Anatomic feasibility of using Shark Screw tendon for humeral ligament re-construction in medial and posterolateral elbow instability.

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSION

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.