Surgical Treatments for Postamputation Pain

This is a double-blind randomised controlled trial (RCT) which compares the effectiveness of three surgical techniques for alleviating residual limb pain (RLP), neuroma pain and phantom limb pain (PLP). The three surgical treatments are Targeted Muscles Reinnervation (TMR), Regenerative Peripheral Nerve Interface (RPNI), and an active control (neuroma excision and muscle burying). Patients will be follow-up for 4 years.

Residual limb pain (RLP), neuroma pain, and phantom limb pain (PLP) can develop after the loss of a body part and fall within the umbrella term postamputation pain. However, the underlaying causes to postamputation pain are diverse and must be addressed accordingly. Surgical treatments for RLP have become a popular approach and have shown great potential for successful outcomes. The two surgical interventions, Targeted Muscle Reinnervation (TMR) and Regenerative Peripheral Nerve Interface (RPNI), are globally used in pain management therapies. This is a multi-centre, double-blind, superiority RCT which takes place at 9 hospitals in 7 countries:the Sahlgrenska University Hospital in Gothenburg, Sweden; the Rizzoli Orthopaedic Institute in Bologna, Italy; the University of Alberta Hospital in Edmonton, Canada; Worker Hospital in Santiago, Chile; the NHS Lothian, NHS Clyde \& Greater Glasgow, and NHS Grampian, UK; Dandenong Hospital, Monash Health in Melbourne, Australia; the Northwestern Memorial Hospital in Chicago, USA; the University of Michigan Health System in Ann Arbor, Michigan, USA; and within the Massachusetts General Hospital in Boston, USA. One hundred ten participants will be recruited and randomly assigned to one of three surgical treatments (TMR, RPNI, or control) in an equal allocation ratio (n = 37 per group). Each participant will be followed up short term (1, 3, 6, and 12 months post-surgery) and long term (2 and 4 years post-surgery). After the 12-month follow-up, the study will be unblinded for the evaluator and the participants. If the participants are unsatisfied with the outcome of the treatment, they may request one of the other treatments. In such a case, a medical evaluation and further treatment options will be discussed in consultation with the clinical investigator at the site. The study design is chosen to be able to follow RLP, neuroma pain and PLP intensity before and after surgical treatment as well as to investigate how pain develops up to four years post-surgery. The evaluation methods in the study are based on previously used methods in the literature for RLP-, neuroma- and PLP-related pain research. The questionnaires are previously used in clinical settings.

Inclusion Criteria: * The participant must have a major limb amputation. * The participant is ≥ 18 years old at the time of consent. * The participant must be in generally good health to undergo a surgical intervention, as per the clinical investigator's opinion. * Time since the last amputation must be over a year at the time of consent. * The participant must have an average residual limb pain score equal or greater than 4 on the Numerical Rating Scale (NRS, 0-10) after the baseline period. * If the participant has been prescribed pharmacological treatments for pain, there must be no variations in dosage (steady consumption) for at least 1 month before the screening visit. * If the participant has been prescribed non-pharmacological treatments for pain, such as spinal cord stimulation, transcutaneous electrical nerve stimulation, and mirror therapy, the treatment must have ended at least 1 month before the screening visit. * The participant must have a stable prosthetic fitting for at least a month before the screening visit. * The participant has a sufficient understanding of the language in which the assessments will be conducted, as per the clinical investigator's opinion. Exclusion Criteria: * Neurological or other conditions that affect nerve regeneration for the nerve to be treated. * Active infection in the residual limb. * Prior RPNI or TMR surgery of the nerve to be treated (with painful neuroma) to address postamputation pain. * Mental disorders (e.g., schizophrenia, paranoia, psychosis, etc.), reluctance, or language difficulties that result in difficulty understanding the meaning of study participation. * Ongoing participation in a clinical study that the clinical investigator deems detrimental to participation in this study.