High-Yield Summary
- Terrible triad injuries combine elbow dislocation, radial head fractureand coronoid process fracture, resulting in inherent instability requiring surgical intervention in most cases.
- Early anatomic restoration of the radial head and coronoid process, combined with lateral collateral ligament (LCL) repair, is critical to restore stability and prevent chronic instability or stiffness.
- Non-operative management is rarely indicated except for minimally displaced fractures with a stable joint after reduction.
- Surgical approach typically involves a lateral (Kocher or Kaplan) exposure with selective medial exposure for coronoid fixation and medial collateral ligament (MCL) repair if instability persists.
- Postoperative rehabilitation balances early motion to prevent stiffness with protection of soft tissue repairs to avoid recurrent instability.
Clinical Fundamentals
Relevant Anatomy
The elbow joint’s stability depends on bony congruity and ligamentous support. The radial head acts as a secondary stabilizer against valgus and axial loads. The coronoid process prevents posterior translation of the ulna. The lateral collateral ligament complex (LCL) resists varus and posterolateral rotatory instability. The medial collateral ligament (MCL) provides valgus stability.
Biomechanics
The terrible triad disrupts both static and dynamic stabilizers. Radial head fractures compromise valgus and axial load resistance. Coronoid fractures destabilize the ulnohumeral articulation. LCL disruption leads to posterolateral rotatory instability. Restoration of these elements is essential to re-establish the elbow’s kinematic chain.
Epidemiology
Terrible triad injuries typically result from high-energy trauma with axial load and valgus stress on an extended elbow. They are more common in young, active patients and represent a surgical challenge due to the complexity of injury patterns and risk of complications such as stiffness, instabilityand post-traumatic arthritis.
Classification & Diagnosis
| Classification System | Description | Impact on Management |
|---|---|---|
| Regan-Morrey (Coronoid Fracture) | Type I: Tip fracture <2 mm; Type II: <50% height; Type III: >50% height | Type II and III usually require fixation to restore stability. |
| Mason (Radial Head Fracture) | Type I: Non-displaced; Type II: Displaced partial; Type III: Comminuted; Type IV: Associated dislocation | Type II-IV often need fixation or replacement; Type III and IV favor arthroplasty if reconstruction is not feasible. |
| O’Driscoll (Coronoid Fracture Subtypes) | Anteromedial facet involvement critical for varus stability | Anteromedial facet fractures require fixation to prevent varus posteromedial instability. |
Diagnostic Pearls
- Obtain true AP and lateral radiographs; CT with 3D reconstructions is essential for fracture characterization and surgical planning.
- Assess elbow stability after closed reduction; persistent instability indicates need for surgical intervention.
- Beware of missed coronoid fractures on plain films; subtle fractures can be overlooked, leading to chronic instability.
- MRI is rarely needed acutely but may assist in evaluating ligamentous injuries if instability persists postoperatively.
Decision-Making Algorithm
| Criteria | Non-Operative Management | Operative Management |
|---|---|---|
| Fracture Displacement | Minimal displacement (<2 mm coronoid tip, non-displaced radial head) | Displaced fractures, comminutionor instability after reduction |
| Joint Stability | Stable joint after closed reduction | Persistent instability or subluxation |
| Patient Factors | Low-demand, medically unfit for surgery | Active patients, young age, high functional demand |
| Surgical Approach | N/A | Lateral approach for radial head and LCL repair; medial approach for coronoid fixation and MCL repair if needed |
Why Specific Approaches and Implants?
- Radial head fixation is preferred for reconstructible fractures; arthroplasty is indicated for comminuted fractures not amenable to fixation to restore lateral column support.
- Coronoid fixation is essential for restoring anterior buttress; screws or suture anchors are chosen based on fragment size and location.
- LCL repair is mandatory to prevent posterolateral rotatory instability; MCL repair is reserved for persistent valgus instability after bony and lateral repairs.
- Early motion protocols require stable fixation and soft tissue repair to minimize stiffness without risking instability.
Surgical Mastery & Pearls
Step-by-Step Conceptual Overview
- Patient Positioning and Exposure: Supine or lateral decubitus with arm on arm board. Begin with a lateral approach (Kocher interval between anconeus and extensor carpi ulnaris).
- Radial Head Management: Assess fracture pattern; attempt anatomic fixation with headless screws or mini-fragment plates. If comminuted, proceed with modular radial head arthroplasty ensuring correct sizing to avoid overstuffing.
- Coronoid Fixation: Through lateral or separate medial approach, fix coronoid fragments with screws or suture lasso technique depending on fragment size and location. Anteromedial facet fractures require direct fixation.
- LCL Repair: Reattach LCL complex to lateral epicondyle using suture anchors or transosseous sutures. Confirm stability intraoperatively with varus and posterolateral rotatory stress tests.
- MCL Repair: Only if valgus instability persists after bony and lateral repairs; typically via medial approach with suture anchors.
- Closure and Postoperative Protocol: Close in layers; apply hinged elbow brace allowing controlled early motion.
Intraoperative Red Flags
- Overstuffing radial head arthroplasty causing decreased flexion-extension arc and capitellar wear.
- Inadequate coronoid fixation leading to persistent instability.
- Failure to repair LCL resulting in posterolateral rotatory instability.
- Excessive soft tissue stripping increasing risk of stiffness and heterotopic ossification.
Evidence-Based Synthesis
Recent high-impact studies emphasize the importance of restoring all three components of the terrible triad to optimize outcomes. A randomized controlled trial comparing radial head fixation versus arthroplasty demonstrated superior stability and fewer reoperations with arthroplasty in comminuted fractures, shifting the standard toward prosthetic replacement in these cases. Meta-analyses confirm that coronoid fixation reduces recurrent instability and improves functional scores, especially when the anteromedial facet is involved.
Controversy remains regarding the necessity of routine MCL repair; some studies suggest that stable lateral repair and bony fixation suffice in most cases, reserving MCL repair for persistent valgus laxity. Early motion protocols have evolved, with evidence supporting initiation within 1-2 weeks postoperatively to minimize stiffness without compromising repair integrity.
Despite advances, heterotopic ossification and post-traumatic arthritis remain common complications, underscoring the need for meticulous surgical technique and patient-specific rehabilitation.
Master Class Pro-Tip
When performing radial head arthroplasty, intraoperative fluoroscopy combined with direct visualization of the radiocapitellar joint is essential to avoid over-lengthening the radius. Use trial implants to confirm restoration of the lateral column height and elbow congruity before final implantation. Overstuffing is the most common technical error leading to poor outcomes and is often subtle on imaging. Mastery of this nuance differentiates a competent surgeon from a master in terrible triad management.
