Mechanical Pain Sensitivity in Postamputation Pain

Abstract

Objectives: Postamputation, clinical markers of pain-related peripheral and central nervous system hypersensitivity remain understudied. This study aimed to identify whether adults with postamputation pain demonstrate greater pain sensitivity in primary (ie, amputated region) and secondary (ie, nonamputated region) sites, as compared with painfree peers and controls with intact limbs.Methods: Ninety-four participants postunilateral, transtibial amputation (59 with pain, 35 pain-free) and 39 controls underwent pain-pressure threshold (PPT) testing at 10 sites. Pain-pressure thresholds were normalized to sex-specific control data using Z score conversions. Normalized primary-site and secondary-site PPTs were compared between groups using multivariate analysis of variance (P < 0.050).Results: Compared with pain-free peers, adults with postamputation pain demonstrated reduced normalized PPTs across primary and secondary sites (mean difference = 0.61-0.74, P = 0.001 to 0.007). Compared with controls, adults with postamputation pain demonstrated reduced normalized PPTs (mean difference = 0.52, P = 0.026) only at primary sites.Discussion: Adults with postamputation pain demonstrate greater amputated region pain sensitivity as compared with pain-free peers or controls with intact limbs, indicating peripheral sensitization persists even after limb healing. Secondary-site pain sensitivity was similar between controls and adults with postamputation pain, suggesting central nervous system hypersensitivity may not be ubiquitous with postamputation pain. Studies are needed to investigate mechanisms underlying pain sensitivity differences between adults with and without postamputation pain.

Post‐amputation pain: Comparing pain presentations between adults with and without increased amputated‐region sensitivity

“…Then, for adults with post‐amputation pain, PPTs at each site were normalized (i.e., z ‐transformed) based on their relative standing within sex‐specific control groups. This conversion has been previously published 14 and allowed comparison of participants with lower‐limb loss to sex‐specific reference data (as it is well‐established that females demonstrate greater pain sensitivity as compared to males 35 ). Amputated‐region pain sensitivity was computed as the average of normalized residual patellar tendon and residual lateral femoral epicondyle PPTs.…”

“…Persistent post‐amputation pain appears to have peripheral contributions, as individuals with post‐amputation pain demonstrate greater amputated‐region pain sensitivity than pain‐free peers with and without limb loss 14 . Furthermore, PLP has been shown to improve following dorsal root ganglion injections, 8 and associations have been identified between pre‐amputation limb pressure sensitivity and early post‐amputation pain severity 15 .…”

“…Persistent post-amputation pain appears to have peripheral contributions, as individuals with postamputation pain demonstrate greater amputated-region pain sensitivity than pain-free peers with and without limb loss. 14 Furthermore, PLP has been shown to improve following dorsal root ganglion injections, 8 and associations have been identified between pre-amputation limb pressure sensitivity and early post-amputation pain severity. 15 What is less known, however, is whether amputated-region sensitivity reflects patterns of peripheral sensitization in isolation, or if it may reflect underlying central sensitization among individuals with post-amputation pain.…”