Minimum toe clearance and tripping probability in people with unilateral transtibial amputation walking on ramps with different prosthetic designs

Abstract

Background: Minimum Toe Clearance (MTC) is defined as the minimum vertical distance between the lowest point under the front part of the foot and the ground, during mid-swing. Low values of MTC and walking on inclines are both related to higher probability of tripping and falling in lower limb amputees. New prosthetic designs aim at improving MTC, especially on ramps, however the real effect on MTC still needs investigation. The objective of this study was then to evaluate the effect of different prosthetic designs on MTC in inclined walking. Methods: Thirteen transtibial amputees walked on a ramp using three different prostheses: non articulating ankle (NAA), articulating hydraulic ankle (AHA), and articulating hydraulic ankle with microprocessor (AHA-MP). Median MTC, coefficient of variation (CV), and tripping probability (TP) for obstacles of 10 and 15 mm were compared across ankle type in ascent and descent. Findings: When using AHA-MP, larger MTC median values for ascending (P ≤ 0.001, W = 0.58) and descending the ramp (P = 0.003, W = 0.47) were found in the prosthetic limb. Also significantly lower CV was found on the prosthetic limb for both types of AHA feet when compared to NAA for descending the ramp (P = 0.014, W = 0.45). AHA-MP showed the lowest TP for the prosthetic leg in three conditions evaluated. On the sound limb results showed the median MTC was significantly larger (P = 0.009, W = 0.43) and CV significantly lower (P = 0.005, W = 0.41) when using an AHA in ascent. Interpretation: Both AHA prosthetic designs help reduce the risk of tripping of the prosthetic limb by increasing the median MTC, lowering its variability and reducing TP for both legs when ascending and descending the ramp. For most of the conditions, AHA-MP showed the lowest TP values. Findings suggest that AHA prostheses, especially AHA-MP could reduce the risk of tripping on ramps in amputees. [11][12][13], type of terrain [14,15] and type of shoes [15]. The changes are reflected on MTC distribution, including median, interquartile

Design and Validation of a Real-Time Visual Feedback System to Improve Minimum Toe Clearance (mTC) in Transfemoral Amputees

“…People with transfemoral amputation fall more frequently than the transtibial amputees, with more than 60% of falls at least once in a year due to tripping [2], [3]. Tripping occurs during the mid-swing phase of gait when the toe approaches minimum distance from the ground, i.e., at minimum toe clearance (mTC) which is defined as the minimum vertical distance between the lowest point under the front part of the foot and the ground, during midswing, while the foot progresses forward with maximum swing velocity [4], [5]. Therefore, mTC is an important consideration to quantify the risk of tripping in the lower limb amputee population.…”

Does Gait with an Ankle Foot Orthosis Improve or Compromise Minimum Foot Clearance?

“…This increase in time may also explain the apparently higher MFC, as a higher clearance may be possible with a longer step time. Therefore, we may conclude that the increased swing and step times may be related to a slower limb translation rather than achieving significantly higher distances with the RL, or may even be related to the counteracting of some instability caused by the AFO [ 29 ]. This agrees with Vistamehr et al [ 30 ], who observed a decrease in the propulsive impulse in the AFO limb compared to the contralateral leg.…”

Can microprocessor knees reduce the disparity in trips and falls risks between above and below knee prosthesis users?

“…Meanwhile, below knee prosthesis users are likely to be fitted with a hydraulic ankle but, once more, because the data were not recorded, the proportion of users in this dataset is unknown. There is published evidence that hydraulic ankles present increased ground clearance during swing [27,28] and enhanced standing stability [29], compared to feet that are rigidly-attached at the ankle. More recently, some researchers have investigated how the combinations of advanced prosthetic knees and ankles work together, suggesting the combination of the two technologies may have biomechanical advantages for balance [29], mobility [30] and navigating everyday, environmental barriers, such as stairs and slopes [30].…”