Poster Number-68 - Targeted Muscle Reinnervation for the Treatment of Complex Regional Pain Syndrome in the Lower Extremity

Targeted Muscle Reinnervation for the Treatment of Complex Regional Pain Syndrome in the Lower Extremity

Purpose:

Complex regional pain syndrome (CRPS) is characterized by severe pain accompanied by vascular, motor, or trophic changes with a debilitating impact on patient quality of life. It’s varied clinical presentation and lack of treatment options make this disease a diagnostic and therapeutic challenge for physicians. Targeted muscle reinnervation (TMR) is a surgical technique that has been shown to improve phantom limb pain in lower extremity (LE) amputation, allowing for better post-amputation outcomes for patients. The objective of this case series was to characterize TMR as an adjunctive treatment for CRPS patients with LE amputation who are refractive to more conservative therapies.

Methods:

Patients were included if they had a diagnosis of CRPS in an upper extremity (UE) or lower extremity (LE) and elected to undergo TMR for CRPS management. Patient demographics, operative details, and functional outcomes were collected and compared pre- and post-operatively. Previous or concurrent treatments for pain management were also noted.

Pain was evaluated using Numerical Pain Rating Scale (NRS) values, collected during pre- and post-operative evaluations. Function of the affected limb was used as a proxy for pain interference, and assessed qualitatively based on patient-reported activity. Measures of central tendency were reported for appropriate variables.

Results:

There were 6 patients identified, all Caucasian women, with an average age of 32.5±15.4 years and body mass index (BMI) 24.9±5.0 kg/m² . CRPS was the indication for all amputations, done either before or during TMR. All patients were following with Pain Management at the time of TMR.

Patients 1 and 2 both carried a CRPS diagnosis due to LE trauma less than 1 year before TMR, for 4 and 11 months respectively. Patient 1 had a simultaneous amputation with TMR, while patient 2 had an amputation 11 months prior. Both patients were otherwise healthy and previously tried ketamine infusions to control their CRPS. They were followed for an average of 11±4.2 months after TMR procedure, and reported no change in their pain based on NRS pain assessments. Patient 1 did not have any previous nerve operations, while Patient 2 had a tibial nerve coaptation and saphenous neurectomy during amputation. At most recent follow up, Patient 1 reported complete resolution of pain and a decreased dose of their neuroleptic medication. Patient 2 continued to endorse generalized pain, but denied any resting leg pain (RLP) or phantom limb pain (PLP). Both Patients 1 and 2 were newly independently ambulatory 90 and 122 days after TMR, respectively, reporting the improvement in pain quality allowed them to tolerate a prosthetic.

The remaining four patients all carried a CRPS diagnosis due to trauma or a post-surgical etiology ranging from 3-8 years before TMR. They were all otherwise healthy, with exception of a Sjogren's (patient 3) and an Ehlers Danlos diagnosis (patient 4). Both of these patients had simultaneous amputation and TMR. Patients 5 and 6 had amputations beforehand, waiting 16 and 93 months, respectively. All had tried either ketamine infusions, spinal cord stimulation, DRG stimulation, or lumbar nerve blocks before TMR. When comparing pre- and post- TMR NRS values, all reported a 2-point increase with exception of patient 5, who maintained a score of 7 both before and after TMR. At most recent follow up, all patients endorsed generalized pain. All but patient 6 continued to endorse PLP after TMR. Of note, patient 6 had multiple neuroma excisions before TMR and reported a decrease in their narcotic dosage by most recent follow up. There were no changes between pre- and post- TMR ambulation status for these patients.

Conclusion:

CRPS is a debilitating condition with a variety of clinical presentations and treatment options. Operative management may be an option to control refractory CRPS pain when more conservative measures have failed. Due to high disease burden, patients should receive psychological and social support longitudinally through the disease course. The outcomes of these cases suggest that TMR may provide some benefit to reducing pain severity and improving function in patients with severe CRPS when utilized earlier in the disease course, though further prospective trials are warranted.

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