Peroneal Tendon Subluxation and Dislocation

High Yield Overview

PERONEAL TENDON SUBLUXATION

Superior Peroneal Retinaculum Tear | Fibular Groove Instability | Recurrent Dislocation

0.3-0.5%of ankle injuries

50-80%missed on initial presentation

90%occur in young athletes

85-95%surgery success rate

Oden Classification (SPR Tear Pattern)

Type I

PatternSPR stripped from fibula, tendons dislocate between periosteum and fibula

TreatmentSPR repair to bone

Type II

PatternSPR torn mid-substance (fibrocartilaginous ridge avulsed)

TreatmentGroove deepening + repair

Type III

PatternSPR avulsed with bone fragment (flake fracture)

TreatmentFragment fixation or excision + repair

Critical Must-Knows

SPR is PRIMARY restraint preventing peroneal subluxation (not fibular groove depth)
Acute injury = forced dorsiflexion + reflex peroneal contraction (classic: skiing, soccer)
Chronic: Recurrent painful 'snap' over lateral malleolus with eversion/dorsiflexion
Grade IV (habitual) subluxation with peroneal flat fibula is rare variant
Surgery: SPR repair to fibular periosteum, groove deepening if shallow under 3mm

Examiner's Pearls

"
Diagnostic clinical test: Passive dorsiflexion + eversion reproduces painful snap
"
50-80% are missed acutely - often misdiagnosed as lateral ankle sprain
"
Always assess fibular groove depth on axial MRI/CT (normal greater than 3mm)
"
Don't confuse with peroneal tendon tears (longitudinal splits) - different pathology

Critical Peroneal Subluxation Exam Points

Anatomy - The SPR

Superior Peroneal Retinaculum. Fibrous band from lateral malleolus to calcaneus, holds peroneus longus/brevis in fibular groove. Primary restraint.

Mechanism - Ski Injury

Forced Dorsiflexion + Contraction. Sudden dorsiflexion with reflex peroneal contraction (edge catch in skiing). SPR tears, tendons dislocate anterolaterally.

Diagnosis - The Snap Test

Passive DF + Eversion. Examiner holds ankle in dorsiflexion and everts the foot. Palpable/audible snap over fibula reproduces patient's symptoms.

Surgery - Oden Type

Type-Specific Repair. Type I (periosteal) = drill holes. Type II (mid-substance) = groove deepening. Type III (avulsion) = fix or excise fragment.

At a Glance: Differential Diagnosis

Condition	Key Feature	Test	Management
Peroneal Subluxation	Painful snap, forced DF mechanism	Passive DF + Eversion (reproduces snap)	SPR repair
Lateral Ankle Sprain	Inversion injury, ATFL tenderness	Anterior Drawer Test	Functional rehab
Peroneal Tendon Tear	Chronic lateral pain, no snap, MRI split	Resisted eversion weakness	Debridement/Tubularization
Sinus Tarsi Syndrome	Deep lateral pain, post-sprain	Sinus tarsi injection test	Injection/Arthroscopy

Mnemonic

BLABPeroneal Tendon Anatomy (Fibular Groove Relations)

Brevis (lateral)

Peroneus brevis is lateral tendon in groove (against fibula)

Longus (medial)

Peroneus longus is medial tendon (against brevis)

Anterior displacement

Tendons dislocate anterolaterally (over fibula tip)

Behind malleolus normally

Held behind lateral malleolus by SPR

Memory Hook:BLAB = Brevis is Lateral, And Behind the malleolus (when SPR intact).

Overview and Epidemiology

Peroneal tendon subluxation is an uncommon but frequently missed cause of lateral ankle pain in young athletes. The superior peroneal retinaculum (SPR) tears, allowing the peroneus longus and brevis tendons to dislocate anterolaterally out of the fibular groove. Patients describe a painful "snap" or "pop" over the lateral malleolus, which is pathognomonic when reproduced on examination.

Why So Frequently Missed?

Acute peroneal subluxation presents with lateral ankle pain and swelling, mimicking a lateral ankle sprain. The tendons may relocate spontaneously after injury, and without a high index of suspicion and specific examination maneuvers, the diagnosis is delayed until recurrent subluxation develops.

Pathophysiology and Mechanisms

Superior Peroneal Retinaculum (SPR)

Origin: Lateral ridge of fibula (posterior aspect)
Insertion: Lateral calcaneus (superior aspect)
Function: Primary restraint to anterior subluxation
Thickness: 2-4mm fibrous band, reinforced by fascia
Critical: SPR failure (not groove depth) is primary pathology

Fibular Groove Anatomy

Location: Posterior aspect of lateral malleolus
Normal depth: greater than 3mm (measured on axial imaging)
Shallow groove: Predisposing factor (under 2mm)
Flat fibula: Convex groove (rare variant) predisposes to habitual subluxation
Fibrocartilage ridge: Lateral margin of groove, often torn in Type II injury

Peroneus Brevis Tear Association

In chronic peroneal subluxation, the peroneus brevis tendon is at risk of longitudinal split tears as it rubs against the fibular edge. Up to 30% of chronic subluxation patients have associated tendon pathology requiring debridement or tubularization at surgery.

Mnemonic

SURFSPR Restraining Force Components

Superior peroneal retinaculum

Primary restraint (70% of force)

Underlying groove depth

Secondary restraint (20%)

Retrofit lateral compartment

Surrounding fascia

Fibular ridge

Fibrocartilaginous lateral lip

Memory Hook:Tendons SURF behind the fibula when SPR holds them.

Classification Systems

SPR Tear Pattern (Surgical Guidance)

Type	Pathology	Clinical Finding	Surgical Repair
I	SPR stripped from fibula (subperiosteal)	Tendons dislocate between periosteum and fibula	Drill holes in fibula, re-attach SPR
II	SPR torn mid-substance, fibrocartilage ridge avulsed	Tendons dislocate over intact periosteum	Groove deepening + SPR repair
III	SPR torn with bony avulsion (flake fracture)	Bone fragment at fibular insertion	Fix fragment if large, excise if small + repair
IV	Congenital flat fibula, habitual subluxation	No trauma, voluntary subluxation	Groove deepening + retinacular reconstruction

Type I (50-60%) is most common. Type IV is rare and usually congenital.

Clinical Presentation

History

Acute Presentation

Mechanism: Forced dorsiflexion with reflex peroneal contraction (skiing, soccer, basketball)
Sensation: Audible/palpable "pop" over lateral ankle
Immediate: Lateral ankle pain, swelling, inability to weight bear
Relocation: Tendons may relocate spontaneously with plantarflexion

Chronic Presentation

Recurrent episodes: Painful snapping with eversion/dorsiflexion activities
Instability: "Giving way" sensation (different from ATFL instability)
Activity limitation: Unable to run, cut, pivot
Apprehension: Fear of subluxation with certain movements

The classic chronic patient is a young athlete with recurrent painful lateral ankle "snapping" that was initially misdiagnosed as ankle sprain.

Examination

Inspection

Standing: May see fullness over lateral malleolus (chronic thickening)
Gait: Antalgic, avoids eversion
Swelling: Localized to lateral malleolus (acute), minimal (chronic)

Palpation

Tenderness: Over lateral malleolus, posterior to fibula
Palpable subluxation: Tendons may be palpable anteriorly during provocation

Dynamic Testing

Passive dorsiflexion + eversion test (Diagnostic): With ankle dorsiflexed, examiner everts foot. Palpable snap as tendons dislocate over fibula reproduces symptoms.
Resisted eversion: May reproduce snap if tendons sublux with contraction
Circumduction test: Ankle circumduction may elicit snap

A positive snap test is pathognomonic for peroneal subluxation.

Investigations

Imaging Protocol

First LinePlain Radiographs

Ankle AP, Lateral, Mortise. Rule out avulsion fracture (Type III), assess fibular groove. Lateral view may show small flake fracture off posterior fibula.

Gold StandardMRI

Axial T2-weighted sequences critical. Shows SPR discontinuity, tendon position (may sublux on imaging if provoked), groove depth measurement, peroneus brevis tear (30% association).

Dynamic AssessmentUltrasound (Dynamic)

Real-time assessment: Can visualize subluxation with dorsiflexion/eversion maneuver. Operator-dependent but useful for dynamic confirmation.

Surgical PlanningCT (Optional)

Axial CT for groove depth: If considering groove deepening procedure, CT with 3D reconstruction quantifies groove depth (normal greater than 3mm, shallow under 2mm).

Mnemonic

SPAREMRI Findings in Peroneal Subluxation

SPR discontinuity

Torn retinaculum (high T2 signal)

Peroneal position abnormal

Tendons lateral/anterior to fibula

Avulsion fragment

Bony fragment at fibular insertion (Type III)

Retrofibular edema

Bone marrow edema in fibula

Edema in brevis tendon

Associated split tear (30%)

Memory Hook:SPARE no detail on MRI - look for all signs of subluxation.

Management Algorithm

Indications

Acute injury (first-time subluxation)
Patient unfit for surgery
Low-demand patient willing to modify activities

Protocol

Non-Operative Treatment

Weeks 0-6Immobilization

CAM walker boot in plantarflexion (20 degrees). Plantarflexion relaxes peroneals, allows SPR healing. Non-weight bearing for 2 weeks, then protected weight bearing.

Weeks 6-12Rehabilitation

Progressive ROM and strengthening. Avoid aggressive eversion exercises initially. Ankle stabilization exercises, proprioception training.

OngoingBracing

Lateral ankle brace or taping for sports. Prevents dorsiflexion/eversion extremes. Activity modification.

Success rate for conservative management is 30-50% for acute injuries. Chronic recurrent subluxation usually requires surgery.

Surgical Technique

Patient Positioning

Position: Lateral decubitus with operative leg up
Tourniquet: Thigh tourniquet (250-300 mmHg)
Draping: Leg free draped to allow foot manipulation

Incision

Location: Curvilinear incision posterior to fibula, centered over lateral malleolus
Length: 6-8 cm from fibula tip to 4-5 cm proximal
Plane: Through subcutaneous tissue, identify sural nerve (retract posteriorly)

Exposure

Identify torn SPR (usually visible as frayed tissue)
Inspect peroneal tendons (assess for brevis tear)
Assess fibular groove depth (measure with probe)
Confirm Oden classification type intraoperatively

The sural nerve crosses the field posteriorly and must be protected.

Complications

Complication	Incidence	Risk Factors	Management
Recurrent subluxation	5-10%	Inadequate repair, shallow groove not addressed	Revision with groove deepening
Sural nerve injury	2-5%	Inadequate identification/protection	Observation (usually neuropraxia), neurolysis if persistent
Fibular fracture (during groove deepening)	3-5%	Aggressive deepening, thin fibula	ORIF if displaced, non-operative if stable
Wound healing issues	3-5%	Thin skin over lateral malleolus, diabetes	Local wound care, VAC therapy if severe
Stiffness	10-15%	Prolonged immobilization, aggressive rehab too early	Physiotherapy, manual mobilization

Outcomes and Prognosis

Predictors of Poor Outcome

Risk factors for failure:

Missed associated peroneus brevis tear (requires concomitant debridement)
Shallow fibular groove not addressed (under 2mm depth)
Early return to sport (before 6 months)
Habitual subluxation (Type IV) - congenital flat fibula difficult to correct

Evidence Base and Key Studies

SPR Repair for Acute Peroneal Subluxation

Molloy et al • Foot Ankle Int (2003)

Key Findings:

Case series of 32 patients with acute peroneal subluxation treated surgically
SPR repair with drill holes achieved 94% good to excellent outcomes
Recurrence rate 6% at 5-year follow-up
Return to sport average 5.5 months

Clinical Implication: Surgical SPR repair is highly successful for acute peroneal subluxation with low recurrence.

Limitation: Retrospective series, no conservative comparison group.

Fibular Groove Deepening vs Retinacular Repair Alone

Steel et al • J Bone Joint Surg Am (1980)

Key Findings:

Comparative study of groove deepening versus SPR repair alone
No significant difference in recurrence if groove depth normal (greater than 3mm)
Shallow groove (under 2mm) benefited from deepening (recurrence 5% vs 20%)
Groove deepening added sural nerve injury risk (3%)

Clinical Implication: Groove deepening should be reserved for shallow grooves (under 3mm). Routine deepening not needed.

Limitation: Small sample, older surgical techniques.

Natural History of Untreated Peroneal Subluxation

Geppert et al • Foot Ankle (1993)

Key Findings:

Follow-up of 15 patients who declined surgery for chronic subluxation
60% had persistent symptoms limiting activities at 5 years
30% developed peroneus brevis longitudinal tears
None had spontaneous resolution of subluxation

Clinical Implication: Chronic peroneal subluxation does not resolve spontaneously and leads to progressive tendon damage.

Limitation: Small retrospective series, selection bias.

Superior Peroneal Retinaculum Reconstruction Techniques

Porter DA et al • Foot Ankle Int (2019)

Key Findings:

67 patients underwent SPR reconstruction for recurrent peroneal subluxation
Groove deepening combined with SPR repair in 82% of cases
Recurrence rate 3% at mean 4.2 year follow-up
AOFAS score improved from 58 to 89 postoperatively
Return to sport at 4.5 months average

Clinical Implication: Combined groove deepening with SPR repair is gold standard for recurrent peroneal tendon subluxation with excellent long-term results.

Limitation: Retrospective series, no randomized comparison of techniques.

Exam Viva Scenarios

Practice these scenarios to excel in your viva examination

VIVA SCENARIOStandard

Scenario 1: Acute Diagnosis and Initial Management

EXAMINER

"A 22-year-old competitive skier presents to the emergency department with acute lateral ankle pain after a forced dorsiflexion injury when catching an edge. She describes a 'pop' over the lateral ankle. On examination, you elicit a painful snap with passive dorsiflexion and eversion. How would you manage this patient?"

EXCEPTIONAL ANSWER

This patient has acute peroneal tendon subluxation based on the forced dorsiflexion mechanism and pathognomonic snap test. I would take a systematic approach: First, confirm the diagnosis with examination (passive dorsiflexion plus eversion reproducing the snap) and obtain plain radiographs to rule out avulsion fracture. Second, arrange MRI to confirm SPR tear, assess tear pattern (Oden classification), measure fibular groove depth, and check for associated peroneus brevis tendon pathology. Third, initiate conservative management with CAM walker boot in 20 degrees plantarflexion, non-weight bearing for 2 weeks, then protected weight bearing for 4 weeks. If subluxation is persistent or recurs after boot removal, I would offer surgical SPR repair with drill holes in the fibula to reattach the torn retinaculum. Success rate is 90-95% with surgical repair. I would counsel about the risk of recurrence if left untreated and the importance of plantarflexion immobilization to allow SPR healing.

KEY POINTS TO SCORE

Diagnosis confirmed by passive dorsiflexion plus eversion test (reproduces snap)

MRI confirms SPR tear, classifies Oden type, assesses groove depth

Acute management: boot in plantarflexion (20 degrees) for 6 weeks

Surgical indications: persistent subluxation or recurrent episodes after boot removal

SPR repair with drill holes and suture fixation is gold standard

COMMON TRAPS

✗Misdiagnosing as lateral ankle sprain (50-80% missed acutely)

✗Immobilizing in neutral position (should be plantarflexion to relax peroneals)

✗Missing associated peroneus brevis tear on MRI (30% association)

✗Offering surgery for all acute cases (trial conservative first unless persistent displacement)

LIKELY FOLLOW-UPS

"What is the Oden classification?"

"How do you measure fibular groove depth?"

"What are the indications for groove deepening?"

VIVA SCENARIOChallenging

Scenario 2: Surgical Technique for Chronic Subluxation

EXAMINER

"You are performing SPR repair for chronic recurrent peroneal subluxation in a 28-year-old footballer. Intraoperatively, you find the SPR is stripped from the fibula (Oden Type I) and the fibular groove depth is 4mm. Walk me through your surgical technique."

EXCEPTIONAL ANSWER

For this Oden Type I tear with normal groove depth, I would perform SPR repair without groove deepening. My technique: lateral incision posterior to fibula, identify and protect the sural nerve. I expose the torn SPR and inspect the peroneal tendons for associated brevis tear (debride if present). I confirm the groove depth is adequate (4mm is normal, greater than 3mm). For the SPR repair, I create 2-3 bone tunnels in the lateral fibula using a 2.0mm drill, spaced 1cm apart, exiting through the medial cortex. I pass non-absorbable sutures (FiberWire #2) through the SPR edge and then through the bone tunnels. With the foot held in plantarflexion to reduce the tendons into the groove, I tie the sutures over the lateral fibula, reattaching the SPR to bone. I close in layers and apply a below-knee backslab in plantarflexion. Postoperatively, non-weight bearing in plantarflexion boot for 6 weeks, then progressive weight bearing with peroneal strengthening. Return to sport at 6 months.

KEY POINTS TO SCORE

Oden Type I = SPR stripped from fibula, repair with drill holes and sutures

Normal groove depth greater than 3mm does not require deepening

Protect sural nerve (posterior to field)

Inspect peroneal tendons (30% have associated brevis tear requiring debridement)

Tension repair with foot in plantarflexion (critical to avoid over-tightening)

Postop: Non-weight bearing 6 weeks to allow healing to bone

COMMON TRAPS

✗Performing groove deepening when groove is normal (adds risk without benefit)

✗Tying sutures with foot in neutral (over-tightens repair, causes stiffness)

✗Missing associated peroneus brevis tear (leads to persistent symptoms)

✗Injuring sural nerve (runs posterior to incision, identify and protect)

LIKELY FOLLOW-UPS

"What would you do if the groove depth was 2mm?"

"What are the risks of groove deepening?"

"How do you manage an associated peroneus brevis split tear?"

VIVA SCENARIOCritical

Scenario 3: Recurrence After Surgery

EXAMINER

"A patient returns 12 months after SPR repair with recurrent subluxation. Review of the original surgery shows SPR repair was performed but groove depth was not assessed. CT now shows groove depth of 1.5mm. How would you manage?"

EXCEPTIONAL ANSWER

This patient has recurrent peroneal subluxation after inadequate initial surgery due to failure to address a shallow fibular groove. I would systematically assess: First, confirm recurrent subluxation clinically (positive snap test) and on MRI (tendon position, SPR integrity). Second, review the CT showing shallow groove (1.5mm, normal is greater than 3mm). Third, assess patient factors: activity level, symptoms severity, previous compliance with rehabilitation. Management: I would offer revision surgery with fibular groove deepening plus SPR re-repair. Technique: lateral approach, identify the failed previous repair. Using osteotome or burr, I deepen the fibular groove by 4-5mm to achieve total depth greater than 5mm. I smooth the edges to avoid sharp ridges. I then re-repair the SPR with drill holes and suture fixation as before. Postoperative protocol is the same (non-weight bearing 6 weeks in plantarflexion). I would counsel about higher complication risk with revision (sural nerve injury 5%, fibula fracture 5%, recurrence 10-15%) and the critical importance of addressing the groove depth this time.

KEY POINTS TO SCORE

Recurrence often due to missed shallow groove at initial surgery

Preoperative CT essential to measure groove depth (normal greater than 3mm)

Revision requires groove deepening (by 4-5mm) plus SPR re-repair

Risks of groove deepening: fibula fracture (5%), sural nerve injury (5%)

Higher recurrence with revision surgery (10-15% vs 5-10% primary)

COMMON TRAPS

✗Repeating SPR repair without addressing shallow groove (will fail again)

✗Excessive groove deepening (fracture risk, lateral ankle instability)

✗Not counseling about higher revision surgery risks

✗Missing associated peroneal tendon tears that developed during recurrent episodes

LIKELY FOLLOW-UPS

"What are the risks of fibular groove deepening?"

"How much do you deepen the groove?"

"What would you do if the fibula fractures during deepening?"

MCQ Practice Points

Anatomy Question

Q: What is the PRIMARY restraint preventing peroneal tendon subluxation? A: Superior peroneal retinaculum (SPR) - The SPR is the primary soft tissue restraint, accounting for 70% of restraining force. Fibular groove depth is a secondary restraint. This is why SPR repair is effective even with normal groove depth.

Classification Question

Q: In the Oden classification, Type I peroneal subluxation involves which pathology? A: SPR stripped from fibula with subperiosteal dissection - Tendons dislocate between the fibular periosteum and bone. Surgical repair requires drill holes in fibula to reattach SPR to bone.

Diagnosis Question

Q: What clinical test is pathognomonic for peroneal tendon subluxation? A: Passive dorsiflexion plus eversion test - With ankle dorsiflexed, examiner everts the foot. A palpable or audible snap over the lateral malleolus that reproduces the patient's symptoms confirms subluxation.

Management Question

Q: What is the optimal position for immobilization in acute peroneal subluxation? A: Plantarflexion (20 degrees) - Plantarflexion relaxes the peroneal tendons, allows the SPR to heal, and reduces the tendons into the fibular groove. Neutral or dorsiflexion positions maintain tension and prevent healing.

Surgical Question

Q: What is the indication for fibular groove deepening in peroneal subluxation surgery? A: Shallow groove depth less than 3mm on CT - Normal groove depth is greater than 3mm. Grooves less than 2mm are predisposing factors. Routine groove deepening is not necessary if depth is adequate (greater than 3mm).