Evidence of Reduced Muscle Trauma Through a Minimally Invasive Anterolateral Approach by Means of MRI

Background Minimally invasive techniques in THA are intended to minimize periarticular muscle trauma. The lateral approach has a risk of partial gluteal insufficiency, while the anterolateral approach carries the risk of damaging the tensor fasciae latae through intermuscular nerve and compression injury. Questions/purposes We assessed the surgical influence of the anterolateral minimally invasive approach and the modified direct lateral approach on the tensor fasciae latae and gluteus medius. Methods We prospectively randomized 44 patients with primary coxarthrosis to receive a cementless THA via the anterolateral minimally invasive approach or the modified direct lateral approach. We performed clinical and MRI examinations preoperatively and 3 and 12 months postoperatively, including Harris hip and pain scores. MRI analysis included assessment of the tensor fasciae latae and gluteus medius with regard to fatty atrophy and changes in the muscle cross-sectional area. Results Clinical scores were similar in the two groups but a low-grade Trendelenburg sign was observed more frequently in the lateral group. MRI showed a pronounced, postoperative fatty atrophy of the anterior part of the gluteus medius more often; and a compensatory hypertrophy of the tensor fasciae latae occurred. Higher-grade atrophy of the tensor fasciae latae and gluteus medius did not occur with the anterolateral approach. Conclusions We found no increased damage to the tensor fasciae latae with the anterolateral approach. The lateral approach was associated with increased partial gluteus atrophy and a compensatory hypertrophy of the tensor fasciae latae. Based on fewer structural changes in the musculature, we recommend the anterolateral minimally invasive approach.