Lateral Ulnar Collateral Ligament Reconstruction: An Analysis of Ulnar Tunnel Locations
We conducted a study to determine precise ulnar tunnel location during lateral ulnar collateral ligament reconstruction to maximize bony bridge and graft construct perpendicularity.
Three-dimensional computer models of 15 adult elbows were constructed. These elbow models were manipulated for simulated 4-mm tunnel drilling. The proximal ulna tunnels were placed at the radial head–neck junction and sequentially 0, 5, and 10 mm posterior to the supinator crest. The bony bridges created by these tunnels were measured. Location of the humeral isometric point was determined and marked as the humeral tunnel location. Graft configuration was simulated. Using all the simulated ulna tunnels, we measured the proximal and distal limbs of the graft. In addition, we measured the degree of perpendicularity of the graft limbs. The ulnar tunnel bony bridge was significantly longer with more posterior placement of the proximal tunnel relative to the supinator crest. An increase in degree of perpendicularity of graft to ulnar tunnels was noted with posterior shifts in proximal tunnel location. Posterior placement of the proximal ulna tunnel allows for a larger bony bridge and a more geometrically favorable reconstruction.
The study was limited by the number of patient-specific elbow models used. However, given the statistical consistency of measurements, sample size was sufficient. Another limitation, inherent to the model, was that only bony anatomy was incorporated. However, the overlying muscles, tendons, and ligaments can significantly alter tunnel placement, and this study provided other means and cues using more reliable landmarks to adequately place the tunnels. As this was a simulation study, we cannot confirm whether these results would make a difference clinically. The strengths of this study include development and verification of reliable landmarks that can be used to guide ulnar tunnel locations during LUCL reconstruction; these landmarks have been used for medial ulnar collateral ligament reconstruction.15 Other strengths include precise and accurate placement of tunnels and measurement of resulting bony bridges—accomplished independently and without compromising specimen quality.
Conclusion
We recommend drilling the proximal ulnar tunnel posterior to the supinator crest at the level of the radial head junction. A reasonable goal is 10 mm posterior to the crest, though the overlying soft tissue must be considered, and care should be taken to aim the drill anteriorly, toward the ulna’s intramedullary canal, to avoid posterior cortical breach. The distal ulnar tunnel should be drilled just posterior to the supinator crest, 15 mm distal to the radial head junction.
