Defining safe rehabilitation for ulnar collateral ligament reconstruction of the elbow: a biomechanical study.

BACKGROUND

Ulnar collateral ligament reconstruction of the elbow using a variety of techniques has been successful in enabling overhead athletes with ulnar collateral ligament insufficiency to return to competition. Most current postoperative rehabilitation programs begin with a period of motion restriction, including limiting elbow extension, that is followed by a transition from elbow strengthening to an interval throwing program, to competition. Motion restrictions early in the postoperative period may increase the risk for contractures. There is limited information to support current motion restrictions.

PURPOSE

(1) To determine strain on the reconstructed ulnar collateral ligament during a rehabilitation protocol that includes passive range of motion, isometric muscle contraction, and varus and valgus torques. (2) To develop guidelines for a safe initial rehabilitation protocol.

STUDY DESIGN

Controlled laboratory study.

METHODS

Eight cadaveric elbows underwent ulnar collateral ligament reconstruction with the docking technique using a gracilis tendon graft. Differential variable reluctance transducers on the anterior and posterior bands of the reconstructed anterior bundle of the ulnar collateral ligament were used to measure strain, while an optical motion tracking system monitored elbow motion. Strain was measured in the following 3 settings: passive range of motion, 22.2 N isometric flexion and extension contractions, and 3.34 N x m varus and valgus torques with the arm at 90 degrees of flexion.

RESULTS

Range of motion from maximum extension to 50 degrees of flexion produced 3% or less strain in both bands of the reconstructed ligament. Forearm rotation did not significantly affect strain in the anterior or posterior bands (P = .336 and P = .357). Strain at 90 degrees approached 7% in the posterior band (upper 95% confidence interval). Isometric muscle contractions had no measurable effect on strain. Varus torques decreased and valgus torques increased strain significantly (P < .05).

CONCLUSION

In the immediate postoperative period, full extension is safe, while flexion beyond 50 degrees may place deleterious strain on the reconstruction. Isometric flexion and extension exercises do not increase ligament strain but may be unsafe at 90 degrees of flexion, while valgus exercises (internal rotation at the shoulder) can increase strain in the reconstructed ligament.

CLINICAL RELEVANCE

The results have implications for the development of appropriate rehabilitation protocols after ulnar collateral ligament reconstructive surgery.