Abstract
Background
Hip resurfacing arthroplasty (HRA) and total hip arthroplasty (THA) are treatments of end-stage hip disease. Gait analysis studies comparing HRA and THA have demonstrated HRA results in a more normal gait than THA. The reasons may include the larger, more anatomic head diameter, the preservation of the femoral neck with restoration of the anatomical hip centre position and normal proprioception. This study investigated (1)whether femoral head size diameter affects gait; (2)whether gait still differs between THA and HRA patients even with comparable head diameters.
Methods
We analysed the gait of 33 controls and 50 patients with unilateral hip replacement. Follow-up ranged from 9–68 months. In 27 hips a small femoral head size was used (≤ 36mm); in 23 hips a large head size (>36mm). The small size group consisted of 11 long femoral stem THA and 16 short-stem THA; the large group of 5 long-stem, 8 short-stem THA and 10 HRA patients. There were 14 females/19 males in the control group; 22 females/5 males in the small size group; 13 females/10 males in the large size group.
Results
(1) We found a significant difference in step-length between small head sizes and controls (p<0.01) at speeds ranging from 4.0 to 5.5 km/h but no difference between the larger head size and the controls. There was no significant difference in maximum speed, weight acceptance, push-off, mid-stance, impulse and cadence between the groups. (2)Analysis between THA and HRA in the large head size group revealed a significant difference in maximum speed (p=0.021) between long-stem THA (6.338 km/h± 1.542) and HRA (7.756km/h± 0.7604) patients. At 5.5 km/h there was a significantly better weight acceptance (p=0.009) and mid-stance (p=0.041) of HRA compared to short-stems. Impulse was significantly higher for HRA compared to long-stem THA (p<0.05) at all speeds ranging 4 to 5.5 km/h. (3)Males (7.1972 km/h ± .9700) had significantly higher maximum speeds compared to females (6.6524km/h± 1.019) (p=0.017) and lower gait impulse (p<0.01) at speeds ranging from 4 to 5.5km/h. (4)There was no significant difference in Oxford Hip Score (OHS) and EQ-5D of patients in the small compared to large head size group.
Conclusions
Gait analysis demonstrated a significant difference in step length between THA patients with head size ≤ 36mm and normal controls. There was no difference in step length between normal controls and THA patients with larger head sizes. Compared to larger head size THA, HRA still revealed higher maximum speeds and better weight acceptance. Males had significantly higher maximum speeds compared to females (controls and hip replacement patients). We could not demonstrate a correlation between better gait and Oxford scores or EQ-5D scores but these are known to have a ceiling effect. In a former study, better gait parameters such as longer step length and higher maximum speed have been associated with higher patient satisfaction
