Component Placement in Direct Lateral vs Minimally Invasive Anterior Approach in Total Hip Arthroplasty: Radiographic Outcomes From a Prospective Randomized Controlled Trial.

Background: End-stage coxarthrosis is increasingly common; however, limited evidence exists on the effect of direct lateral approach (DLA) and minimally invasive direct anterior approach (MIDA) on component placement in total hip arthroplasty (THA). We therefore conducted a prospective, randomized controlled trial to determine the component placement in DLA vs MIDA in THA.

Methods: Between January 2012 and June 2013, 164 patients with clinically and radiologically confirmed coxarthrosis aged 20-80 years were randomized to either DLA or MIDA (active comparator). Excluded were patients with previous ipsilateral hip surgery, a body mass index >35 kg/m, and/or mental disability. Primary clinical outcomes have been published elsewhere. Secondary outcomes included radiographic assessment of the acetabular component (cement-mantle thickness, inclination, and anteversion), femoral stem position (varus/valgus and THA index), offset restoration, and leg length discrepancy.

Results: The mean cement-mantle was significantly thicker in zone 1 in the MIDA group (mean difference = 0.51 mm, 95% confidence interval [CI] 0.09-0.93, P = .018), and the mean degrees of inclination and anteversion were higher in the MIDA group (mean difference = 2.5°, 95% CI 0.3-4.6, P = .023 and mean difference = 3.6°, 95% CI 2.2-5.0, P < .0001, respectively). According to the defined reference range, cup inclination was more often adequate in the DLA group (67.9% (53/78) in the DLA group vs 52.4% (43/82) in the MIDA group, P = .045). There were no differences in frontal or lateral femoral stem position, global offset restoration, or leg length discrepancy.

Conclusion: In this population of Norwegian patients with coxarthrosis, radiographic assessment showed limited differences in component placement between MIDA and DLA. The findings suggest that component placement is similar in the 2 surgical approaches.