Referred pain from amputation stump trigger points into the phantom limb

OBJECTIVES: The aim of the study was to examine whether/how myofascial stump trigger points (TPs) after lower leg amputations are able to produce stump pain (SP), phantom pain (PP), and sensations (PS) in the phantom limb. METHODS: Palpation of the 5 most striking stump TPs of 30 leg amputees (12 transfemoral, 18 transtibial) was documented in a standardized manner. Patients were asked to localize SP, PP, and PS. RESULTS: Of 150 TPs, 14 produced involuntary stump movements and 10 stump fasciculations. Dorsal PP after ventral TP palpation occurred as well as PP in the toes from TPs near the hip. Of 30 patients, 20 reported PS and 8 PP; 60 of 150 TPs produced PS and 17 PP. Phantom phenomena were localized in 62.8% in the toes (1st toe 19.8%, toes 2-5 about 10% each), 17.9% midfoot, and the rest were more proximal. TPs were localized more in the lateral/dorsal stump than medial/ventral. About 70% of the TPs were found between 3 and 7 cm from the stump end, those with toe projections more distal than those with tibial projections. CONCLUSIONS: Myofascial TPs in amputation stumps are common and able to produce sensations and pain in the phantom limb. Most reported experiences were localized in the toes, as phantom pain usually is. There seems to be a "stump representation" and it seems possible that "referred TP pain" and "phantom pain" may develop from similar origin.