Hand and Upper Limb Centre, St. Joseph’s Health Centre, 268 Grosvenor Street, London, ON N6A 4L6, Canada. E-mail address for G.J.W. King: email@example.com
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EpidemiologyRadial head fractures constitute 3% of all fractures, making them the most common fracture of the elbow in adults1,2. A retrospective epidemiological study from the Netherlands noted that the incidence of radial head fractures was 2.8 per 10,000 inhabitants per year3. The male-to-female ratio was 2:3. The mean age was forty-three years.Anatomy and BiomechanicsThe elbow has three separate articulations—the ulnohumeral, radiocapitellar, and proximal radioulnar articulations (see Appendix). The medial collateral ligament (MCL) resists valgus, while the lateral collateral ligament (LCL) resists varus and posterolateral instability4,5. The radial head is an important stabilizer for valgus, axial, and posterolateral rotational forces.An increasing size of the radial head fracture fragment alters radiocapitellar stability and kinematics because of the loss of concavity-compression, which may cause painful clicking. Stability is restored with open reduction and internal fixation (ORIF) or radial head replacement6-8.Radial head excision alters elbow stability, even with intact ligaments, and radial head arthroplasty restores normal kinematics9,10. With an MCL injury, radial head excision further exacerbates valgus instability, while radial head arthroplasty restores stability similar to the native radial head9,11,12. Bipolar radial head implants are less stable than monopolar implants in cadaveric studies, suggesting that monopolar implants may be preferred in treating complex elbow instability13,14.Anthropometric studies have revealed that the radial head has a variably elliptical shape11,15. The radial head is variably offset from the radial neck, which is important since most current radial head arthroplasty and plate designs do not replicate anatomic characteristics16.The radial head articulates with the lesser sigmoid notch of the proximal part of the ulna and has articular and nonarticular surfaces. The nonarticular zone can be identified by a 110° arc from 65° anterolaterally to 45° posterolaterally with the forearm in neutral rotation17-19.Classification SystemThe optimal classification and characterization for radial head fractures are debatable20. Mason classified radial head fractures as nondisplaced, displaced, and displaced and comminuted1. This classification system was modified by Broberg and Morrey to include parameters of displacement and size21. However, these classifications have poor interobserver reliability and do not direct treatment22-24.We prefer to consider radial head fractures as partial articular (wedge) or complete articular, undisplaced or displaced, with or without comminution. The treatment sections below reflect this classification.History and Physical ExaminationPatient age, occupation, date of the injury, and treatment history are obtained. The location of pain and mechanism of injury may assist in determining associated injuries along with a history of dislocation or instability. Neurologic symptoms are elicited. The medical, surgical, anesthetic, and social history, as well as medication and allergy history, are reviewed.A thorough physical examination begins with inspection of the upper extremity and elbow for alignment, soft-tissue injury, and osseous injuries. Laterally, the epicondyle, capitellum, and radial head and neck are palpated. Medially, the epicondyle, sublime tubercle, and proximal part of the ulna are palpated. The wrist and distal radioulnar joint are assessed to rule out concomitant distal injuries. Elbow motion is assessed and, if restricted, is reevaluated after evacuation of the hematoma and intra-articular injection of local anesthetic24,25. A mechanical block to forearm rotation is an indication for surgical treatment.Associated InjuriesMinimally displaced or nondisplaced fractures do not usually have associated injuries25. Displaced, unstable, or comminuted radial head fractures have a high prevalence of an associated fracture or ligamentous injury26,27. More complex radial head fractures are commonly seen with: posterior dislocation, LCL and/or MCL disruption, capitellar fracture, terrible triad injury, posterior transolecranon fracture-dislocation (posterior Monteggia), and interosseous membrane disruption (Essex-Lopresti injury)26.