7. Upper Limb Transplantation at Proximal Forearm Level: The Donor Muscle Sleeve Technique

Background: Optimal results in hand and upper limb transplantation require comprehensive assessment of immune and physical matching criteria, and careful consideration of the anatomical requirements of each patient. A core principle of the UK Hand and Upper Limb (HAUL) program is that, in the event of transplant loss, recipients should not be left at a substantial functional disadvantage in comparison to their pre-transplant condition. In this context, transplantation at proximal forearm level is challenging. Proximal to the tendons, muscle coaptation is unreliable, and while proximal revision and transhumeral transplantation would offer the functional benefit of intact donor forearm muscle-tendon units, subsequent re-amputation would leave the patient significantly disadvantaged. Instead we aim to conserve enough forearm skeletal length to drive a prosthesis if required. We present the donor muscle sleeve (DMS) technique as our approach to such cases. Methods: The UK HAUL-Tx cohort includes two patients with bilateral proximal forearm amputations transplanted using the donor muscle-sleeve technique. The surgical technique and outcomes will be presented in detail. Briefly, the recipient dissection commences with design and elevation of interdigitating skin flaps. The median, ulnar and radial nerve motor and sensory branches are identified, dissected and tagged. Pronator teres and the deep belly of supinator are preserved with their innervation. All remaining residual forearm musculature is excised. Radial and ulnar terminal osteotomies are freshened with minimal shortening beyond the junction of proximal and distal third forearm. Donor limbs are retrieved by transhumeral amputation, flushed, chilled and packaged for transfer according to standard protocols. Dissection subsequently proceeds with elevation of corresponding skin flaps, and dissection of median, ulnar and radial nerve motor and sensory branches. The flexor and extensor muscles are elevated en masse from their origins. Brachioradialis is preserved, and pronator teres and supinator excised. Required skeletal length is determined and osteotomies performed. Following osteosynthesis the donor flexor and extensor origins, and brachioradialis, are fixed with bone anchors and periosteal sutures to secure the muscle sleeve. The limb is reperfused by anastomosis of the brachial artery, venae comitantes and superficial veins, and targeted motor and sensory nerve coaptations performed. Results: Two individuals have undergone DMS transplant technique, with 8 and 3 years follow-up. Psychosocial and immunological outcomes are comparable to overall cohort means. Functional recovery relies on reinnervation of the donor muscles, and therefore progresses more slowly than more distal-level transplants. Recordable grip strength on dynamometer is first seen at the end of year 2 and year 1 respectively, with slow continued increase and plateauing at year 5 post-operatively in the individual with 8 years follow up. Canadian Occupational Performance Measure - Satisfaction (COPM-S) scores improved from 1.8 & 2.5 to 3.25 and 6.4 respectively post-transplant. Performance score (COPM-P) improved from 1.8 and 3.1 to 2.25 and 5.0. Recovery of sensation and strength have been sufficient for functional integration of the limbs and both have returned to independent self care and leisure activities. Conclusion: The donor muscle sleeve technique facilitates transplantation of the proximal-forearm level amputee with preservation of skeletal length which could be resurfaced in the event of transplant loss, preserving pre-transplant functional capacity with prosthesis.

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