Postural Stability in Unilateral Transtibial Amputees Using Two Suspension Systems: SmartpuckTM vs Lock and Pin

The number of individuals with lower limb amputation is growing. Individuals with transtibial amputation (TTA) face an increased risk of falling. Center of pressure (COP) is measured during quiet stance to assess postural stability and fall risk. The purpose of the present study was to examine postural stability of individuals with TTA using two suspension systems: SmartPuck™ (PUCK) and lock and pin (PIN). Four participants with TTA (71.34 ± 41.52 kg, 1.39 ± 0.08 m; 49.2 ± 27.79 years, K3 - K4) performed 30 seconds of quiet standing for four different conditions with each suspension system: (a) rigid surface eyes open (RSEO), (b) rigid surface eyes closed (RSEC), (c) compliant surface eyes open (CSEO), and (d) compliant surface eyes closed (CSEC). Center of pressure and vertical ground reaction forces (GRF) (1000 Hz) were collected using two force plates (AMTI, Watertown, MA). Throughout the four conditions, significant interlimb differences were observed in mean resultant velocity, mean AP velocity, 95% CE area, sway area, and %BWT, demonstrating greater reliance of the intact limb. As conditions increased in difficulty, more interlimb differences in measures of postural stability were present, demonstrating increased reliance of the intact limb when stability is challenged. No significant differences were found in either limb between PUCK and PIN suspensions. However, trends demonstrating increased control of postural stability were observed with PUCK suspension in the RSEO, RSEC, and CSEO conditions. Conversely, trends in measures of postural stability in the CSEC condition suggest increased stability with PIN suspension. As vision was removed and the standing surface was manipulated, participants demonstrated loss of control of postural stability, or instability. Confidence in the significance of the results is low due to the small number of individuals who participated in the study. Considering the direct relationship between instability and increased fall risk, it is important to identify whether different prosthesis designs can aid in postural steadiness. Further research with more participants is needed to understand the differences in postural stability caused by suspension systems