Immediate Post-Operative Advantages of Minimally Invasive Hip Replacement - Results of Symmetry and Load from the Measurement of Ground Reaction Force

Aim: The purpose of this clinical study is to evaluate the postoperative walking ability after total hip replacement (THR) in terms of different surgical approaches by means of an evaluation of gait velocity. Methods: 21 patients underwent a total hip replacement using an anterolateral minimally invasive modified Watson-Jones approach (MIS group). 20 other patients received a THR using a transgluteal approach (standard group). Differences in functional indices of ground reaction forces and symmetry indices were measured one day pre-operatively, and at 6 and 13 weeks post-operatively on the walkway. The intervention of gait velocity was done by means of a digital metronome. The given step frequences were 70, 90 and 110 steps/minute. The results were compared to an age-matched control group (n = 20). Results: There are significantly reduced pain symptoms in both surgical groups at 6 weeks post-operatively. The MIS group has a higher functional ability, improved symmetry indices of stance time, loading rate and single limb stance compared to the control group at 6 weeks postoperatively. At 13 weeks postoperatively there are no differences between the two surgical groups, except for the parameter "loading rate". The patients in the MIS group had an increasing improvement already at 6 weeks after THR. From 6 to 13 weeks after surgery there were important changes in the control group, Conclusion: Obviously, the early postoperative advantages of the minimal invasive approach provide for an improved re-establishment of symmetry and load. In this clinical course study, the proof is validated because the trends in the biomechanical gait parameters are comparable by means of gait velocity standardisation.