Powered hip exoskeleton improves walking economy in individuals with above-knee amputation.

Above-knee amputation severely reduces the mobility and quality of life of millions of individuals. Walking with available leg prostheses is highly inefficient, and poor walking economy is a major problem limiting mobility. Here we show that an autonomous powered hip exoskeleton assisting the residual limb significantly improves metabolic walking economy by 15.6 ± 2.9% (mean ± s.e.m.; two-tailed paired t-test, P = 0.002) in six individuals with above-knee amputation walking on a treadmill. The observed metabolic cost improvement is equivalent to removing a 12-kg backpack from a nonamputee individual. All participants were able to walk overground with the exoskeleton, including starting and stopping, without notable changes in gait balance or stability. This study shows that assistance of the user's residual limb with a powered hip exoskeleton is a viable solution for improving amputee walking economy. By significantly reducing the metabolic cost of walking, the proposed hip exoskeleton may have a considerable positive impact on mobility, improving the quality of life of individuals with above-knee amputations.

Safe Selection of Outpatient Joint Arthroplasty Patients With Medical Risk Stratification: the "Outpatient Arthroplasty Risk Assessment Score".

BACKGROUND: Current patient selection criteria and medical risk stratification methods for outpatient primary total joint arthroplasty (TJA) surgery are unproven. This study assessed the predictive ability of a medically based risk assessment score in selecting patients for outpatient and short stay surgery. METHODS: A retrospective review of 1120 consecutive primary TJAs in an early discharge program was performed. An Outpatient Arthroplasty Risk Assessment ("OARA") score was developed by a high-volume arthroplasty surgeon and perioperative internal medicine specialist to stratify patients as "low-moderate risk (≤59)" and "not appropriate" (≥60) for early discharge. OARA, American Society of Anesthesiologists Physical Status Classification System (ASA-PS), and Charlson comorbidity index (CCI) scores were analyzed with respect to length of stay. RESULTS: The positive predictive value of the OARA score was 81.6% for the same or the next day discharge, compared with that of 56.4% for ASA-PS (P < .001) and 70.3% for CCI (P = .002) scores. Patients with OARA scores ≤59 were 2.0 (95% confidence interval [CI], 1.4-2.8) times more likely to be discharged early than those with scores ≥60 (P < .001), while a low ASA-PS score was 1.7 (95% CI, 1.2-2.3) times more likely to be discharged early (P = .001). CCI did not predict early discharge (P ≥ .301). With deliberate patient education and expectations for outpatient discharge, the odds of early discharge predicted by the OARA score, but not the ASA-PS score, increased to 2.7 (95% CI, 1.7-4.2). CONCLUSION: The OARA score for primary TJA has more precise predictive ability than the ASA-PS and CCI scores for the same or next day discharge and is enhanced with a robust patient education program to establish appropriate expectations for early discharge. Early results suggest that the OARA score can successfully facilitate appropriate patient selection for outpatient TJA, although consideration of clinical program maturity before adoption of the score is advised.