Experience to date with elective transfemoral amputations incorporating agonist-antagonist myoneural interface (AMI) design

Introduction: The agonist-antagonist myoneural interface (AMI) is a surgical construct that, when incorporated into limb amputation, offers to potential to preserve or restore proprioception, augment functionality, reduce neuropathic pain and enhance overall limb stability. We here present our experience to date with AMI construction in the context of transfemoral amputation (TFA). Methods: Patients were recruited for TFA with AMI construction at Brigham & Women's and Brigham & Women's Faulkner Hospital between June 2018 and June 2023. Data collection included demographic information, intraoperative parameters, clinical recovery metrics and complications. All data was then collated and analyzed. Results: Seven TFA procedures were performed on seven patients during the study period. The operative technique employed evolved significantly over time, and included the development of both native and regenerative AMI models. Four patients were biological males (57%), and mean patient age was 42.0 ± 14.6 years. The etiology of conditions necessitating amputation included traumatic (43%), oncologic (29%), iatrogenic (14%) and congenital (14%). Mean operative time was 566 ± 97 min and average length of stay was 11.7 ± 8.4 days. Average postoperative follow-up was 2.19 ± 1.57 years (range 0.81–4.30 years). Postoperative imaging of AMI constructs demonstrated average muscle excursions of 6±3 mm, and total average limb volume preservation over time was 102 ± 14%. All patients demonstrated a complete wean from narcotic pain medications, with a mean time to wean of 86 ± 79 days. Minimal neuropathic pain was reported after the acute postoperative period. All seven (100%) of the subjects reported functional phantom limb sensation over the same time. Complications included significant soft tissue necrosis in two (29%) patients and minor wound healing issues in one (14%) patient. Conclusions: TFA incorporating AMI construction appears to offer promising benefits similar to those previously reported in patients undergoing similar interventions at the transtibial level.