Does acetabular retroversion affect range of motion after total hip arthroplasty?

Background: Increasingly, acetabular retroversion is recognized in patients undergoing hip arthroplasty. Although prosthetic component positioning is not determined solely by native acetabular anatomy, acetabular retroversion presents a dilemma for component positioning if the surgeon implants the device in the anatomic position. Questions/purposes: We asked (1) whether there is a difference in ROM between surface replacement arthroplasty (SRA) and THA in the retroverted acetabulum, and (2) does increased femoral anteversion improve ROM in the retroverted acetabulum? Methods: Using a motion analysis tracking system, we determined the ROM of eight cadaveric hips and then created virtual CT-reconstructed bone models of each specimen. ROM was determined with THA and SRA systems virtually implanted with (1) the acetabular component placed in 45° abduction and matching the acetabular anteversion (average 23° ± 4°); (2) virtually retroverting the bony acetabulum 10°; and (3) after anteverting the THA femoral stem 10°. Results: SRA resulted in ROM deficiencies in four of six maneuvers, averaging 25% to 29% in the normal and retroverted acetabular positions. THA restored ROM in all six positions in the normal acetabulum and in four of the six retroverted acetabula. The two deficient positions averaged 5% deficiency. THA with increased femoral stem anteversion restored ROM in five positions and showed only a 2% deficiency in the sixth position. Compared with the intact hip, ROM deficits were seen after SRA in the normal and retroverted acetabular positions and to a lesser extent for THA which can be improved with increased femoral stem anteversion. Conclusion: Poor ROM may result after SRA if acetabular retroversion is present.