Targeted Muscle Reinnervation for Prosthesis Optimization and Neuroma Management Following Transradial Amputation
Sarah Pierrie, MD1; Glenn Gaston, MD2; Michael Gart, MD2; Bryan Loeffler, MD2
1Atrium Health, Charlotte, NC, 2OrthoCarolina Hand Center, Charlotte, NC
Introduction: Targeted muscle reinnervation (TMR) is an evolving surgical technique that involves the transfer of peripheral "donor" nerves that lost their motor targets at the time of amputation to traumatically or surgically denervated "target" muscles. Surface-level sensors within myoelectric prostheses detect contracting target muscles, providing motor control over functions that otherwise would be lost. TMR has been performed and studied primarily in transhumeral amputees. Clinical data about the adaptation of TMR to patients with transradial amputations is exceedingly scarce.
Materials & Methods: Adult patients who underwent forearm-level TMR concurrent with or following transradial amputation were identified from our institution's upper extremity amputation registry. Demographic and technical data were extracted from the medical record while patient-reported metrics were collected prospectively.
Results: Fifteen transradial amputees (8 men) with mean age 47.8 years underwent forearm TMR in 16 upper limbs (9 right, 7 left). Amputations were performed for pressor ischemia or gangrene (8), sequelae of trauma (6 cases), vascular insult (1), or wide excision of sarcoma (1). The dominant hand was affected in 9 cases. The median interval between amputation and TMR was 1 month; in 7 cases (43.8%), TMR was performed within 30 days of amputation. Neuromas were identified at the time of surgery in 6 cases (37.5%). A variety of TMR and nerve transfer patterns were employed. TMR targets exhibited palpable contraction at a mean of 2.7 ± 2.0 months after surgery. Seven patients (43.8%) experienced postoperative complications such as wound dehiscence, hematoma requiring surgical debridement, or persistent tenderness over the nerve coaptation site. Between 6 and 12 months post-operatively, the median in-prosthesis Disabilities of the Arm, Shoulder, and Hand score changed minimally, suggesting that the majority of functional gains are achieved early in the postoperative period and then plateau.
Conclusions: This is the largest reported series of patients undergoing forearm TMR to date. This procedure has the potential to improve early outcomes for patients with transradial amputations. Nevertheless, complications affect nearly half of these patients, so employing a multidisciplinary team approach is critical in this challenging patient population.
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