Nerve Transfer Explorer

The terminal AIN donor, pronator quadratus and separated ulnar motor pathway are schematic additions within a reference forearm. The atlas does not contain these dissected structures. The motor pathway is separated from the reference trunk for clarity; its position and the ETE division gap are illustrative. Individual motor fascicles and the epineurial window are not resolved. The mixed ulnar reference trunk is retained as context, not cut.

Native anatomy shows the terminal AIN supplying pronator quadratus before any division or coaptation. In SETS, this motor donor is divided distally near its entry into pronator quadratus. Its proximal end is coapted through a window to the side of the ulnar motor fascicular group in the distal forearm, preserving ulnar continuity. In ETE, the donor joins the distal cut end of the ulnar motor fascicular group. The proximal motor stump is disconnected, while the sensory components are preserved. Both transfers sacrifice the depicted AIN supply to pronator quadratus. The small distal AIN remnant at the muscle is omitted. The transitions compare completed configurations, not operative steps or regeneration. Arrowheads indicate potential motor input toward the depicted targets after reinnervation, not measured conduction, immediate postoperative function, axon counts or the relative contribution of either source. In SETS, both routes remain available; ETE interrupts the native motor route at the divided stump. The illustration shows distal routes only. The distal articular continuation of the AIN is not the donor depicted. Proximal branches to flexor pollicis longus and radial flexor digitorum profundus are outside this distal transfer.

Representative targets are first dorsal interosseous and adductor pollicis. In Targets, the copper route continues along the schematic recipient pathway into the reference deep motor branch. The highlight is visible through overlying tissue; its width is illustrative. It does not resolve individual donor axons, their distribution or recovery. Branch anatomy varies. This is an educational model, not an operative plan.

• Barbour et al. (2012): supercharged end-to-side AIN transfer.
• Mackinnon and Yee: AIN-to-ulnar motor transfer anatomy and technique.
• AIN-to-ulnar motor transfer: ETE and SETS operative techniques.
• Deep motor branch anatomy: adductor pollicis and first dorsal interosseous.
• Anatomical study: AIN distribution within pronator quadratus.

Upper-limb anatomy: Jan Kooloos, Eungyeol Lee and Open3DModel contributors. Open3DModel upper limb, CC BY-SA 4.0. Distal structures isolated from the source, recolored and made selectively transparent. The model remains available under the same license.