Courtesy: Michell Ruiz MD
Past President, Mexican Shoulder and ELbow Society
Introduction
Posterolateral Rotatory Instability (PLRI) is the most common pattern of elbow instability.
Key facts:
- Frequently underdiagnosed.
- Common cause of chronic lateral elbow pain.
- Often develops after elbow dislocation.
- May be mistaken for lateral epicondylitis or chronic elbow pain syndromes.
Historical Background
- Residual instability after elbow dislocation was recognized in 1966.
- PLRI was clearly defined by O’Driscoll in 1991.
- Since then, its pathomechanics and treatment principles have been extensively studied.
Elbow Stability
The elbow is inherently stable because of:
Bony Stability
- Trochlea
- Trochlear notch of ulna
- Radiocapitellar articulation
Ligamentous Stability
- Lateral collateral ligament complex
- Medial collateral ligament complex
Dynamic Stability
- Muscles crossing the elbow joint
Lateral Ligament Complex
The lateral ligament complex consists of:
Lateral Ulnar Collateral Ligament (LUCL)
Most important stabilizer.
Functions:
- Prevents varus instability
- Prevents external rotation of the forearm
- Prevents posterolateral rotatory instability
Radial Collateral Ligament (RCL)
Provides lateral support.
Annular Ligament
Maintains radial head stability.
Posterolateral Ligament
Recently recognized as an important stabilizing structure.
Functions:
- Enhances stability during forearm supination
- Controls radial head translation
Deficiency causes:
- Increased radial head translation
- Rotational instability
Etiology
Acute Causes
Elbow Dislocation
Most common cause.
Usually:
- Posterolateral elbow dislocation
Chronic Causes
Failed Healing of LUCL
Following:
- Elbow dislocation
- Lateral ligament injury
Cubitus Varus
Produces chronic varus loading.
Repeated Steroid Injections
Can weaken the lateral ligament complex.
Generalized Ligament Laxity
Predisposes to instability.
Pathomechanics
The injury follows a sequential pattern:
Stage 1
Lateral collateral ligament complex fails.
Stage 2
Anterior capsule becomes disrupted.
Stage 3
Medial collateral ligament acts as a pivot.
Result:
- Radius and ulna rotate externally away from the humerus.
- Radial head subluxes posteriorly.
- Forearm undergoes posterolateral rotatory displacement.
Clinical Presentation
Symptoms
Lateral Elbow Pain
Most common symptom.
Mechanical Symptoms
- Clicking
- Catching
- Snapping
Sense of Instability
Patients often report:
- Elbow feels loose
- Elbow shifts during activity
Apprehension
Particularly during:
- Push ups
- Rising from a chair
- Weight bearing through the arm
Radiological Evaluation
Plain Radiographs
Drop Sign
Definition:
- Ulnohumeral joint widening greater than 4 mm.
Suggests:
- Persistent ligament insufficiency following elbow dislocation.
MRI Findings
Typical findings include:
- LUCL disruption
- Joint asymmetry
- Radiocapitellar widening
- Fluid at ligament origin
- Capsular injury
MRI Positioning Pearl
- Supination may worsen instability.
- Pronation may improve visualization.
Clinical Examination
Pivot Shift Test
Most specific test.
Technique:
- Elbow extended
- Forearm supinated
- Axial load and valgus stress applied
Positive test:
- Apprehension
- Subluxation of radial head
Usually difficult in awake patients because of pain and guarding.
Posterolateral Drawer Test
Performed at approximately 40° elbow flexion.
Positive finding:
- Excessive posterior translation of the forearm.
Chair Push Up Test
Patient rises from a chair with:
- Forearms supinated
- Elbows extended
Positive test:
- Pain
- Apprehension
- Sense of instability
Relief when the radial head is manually stabilized supports the diagnosis.
Arthroscopic Evaluation
Arthroscopy provides direct assessment of instability.
Findings:
- Radial head subluxation
- Widening of radiocapitellar joint
- Ulnohumeral opening
- Ligament insufficiency
Advantages:
- Confirms diagnosis
- Identifies associated pathology
- Helps surgical planning
Treatment
Non Operative Treatment
Generally ineffective once true instability is established.
Results are unpredictable.
May be considered in:
- Mild symptoms
- Low demand patients
Surgical Treatment
1. Primary Repair
Indications
Acute injuries
Typically:
- Less than 3 weeks old
Advantages
- Preserves native tissue
- Faster recovery
- Less invasive
Requirement
- Accurate anatomical repair
2. Augmented Repair (Reinforcement)
Indications
Subacute injuries
Approximately:
- 3 to 12 weeks
Technique:
- Repair plus synthetic augmentation
Advantages:
- Additional stability during healing
3. Ligament Reconstruction
Most common treatment for chronic PLRI.
Indications
- Chronic instability
- Failed repair
- Poor tissue quality
Graft Options
Autograft:
- Gracilis tendon
- Palmaris longus tendon
Allograft:
- Tendon allograft
Fixation Techniques
Bone Tunnel (Docking Technique)
Commonly used.
Interference Screw Fixation
Alternative method.
Challenges
- Numerous surgical techniques
- Variable outcome reporting
- Graft failure rates up to approximately 15%
4. Ligament Plication
Indications
- Ligament intact but stretched
- Good tissue quality
Can be performed:
- Open
- Arthroscopically
Requires preserved ligament attachments.
Principles of Reconstruction
Important landmarks:
Ulna
- Supinator crest
Humerus
- Center of rotation of capitellum
Graft Tensioning
Optimal position:
- Elbow flexion approximately 30°
- Forearm pronated
- Valgus force applied
Proper tensioning is critical for success.
Role of Arthroscopy
Increasingly used in modern management.
Advantages:
- Minimally invasive
- Better visualization
- Assessment of associated pathology
- Guidance during reconstruction
Limitation:
- Technically demanding
Causes of Chronic Lateral Elbow Pain Related to PLRI
PLRI may coexist with:
- Lateral epicondylitis
- Synovial plica syndrome
- Cartilage lesions
- Previous elbow dislocation
Patients with persistent lateral elbow pain should always be evaluated for instability.
Key Clinical Pearls
- PLRI is the most common form of elbow instability.
- The LUCL is the primary stabilizer against posterolateral rotatory instability.
- Previous elbow dislocation is the most common cause.
- Lateral elbow pain with instability symptoms should raise suspicion for PLRI.
- The pivot shift test is the most specific clinical test.
- MRI and arthroscopy are valuable diagnostic tools.
- Established instability usually requires surgery.
- Early diagnosis and treatment provide the best outcomes.
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