High-Yield Summary
- The coronoid process is critical for anterior elbow stability; fractures compromise varus and posteromedial rotatory stability, often necessitating fixation in unstable elbows.
- Regan-Morrey and O’Driscoll classifications guide fixation strategy by fracture size and location, directly influencing surgical approach and implant choice.
- Small tip fractures (<10% of coronoid height) may be managed non-operatively if the elbow is stable; larger or anteromedial facet fractures require surgical fixation to restore stability.
- Surgical approaches include the anteromedial, medialand lateral windows, selected based on fracture pattern and associated ligamentous injury.
- Fixation techniques range from suture lasso constructs for small fragments to buttress plating for anteromedial facet fractures; rigid fixation is essential to allow early motion and prevent stiffness.
Clinical Fundamentals
The coronoid process forms the anterior buttress of the ulnohumeral joint, resisting posterior translation and varus stress. It contributes approximately 50% of the elbow’s bony stability, particularly against posteromedial rotatory forces. The anteromedial facet is a key stabilizer against varus posteromedial rotatory instability (PMRI), while the tip resists posterior subluxation. The elbow’s stability is further supported by the medial collateral ligament (MCL) and lateral collateral ligament (LCL) complexes, which often sustain concomitant injury in coronoid fractures.
Epidemiologically, coronoid fractures are uncommon in isolation and frequently occur with elbow dislocations or complex fracture-dislocations such as the “terrible triad” (radial head fracture, coronoid fractureand LCL injury). Failure to recognize and fix these fractures leads to chronic instability, arthritisand poor functional outcomes.
Classification & Diagnosis
| Classification System | Description | Surgical Implication |
|---|---|---|
| Regan-Morrey | Type I: Tip <2 mm Type II: <50% height Type III: >50% height | Type I often non-operative if stable Type II/III usually require fixation |
| O’Driscoll | Type 1: Tip fractures Type 2: Anteromedial facet fractures Type 3: Basal fractures | Type 2 requires buttress plating to restore varus stability |
| Diagnostic Pearls | Use CT with 3D reconstructions for fracture morphology Assess elbow stability under fluoroscopy post-reduction Beware of missed anteromedial facet fractures on plain films | Misclassification risks inadequate fixation and persistent instability |
Decision-Making Algorithm
Non-operative management is reserved for isolated, small tip fractures (<10% coronoid height) with a stable elbow after reduction and no ligamentous disruption. Early mobilization is critical to prevent stiffness.
Operative fixation is indicated when:
- Fracture involves >50% of coronoid height (Regan-Morrey Type III).
- Anteromedial facet fractures (O’Driscoll Type 2) causing varus instability.
- Associated ligamentous injuries (LCL or MCL) causing gross instability.
- Elbow remains unstable after closed reduction.
Surgical approach selection depends on fracture location and associated injuries:
- Anteromedial approach for anteromedial facet fractures to allow buttress plating.
- Medial approach for basal fractures and MCL repair.
- Lateral approach for tip fractures and concomitant radial head fixation.
Implant choice balances fragment size and bone quality:
- Suture lasso or suture anchors for small tip fragments.
- Headless compression screws for larger fragments with sufficient bone stock.
- Mini fragment buttress plates for anteromedial facet fractures to resist varus forces.
Surgical Mastery & Pearls
Step 1: Exposure
Position the patient supine or lateral decubitus with the arm on a radiolucent arm board. Use the approach tailored to fracture type: anteromedial for facet fractures, medial for basal fractures, lateral for tip fractures. Protect the ulnar nerve during medial exposures.
Step 2: Fracture Reduction
Achieve anatomic reduction under direct visualization. Use temporary K-wire fixation to maintain reduction. Confirm reduction fluoroscopically in multiple planes.
Step 3: Fixation
For small tip fractures, employ a suture lasso technique through the anterior capsule and coronoid tip, tied over a bone bridge or suture anchor. For larger fragments, insert headless compression screws perpendicular to the fracture plane to maximize compression without hardware prominence.
For anteromedial facet fractures, apply a mini fragment buttress plate along the medial ulna to counteract varus forces. Ensure the plate is contoured to the ulna and does not impinge on the joint.
Step 4: Ligament Repair
Address concomitant LCL or MCL injuries with suture anchors or transosseous repair to restore soft tissue stability.
Intraoperative Red Flags
- Persistent instability after fixation suggests missed ligamentous injury or inadequate fixation.
- Excessive soft tissue stripping risks stiffness and heterotopic ossification.
- Hardware prominence can cause mechanical block or cartilage damage.
Technical Tips
- Use intraoperative fluoroscopy to confirm screw length and plate position.
- Preserve the anterior capsule to maintain elbow stability.
- Early controlled motion postoperatively reduces stiffness without compromising fixation.
Evidence-Based Synthesis
Recent literature emphasizes the importance of restoring the anteromedial facet in PMRI to prevent recurrent instability. Biomechanical studies demonstrate that buttress plating of the anteromedial facet restores varus stability more effectively than screw fixation alone. Clinical series report improved outcomes with combined bony and ligamentous repair in terrible triad injuries, reducing rates of recurrent dislocation and arthrosis.
Randomized controlled trials comparing fixation methods are limited; however, consensus favors rigid fixation with early motion protocols. Controversy remains regarding the necessity of fixing small tip fractures in the presence of ligamentous repair alone. Emerging data suggest that selective non-fixation may be safe in highly stable elbows, but this requires careful intraoperative assessment.
The evolving role of arthroscopic-assisted fixation is promising but currently lacks robust comparative data. Future studies are needed to define indications and long-term outcomes.
Master Class Pro-Tip
Mastery in coronoid fracture fixation hinges on recognizing the fracture’s biomechanical role within the elbow’s stability complex. Prioritize anatomic restoration of the anteromedial facet with buttress plating when indicatedand never underestimate the need for meticulous soft tissue repair. Intraoperative dynamic assessment of stability after fixation guides the necessity for additional ligament reconstruction. This tailored, stability-driven approach-not fragment size alone-defines surgical excellence and optimizes functional recovery.
