Paper 12: Biomechanical Comparison of Anatomic Restoration of the Ulnar Footprint Versus Traditional Ulnar Tunnels in Ulnar Collateral Ligament Reconstruction

Abstract

Objectives:Current techniques for ulnar collateral ligament (UCL) do not reproduce the anatomic ulnar footprint of the UCL. The purpose of this study was to describe a novel UCL reconstruction technique that utilizes proximal-to-distal ulnar bone tunnels to better recreate the anatomy of the UCL and compare the biomechanical profile at time zero between this technique, the native UCL, and the traditional docking technique. Our hypothesis was that the biomechanical profile of the anatomic technique is similar to the native UCL and traditional docking technique.Methods:Ten matched cadaveric elbows were potted with the forearm in neutral rotation. The palmaris longus tendon graft was harvested, and bones were sectioned 14 cm proximal and distal to the elbow joint. Specimen testing included: (1) native UCL testing performed at 90° flexion with 0.5 Nm valgus moment preload, (2) cyclic loading from 0.5-to-5 Nm valgus moment for 1000 cycles at 1 Hz, and (3) load to failure at 0.2 mm/s. Elbows then underwent UCL reconstruction with one elbow of each pair receiving the classic docking technique using either anatomic (proximal-to-distal) or traditional (anterior-to-posterior) tunnel locations. Specimen testing was then repeated, as described above.Results:There was no difference between maximum load at failure or valgus angle between the anatomic or traditional tunnel location techniques (34.90 ± 10.65 Nm vs. 37.28 ± 14.26 Nm, P = 0.644) or the native UCL (45.83 ± 17.03 Nm, P = 0.099). Additionally, there was no difference in valgus angle after 1000 cycles across the anatomic (4.58 ± 1.47°), traditional (4.08 ± 1.28°), or native UCL (4.07 ± 1.99°). Anatomic group and the native UCL had similar valgus angles at failure (24.13 ± 5.86° vs. 20.13 ± 5.70°, P = 0.083), while the traditional group had a higher valgus angle at failure compared to the native UCL (24.88 ± 6.18° vs. 19.44 ± 5.86°, P = 0.015).Conclusions:UCL reconstruction with the docking technique utilizing proximal-to-distal ulnar tunnels to restore the anatomic ulnar footprint better recreates the anatomy of the UCL while providing valgus stability comparable to reconstruction with docking technique using traditional anterior-to-posterior ulnar tunnel locations. These results suggest that utilization of the anatomic tunnel location in UCL reconstruction has similar biomechanical properties compared to the traditional method at the time of initial fixation (i.e., not accounting for healing following reconstruction in vivo) while keeping the ulnar tunnels further from the ulnar nerve. Further studies are warranted to determine if an anatomically based UCL reconstruction results in differing outcomes compared to traditional reconstruction techniques.