Static stability of novel uncemented elbow hemiarthroplasty stabilized with ligament reconstruction

Background: The purpose of this study was to create a model to simulate treatment of unreconstructable distal humerus fractures with hemi-arthroplasty. Stability was restored with a latest plate-system that simultaneously tensions medial and lateral collateral ligament grafts.Materials and methods: Static varus and valgus elbow stability was tested in 11 cadaver elbows with intact ligaments and capsule at 5 flexion angles (0 degrees, 30 degrees, 60 degrees, 90 degrees, 120 degrees). The elbows were then destabilized via release of all ligaments and capsular attachments. The distal humerus articular cartilage was excised and replaced with an uncemented hemiarthroplasty. Ligament reconstruction was subsequently performed, and elbow stability was measured and compared to the native state. Dimensions of the hemiarthroplasty component were compared to native elbow dimensions to assess and quantify any existing relationship to elbow stability.Results: A hemiarthroplasty was implanted in all specimens. A size mismatch occurred between the distal humerus trochlea and the olec-ranon fossa in all specimens and averaged 6.3 mm. Following ligament reconstruction, specimens reproduced the flexion angle-dependent stability of native elbows to both varus and valgus stress. On the medial side, elbow joint stability in mid-flexion was approximately 7% tighter after hemiarthroplasty. Laterally, the elbow was approximately 15% tighter after hemiarthroplasty and demonstrated peak stability in full flexion. The 3 assessed hemiarthroplasty components and bony dimensions did not exhibit any relationship between implant-bone mismatch and elbow stability after ligamentous reconstruction.Conclusion: Cadaveric elbow specimens underwent uncemented hemiarthroplasty with soft tissue stabilization with a novel technique for ligament reconstruction. Following hemiarthroplasty and ligament reconstruction, these specimens maintained secure fixation between lig-ament and bone. Static stability was maintained at varying degrees of elbow flexion regardless of variable mismatch between the hemi-arthroplasty component and the native olecranon fossa.Level of evidence: Basic Science Study; Biomechanics (c) 2023 Journal of Shoulder and Elbow Surgery Board of Trustees. All rights reserved.