Patient Reported Outcomes Following Targeted Muscle Reinnervation

Residual limb pain and phantom limb pain (PLP) have been shown to be associated with decrease in prosthetic function and poor quality of life. It is estimated that the prevalence of PLP is as high as 85% and residual limb pain 10-76%. The treatment of amputee-related pain continues to rely largely on pharmacologic therapy, and typically opioids. Targeted Muscle Innervation (TMR) first performed by Dr. Dumanian, is a peripheral nerve transfer procedure that reroutes amputated axons to motor endplates and sensory organelles in nearby muscles, giving amputated nerves "somewhere to go and something to do" which may play a role in preventing development of neuromas and phantom limb pain.

A multicenter retrospective study found that upper-extremity amputees who subsequently underwent TMR ("secondary TMR") experienced relief in neuroma pain post-operatively. Other studies have shown that amputees who have undergone TMR have decreased narcotic use and improvement in prosthetic tolerance. A randomized controlled trial demonstrated that major limb amputees who underwent TMR had decreased phantom limb pain and residual limb pain compared with those who underwent traditional treatment of neuroma excision and burying into muscle. A subsequent study found that patients undergoing major limb amputation with immediate TMR ("primary TMR") had less PLP and residual limb pain than untreated amputee controls. A recent prospective study of patients undergoing TMR at time of major limb amputation secondary to trauma had overall low pain scores, and neuromodulator medication use and overall high rate of daily prosthetic use. Oncologic patients who underwent amputation with concurrent TMR demonstrated decreased neuroma symptoms, PLP and residual limb pain compared to oncologic amputees who did not undergo TMR. However, 32% of patients who underwent TMR for upper extremity amputation did not finish prosthetic rehabilitation, despite showing overall improved functional outcome scores.

Thus, there is increasing evidence that TMR, both primary and secondary, can prevent or improve pain from neuroma, phantom and residual limb pain. There is also evidence that TMR may promote early use of prosthetics and reduce reliance on narcotic medications. Prior studies have largely relied on outcome measures such as Numerical Rating Scale (NRS) for pain and pain-related instruments from the Patient-Reported Outcomes Measurement Information System (PROMIS) toolbox. More comprehensive data is limited on patient's functional status and quality of life, and thus far there is a lack of studies using patient-reported outcome instruments specific to patients with upper or lower extremity conditions. There is also limited data on patient desires and expectations for pursuing TMR, and subsequent satisfaction after having undergone the procedure.

Retrospective Cross-sectional study: Medical record review, electronic survey, optional interview This is a mixed methods, cross-sectional study assessing major limb amputee patients who have undergone TMR. It includes a medical record review to collect demographic information listed below, and an electronic survey (quantitative study), as well as interviews with a subset of subjects (qualitative study). Patients who have had at least 6 months follow up will be invited to participate in the electronic survey, which will include questions from validated patient-reported outcome instruments to measure function and quality of life. Patients will also be invited to be interviewed by phone using a set of open-ended questions. Thematic content analysis will be used to evaluate the participants' responses, and with the objective to examine the patient's motivations for undergoing TMR and their postoperative course, including pain, daily function, quality of life.

Prospective Cohort study: Medical record review, electronic survey, optional interview This is a mixed methods cohort study of patients with history of major limb amputation who will be undergoing secondary TMR, and patients who will be undergoing a major limb amputation with primary TMR. It includes a medical record review to collect demographic information listed below. The pre-survey will be administered between time of pre-operative evaluation to just prior to the operation, and the post-survey will be administered between 6-18 months after surgery. Each subject will also be invited to be interviewed by phone (or in person if at University of Wisconsin for follow up appointment), with set of open-ended questions focused on motivations for undergoing TMR, and their postoperative course including pain, daily function, quality of life.

General amputee population: Electronic survey ONLY To define normative data for general amputee population, the electronic survey with patient reported outcomes measures will be administered to amputees recruited from prosthetic, orthotic, orthopedic, vascular, oncologic or other amputee clinics and support groups.

For all above, the electronic survey, which will be administered via REDCap, will take approximately 7-8 minutes to complete. The interview will take 15-20 minutes to complete.

Study Aims:

• Aim 1: Evaluate functional status and quality of life of patients who have undergone primary or secondary TMR using patient reported outcome instruments
• Aim 2: Compare functional status and quality of life of primary TMR patients to those of general amputee population
• Aim 3: Compare pre-operative and post-operative functional status and quality of life of secondary TMR patients
• Aim 4: Compare post-operative functional status and quality of life of secondary TMR patients to those of general amputee population
• Aim 5: Evaluate patient desire, expectations and satisfaction with undergoing TMR (via survey and structured interview)