Human Implementation of Upper Extremity Amputation Incorporating Agonist–Antagonist Myoneural Interface Construction

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. Previous studies that included AMI construction in lower extremity amputation have demonstrated multiple benefits over standard methods of lower limb amputation. The authors present their experience with modified surgical approaches to upper extremity transradial amputation (TRA) and transhumeral amputation (THA) that incorporate AMI constructs. Methods: – Modified upper extremity amputation procedures were performed in a patient cohort at Brigham & Women’s Hospital or Walter Reed National Military Medical Center. Prospectively collected outcomes included clinical, functional, and sensorial measures. The results were tabulated and analyzed. Results: – Seven modified upper extremity amputations were performed: 5 TRAs (71%) and 2 THAs (29%). All patients had trauma-related amputations, and the majority of patients were men (6 [86%]), with a median age at amputation of 42.0 ± 19.5 years. The median operative time was 399 ± 23 minutes for TRA and 670 ± 85 minutes for THA. At the 12-month postoperative encounter, patients had preserved nearly all of their residual limb volume, retaining a median of 97% of their preoperative limb size (±5%). The reconstructed muscle units demonstrated a median excursion of 6 mm (±1 mm). Antagonist muscle strain and agonist muscle activation were strongly correlated. Eighty-three percent of patients reported resolution of preoperative limb pain and experienced functional phantom limb perception. Conclusion: – The incorporation of AMI construction into upper extremity amputation procedures may provide benefits similar to those observed in patients with lower extremity amputations who have undergone equivalent AMI interventions.