Intermanual transfer effects in novice and experienced below-elbow myoelectric prosthesis users

Background. Intermanual transfer training may be beneficial for persons with an upper limb amputation, since it facilitates prosthesis training shortly after the amputation. Intermanual transfer implies improvement of skill in the affected arm, after training the unaffected arm. Previously, this has been demonstrated only in able-bodied persons for prosthetic skills. Objective. To determine intermanual transfer effects in patients with a below-elbow amputation, in both experienced (experiment A) and novice (experiment B) myoelectric prosthesis users, and to establish whether laterality affects these effects. Design. A: Case-control, B: Case-series. Methods. A: Experienced myoelectric prosthesis users (n=22) and matched controls (n=22) performed tasks using a prosthesis simulator attached to their non-affected arm. Outcomes were movement time, force control, Box and Blocks test (BBT)scores and duration of hand opening. B: A training group of novice myoelectric prosthesis users who trained using the simulator (n=3) were compared to a control group of novice users who did not train (n=4). Group-allocation was randomized. Movement time and force control were measured in the affected arm using the patient’s own prosthesis. Results. Movement times of experienced (A) and trained novice (B) myoelectric prosthesis users were shorter. Experienced users (A) had a higher BBT-score and a shorter hand opening duration compared to controls. No intermanual transfer effects on force control and no laterality effects were found. Limitations. Blinding was not feasible, and only few novice users were measured. Conclusions. Intermanual transfer effects were present after training in persons with a below-elbow amputation, independent of laterality. This is of clinical relevance for persons with an upper-limb amputation, for it supports the idea that prosthesis handling benefits from intermanual transfer training shortly after the amputation. Intermanual transfer effects in novice and experienced below-elbow myoelectric prosthesis users 117 7 INTRODUCTION Persons with an upper limb amputation reject their prosthesis in approximately 20-40%, because of a low degree of functionality. 2 To reduce this high percentage of refusal, one can improve the design of the prosthesis. Another way is to improve the handling of the prosthesis, which can be established by training. 126 Starting prosthetic training early after the amputation, preferably within the first four weeks, could result in better acceptance and handling of the prosthetic device. 9, 26 A problem of training immediately after the amputation is that the wound on the stump is not yet healed and the stump contains edema. Furthermore, the prosthesis needs to be constructed and fitted. For these reasons, most of the patients can only be fitted with a proper myoelectric prosthesis a few months after the amputation. To improve prosthetic handling immediately after the amputation, intermanual transfer might be useful. 61, 71, 95 Intermanual transfer means that a motor skill trained in one arm, also improves in the other arm. 28-30 When applying intermanual transfer immediately after an upper-limb amputation, the unaffected arm can be trained in prosthetic skills using a prosthesis simulator immediately after the amputation. A simulator is operated in the same way as an actual prosthesis, but is worn on the unaffected arm. In several previous studies, intermanual transfer effects in learning to use a prosthetic device were found. 18, 61, 71, 95 However, these studies used able-bodied participants and to this date no studies on transfer of prosthesis skills have been conducted with persons with an upper limb amputation. It is expected that after an intermanual transfer training the performance with the actual prosthesis will be enhanced. However, it is hard to find enough novice amputation patients to set up a study that reaches sufficient statistical power because the incidence of upper limb amputations is low. We therefore also examined experienced prosthesis users, because it may be assumed that prosthetic users have extensively trained the skills to handle a prosthesis at their affected side through the use of their own prosthesis. If these skills transfer to the other side, the prosthesis skills of the unaffected arm probably will be better than those skills in non-amputee novice prosthetic users (reverse effect). The aim of this study is to determine whether intermanual transfer effects can be demonstrated in persons with a transradial or wrist