Abstract
Medial and posterolateral rotational instability of the elbow, often resulting from collateral ligament insufficiency, can lead to pain and functional impairment. Surgical re-construction is indicated when conservative treatment fails, yet complications such as graft failure and donor-site morbidity persist. This study investigates the anatomic and biomechanical feasibility of the Shark Screw tendon as a representative human allogeneic bone screw for humeral ligament fixation in cases of elbow instability. Eight fresh-frozen cadaveric specimens were used to evaluate the feasibility of the use of a Shark Screw tendon for humeral fixation on both medial and lateral sides. Cyclic loading and failure testing were performed to assess time-zero fixation characteristics and failure load. A total of sixteen testing scenarios were conducted on the specimens. Implantation was technically feasible without anatomic limitations related to implant size or positioning. Six graft failures occurred (38%), all attributable to poor tissue quality. Tendon slippage was observed in 9 of 16 cases (56%) under progressively increasing axial load, while the Shark Screw tendon remained seated. The mean failure load was 101 N (±50) for medial insertions, 118 N (±77) for lateral insertions, and 110 N (±64) overall. After 100 cycles, tendon displacement averaged 1.1 mm (±0.4) during extension-flexion on the medial side, 1.0 mm (±1.0) on the lateral side, and 1.0 mm (±0.7) overall. During supination-pronation, displacement was 0.8 mm (±0.7) medially, 1.0 mm (±0.8) laterally, and 0.9 mm (±0.7) overall. No anchor pullout was observed, although one anchor tip fractured during insertion. The Shark Screw tendon appears to be a feasible biologically integrative alternative for humeral fixation in medial and posterolateral elbow ligament re-construction, demonstrating preliminary time-zero fixation characteristics in a cadaveric model. Further biomechanical and clinical studies are needed to confirm long-term outcomes.