1. The results suggest that over 90% of non- neuropathic LLAs have RFs for the heel and/or ball of the foot at 6 months post amputation or later. Younger LLAs seem to be more likely to have acquired RFs but Age does not seem to be a major contributing factor compared to YSA. It is not known if the LLAs classed as not having RFs did in fact have RFs that were difficult to find or if they would have eventually acquired fields. This could especially be true for the older LLAs. The authors plan to perform studies on LLAs to quantify possible improvements in balance and gait, possible decrease in phantom pain and the long term effects of using an electrical phantom stimulation system on RFs. They also plan on assessing neuropathic LLAs, which is particularly relevant as a lot of LLAs have diabetes. Other studies will involve assessing procedures for relocating RFs, training to acquire RFs and introducing the phantom stimulation system early in the rehabilitation phase. Receptive fields in lower limb amputees Alexandersson, A 1, Weber, KH 2, Lechler, K 1, Ingvarsson, T 1,3, Meier-Koll, A 2,4 1-Össur ehf, Reykjavik, Iceland; 2-CortXSenSorics GmbH, Spaichingen, Germany; 3-Faculty of Medicine, University of Iceland; 4- Forschungsstelle für experimentelle Ergo- und Physiotherapie, Friedrichshafen, Germany A complete map of the body surface exists in the somatosensory cortex and the map represents all body parts in a specific topographical order (Penfield and Rasmussen, 1950). If a limb is amputated, the cortical area previously devoted to the amputated limb suddenly becomes “silent”. This is followed by expansion of nearby representational areas into the “silent” areas. Ramachandran and Hirstein (1998) demonstrated cortical functional reorganization by evoking sensory phenomena in the missing limb of upper limb amputees when touching the forearm or face. They mapped out receptive fields (RF) with sharp margins for different hand areas. Simões et al. (2012) provided evidence that patients with amputated lower limbs show expanded cortical activation maps of the deafferented hemisphere that can also include the representation field of the corresponding upper limb. Meier-Koll and Weber (2013) demonstrated circumscribed RF sites representing distinct foot areas on seven lower limb amputees (LLA). The RFs were found both on the stumps and hands. Introduction The seven LLAs in the study by Meier-Koll and Weber were fitted with portable pulse generators that were controlled by two contact sensors located at the ball and the heel of the sole of a shoe. The corresponding RFs on the skin were stimulated with bipolar electrodes and phantom sensations of the ball and heel were triggered during standing and walking. The LLAs used the system at their homes several hours per day and reported effects such as improved prosthetic control and decreased phantom pain. Residual limb volume decreases over time, mostly due to decrease in oedema, until reaching relative stability at 4-6 months post-op (Sanders et al. 2011). After his preliminary evaluation of LLAs, Meier Koll noted that the majority seem to have acquired an RF for the foot at 6 months. The aim of the current study was to investigate the ratio of non-neuropathic LLAs with RFs for the heel and/or ball of the foot. Such information helps assess the possible benefits of a phantom stimulation system for the LLA population. 50 LLAs (transtibial, transfemoral, hip disarticulation, and hemipelvectomy) from Germany, Canada, USA and Iceland were assessed to determine if they were with or without RFs for the heel and/or ball of the foot. LLAs were mainly recruited from the Rehabilitationsklinik Bad Wurzach. Other LLAs were recruited from other clinical centres (orthopaedists, therapists, clinics and walking training centres) or referred for testing by clinicians. LLAs with diabetes, neurological disorders, and difficulties with mobility were excluded. A toothbrush or a watercolour paint brush were used for tactile stimulation to search for the RFs. Data on the age of LLAs (Age) and years since amputation (YSA) were collected. Logistic regression was used to analyse the relationship between the presence of an RF vs. the variables Age and YSA (binary variable: <0.5 years and ≥0.5 years). Statistical significance was defined as p-value < 0.05. Methods Discussion Conclusion The vast majority of non-neuropathic LLAs have acquired RFs for the heel and/or ball of the foot at 6 months post amputation. This suggests that a substantial number of LLAs could benefit from a phantom stimulation system. The logistics of providing such a personalized system to amputees and the presence of RFs in neuropathic amputees needs to be assessed. Meier-Koll, A. 2013. Penfield, W et al. The cerebral cortex of man: a clinical study of localization of function. 1950. Ramachandran, VS et al. Brain 121 (Pt 9). 1603-1630. 1998. Sanders, JE et al. J Rehabil Res Dev 48(8). 949-86. 2011. Simões, EL et al. J Neurosc 32(9). 3211-20. 2012. Receptive fields on a transfemoral amputee (Meier-Koll 2013) The average age was 58 years (range 25-80). The average YSA was 3.0 years (range 1 month – 13 years). The graph shows the results of the study. Each black circle represents an LLA. LLAs with RFs are represented with filled circles whilst LLAs without RFs are represented with empty circles. Two LLAs were measured more than once, represented with green and red circles. 40 LLAs (80%) had RFs. The highest YSA without an RF was 1.25 years. All 22 LLAs who had YSA more than 1.5 years had RFs. All 22 LLAs that were at or under 60 years of age had RFs. The LLAs that were measured more than once acquired RFs after initially not having them. 7 of 16 LLAs (37%) at less than 6 months after amputation (0.5 YSA) had an RF whereas 33 of 35 LLAs (94%) at 6 months or more had an RF. Results References Logistic regression showed that the coefficients of both Age (p=0.026) and YSA (binary variable: <0.5 years and ≥0.5 years, p=0.013) were statistically significant. The odds ratio for Age was 0.91 and 10.3 for YSA. Lower limb amputees with and without receptive fields Each black circle represents a lower limb amputee. Two were measured more than once (red and green circles)