Minimally invasive primary THA: anterolateral intermuscular approach versus lateral transmuscular approach

Currently, several potential advantages lead to minimally invasive total hip arthroplasty which become popular with orthopaedic community. However, there is little comparative study on minimally invasive techniques especially through anterior approach. This investigation aimed to evaluate the efficacy of minimally invasive modified Watson-Jones approach and to compare short-term clinical results with minimally invasive modified Hardinge approach.

A consecutive series of 92 patients managed with minimally invasive total hip arthroplasty (47 with use of a modified Watson-Jones approach and 45 with use of a modified Hardinge approach) by one surgeon at one hospital were studied. All patients received the same design of cementless acetabular cup and femoral component. Data analysis included patient demographics, pre-operative diagnosis, surgical duration, intra-operative blood loss, type of anesthesia and length of hospital stay. Radiographic analysis included cup inclination angle, femoral stem alignment and leg length discrepancy.

No significant differences were noticed with regard to the average surgical time, intra-operative blood loss and length of hospital stay in both groups. The average femoral component alignment and the average post-operative abduction angle of the acetabular cup were in acceptable ranges in both groups. However, the prevalence of femoral stem varus outlier was significantly high in minimally invasive modified Watson-Jones approach group.

The higher prevalence of varus stem outlier in minimally invasive modified Watson-Jones approach must be considered to minimize femoral stem malalignment.