Purpose: The purpose of the present study was to evaluate the MRI of the hip musculature as well as specific blood parameters on comparison of the Bauer approach with the minimally invasive ALMI approach.
Material and methods: We compared two patient groups after total hip replacement, which were operated either via the Bauer or the ALMI approach. All 47 patients had the same cementless hip design. All surgeries were performed by two experienced hip surgeons with experience of more than 1200 ALMI approaches. The patient groups did not differ concerning age, sex or side which was operated on. All MRI were performed in a standardised technique with a Philips Outlook Proview (0.23 Tesla). Patients were scanned preoperatively, within 2 weeks after surgery and at time of follow-up 14 months after surgery. The evaluation of the MRI findings was performed by two independent and blinded examiners. In order to document the muscle damage we documented myoglobin (the day before surgery, 6 hours postoperatively and at the first postop. day) und troponin (6 hours postoperatively).
Results: Preoperatively the male patients showed a significantly larger diameter of the gluteus medius muscle. We also could demonstrate in many patients a fatty degeneration even before surgery. At time of follow-up there was no significant difference between the two patient populations concerning the fatty degeneration. There was also no significant difference concerning the muscle atrophy. Muscle oedema, that was present before surgery, however, was no longer present at the time of follow-up. Two patients even preoperatively showed a lesion of the gluteus medius tendon. The range of the postoperative myoglobin level was high (118-5411 µg/L), in the ALMI group the standard deviation was 1445 µg/L, in the Bauer group it was 738 µg/L. There was no significant difference between both groups. Similar findings were documented for the troponin levels.
Conclusion and clinical relevance: Even before THR many patients show significant degeneration in the hip muscles. Muscle oedema that was present before surgery had disappeared at the time of follow-up. The fatty degeneration was still present at the time of follow-up. There was no difference concerning the muscle atrophy between the ALMI and the Bauer groups.
Georg Thieme Verlag KG Stuttgart · New York.