Effects of a powered prosthetic foot on sit-to-stand performance for individuals with trans-tibial amputation

Abstract

Introduction: Many functional limitations occur following lower limb amputation. Those limitations can impair a person’s ability to complete activities of daily living, such as standing up from a seated position. The sit-to-stand movement is a complex movement and is considered to be one of the most mechanically demanding functional task routinely undertaken during daily activities. People with trans-tibial amputations tend to have asymmetrical loading between limbs and favor the sound limb over the amputated one. This can lead to secondary complications such as osteoarthritis in hips and/or knees and back pain. Powered prosthetics and their correct use may help people decrease the likelihood of developing those secondary complications. The purpose of the study was to examine the effects of active assistance from a powered prosthetic foot on the sit–to–stand task.Methods: Four individuals with transtibial amputation participated, with three completing the study. Lower body kinematic and kinetic data were collected using force plates and a 12-camera motion capture system during the sit-to-stand task. The main outcome measures included vertical ground reaction forces (vGRF), and bilateral ankle, knee, and hip joint angles and power. A powered prosthetic foot was used in the study and outcome measures measured with the foot function turned on and turned off, termed ON/OFF settings. Mixed model analysis of variance (ANOVA) was used to evaluate the symmetry of vGRF between sides, differences in joint power and angles between the sound limb and the amputated limb in ON/OFF settings. The level for significance was set to alpha 0.05.Results: No statistically significant main effect for side (AMP/Sound) or setting (ON/OFF) was found for vGRF nor interactions between side and setting. For joint power a statistically significant main effect for side was found in all three joints (ankle (p=0.014), knee (p=0.021), hips (p=0.011)), but a main effect of setting was observed only at the ankle (p=0.014). For joint power there was no interactions between side and setting found at any of the joints. For joint angles a statistically significant main effect of setting was found at the ankle((p<0.001) and hip (p=0.004)) but not at the knee. A statistically significant main effect of side and an interaction between setting and side was found at the ankle only (p<0.001). Conclusion: According to this study the powered prosthetic ankle tested did not affect symmetry of weight bearing between sides during the sit-to-stand movement for trans-tibial amputees. The results must be interpreted with caution for various reasons and more research on the matter is needed with bigger cohort of participants.