Lower Extremity Transplantation in Children

Ronald Zuker, The Hospital for Sick Children, Toronto, ON, Canada.

Key Learning Objectives:

1. Useful lower limb function can be anticipated following transplantation.
2. Coordinated, integrated activity of the transplanted limb is possible through the process of cortical reorganization or cortical plasticity, even when there was no limb at all at birth or there have been many years since the loss of the limb and transplantation.
3. Limb transplantation for children who have never had a limb should not be precluded on the basis that the cortical infrastructure is not available to control the limb.

Vascularized composite tissue allotransplantation continues to gain recognition and acceptance as a reconstructive option for complex defects that would have only suboptimal results using current techniques. New cases are being reported expanding our understanding of face, upper limb and laryngeal transplants. However, only one successful complete lower limb transplantation has been reported to date.

A functioning limb from one ischiopagus twin with an irreparable and lethal cardiac anomaly was transplanted to her surviving sister, who would otherwise have only one limb. The transplant was secured, revascularized, and reinnervated. Six years post transplant, after tendon adjustments and soft tissue realignment, she is mobilizing well, interacting normally with her peers in a mainstream school, and even engaging in sporting activities.

This report will outline our detailed clinical evaluation. The transplanted limb was shorter than the normal limb, leading to a pelvic tilt. There was good power at the hip and knee, but ankle dorsiflexion was limited. The transplant was pain free and demonstrated sensation throughout. It was virtually normal distally. She agreed to a structured interview which revealed no psychological issues and normal social integration. She completed two subjective assessments, the validated SF-36 and the Lower Extremity Functional Scale (LEFS), and scored high on both. On the SF-36 she scored 66.9% and on the LEFS she scored 86.25%, indicating minimal functional impairment.

Although this child had no normal right leg at birth, she is now able to integrate the transplant into coordinated, seamless function. She has demonstrated cortical plasticity whereby the cerebral cortex has become rearranged to capture the function of the transplanted leg. The implications for VCTA for children who may never have had a limb or in whom the limb has been absent for years is profound, as cortical plasticity will allow for normal integration of function. The possibility of VCTA should not be precluded on the basis that the cortical infrastructure is not available to control the limb.