summary Coronoid Fractures are traumatic elbow fractures that are generally pathognomonic for an episode of elbow instability. Diagnosis can be made using plain radiographs of the elbow. CT studies may be helpful for surgical planning. Treatment may be nonoperative for nondisplaced coronoid tip fractures with a stable elbow. Surgical management is indicated for anteromedial facet fractures or fractures associated with elbow instability. Epidemiology Incidence 10-15% of elbow injuries Etiology Types isolated coronoid fracture less common than previously thought coronoid fracture + associated injuries commonly occur with elbow dislocation associated with recurrent instability after dislocation Mechanism traumatic shear injury typically occurs as distal humerus is driven against coronoid with an episode of severe varus stress or posterior subluxation not an avulsion injury as nothing inserts on tip Pathoanatomy fractures at the coronoid base can amplify elbow instability given that anterior bundle of the medial ulnar collateral ligament attaches to the sublime tubercle 18 mm distal to tip anterior capsule attaches 6 mm distal to the tip of the coronoid Associated conditions posteromedial rotatory instability coronoid anteromedial facet fracture and LCL disruption results from a varus deforming force posterolateral rotatory instability coronoid tip fracture, radial head fracture, and LCL injury olecranon fracture-dislocation usually associated with a large coronoid fracture terrible triad of elbow coronoid fracture (transverse fracture pattern), radial head fracture, and elbow dislocation Anatomy Osteology coronoid tip is an intraarticular structure can be visualized during elbow arthroscopy medial facet important for varus stability provides insertion for the medial ulnar collateral ligament Biomechanics coronoid functions as an anterior buttress of the olecranon greater sigmoid notch important in preventing recurrent posterior subluxation primary resistor of elbow subluxation or dislocation Classification Regan and Morrey Classification Type I Coronoid process tip fracture Type II Fracture of 50% or less of height Type III Fracture of more than 50% of height O'Driscoll Classification - Subdivides coronoid injuries based on location and number of coronoid fragments-Recognizes anteromedial facet fractures caused by varus posteromedial rotatory force Presentation Symptoms elbow deformity & swelling elbow pain forearm or wrist pain may be a sign of associated injuries Physical exam inspection & palpation varus or valgus deformity ecchymosis & swelling diffuse tenderness range of motion & instability document flexion-extension and pronation-supination crepitus should be noted varus/valgus instability stress test challenging but important for an accurate diagnosis neurovascular exam Imaging Radiographs recommended views AP and lateral elbow views findings interpretation may be difficult due to overlapping structures CT scan useful for high grade injuries and comminuted fractures Treatment Nonoperative brief period of immobilization, followed by early range of motion indications Type I, II, and III that are minimally displaced with stable elbow Operative ORIF with medial approach indications Type I, II, and III with persistent elbow instability posteromedial rotatory instability ORIF with posterior approach indications olecranon fracture dislocation terrible triad of elbow hinged external fixation indications large fragments poor bone quality difficult revision cases to help maintain stability Techniques ORIF with medial approach approach medial exposure through an interval between two heads of FCU exposure more anteriorly through a split in flexor pronator mass technique cerclage wire or No. 5 suture through ulna drill holes for Type I injuries ORIF with retrograde cannulated screws or plate for Type II or III injuries ORIF with buttress plate fixation or pins and lateral ligament repair for posteromedial rotatory instability postoperative rehabilitation depends on intraoperative exam following the procedure thermoplastic resting splint applied with elbow at 90° and forearm in neutral restrict terminal 30° extension for 2-4 weeks avoid shoulder abduction for 4-6 weeks to prevent varus moment on arm early active motion dynamic muscle contraction may improve gapping of the ulnohumeral joint after surgical repair ORIF with posterior approach approach posterior technique mobilize olecranon fracture to access coronoid fracture for associated olecranon fracture-dislocations repair coronoid fragment first prior to reducing main ulnar fracture olecranon ORIF with dorsal plate and screws Complications Recurrent elbow instability especially medial-sided Elbow stiffness Posttraumatic arthritis Heterotopic ossification Early failure associated with failure to recognize and repair underlying elbow instability Prognosis Complications and reoperation rates are high