Nine Compartments | Calcaneal Fracture Association | Fasciotomy Controversy | Claw Toe Sequelae
COMPARTMENT ANATOMY
Critical Must-Knows
- Foot has nine distinct compartments separated by fascial septa
- Calcaneal fractures cause compartment syndrome in up to 10 percent of cases
- Clinical diagnosis relies on pain out of proportion and pain on passive stretch
- Fasciotomy versus delayed reconstruction remains controversial
- Untreated leads to intrinsic-minus claw toes and permanent stiffness
Clinical Pearls
- "Always measure pressures in calcaneal fractures with tense swelling
- "Central calcaneal compartment contains the lateral plantar nerve
- "Late claw toes result from intrinsic muscle necrosis and fibrosis
- "Fasciotomy incisions must address all nine compartments
Critical Foot Compartment Syndrome Points
Anatomy
Nine compartments: medial, lateral, superficial central, calcaneal (deep central), four interosseous, and adductor hallucis compartment in some descriptions. The calcaneal compartment communicates with the deep posterior leg compartment via the tarsal tunnel.
High-Risk Injuries
Calcaneal fractures (especially joint-depression types) and Lisfranc fracture-dislocations produce marked swelling within rigid fascial boundaries. Crush injuries, high-energy axial loading, and tight casts also precipitate acute compartment syndrome.
Diagnosis Thresholds
Absolute pressure greater than 30 mmHg or delta pressure (diastolic BP minus compartment pressure) less than 30 mmHg are commonly cited thresholds. Serial measurements every 1-2 hours are essential when clinical suspicion exists but pressures are borderline.
Treatment Decision
Early fasciotomy remains standard for confirmed acute compartment syndrome. However, many centres now favour selective fasciotomy with close monitoring because late reconstruction of claw toes and contractures can be performed electively with reasonable functional outcomes.
Quick Decision Guide
| Presentation | Diagnosis | Treatment | Key Pearl |
|---|---|---|---|
| Calcaneal fracture, tense swelling, severe pain | Compartment pressure greater than 30 mmHg or delta P less than 30 | Urgent fasciotomy of all nine compartments | Measure pressures before and after fracture fixation |
| Lisfranc injury with foot swelling | Pain on passive toe stretch, tense plantar arch | Serial pressure monitoring, fasciotomy if thresholds met | Central calcaneal compartment most commonly elevated |
| Late presentation with claw toes | Intrinsic muscle fibrosis, fixed deformities | Delayed reconstruction: tendon transfers, osteotomies | Prevent with early recognition in high-energy fractures |
MLSCIAINine Foot Compartments
| M | Medial Abductor hallucis compartment |
| L | Lateral Abductor digiti minimi compartment |
| S | Superficial central Flexor digitorum brevis |
| C | Calcaneal Quadratus plantae and lateral plantar nerve |
| I | Interosseous (4) Dorsal and plantar interossei in four spaces |
| A | Adductor Adductor hallucis (transverse and oblique heads) |
| I | Interosseous again Remember four separate interosseous compartments |
| M | Medial Abductor hallucis compartment | C | Calcaneal Quadratus plantae and lateral plantar nerve | I | Interosseous again Remember four separate interosseous compartments |
| L | Lateral Abductor digiti minimi compartment | I | Interosseous (4) Dorsal and plantar interossei in four spaces | ||
| S | Superficial central Flexor digitorum brevis | A | Adductor Adductor hallucis (transverse and oblique heads) |
Hook:MLSCIAI - nine compartments that must all be released in foot compartment syndrome!
DELTA30Pressure Measurement Thresholds
| D | Diastolic pressure Measure systemic diastolic blood pressure |
| E | Elevated compartment Measure each of the nine foot compartments |
| L | Less than 30 mmHg Delta pressure threshold for fasciotomy |
| T | Threshold absolute Compartment pressure greater than 30 mmHg also indicates release |
| A | Always serial Repeat measurements if borderline or clinical suspicion high |
| 3 | 30 mmHg rule Both absolute and perfusion pressure criteria used together |
| 0 | Zero tolerance Do not wait for neurologic deficit - irreversible damage occurs early |
| D | Diastolic pressure Measure systemic diastolic blood pressure | T | Threshold absolute Compartment pressure greater than 30 mmHg also indicates release | 0 | Zero tolerance Do not wait for neurologic deficit - irreversible damage occurs early |
| E | Elevated compartment Measure each of the nine foot compartments | A | Always serial Repeat measurements if borderline or clinical suspicion high | ||
| L | Less than 30 mmHg Delta pressure threshold for fasciotomy | 3 | 30 mmHg rule Both absolute and perfusion pressure criteria used together |
Hook:DELTA30 guides fasciotomy decision - never rely on a single pressure reading!
CLAWTOELate Sequelae Management
| C | Claw toes Intrinsic minus posture from muscle necrosis |
| L | Late reconstruction Tendon transfers and osteotomies after swelling subsides |
| A | Amputation risk Severe untreated cases may require below-knee amputation |
| W | Wound management Delayed primary closure or skin grafting after fasciotomy |
| T | Tendon transfers FHL to extensor tendons for claw toe correction |
| O | Osteotomies Metatarsal shortening or proximal interphalangeal fusions |
| E | Early prevention Best outcome is avoiding the need for late reconstruction |
| C | Claw toes Intrinsic minus posture from muscle necrosis | W | Wound management Delayed primary closure or skin grafting after fasciotomy | E | Early prevention Best outcome is avoiding the need for late reconstruction |
| L | Late reconstruction Tendon transfers and osteotomies after swelling subsides | T | Tendon transfers FHL to extensor tendons for claw toe correction | ||
| A | Amputation risk Severe untreated cases may require below-knee amputation | O | Osteotomies Metatarsal shortening or proximal interphalangeal fusions |
Hook:CLAWTOE reminds you of the devastating late consequences of missed foot compartment syndrome!
Overview and Epidemiology
Why This Matters
Foot compartment syndrome is a limb-threatening emergency that is frequently underdiagnosed in association with calcaneal fractures and Lisfranc injuries. The foot's nine rigid fascial compartments leave little room for swelling, and delayed diagnosis leads to irreversible muscle necrosis, intrinsic-minus claw toes, chronic pain, and in severe cases amputation. Early pressure measurement and timely fasciotomy remain the only means of preventing these sequelae, yet controversy persists regarding the necessity of fasciotomy in every case meeting pressure thresholds.
Mechanism of Injury
- Calcaneal fractures: Axial loading produces massive swelling within the calcaneal and central compartments
- Lisfranc fracture-dislocations: Tarsometatarsal disruption causes bleeding into multiple interosseous and central compartments
- Crush injuries: Industrial or motor-vehicle trauma directly compresses the plantar compartments
- Tight casting: Circumferential casts applied to swollen feet create iatrogenic compartment syndrome
- High-energy axial load: Falls from height or motorcycle accidents
Clinical Impact
- Muscle necrosis: Intrinsic muscles die within 4-6 hours of critical ischaemia
- Claw toe deformity: Fibrosis of intrinsics produces intrinsic-minus posture
- Chronic pain: Persistent plantar neuropathic pain from nerve compression
- Stiffness: Global foot rigidity limits gait and shoe wear
- Amputation: Up to 10 percent of severe untreated cases progress to below-knee amputation
Pathophysiology
Fascial Anatomy of the Foot
The foot is divided into nine distinct compartments by tough fascial septa arising from the plantar aponeurosis and intermetatarsal ligaments. The medial compartment contains abductor hallucis. The lateral compartment houses abductor digiti minimi. The central compartment is subdivided into superficial (flexor digitorum brevis) and deep calcaneal (quadratus plantae and lateral plantar neurovascular bundle) layers. Four separate interosseous compartments exist between the metatarsals, and the adductor hallucis occupies its own transverse and oblique head compartment. The calcaneal compartment communicates proximally with the deep posterior compartment of the leg through the tarsal tunnel, allowing pressure transmission in both directions.
Compartment Contents and Clinical Relevance
| Compartment | Key Structures | Clinical Consequence if Necrotic | Release Incision |
|---|---|---|---|
| Medial | Abductor hallucis, medial plantar nerve | Loss of great toe abduction, medial foot pain | Medial hindfoot incision |
| Lateral | Abductor digiti minimi, lateral plantar nerve branch | Little toe abduction loss, lateral foot pain | Lateral hindfoot incision |
| Calcaneal (Deep Central) | Quadratus plantae, lateral plantar nerve and vessels | Intrinsic-minus clawing, plantar numbness | Plantar central deep release |
| Interosseous (4) | Dorsal and plantar interossei, metatarsal arteries | Metatarsal head necrosis, web-space pain | Dorsal intermetatarsal incisions |
Pressure Dynamics
Normal resting pressure: 0-8 mmHg Critical ischaemia threshold: compartment pressure greater than 30 mmHg or delta pressure less than 30 mmHg for greater than 4-6 hours Calcaneal fractures: pressures often exceed 40-60 mmHg within the calcaneal compartment due to bleeding from the bone and surrounding soft tissues Lisfranc injuries: interosseous and central compartments most affected by haemorrhage tracking along the tarsometatarsal joints
Why the Foot is Vulnerable
Rigid fascial boundaries: nine separate envelopes with minimal compliance Dependent position: gravity increases hydrostatic pressure in the foot Limited collateral flow: single dominant posterior tibial artery contribution Communication with leg: tarsal tunnel allows pressure to rise from leg compartments or transmit distally Small volume: even modest bleeding produces rapid pressure elevation
Classification and Types
Classification by Associated Injury
| Injury Type | Compartment Risk | Typical Pressures | Fasciotomy Rate |
|---|---|---|---|
| Calcaneal fracture (joint depression) | Calcaneal and central compartments highest | Often greater than 40 mmHg | Up to 10 percent require fasciotomy |
| Lisfranc fracture-dislocation | Interosseous and central compartments | 30-50 mmHg common | Selective, 5-15 percent |
| Crush injury foot | Multiple compartments simultaneously | Variable, often all nine elevated | High fasciotomy rate |
| Tight cast or dressing | Global elevation possible | Reversible if cast removed early | Rare if recognised promptly |
High-energy calcaneal fractures remain the strongest predictor of foot compartment syndrome and should trigger routine pressure monitoring in the first 24-48 hours.
Clinical Assessment
History
- Mechanism: High-energy axial load, calcaneal fracture, Lisfranc injury, crush
- Timing: Onset of severe pain relative to injury or cast application
- Pain character: Deep, burning, out of proportion to visible injury
- Analgesia requirement: Escalating opioid needs despite fracture stabilisation
- Sensory change: Numbness in plantar distribution (lateral plantar nerve)
Examination
- Inspect: Tense, shiny plantar skin, loss of skin wrinkles, massive swelling
- Palpate: Rock-hard compartments, especially calcaneal and central
- Passive stretch: Severe pain on passive toe flexion or extension (most sensitive sign)
- Active movement: Weak or absent intrinsic function
- Neurologic: Diminished plantar sensation, two-point discrimination greater than 6 mm
- Vascular: Dorsalis pedis and posterior tibial pulses usually preserved until late
Pain on Passive Stretch: The Most Reliable Clinical Sign
Technique: Stabilise the ankle and gently extend or flex the toes while observing patient response. Pain out of proportion or disproportionate guarding indicates rising compartment pressure. Interpretation: Positive in greater than 90 percent of confirmed cases before neurologic deficit appears. Pitfall: In the multiply injured or sedated patient this sign may be masked; rely on pressure measurement and serial examination. Key point: Never wait for the five P's (pain, pallor, paraesthesia, paralysis, pulselessness) - these are late, irreversible signs.
Differential Diagnosis of the Painful Swollen Foot
| Condition | Distinguishing Feature | Pressure Measurement | Management Difference |
|---|---|---|---|
| Foot compartment syndrome | Pain on passive stretch, tense compartments | Elevated greater than 30 mmHg or delta less than 30 | Fasciotomy of all nine compartments |
| Calcaneal fracture alone | Heel pain, swelling, no disproportionate pain | Normal or mildly elevated | Fracture management, elevation, monitoring |
| Infection / cellulitis | Erythema, warmth, systemic signs | Normal pressures | Antibiotics, possible drainage |
| Deep vein thrombosis | Calf swelling, Homan sign positive | Normal foot pressures | Anticoagulation, vascular consult |
Investigations
Diagnostic Protocol
Indications: Any calcaneal fracture with tense swelling, Lisfranc injury with severe pain, crush injury, or clinical suspicion. Technique: Use a handheld manometer or arterial-line transducer. Measure all nine compartments through separate needle insertions. Record absolute pressure and calculate delta pressure using diastolic blood pressure. Thresholds: Absolute pressure greater than 30 mmHg or delta pressure less than 30 mmHg warrants strong consideration of fasciotomy. Serial measurements every 1-2 hours if borderline.
Views: AP, lateral, oblique, and Harris heel views of the foot and ankle. Purpose: Identify calcaneal fracture pattern (Essex-Lopresti or Sanders classification), Lisfranc displacement, or other bony injury that may require fixation in the same sitting as fasciotomy. Clinical correlation: Fracture classification does not predict compartment pressures; measure pressures regardless of fracture type.
CT: Useful for surgical planning of calcaneal fracture fixation after fasciotomy decision is made. MRI: Rarely required acutely; may show muscle oedema but delays intervention and is not used for diagnosis of compartment syndrome. Key point: Imaging confirms the fracture but the diagnosis of compartment syndrome is made by pressure measurement and clinical correlation.
Pressure Measurement Pearl
Always measure the calcaneal (deep central) compartment first in calcaneal fractures - it is the most commonly elevated and contains the lateral plantar nerve. If pressures are borderline, repeat after 30-60 minutes of observation or after fracture reduction. Document both absolute and delta pressures in the notes before proceeding to fasciotomy.
Management Algorithm
Acute Compartment Syndrome Requiring Fasciotomy
Goal: Release all nine compartments through minimal incisions while protecting neurovascular structures and allowing subsequent fracture fixation.
Surgical Protocol
Position: Supine with bump under ipsilateral hip, foot at end of table. Tourniquet: Use only if needed for fracture fixation; avoid prolonged tourniquet time before fasciotomy. Equipment: Handheld manometer confirmation in theatre, fine scissors, retractors, skin-marking pen.
Medial incision: 6 cm incision along medial foot from navicular to calcaneal tuberosity, releasing medial and superficial central compartments. Lateral incision: 6 cm incision along lateral foot parallel to plantar surface, releasing lateral and interosseous compartments. Plantar central: Connect or separate incision to release calcaneal (deep) compartment and protect lateral plantar nerve. Dorsal intermetatarsal: Two or three dorsal incisions between metatarsals to release all four interosseous compartments and adductor hallucis.
Complete fascial division: Ensure each compartment is fully released from proximal to distal. Protect neurovascular bundles: Identify and preserve medial and lateral plantar nerves during central compartment release. Debride necrotic muscle: Any obviously dead muscle should be excised at the index procedure. Leave wounds open: Plan for delayed primary closure or skin grafting at 5-7 days.
Elevation: Strict elevation for 48 hours to reduce oedema. Wound care: Negative-pressure dressing or moist gauze, return to theatre in 48-72 hours for inspection and possible closure. Fracture fixation: Perform ORIF of calcaneal or Lisfranc injury once swelling allows, usually 7-14 days later. Rehabilitation: Early active toe motion, progressive weight-bearing once wounds stable.
Fasciotomy Pearl
The calcaneal compartment must be released through a separate deep plane because it lies beneath the superficial central compartment. Failure to release the calcaneal compartment leaves the quadratus plantae and lateral plantar nerve compressed, resulting in persistent clawing and plantar numbness despite release of the other eight compartments.
Outcomes and Prognosis
Functional Outcomes by Timing of Intervention
| Timing of Fasciotomy | Muscle Viability | Claw Toe Rate | Return to Work |
|---|---|---|---|
| Less than 6 hours | Greater than 90 percent viable | Less than 10 percent | 80-90 percent at 3-6 months |
| 6-12 hours | 70-80 percent viable | 20-30 percent | 60-70 percent at 6 months |
| Greater than 24 hours or none | Less than 50 percent viable | Greater than 70 percent | Less than 40 percent, many require late surgery |
Prognostic Factors
Best prognosis: Early diagnosis (less than 6 hours), complete nine-compartment release, young patient, low-energy mechanism, compliant rehabilitation. Poor prognosis: Delayed presentation (greater than 24 hours), incomplete release (especially calcaneal compartment), high-energy crush, associated open fracture or vascular injury, smoking, diabetes. Key threshold: 6 hours from onset of critical pressure elevation - muscle necrosis becomes irreversible beyond this window in most patients.
Evidence Base and Key Trials
Compartment syndromes of the foot after calcaneal fractures
- Linked calcaneal fractures to high risk of foot compartment syndrome
- Advocated early fasciotomy through multiple incisions to prevent claw toe deformity
Experimental decompression of the fascial compartments of the foot--the basis for fasciotomy in acute compartment syndromes
- Cadaver study defining nine foot compartments and safe release techniques
- Provided anatomic basis for multi-incision fasciotomy approach
Foot compartment syndrome
- Review of diagnosis and management emphasizing clinical signs and pressure thresholds
- Highlighted calcaneal compartment as most frequently elevated in trauma
Compartment syndrome of the foot after calcaneal fracture
- Case report of compartment syndrome following calcaneal fracture
- Stressed importance of early recognition and fasciotomy in emergency setting
Exam Viva Scenarios
Use these scenarios to practise clinical reasoning and management decisions
Scenario 1: Calcaneal Fracture with Suspected Compartment Syndrome
"A 42-year-old roofer falls 4 metres onto his right heel. He has a closed Sanders type III calcaneal fracture with massive foot swelling. Six hours after injury he complains of severe burning plantar pain despite opioid analgesia. The foot is tense, especially over the medial arch. What is your assessment and management?"
Scenario 2: Late Presentation with Claw Toes
"A 35-year-old man sustained a crush injury to his foot 8 weeks ago that was treated non-operatively elsewhere. He now presents with fixed clawing of all lesser toes, loss of plantar sensation, and inability to wear normal shoes. The foot is stiff and painful. How would you manage this?"
MCQ Practice Points
Anatomy Question
Q: How many compartments does the foot have and which is most clinically important in calcaneal fractures? A: The foot has nine compartments. The calcaneal (deep central) compartment is most clinically important in calcaneal fractures because it contains the quadratus plantae and the lateral plantar neurovascular bundle; its release is frequently incomplete if not specifically addressed through a deep plane.
Diagnosis Question
Q: What are the pressure thresholds for fasciotomy in foot compartment syndrome? A: Absolute compartment pressure greater than 30 mmHg or delta pressure (diastolic blood pressure minus compartment pressure) less than 30 mmHg. Serial measurements are essential when values are borderline, and the decision integrates both pressure data and clinical signs.
Sequelae Question
Q: What late deformity occurs if foot compartment syndrome is missed? A: Intrinsic-minus claw toe deformity. Necrosis of the intrinsic muscles (especially quadratus plantae and interossei) removes their opposition to the long flexors and extensors, producing hyperextension at the metatarsophalangeal joints and flexion at the interphalangeal joints.
Treatment Question
Q: What incisions are required for complete nine-compartment release? A: Medial hindfoot incision (medial and superficial central compartments), lateral hindfoot incision (lateral and interosseous compartments), separate deep central release for the calcaneal compartment, and two to three dorsal intermetatarsal incisions for the four interosseous compartments and adductor hallucis.
Guidelines, Registries & Global Practice
Global Epidemiology
- Calcaneal fractures account for 1-2 percent of all fractures worldwide and are the leading cause of foot compartment syndrome
- Incidence of compartment syndrome after calcaneal fracture ranges from 4-10 percent in published series across trauma centres
- High-energy axial loading mechanisms predominate in industrial and motor-vehicle settings globally
- Missed diagnosis remains a significant source of litigation in foot and ankle trauma worldwide
Practice Variation by Resource Setting
- High-resource centres: routine pressure monitoring with handheld manometers, dedicated foot and ankle trauma lists, negative-pressure wound therapy for open fasciotomy wounds
- Limited-resource settings: reliance on clinical signs and serial examination, improvised fasciotomy incisions, delayed wound closure with skin grafts when available
- Universal principle: outcome depends on early recognition and complete release of all nine compartments regardless of available technology
- Surgery: late reconstruction expertise is concentrated in specialist foot and ankle units globally
Society and Reference Guidance (Side by Side)
| Source | Diagnosis emphasis | Acute treatment | Late reconstruction |
|---|---|---|---|
| AAOS / AOFAS (US) | Pressure measurement in all high-risk calcaneal and Lisfranc injuries | Fasciotomy when absolute greater than 30 mmHg or delta less than 30 mmHg | Tendon transfers and osteotomies for established claw toes |
| BOA / BSSH (UK) | High index of suspicion, serial clinical examination, selective pressure measurement | Early fasciotomy for confirmed cases, close monitoring for borderline | Multidisciplinary foot and ankle reconstruction pathways |
| AO Foundation | Compartment pressure monitoring as standard in calcaneal fracture protocols | Complete nine-compartment release through described incisions | Staged reconstruction after soft-tissue recovery |
| EFORT / European consensus | Awareness of tarsal tunnel communication with leg compartments | Individualised decision-making integrating pressure and clinical data | Emphasis on prevention and early referral to specialist units |
Registry and Evidence Note
No dedicated international registry tracks foot compartment syndrome outcomes. Evidence is derived from small prospective series and expert consensus. The trend toward selective rather than routine fasciotomy reflects recognition that many patients with moderately elevated pressures recover without surgery, while those who develop fixed claw toes can still achieve useful function with delayed reconstruction. Documentation of pressure measurements and clinical rationale for or against fasciotomy is essential for medicolegal protection worldwide.
Controversies & Areas of Uncertainty
Routine versus selective fasciotomy
Absolute pressure thresholds (greater than 30 mmHg) have driven routine fasciotomy in many centres, yet recent series suggest selective monitoring is safe when delta pressure remains above 25-30 mmHg and clinical signs are improving. No randomised trial exists to settle the question.
Optimal number of incisions
Classic teaching requires four separate incisions to release all nine compartments reliably. Some surgeons advocate three-incision techniques with acceptable release rates, but cadaveric studies show incomplete deep central release when incisions are minimised.
Role of continuous pressure monitoring
Indwelling catheter systems provide continuous readings but add cost, infection risk, and potential for measurement error. Intermittent handheld manometry remains the global standard; no high-quality evidence demonstrates superiority of continuous systems in the foot.
Timing of fracture fixation after fasciotomy
Traditional teaching delays ORIF 7-14 days until swelling subsides. Some centres now perform acute fixation at the time of fasciotomy using minimally invasive techniques, but wound complication rates and long-term outcomes require further study.
FOOT COMPARTMENT SYNDROME
Clinical summary
Key Anatomy
- •Nine compartments: medial, lateral, superficial central, calcaneal (deep central), four interosseous, adductor hallucis
- •Calcaneal compartment contains quadratus plantae and lateral plantar neurovascular bundle
- •Tarsal tunnel communication allows pressure transmission between leg and foot
- •Intrinsic muscles (especially quadratus plantae) are critical for toe balance
Diagnosis
- •Pain out of proportion and pain on passive toe stretch are most sensitive clinical signs
- •Pressure thresholds: absolute greater than 30 mmHg or delta (diastolic minus compartment) less than 30 mmHg
- •Measure all nine compartments serially when suspicion exists
- •Calcaneal fractures and Lisfranc injuries carry highest risk
Treatment Algorithm
- •Acute confirmed compartment syndrome: urgent nine-compartment fasciotomy
- •Medial, lateral, plantar central, and dorsal intermetatarsal incisions required
- •Selective monitoring acceptable in borderline cases with close observation
- •Late claw toes treated with FHL transfer, osteotomies, and joint fusions
Critical Thresholds
- •Absolute pressure greater than 30 mmHg = consider fasciotomy
- •Delta pressure less than 30 mmHg = consider fasciotomy
- •Time window for reversible muscle ischaemia approximately 4-6 hours
- •Delayed presentation (greater than 24 hours) shifts focus to late reconstruction
Sequelae & Prevention
- •Missed compartment syndrome produces intrinsic-minus claw toe deformity
- •Late reconstruction improves but rarely normalises function
- •Best outcome achieved by early recognition and complete release
- •Always document pressure measurements and clinical rationale in high-risk fractures