Partial Hand Transplant: Lessons Learned from Cadaveric Dissections
Valeriy Shubinets, MD; Benjamin Chang, MD; L. Scott Levin, MD; Ines C Lin, MD, FACS
University of Pennsylvania, Philadelphia, PA
Introduction: As the field of vascularized composite allotransplantation continues to grow, new upper extremity transplant candidates are being considered on a regular basis. We recently evaluated a patient who had a mid-forearm level amputation and a contralateral metacarpal level amputation of digits with a preserved partial thumb. In the latter "partial hand" limb, native thumb was amputated at the proximal phalanx base with retained opposition and adduction, and the patient strongly desired to maintain these functions. Transplants at the hand level have reportedly been performed, but limited information exists on the technical details of such operation. This study aims to assess the feasibility of a partial hand transplant using cadaveric dissections, focusing on anatomic and functional concerns of a metacarpal-level transplantation.
Materials and Methods: Four cadaveric dissections were performed. A transplant approach was evaluated in which the donor hand would be fixated to the recipient hand at the metacarpal level, while attempting to preserve native innervation to adductor pollicis and thenar muscles. The distal donor thumb would be transplanted to the native thumb "en bloc" with the rest of the donor hand to improve thumb length. The vascular anastomoses would be performed at the distal forearm level (radial and ulnar arteries).
Results: Several concerns were realized during cadaveric dissections. Despite the use of CAD-CAM technology and patient-specific bone cutting guides, osteosynthesis for 4 metacarpals and thumb proximal phalanx was significantly more time-consuming than osteosynthesis for radius and ulna in the typical forearm transplant. Preserving the native thumb and thenar muscles required extensive dissection. Transplanting the distal donor thumb "en bloc" with the rest of the donor hand was challenging in terms of maintaining the distal donor thumb's blood supply. The recipient's intrinsic muscles also presented a challenge, as they were expected to be severed and atrophied. Certain structures such as palmar arches would have to be "doubled" if the anastomoses were performed at the distal forearm level, which added significant bulk to the final hand.
Conclusion: Based on our simulation dissections, mid-metacarpal partial hand transplantation with "en bloc" distal thumb transfer is associated with a tedious osteosynthesis and dissection, high risk of donor distal thumb ischemia, added bulk, and likely poor intrinsic muscle function. We thus recommend amputation and transplantation at the distal forearm rather than attempting to preserve the native proximal hand, particularly given the high rate of intrinsic muscle recovery in forearm-level transplant patients to date.
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