| Introduction |
 Coronoid fractures are pathognomonic of an episode of elbow instability
- may be
- 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
- Epidemiology
- 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
- Prognosis
- complications and reoperation rates are high
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| Anatomy |
- Coronoid 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
- Coronoid 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
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| Classification |
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Regan and Morrey Classification
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| Type I |
coronoid process tip fracture
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| Type II |
fracture of 50% or less of height |
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| Type III |
fracture of more than 50% of height |
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O'Driscoll Classification
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- Subdivides coronoid injuries based on location and number of coronoid fragments
- Recognizes anteromedial facet fractures caused by varus posteromedial rotatory force
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| 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
- varus/valgus instability stress test
- challenging but important for an accurate diagnosis
- neurovascular exam
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| 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
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| 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
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| 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
- 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
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| Complications |
- Recurrent elbow instability
- Elbow stiffness
- Posttraumatic arthritis
- Heterotopic ossification
- Early failure
- associated with failure to recognize and repair underlying elbow instability
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