METATARSAL STRESS FRACTURES
MT2 Marching Fracture | MT5 High-Risk Zones | Female Athlete Triad | MRI Gold Standard | Activity Modification
STRESS FRACTURE SEVERITY
Critical Must-Knows
- Second metatarsal is most common site (marching fracture) - usually low-risk, conservative treatment
- Fifth metatarsal Zone 2-3 are HIGH-RISK locations - 50%+ nonunion rate, often need surgery
- MRI is gold standard for early diagnosis - X-rays negative for 2-3 weeks after symptom onset
- Female athlete triad (energy deficiency, amenorrhea, low BMD) increases stress fracture risk
- Activity modification is cornerstone - address training errors, biomechanics, nutrition
Examiner's Pearls
- "MT2 stress fracture = 'marching fracture' - most common, usually conservative, good prognosis
- "MT5 Zone 2-3 stress fractures = high nonunion risk = surgical fixation in athletes
- "X-ray delay: symptoms appear 2-3 weeks before radiographic changes (MRI earlier)
- "Bone scan vs MRI: MRI more specific, shows fracture line and edema pattern
- "Return to sport: 6-8 weeks for low-risk, 10-12 weeks for high-risk (MT5 Zone 2-3)
Clinical Imaging
Imaging Gallery
Critical Exam Points for Metatarsal Stress Fractures
Site-Specific Risk
MT5 Zone 2-3 = HIGH-RISK - 50%+ nonunion, need surgery. MT2 = low-risk, usually conservative
Diagnosis Timing
X-rays negative for 2-3 weeks - MRI gold standard for early diagnosis before radiographic changes
Risk Factor Assessment
Female athlete triad, training errors, biomechanics, nutrition - must address underlying causes
Treatment Algorithm
Low-risk (MT2-4): Activity mod. High-risk (MT5 Zone 2-3): Surgical fixation in athletes
At a Glance: Quick Decision Guide
| Location | Risk Level | Treatment | Key Pearl |
|---|---|---|---|
| MT2-4 shaft (marching fracture) | Low risk | Activity modification, CAM boot 4-6 weeks | Most common, excellent prognosis with rest |
| MT1 stress fracture | Moderate risk | NWB 6-8 weeks, bone stimulator | Weight-bearing importance - lower threshold for surgery |
| MT5 Zone 2-3 | HIGH RISK | Surgical fixation (IM screw) in athletes | 50%+ nonunion rate - watershed blood supply |
| Multiple metatarsals | High risk | Comprehensive workup, address systemic causes | Female athlete triad, nutrition, biomechanics |
STRESSSTRESS - Risk Factors and Management
Memory Hook:STRESS fractures need STRESS management - Site-specific risk, Training errors, Risk factors, Early MRI, Surgery for high-risk, Systematic approach
MARCHINGMARCHING - MT2 Stress Fracture Features
Memory Hook:MARCHING fractures are the most common - Most common site, Activity modification, Rapid recovery, Conservative treatment, High success, Inferior cortex, No surgery, Gradual return
ZONEZONE - Fifth Metatarsal Risk Zones
Memory Hook:ZONE classification determines risk - Zone 1 low risk, Zone 2-3 HIGH RISK, Nonunion risk high, Early surgery for athletes
Overview and Epidemiology
Why This Topic Matters
Metatarsal stress fractures are among the most common stress fractures in athletes and military recruits. The second metatarsal ("marching fracture") is the most frequent site, typically low-risk with excellent prognosis. However, fifth metatarsal Zone 2-3 stress fractures have high nonunion rates (50%+) due to watershed blood supply, requiring surgical fixation in athletes. Understanding site-specific risk and treatment algorithms is critical for exam success.
Demographics
- Athletes: Runners, dancers, military recruits
- Age: Peak 20-30 years
- Gender: 2-3x higher in females (triad risk)
- Sports: Track, basketball, ballet, marching
Impact
- Training interruption: 6-12 weeks
- High-risk sites: 50%+ nonunion without surgery
- Recurrence risk: If underlying causes not addressed
- Career impact: Professional athletes need early surgery
Anatomy and Pathophysiology
Watershed Blood Supply - Fifth Metatarsal Zone 2-3
The metadiaphyseal junction (Zone 2) and proximal diaphysis (Zone 3) of the fifth metatarsal represent a watershed zone where nutrient artery supply meets periosteal supply. This creates a relative avascular zone with poor healing potential, explaining the 50%+ nonunion rate in these locations. This is why Zone 2-3 stress fractures require surgical fixation in athletes.
| Metatarsal | Blood Supply | Stress Fracture Risk | Clinical Significance |
|---|---|---|---|
| MT1 | Dual supply (medial/lateral plantar) | Moderate (weight-bearing importance) | Lower threshold for surgery due to load |
| MT2-4 | Adequate nutrient artery supply | Low (MT2 most common but low-risk) | Excellent healing with activity modification |
| MT5 Zone 1 | Periosteal supply adequate | Low (tuberosity avulsion different) | Conservative treatment successful |
| MT5 Zone 2-3 | Watershed zone (poor supply) | VERY HIGH (50%+ nonunion) | Surgical fixation required in athletes |
Biomechanical Factors
- MT2: Longest, most rigidly fixed at TMT joint
- Load concentration: Inferior cortex of MT2 shaft
- Repetitive loading: Running, jumping, marching
- Fatigue failure: Microfractures exceed repair capacity
Pathophysiology
- Bone remodeling: Osteoclasts > osteoblasts with overuse
- Microfracture accumulation: Exceeds repair capacity
- Cortical breach: Starts on tension side (inferior cortex)
- Complete fracture: If activity continues
Classification Systems
Metatarsal Stress Fracture Sites
| Site | Risk Level | Nonunion Risk | Treatment |
|---|---|---|---|
| MT2 shaft (marching fracture) | Low | Under 5% | Activity modification, CAM boot 4-6 weeks |
| MT1 | Moderate | 10-15% | NWB 6-8 weeks, consider bone stimulator |
| MT5 Zone 2 (metadiaphyseal) | HIGH | 50%+ | Surgical fixation in athletes |
| MT5 Zone 3 (proximal diaphysis) | HIGH | 50%+ | Surgical fixation + bone graft if delayed |
Key Distinction
MT2 stress fracture (marching fracture) is the most common but has low nonunion risk - excellent prognosis with conservative treatment. MT5 Zone 2-3 stress fractures are less common but have HIGH nonunion risk (50%+) - require surgical fixation in athletes. Site determines risk, not frequency.
Clinical Assessment
History
- Onset: Gradual, insidious (weeks to months)
- Mechanism: Repetitive loading, training errors
- Pain: Initially with activity, progresses to rest pain
- Training changes: Recent increase in volume/intensity
- Risk factors: Female athlete triad, nutrition, biomechanics
Examination
- Point tenderness: Over specific metatarsal
- Swelling: Localized, minimal in early stages
- Tuning fork test: Vibration over fracture site causes pain
- Hop test: Single-leg hop reproduces pain
- Neurovascular: Usually intact
Beware the High-Risk Site
Fifth metatarsal Zone 2-3 stress fractures may present with minimal symptoms initially but have 50%+ nonunion risk. Any athlete with MT5 base pain and training history should have early MRI to assess Zone 2-3 involvement. Delayed diagnosis leads to nonunion requiring bone graft.
Differential Diagnosis
| Condition | Key Features | Distinguishing Factor |
|---|---|---|
| Metatarsal stress fracture | Point tenderness, insidious onset, training history | MRI shows fracture line and edema |
| Metatarsalgia | Diffuse forefoot pain, no point tenderness | No fracture on imaging |
| Morton's neuroma | Interdigital pain, Mulder's click | Between metatarsals, not over bone |
| Freiberg's disease | MT2 head avascular necrosis | X-ray shows collapse, not stress fracture |
Investigations
Imaging Protocol
Initial X-rays often negative - stress fractures take 2-3 weeks to show radiographic changes.
Views: AP, lateral, oblique foot
Early findings: None (X-ray negative period)
Later findings:
- Periosteal reaction (2-3 weeks)
- Fracture line (3-4 weeks)
- Callus formation (4-6 weeks)
Best for early diagnosis - shows changes within days of symptom onset.
Findings:
- Bone marrow edema (T2 hyperintensity)
- Fracture line (T1 hypointense line)
- Periosteal reaction
Advantages: High sensitivity, shows extent, guides treatment
Sensitive but less specific than MRI.
Findings: Increased uptake at fracture site
Use: If MRI unavailable, but MRI preferred for specificity
Imaging Timing
X-rays are negative for 2-3 weeks after symptom onset. If clinical suspicion is high (point tenderness, training history), order MRI immediately rather than waiting for radiographic changes. Early diagnosis allows prompt treatment and prevents progression to complete fracture.
Management Algorithm
Conservative Management
Goal: Pain-free healing with activity modification
Treatment Steps
Activity modification: Stop running/jumping activities
Weight-bearing: CAM boot, weight-bearing as tolerated
Pain control: NSAIDs, ice
Address risk factors: Training errors, nutrition, biomechanics
If pain-free: Progress to walking, then light jogging
Monitor: No return of pain with activity
Cross-training: Swimming, cycling to maintain fitness
Follow-up: X-ray at 6 weeks to confirm healing
Criteria: Pain-free, no tenderness, X-ray shows healing
Progression: Gradual increase in intensity
Prevention: Address underlying causes (training, biomechanics)
Key Point
MT2 stress fractures (marching fracture) have excellent prognosis with conservative treatment. Success rate over 95% with proper activity modification. Surgery rarely needed unless displaced or nonunion.
Surgical Technique
MT5 Zone 2-3 Stress Fracture Fixation
Indication: High-risk stress fractures (MT5 Zone 2-3) in athletes
Surgical Steps
Supine on radiolucent table
C-arm: Positioned for AP and lateral views
Limb: Free draped, accessible for screw insertion
Location: Tip of fifth metatarsal tuberosity
Landmark: Palpable prominence at base of MT5
Incision: Small (1-2cm) longitudinal over tuberosity
Protect: Sural nerve branches
Insertion: Under fluoroscopy guidance
Path: Down medullary canal, across fracture
Endpoint: Engage far cortex (distal)
Confirm: AP and lateral views show correct position
Size: Minimum 5.5mm diameter (larger better)
Length: Measure from guidewire, engage far cortex
Compression: Partially threaded or fully threaded with compression
Final check: Fluoroscopy confirms compression and position
Indication: Torg Type II-III (sclerotic canal, delayed/nonunion)
Technique: Curettage of sclerotic bone, autograft from iliac crest
Placement: Around fracture site, then screw fixation
Alternative: Allograft bone chips if autograft not desired
Layers: Subcutaneous, skin
Dressing: Sterile, non-adherent
Splint: Posterior splint for comfort (remove in 1-2 weeks)
Pearls
- Screw size matters: 5.5mm minimum, larger diameter better outcomes
- Entry point critical: Tip of tuberosity, not too medial
- Engage far cortex: Essential for compression and stability
- Fluoroscopy: Confirm position before final tightening
Pitfalls
- Undersized screw: Less than 5.5mm increases failure risk
- Wrong entry point: Too medial risks peroneal tendon injury
- Incomplete engagement: Screw not engaging far cortex
- Missed sclerosis: Torg Type II-III need bone graft
Screw Technique
Screw size is critical - minimum 5.5mm diameter recommended. Studies show better outcomes with larger screws (5.5-6.5mm) compared to 4.5mm. Entry at tip of tuberosity, engage far cortex for compression. For Torg Type II-III, add bone graft after curettage of sclerotic canal.
Complications
| Complication | Incidence | Risk Factors | Management |
|---|---|---|---|
| Nonunion | 50%+ (MT5 Zone 2-3 conservative) | High-risk site, continued activity, Torg Type II-III | Surgical fixation + bone graft |
| Delayed union | 10-20% (all sites) | Inadequate rest, poor nutrition, biomechanics | Extended NWB, bone stimulator, address causes |
| Recurrence | 20-30% | Underlying causes not addressed | Comprehensive risk factor management |
| Malunion | Rare (if displaced) | Inadequate reduction, continued weight-bearing | Osteotomy if symptomatic |
| Hardware issues | 5-10% (surgical) | Undersized screw, poor technique | Revision surgery if symptomatic |
Nonunion Risk - MT5 Zone 2-3
Fifth metatarsal Zone 2-3 stress fractures have 50%+ nonunion rate with conservative treatment due to watershed blood supply. Athletes should have early surgical fixation to prevent nonunion. Non-athletes may attempt conservative trial but must be counseled about high failure rate and need for eventual surgery.
Postoperative Care and Rehabilitation
Rehabilitation Timeline
Activity: Complete rest from running/jumping
Weight-bearing: CAM boot, weight-bearing as tolerated
Pain control: NSAIDs, ice
Cross-training: Swimming, cycling (if pain-free)
If pain-free: Progress to walking without boot
Activity: Light activities of daily living
Monitor: No return of pain
Continue: Address risk factors (training, nutrition)
Activity: Light jogging if pain-free
Progression: Gradual increase in distance/intensity
Stop if: Pain returns
Follow-up: X-ray at 6 weeks
Criteria: Pain-free, no tenderness, X-ray shows healing
Sport-specific: Gradual return to full activity
Prevention: Maintain risk factor management
Outcomes and Prognosis
| Site | Conservative Success | Surgical Success | Return to Sport |
|---|---|---|---|
| MT2 (marching fracture) | 95%+ (6-8 weeks) | N/A (rarely needed) | 6-8 weeks |
| MT1 | 85-90% (8-10 weeks) | 95%+ (if needed) | 8-10 weeks |
| MT5 Zone 2-3 | Under 50% (high nonunion) | 90%+ (8-10 weeks) | 8-10 weeks surgical |
Predictors of Outcome
Site is the strongest predictor: MT2 has excellent prognosis (95%+), MT5 Zone 2-3 has poor prognosis without surgery (under 50%). Early diagnosis and treatment improve outcomes. Addressing risk factors prevents recurrence. Athletes with MT5 Zone 2-3 should have early surgery for reliable healing and timely return.
Evidence Base and Key Trials
Fifth Metatarsal Stress Fracture Outcomes
- Retrospective review: 5.5mm screws better outcomes than 4.5mm
- Larger diameter screws reduce failure rate
- Minimum 5.5mm recommended for MT5 Zone 2-3 fixation
Metatarsal Stress Fracture Risk Factors
- Prospective study: Female athletes 2-3x higher risk
- Training errors, low BMD, menstrual dysfunction increase risk
- Comprehensive risk factor assessment essential
Second Metatarsal Stress Fracture (Marching Fracture)
- MT2 is most common metatarsal stress fracture site
- Excellent prognosis with conservative treatment (95%+ success)
- 6-8 weeks activity modification usually sufficient
Fifth Metatarsal Zone Classification and Nonunion Risk
- Zone 2-3 have high nonunion risk (50%+) with conservative treatment
- Watershed blood supply explains poor healing
- Athletes benefit from early surgical fixation
Stress Fracture Diagnosis - MRI vs X-ray
- MRI shows changes within days of symptom onset
- X-rays negative for 2-3 weeks after symptoms
- MRI more specific than bone scan for fracture line
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
Scenario 1: Second Metatarsal Stress Fracture (~2-3 min)
"A 22-year-old female runner presents with 3 weeks of gradually worsening pain in her midfoot. Pain started after increasing her weekly mileage from 20 to 40 miles. Examination shows point tenderness over the second metatarsal shaft. X-rays are normal. What is your assessment and management?"
Scenario 2: Fifth Metatarsal Zone 2-3 Stress Fracture (~3-4 min)
"A 19-year-old college basketball player presents with 6 weeks of pain at the base of his fifth metatarsal. He continued playing through the pain initially. Examination shows tenderness over MT5 base, pain with hop test. X-ray shows a fracture line at the metadiaphyseal junction extending into the 4-5 intermetatarsal articulation, with some medullary sclerosis. What is your assessment and management?"
Scenario 3: Recurrent Stress Fractures (~2-3 min)
"A 20-year-old female cross-country runner presents with her third metatarsal stress fracture in 18 months (previous MT2, MT3, now MT4). She has been compliant with activity modification each time. What is your approach?"
MCQ Practice Points
Most Common Site Question
Q: What is the most common site for metatarsal stress fractures? A: Second metatarsal (marching fracture) - most common site but has low nonunion risk with excellent prognosis using conservative treatment.
High-Risk Location Question
Q: Which metatarsal stress fracture location has the highest nonunion risk? A: Fifth metatarsal Zone 2-3 (metadiaphyseal junction and proximal diaphysis) - 50%+ nonunion rate with conservative treatment due to watershed blood supply. Athletes require surgical fixation.
Diagnosis Timing Question
Q: When do stress fractures become visible on X-ray after symptom onset? A: 2-3 weeks - X-rays are negative initially. MRI is gold standard for early diagnosis, showing changes within days of symptom onset.
Screw Size Question
Q: What is the minimum recommended screw diameter for MT5 Zone 2-3 stress fracture fixation? A: 5.5mm - Studies show better outcomes with larger screws (5.5-6.5mm) compared to 4.5mm. Screw size matters for reliable healing.
Return to Sport Question
Q: What is the typical return to sport timeline for MT5 Zone 2-3 stress fractures treated surgically? A: 8-10 weeks - Surgical fixation allows reliable healing and earlier return compared to conservative treatment (which has 50%+ nonunion risk and 15+ weeks if it fails).
Risk Factors Question
Q: What increases the risk of metatarsal stress fractures in female athletes? A: Female athlete triad (energy deficiency, amenorrhea, low BMD) increases risk 2-3x. Also training errors, nutrition, and biomechanical factors.
Australian Context and Medicolegal Considerations
Australian Sports Medicine
- Sports Medicine Australia: Guidelines for stress fracture management
- Return to sport protocols: Gradual progression, pain-free criteria
- Multidisciplinary teams: Sports physicians, physiotherapists, nutritionists
- Elite athlete support: AIS protocols for high-performance athletes
Medicolegal Considerations
- Documentation: Risk factor assessment, treatment rationale
- Counseling: Nonunion risk for high-risk sites (MT5 Zone 2-3)
- Informed consent: Surgical vs conservative options, outcomes
- Recurrence prevention: Documented risk factor management
Medicolegal Considerations
Key documentation requirements:
- Document risk factor assessment (training, nutrition, female athlete triad)
- Counsel about nonunion risk for MT5 Zone 2-3 (50%+ with conservative)
- Document treatment rationale (surgical vs conservative based on site and patient factors)
- Address underlying causes to prevent recurrence - document multidisciplinary referrals
METATARSAL STRESS FRACTURES
High-Yield Exam Summary
Key Anatomy
- •MT2 = most common site (marching fracture) - low risk, excellent prognosis
- •MT5 Zone 2-3 = HIGH RISK - watershed blood supply, 50%+ nonunion
- •Watershed zone = metadiaphyseal junction where nutrient artery meets periosteal supply
- •MT1 = moderate risk due to weight-bearing importance
Classification
- •Site-based: MT2 (low), MT1 (moderate), MT5 Zone 2-3 (HIGH)
- •Torg classification: Type I (acute), Type II (delayed with sclerosis), Type III (nonunion)
- •Severity: Grade I (MRI only), Grade II (periosteal reaction), Grade III (fracture line), Grade IV (displaced)
- •Zone classification (MT5): Zone 1 (tuberosity), Zone 2 (metaphyseal-diaphyseal), Zone 3 (proximal diaphysis)
Treatment Algorithm
- •Low-risk (MT2-4): Activity modification, CAM boot 4-6 weeks, excellent prognosis
- •High-risk (MT5 Zone 2-3): Surgical fixation (IM screw) in athletes, 50%+ nonunion with conservative
- •Torg Type II-III: Bone graft + screw fixation for sclerotic canal
- •Address risk factors: Training errors, nutrition, female athlete triad, biomechanics
Surgical Pearls
- •Entry point: Tip of MT5 tuberosity (not too medial)
- •Screw size: Minimum 5.5mm diameter (larger better outcomes)
- •Technique: Engage far cortex for compression
- •Bone graft: For Torg Type II-III (curettage + autograft)
Complications
- •Nonunion: 50%+ risk MT5 Zone 2-3 with conservative treatment
- •Delayed union: 10-20% all sites, address risk factors
- •Recurrence: 20-30% if underlying causes not addressed
- •Hardware issues: 5-10% with undersized screws or poor technique