Static Stability of Elbow Interposition Arthroplasty Stabilized With Novel Ligament Reconstruction

Abstract

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.

Keywords: allograft interposition; collateral ligaments; elbow arthritis; elbow biomechanics; elbow instability; elbow interposition arthroplasty; ligament reconstruction.

Figure 1.

Schematic representation of the cylindrical ligament retention device (CLRD) (a) and cross-locking plate, screw, and nut (b) designs. The CLRD is implanted within the distal humerus and utilizes 2 grafts, 1 medial and 1 lateral, which are tensioned symmetrically and locked in to the proximal ulna with aggressively teethed plates. These plates are designed to compress the ligament grafts to bone and to contour to the irregular topography of the proximal ulna.

Figure 2.

Interposition arthroplasty technique. Denude distal humerus articular cartilage. Drill 4 bone tunnels through the supracondylar humerus and 2 bone tunnels through the olecranon fossa. Load the Achilles allograft with 3 sutures. Position the allograft over the distal humerus and pull the loaded sutures through the supracondylar drill holes such that the limbs of each suture are separated by a bone bridge. Pass another suture through the allograft at the level of the olecranon fossa holes and pass these through their corresponding holes. Using a free needle, pass all suture tails through the other side of the Achilles allograft. Tie down all sutures to secure the allograft to the distal humerus.

Figure 3.

Cylindrical ligament retention device (CLRD) technique. Identify the centerline of rotation of the distal humerus by placing a Kirschner wire (K-wire) at the center of the capitellum laterally and the anterior inferior aspect of the medial epicondyle medially. Use the drill guide to place a second, parallel K-wire on either side. Remove the first set of K-wires and drill over the second set of K-wires, connecting the tunnel centrally. Identify the supinator crest and use the custom drill guide to drill 2 transverse drill holes across the proximal ulna. Apply and secure the ligament reconstruction plates with the transulnar bolts and nuts. Harvest ligament reconstruction grafts and load them into the CLRD. Implant the CLRD within the distal humerus. With the interpositional Achilles graft applied and the elbow reduced, apply a total pull of 80 N across the ligament grafts and tighten the bolts and nuts, securing the grafts to the ulna. Cut the prominent portions of the bolts and close the soft tissue sleeves and native ligaments over the subcutaneous ulna. Closure was not performed in this biomechanical study in order to maintain access to the reference points.

Figure 4.

Elbow deflection measurements between 2 fixed medial and lateral reference points throughout the range of motion is quantified for 0°, 30°, 60°, 90°, and 120° of elbow flexion on the medial (a) and lateral (b) sides under 13.3 N of valgus and varus stress, respectively, for native elbows and elbows after interposition arthroplasty with ligament reconstruction, and normalized by deflection of the native elbow at 0° of elbow flexion. Normalized deflection is compared between the medial and lateral sides for native elbows (c) and elbows after interposition arthroplasty with ligament reconstruction (d). Percent change from the native elbow at various flexion angles after interposition arthroplasty with ligament reconstruction (e). Statistics are performed using 2-way ANOVA (a)-(d). P-values are represented, with error bars representing standard error of the mean (SEM). Abbreviations: ANOVA, analysis of variance; n.s., not significant; SEM, standard error of the mean.