Medial Ankle Instability
Comprehensive overview of the topic.
Exam Warning
High-yield exam focus: Understanding deltoid anatomy (superficial vs deep components), recognizing associated injuries (syndesmosis, PTTD, fractures), differentiating medial gutter pain from true instability, identifying when surgical intervention is required, and managing concomitant pathology. Examiners expect discussion of why isolated deltoid injury is rare and what forces/injuries cause deltoid disruption.
Anatomy and Biomechanics
Deltoid Ligament Complex
The deltoid ligament is the primary medial ankle stabilizer, consisting of superficial and deep layers with distinct anatomic and functional characteristics.
Superficial Deltoid Layer
Components: Tibionavicular, tibiocalcaneal (superficial), tibiospring ligaments Origin: Anterior colliculus of medial malleolus Insertion: Navicular tuberosity, sustentaculum tali, spring ligament Orientation: Fan-shaped, broad insertion Primary function: Restraint to hindfoot valgus, secondary restraint to external rotation Clinical note: More commonly injured in isolation, better healing potential Blood supply: Medial tarsal artery branches
Deep Deltoid Layer
Components: Anterior tibiotalar, posterior tibiotalar, tibiocalcaneal (deep) Origin: Intercollicular groove and posterior colliculus of medial malleolus Insertion: Medial talus (tubercle), medial calcaneal wall Orientation: Thick, cord-like bands Primary function: Critical restraint to external rotation and lateral talar shift Clinical significance: Deep component injury indicates severe force, often associated with syndesmotic disruption Strongest component: Posterior tibiotalar (deep) is strongest and most critical for stability
Spring Ligament Complex
Components: Superomedial, medioplantar oblique, inferoplantar longitudinal bands Connection: Intimately associated with superficial deltoid (tibiospring fibers) Function: Supports talar head, maintains medial longitudinal arch Dual pathology: Spring ligament injury often accompanies deltoid insufficiency Clinical presentation: Combined injury leads to valgus hindfoot and flatfoot deformity Surgical consideration: Both may require reconstruction in chronic cases
Biomechanical Function
At a Glance
Medial ankle instability from deltoid ligament insufficiency represents only 3-5% of ankle sprains due to the ligament's significant strength (2-3x ATFL). The deltoid has superficial (hindfoot valgus restraint) and deep (external rotation and lateral talar shift restraint) components. Isolated deltoid injury is rare; most occur with syndesmotic injuries (40-60%), pronation-external rotation fractures, or stage 4 PTTD. Diagnosis requires stress radiographs showing medial clear space widening greater than 4mm or MRI demonstrating ligament discontinuity. Conservative management succeeds in 60-70%; surgical reconstruction is indicated for persistent symptomatic instability.
Memory Hook:EVEL Deltoid
The deltoid ligament resists 40% of valgus stress and is primary restraint to external rotation of the talus within the mortise. The deep posterior tibiotalar ligament prevents lateral translation of the talus, maintaining medial clear space (normal less than 4mm). Deltoid competency is essential for syndesmotic stability; deltoid insufficiency allows widening of ankle mortise even with intact syndesmosis.
Pathophysiology and Injury Mechanisms
Injury Patterns and Associated Pathology
Isolated deltoid ligament injury is rare due to the ligament's substantial strength (2-3 times stronger than ATFL). Most deltoid injuries occur as part of more complex injury patterns.
Deltoid Injury Patterns and Mechanisms
| feature | mechanism | associatedInjuries | incidence | treatment | prognosis |
|---|---|---|---|---|---|
| Isolated Deltoid Sprain | Direct valgus force with external rotation (rare) | Usually none, occasionally spring ligament injury | Less than 5% of deltoid injuries | Conservative management, immobilization 4-6 weeks | Good, 70-80% resolution with conservative care |
| Deltoid with Syndesmosis Injury | Pronation-external rotation force | AITFL disruption (40-60%), IOL injury, fibular fracture | Most common pattern (40-60% of deltoid injuries) | Syndesmotic fixation priority, deltoid may require repair | Dependent on syndesmosis treatment, deltoid usually heals |
| Pronation-Abduction Fractures | Valgus force with abduction, oblique medial malleolus fracture | Medial malleolus fracture, lateral ligament injury or fibula fracture | 20-30% of deltoid pathology presentations | ORIF medial malleolus, deltoid repair if tissue quality poor | Good with anatomic fracture reduction |
| Stage 4 PTTD | Chronic progressive valgus deformity and arch collapse | PTT rupture, spring ligament attenuation, subtalar arthritis | 10-15% of deltoid presentations | Reconstruction vs fusion based on arthritis presence | Complex, depends on deformity correction and arthritic changes |
Clinical Imaging
Imaging Gallery
Acute vs Chronic Deltoid Insufficiency
Acute deltoid injuries typically result from high-energy trauma with forced valgus and external rotation. Clinical presentation includes significant medial ankle swelling, ecchymosis extending to hindfoot, inability to weight-bear, and positive external rotation stress test. MRI demonstrates ligament discontinuity with surrounding edema. Treatment prioritizes identifying and addressing associated injuries, particularly syndesmotic disruption.
Chronic deltoid insufficiency develops from untreated acute injury, repetitive microtrauma in athletes (gymnastics, soccer), or progressive deformity in PTTD. Presents with medial ankle pain, subjective instability, and valgus hindfoot alignment. MRI shows ligament thickening, scarring, or complete attenuation. May have widened medial clear space on weight-bearing radiographs. Treatment requires addressing underlying biomechanical abnormalities.
Clinical Evaluation
History and Physical Examination
Patient history should elicit mechanism of injury (valgus force, external rotation), previous ankle injuries or instability, and functional limitations. Pain with cutting or pivoting activities suggests rotational instability. History of flatfoot or PTTD relevant for chronic cases.
Memory Hook:STAMP
Inspection reveals medial ankle swelling in acute injuries or valgus hindfoot deformity in chronic cases. Observe for pes planus deformity suggesting concurrent PTTD or spring ligament insufficiency. Check for antalgic gait or inability to perform single heel raise.
Palpation should systematically assess medial malleolus, deltoid ligament course (from anterior colliculus inferiorly), spring ligament (plantar-medial to navicular), and PTT course. Tenderness localizes injury and identifies associated pathology.
Special Tests:
- External rotation stress test: With knee flexed 90 degrees and ankle in neutral, apply external rotation force to foot. Pain and increased rotation compared to contralateral side indicates deltoid injury
- Valgus stress test: Apply valgus force to hindfoot with ankle in neutral. Increased medial joint opening suggests deltoid insufficiency
- Kleiger test: External rotation of foot with ankle dorsiflexed and tibia stabilized. Pain at medial ankle indicates deltoid injury; pain at syndesmosis suggests combined pathology
- Single heel raise test: Inability to perform or lack of hindfoot inversion during raise indicates PTT dysfunction or severe deltoid insufficiency
Imaging Protocol
Radiographs (Weight-Bearing)
Views required: AP, lateral, mortise of ankle; AP and lateral foot Key measurements: Medial clear space (normal less than 4mm), talonavicular coverage angle, lateral talar station Stress views: External rotation stress radiograph may demonstrate medial clear space widening Fracture assessment: Medial malleolus, fibula, posterior malleolus Chronic findings: Valgus tilt, talar subluxation, arthritic changes
MRI Imaging
Indications: Suspected deltoid injury, chronic instability, pre-operative planning Protocol: T1, T2, STIR sequences in coronal, sagittal, and axial planes Deltoid assessment: Grade 1 (intact fibers with edema), Grade 2 (partial tear), Grade 3 (complete disruption) Associated pathology: Syndesmosis, spring ligament, PTT, osteochondral lesions, bone bruising Chronic changes: Ligament thickening, scarring, attenuation without discrete tear
CT Scanning
Indications: Fracture characterization, pre-operative planning, arthritic assessment Advantages: Superior bony detail, assessment of subtalar joint Weight-bearing CT: Emerging technology for dynamic assessment of hindfoot alignment 3D reconstruction: Helpful for complex fracture patterns Limitations: Poor soft tissue resolution, radiation exposure
Exam Pearl
Medial clear space measurement on mortise radiograph is critical diagnostic parameter. Normal is less than 4mm and should equal superior clear space. Widening greater than 4mm or asymmetry compared to contralateral ankle indicates deltoid insufficiency or syndesmotic injury. Weight-bearing radiographs essential for accurate assessment.
Conservative Management
Treatment Protocol for Acute Injuries
Non-operative management is first-line treatment for isolated deltoid sprains without fracture or syndesmotic injury, successful in 60-70% of cases.
Phase 1 (0-3 weeks): Protection and Immobilization
- CAM boot or short leg cast, non-weight-bearing for grade 2-3 injuries
- Protected weight-bearing for grade 1 injuries after first week
- Ice, elevation, compression for edema control
- NSAIDs for pain management (if no contraindications)
Phase 2 (3-6 weeks): Progressive Weight-Bearing
- Transition to weight-bearing as tolerated in CAM boot
- Begin gentle ankle range of motion exercises (avoid forced eversion)
- Initiate isometric strengthening (tibialis posterior, gastrocnemius)
- Continue until pain-free with daily activities
Phase 3 (6-12 weeks): Strengthening and Return to Activity
- Progress to lace-up ankle brace or taping
- Progressive resistance exercises focusing on tibialis posterior and invertor muscles
- Proprioceptive training (single leg balance, wobble board)
- Sport-specific training with gradual progression
- May require 3-4 months for return to high-level athletics
Critical assessment for syndesmotic injury required in all deltoid injuries. Failure to identify and treat concurrent syndesmosis disruption leads to chronic pain, instability, and post-traumatic arthritis. Perform syndesmotic squeeze test, external rotation stress test, and consider MRI if clinical suspicion despite negative radiographs.
Indications for Surgical Intervention
Conservative management fails in 30-40% of cases, requiring surgical consideration. Indications for surgery include:
Absolute indications:
- Acute deltoid disruption with syndesmotic instability requiring fixation
- Deltoid disruption with widened medial clear space (greater than 4mm) despite syndesmotic fixation
- Chronic symptomatic instability with functional limitation despite 4-6 months therapy
- Stage 4 PTTD with deltoid insufficiency and progressive deformity
Relative indications:
- High-demand athletes with persistent symptoms after 3 months conservative care
- Deltoid injury associated with medial malleolus fracture with comminution preventing stable fixation
- MRI-confirmed complete deltoid rupture with poor tissue quality in acute setting
Surgical Management
Direct Deltoid Ligament Repair
Primary repair of acute deltoid injuries is performed when good tissue quality exists and injury is part of operative ankle fracture or syndesmotic fixation.
Patient Positioning: Supine, bump under ipsilateral hip, thigh tourniquet, foot over end of table or on folded towel for access to medial ankle.
Incision: Curvilinear incision centered over medial malleolus, extending from just proximal to tip distally along deltoid course (6-7cm length). Alternative: use medial malleolar fracture fixation incision if present.
Approach: Full-thickness skin flaps to expose medial malleolus, deltoid ligament, and tibialis posterior tendon. Identify and protect saphenous vein and nerve (anterior to incision). Great saphenous nerve at risk with anterior extension.
Deltoid Assessment:
- Identify level of disruption (most commonly at tibial origin or midsubstance)
- Differentiate superficial from deep components
- Assess tissue quality for primary repair vs augmentation requirement
- Inspect for associated injuries (spring ligament, PTT, medial talar osteochondral lesion)
Repair Technique:
- Debride devitalized tissue conservatively
- Place suture anchors (3.0-3.5mm) at anatomic deltoid origin on medial malleolus
- Anterior colliculus for superficial layer
- Intercollicular groove for deep components
- Use high-strength sutures (2-0 or 0 nonabsorbable)
- Repair deep layer first (critical for rotational stability)
- Superficial layer repaired separately with slight overlap
- Ankle positioned in neutral dorsiflexion and 5 degrees hindfoot inversion during tie-down
- Consider suture augmentation with internal brace for high-demand athletes
Spring Ligament Assessment: If spring ligament injury identified (palpable defect plantar-medial to navicular, talar head uncoverage on radiograph), address concurrently with suture anchor repair or reconstruction.
Closure: Deep layer with absorbable suture, skin with nonabsorbable suture or staples. Well-padded posterior splint with ankle in neutral position, hindfoot slight inversion.
Exam Pearl
Ankle positioning during deltoid repair is critical: neutral dorsiflexion and 5 degrees hindfoot inversion (not eversion or valgus). This prevents overtightening causing stiffness while ensuring adequate tension for stability. Compare to contralateral ankle for appropriate positioning.
Postoperative Management
Rehabilitation Protocol
Phase 1: Protection (0-2 weeks)
Immobilization: Posterior splint or CAM boot, strict non-weight-bearing Activity: Toe wiggling, ankle pumps (plantarflexion/dorsiflexion only) Precautions: No eversion, no forced dorsiflexion Wound care: Suture removal 10-14 days, monitor for infection Pain control: Multimodal analgesia, ice, elevation
Phase 2: Early Motion (2-6 weeks)
Weight-bearing: Progress from non-weight-bearing to 50% by week 6 Immobilization: CAM boot with gradual increase in time out for exercises ROM exercises: Active ankle pumps, gentle inversion-eversion (no forced eversion) Strengthening: Isometric tibialis posterior, gastrocnemius contractions PT initiation: Week 3-4 for edema control and supervised ROM
Phase 3: Strengthening (6-12 weeks)
Weight-bearing: Progress to full weight-bearing in boot, then transition to brace Immobilization: Lace-up ankle brace or Arizona brace for support Strengthening: Progressive resistance with theraband, focus on tibialis posterior Proprioception: Single leg balance, wobble board exercises Functional activities: Pool walking, stationary bike, elliptical Return to work: Sedentary 8-10 weeks, manual labor 12-14 weeks
Phase 4: Return to Sport (3-6 months)
Criteria: Full strength, normal ROM, negative stress tests, functional testing passed Progression: Walk-jog program, straight-line running, cutting drills, sport-specific Bracing: External ankle brace recommended for sports for 12 months Success rate: 80-90% return to pre-injury activity level Long-term: Permanent brace may be needed for high-level athletics
Memory Hook:PIER Deltoid Recovery
Complications
Early Complications
Wound healing problems occur in 5-8% due to thin soft tissue envelope over medial malleolus. Risk factors include diabetes, smoking, peripheral vascular disease, and steroid use. Prevention requires careful handling of skin flaps, avoiding excessive tension on closure, and appropriate patient selection. Management ranges from local wound care to debridement and delayed closure for deeper dehiscence.
Saphenous nerve injury presents as numbness or dysesthesia along medial ankle and foot (10-15% incidence). Usually iatrogenic from surgical dissection or retractor placement. Majority are neurapraxia resolving within 3-6 months. Permanent injury occurs in less than 2% but can be debilitating. Prevention requires identification and protection of nerve during approach.
Posterior tibial neurovascular injury is rare (less than 1%) but catastrophic. Bundle lies approximately 1.5cm posterior to medial malleolus. At risk during deep dissection for deltoid reconstruction or bone tunnel creation. Presents with numbness on plantar foot, weakness of toe flexion, or vascular compromise. Prevention through careful dissection and knowledge of anatomy.
Late Complications
Stiffness and loss of motion affects 15-20% of patients following deltoid reconstruction, higher than lateral ligament procedures. Typically involves loss of dorsiflexion (average 8-12 degrees) and subtalar motion. Caused by immobilization duration, adhesion formation, or overtightening during repair. Prevention includes early motion protocols (after 2 weeks protection) and avoiding excessive tension during reconstruction. Treatment with aggressive physical therapy, occasionally manipulation under anesthesia.
Persistent instability occurs in 10-15% following reconstruction. Causes include technical failure (inadequate graft tension, tunnel malposition), unaddressed hindfoot valgus deformity, progression of PTTD, or syndesmotic insufficiency. Requires thorough re-evaluation with imaging to identify specific failure mechanism. Management may require revision reconstruction, calcaneal osteotomy, or salvage fusion procedures.
Post-traumatic arthritis develops in 20-30% of patients with deltoid injuries associated with ankle fractures or syndesmotic disruption. Risk factors include initial fracture displacement, quality of fracture reduction, articular cartilage damage, and age greater than 50 years. Presents with progressive pain and stiffness over 2-5 years. Treatment ranges from conservative measures (bracing, activity modification, injections) to ankle arthroplasty or arthrodesis in severe cases.
Evidence Base
Deltoid Repair in Ankle Fractures with Syndesmotic Injury
Deltoid Reconstruction for Chronic Instability Outcomes
Natural History of Conservatively Treated Deltoid Sprains
Internal Brace Augmentation of Deltoid Repair
Viva Scenarios
Viva Overview Summary
Key Points for Viva
Epidemiology:
- 3-5% of ankle sprains (much less common than lateral)
- Deltoid is 2-3x stronger than ATFL
- Isolated injury is rare
Key Associations:
- Syndesmotic injury (40-60% of deltoid injuries)
- Pronation-external rotation ankle fractures
- Stage 4 PTTD with flatfoot
Quick Reference
| Feature | Key Point |
|---|---|
| Incidence | 3-5% of ankle sprains |
| Most common pattern | Deltoid + syndesmosis (40-60%) |
| Conservative success | 60-70% |
Deltoid Anatomy Summary
Two-Layer Structure
Superficial Layer:
- Tibionavicular, tibiocalcaneal, tibiospring
- Origin: Anterior colliculus
- Function: Restraint to hindfoot valgus
Deep Layer:
- Anterior and posterior tibiotalar
- Origin: Intercollicular groove
- Function: Restraint to external rotation and lateral talar shift
Deltoid Components
| Layer | Components | Function |
|---|---|---|
| Superficial | Tibionavicular, tibiocalcaneal, tibiospring | Hindfoot valgus restraint |
| Deep | Anterior/posterior tibiotalar | External rotation, lateral shift |
Injury Classification
Classification by Pattern
By Mechanism:
- Isolated deltoid (less than 5%): Direct valgus force
- With syndesmosis (40-60%): Pronation-external rotation
- With fracture (20-30%): Pronation-abduction
- Stage 4 PTTD (10-15%): Chronic progressive
By Severity:
- Grade 1: Intact fibers with edema
- Grade 2: Partial tear
- Grade 3: Complete disruption
Injury Pattern Classification
| Pattern | Incidence | Prognosis |
|---|---|---|
| Isolated | Less than 5% | Good (70-80% conservative) |
| With syndesmosis | 40-60% | Depends on syndesmosis treatment |
| Stage 4 PTTD | 10-15% | Complex, multi-procedure needed |
Clinical Examination Summary
Key Clinical Tests
External Rotation Stress Test:
- Knee flexed 90°, ankle neutral
- Externally rotate foot
- Pain and increased rotation = positive
Valgus Stress Test:
- Apply valgus force to hindfoot
- Compare to contralateral side
- Increased opening = deltoid insufficiency
Single Heel Raise:
- Tests PTT function
- Inability or lack of inversion = dysfunction
Clinical Tests
| Test | What It Tests | Positive Finding |
|---|---|---|
| External rotation | Deep deltoid | Pain, increased rotation |
| Valgus stress | Both layers | Increased medial opening |
| Single heel raise | PTT function | Unable or no inversion |
Viva Imaging Review
Key Imaging Findings
Radiographs (Weight-Bearing):
- Medial clear space: Normal less than 4mm
- Greater than 4mm = deltoid insufficiency
- Must compare to contralateral
MRI Grading:
- Grade 1: Intact fibers with edema
- Grade 2: Partial tear (some fibers intact)
- Grade 3: Complete disruption
Associated Findings:
- Syndesmosis injury
- Spring ligament attenuation
- Osteochondral lesions
Imaging Findings
| Modality | Key Finding | Significance |
|---|---|---|
| X-ray | Medial clear space greater than 4mm | Deltoid/syndesmosis injury |
| MRI | Grade 3 disruption | Complete tear, may need surgery |
| Stress views | Widening with stress | Confirms instability |
Viva Treatment Review
Management Approach
Conservative (First-Line):
- CAM boot/cast 4-6 weeks
- Progressive weight-bearing
- Strengthening and proprioception
- Success rate: 60-70%
Surgical Indications:
- Deltoid + syndesmosis requiring fixation
- Widened MCS despite syndesmosis reduction
- Chronic instability failed 4-6 months therapy
- Stage 4 PTTD
Treatment Decision
| Scenario | Treatment | Expected Outcome |
|---|---|---|
| Isolated Grade 1-2 | Conservative | 70-80% success |
| With syndesmosis | Fix syndesmosis, assess MCS | MCS may normalise |
| Chronic instability | Reconstruction | 75-85% success |
Surgical Technique Essentials
Operative Approach
Primary Repair (Acute):
- Medial incision over malleolus
- Protect saphenous nerve (anterior)
- Suture anchors at anatomic origins
- Repair deep layer first
Reconstruction (Chronic):
- Autograft (hamstring) preferred
- Bone tunnels in malleolus
- Anatomic recreation of superficial and deep
Key Position:
- Neutral dorsiflexion
- 5° hindfoot inversion (NOT valgus)
Surgical Options
| Type | Indication | Technique |
|---|---|---|
| Primary repair | Acute, good tissue | Suture anchors to malleolus |
| Reconstruction | Chronic, poor tissue | Autograft through tunnels |
Complications Overview
Complication Summary
Early:
- Wound healing (5-8%)
- Saphenous nerve injury (10-15%, mostly neurapraxia)
- PTN injury (less than 1%)
Late:
- Stiffness (15-20%)
- Persistent instability (10-15%)
- Post-traumatic arthritis (20-30% with fractures)
Complication Rates
| Complication | Incidence | Outcome |
|---|---|---|
| Saphenous nerve | 10-15% | Most resolve 3-6 months |
| Stiffness | 15-20% | May need PT or MUA |
| Recurrent instability | 10-15% | May need revision |
Rehabilitation Summary
Post-Op Protocol
Phase 1 (0-2 weeks): NWB, splint, wound care Phase 2 (2-6 weeks): Progress to 50% WB, gentle ROM Phase 3 (6-12 weeks): Full WB, strengthening, proprioception Phase 4 (3-6 months): Return to sport with brace
Rehabilitation Timeline
| Phase | Weight-Bearing | Activity |
|---|---|---|
| 0-2 weeks | Non-weight-bearing | Splint protection |
| 2-6 weeks | Progress to 50% | Gentle ROM in boot |
| 6-12 weeks | Full weight-bearing | Strengthening, proprioception |
| 3-6 months | Sport-specific | Return to play with brace |
Outcomes Summary
Expected Results
Conservative Treatment:
- 60-70% success for isolated injuries
- 14-week average return to sport
- Higher failure with Grade 3 tears
Surgical Treatment:
- Primary repair: 85-90% success
- Reconstruction: 75-85% success
- Combined with PTTD: 70-80% success
Outcome Rates
| Treatment | Success Rate | Notes |
|---|---|---|
| Conservative | 60-70% | Isolated injuries only |
| Primary repair | 85-90% | Acute, good tissue |
| Reconstruction | 75-85% | Chronic insufficiency |
Evidence Summary
Key Evidence
Yu et al (JBJS 2016):
- Deltoid repair may accelerate recovery
- Faster return to weight-bearing (6.2 vs 8.1 weeks)
- No difference long-term
Hintermann et al (FAI 2018):
- Anatomic reconstruction: 81% good-excellent
- 14% recurrent instability
- Better for isolated than combined PTTD
Hiller et al (AJSM 2015):
- 68% conservative success
- 8% required reconstruction
- Grade 3 and spring ligament injury = higher failure
Evidence Summary
| Study | Key Finding | Level |
|---|---|---|
| Yu 2016 | Deltoid repair accelerates recovery | Level 2 |
| Hintermann 2018 | 81% good-excellent outcomes | Level 3 |
| Hiller 2015 | 68% conservative success | Level 2 |
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
Acute Deltoid Injury with Syndesmotic Disruption
"A 32-year-old rugby player sustained an ankle injury during a tackle. Radiographs show a Weber B fibular fracture and widened medial clear space (6mm). Tibiofibular clear space is 7mm. MRI confirms complete deltoid disruption and syndesmotic injury. How would you manage this patient?"
Chronic Medial Ankle Instability in Stage 4 PTTD
"A 58-year-old female presents with progressive flatfoot deformity and medial ankle pain over 5 years. She has valgus hindfoot, forefoot abduction, and failed conservative management including orthotics and bracing. Weight-bearing radiographs show valgus tilt of talus with medial clear space widening to 6mm. MRI shows complete PTT rupture, spring ligament attenuation, and deltoid insufficiency. No ankle arthritis present. What is your treatment approach?"
Exam Day Cheat Sheet
MCQ Practice Points
Exam Pearl
Q: What are the components of the deltoid ligament complex?
A: Superficial deltoid: Tibionavicular, tibiospring (tibiocalcaneonavicular), tibiocalcaneal. Deep deltoid: Anterior and posterior tibiotalar ligaments. Deep deltoid is primary restraint to lateral talar shift; superficial deltoid resists eversion. Injury often associated with lateral malleolus fracture or syndesmotic injury.
Exam Pearl
Q: What is the relationship between posterior tibial tendon dysfunction and medial ankle instability?
A: Stage II-IV PTTD often involves spring ligament attenuation and medial ankle instability. The spring ligament (calcaneonavicular) is part of medial support complex. PTTD progression leads to hindfoot valgus, forefoot abduction, and increased deltoid ligament stress. Reconstruction must address both tendon and ligament insufficiency.
Exam Pearl
Q: How is medial ankle instability assessed clinically?
A: Medial talar tilt test: Eversion stress - increased tilt indicates deltoid insufficiency. External rotation stress test: Tests deep deltoid. Compare to contralateral side. Medial clear space on mortise radiograph: greater than 4-5mm indicates deltoid incompetence. Often associated with valgus ankle deformity and lateral ankle impingement.
Exam Pearl
Q: What is the role of the spring ligament in medial ankle stability?
A: Spring ligament (calcaneonavicular) supports talar head and maintains longitudinal arch. Attenuation allows talar head plantar/lateral subluxation and contributes to flatfoot deformity. Works in conjunction with deltoid ligament and PTTD. Spring ligament reconstruction often required in adult-acquired flatfoot surgery.
Exam Pearl
Q: What are the surgical options for chronic medial ankle instability?
A: Direct repair: Rarely possible due to attenuated tissue. Reconstruction: Autograft (FHL, peroneus longus) or allograft recreating deltoid anatomy. Medializing calcaneal osteotomy reduces medial ligament stress. Concurrent procedures: Lateral lengthening, spring ligament reconstruction, FDL transfer if PTTD present. Address underlying alignment.
Australian Context
Practice in Australia
Epidemiology:
-
Medial ankle instability: 3-5% of ankle sprains
-
Often associated with ankle fractures (Weber B/C)
-
PTTD prevalence: 3-10% in adults over 40
-
49542: Ankle ligament reconstruction
-
49227: Tendon repair/reconstruction
-
49236: Tendon transfer procedures
Medicare Rebates
| Procedure | MBS Item | Fee |
|---|---|---|
| Ligament reconstruction | 49542 | $580-700 |
| Tendon reconstruction | 49227 | $450-550 |
| Tendon transfer | 49236 | $520-620 |
High-Yield Exam Summary
Immediate Answer Opener
- •Medial ankle instability from deltoid ligament insufficiency is uncommon (3-5% of ankle sprains) but clinically significant
- •Deltoid complex has superficial and deep components; deep layer critical for rotational stability and preventing lateral talar shift
- •Isolated injuries are rare; most occur with syndesmotic disruption, ankle fractures, or stage 4 PTTD
- •Diagnosis requires medial clear space assessment (pathologic if greater than 4mm), external rotation stress testing, and MRI
- •Conservative management succeeds in 60-70% of acute isolated injuries
- •Surgical treatment: primary repair for acute injuries with good tissue, or reconstruction using autograft for chronic insufficiency
Anatomy - Superficial vs Deep Deltoid
- •Superficial layer: Tibionavicular, tibiocalcaneal superficial, tibiospring ligaments from anterior colliculus - restrains hindfoot valgus
- •Deep layer: Anterior tibiotalar, posterior tibiotalar, tibiocalcaneal deep from intercollicular groove
- •Deep layer is critical restraint to external rotation and lateral talar translation
- •Deep posterior tibiotalar is strongest component and most important for stability
- •Spring ligament intimately associated with superficial deltoid, often injured concurrently
Associated Injury Patterns
- •Isolated deltoid (less than 5%): Rare, direct valgus force
- •Deltoid plus syndesmosis (40-60%): Pronation-external rotation mechanism, most common pattern
- •Ankle fractures (20-30%): Pronation-abduction with medial malleolus fracture or deltoid rupture
- •Stage 4 PTTD (10-15%): Chronic valgus deformity with progressive deltoid attenuation
- •Always assess for associated injuries before treating deltoid in isolation
Clinical Tests and Imaging
- •External rotation stress test: Foot externally rotated with tibia stabilized, pain and increased rotation indicates deltoid injury
- •Valgus stress test: Medial joint opening compared to contralateral
- •Kleiger test: External rotation with ankle dorsiflexed
- •Medial clear space on mortise radiograph: normal less than 4mm, pathologic if greater than 4mm or asymmetric
- •Weight-bearing radiographs essential
- •MRI shows grade 1 (intact with edema), grade 2 (partial tear), grade 3 (complete disruption)
Conservative vs Surgical Management
- •Conservative for isolated grade 1-2 injuries: CAM boot immobilization 4-6 weeks, protected weight-bearing, strengthening and proprioception training (60-70% success)
- •Surgical indications: Acute deltoid with syndesmotic injury requiring fixation, widened medial clear space despite syndesmotic reduction
- •Also surgical: Chronic symptomatic instability failed 4-6 months therapy, stage 4 PTTD with progressive deformity
- •Primary repair if acute with good tissue; reconstruction with autograft (hamstring) if chronic or poor quality tissue
Surgical Technique Pearls
- •Medial incision protecting saphenous nerve anteriorly, PTN bundle 1.5cm posterior to malleolus
- •Suture anchors at anatomic origins: anterior colliculus (superficial), intercollicular groove (deep)
- •Repair deep layer first for rotational stability
- •Ankle positioned in neutral dorsiflexion and 5 degrees hindfoot inversion during tie-down, NOT eversion or valgus
- •Assess medial clear space after syndesmotic fixation before deciding on deltoid repair
- •Spring ligament addressed if concurrent injury identified
Postoperative Protocol
- •0-2 weeks: Non-weight-bearing in splint/boot, suture removal 10-14 days
- •2-6 weeks: Progress to 50% weight-bearing in boot, begin gentle ROM avoiding forced eversion
- •6-12 weeks: Full weight-bearing in brace, progressive strengthening of tibialis posterior, proprioceptive training
- •3-6 months: Return to sport with functional testing, external bracing recommended for 12 months
- •Timeline longer than lateral ligament reconstruction due to weight-bearing role
Complications and Outcomes
- •Early: Saphenous nerve injury (10-15%, usually neurapraxia), wound healing problems (5-8%), PTN injury (less than 1% but catastrophic)
- •Late: Stiffness and loss of motion (15-20%), persistent instability (10-15%), post-traumatic arthritis (20-30% with fractures/syndesmotic injuries)
- •Outcomes: Primary repair 85-90% success, reconstruction 75-85% success
- •Combined procedures with PTTD reconstruction 70-80% success
- •Success rates lower than lateral ligament procedures with longer recovery