Residual Limb Morphological Changes Following Lower Extremity Amputations Including Agonist–antagonist Myoneural Interface Construction

Background: The agonist–antagonist myoneural interface (AMI) is a bi-directional neural communication platform created to augment volitional motor control, diminish pain, and restore proprioception. We have furthermore hypothesized that AMI construction may preserve limb volume. Objectives: To verify whether AMI construction leads to preserved residual limb volume in transtibial and transfemoral amputations. Study Design: Prospective cohort interventional study. Methods: Patients were recruited for transtibial (TTA) or transfemoral (TFA) amputations with AMI construction at Brigham & Women’s Faulkner Hospital between June 2016 and October 2025. Limb volume was estimated from serially collected circumferential measurements at distinct points along the limb over time. Results: Forty-seven modified amputations, including AMI construction, were performed in 40 patients over the course of the study. Forty (85%) were TTAs, while 7 (15%) were TFAs. Seven patients (18%) underwent bilateral amputations. The ratio of biological male to female patients was 58:42%, with a mean age of 39.5 ± 12.1 years and a mean body mass index of 26.9 ± 5.4 kg/m 2 . The average length of follow-up was 518 ± 598 days, with a range of 27–3109 days. The TTA and TFA cohorts demonstrated overall median limb volume preservation ratios of 1.00 ± 0.13 and 0.96 ± 0.09, respectively, with ratios of 0.94 ± 0.10 and 0.98 ± 0.11, respectively, noted in patients greater than 2 years post-surgery. Greater volume preservation was noted in the proximal portions of residual limbs. Bilateral amputees did not demonstrate volume preservation trends statistically different from those of unilateral amputees. Conclusion: AMI construction may offer the potential to preserve near-total long-term residual limb volume in TTAs and TFAs. Clinical Relevance: AMI construction may mitigate some of the long-term negative sequelae of lower limb amputation associated with muscle disuse atrophy.