Introduction: By means of gait analysis and EMG measurements, we evaluated the difference between short and conventional hip stems in patients who underwent hip replacement for osteoarthritis. The remaining gait differences after hip replacements are well documented and caused by many factors, among which offset restoration is an important factor. Based on the theory that short stems are more capable of restoring offset, we compared gait between short stems and conventional stems. Methods: Two groups of ten patients were selected from ongoing trials and were case matched. For all patients, a detailed gait and EMG measurement was performed using the GRAIL (Gait Real-time Analysis Interactive lab, Motek ForceLink BV, Netherlands) system. Our primary outcome measurement was the peak hip abduction moment (HAM). Other gait parameters, muscular activity and the hip disability and osteoarthritis outcome score (HOOS) were secondary outcome measurements. Results: The peak HAM for the short stems was 1.29 Nm/kg (0.27) compared to 1.14 Nm/kg (0.32) for the conventional stem group (not significant). The short-stem group further showed longer step and stride length. Gluteus medius activation needed to stabilize the trunk and walking speed did not reach significance. The HOOS was better in the short-stem group. Conclusion: The results of our pilot study support the belief that a short stem can result in better outcomes, as measured by gait and EMG analysis.

Background: After total knee replacement (TKR) some patients report low self-perceived function, which is clinically measured using patient reported outcome measures (PROMs). However, PROMs, e.g. the Oxford Knee Score (OKS), inherently lack objective parameters of knee function. Biomechanical gait analysis is an objective and reliable measurement to quantitatively assess joint function. Therefore, the aim of this study was to explore the relationship between biomechanical gait parameters and the OKS. Methods: Gait analyses were recorded in 37 patients at least one year after primary TKR and in 24 healthy controls. Parameters from this analysis were calculated for hip, knee and ankle joint angles and joint moments in the sagittal and frontal plane including initial contact, early, late stance and swing. For the patients these parameters were expressed as its difference to control values at matched walking speed. Linear regression analyses were performed between the parameters from gait analysis and the OKS, with speed as covariate. Results: The difference in knee extension angle at initial contact and late stance between patients and controls was significantly related to the OKS. Per one degree knee extension difference increase, the OKS reduced with 1.0 to 1.6 points. Overall, patients extended their knee less than controls. Neither ankle and hip gait parameters, nor joint moments showed a relation with OKS. Conclusions: All patients with a submaximal score on the OKS showed limited knee extension during gait, even without a mechanical constraint in knee extension. This could be related to motor control limitations in this patient group.