Carty, Matthew J.; Fernandez, Michael F.; Sullivan, Corey L.; Chiao, Rachael; Berger, Lori; Sparling, Tawnee L.; Souza, Jason M.; Potter, Benjamin K.; Beltran, Luis; Herr, Hugh M. Human Implementation of Upper-Extremity Amputation Incorporating Agonist-Antagonist Myoneural Interface (AMI) Construction. Plastic and Reconstructive Surgery, December 12, 2025. | DOI: 10.1097/PRS.0000000000012642

Abstract

Background: 

The agonist-antagonist myoneural interface (AMI) is a mechanoneural construct in which naturally opposed, innervated muscles are surgically linked to recapitulate the neural feedback loops present in intact human anatomy. Prior studies in which AMI construction has been incorporated into lower-extremity amputation have demonstrated multiple benefits over and above standard approaches to lower limb sacrifice. We here present our experience with modified surgical approaches to upper-extremity amputation at the transradial (TRA) and transhumeral (THA) levels that incorporate AMI constructs.

Methods: 

Modified upper-extremity amputation procedures were performed in a patient cohort at Brigham & Women’s Hospital (BWH) or Walter Reed National Military Medical Center (WRNMMC). Prospectively collected outcomes included clinical, functional, and sensorial measures. Results were tabulated and analyzed.

Results: 

Seven modified upper-extremity amputations were performed: 5 (71%) TRA and 2 (29%) THA. All patients sustained trauma-related amputations and the majority of patients were male (6, 86%), with a median age at amputation of 42.0±19.5 years. Median operative time was 399±23 minutes for TRA and 670±85 minutes for THA. At the 12-month postoperative encounter, median residual limb volume preservation was measured at 97±5% of the preoperative state and median construct excursion was 6±1 mm. Antagonist muscle strain and agonist muscle activation were strongly correlated. Eighty-three percent of patients reported resolution of preoperative limb pain and the presence of functional phantom limb perception.

Conclusions: 

The incorporation of AMI construction into upper-extremity amputation procedures may provide benefits similar to those witnessed in persons with lower-extremity amputation who have undergone equivalent AMI interventions.