MRI assessment of muscle damage after the posterolateral versus direct anterior approach for THA (POLADA trial). A randomized controlled trial

Abstract Background There is controversy in literature whether the direct anterior approach (DAA) results in less muscle damage compared to the posterolateral approach (PLA) for total hip arthroplasty. The aim of this randomized controlled trial was to assess muscle damage between these two approaches. Methods Forty-six patients were included. Muscle atrophy, determined with the Goutallier classification, and muscle surface of twelve muscles were analysed on MRI images made preoperatively and one year postoperatively. Differences in component placement following DAA or PLA were assessed on radiographs. Harris Hip Scores and Hip disability and Osteoarthritis and Outcome Score were used as functional outcomes. Results External rotator musculature was damaged in both approaches. Following PLA, the obturator muscles showed significantly more atrophy and a decrease in muscle surface. After DAA, the tensor fascia latae (TFL) showed an increased muscle atrophy and the psoas muscle showed a decreased muscle surface. An increase in muscle surface was seen for the rectus femoris, sartorius and quadratus femoris following both approaches. The muscle surface of the gluteus medius and iliacus were also increased following PLA. No difference in muscle atrophy was found between the approaches for these muscles. The inclination angle of the cup in PLA was significantly higher. No differences were found in functional outcomes. Conclusions Different muscle groups were affected in the two approaches. Following PLA the external rotators were more affected, whereas the TFL and psoas muscles were more affected after DAA.