Comparing the express and enhanced workflows for restoration of hip length and combined offset using the Mako robotic arm-assisted total hip arthroplasty

Aims: The Mako system is one of the most widely used systems for robotic arm-assisted total hip arthroplasty (THA). Two workflows for femoral preparation exists for this system - the enhanced and the express workflow. Methods: We performed a retrospective cohort study comparing the accuracy of each workflow in restoring the patient's combined offset and correcting the hip length discrepancy. The Mako derived values were compared against measured values and assessed with Bland-Altman plots and Theil's median slope. Secondary outcomes of interest included comparison of the measured combined offset and hip length discrepancy, surgical time, incidence of postoperative instability/dislocation, as well as pin-site related complications between the two groups. Results: A total of 81 patients were identified from our database: 61 in the enhanced group and 20 in the express workflow group. Bland-Altman plots demonstrated agreement between the measurements for both hip length discrepancy and combined offset. There was no significant difference in the measurement of hip length discrepancy or combined offset difference between the two groups; however, the magnitude of the latter was better in the enhanced (median 1.50 mm) compared with the express workflow group (median 3.13 mm). There was no significant difference in measured combined offset (p = 0.254), hip length discrepancy (p = 0.425), or surgical time (p = 0.548). Lastly, there were no patients with postoperative instability/dislocation nor pin-site related complications in either group. Conclusion: Both techniques provide excellent outcomes with minimal risk of complications when performing a Mako robotic arm-assisted THA.