Ulrika Wijk, Pamela Svensson, Christian Antfolk, Ingela K. Carlsson, Anders Björkman, Birgitta Rosén
Department of Translational Medicine, Hand Surgery, Lund University, 20205 Malmö, Sweden. E-mail: ulrika.wijk@med.lu.se
DOI: 10.2340/16501977-2518

Objective: Currently available hand prostheses lack sensory feedback. A “phantom hand map”, a referred sensation, on the skin of the residual arm is a possible target to provide amputees with non-invasive somatotopically matched sensory feedback. How-ever, not all amputees experience a phantom hand map. The aim of this study was to explore whether touch on predefined areas on the forearm can be associated with specific fingers.
Design: A longitudinal cohort study.
Subjects: A total of 31 able-bodied individuals.
Methods: A “tactile display” was developed consisting of 5 servo motors, which provided the user with mechanotactile stimulus. Predefined pressure points on the volar aspect of the forearm were stimulated during a 2-week structured training period.
Results: Agreement between the stimulated areas and the subjects’ ability to discriminate the stimulation was high, with a distinct improvement up to the third training occasion, after which the kappa score stabilized for the rest of the period.
Conclusion: It is possible to associate touch on intact skin on the forearm with specific fingers after a structured training period, and the effect persisted after 2 weeks. These results may be of importance for the development of non-invasive sensory feedback systems in hand prostheses.

A drawback of currently available hand prostheses is the lack of sensory feedback. Some amputees experience a feeling of touch of the amputated hand when the residual limb is touched. This kind of referred sensation is called “phantom hand map”. However, not all amputees experience “phantom hand map”. Therefore, we examined whether touch on predefined areas on the forearm can be associated with specific fingers in individuals with an intact arm, using a tactile display during a 5-week training period. In conclusion, it is possible to learn to associate touch on predefined areas on the forearm with specific fingers after a structured training period, and the effect persisted after 2 weeks. These results may be of importance for the development of non-invasive sensory feedback systems in hand prostheses.