Does a Microprocessor-controlled Prosthetic Knee Affect Stair Ascent Strategies in Persons With Transfemoral Amputation?

Abstract

Background Stair ascent can be difficult for individuals with transfemoral amputation because of the loss of knee function. Most individuals with transfemoral amputation use either a step-to-step (nonreciprocal, advancing one stair at a time) or skip-step strategy (nonreciprocal, advancing two stairs at a time), rather than a step-over-step (reciprocal) strategy, because step-to-step and skip-step allow the leading intact limb to do the majority of work. A new microprocessor-controlled knee (Ottobock X2 1 ) uses flexion/extension resistance to allow step-over-step stair ascent. Questions/Purposes We compared self-selected stair ascent strategies between conventional and X2 1 prosthetic knees, examined between-limb differences, and differentiated stair ascent mechanics between X2 1 users and individuals without amputation. We also determined which factors are associated with differences in knee position during initial contact and swing within X2 1 users. Methods Fourteen individuals with transfemoral amputation participated in stair ascent sessions while using conventional and X2 1 knees. Ten individuals without amputation also completed a stair ascent session. Lowerextremity stair ascent joint angles, moment, and powers and ground reaction forces were calculated using inverse dynamics during self-selected strategy and cadence and controlled cadence using a step-over-step strategy. Results One individual with amputation self-selected a stepover-step strategy while using a conventional knee, while 10 individuals self-selected a step-over-step strategy while using X2 1 knees. Individuals with amputation used greater prosthetic knee flexion during initial contact (32.5°, p = 0.003) and swing (68.2°, p = 0.001) with higher intersubject variability while using X2 1 knees compared to conventional knees (initial contact: 1.6°, swing: 6.2°). The increased prosthetic knee flexion while using X2 1 knees normalized knee kinematics to individuals without amputation during swing (88.4°, p = 0.179) but not during initial contact (65.7°, p = 0.002). Prosthetic knee flexion during initial contact and swing were positively correlated with prosthetic limb hip power during pull-up (r = 0.641, p = 0.046) and push-up/ early swing (r = 0.993, p \ 0.001), respectively. Conclusions Participants with transfemoral amputation were more likely to self-select a step-over-step strategy similar to individuals without amputation while using X2 1 knees than conventional prostheses. Additionally, the increased prosthetic knee flexion used with X2 1 knees placed large power demands on the hip during pull-up and push-up/early swing. A modified strategy that uses less knee flexion can be used to allow step-over-step ascent in individuals with less hip strength. Level of EvidenceLevel II, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.

Functional performance differences between the Genium and C-Leg prosthetic knees and intact knees

“…Another study assessed stair ascent using the Ottobock X2 MPK compared with NMPKs [29]. The X2 and Genium are comparable regarding stair gait function, using flexion/extension resistance timing to maximize user climbing ability with their own strength as opposed to systems offering external-powered assistance [8,[29][30]. Persons with TFA used a reciprocal stepping strategy with the X2, necessitating greater hip power, corroborating Bellman et al's findings [8,29].…”

“…Specific research regarding functional stair gait performance and stair gait during load carriage is necessary to corroborate Bellman et al's findings. Another study assessed stair ascent using the Ottobock X2 MPK compared with NMPKs [29]. The X2 and Genium are comparable regarding stair gait function, using flexion/extension resistance timing to maximize user climbing ability with their own strength as opposed to systems offering external-powered assistance [8,[29][30].…”

“…The X2 and Genium are comparable regarding stair gait function, using flexion/extension resistance timing to maximize user climbing ability with their own strength as opposed to systems offering external-powered assistance [8,[29][30]. Persons with TFA used a reciprocal stepping strategy with the X2, necessitating greater hip power, corroborating Bellman et al's findings [8,29]. While both studies demonstrate biomechanical improvements and control strategy with this system, neither has done so during functional task completion, particularly while carrying a load, an activity common in daily life.…”

Crossover study of amputee stair ascent and descent biomechanics using Genium and C-Leg prostheses with comparison to non-amputee control

“…Aldridge Whitehead et al studied stair ascent in young active male TFAs [14], reporting that the majority of participants (13 of 14) preferred a ST or skip-step (an ST gait that advances two stairs per stride) gait on their conventional prostheses, which were a C-Leg or Total Knee (Ossur), and that the majority (10 of 14) preferred a SOS gait while using the Genium knee. While the adoption rate of the SOS as the preferred gait style was not as high in our study, we did observe a more heterogeneous representation of the amputee population, and our participants were asked to not use handrails during testing.…”

Analysis of clinically important factors on the performance of advanced hydraulic, microprocessor-controlled exo-prosthetic knee joints based on 899 trial fittings

“…Aldridge et al [25] observed that 71% of subjects were capable of ascending stairs step over step in a population of 14 subjects with MCFL rating 3 and 4. Highsmith et al [26] reported that 14 out of 20 (70%) K3 and K4 transfemoral amputees who received training were able to ascend stairs reciprocally.…”