The gait of patients with one resurfacing and one replacement hip: a single blinded controlled study.

PURPOSES: Post arthroplasty gait analysis has up till now been performed on subjects walking slowly on flat ground rather than challenging them at faster speeds or walking uphill. We therefore asked: (1) Is there a measurable difference in the performance of hip resurfacing arthroplasty (HRA) and total hip arthroplasty (THA) limbs at patients' self-determined fastest walking speeds and steepest inclines? and (2) Is there a relationship between the observed differences between the gait of HRA and THA implanted limbs and patient walking speeds and inclines.
METHODS: In an ethically approved study we recruited patients with bilateral hip arthroplasties: one HRA and one THA. Nine subjects were assessed using an instrumented treadmill at a range of speeds and inclines by a blinded observer. The ground reaction forces of subjects were recorded and an age, sex and BMI matched control group was used for comparison.
RESULTS: Increasing walking speed correlated strongly with between leg differences in weight acceptance (r = 0.9, p = 0.000) and push-off force (r = 0.79, p = 0.002). HRA implanted limbs accepted significantly more weight at top walking speeds (1208 N ± 320 versus 1279 N ± 370, p = 0.026) and pushed off with greater force when walking uphill (818 N ± 163 versus 855 ± 166, p = 0.012). HRA limbs more closely approximated to the gait of the normal control group.
CONCLUSIONS: Arthroplasty implants do have an impact on the gait characteristics of patients. Differences in gait are more likely to be evident when assessment is made at fast speeds and walking uphill. This study suggests that HRA may enable a more normal gait.