Comparing Static Stability of Native Elbow With Static Stability of Novel Bidirectional Ligament Reconstruction at Different Degrees of Elbow Flexion

Abstract

Purpose: The treatment of bidirectional ligament instability is proposed using a method that simultaneously tensions medial and lateral ligaments. Graft tension is maintained via plates that apply compression between the graft and bone.

Methods: We tested static varus and valgus elbow stability in six cadaver elbows with intact ligaments and capsules at five positions, and then created gross instability by dividing all soft tissue attachments. A ligament reconstruction was subsequently performed with and without nonabsorbable ligament augmentation. Elbow stability was measured and compared with the native state.

Results: The augmented and the nonaugmented ligament reconstructions provided stability to the lateral side with only 1.0 mm of increased deflection recorded for the augmented ligaments and 0.6 mm for the nonaugmented when compared with the native state. On the medial side, the deflection was greater after reconstruction compared with the native state with the augmented ligaments ranging between 1.0 and 1.8 mm and the nonaugmented ligament reconstruction ranging between 2.4 and 3.3 mm.

Conclusions: This novel ligament reconstruction maintained secure fixation between ligament and bone and allowed for maintenance of static stability at different degrees of elbow flexion.

Clinical relevance: Restoring elbow stability using a method that minimizes ligament graft and which may not need to be removed could benefit management of bidirectionally unstable elbows, such as following interposition arthroplasty or substantial trauma.

Keywords: Cadaver; Elbow; Ligament reconstruction; Testing.

Figure 1

The cylindrical ligament retention device comes in three lengths to reside within the distal humerus. It can slide within the drill hole, allowing graft tension equalization.

Figure 2

Two plates secure the graft limbs against bone after the ligaments are pretensioned for 3 minutes to minimize postimplantation stress relaxation. Ligament grafts may be augmented with an absorbable suture. The thumb arrow describes force being imparted to seat the olecronon. The four ligament arrows describe the application of 20N on each limb. The screwdriver arrow demonstrates tightening of the bolts to compress graft against bone.

Figure 3

Drill holes within the humerus and ulna are placed using anatomic landmarks. Static testing is performed using a custom-designed experimental setup that allows elbow flexion when a 13.3 N weight is applied to the wrist.

Figure 4

Caliper measurements of the distance between the two fixed points (epicondyle and socket cap bolt head of plate) that were taken at the five positions of elbow motion (0°, 30°, 60°, 90°, and 120°).

Figure 5

Deflection measurements in full extension and flexion of 4° of flexion were recorded in the native elbow and after the augmented and nonaugmented ligament reconstruction. MCL, medial collateral; LUCL, lateral ulnar collateral.

Figure 6

Graph showing the average distance measured between medial epicondyle and medial socket cap bolt head. Measurement range is shown as a black line. MUCL, medial collateral ligament; PDS, polydioxanone.

Figure 7

Graph showing the average distance measured between lateral epicondyle and lateral socket cap bolt head. Measurement range is shown as a black line. LUCL, lateral ulnar collateral; PDS, polydioxanone.