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Thesis Format

Integrated Article

Degree

Master of Science

Program

Surgery

Supervisor

King, Graham

2nd Supervisor

Johnson, James

Co-Supervisor

Abstract

Anterior Monteggia injuries are frequently complicated by persistent radial head instability and suboptimal outcomes. Using a cadaveric elbow motion simulator, we quantified the contributions of ligaments of the proximal radius on maintaining radial head stability, evaluated the effectiveness of ulnar overcorrection to create an apex dorsal angulation in stabilizing the radiocapitellar joint, and finally compared the stabilizing effect of annular ligament repair to three different reconstruction techniques. Our results showed increased anterior radial head translation with progressive soft tissue sectioning with the annular ligament as the primary stabilizer. Ulnar overcorrection and forearm pronation were shown to decrease anterior translation of the radial head. Finally, our results showed annular ligament repair restored stability closest to the intact state. These findings support the importance of safeguarding the annular ligament and repairing if feasible. Our findings also suggest pronation may be a useful method of postoperative immobilization for patients with anterior radiocapitellar instability.

Summary for Lay Audience

Monteggia injuries are fracture-dislocations of the forearm and elbow. The forearm is made up of two bones – the ulna and the radius. When the ulna breaks close to the elbow, it can often cause the radial bone to dislocate out of its joint, at the elbow. These injuries occur most commonly from a direct blow to the forearm while the elbow is extended, like during wresting or football activities or due to conditions like osteoporosis. Monteggia fractures occur most often in young males and elderly females.

There are different types of Monteggia fractures and they are grouped into their direction of ulnar fracture and radial head dislocation. This study focuses on type 1 Monteggia fractures, which are apex anterior ulnar fractures associated with an anterior dislocation of the radial head. Type 1 Monteggia fractures are the most common type occurring in children. While children may get away with nonoperative treatment, surgical management is crucial for the majority of Monteggia fractures in adults.

The overall purpose of this biomechanical investigation is to study the specific injuries which play a role in anterior Monteggia fractures leading to anterior radial head instability. We also evaluate surgical strategies to improve radial head stability including rebreaking the ulna and creating a posterior angulation, also known as overcorrection. We also evaluated four different annular ligament repair and reconstruction procedures. In order to investigate this, we employed a cadaver-based biomechanical testing protocol.

The results showed the annular ligament to be an important stabilizer of the radial head. We also found that overcorrection of the ulna as well as a pronated forearm position helped to stabilize the radial head. Finally, we found that the annular ligament repair was the best method to restore radial head stability.

Clinical implications of these findings suggest evaluating and keeping the annular ligament protected throughout treatment. It has also been shown that overcorrection can be a viable surgical option to increase stability. Finally, since pronation helped stabilize the radial head, this could be an optimal position of immobilization for the arm in patients with anterior Monteggia fractures.

Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.

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