gms | German Medical Science

Objectives: Malposition of the cup with uncovered anterolateral rim may induce significant damage to the iliopsoas tendon and cause consecutive pain. Conversely, early revision of a stable implant with only slight protrusion should be avoided. Iliopsoas (IP) tenotomy has demonstrated effectiveness in alleviating pain even in these cases. However, tenotomy at the lesser trochanter is known to promote higher levels of IP atrophy. Alternatively, tenotomy at the labral level may be performed. This study assesses the clinical outcome, the impact on hip flexion strength and the morphological changes of the IP muscle via magnetic resonance imaging (MRI) following labral-level tenotomy.

Methods: From 2013 to 2020, all patients who underwent arthroscopic labral-level IP tenotomy for tendinopathy post-hip arthroplasty with a minimum follow-up time of 12 months and willing to participate in the study were included. Pre- and post-operative cross-sectional areas of the iliopsoas muscle were measured at 2 different levels in the MRI. Muscle atrophy according to Goutallier, irregularities of the tendon, muscle edema and compensatory hypertrophy were assessed. Hip flexion strength was measured in seated and supine position using a dynamometer. Analysis was performed using Mann-Whitney U and Kruskal-Wallis tests.

Results: The study evaluated 22 patients, of whom 17 met the inclusion criteria. Median follow-up was 51 months (range 12 – 105). Post-operative MRIs revealed a reduction in iliopsoas cross-sectional area by 36% (±33.85%) at the anterior superior iliac spine (ASIS) and 31% (±30.02%) at the anterior inferior iliac spine (AIIS) as compared to the unaffected side. A similar decrease was observed when comparing pre- and post-operative MRIs of the affected side with a reduction of 34% (±27.53%) at the ASIS and of 25% (±15.69%) at the AIIS. Using the Goutallier classification, we observed atrophy (psoas/iliacus) at the following grades: grade 0 (1/4), grade 1 (6/7), grade 2 (9/5) and grade 3 (1/1). None of the observed cases were classified as grade 4. Examination of the hip flexion in seated and supine position did not show significant differences in strength between the affected and non-affected side with median differences of minus 12% and minus 18%, respectively. All patients reported a complete reduction in their symptoms and were satisfied with the procedure.

Conclusion: The study confirms that IP muscle atrophy occurs in most patients after IP tenotomy, on average reducing the cross-sectional area of the IP muscle by about one-third. Despite this reduction, hip flexion strength remains virtually unaffected. These findings align with existing research, highlighting the absence of severe atrophy after labral-level compared to lesser trochanteric tenotomies. In this study, all patients reported satisfaction after tenotomy.