LUCL Insufficiency | Elbow Dislocation Spectrum | Horii Circle Injury
INJURY SPECTRUM
Critical Must-Knows
- LUCL originates from lateral epicondyle, inserts on supinator crest of ulna
- PLRI follows simple elbow dislocation or repetitive varus stress
- Pivot-shift test: patient supine, arm overhead, forearm supinated, valgus + axial load produces subluxation
- Horii circle describes sequential soft-tissue disruption from lateral to medial
- Reconstruction uses tendon graft (palmaris, gracilis, or triceps) through bone tunnels or anchors
Clinical Pearls
- "PLRI often missed after simple dislocation - always test lateral stability
- "Chair push-up test and lateral pivot apprehension sign are highly sensitive
- "MRI in supination shows LUCL discontinuity and posterolateral capsule injury
- "Reconstruction indicated when instability persists beyond 3-6 months
Clinical Imaging
Posterolateral Rotatory Instability Clinical and Radiographic Features
Critical PLRI Exam Points
Horii Circle Stages
Stage 1: LUCL tear. Stage 2: + posterolateral capsule. Stage 3: + radial collateral ligament. Stage 4: + anterior and posterior capsule. Stage 5: + medial collateral ligament (complete dislocation).
Pivot-Shift Test
Technique: Patient supine, shoulder flexed 90 degrees, forearm fully supinated. Apply valgus and axial load while flexing from extension. Positive = radial head subluxes posterolaterally at 40-60 degrees flexion, reduces with further flexion.
Lateral Pivot Apprehension
Sign: Patient experiences apprehension or reproduction of instability when the forearm is supinated and a valgus force is applied in slight flexion. Highly sensitive for symptomatic PLRI.
Chair Push-Up Test
Technique: Patient pushes up from a chair with hands on armrests, forearms supinated. Positive test = reproduction of posterolateral pain or instability sensation. Sensitivity over 90 percent in confirmed PLRI.
Quick Decision Guide
| Presentation | Diagnosis | Treatment | Key Pearl |
|---|---|---|---|
| Post-dislocation instability | Positive pivot-shift + apprehension | LUCL reconstruction with graft | Wait 3-6 months before surgery |
| Chronic posterolateral pain | Chair push-up and table-top tests positive | Graft reconstruction (palmaris/gracilis) | Address any bony deficiency first |
| Acute simple dislocation | Stress views under anesthesia | Non-operative if stable post-reduction | Reassess stability at 2-3 weeks |
LATERALHorii Circle of Injury
| L | LUCL first Primary restraint fails under supination-valgus |
| A | Anterior capsule Next structure to yield in progression |
| T | Table-top test Clinical correlate of posterolateral instability |
| E | External rotation Ulna externally rotates on humerus |
| R | Radial head subluxes Posterolateral prominence visible |
| A | Apprehension sign Patient guards against supinated valgus stress |
| L | Ligament reconstruction Definitive treatment when symptomatic |
| L | LUCL first Primary restraint fails under supination-valgus | E | External rotation Ulna externally rotates on humerus | L | Ligament reconstruction Definitive treatment when symptomatic |
| A | Anterior capsule Next structure to yield in progression | R | Radial head subluxes Posterolateral prominence visible | ||
| T | Table-top test Clinical correlate of posterolateral instability | A | Apprehension sign Patient guards against supinated valgus stress |
Hook:Horii circle starts LATERAL and marches medially until the elbow dislocates!
SUPINATEPivot-Shift Test Steps
| S | Supine position Patient lies flat with arm overhead |
| U | Upper arm stabilised Examiner holds humerus firmly |
| P | Pronation avoided Forearm held in full supination |
| I | Initial extension Start with elbow near full extension |
| N | Neutral to valgus Apply gentle valgus and axial load |
| A | Apprehension at 40-60 Subluxation occurs in mid-flexion |
| T | Terminal flexion Further flexion reduces the joint |
| E | Examiner feels clunk Reduction palpable and visible |
| S | Supine position Patient lies flat with arm overhead | I | Initial extension Start with elbow near full extension | T | Terminal flexion Further flexion reduces the joint |
| U | Upper arm stabilised Examiner holds humerus firmly | N | Neutral to valgus Apply gentle valgus and axial load | E | Examiner feels clunk Reduction palpable and visible |
| P | Pronation avoided Forearm held in full supination | A | Apprehension at 40-60 Subluxation occurs in mid-flexion |
Hook:SUPINATE the forearm and feel the radial head jump back into place!
GRAFTPLRI Reconstruction Principles
| G | Graft choice Palmaris longus, gracilis or triceps tendon |
| R | Reproduce LUCL origin Isometric point just distal to lateral epicondyle |
| A | Anchor or tunnel fixation Suture anchors or bone tunnels at ulna |
| F | Flexion angle critical Tension graft at 30-40 degrees flexion |
| T | Test stability intra-op Pivot-shift should be eliminated |
| G | Graft choice Palmaris longus, gracilis or triceps tendon | F | Flexion angle critical Tension graft at 30-40 degrees flexion |
| R | Reproduce LUCL origin Isometric point just distal to lateral epicondyle | T | Test stability intra-op Pivot-shift should be eliminated |
| A | Anchor or tunnel fixation Suture anchors or bone tunnels at ulna |
Hook:GRAFT the LUCL isometrically and test stability before closure!
Overview and Epidemiology
Why This Matters
Posterolateral rotatory instability is the most common pattern of recurrent elbow instability after simple dislocation. The lateral ulnar collateral ligament (LUCL) is the primary restraint. Missed or undertreated PLRI leads to chronic pain, mechanical symptoms, and secondary osteoarthritis. Early recognition of the Horii circle injury pattern and appropriate ligament reconstruction restore stability in over 85 percent of patients.
Mechanism of Injury
- Simple elbow dislocation: Most common precursor (valgus-hyperextension)
- Repetitive varus stress: Overhead athletes, gymnasts
- Iatrogenic: Excessive release during lateral epicondylitis surgery
- Trauma: Direct varus blow or fall onto outstretched hand
Clinical Impact
- Mechanical instability: Clicking, clunking with supinated activities
- Pain: Posterolateral elbow, worse with loading in supination
- Secondary OA: Chronic subluxation accelerates radiocapitellar wear
- Functional loss: Difficulty with pushing, throwing, weight-bearing
Pathophysiology
LUCL Anatomy and Restraint Function
The lateral ulnar collateral ligament originates from the lateral epicondyle just distal and slightly anterior to the common extensor origin. It courses distally and inserts on the supinator crest of the proximal ulna. The LUCL is the primary static restraint to posterolateral rotatory instability. Secondary restraints include the radial collateral ligament, posterolateral capsule, and when deficient, the medial collateral ligament complex. The radial head acts as a secondary stabilizer; its excision dramatically increases PLRI risk.
Soft-Tissue Restraints to PLRI
| Structure | Function | When Deficient | Clinical Relevance |
|---|---|---|---|
| LUCL | Primary restraint to external rotation of ulna | Allows posterolateral subluxation | Target of reconstruction |
| Radial collateral ligament | Resists varus and posterolateral rotation | Increases instability magnitude | Often reconstructed together |
| Posterolateral capsule | Secondary check-rein to rotation | Permits greater subluxation arc | Repaired or imbricated during surgery |
| Medial collateral ligament | Final restraint in complete dislocation | Complete dislocation occurs | Rarely addressed in isolated PLRI |
Horii Circle Progression
Stage 1: LUCL tear only - pivot-shift positive Stage 2: + posterolateral capsule - increased external rotation Stage 3: + radial collateral ligament - gross subluxation Stage 4: + anterior/posterior capsule - perched dislocation Stage 5: + MCL - complete dislocation (ulnohumeral joint)
Why Stability Returns Acutely
Acute dislocation: Swelling and hemarthrosis provide temporary stability Healing potential: LUCL may heal in extension but not in supination Missed diagnosis: Patients often told "simple dislocation" and discharged Late presentation: 6-24 months later with mechanical symptoms
Classification and Types
Classification by Soft-Tissue Injury Stage
| Stage | Structures Torn | Clinical Test | Treatment |
|---|---|---|---|
| Stage 1 | LUCL only | Pivot-shift positive, apprehension | Non-operative trial or repair |
| Stage 2 | LUCL + posterolateral capsule | Gross pivot-shift, clunk | Reconstruction indicated |
| Stage 3 | + radial collateral ligament | Subluxation at rest, visible prominence | Graft reconstruction mandatory |
| Stage 4-5 | Complete dislocation, MCL involved | Recurrent dislocation episodes | Staged or combined medial-lateral reconstruction |
The Horii circle concept explains why some elbows remain unstable after "simple" dislocation reduction.
Clinical Assessment
History
- Index event: Simple elbow dislocation or varus injury
- Timing: When instability symptoms began after injury
- Activities: Pain or clunk with pushing, throwing, supinated loading
- Prior treatment: Immobilisation duration, therapy, injections
Examination Sequence
- Inspect: Swelling, radial head prominence, carrying angle
- Palpate: Lateral epicondyle tenderness, radial head click
- ROM: Note flexion arc, any extension loss from prior injury
- Stability tests: Pivot-shift, lateral pivot apprehension, chair push-up, table-top
Pivot-Shift Test: Gold Standard for PLRI
Technique: Patient supine, shoulder flexed to 90 degrees, elbow extended, forearm fully supinated. Examiner applies valgus force and axial compression while slowly flexing the elbow. At approximately 40-60 degrees of flexion the radial head subluxes posterolaterally (felt as a clunk or visible prominence). Further flexion to 90-100 degrees reduces the joint with a second clunk. Key point: The test is performed under anesthesia if apprehension prevents relaxation. Sensitivity approaches 100 percent when performed correctly.
Clinical Tests for PLRI
| Test | Technique | Positive Finding | Sensitivity |
|---|---|---|---|
| Pivot-shift test | Supine, arm overhead, supinated forearm, valgus + axial load during flexion | Radial head subluxes at 40-60 degrees, reduces in further flexion | Gold standard - near 100 percent when relaxed |
| Lateral pivot apprehension | Supinated forearm, valgus stress in 20-30 degrees flexion | Patient apprehension or reproduction of instability | Greater than 90 percent in symptomatic PLRI |
| Chair push-up test | Push up from chair with forearms supinated | Pain or instability sensation posterolaterally | Greater than 90 percent sensitivity |
| Table-top test | Patient leans on table with elbow extended, forearm supinated | Pain or giving-way sensation | Useful office screening test |
Differentiating PLRI from Other Lateral Elbow Pathology
Lateral epicondylitis produces point tenderness at the epicondyle but negative pivot-shift and no mechanical instability. Radial tunnel syndrome causes forearm pain without instability signs. PLRI is confirmed only when the pivot-shift or apprehension tests are positive. Always perform stability testing before diagnosing "tennis elbow" in a post-dislocation patient.
Investigations
Imaging Protocol
Views: AP, lateral, oblique of elbow Look for: Radial head subluxation, coronoid fracture, radial head fracture, heterotopic ossification Clinical correlation: Many PLRI cases have normal radiographs; diagnosis is clinical
Indication: When clinical tests equivocal or under anesthesia Technique: Supinated forearm with valgus load, compare to contralateral side Positive finding: Greater than 3 mm radial head posterior translation or ulnohumeral gapping
Indication: Pre-operative planning, confirm LUCL tear, assess cartilage Best sequence: T2-weighted coronal and axial in supination Findings: LUCL discontinuity or attenuation, posterolateral capsule injury, radial head chondral damage
Imaging Pearl
MRI is most useful when performed with the forearm in supination and elbow in slight flexion. The LUCL is best seen on coronal images just distal to the lateral epicondyle. A "bright" or discontinuous LUCL on T2 is diagnostic, but a normal MRI does not exclude symptomatic PLRI if clinical tests are positive.
Management Algorithm
Acute or Minimally Symptomatic PLRI
Goal: Allow soft-tissue healing and assess whether instability resolves with protected motion
Treatment Protocol
Immobilisation: Posterior splint or hinged brace at 90 degrees flexion, neutral rotation Avoid: Forced supination or varus stress Early motion: Gentle flexion-extension in pronation only
Hinged brace: Allow gradual extension, maintain pronation during loading Strengthening: Isometric exercises, avoid supinated resistance Reassess: Pivot-shift test at 6 weeks
Progressive loading: Begin supinated activities if stable Physiotherapy: Proprioception, dynamic stabiliser strengthening Return to sport: 3-4 months if asymptomatic and stable
Non-operative Success Factors
Non-operative treatment succeeds in approximately 30-40 percent of acute post-dislocation PLRI when the injury is limited to stage 1-2 and the patient avoids supinated loading during healing. Failure is common when the Horii circle extends beyond stage 2 or when early aggressive supination exercises are prescribed.
Evidence Base
The pivot-shift test for posterolateral rotatory instability of the elbow
- Described the pivot-shift test and its pathognomonic finding of posterolateral subluxation in LUCL insufficiency
- Demonstrated that the LUCL is the primary restraint to posterolateral rotatory instability
- Established the clinical test that remains the gold standard for diagnosis
Lateral ulnar collateral ligament reconstruction for posterolateral rotatory instability
- Retrospective review of 44 patients undergoing LUCL reconstruction
- Good to excellent results in 82 percent at mean 6-year follow-up
- Palmaris longus autograft with bone tunnels provided reliable stability
Long-term outcomes of LUCL reconstruction using triceps tendon autograft
- Prospective cohort of 25 patients with triceps tendon reconstruction
- 92 percent stability at mean 8-year follow-up, 80 percent returned to pre-injury sport
- Isometric tunnel placement and tensioning at 30 degrees flexion critical to success
Tardy posterolateral rotatory instability of the elbow due to cubitus varus
- Described the association between cubitus varus malunion and late-onset PLRI
- Proposed corrective osteotomy combined with LUCL reconstruction for optimal outcomes
Exam Viva Scenarios
Use these scenarios to practise clinical reasoning and management decisions
Scenario 1: Post-Dislocation Instability
"A 32-year-old rugby player sustained a simple elbow dislocation 4 months ago that was reduced in the emergency department. He has since had recurrent mechanical clicking and a feeling of instability when pushing up from a chair or throwing. Examination demonstrates a positive pivot-shift test and lateral pivot apprehension sign. X-rays are normal. How would you manage this patient?"
Scenario 2: Chronic PLRI with Chondral Wear
"A 45-year-old manual labourer presents with 18-month history of posterolateral elbow pain and instability after a fall onto an outstretched hand. He has a positive pivot-shift under anesthesia and MRI shows LUCL tear, radial head chondral loss, and early capitellar wear. He cannot return to heavy work. How would you manage?"
MCQ Practice Points
Anatomy Question
Q: What is the primary restraint to posterolateral rotatory instability of the elbow? A: The lateral ulnar collateral ligament (LUCL). It originates from the lateral epicondyle and inserts on the supinator crest of the ulna. Sectioning studies confirm it is the essential lesion; all other lateral structures are secondary.
Diagnosis Question
Q: Describe the pivot-shift test for PLRI and what constitutes a positive result. A: Patient supine, shoulder flexed 90 degrees, forearm fully supinated. Apply valgus and axial load while flexing the elbow from extension. Positive test: radial head subluxes posterolaterally at 40-60 degrees flexion with a palpable clunk, then reduces with further flexion. The test is pathognomonic for LUCL insufficiency.
Injury Pattern Question
Q: What is the Horii circle and why is it clinically relevant to PLRI? A: The Horii circle describes the sequential soft-tissue disruption from lateral to medial during elbow dislocation. Stage 1 = LUCL, Stage 2 = + posterolateral capsule, Stage 3 = + radial collateral, Stage 4 = + anterior/posterior capsule, Stage 5 = + MCL (complete dislocation). PLRI represents an incomplete stage; recognising the stage guides reconstruction magnitude.
Treatment Question
Q: What are the indications and graft options for LUCL reconstruction? A: Indications: symptomatic PLRI greater than 3-6 months, positive pivot-shift, failed non-operative care. Graft options: palmaris longus (preferred), gracilis, or ipsilateral triceps tendon strip. The graft is passed through isometric humeral and ulnar bone tunnels and tensioned at 30-40 degrees flexion.
Test Question
Q: Which clinical test has the highest sensitivity for symptomatic PLRI in the office setting? A: The chair push-up test (greater than 90 percent sensitivity). The patient pushes up from a chair with forearms supinated; reproduction of posterolateral pain or instability is positive. The lateral pivot apprehension sign is equally useful and often easier to elicit.
Guidelines, Registries & Global Practice
Global Epidemiology
- PLRI occurs worldwide after simple elbow dislocation (incidence 5-10 percent of dislocations develop chronic instability)
- Overhead athletes and gymnasts have higher rates due to repetitive varus stress
- Iatrogenic PLRI remains a recognised complication of lateral epicondylitis release in all regions
- Missed diagnosis is the most common reason for late presentation globally
Practice Variation by Resource Setting
- High-resource: MRI + arthroscopic assessment, anatomic graft reconstruction with anchors
- Limited-resource: Clinical diagnosis with stress fluoroscopy, palmaris graft through bone tunnels
- Universal principle: Outcome depends on isometric tunnel placement and postoperative compliance more than implant cost
- Surgery: Concentrated in upper-limb specialist centres; generalists refer chronic cases
Society and Reference Guidance (Side by Side)
| Source | Diagnosis emphasis | Non-operative care | Surgery / reconstruction |
|---|---|---|---|
| AAOS / ASSH (US) | Pivot-shift under anesthesia, MRI in supination | Protected motion 6-12 weeks, reassess stability | Anatomic LUCL reconstruction with autograft |
| BSSH / BOA (UK) | Clinical tests + stress views, MRI for planning | Hinged bracing, avoid supinated loading | Graft reconstruction when symptoms persist greater than 6 months |
| AO Foundation | Recognise Horii circle pattern on MRI | Early protected pronated motion | Isometric graft placement critical; document technique |
| ESSKA / European | Apprehension and chair push-up as screening | Physiotherapy-led, 3-month trial minimum | Triceps or gracilis graft when palmaris absent |
Registry and Evidence Note
There is no dedicated elbow instability registry comparable to joint arthroplasty registries. Evidence is derived from prospective cohorts and anatomic studies rather than randomised trials. The consistent message across all guidelines is: diagnose with pivot-shift testing, allow 3-6 months for potential healing, then reconstruct isometrically with autograft when symptoms persist. Documentation of the Horii stage and tunnel positions improves audit and outcome analysis.
Documentation Essentials (Globally Applicable)
Record in every post-dislocation elbow:
- Pivot-shift test result (positive/negative, under anesthesia if required)
- Chair push-up and apprehension signs
- MRI findings of LUCL and cartilage status
- Time from injury and response to non-operative care A missed PLRI diagnosis leading to chronic instability and secondary arthritis is an avoidable source of morbidity worldwide. Always perform and document lateral stability testing after elbow dislocation reduction.
Controversies & Areas of Uncertainty
Optimal timing of reconstruction
Most surgeons wait 3-6 months after dislocation before offering reconstruction. Earlier surgery risks operating on injuries that would have healed. Later surgery risks secondary cartilage damage. No high-quality data defines the exact threshold.
Graft choice and fixation
Palmaris longus, gracilis, and triceps all report good outcomes. Suture anchors versus interference screws versus bone tunnels have no comparative trials. Surgeon experience and graft availability drive choice rather than evidence.
Role of arthroscopy
Arthroscopy can confirm chondral damage and perform capsular plication, but ligament reconstruction remains an open procedure. Whether arthroscopic plication adds value in early-stage PLRI is debated.
Return to sport criteria
Most protocols allow return at 6-9 months, but objective criteria (isokinetic strength, pivot-shift elimination, patient-reported stability) vary widely between centres. No consensus exists on the safest timeline.
POSTEROLATERAL ROTATORY INSTABILITY (PLRI)
Clinical summary
Key Anatomy
- •LUCL originates lateral epicondyle, inserts supinator crest of ulna
- •Primary restraint to posterolateral rotation and varus
- •Secondary restraints: radial collateral ligament, posterolateral capsule
- •Radial head is important secondary stabilizer when LUCL deficient
Diagnosis
- •Pivot-shift test: gold standard (subluxation at 40-60 degrees flexion)
- •Lateral pivot apprehension and chair push-up tests highly sensitive
- •MRI in supination best visualises LUCL discontinuity
- •Always test stability after simple elbow dislocation
Horii Circle Stages
- •Stage 1: LUCL tear only - pivot-shift positive
- •Stage 2: + posterolateral capsule - increased external rotation
- •Stage 3: + radial collateral - gross subluxation
- •Stage 4-5: complete dislocation with MCL involvement
Treatment Algorithm
- •Acute post-dislocation: protected motion 3-6 months, reassess
- •Symptomatic greater than 3-6 months: LUCL reconstruction
- •Graft options: palmaris longus, gracilis, triceps tendon
- •Tension graft at 30-40 degrees flexion, forearm pronated
Complications
- •Recurrent instability: 5-15 percent if non-isometric tunnels
- •Stiffness: 10-20 percent, worse with prolonged immobilisation
- •Radial nerve or PIN injury: rare but reported with Kocher approach
- •Secondary OA: common if chronic subluxation untreated