect clinical outcome in total hip arthroplasty?

Purpose The aim of this prospective study was to perform a clinical and radiologic evaluation of patients undergoing total hip arthroplasty (THA). The hypothesis is that there is a correlation between the pre-operative degeneration state of the gluteal muscle-tendinous unit and the clinical outcome in terms of functional recovery. Methods Fifty-five patients have met inclusion criteria. All patients included in the sample were subjected to clinical evaluation. The ultrasound examination of the patients of the study was conducted and the following parameters were assessed: Thickness in mm of the gluteus medius tendon; Quality of the gluteus medius tendon; and Trophy and muscular composition. Results The degree of degeneration of the pre-operative tendon shows a negative statistical correlation with all the pre- and post-operative clinical scales, but presents statistical significance (p < 0.05) only with the post-operative Harris, the post-operative Oxford, the Harris and HOOS-modified post-operative, lameness, and Trendelenburg; it correlates positively with the quality of the macroscopic tendon detected intra-operatively, the degree of the pre-operative contralateral tendon, and the operated and contralateral pre-operative muscle (p < 0.05). The degree of fatty degeneration of the pre-operatively operated muscle correlates negatively (p < 0.05) with all pre- and post-operative clinical scales except for the pre-operative WOMAC and HOOS modified, with the lameness and the Trendelenburg sign; it correlates positively (p < 0.05) with age, the quality of the macroscopic tendon detected intra-operatively, degree of tendon degeneration, fatty infiltration of the contralateral pre- and post-operative muscle and of the post-operative operated muscle. Conclusion Tendon degeneration and fatty infiltration of the gluteus medius muscle appeared to be determinants of the post-operative persistence of lameness and Trendelenburg sign positivity in patients undergoing hip arthroplasty.