Peak External Adduction Moment Research Articles

Static and dynamic abductor function are both associated with physical function 1 to 5 years after total hip arthroplasty

BackgroundA subset of total hip arthroplasty patients experience functional impairments past the first postoperative year. Poor hip abductor function is common before and in the early postoperative period. It is not known if abductor impairment is associated with long-term functional impairment. This study evaluated the relationships between static and dynamic abductor function and performance-based and self-reported function >1 year post-total hip arthroplasty. MethodsEighteen adults 1–5 years post-total hip arthroplasty participated. Static and dynamic abductor function were assessed through dynamometry and gait analysis, respectively. Subjects completed four physical performance tests and two self-report instruments. FindingsHigher peak isometric abductor strength was associated with better performance-based function (P ≤ 0.001–0.030) and with self-reported function (P ≤ 0.001–0.012). Higher peak external adduction moment was associated with better results on 3 of 4 performance tests (P = 0.007–0.026). Together, static and dynamic abductor function predicted 35–77% of the variation in physical function. Abductor strength best predicted walking test results and self-reported function, while dynamic abductor function best predicted tests involving sit-to-stand InterpretationStatic and dynamic abductor function were associated with physical function 1–5 years after total hip arthroplasty. These results support further investigation of interventions targeting abductor function for persons experiencing persistent impairments.

Does hip implant positioning affect the peak external adduction moments of the healthy knees of subjects with total hip replacements?

After unilateral total hip replacement (THR) for hip osteoarthritis (OA), knee OA incidence or progression is common. The contralateral knee is at particular risk, and some have speculated that abnormal THR-hip biomechanics contributes to this asymmetry. We investigated the relationships between operated-hip joint geometry or gait variables and the peak external knee adduction moments-an indicator of knee OA risk-in 21 subjects with unilateral THRs. We found that the peak adduction moment was 14% higher on the contralateral versus the ipsilateral knee (p = 0.131). The best predictors of ipsilateral knee adduction moments were superior-inferior joint center position and operated-hip peak adduction moment (adj R(2) = 0.291, p = 0.017). The sole predictor of the contralateral knee adduction moment was the medial-lateral hip center position (adj R(2) = 0.266, p = 0.010). A postoperative medial shift of the hip center was significantly correlated with a lower postoperative contralateral/ipsilateral knee adduction moment ratio (R = 0.462, p = 0.035). Based on these relationships, we concluded that implant positioning could influence the biomechanical risk of knee OA progression after THR. Although implant positioning decisions are necessarily driven by other factors, it may be appropriate to assess individual THR candidate's knee OA risk and adjust perioperative management accordingly.

Do gait adaptations during stair climbing result in changes in implant forces in subjects with total hip replacements compared to normal subjects?

Background The study objective was to identify gait abnormalities and their relationships to hip loading during stair climbing after total hip replacement. Hypotheses: (1) total hip replacement subjects would have significantly lower dynamic hip range of motion and peak external moments during stair climbing compared to normal subjects and (2) the peak twisting moment about the long axis of the implant and peak hip forces would be significantly reduced in subjects with total hip replacements compared to normal subjects. Methods Gait parameters during a stair climbing task were measured for 15 total hip replacement subjects and 15 matched normal subjects. Forces were predicted using an analytical model. Findings The peak external adduction moment for the total hip replacement subjects was 25% less than normal ( P = 0.001). The external rotation moment was 26% less than normal ( P = 0.029) but the extension moment was 77.5% higher in the total hip subjects than in normal subjects ( P = 0.004). The peak twisting moment and first peak contact force were 18% and 14% lower in the total hip group compared to normal ( P = 0.090 and P = 0.055, respectively). The second peak force was nearly equal ( P = 0.424) between the two groups. Interpretation Stair climbing biomechanics differ from normal in subjects with total hip replacements, however these unconscious alterations do not abnormally increase the hip loads during this activity. More work is necessary to determine exactly what constitutes optimal stair climbing biomechanics for patients with total hip replacements.

Effects of Disease Severity on Response to Lateral Wedged Shoe Insole for Medial Compartment Knee Osteoarthritis

Shimada S, Kobayashi S, Wada M, Uchida K, Sasaki S, Kawahara H, Yayama T, Kitade I, Kamei K, Kubota M, Baba H. Effects of disease severity on response to lateral wedged shoe insole for medial compartment knee osteoarthritis. Objective To determine the effects of lateral wedged insoles on knee kinetics and kinematics during walking, according to radiographic severity of medial compartment knee osteoarthritis (OA). Design A prospective case control study of patients with medial compartment OA of the knee. Setting Gait analysis laboratory in a university hospital. Participants Forty-six medial compartment knees with OA of 23 patients with bilateral disease and 38 knees of 19 age-matched healthy subjects as controls. Interventions Not applicable. Main Outcome Measures We measured the peak external adduction moment at the knee during the stance phase of gait and the first acceleration peak after heel strike at the lateral side of the femoral condyles. Kellgren and Lawrence grading system was used for radiographic assessment of OA severity. Results The mean value of peak external adduction moment of the knee was higher in OA knees than the control. Application of lateral wedged insoles significantly reduced the peak external adduction moment in Kellgren-Lawrence grades I and II knee OA patients. The first acceleration peak value after heel strike in these patients was relatively high compared with the control. Application of lateral wedged insoles significantly reduced the first acceleration peak in Kellgren-Lawrence grades I and II knee OA patients. Conclusions The kinetic and kinematic effects of wearing of lateral wedged insoles were significant in Kellgren-Lawrence grades I and II knee OA. The results support the recommendation of use of lateral wedged insoles for patients with early and mild knee OA.

Use of a lateral offset short-leg walking cast before high tibial osteotomy.

The clinical results after high tibial osteotomy for the treatment of symptomatic varus gonarthrosis are unpredictable. Although preoperative gait analysis has been shown to be useful in predicting successful outcome after high tibial osteotomy, there are no readily available preoperative clinical tests for predicting success. The authors did a study to determine the effects of an offset short-leg walking cast as a potential predictor of clinical success after high tibial osteotomy. Specifically, the authors evaluated the effect of an offset short-leg walking cast on pain relief and changes in the peak external adduction moments in patients with symptomatic varus gonarthrosis indicated for high tibial osteotomy. Nineteen consecutive patients indicated for high tibial osteotomy were enrolled and completed the study. All patients had precast gait analysis to determine baseline parameters. Immediately after gait analysis, a short-leg lateral offset walking cast was applied and worn for 3 days to allow time for adaptation. Gait analysis then was repeated. Western Ontario and McMaster Universities Osteoarthritis Index pain scores were obtained before and after the cast was applied. The cast resulted in a mean reduction in pain of 53%, and a mean reduction in the peak external adduction moment of 36% in the 17 of 19 patients who tolerated the cast. The reduction in pain was correlated with the reduction in the peak adduction moment (r = 0.63). The authors conclude that an offset short-leg walking cast results in pain reduction that correlates with changes in external adduction moments about the knee. Therefore, an offset short-leg walking cast may prove to be an effective tool for predicting patients who ultimately will benefit from valgus high tibial osteotomy.