This is a kinematics study to determine the effect of repair of Type I coronoid fractures on elbow stability in patients with and without medial collateral ligament deficiencies. This is a cadaver study replicating a terrible triad injury. The study was performed in cadavers that had undergone radial head arthroplasty with an intact coronoid, with a coronoid fracture, and after suture repair. The study was repeated after sectioning the medial collateral ligament. The parameters measured were ulnar vs. humeral angulation during active motion, which included varus/valgus pathways with gravity loaded flexion. The results indicate that if the medial collateral ligament was intact, there was a slight increase in valgus angulation after a Type I fracture that was not corrected with suture fixation. If the MCL was deficient, there was no change regardless of coronoid status.
The results indicate that Type I coronoid fractures cause only small changes in elbow kinematics and are not corrected with repair. Thus, MCL repair rather than Type I coronoid fixation should be considered if the elbow remains unstable after radial head repair/replacement and lateral ulnar collateral ligament repair. The significance of this study is that in patients with fracture dislocations of the elbow, the surgeon will first address the lateral complex consisting of repair or replacement of the radial head and repair or reconstruction of the lateral collateral complex. There is debate as to whether coronoid fixation for smaller coronoid fractures will increase the stability of the construct. The authors’ study concludes that coronoid fixation in Type I coronoid injuries will not increase the stability of the construct and if the patients remain unstable following repair or reconstruction of the lateral complex, that attention should be turned towards the medial collateral ligament and not the Type I coronoid.
Elbow, Coronoid, Fracture, Dislocation, Stability, Instability
J Shoulder and Elbow Surg