Adductor magnus muscle transfer to restore knee extension: Anatomical studies and clinical applications

Background: Loss of knee extension causes significant impairment. Though nerve-based reconstruction is preferable in cases of femoral nerve palsy or injury, these surgeries are not always appropriate if the pathology involves the quadriceps muscles or presentation too late for muscle reinnervation. Muscle transfers are another option that has been underutilized in the lower extremity. We describe the successful restoration of knee extension by adductor magnus muscle transfer without functional donor morbidity, along with anatomical considerations. Methods: Ten fresh frozen cadaveric lower limbs were dissected at the groin and thigh. In addition, three patients presented with femoral nerve palsy for which nerve-based reconstruction was not appropriate because of late presentation. In these patients, adductor magnus muscle transfers were performed, along with sartorius, gracilis, and tensor fasciae latae transfers if available and healthy. Results: In cadavers, the pedicle for the adductor magnus is at the level of the gracilis and adequate for muscle transfer, with sufficient weavable tendon length. The only major structure at risk is the femoral neurovascular bundle, which is in a reliable anatomic position. Two patients recovered 4/5 active knee extension and ambulation without assistive devices. A third required reoperation for a loosened tendon weave, after which the noted improved stability and strength with ambulation but did not regain strong active knee extension and continued to require a cane. Conclusions: We present a novel reconstructive approach for loss of quadriceps function in patients, which yields good clinical outcomes, with anatomic and technical details to demonstrate the utility of this technique. Ongoing evaluation of optimal technique and rehabilitation to maximize functional outcomes is still needed.