User's Limb Research Articles

Performance‐driven motion choreographing with accelerometers

AbstractLive performance is an intuitive way to naturally draft the desired motion in the choreographer's mind. In this paper we present a novel approach to choreographing motions by live performance captured with degree of freedom (3‐DOF) accelerometers. The process begins by placing the accelerometers on the user's limbs according to the pre‐specified positions. The computer then recognizes the performed actions using Hidden Markov Model (HMM), which is pre‐trained by the acceleration data samples automatically generated from a pre‐segmented motion capture database. At last, the captured actions are further synthesized with motion retiming and exaggeration based on the acceleration signals from the accelerometers. This method can intuitively rapid‐prototype the choreographed motions for pre‐production of animation, the avatar control in virtual reality and game‐like scenarios, etc. The experimental results show that it can effectively recognize actions with spatial‐time variance, and is easy‐to‐use especially for a novice with little experience. Copyright © 2009 John Wiley & Sons, Ltd.

Effect of Training on Upper-Extremity Prosthetic Performance and Motor Learning: A Single-Case Study

Dromerick AW, Schabowsky CN, Holley RJ, Monroe B, Markotic A, Lum P. Effect of training on upper-extremity prosthetic performance and motor learning: a single-case study. Objectives To examine the impact of a new prosthesis on an experienced and highly motivated prosthetic limb user, to evaluate the effects of training and the ability of clinical measures to detect change, and to gain insight into the mechanisms by which improvement occurs. Design A single-case study. Setting An outpatient clinic. Participant A bilateral high-arm amputee (right shoulder disarticulation, left above elbow). Interventions Provision of new prosthesis and occupational therapy. Main Outcome Measures Action Research Arm Test, box and block test of manual dexterity, Jebsen-Taylor Hand Function Test, and speed and accuracy of reaching movements with and without visual guidance. Results In this experienced prosthesis user, provision of a new prosthesis led to an immediate worsening in functional limitation. With training, the subject recovered his baseline status and then exceeded it in both proximal and distal function. All study clinical measures detected change, but the change detected varied as much as 300-fold depending on the measure chosen. The clinical improvements were associated with modest improvements in the speed of reaching but not the accuracy of reaching under visual guidance. Improvements in reaching accuracy without visual guidance were seen after 10 trials, suggesting that some motor learning had occurred. Conclusions Provision of a new prosthesis can cause functional decline even in an experienced user; this decline can be reversed with training. There is wide variability in sensitivity to change among functional limitation measures. Although some training-related improvements may have been due to increased speed and accuracy of reaching without visual guidance, skill in prosthesis use also plays a role.

Stump Ulcers and Continued Prosthetic Limb Use

Stump ulcers are common problems in amputees. Temporary discontinuation of prosthetic limb use is frequently employed to facilitate healing. Inevitably, this limits activity and may, for instance, prevent an amputee from going to work. A survey of clinical practice was carried out based on the premise that controlled continued prosthetic limb use in patients with stump ulcers will not adversely affect the ulcer nor prevent healing. The survey would also form a basis for developing future guidelines in the management of stump ulcers. All consecutive patients attending the Chapel Allerton Hospital prosthetic clinic between January 2003 and May 2004 with stump ulcers were recruited into the study. Primary outcome measures were changes in the surface area of the ulcers and in clinical photographs taken on 2 occasions 6 weeks apart. Some 102 patients with a mean age 60 years (range 18 - 88 years) were recruited. Eight patients who were established prosthetic limb users did not complete the study and were excluded from the analysis. Of the patients 52 were newly referred patients with delayed surgical wound healing while 42 were established prosthetic limb users for at least 1 year. Continued prosthetic limb was associated with a significant reduction in ulcer size (p < 0.05). Mean sizes of the ulcers at first and second observations were 3.30 cm2 (range 0.06 - 81) and 0.70 cm2 (range 0.00 - 13.00) respectively. The ulcers improved in 83 cases while two were unchanged. Deterioration was observed in nine cases. The current clinical practice is to allow most of the patients to commence or continue prosthetic limb wearing despite the presence of stump ulceration. This observational study found that, despite prosthetic use, 60 (64%) cases healed completely within the six-week study period and 23 (25%) ulcers reduced in size. The ulcers were unchanged in 2% of the cases. Deterioration was observed in nine (9%) cases. This survey suggests that the current practice of allowing patients to use their prostheses is safe. A clinical trial is now needed to establish whether this practice alters healing rate or has any other disadvantages for new or established amputees.

Cardiovascular and Renal Regulation by the Angiotensin Type 2 Receptor

The renin-angiotensin system is a coordinated hormonal cascade of major importance in cardiovascular and renal regulation. The principle effector of this system is the octapeptide angiotensin II (Ang II), which acts at 2 cell membrane receptors, AT1 and AT2. The majority of the actions of Ang II have been demonstrated to be mediated by the AT1 receptor, including growth promotion, vasoconstriction, antinatriuresis, aldosterone secretion, salt appetite, thirst, sympathetic outflow and inhibition of renin biosynthesis, and secretion.1 The AT2 receptor has been less well understood. Past studies, however, clearly demonstrated that the AT2 receptor mediates cellular differentiation and growth, opposing the actions of Ang II through the AT1 receptor.2 Studies in the mid to late 1990s demonstrated that AT2 receptor stimulation engenders an autacoid vasodilator cascade composed of bradykinin (BK), nitric oxide (NO), and guanosine cyclic 3′, 5′-monophosphate (cGMP).3–5 This discovery turned attention to the possibility that the AT2 receptor may mediate vasodilation, opposing the vasoconstrictor actions of Ang II at the AT1 receptor.6 Parallel cell signaling studies indicated that the AT2 receptor is G-protein–coupled (through Giα) and that receptor stimulation is accompanied by an increase in phosphotyrosine phosphatase activity and an inhibition of MAP kinase enzymes (p42 and p44) composing the extracellular signal-related kinase (ERK1/2). AT2 receptor-mediated inhibition of the extracellular signal-regulated kinase pathway opposed the actions of Ang II, resulting in extracellular signal-regulated kinase phosphorylation via the AT1 receptor.1,2,6,7 Work during the late 1990s through 2002 suggested that the AT2 receptor might serve as a vasodilator counterforce to the AT1 receptor.2,6,7 However, vasorelaxation was difficult to elicit in some experimental models, attributed to the relatively low level of AT2 receptor vascular expression compared with that of the …

Skin disorders in amputees

Background: Dermatologic problems restrict the normal use of a prosthetic limb. The importance of contact dermatitis to skin morbidity in a population of amputees and the selection criteria for patch testing have not been clearly defined. Objective: We describe the range of dermatoses seen in a population of amputees and examine the incidence, causes, and patterns of contact dermatitis. Methods: This is a questionnaire-based, cross-sectional study of 210 amputees. Those with a skin problem were assessed by a dermatologist. Patch testing was undertaken in patients with persistent dermatitis. Results: A total of 34% of amputees experienced a skin problem. Lesions resulting from friction, pressure, and occlusion are common. Allergic contact dermatitis is seen in a third of patients with stump dermatitis. There are no features that distinguish allergic from irritant (chemical or physical) dermatitis. Conclusion: Dermatologic problems are common in prosthetic limb users. Allergic contact dermatitis is a significant problem, and all patients with dermatitis on the residual limb should be patch tested. (J Am Acad Dermatol 2000;42:501-7.)

A Survey of Upper-Limb Prosthesis Users in Oxfordshire

The design of a new device should embrace the needs of the target population. A survey of prosthetic limb users was performed at the Oxford Limb-Fitting Centre, Headington, Oxford, as part of the specification for an intelligent hand prosthesis. Users of prosthetic limbs were questioned about the positive and negative attributes of their limb and were asked about their wishes for the design of prostheses. A questionnaire was devised to address this and sent to 80 subjects; 69% responded. It was found that light weight, durability, ease of cleaning, longevity of operation (up to 12 hours), and suitability for driving were highlighted as priorities. This information was incorporated into the design of a new powered hand prosthesis. This article reviews the results of the survey and makes comparisons with similar studies. Finally, recommendations are made for the designs of any new prosthesis system.

Virtual reality in rehabilitation

Virtual reality is an interactive, computer generated environment that simulates the real world. Accessible via an interface that has been adapted to the human senses, it provokes in the user the sensation of immersion, like Alice in Wonderland crawling down the rabbit hole and finding herself in a new fantastic world.1 A dataglove wired with fibreoptics to record the degree of bending of fingers and wrists, a head-mounted display, and an exoskeleton surrounding the user's limbs to give feedback, project the user into the virtual environment and report back on his or her actions within it. The user can react intuitively to the virtual world, any actions being detected by position and movement sensors placed strategically on his or her body. A computer calculates the changes occurring in the virtual world according to the rules chosen by its creator and feeds the results back to the user. Applications appeal to disabled and non-disabled persons alike2: telepresence, for example, allows specialists to operate on patients in remote hospitals. Three applications of …

Functional outcome of lower limb amputees with peripheral vascular disease

A series of 40 patients accepted for prosthetic rehabilitation after lower limb amputations for peripheral vascular disease were reviewed nine to 27 months later. Two have since died, one has not been traced, and 37 have been assessed. Fourteen were successful full-time limb users ('walkers'), 10 were partial users ('partial walkers') and 13 were wheelchair-dependent ('none walkers' or 'wheelchair users'). Of the walkers, 85% completed a 10-metre walk in under 30 seconds (mean 20s), whereas 90% of the partial walkers took over 30 seconds (mean 79s). The Barthel Activities of Daily Living (ADL) Index, a measure of independence in self-care, correlated closely with outcome status and walking speed. Other items that correlated well with outcome included grip strength, assessed using a simple hand-held dynanometer, and cardiovascular fitness, the measure being time taken for the pulse to return to resting baselme after exercise. This was less than two minutes in 85% of the walkers (mean 94s) and two minutes or more in 100% of the partial walkers (mean 240s). Age did not indicate whether prosthetic training would be successful, but in those who were walking it correlated closely with speed. The partial walkers had lower kitchen and domestic activity scores, which were due to lack of environmental modification for wheelchair use, it being assessed that their walking status conferred ability to do tasks whilst standing. These patients can easily be identified by measuring their walking speed and Barthel ADL Index.