Incidence of Clinically Documented Phantom Limb Pain During Hospitalization and Preoperative Risk Factors in Patients...

Background and Objectives: Phantom limb pain (PLP) frequently occurs after lower limb amputation (LLA). However, a consensus has not been reached regarding its incidence, particularly in nontraumatic amputations, because reported estimates vary according to case mix, follow-up duration, and outcome definitions. Data from Japan remain limited. Methods: After approval by the Institutional Review Board, the electronic medical records of patients who underwent above-knee amputation (AKA) or below-knee amputation (BKA) at Saitama Medical University Hospital between 1 January 2012 and 31 December 2024 were retrospectively reviewed. The primary outcome was the incidence of clinically documented PLP during hospitalization, typically within approximately 1-2 months after amputation. PLP was defined as a painful sensation in the amputated limb documented in the medical record and diagnosed by surgeons or anesthesiologists. Postamputation pain due to symptomatic neuroma was not classified as PLP. Patients with only nonpainful phantom limb sensations were not considered to have the primary outcome. Patients aged 18 years or older who required nontraumatic AKA or BKA were included. Patients who (1) died within 30 days of surgery or (2) were unable to communicate were excluded. Results: Clinically documented PLP occurred in 31 of 298 patients (10.4%; exact 95% CI, 7.2-14.4%) during hospitalization. In the prespecified primary model including age and preoperative pain, younger age (adjusted odds ratio (OR) 0.96 per 1-year increase, 95% confidence interval (CI) 0.93-0.99; p = 0.008) and preoperative pain (adjusted OR 16.34, 95% CI 3.75-71.24; p < 0.001) were associated with PLP. In an exploratory model additionally including postoperative pain on the day of surgery, postoperative pain was not independently associated with PLP. Firth penalized logistic regression yielded similar results. Conclusions: This study found a 10.4% incidence of clinically documented PLP during hospitalization after nontraumatic major LLA. Younger age and preoperative pain were associated with PLP, although the estimates should be interpreted cautiously because only 31 PLP events occurred.