Transverse coronoid fracture: when does it have to be fixed?

BACKGROUND: After elbow fracture-dislocation, surgeons confront numerous treatment options in pursuing a stable joint for early motion. The relative contributions of the radial head and coronoid, in combination, to elbow stability have not been defined fully. QUESTIONS/PURPOSES: The purpose of this study was to evaluate the effect of an approximately 50% transverse coronoid fracture and fixation in the setting of an intact or resected radial head on coronal (varus/valgus) and axial (internal and external rotational) laxity in (1) gravity varus stress; and (2) gravity valgus stress models.
METHODS: Kinematic data were collected on six fresh-frozen cadaveric upper extremities tested with passive motion throughout the flexion arc under varus and valgus gravity stress with lateral collateral ligaments reconstructed. Testing included coronoid fracture and osteosynthesis with and without a radial head.
RESULTS: In the varus gravity stress model, fixation of the coronoid improved varus stability (fixed: 1.6° [95% confidence interval, 1.0-2.2], fractured: 5.6° [4.2-7.0], p < 0.001) and internal rotational stability (fixed: 1.8° [0.9-2.7], fractured: 5.4° [4.0-6.8], p < 0.001), but radial head fixation did not contribute to varus stability (intact head: 2.7° [1.3-4.1], resected head: 3.8° [2.3-5.3], p = 0.4) or rotational stability (intact: 2.7° [0.9-4.5], resected head: 3.9° [1.5-6.3], p = 0.4). With valgus stress, coronoid fixation improved valgus stability (fixed: 2.1° [1.0-3.1], fractured: 3.8° [1.8-5.8], p < 0.04) and external rotation stability (fixed: 0.8° [0.1-1.5], fractured: 2.1° [0.9-3.4], p < 0.04), but the radial head played a more important role in providing valgus stability (intact: 1.4° [0.8-2.0], resected head: 7.1° [3.5-10.7], p < 0.001).
CONCLUSIONS: Fixation of a 50% transverse coronoid fracture improves varus and internal rotatory laxity but is unlikely to meaningfully improve valgus or external rotation laxity. The radial head, on the other hand, is a stabilizer to resist valgus stress regardless of the status of the coronoid. CLINICAL RELEVANCE: Determination as to whether it is necessary to fix a coronoid fracture should be based on the stability of the elbow when tested with a varus load. The elbow may potentially be stable with fractures involving less than 50% of the coronoid. Under all circumstances, the radial head should be fixed or replaced to ensure valgus external rotatory stability.