Subject-specific responses to an adaptive ankle prosthesis during incline walking

Individuals with lower-limb amputation often have difficulty walking on slopes, in part due to limitations of conventional prosthetic feet. Conventional prostheses have fixed ankle set-point angles and cannot fully replicate able-bodied ankle dynamics. Microprocessor-controlled ankles have been developed to help overcome these limitations. The objective of this study was to characterize how the slope adaptation feature of a microprocessor-controlled ankle affected individual prosthesis user gait biomechanics during sloped walking. Previous studies on similar microprocessor-controlled ankles have focused on group-level results (inter-subject mean), but did not report individual subject results. Our study builds upon prior work and provides new insight by presenting subject-specific results and investigating to what extent individual responses agree with the group-level results. We performed gait analysis on seven individuals with unilateral transtibial amputation while they walked on a 7.5° incline with a recently redesigned microprocessor-controlled ankle that adjusts ankle set-point angle to the slope. We computed gait kinematics and kinetics, and compared how users walked with vs. without this set-point adjustment. The microprocessor-controlled ankle increased minimum toe clearance for all subjects. Despite the microprocessor-controlled ankle behaving similarly for each user, we observed marked differences in individual responses. For instance, two users switched from a forefoot landing pattern with the microprocessor-controlled ankle locked at neutral angle to rearfoot landing when the microprocessor-controlled ankle adapted to the slope, while two maintained a forefoot and three maintained a rearfoot landing pattern across conditions. Changes in knee angle and moment were also subject-specific. Individual user responses were often not well represented by inter-subject mean. Although the prevailing experimental paradigm in prosthetic gait analysis studies is to focus on group-level analysis, our findings call attention to the high inter-subject variability which may necessitate alternative experimental approaches to assess prosthetic interventions.     

Dynamic stability of superior vs. inferior body segments in individuals with transtibial amputation walking in destabilizing environments

Interestingly, young and highly active people with lower limb amputation appear to maintain a similar trunk and upper body stability during walking as able-bodied individuals. Understanding the mechanisms underlying how this stability is achieved after lower-leg amputation is important to improve training regimens for improving walking function in these patients. This study quantified how superior (i.e., head, trunk, and pelvis) and inferior (i.e., thigh, shank, and feet) segments of the body respond to continuous visual or mechanical perturbations during walking. Nine persons with transtibial amputation (TTA) and 12 able-bodied controls (AB) walked on a 2 m×3 m treadmill in a Computer Assisted Rehabilitation Environment (CAREN). Subjects were perturbed by continuous pseudo-random mediolateral movements of either the treadmill platform or the visual scene. TTA maintained a similar local and orbital stability in their superior body segments as AB throughout both perturbation types. However, for their inferior body segments, TTA subjects exhibited greater dynamic instability during perturbed walking. In TTA subjects, these increases in instability were even more pronounced in their prosthetic limb compared to their intact leg. These findings demonstrate that persons with unilateral lower leg amputation maintain upper body stability in spite of increased dynamic instability in their impaired lower leg. Thus, transtibial amputation does significantly impair sensorimotor function, leading to substantially altered dynamic movements of their lower limb segments. However, otherwise relatively healthy patients with unilateral transtibial amputation appear to retain sufficient remaining sensorimotor function in their proximal and contralateral limbs to adequately compensate for their impairment.     

超声引导下外周神经阻滞对老年下肢动脉硬化闭塞症截肢术患者循环系统和疼痛的影响

目的:研究超声引导下外周神经阻滞对老年下肢动脉硬化闭塞症截肢术患者循环系统和疼痛的影响。方法:选择我院2016年2月～2019年11月收治的82例老年下肢动脉硬化闭塞症患者为研究对象,所有患者均接受下肢截肢术治疗,对照组采用硬膜外麻醉,研究组采用超声引导下外周神经阻滞。对比两组感觉神经、运动神经阻滞情况、阻滞效果,循环功能,疼痛指标和不良反应。结果:研究组感觉神经及运动神经阻滞起效时间较对照组短,感觉神经及运动神经阻滞维持时间较对照组长,差异比较有统计学意义(P0.05)。两组优良率差异比较无统计学意义(P0.05)。手术开始30 min时,对照组心率、平均动脉压均下降,研究组无明显改变,差异比较有统计学意义(P0.05)。术后24h时,两组疼痛指标浓度均较入室时增加,研究组低于对照组,差异比较有统计学意义(P0.05)。研究组不良反应总发生率低于对照组(P0.05)。结论:老年下肢动脉硬化闭塞症截肢术患者予以超声引导下外周神经阻滞的起效时间更快,能够减轻围术期疼痛,保持术中循环功能的稳定。     

The Dutch consensus on the diabetic foot

In 1996 the Dutch Diabetes Federation installed a consensus committee to formulate practical guidelines for daily practice to prevent, diagnose and treat foot-related complications in patients with diabetes mellitus. A list of definitions was formulated. A new ulcer classification was introduced. Pathophysiology, diagnostic and therapeutic strategies were discussed with special attention for patients with a high risk foot and for prevention instruction. After several rounds of implementation the definite document was unanimously accepted in the fall of 1998.     

Primary motor cortex reorganization in a long-term monkey amputee

The primary motor cortex (M1) was mapped with intracortical microstimulation (ICMS) in a 15 year-old macaque whose right upper extremity was amputated at the shoulder joint prior to 2 years of age. Movements of the right shoulder girdle and stump were evoked by ICMS throughout the left M1 upper extremity region. The size of the left M1 upper extremity region contralateral to the amputated arm was not appreciably different from the size of the right upper extremity region contralateral to the intact arm. Long stimulus trains and/or higher stimulus currents were needed to evoke detectable movements at significantly more loci in the left than in the right M1 upper extremity region. These observations would be consistent with unmasking of a high threshold representation of shoulder musculature that normally exists throughout the central core of the upper extremity region, where it underlies a lower threshold representation of the distal forelimb. Alternatively, invasion of the de-efferented distal forelimb core by surrounding shoulder representation may have occurred. Differences between the limited M1 reorganization observed in the present study and the more extensive reorganization of S1 observed in other studies may reflect fundamental differences between M1 and S1, and/or differences in the extent of de-efferentation versus deafferentation.     

Altered flexion-relaxation responses exist during asymmetric trunk flexion movements among persons with unilateral lower-limb amputation

Repetitive exposures to altered gait and movement following lower-limb amputation (LLA) have been suggested to contribute to observed alterations in passive tissue properties and neuromuscular control in/surrounding the lumbar spine. These alterations, in turn, may affect the synergy between passive and active tissues during trunk movements. Eight males with unilateral LLA and eight non-amputation controls completed quasi-static trunk flexion–extension movements in seven distinct conditions of rotation in the transverse plane: 0° (sagittally-symmetric), ±15°, ±30°, and ±45° (sagittally-asymmetric). Electromyographic (EMG) activity of the bilateral lumbar erector spinae and lumbar kinematics were simultaneously recorded. Peak lumbar flexion and EMG-off angles were determined, along with the difference (“DIFF”) between these two angles and the magnitude of peak normalized EMG activities. Persons with unilateral LLA exhibited altered and asymmetric synergies between active and passive trunk tissues during both sagittally-symmetric and -asymmetric trunk flexion movements. Specifically, decreased and asymmetric passive contributions to trunk movements were compensated with increases in the magnitude and duration of active trunk muscle responses. Such alterations in trunk passive and active neuromuscular responses may result from repetitive exposures to abnormal gait and movement subsequent to LLA, and may increase the risk for LBP in this population.