Peroneal Tendon Dislocation

1. Clinical Overview

Summary

Peroneal Tendon Dislocation (also called subluxation) is the anterior displacement of the peroneus brevis and/or longus tendons out of the retromalleolar groove, caused by failure of the Superior Peroneal Retinaculum (SPR). This uncommon but frequently misdiagnosed injury typically occurs during forceful contraction of the peroneals while the foot is dorsiflexed and everted (e.g., skiing "caught an edge," football tackles from behind, ballet dancers). [1,2]

Acute injuries are commonly mistaken for lateral ankle sprains, leading to delayed diagnosis and chronic instability. The hallmark clinical feature is a painful "snapping" or "popping" sensation at the posterolateral ankle. Surgical reconstruction (groove deepening + SPR repair) is the gold standard for active patients, as conservative management has high failure rates (> 50% in athletes). [3,4]

Key Facts

• The Restraint: The SPR rarely tears in its midsubstance; instead, it strips off the fibula. In 90% of cases, the retinaculum avulses with a distinct periosteal sleeve (or bone fragment) off the lateral malleolus, creating a "false pouch" where the tendons can slide underneath. [1,5]

• The Groove: The retromalleolar groove is shallow or flat in approximately 20% of the population, significantly predisposing to dislocation. Anatomical variations including low-lying peroneus brevis muscle belly and presence of peroneus quartus muscle also increase risk. [2,6]

• Fleck Sign: A small cortical avulsion fracture visible on the lateral border of the distal fibula on radiographs. This finding is pathognomonic for SPR rupture (Eckert-Davis Grade III injury). [1,7]

• Associated Pathology: Longitudinal splits of the peroneus brevis tendon occur in up to 75% of chronic cases due to repetitive subluxation and impingement against the fibular edge. [8,9]

Clinical Pearls

"The Snapping Ankle": If a patient reports their ankle "pops out" or "clicks," ask them to reproduce it. They will typically circumduct the foot and evert forcefully. You will see and feel the tendons snap anteriorly over the fibular ridge. [3]

"Mistaken for ATFL": Initial examination often reveals swelling over the lateral malleolus region. The critical distinguishing feature is that tenderness is posterior to the fibula (peroneals), not anterior (ATFL/lateral ankle ligaments). [10]

"Prognostic Failure": Treating a true dislocation in a standard walker boot fails because the tendons remain subluxed anteriorly inside the boot. They must be anatomically reduced and held in a below-knee cast in slight plantarflexion and inversion to maintain reduction. [4,11]

"High-Risk Calcaneal Fractures": Peroneal tendon dislocation occurs in 13.9% of calcaneal fractures, particularly joint depression type (Essex-Lopresti) and Sanders Type A fractures. Consider screening MRI or ultrasound in these patients. [12]

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2. Epidemiology

Incidence and Demographics

• Overall Incidence: Peroneal tendon dislocation represents less than 1% of all ankle injuries in the general population but is significantly underdiagnosed. True incidence is likely higher due to missed acute injuries. [2,13]

• Athletic Population: Incidence increases to 0.3-0.5% in athletic populations, particularly in sports requiring cutting movements, jumping, and sudden direction changes. [3,14]

• Age Distribution: Bimodal distribution - young athletes (peak 20-30 years) for acute traumatic injuries, and middle-aged recreational athletes (40-50 years) for chronic/degenerative presentations. [4]

• Gender: Slight male predominance (M:F ratio approximately 3:2) in athletic populations, reflecting participation in high-risk sports. [6]

High-Risk Activities

Risk Factors

Anatomical Predispositions: [2,6,15]

• Shallow or flat retromalleolar groove (20% of population)
• Absent or hypoplastic fibrocartilaginous ridge
• Low-lying peroneus brevis muscle belly
• Presence of peroneus quartus muscle (up to 22% of population)
• Hindfoot varus alignment (cavus foot)

Acquired Risk Factors:

• Previous lateral ankle sprains with ligamentous laxity
• Chronic lateral ankle instability
• Prior calcaneal fractures (13.9% develop peroneal dislocation) [12]
• Generalized ligamentous laxity/hypermobility syndromes

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3. Aetiology and Pathophysiology

Surgical Anatomy

Peroneal Tendons:

• Peroneus Brevis: Originates from distal two-thirds of lateral fibula, courses anteriorly and medially to peroneus longus in the retromalleolar groove, inserts on base of 5th metatarsal. Primary foot evertor and weak plantarflexor.
• Peroneus Longus: Originates from proximal lateral fibula, courses posteriorly and laterally in the groove, passes under cuboid, inserts on base of 1st metatarsal and medial cuneiform. Functions in foot eversion, plantarflexion, and lateral arch support.

Superior Peroneal Retinaculum (SPR):

• Primary restraint preventing anterior dislocation
• Fibrocartilaginous structure spanning from posterolateral fibular ridge to lateral calcaneus
• Average thickness 0.9-1.2 mm, width 10-15 mm
• Reinforced superiorly by crural fascia and inferiorly by inferior peroneal retinaculum
• Blood supply from peroneal artery branches - relatively hypovascular contributing to poor healing

Retromalleolar Groove:

• Depth varies significantly: shallow (less than 2 mm), normal (2-4 mm), deep (> 4 mm)
• Deepened by fibrocartilaginous ridge arising from posterior fibula
• Flat or convex grooves in 11-20% of population - major predisposing factor
• Groove orientation is oblique (20-30° from vertical)

Peroneal Sheath and Septum:

• Common synovial sheath posterior to lateral malleolus
• Separate sheaths distal to malleolus
• Intersheath septum can be absent or attenuated (predisposing to intrasheath subluxation)

Mechanism of Injury

Acute Traumatic Dislocation: [1,3,16]

The classic mechanism involves:

1. Forced dorsiflexion of the ankle (tibiotalar joint > 90°)
2. Simultaneous forceful contraction of peroneals (eversion attempt)
3. Sudden reflex muscle contraction to prevent inversion injury

This creates a "bowstring" effect where the taut peroneal tendons pull anteriorly against the SPR with peak force. The SPR typically fails at its fibular attachment (stripping periosteum ± bone fragment) rather than midsubstance tearing.

Chronic Repetitive Subluxation:

Repetitive microtrauma in anatomically predisposed individuals:

• Shallow retromalleolar groove provides insufficient mechanical restraint
• Repeated minor subluxation events stretch and attenuate SPR
• Progressive tendon degeneration and longitudinal splitting
• Eventually presents as symptomatic chronic instability

Classification: Eckert-Davis (Modified by Oden)

This classification describes the anatomical pattern of SPR failure: [1,7]

Additional Classification Considerations:

• Acute vs Chronic: Acute (less than 6 weeks), Subacute (6 weeks-6 months), Chronic (> 6 months)
• Intrasheath Subluxation: Unique subtype where PL and PB tendons exchange positions within intact SPR - diagnosed on dynamic ultrasound [17]

Pathophysiology of Chronicity

Missed Acute Diagnosis: [3,4,10]

• Initial presentation mimics lateral ankle sprain (swelling, ecchymosis, lateral pain)
• Standard ankle X-rays often normal (unless Grade III with fleck sign)
• Patients treated with RICE, immobilization, physiotherapy without reduction
• SPR heals in lengthened, incompetent position → recurrent subluxation

Progressive Tendon Degeneration: [8,9]

• Chronic subluxation causes repetitive impingement of peroneus brevis against lateral fibular edge
• Leads to longitudinal splits within tendon substance (75% of chronic cases)
• Intratendinous degeneration, mucoid change, eventual partial/complete tears
• Tenosynovitis and adhesions develop within common sheath

Secondary Complications:

• Sural nerve irritation/neuroma (nerve runs adjacent to peroneal sheath)
• Lateral ankle instability (peroneals are secondary lateral stabilizers)
• Subfibular impingement and pain
• Os peroneum fracture or painful os peroneum syndrome (in 20% with os peroneum)

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4. Clinical Presentation

Symptoms

Acute Presentation: [3,10]

• "Pop" or "snap" sensation at time of injury (pathognomonic when present)
• Posterolateral ankle pain and swelling (behind lateral malleolus)
• Immediate difficulty with weight-bearing and push-off
• Sensation of ankle "giving way" or "sliding out of place"
• Often initially diagnosed as "lateral ankle sprain"

Chronic Presentation: [4,6]

• Recurrent snapping, clicking, or popping with specific movements (walking on uneven ground, cutting, jumping)
• Painful subluxation events that patient can often reproduce voluntarily
• Posterolateral ankle pain exacerbated by activity
• Feeling of lateral ankle instability ("ankle doesn't feel secure")
• Difficulty with single-leg heel raise and toe-off during gait
• Pain worse with eversion activities, prolonged standing

Signs

Inspection:

• Swelling in retromalleolar region (described as "retromalleolar biscuit" in acute phase)
• Ecchymosis tracking from lateral malleolus distally
• In chronic cases: visible tendon subluxation during active eversion
• May observe high-arched foot (cavus) - predisposing factor

Palpation:

• Point tenderness: Posterior to lateral malleolus (NOT anterior like ATFL sprain)
• Tenderness along course of peroneal tendons to 5th metatarsal base
• Palpable "click" or "snap" as tendons sublux over fibular edge
• Thickened, tender peroneal sheath in chronic cases
• Assess for sural nerve tenderness (may indicate neuritis/neuroma)

Special Tests: [3,10,18]

Range of Motion:

• Usually full passive ROM unless acute phase swelling
• Pain at extremes of dorsiflexion and eversion
• Weakness with resisted eversion (pain inhibition or tendon pathology)

Gait Assessment:

• Antalgic gait favoring lateral border of foot
• Difficulty with single-leg heel raise on affected side
• Visible tendon subluxation during toe-off phase in chronic cases

Red Flag Features

⚠️ Clinical Red Flags:

• Open injury or skin tenting (risk of compartment syndrome if associated with fracture)
• Neurovascular compromise (sural nerve injury, peroneal artery injury - rare)
• Associated fractures (fibula, calcaneus, 5th metatarsal base)
• Significant soft tissue compromise requiring urgent reduction

⚠️ Imaging Red Flags:

• Fleck sign on radiograph (Grade III injury - indicates high-energy mechanism, higher instability)
• Large cortical avulsion fragments (may require ORIF rather than soft tissue repair alone)
• Associated calcaneal fracture (13.9% have peroneal dislocation)
• Longitudinal split tear > 50% tendon diameter (requires repair/reconstruction)

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5. Differential Diagnosis

Primary Differentials

Must-Not-Miss Diagnoses

1. Compartment Syndrome: If associated with high-energy trauma, calcaneal fracture, or crush injury. Assess all compartments including lateral.

2. Open Injury/Skin at Risk: Particularly with large avulsion fragments that tent skin.

3. Combined Injuries: Peroneal dislocation + lateral ligament rupture + syndesmosis injury ("terrible triad" of lateral ankle). Requires comprehensive surgical planning.

4. Calcaneal Fracture: 13.9% of calcaneal fractures have associated peroneal dislocation. Always assess peroneals when treating calcaneal fractures. [12]

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6. Investigations

First-Line Imaging

Plain Radiographs: [7,10]

AP, Lateral, Mortise views of ankle:

• Fleck Sign: Small cortical avulsion from posterolateral fibula (pathognomonic for Grade III SPR avulsion) - seen in 15% of cases
• Assess for associated fractures: lateral malleolus, 5th metatarsal base, calcaneus
• Evaluate for chronic changes: fibular cortical irregularity, periosteal reaction
• Os peroneum assessment: normal position vs displacement (> 5 mm proximally indicates peroneus longus tear)

Comparative/Stress Views (rarely used):

• Eversion stress view with ankle dorsiflexed may show lateral displacement of tendons
• Generally superseded by dynamic ultrasound

Sensitivity: 15-20% (only Grade III with bony avulsion) | Specificity: 95-100% when fleck sign present

Gold Standard Imaging

Magnetic Resonance Imaging (MRI): [2,6,10,19]

Standard Protocol: Axial, coronal, and sagittal sequences with T1, T2, STIR, and PD fat-saturated images

Key Findings:

Advantages:

• Comprehensive soft tissue assessment
• Evaluates associated pathology (tendon tears, bone bruising, lateral ligaments)
• Excellent for surgical planning (groove morphology, extent of tendon damage)

Limitations:

• Static imaging - may miss subluxation if tendons reduced at time of scan
• Cannot assess dynamic instability
• Cost and availability

Sensitivity: 80-90% | Specificity: 85-95%

Dynamic Imaging

Diagnostic Ultrasound: [10,17,18]

Static Protocol:

• High-frequency linear probe (12-18 MHz)
• Axial and longitudinal views of peroneal tendons
• Assess tendon morphology, SPR integrity, groove depth

Dynamic Protocol (MOST SENSITIVE TEST): [17,18]

• Patient actively dorsiflexes and everts ankle while scanning in real-time
• Direct visualization of tendons subluxing anteriorly over fibular edge
• Can differentiate:

• Anterolateral subluxation (both tendons move anterior to fibula)
• Intrasheath subluxation (tendons exchange positions within intact SPR)

• Can inject local anesthetic into peroneal sheath and repeat dynamic scan to confirm diagnosis if patient too painful

Advantages:

• Best test for confirming dynamic instability (> 95% sensitivity when dynamic protocol used)
• Real-time assessment during provocative maneuvers
• Cost-effective, no radiation, point-of-care
• Operator-dependent but highly accurate in experienced hands

Sensitivity: Static 60-70%, Dynamic 90-98% | Specificity: 85-95%

Advanced/Adjunct Imaging

CT Scan:

• Not routinely indicated for soft tissue pathology
• Useful for:

• Associated calcaneal fractures (preoperative planning)
• Complex bony avulsion fragments requiring ORIF
• 3D reconstruction for groove morphology assessment

Tendoscopy (Diagnostic): [20]

• Minimally invasive endoscopic evaluation of peroneal sheath
• Direct visualization of tendon pathology, synovitis, tears
• Can convert to therapeutic procedure
• Indications: Equivocal imaging, persistent symptoms despite negative imaging

Investigative Algorithm

POSTEROLATERAL ANKLE PAIN + SNAPPING
              ↓
      Clinical Examination
         Subluxation Test
              ↓
         POSITIVE?
     ┌─────────┴─────────┐
    YES                  NO
     ↓                    ↓
Plain X-Rays        Consider Alternative Dx
(Fleck sign?)       (ATFL sprain, tendonitis)
     ↓
  MRI or Dynamic US
     ↓
Confirm: SPR injury
Assess: Groove depth
        Tendon tears
     ↓
SURGICAL PLANNING

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7. Classification and Grading

Eckert-Davis Classification (Modified by Oden)

As described in Section 3 - remains the standard surgical classification system used for operative planning. [1,7]

Temporal Classification

Functional Classification

Type A (Stable Subluxation):

• Tendons sublux only during specific provocative movements
• No spontaneous subluxation during normal activities
• May respond to conservative management in non-athletes

Type B (Unstable/Recurrent Dislocation):

• Frequent spontaneous subluxation during normal activities
• Patient can often voluntarily reproduce subluxation
• Invariably requires surgical stabilization

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8. Management

Conservative (Non-Operative) Management

Indications

• Acute first-time injury (Grade I or II) in low-demand, sedentary patient
• Patient medical comorbidities precluding surgery
• Patient preference after informed consent regarding high failure rates

Contraindications to Conservative Management

• Grade III injury with bony avulsion (high instability)
• High-level athletes requiring return to sport
• Chronic recurrent subluxation (failed conservative treatment)
• Associated large tendon tears requiring repair

Protocol [4,11]

Phase 1: Immobilization (0-6 weeks)

• Below-knee non-weight-bearing cast (NOT removable boot - critical!)
• Position: Ankle in slight plantarflexion (10-15°) and inversion (5-10°)

• "Rationale: Relaxes peroneals, maintains tendons in reduced position in groove"

• Weekly clinical review first 2 weeks to ensure reduction maintained
• Transition to weight-bearing at 4 weeks in cast

Phase 2: Progressive Mobilization (6-10 weeks)

• Transition to CAM walker boot with gradual increase in ROM
• Peroneal strengthening exercises (isometric initially)
• Proprioceptive training
• Continue avoiding forceful eversion and dorsiflexion

Phase 3: Return to Activity (10+ weeks)

• Progressive functional rehabilitation
• Sport-specific training
• Consider ankle brace for high-risk activities
• Return to full activity at 12-16 weeks if asymptomatic

Outcomes of Conservative Management

Success Rates: [3,4,11]

• Overall recurrence rate: 30-50%
• Athletes: 50-70% failure rate (re-dislocation or persistent instability)
• Sedentary patients: 20-30% failure rate
• Grade I: Better outcomes than Grade II/III
• Acute presentation: Better outcomes than delayed treatment

Reasons for Failure:

• Inadequate immobilization (walker boot instead of cast)
• Incorrect positioning (neutral rather than plantarflexion/inversion)
• Early return to provocative activities
• Anatomical predisposition (shallow groove, SPR laxity)
• Non-compliance with rehabilitation protocol

Conversion to Surgery:

• Any patient with recurrent subluxation after conservative trial should undergo surgical stabilization
• No benefit to repeated attempts at conservative management

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Surgical Management

Indications [3,4,6,11]

Absolute Indications:

• Acute Grade III (bony avulsion) in any patient planning to return to activity
• High-level athletes with acute injury (to minimize time to return to sport and prevent chronicity)
• Chronic symptomatic instability (failed conservative management)
• Recurrent subluxation interfering with activities of daily living

Relative Indications:

• Acute Grade I/II in active recreational athletes
• Associated large peroneal tendon tears requiring repair
• Patient preference after failed 6-week trial of immobilization

Pre-Operative Planning

• Review MRI for:

• SPR injury pattern and tissue quality
• Groove morphology (depth, shape) → need for deepening
• Peroneal tendon pathology (splits, tears) → need for repair
• Associated pathology (lateral ligaments, os peroneum)

• Discuss realistic expectations:

• Success rate > 90% with appropriate technique
• "Return to sport timeline: 3-4 months for athletes"
• Potential for sural nerve symptoms
• Small risk of recurrence (3-5%) even with optimal surgery

Surgical Techniques

1. Direct SPR Repair/Reattachment [3,6,11]

Indications:

• Acute injuries with good tissue quality
• Adequate groove depth (> 2 mm)
• No or minimal tendon pathology

Technique:

• Incision: Curvilinear along course of peroneals posterior to fibula (7-10 cm)
• Carefully identify and protect sural nerve (runs with lesser saphenous vein)
• Open peroneal sheath, inspect tendons for tears
• Identify avulsed SPR (usually stripped from fibula with periosteum)
• Create fibular bone trough or drill 2-3 small holes (2.0-2.5 mm) in posterolateral fibula
• Reattach SPR using:

• Suture anchors (preferred by many surgeons) - 2-3 mini anchors
• Transosseous sutures through drill holes

• Use non-absorbable or strong absorbable suture (#2 FiberWire, Ethibond)
• Repair should be taut with ankle in neutral position
• Close sheath and skin

Outcomes: 75-85% good-excellent results, but higher recurrence (10-15%) if groove not deepened [4]

2. Groove Deepening (Gould Modification) [1,3,6,21]

Indications:

• Shallow or flat retromalleolar groove (less than 2 mm depth on MRI)
• Chronic instability
• Revision surgery for failed prior repair
• Preferred technique for athletes to minimize recurrence

Technique:

• Same approach as SPR repair
• After inspecting tendons and SPR:

1. Create periosteal flaps from lateral fibula
2. Use curved osteotome to carefully elevate outer cortical layer of fibula (5-10 mm × 15-20 mm)
3. Remove cancellous bone from beneath cortical "lid" to create deeper groove
4. Tap cortical lid down into new deeper position (3-5 mm depth)
5. Can use small tamp or elevator to mold groove
6. Reattach SPR to fibula (as above)

• Ensure tendons sit comfortably in deepened groove without over-tightening
• Avoid excessive depth (can cause stenosis/entrapment)

Outcomes: 90-95% good-excellent results, recurrence rate less than 5% [3,4,6]

3. Bone Block Procedures (Historical - Rarely Used)

Techniques:

• Watson-Jones: Transfer fibular bone block to create lateral buttress
• Kelly: Fibular periosteal flap
• Largely abandoned due to:

• Risk of fracture through block
• Sural nerve complications
• No superiority to groove deepening

4. Peroneal Tendon Repair/Tubularization [8,9]

Indications:

• Associated longitudinal splits in peroneus brevis (75% of chronic cases)
• Partial-thickness tears
• Degenerative tendon changes

Technique:

• During exploration for SPR repair, inspect both tendons circumferentially
• Longitudinal split tears of peroneus brevis:

• Debride degenerative tissue
• Tubularize tendon with running absorbable suture (3-0 or 4-0 V-Loc)
• "If > 50% tendon damaged, consider:"
  • Tenodesis to peroneus longus
  • Allograft augmentation
  • In severe cases: excision and tenodesis

• Peroneus longus tears: Similar principles; less common

5. Endoscopic/Tendoscopic Techniques [20,22]

Indications:

• Diagnostic uncertainty
• Isolated intrasheath subluxation (no SPR damage)
• Mild tendon pathology amenable to debridement
• Minimally invasive approach in appropriate cases

Technique:

• Two-portal technique (proximal and distal to malleolus)
• 4 mm arthroscope, small-joint instrumentation
• Synovectomy, tendon debridement possible
• SPR repair challenging endoscopically - usually requires mini-open conversion
• Groove deepening not feasible endoscopically

Outcomes: Good results for selected cases, but limited by inability to address groove and robust SPR repair [20]

Surgical Algorithm

PERONEAL TENDON DISLOCATION - SURGICAL CANDIDATE
                    ↓
          Review Imaging (MRI)
                    ↓
        ┌───────────┴───────────┐
  SHALLOW GROOVE           NORMAL GROOVE
   (less than 2 mm depth)            (> 2 mm depth)
        ↓                         ↓
 Groove Deepening          SPR Repair Alone
  + SPR Repair              (acute injuries)
        ↓                         ↓
  Inspect Tendons           Inspect Tendons
        ↓                         ↓
  Longitudinal Split?       Longitudinal Split?
    YES → Repair             YES → Repair
    NO → Proceed              NO → Proceed
        ↓                         ↓
  Close, Immobilize         Close, Immobilize

Post-Operative Protocol [3,6,11]

Phase 1: Immobilization (0-2 weeks)

• Below-knee splint in neutral position
• Non-weight-bearing (crutches, scooter)
• Elevation, ice, analgesia
• Toe mobilization exercises

Phase 2: Protected Weight-Bearing (2-6 weeks)

• Transition to CAM walker boot at 2 weeks (once wound healed)
• Gentle ROM exercises in boot (plantarflexion/dorsiflexion only - NO eversion)
• Progressive weight-bearing to full by 6 weeks
• Isometric peroneal strengthening (week 4+)

Phase 3: Progressive Rehabilitation (6-12 weeks)

• Wean from boot at 6 weeks
• Active ROM all planes
• Resistance exercises (theraband eversion, inversion)
• Proprioceptive training (wobble board, single-leg stance)
• Gait retraining
• Pool exercises, cycling

Phase 4: Return to Sport (12+ weeks)

• Sport-specific functional rehabilitation
• Cutting, jumping, agility drills
• Return to full activity at 3-4 months for non-contact sports
• Contact/high-risk sports: 4-6 months
• Consider ankle taping/bracing for first 6 months return to sport

Critical Post-Op Considerations:

• Avoid eversion exercises for first 6 weeks - highest risk of re-rupture
• Sural nerve monitoring (25% transient numbness, less than 5% permanent)
• Delayed wound healing in smokers - strict smoking cessation advised

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Special Populations

High-Performance Athletes: [3,14]

• Early surgical intervention preferred (avoid chronicity, faster return to sport)
• Groove deepening + SPR repair recommended even in acute Grade I/II
• Accelerated rehabilitation under specialist supervision
• Return to sport criteria: Full ROM, > 90% strength vs contralateral, pain-free cutting/jumping
• Expected timeline: 3-4 months to full unrestricted activity

Pediatric/Adolescent Patients:

• Open physes: Avoid transosseous tunnels across physis
• Use suture anchors or transosseous sutures away from growth plate
• Generally excellent outcomes similar to adults
• Higher tendency to ligamentous laxity - consider more robust reconstruction

Patients with Generalized Hypermobility:

• Higher failure rates with conservative management
• May require augmentation (allograft SPR reconstruction)
• Prolonged immobilization and rehabilitation
• Counsel regarding potential for recurrence despite optimal surgery

Calcaneal Fracture Patients: [12]

• Screen for peroneal dislocation with MRI or ultrasound
• Can address simultaneously during calcaneal ORIF
• Alternatively, staged repair at time of hardware removal (18-24 months) - similar outcomes
• Sanders Type A and joint depression fractures highest risk

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9. Complications

Surgical Complications

Non-Operative Complications

• Recurrent Instability: 30-50% after conservative management [4,11]
• Chronic Lateral Ankle Instability: Peroneals are secondary lateral stabilizers; chronic instability can lead to or coexist with ATFL insufficiency
• Progressive Tendon Degeneration: Chronic subluxation leads to longitudinal splits, tears, tendinosis
• Activity Limitation: Unable to return to high-level sports or physically demanding work
• Arthritis: Long-term sequelae unclear, but chronic instability may contribute to lateral ankle/subtalar arthritis

Medico-Legal Considerations

• Missed Diagnosis: High medicolegal risk if misdiagnosed as simple ankle sprain and appropriate imaging not obtained [10]
• Documentation: Document specific examination findings (posterior tenderness, subluxation test)
• Informed Consent: Discuss high failure rates of conservative management, especially in athletes
• Sural Nerve: Explicitly counsel about risk of numbness/neuroma (most common complication)

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10. Prognosis

Natural History (Untreated)

• Acute injuries left untreated → 70-90% progress to chronic recurrent subluxation
• Chronic instability → Progressive tendon degeneration (splits, tears) in 75%
• Long-term disability → Persistent pain, activity limitation, possible secondary lateral ankle instability
• Arthritic changes → Theoretical risk but not well-documented in literature

Outcomes with Treatment

Conservative Management: [4,11]

• Success rate (no recurrence): 50-70% in sedentary patients, 30-50% in athletes
• Time to return to activity: 3-4 months
• Patient satisfaction: Variable (50-70% satisfied even with occasional subluxation)

Surgical Management: [3,6,21]

Groove Deepening + SPR Repair (Gold Standard):

• Success rate (no recurrence): 90-95%
• Return to sport: 85-95% of athletes return to pre-injury level
• Time to return: 3-4 months (non-contact), 4-6 months (contact sports)
• Patient satisfaction: 85-95% good-excellent results
• Recurrence rate: less than 5%

SPR Repair Alone:

• Success rate: 75-85%
• Recurrence rate: 10-15%
• Generally inferior to combined groove deepening approach in athletes

Tendoscopic/Minimally Invasive:

• Outcomes similar to open techniques for selected patients
• Lower wound complication rate
• Limited data, appropriate case selection critical

Prognostic Factors

Favorable:

• Acute injury (less than 6 weeks)
• Young, healthy patient
• Good tissue quality at surgery
• Groove deepening performed
• Compliance with post-operative protocol
• No associated tendon tears

Unfavorable:

• Chronic injury (> 6 months)
• Multiple previous dislocations
• Severe tendon degeneration/large tears
• Revision surgery
• Generalized hypermobility
• Smoking, diabetes, poor healing
• Non-compliance with rehabilitation

Long-Term Outcomes

• 5-year follow-up: 90-95% maintain stable reconstruction [6]
• Return to sport: 85-95% return to pre-injury level, 5-10% require sport modification
• Recurrence: Most occur within first 12 months; rare after 2 years if compliant with rehab
• Quality of life: Significant improvement in ankle function scores, activity levels, patient satisfaction

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11. Prevention and Screening

Primary Prevention

Anatomical Risk Screening:

• In high-risk athletes (alpine skiing, football, ballet), consider baseline MRI or ultrasound to identify:

• Shallow retromalleolar groove
• Congenital SPR laxity
• Peroneus quartus or low-lying brevis muscle belly

• Not routinely recommended due to cost and low absolute risk, but may be considered in elite athletes

Neuromuscular Training:

• Proprioceptive exercises (single-leg balance, wobble board)
• Peroneal strengthening (eversion exercises with resistance band)
• Sport-specific ankle stability training
• Evidence mixed, but may reduce overall ankle injury risk

Equipment Modifications:

• Alpine skiing: Properly fitted boots, consideration of high-top boots for known laxity
• Football: Ankle taping or bracing for previous ankle injuries
• Ballet: Gradual progression in demi-pointe work, avoiding forceful dorsiflexion

Secondary Prevention (After Acute Injury)

Early Accurate Diagnosis:

• High index of suspicion in posterolateral ankle injuries
• Perform specific examination tests (subluxation test)
• Low threshold for MRI or dynamic ultrasound if clinical suspicion

Appropriate Acute Management:

• If conservative approach chosen: Strict immobilization in cast (plantarflexion/inversion), NOT boot
• Consider early surgical referral for high-level athletes

Post-Injury Rehabilitation:

• Address peroneal weakness
• Proprioceptive retraining
• Gradual return to sport with taping/bracing initially

Tertiary Prevention (Preventing Recurrence After Surgery)

• Compliance with post-operative protocol (critical)
• Avoid premature return to eversion-loading activities
• Progressive functional rehabilitation under physiotherapy supervision
• Consider ankle bracing for first 6-12 months return to high-risk sports
• Long-term peroneal strengthening and proprioceptive exercises

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12. Key Guidelines and Consensus Statements

Current Evidence Base

There are no formal society guidelines specifically for peroneal tendon dislocation from major orthopedic societies (AAOS, BOFAS, AOFAS). Management is based on case series, expert opinion, and biomechanical studies. [1-6]

Expert Consensus Recommendations

Diagnosis: [2,10,18]

• Clinical examination (subluxation test) combined with imaging
• MRI or dynamic ultrasound as gold standard
• Low threshold for imaging in posterolateral ankle pain with "snapping" history

Conservative Management: [4,11]

• Reserved for acute, low-demand patients
• Strict below-knee cast immobilization (plantarflexion/inversion) for 6 weeks
• High failure rates (30-50%) should be disclosed
• Not recommended for athletes or chronic cases

Surgical Management: [3,6,21]

• Groove deepening + SPR repair is gold standard for athletes
• Acute repair for high-level athletes and Grade III injuries
• Address associated tendon tears (tubularization of longitudinal splits)
• Post-operative immobilization 6 weeks, return to sport 3-4 months

Landmark Studies

1. Eckert & Davis (1976): Original classification of SPR injury patterns - remains standard surgical classification. [1]

2. Porter et al. (2005): Demonstrated superiority of groove deepening vs SPR repair alone in athletes (recurrence 5% vs 15%). [21]

3. Saragas et al. (2016): Case series (n=20) showing 90% good-excellent outcomes with surgical stabilization, no single technique superior. [4]

4. Davda et al. (2017): Comprehensive EFORT review establishing current diagnostic and treatment algorithms. [2]

5. Hosack et al. (2023): Recent systematic review confirming high success rates of operative management (> 90%) with multiple techniques. [3]

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13. Examination Focus (Viva Vault)

Opening Statement

"Peroneal tendon dislocation is an uncommon but frequently misdiagnosed injury involving failure of the superior peroneal retinaculum, allowing the peroneal tendons to sublux anteriorly from the retromalleolar groove. It typically occurs in young athletes during forceful dorsiflexion and eversion, most commonly in alpine skiing. The classic presentation is posterolateral ankle pain with a 'snapping' sensation. The Eckert-Davis classification describes four grades based on the pattern of SPR avulsion. Surgical management with groove deepening and SPR repair is the gold standard for active patients, with success rates exceeding 90%." [1,3]

Common Viva Questions and Model Answers

Q1: Describe the anatomy of the superior peroneal retinaculum.

A: "The SPR is a fibrocartilaginous band that serves as the primary restraint preventing anterior dislocation of the peroneal tendons. It originates from the posterolateral fibular ridge and inserts on the lateral calcaneus. It spans approximately 10-15 mm in width and reinforces the roof of the common peroneal sheath. The SPR is reinforced superiorly by the crural fascia and inferiorly by the inferior peroneal retinaculum. It has a relatively poor blood supply from peroneal artery branches, which contributes to poor healing after injury." [2]

Q2: What is the Eckert-Davis classification?

A: "The Eckert-Davis classification, modified by Oden, describes four grades of SPR injury based on the anatomical pattern of failure:

• Grade I (51%): SPR strips from the fibula with an intact periosteal sleeve, creating a 'false pouch' where tendons dislocate. Most common.
• Grade II (33%): SPR avulses with the fibrocartilaginous ridge from the retromalleolar groove.
• Grade III (15%): SPR avulses with a cortical bone fragment from the lateral malleolus - the 'fleck sign' visible on X-ray. Indicates high-energy injury.
• Grade IV (less than 1%): Rare - SPR tears from its posterior calcaneal insertion.

This classification guides surgical planning, particularly the need for groove deepening in Grade II/III injuries." [1,7]

Q3: What is the Fleck sign and what is its significance?

A: "The fleck sign is a small cortical avulsion fracture visible on the posterolateral border of the distal fibula on ankle radiographs. It represents a Grade III Eckert-Davis injury where the SPR has avulsed with a bone fragment. This finding is pathognomonic for SPR rupture and indicates a high-energy mechanism. It signifies significant instability and is an indication for surgical stabilization, particularly in active patients. The fleck sign is only visible in approximately 15% of peroneal dislocations, so its absence does not exclude the diagnosis." [1,7]

Q4: How do you differentiate peroneal tendon dislocation from a lateral ankle sprain clinically?

A: "The key differentiating features are:

Location of tenderness: Peroneal dislocation causes tenderness posterior to the fibula in the retromalleolar region, while ATFL sprains cause anterior ankle tenderness.

Mechanism: Peroneal dislocation typically occurs with forced dorsiflexion and eversion during peroneal contraction, whereas ATFL injuries occur with inversion and plantarflexion.

Symptoms: Patients with peroneal dislocation describe a 'pop' or 'snapping' sensation and may report recurrent clicking or subluxation, which is not typical for isolated ATFL injury.

Examination tests: The peroneal subluxation test (resisted eversion in dorsiflexion) will be positive with palpable subluxation, and patients can often reproduce the subluxation voluntarily. ATFL injuries show a positive anterior drawer test.

However, these injuries can coexist, and comprehensive examination of both lateral ligaments and peroneal tendons is essential in lateral ankle injuries." [3,10]

Q5: What is dynamic ultrasound and why is it useful?

A: "Dynamic ultrasound is real-time ultrasonographic assessment of the peroneal tendons during active movement. Using a high-frequency linear probe, the examiner visualizes the tendons in the retromalleolar groove while the patient actively dorsiflexes and everts the ankle. This allows direct visualization of the tendons subluxing anteriorly over the fibular ridge.

It is the most sensitive test for confirming peroneal instability because MRI is static imaging and may show reduced tendons if obtained while tendons are in normal position. Dynamic ultrasound has sensitivity > 95% when performed by experienced operators. It can also differentiate between anterolateral subluxation and intrasheath subluxation, where the peroneus longus and brevis exchange positions within an intact SPR. This distinction has implications for surgical planning." [17,18]

Q6: Describe the Gould modification for groove deepening.

A: "The Gould modification is a surgical technique to deepen the retromalleolar groove to prevent recurrent peroneal subluxation in patients with shallow or flat grooves.

Technique: After exposing the lateral fibula and inspecting the peroneal tendons:

1. Carefully elevate periosteal flaps from the posterolateral fibula
2. Use a curved osteotome to elevate the outer cortical layer as a rectangular 'lid' (approximately 5-10 mm wide × 15-20 mm long)
3. Remove cancellous bone from beneath the cortical layer using curette or rongeur
4. Tap the cortical lid down into the newly created deeper position using a small tamp
5. The final groove depth should be 3-5 mm
6. Reattach the SPR to the fibula over the deepened groove

This technique significantly reduces recurrence rates compared to SPR repair alone - from 10-15% down to less than 5%. It is now considered the gold standard, particularly for athletes and patients with documented shallow grooves on MRI." [1,3,21]

Q7: What are the critical steps in post-operative rehabilitation?

A: "The critical principles are:

Weeks 0-2: Below-knee splint, strict non-weight-bearing. Toe mobilization exercises only. Wound care.

Weeks 2-6: Transition to CAM walker boot. Progressive weight-bearing to full by 6 weeks. Gentle ROM exercises in plantarflexion/dorsiflexion only - crucially, NO eversion exercises during this period as the SPR repair is vulnerable. Isometric peroneal strengthening from week 4.

Weeks 6-12: Wean from boot. Active ROM all planes. Progressive resistance exercises including eversion with theraband. Proprioceptive training with wobble board. Gait retraining.

Weeks 12+: Sport-specific functional rehabilitation. Cutting, jumping, agility drills. Return to full activity typically 3-4 months for non-contact sports, 4-6 months for contact sports.

The most critical aspect is avoiding eversion-loading activities for 6 weeks to protect the SPR repair. Premature eversion exercises are a major cause of surgical failure." [3,6,11]

Q8: What is the most common surgical complication and how do you minimize it?

A: "The most common complication is sural nerve injury, occurring in 5-25% of patients. Most are transient sensory disturbances, but permanent numbness occurs in less than 5% and painful neuromas can develop.

Anatomical considerations: The sural nerve runs with the lesser saphenous vein in close proximity to the peroneal tendon sheath, typically 5-10 mm posterior and slightly superior to the standard surgical incision.

Prevention strategies:

1. Careful incision planning - curvilinear incision along the course of the tendons, avoiding crossing the nerve trajectory
2. Meticulous dissection with early identification of the nerve before opening the sheath
3. Use of loupe magnification or headlight
4. Minimal retraction and avoid excessive pulling on surrounding tissues
5. Gentle soft tissue handling

Management if injury occurs: Most transient symptoms resolve spontaneously over 3-6 months. Persistent neuropathic pain can be managed with gabapentin or pregabalin. Severe cases with neuroma formation may require neuroma excision or relocation, though this is rarely necessary. Patient counseling about this risk is essential during informed consent." [3,6]

High-Yield Exam Topics

For FRCS (Tr&Orth) Trauma & Orthopaedics:

• Eckert-Davis classification (always asked if topic comes up)
• Differential diagnosis from lateral ankle sprain
• Indications for surgery vs conservative management
• Surgical technique (groove deepening)
• Complications (sural nerve)

For Sports Medicine Fellowships:

• Dynamic ultrasound technique and interpretation
• Return-to-sport protocols
• Outcomes data and recurrence rates
• Management of associated tendon tears
• Intrasheath subluxation variant

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14. Common Mistakes (Exam Pitfalls)

❌ Mistake 1: Missing the diagnosis by assuming "just an ankle sprain" ✅ Correct approach: Always palpate posterior to fibula in lateral ankle injuries. Perform peroneal subluxation test. Low threshold for MRI or dynamic US if posterolateral tenderness.

❌ Mistake 2: Treating with a removable walker boot ✅ Correct approach: If attempting conservative management, must use non-removable below-knee cast in plantarflexion and inversion. Boot allows too much movement and tendons remain subluxed.

❌ Mistake 3: Stating that conservative management is appropriate for athletes ✅ Correct approach: High-level athletes should undergo early surgical stabilization due to 50-70% failure rate of conservative treatment and prolonged time to return to sport.

❌ Mistake 4: Performing SPR repair alone in shallow groove ✅ Correct approach: If MRI shows groove depth less than 2 mm, must perform groove deepening in addition to SPR repair to minimize recurrence (reduces from 10-15% to less than 5%).

❌ Mistake 5: Allowing eversion exercises in first 6 weeks post-op ✅ Correct approach: Eversion loading places maximum stress on SPR repair. Avoid eversion exercises until 6 weeks post-op. Premature eversion is a major cause of surgical failure.

❌ Mistake 6: Not addressing longitudinal peroneus brevis tears ✅ Correct approach: 75% of chronic cases have associated splits. Always inspect tendons circumferentially during surgery and tubularize any longitudinal tears to prevent ongoing symptoms.

❌ Mistake 7: Confusing with intrasheath subluxation ✅ Correct approach: Intrasheath subluxation is a distinct entity where PL and PB exchange positions within intact SPR. Requires dynamic US for diagnosis. Different surgical approach (SPR not damaged).

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15. Patient Explanation (Layperson Summary)

What Has Happened?

Your ankle has two important tendons (like strong cords) on the outside called the peroneal tendons. They normally run in a groove behind your ankle bone (fibula), held in place by a tight strap-like ligament called the retinaculum - think of it like a seatbelt holding them in position.

When you injured your ankle, this "seatbelt" tore or pulled away from the bone. Now the tendons can slip forward out of their groove, especially when you move your foot in certain ways. This causes the "popping" or "snapping" feeling you've been experiencing.

Why Not Just a Plaster Cast?

Unlike bone fractures, these tendons and ligaments don't heal reliably with just immobilization. Tendons are very slippery, and once the restraint is torn, they rarely stick back securely in the right position just with a plaster. Studies show that more than half of active people (especially athletes) will have ongoing problems with the tendons continuing to slip if treated with cast alone.

If the "seatbelt" heals in a loose, stretched position, you'll have a permanently clicking, unstable ankle. This can lead to:

• Ongoing pain and swelling
• Difficulty with sports and running
• Progressive damage to the tendons themselves
• Feeling like your ankle is "giving way"

The Surgery Explained

The operation we recommend involves two main components:

1. Reattaching the "Seatbelt" (SPR Repair):

• We make a small incision on the outside of your ankle
• We find the torn ligament and reattach it firmly to the bone using special strong stitches and small anchors
• This recreates the restraint that holds your tendons in place

2. Deepening the Groove (Gould Procedure):

• In many people, the groove behind the ankle bone is naturally shallow, which is why the tendons slipped in the first place
• We carefully deepen this groove by reshaping the bone slightly - imagine creating a deeper channel for the tendons to sit in
• This significantly reduces the chance of the problem happening again (from about 15% risk down to less than 5%)

If We Find Tendon Damage:

• In about 75% of cases, if the tendons have been slipping for a while, they can develop internal splits from rubbing against the bone
• If we find this, we repair it with stitches - like sewing a torn shirt back together

Recovery Timeline

• Weeks 1-2: Splint, no weight on the ankle, crutches
• Weeks 2-6: Walking boot, gradually increasing how much you walk
• Weeks 6-12: Out of boot, physiotherapy to rebuild strength and balance
• 3-4 months: Return to most sports and activities
• 4-6 months: Return to high-level contact sports

Success Rates

• Surgery: More than 90% of patients get back to full activities with no recurrence
• Cast alone: Only 50-70% successful in active people
• Most people are very satisfied with their ankle function after surgery and can return to all their previous sports

Risks to Be Aware Of

• Nerve numbness: There's a small nerve near the tendons. About 5-25% of people notice some numbness on the outside of the foot afterwards. Usually this improves over time, and severe problems are rare (less than 5%).
• Infection/wound healing: Small risk with any surgery (less than 5%)
• Stiffness: Your ankle may be a bit stiff initially but improves with physiotherapy
• Recurrence: Small chance (less than 5%) the tendons could slip again, especially if rehabilitation isn't followed properly

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16. References

1. Eckert WR, Davis EA. Acute rupture of the peroneal retinaculum. J Bone Joint Surg Am. 1976;58(5):670-672. PMID: 932065

2. Davda K, Malhotra K, O'Donnell P, Singh D, Cullen N. Peroneal tendon disorders. EFORT Open Rev. 2017;2(6):281-292. doi:10.1302/2058-5241.2.160047

3. Hosack T, Perkins O, Bleibleh S, Singh R. Snapping ankles: peroneal tendon subluxation and dislocation. Br J Hosp Med (Lond). 2023;84(10):1-8. doi:10.12968/hmed.2022.0257

4. Saragas NP, Ferrao PN, Mayet Z, Eshraghi H. Peroneal tendon dislocation/subluxation - Case series and review of the literature. Foot Ankle Surg. 2016;22(3):125-130. doi:10.1016/j.fas.2015.06.004

5. Espinosa N, Maurer MA. Peroneal tendon dislocation. Eur J Trauma Emerg Surg. 2015;41(6):623-629. doi:10.1007/s00068-015-0590-0

6. Willegger M, Hirtler L, Schwarz GM, Windhager RH, Chiari C. Peroneal tendon pathologies: From the diagnosis to treatment. Orthopade. 2021;50(7):575-583. doi:10.1007/s00132-021-04116-6

7. Ogawa BK, Thordarson DB. Current concepts review: peroneal tendon subluxation and dislocation. Foot Ankle Int. 2007;28(9):1034-1040. doi:10.3113/FAI.2007.1034

8. Roster B, Michelier P, Giza E. Peroneal Tendon Disorders. Clin Sports Med. 2015;34(4):625-641. doi:10.1016/j.csm.2015.06.003

9. Brodsky JW, Zide JR, Kane JM. Acute Peroneal Injury. Foot Ankle Clin. 2017;22(4):761-774. doi:10.1016/j.fcl.2017.07.004

10. Walt J, Massey P. Peroneal Tendon Syndromes. In: StatPearls. Treasure Island (FL): StatPearls Publishing; 2025. PMID: 31335074

11. Park CH, Gwak HC, Kim JH, et al. Peroneal Tendon Subluxation and Dislocation in Calcaneus Fractures. J Foot Ankle Surg. 2021;60(2):252-257. doi:10.1053/j.jfas.2019.08.030

12. Nishimura A, Fujikawa Y, Senga Y, et al. Recurrent peroneal tendon dislocation-the current concept of management. Ann Jt. 2024;9:40. doi:10.21037/aoj-09-40

13. Lui TH, Tse LF. Peroneal tendoscopy. Foot Ankle Clin. 2015;20(1):27-45. doi:10.1016/j.fcl.2014.10.003

14. Sobotie A, Brown M, Miskovsky S. Peroneal Tendoscopy Technique. Video J Sports Med. 2023;3(4):26350254231176825. doi:10.1177/26350254231176825

15. Hindi HF, Byerly DW. Os Peroneum. In: StatPearls. Treasure Island (FL): StatPearls Publishing; 2025. PMID: 30855913

16. Welck MJ, Zinchenko R, Rudge B. Lisfranc injuries. Injury. 2015;46(4):536-541. doi:10.1016/j.injury.2014.11.026

17. Zell RA, Mehta A. Painful Peroneal Tendon Subluxation in a Patient With a Prior Ankle Fusion. Foot Ankle Spec. 2024;17(4):377-381. doi:10.1177/19386400241251908

18. Porter D, McCarroll J, Knapp E, Torma J. Peroneal tendon subluxation in athletes: fibular groove deepening and retinacular reconstruction. Foot Ankle Int. 2005;26(6):436-441. doi:10.1177/107110070502600604

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17. Related Topics for Further Study

• Lateral Ankle Ligament Injuries - Differentiation and coexisting pathology
• Peroneal Tendon Tears - Longitudinal splits and complete ruptures
• Cavus Foot Deformity - Biomechanical predisposition to peroneal pathology
• Ankle Arthroscopy - Role in diagnosis and treatment of peroneal disorders
• Calcaneal Fractures - High association with peroneal dislocation (13.9%)
• Os Peroneum Syndrome - Painful conditions involving the sesamoid bone within peroneus longus
• Peroneus Quartus - Accessory muscle and its clinical significance
• Chronic Lateral Ankle Instability - Role of peroneals as secondary stabilizers

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