TERRIBLE TRIAD - COMPLEX ELBOW INSTABILITY
Dislocation + Radial Head + Coronoid | LCL Always Torn | Address All Components
THE THREE COMPONENTS
Critical Must-Knows
- All three components (bone and soft tissue) must be addressed for stability
- LCL repair is essential - always torn in posterior dislocation mechanism
- Radial head must be fixed or replaced (never excise)
- Coronoid tip fractures may not need fixation but LCL repair critical
- Surgical sequence: coronoid first, radial head, LCL repair, assess MCL
Examiner's Pearls
- "Terrible triad = dislocation + radial head + coronoid + LCL rupture
- "Coronoid is anterior buttress - prevents posterior subluxation
- "LUCL is key component of LCL - originates from lateral epicondyle
- "Redislocation rate high if components not all addressed
Clinical Imaging
Imaging Gallery
Critical Terrible Triad Exam Points
Address All Components
Four structures need treatment: coronoid, radial head, LCL (always), and sometimes MCL. Undertreating any component leads to recurrent instability. This is a pattern, not just a radial head fracture.
LCL Always Torn
The LCL (especially LUCL) is always torn in posterior dislocations. It is the primary lateral stabilizer. Must be repaired through bone tunnels or suture anchors even if coronoid is just a tip fracture.
Coronoid Function
The coronoid is the anterior buttress against posterior subluxation. More than 50% coronoid fracture or anteromedial facet fracture requires fixation. Tip fractures may be stable with LCL repair.
Radial Head Critical
Never excise the radial head in terrible triad. It is a secondary stabilizer in the MCL-deficient elbow. Fix (3 or fewer fragments) or replace (more than 3 fragments).
Quick Decision Guide - Surgical Sequence
| Step | Component | Decision | Options |
|---|---|---|---|
| 1 | Coronoid fracture | Assess size and type | Tip only: LCL may suffice. More than 50%: fix through lateral or anterior |
| 2 | Radial head | Reconstruct or replace | 3 or fewer fragments: ORIF. More than 3: arthroplasty |
| 3 | LCL repair | Always required | Suture anchors or bone tunnels to isometric point |
| 4 | Assess stability | Test through arc of motion | Stable: proceed. Unstable: consider MCL repair or hinged ex-fix |
| 5 | MCL (if needed) | Only if unstable after lateral repair | Medial approach, repair to sublime tubercle |
TRIAD - The Three Components
Memory Hook:TRIAD reminds you of all components - don't forget the LCL is the fourth structure
SEQUENCE - Surgical Order
Memory Hook:SEQUENCE keeps you on track - coronoid, radial head, LCL, then assess stability
LUCL - Lateral Collateral Structure
Memory Hook:The LUCL is the key structure in the LCL complex - always repair it
50-25-4 Rule
Memory Hook:These numbers guide surgical decision-making in terrible triad
Overview and Epidemiology
The terrible triad of the elbow describes the combination of posterior elbow dislocation, radial head fracture, and coronoid process fracture. The term "terrible" reflects the historically poor outcomes when these injuries were undertreated.
Mechanism of injury:
- Fall on outstretched hand with elbow in extension
- Axial load combined with valgus and supination moment
- Posterior dislocation occurs first
- Coronoid impacts on trochlea during reduction attempts
- Radial head impacts capitellum
Why 'Terrible'?
Historical outcomes were poor because the soft tissue components (especially LCL) were not recognized or addressed. Modern understanding that this is a pattern of instability requiring treatment of all components has improved outcomes significantly.
The four lesions:
- Posterior elbow dislocation
- Radial head fracture (Mason Type IV by definition)
- Coronoid fracture
- LCL rupture (always present but historically under-recognized)
Anatomy and Biomechanics
Elbow stability:
The elbow is one of the most stable joints due to:
- Primary stabilizers: ulnohumeral articulation, MCL (anterior bundle), LCL complex
- Secondary stabilizers: radial head, common flexor/extensor origins, joint capsule
Lateral collateral ligament complex:
- LUCL (Lateral Ulnar Collateral Ligament) - key structure, resists posterolateral rotatory instability
- RCL (Radial Collateral Ligament) - lateral epicondyle to annular ligament
- Annular ligament - encircles radial head
LUCL Importance
The LUCL is the primary restraint to posterolateral rotatory instability (PLRI). It originates from the lateral epicondyle (isometric point) and inserts on the supinator crest of the ulna. In terrible triad, the LUCL is always ruptured and must be repaired.
Coronoid function:
- Anterior buttress against posterior subluxation
- Insertion point for anterior MCL bundle
- Anteromedial facet - key for varus-posteromedial instability
Radial head function:
- Secondary valgus stabilizer
- Becomes critical when MCL is deficient
- Contributes to longitudinal forearm stability
Stability relationships:
Circle of Stability
Think of elbow stability as a ring: MCL + coronoid + radial head + LCL. Breaking the ring at two or more points creates instability. In terrible triad, the ring is broken at multiple points - all must be addressed.
Classification Systems
Regan-Morrey Classification (simple)
| Type | Description | Involvement |
|---|---|---|
| I | Tip fracture | Less than 10% height |
| II | Less than 50% of process | 10-50% height |
| III | More than 50% of process | More than 50% height |
O'Driscoll Classification (more comprehensive)
| Type | Description |
|---|---|
| 1 | Tip fractures (subtype 1 = less than 2mm, subtype 2 = more than 2mm) |
| 2 | Anteromedial facet fractures (subtypes based on extension) |
| 3 | Basal fractures (subtypes based on extension) |
Anteromedial Facet
Anteromedial facet fractures (O'Driscoll Type 2) are associated with varus-posteromedial rotatory instability, a different pattern from terrible triad. Important to distinguish as treatment differs.
Clinical Presentation and Assessment
History:
- Mechanism (FOOSH, sports, MVA)
- Any sense of the elbow "going out"
- Previous elbow problems
- Hand dominance, occupation
Physical examination:
Physical Examination
| Finding | Significance | Action |
|---|---|---|
| Elbow deformity (if unreduced) | Dislocation still present | Reduce urgently |
| Massive swelling | Significant injury | Assess skin, neurovascular status |
| Lateral tenderness | LCL injury, radial head fracture | Part of the triad |
| Medial tenderness | Possible MCL involvement | May need medial repair |
| Instability after reduction | Unstable pattern | Surgical stabilization required |
| Neurovascular deficit | Nerve or vessel injury | Document, urgent assessment |
Post-reduction assessment:
- Test stability through ROM (under anesthesia if needed)
- Note angle at which re-dislocation occurs
- Valgus stress (MCL) and varus stress (LCL)
- Posterolateral rotatory stress
Stability Testing
After closed reduction, test stability through full arc of motion. If the elbow redislocates before 30-45 degrees of extension, it is highly unstable and requires urgent surgical stabilization.
Neurovascular examination:
- Ulnar nerve (most commonly affected - up to 20%)
- Median nerve
- Radial nerve/PIN
- Brachial artery (rare but serious)
Investigations
Radiographic assessment:
Pre-reduction:
- AP and lateral elbow (confirm dislocation, identify fractures)
- May be limited by patient pain
Post-reduction:
- AP and lateral (confirm reduction, assess fractures)
- Assess concentric reduction
- Look for radial head and coronoid fractures
CT imaging (essential for surgical planning):
- All terrible triad injuries should have CT
- Assess coronoid fragment size (percentage of height)
- Assess radial head (fragment number, reconstructability)
- Look for loose bodies
- 3D reconstruction helpful for visualization
CT Mandatory
CT scan is mandatory before surgery. It allows accurate assessment of coronoid fragment size (determines if fixation needed) and radial head fragments (determines ORIF vs arthroplasty). Don't operate without CT.
Key CT findings to document:
- Coronoid: percentage of height involved, fragment type
- Radial head: number of fragments, reconstructability
- Associated injuries (capitellum, medial epicondyle)
- Loose bodies in joint
Management
Emergency department:
- Closed reduction of elbow (usually in ED under sedation)
- Post-reduction X-rays
- Splint at 90 degrees
- Assess stability (may defer to OR if too painful)
- CT scan for surgical planning
Do Not Delay
Terrible triad injuries require surgical intervention. Do not discharge with plan for delayed surgery. Recurrent instability, stiffness, and heterotopic ossification increase with delay.
Surgical Technique
Lateral approach (Kocher or extended lateral) is standard.
Kocher approach:
- Interval between anconeus and ECU
- Identify and protect LCL origin
- Excellent access to radial head and lateral coronoid
Extended lateral (Hotchkiss):
- Extension of Kocher
- Better access to coronoid through radial head defect
- Can split common extensor origin
Key points:
- Do not detach LCL from epicondyle (it's already torn)
- Use torn LCL as a window
- Identify LUCL for later repair
Working through the existing disruption avoids further soft tissue damage and maintains surgical exposure.
Complications
Complications of Terrible Triad
| Complication | Incidence | Prevention/Management |
|---|---|---|
| Recurrent instability | 5-15% (modern techniques) | Address all components, adequate LCL repair |
| Elbow stiffness | 20-40% | Early motion, avoid over-immobilization |
| Heterotopic ossification | 10-20% | Indomethacin prophylaxis, early motion |
| Post-traumatic arthritis | 10-30% | Anatomic reduction of articular surfaces |
| Ulnar neuropathy | 10-15% | Careful retraction, may need transposition |
| Hardware failure/prominence | 5-10% | Adequate fixation, hardware removal if symptomatic |
| Nonunion | Rare (less than 5%) | Adequate fixation, bone graft if at-risk |
Recurrent instability:
- Most serious complication
- Usually due to undertreated components
- Prevention: meticulous surgical technique addressing all structures
- Treatment: revision surgery, may need hinged ex-fix
Stiffness:
- Very common after complex elbow trauma
- Goal: functional arc (30-130 degrees)
- Prevention: early motion (within first week)
- Treatment: physiotherapy, dynamic splinting, surgical release
HO Prophylaxis
Heterotopic ossification (HO) is common in terrible triad. Consider prophylaxis with indomethacin 75mg/day for 2-3 weeks or single-dose radiation. Early motion also reduces HO risk.
Postoperative Care and Rehabilitation
Post-surgical protocol:
- Posterior splint at 90 degrees
- Elevation, ice
- Wound monitoring
- Finger motion encouraged
- Remove splint, begin ROM
- Active and active-assisted motion
- May use hinged brace if stability concerns
- Avoid terminal extension if any instability
- Progressive ROM
- Goal: functional arc by 6 weeks
- Dynamic splinting if stiff
- Avoid varus stress and forced extension
- Begin pronation/supination as tolerated
- Full active ROM expected
- Begin gentle strengthening
- Progressive loading
- Wean from brace if used
- Progressive strengthening
- Return to work (desk work earlier)
- Sports depending on demands
- May take 6-12 months for full recovery
Key rehabilitation principles:
- Early motion is critical but must balance with stability
- Avoid varus stress (stresses LCL repair)
- Hinged brace allows motion while limiting terminal extension
- Patient education about activity restrictions
- Long-term outcome depends heavily on rehabilitation compliance
Outcomes and Prognosis
Outcomes with modern treatment:
Modern understanding and treatment of all components has dramatically improved outcomes compared to historical series.
| Era | Good/Excellent | Key Issues |
|---|---|---|
| Historical (pre-1990s) | 40-50% | Undertreatment of soft tissues |
| Modern (comprehensive repair) | 70-85% | All components addressed |
Prognostic factors:
- Coronoid fragment size (larger = worse prognosis)
- Quality of repairs
- Associated injuries (MCL, capitellum)
- Time to surgery (delay increases stiffness and HO)
- Patient compliance with rehabilitation
Key to Success
The key to good outcomes is recognizing this as a pattern of instability and addressing all components: coronoid (fix if significant), radial head (fix or replace), LCL (always repair). Undertreating any component leads to poor results.
Evidence Base
- Systematic approach addressing all components (coronoid fixation, radial head repair/replacement, LCL repair) produced 78% good/excellent results. This changed the paradigm from conservative to surgical management.
- Coronoid fractures are key to elbow stability. Fractures involving more than 50% of the coronoid are associated with persistent instability. LCL repair is essential even with small coronoid fractures.
- More detailed coronoid classification identifying anteromedial facet fractures as distinct pattern. These are associated with varus-posteromedial rotatory instability, different from terrible triad.
- Meta-analysis of terrible triad outcomes showed 82% satisfactory results with surgical treatment. Radial head replacement had similar outcomes to ORIF when ORIF was appropriate.
- Described surgical technique for complex elbow instability including extended lateral approach, coronoid access through radial head defect, and systematic repair sequence.
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
Scenario 1: Classic Terrible Triad Presentation
"A 40-year-old man presents after falling off a ladder. X-rays show a posterior elbow dislocation that has been reduced. Post-reduction X-rays show a radial head fracture and coronoid tip fracture. The elbow feels unstable to the ED doctor. What is your assessment and management?"
Scenario 2: Persistent Intraoperative Instability
"You have performed ORIF of the coronoid (suture lasso), radial head arthroplasty, and LCL repair for a terrible triad. On testing, the elbow still redislocates at 40 degrees of extension. What do you do next?"
Scenario 3: Delayed Presentation with Complications
"A patient presents 3 weeks after a terrible triad injury that was initially splinted and sent home with plan for delayed surgery. The elbow is now stiff, with only 30-80 degrees motion, and X-ray shows early heterotopic ossification. How do you manage this?"
MCQ Practice Points
Definition Question
Q: What are the three osseous components of the terrible triad of the elbow? A: (1) Posterior elbow dislocation, (2) radial head fracture, (3) coronoid fracture. Note: the LCL rupture is the fourth component (soft tissue) that is always present.
Anatomy Question
Q: What is the function of the coronoid process in elbow stability? A: The coronoid is the anterior buttress that resists posterior subluxation of the ulna. It is also the insertion point for the anterior bundle of the MCL (sublime tubercle).
Surgical Order Question
Q: What is the recommended surgical sequence for terrible triad repair? A: (1) Address coronoid first (fix if more than 50% or unstable), (2) radial head (ORIF or replace), (3) LCL repair (essential), (4) assess stability, (5) MCL repair if still unstable.
LCL Question
Q: Why must the LCL be repaired in terrible triad even if the coronoid is just a tip fracture? A: The LCL is always torn in posterior elbow dislocations. The LUCL is the primary restraint to posterolateral rotatory instability. Without repair, even small coronoid fractures can result in recurrent instability.
Radial Head Question
Q: In terrible triad, when should the radial head be replaced rather than fixed? A: When there are more than 3 fragments (unreconstructable). The radial head should never be excised without replacement as it is a critical secondary stabilizer in the MCL-deficient elbow.
Australian Context
Epidemiology:
- Sports injuries (cycling, football, rugby) common mechanism
- Motor vehicle and motorcycle accidents
- Falls in elderly population
Management considerations:
- Subspecialty referral often appropriate for these complex injuries
- May need transfer to major trauma center
Implant availability:
- Various radial head prostheses available
- Hinged external fixators available at major centers
- Ensure equipment availability before surgery
Exam Context
Be prepared to describe the systematic surgical approach to terrible triad. Know the coronoid fixation thresholds, radial head decision-making, and that LCL repair is mandatory. Understand the concept of elbow instability as a pattern requiring treatment of all components.
TERRIBLE TRIAD OF THE ELBOW
High-Yield Exam Summary
THE FOUR COMPONENTS
- •1. Posterior elbow dislocation
- •2. Radial head fracture (Mason IV by definition)
- •3. Coronoid fracture
- •4. LCL rupture (always present, often forgotten)
SURGICAL SEQUENCE
- •1. Coronoid: fix if more than 50% (suture, screw, or plate)
- •2. Radial head: ORIF (3 or fewer fragments) or replace (more than 3)
- •3. LCL: ALWAYS repair (suture anchors to isometric point)
- •4. Stability check: if unstable, consider MCL or hinged ex-fix
CORONOID DECISION
- •Tip (less than 10%): LCL repair may be sufficient
- •Less than 50% (Regan-Morrey II): consider fixation
- •More than 50% (Regan-Morrey III): fixation required
- •Access through radial head defect if present
RADIAL HEAD DECISION
- •3 or fewer fragments: ORIF (headless screws, safe zone)
- •More than 3 fragments: arthroplasty
- •NEVER excise without replacement
- •Secondary stabilizer - critical in MCL-deficient elbow
LCL REPAIR
- •ALWAYS required - non-negotiable
- •LUCL is key component
- •Repair to isometric point (center of lateral epicondyle)
- •Suture anchors or bone tunnels with non-absorbable suture
TRAPS AND PEARLS
- •Don't treat as simple radial head fracture
- •Don't forget LCL repair
- •CT is mandatory before surgery
- •Early motion essential but balance with stability
- •HO prophylaxis (indomethacin) recommended