Elbow Uncemented Hemiarthroplasty: Surgical Technique

Computed Tomography-Based Humeral Templating for Uncemented Elbow Arthroplasty

BACKGROUND

Intramedullary (IM) screw insertion into the distal humerus provides fixation for a novel, uncemented elbow arthroplasty. A multitude of screw sizes is required to accommodate variable humeral morphology. The goal of this study was to use computed tomography (CT) for IM screw sizing and to validate this templating by inserting screws into three-dimensionally (3D) printed models.

METHODS

Computed tomography humerus scans for 30 patients were reformatted in the plane of the distal IM canal. Screw size was templated by measuring the canal diameter at 3 locations corresponding to the lengths of the screws being tested. Interrater and intrarater reliabilities of the measurements were assessed. Three-dimensional models of 5 humeri were printed, and IM screws were placed to achieve a secure endosteal fit.

RESULTS

We identified combinations of body components and IM screw length and diameter for all patients to seat this uncemented elbow arthroplasty. The measurements and screw width determinations were reliable. Canal diameter correlated with age but was unrelated to sex. Screws were inserted into five 3D-printed models which matched the templates and demonstrated mechanical and radiographic evidence of secure fit.

CONCLUSIONS

This study characterizes distal humerus anatomy in the context of IM screw fixation. Humerus CT scans of 30 patients were able to be templated, and validation via implantation of IM screws into 3D models was successful. Computed tomography templating will allow surgeons to predict the optimal screw size prior to implantation. A broad range of screw lengths and diameters is critical for implantation of this novel elbow arthroplasty.

Static Stability of Elbow Interposition Arthroplasty Stabilized With Novel Ligament Reconstruction

BACKGROUND

Outcomes of interposition arthroplasty for treatment of elbow arthritis are highly dependent on elbow stability. The purpose of this study was to determine whether interposition arthroplasty with a novel bidirectional ligament reconstruction technique could adequately restore the static stability of the native elbow.

METHODS

Static varus and valgus elbow stability was tested in 7 cadaver elbows with intact ligaments and capsule at 5 flexion angles (0°, 30°, 60°, 90°, and 120°). At each angle, the distance between fixed reference points across the elbow was measured both medially and laterally. The elbows were then destabilized and an interposition arthroplasty with ligament reconstruction was performed. Static elbow stability was reassessed by comparing postoperative deflection measurements with those of the native state. Graft slippage or loosening was visually assessed following testing.

RESULTS

Interposition arthroplasty was performed in 7 cadaver specimens. Following ligament reconstruction, specimens reproduced the flexion angle-dependent static stability of native elbows to both varus and valgus stress. The greatest deflection changes between native elbows and elbows after interposition arthroplasty were 2.7% (P = .13) medially and 2.3% (P = .42) laterally, which were not significant. There was no loosening or slippage of either the interposition graft or the ligament reconstruction grafts.

CONCLUSIONS

Cadaveric elbow specimens underwent interposition arthroplasty with a novel technique for bidirectional ligament reconstruction. Static stability was maintained at varying degrees of elbow flexion, comparable to that of the native elbow. Interposition and ligament reconstruction grafts maintained secure fixation following static biomechanical testing.