1. Recovery in horizontal gait after hip resurfacing vs. total hip arthroplasty at 6-month follow-up – a RCT study Purpose To test the hypothesis that (i) a superior recovery in gait would be observed following resurfacing total hip arthroplasty (R-THA) compared to standard total hip arthroplasty (S- THA) and (ii) to investigate the hypothesized relationship between mechanical hip and knee muscle performance (MVC) and horizontal gait function in patients with total hip replacement Methods Forty-three patients were randomized into either S-THA or R-THA. Three-dimensional gait data were collected at self-selected normal and maximal walking speed. Primary outcome was gait speed while secondary outcomes comprised selected temporospatial and kinematic parameters obtained during horizontal walking. Explorative outcome was the relationship between hip and knee muscle strength (MVC) and horizontal gait function in THA patients. Data was collected pre-operatively, 8 and 26 weeks post-surgery. Results There was no effect of treatment on horizontal self-selected normal gait speed. However, an effect of treatment was observed on maximal walking speed where S-THA subjects walked faster than the R-THA subjects (P = 0.03, Fig.1). No differences in the recovery of temporospatial parameters were observed between treatment groups (Fig. 2). Also, peak hip flexion and peak hip adduction angles recorded during the stance phase were similar in both groups (Table 2). The explorative outcome analysis of the study showed that maximal isometric knee and hip muscle strength (MVC) were positively associated with gait speed, step length and cadence during maximal walking (R 2 = 0.13-0.37, P <.05) (Not-shown) Conclusion The present data could not provide evidence to support the hypothesis that resurfacing total hip arthroplasty should lead to a superior recovery in gait and hip kinematics compared to standard total hip arthroplasty in younger hip arthritis patients. Maximal isolated leg muscle strength was a predictor of horizontal gait performance, and thus provides an important and valid functional outcome measure for individuals undergoing total hip arthroplasty. TABLE 1: Baseline characteristics, mean (SD) C. Jensen 1, P. Aagaard 2, S. Overgaard 1 1 Orthopaedic Research Unit – Dept. of Orthopaedic Surgery and Traumatology, Odense, Denmark 2 Institute of Sports Science and Clinical Biomechanics, University of Southern Denmark, Odense, Denmark Background Standard total hip arthroplasty (S-THA) is the established surgical treatment for patients older than 65 years with progressive osteoarthritis. However, implant survivorship curves decline more rapidly in patients younger than 50 years. Resurfacing hip arthroplasty (R-THA) has therefore been suggested as an alternative for younger more active patients. Walking ability is one of the most common and useful outcome measures used in hip replacement patients, and the ability to safely ambulate is considered a prerequisite for discharge from most orthopedic facilities. Improvements in walking ability and kinematics have been suggested after hip resurfacing, but no study has objectively assessed this aspect in a randomized clinical trial. Characteristic S-THA (n = 19) R-THA (n=18) Age at surgery, yrs55 (6.2)57 (5.1) Gender, F:M3:167:11 Operated, L:R13:611:7 Leg length, m.86 (.03).88 (.06) Follow-up, weeks8.7 (1.0)8.2 (1.0) Follow-up, weeks24.5 (1.4)24.4 (0.8) FIGURE 1: Gait speed self-selected normal (A) and maximal (B) walking speed, mean ± 95% C.I. TABLE 2: Kinematic gait parameters during the stance phase at self-selected normal speed, mean (SD) Gait parameterSideTreatment Time Pre-surgery8 wks post-surgery26 wks post-surgery Peak Hip Flexsion [deg] Operated R-THA31 (6.4)33 (5.5)34 (4.8) S-THA31 (6.3)33 (6.5)34 (6.9) Non-operated R-THA36 (6.0)36 (6.7)36 (5.5) S-THA33 (5.5)36 (6.8)35 (5.7) Peak Hip Adduction [deg] Operated R-THA6 (3.5)5 (3.8)5 (2.5) S-THA9 (4.1)7 (3.4)8 (4.0) Non-operated R-THA7 (4.4)6 (5.8)7 (3.6) S-THA9 (4.0)9 (4.6) No significant difference between groups at any time points No significant difference between groups FIGURE 2: Temporospatial gait parameters at self-selected normal walking speed, mean ± 95% C.I.