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The Effect of Anteromedial Facet Fractures of the Coronoid and Lateral Collateral Ligament Injury on Elbow Stability and Kinematics

¹ The Ottawa Hospital, 501 Smyth Road, Ottawa, ON K1H 8L6, Canada. E-mail address: jwpollock{at}gmail.com
² Hand and Upper Limb Clinic, University of Western Ontario, 268 Grosvenor Street, Rooms B2-226 (J.B., L.F., and C.P.M.), E2-153 (J.J.), and D0-202 (G.K.), London, ON N6A 4V2, Canada

Investigation performed at The Ottawa Hospital, Ottawa, and the Hand and Upper Limb Clinic, University of Western Ontario, London, Ontario, Canada

Disclosure: In support of their research for or preparation of this work, one or more of the authors received, in any one year, outside funding or grants of less than $10,000 from the Canadian Institute of Health Research. Neither they nor a member of their immediate families received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, division, center, clinical practice, or other charitable or nonprofit organization with which the authors, or a member of their immediate families, are affiliated or associated.

Methods: Ten fresh-frozen cadaveric arms from donors with a mean age of 66.3 years at the time of death were used in this biomechanical study. Passive elbow flexion was performed with the plane of flexion oriented horizontally to achieve varus and valgus gravitational loading. An in vitro unconstrained elbow-motion simulator was used to simulate active elbow flexion in the vertical position. Varus-valgus angle and internal-external rotational kinematics were recorded with use of an electromagnetic tracking system. Testing was repeated with the coronoid intact and with subtype-I, subtype-II, and subtype-III fractures. Instability was defined as an alteration in varus-valgus angle and/or in internal-external rotation of the elbow. All six coronoid states were tested with the lateral collateral ligament detached and after repair.

Results: In the vertical position, the kinematics of subtype-I and subtype-II anteromedial coronoid fractures with the lateral collateral ligament repaired were similar to those of the intact elbow. In the varus position, the kinematics of 2.5-mm subtype-I fractures with the lateral collateral ligament repaired were similar to those of the intact elbow. However, 5-mm fractures demonstrated a mean (and standard deviation) of 6.2° ± 4.5° of internal rotation compared with a mean of 3.3° ± 3.1° of external rotation in the intact elbow (p < 0.05). In the varus position, subtype-II 2.5-mm fractures with the lateral collateral ligament repaired demonstrated increased internal rotation (mean, 7.0° ± 4.5°; p < 0.005). Subtype-II 5-mm fractures demonstrated instability in both the varus and valgus positions (p < 0.05). Subtype-III fractures with the lateral collateral ligament repaired were unstable in all three testing positions (p < 0.05).

Conclusions: This study suggests that the size of the anteromedial coronoid fracture fragment affects elbow kinematics, particularly in varus stress. The size of an anteromedial coronoid fracture and the presence of concomitant ligament injuries may be important determinants of the need for open reduction and internal fixation.

Clinical Relevance: This biomechanical study suggests that small subtype-I anteromedial coronoid fractures may be managed with isolated repair of the lateral collateral ligament while larger fragments probably should be treated with internal fixation in addition to lateral collateral ligament repair. Additional clinical studies are needed to determine the outcomes of operative and nonoperative treatment of anteromedial coronoid fractures.

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