Pseudo-Jones Fractures (Fifth Metatarsal Tuberosity Avulsion)

Location: Styloid process/tuberosity - PROXIMAL to 4-5 intermetatarsal joint

Mechanism: Inversion injury with avulsion by peroneus brevis or lateral plantar fascia

Blood Supply: Excellent (metaphyseal bone)

Prognosis:

• Union rate over 95% with conservative treatment
• Nonunion under 5%
• Excellent functional outcomes

Treatment: Conservative - CAM boot or hard-soled shoe, WBAT, 4-6 weeks

Stewart Subclassification:

• Type 1: Small flake avulsion (fragment under 5mm) - most common
• Type 2: Large fragment avulsion (fragment over 5mm)
• Type 3: Comminuted tuberosity fracture - may extend to cuboid articulation

Location: Metadiaphyseal junction - fracture extends INTO 4-5 intermetatarsal joint

Mechanism: Adduction force to forefoot with foot plantarflexed

Blood Supply: Poor (watershed zone where nutrient artery meets periosteal vessels)

Prognosis:

• Union rate 50-75% with conservative treatment
• Nonunion 25-50%
• Delayed union common

Treatment:

• Conservative: 6-8 weeks NWB in cast, prolonged immobilization
• Surgical: IM screw fixation (preferred for athletes)
• Return to activity: 12-20 weeks

Location: Proximal diaphysis - DISTAL to 4-5 intermetatarsal joint

Mechanism: Repetitive stress, often in athletes (basketball, tennis)

Blood Supply: Limited periosteal vessels only

Prognosis:

• High risk of delayed union or nonunion
• Refracture risk with conservative treatment

Treatment:

• Usually surgical - IM screw fixation
• Conservative treatment has high failure rate
• Return to activity: 10-16 weeks with surgery

Non-Operative Treatment - First Line for Zone 1

Indications:

• All non-displaced or minimally displaced Zone 1 fractures
• Displaced fractures not involving articular surface significantly
• Most Type 1 and Type 2 fractures (over 95% of cases)

Protocol Options:

CAM Boot (Most Common):

• Weight-bearing as tolerated from day 1
• Duration: 4-6 weeks
• Transition to supportive shoe when comfortable
• No routine follow-up X-rays if progressing well

Hard-Soled Shoe (Minor Fractures):

• For very small avulsions with minimal symptoms
• Weight-bearing as tolerated
• Duration: 3-4 weeks
• May be sufficient for small flake fractures

Initial NWB Protocol (Severe Pain):

• 1-2 weeks non-weight-bearing with crutches
• Then progress to CAM boot with WBAT
• Reserved for patients with severe pain on initial weight-bearing

Expected Outcomes:

• Union rate over 95%
• Return to full activity: 6-8 weeks
• Fibrous union common but asymptomatic

Surgical Treatment - Reserved for Select Cases

Indications (Less than 5% of Cases):

• Displaced fracture with over 2mm articular step-off (Type 3 with joint involvement)
• Symptomatic nonunion after adequate conservative trial
• Large displaced fragment in high-demand athlete (controversial - no strong evidence)

Surgical Options:

ORIF with Screw Fixation:

• 3.5mm or 4.0mm cortical screw
• Lag screw technique
• Fragment must be large enough to accept fixation

Tension Band Technique:

• For larger tuberosity fragments
• K-wires and tension band wire
• Provides compression across fracture

Fragment Excision:

• For small symptomatic fragments
• Only if fragment too small for fixation
• Rarely affects peroneus brevis function

Indications for Surgery

• Type 3 comminuted fracture with over 2mm intra-articular step-off
• Symptomatic nonunion (under 2% of cases)
• Failed conservative treatment with persistent symptoms

Preoperative Planning

• CT scan to assess fragment size and joint involvement
• Ensure fragment is large enough for screw fixation
• Consider fragment excision if too small

Surgical Approach

Positioning:

• Supine on operating table
• Bump under ipsilateral hip
• Tourniquet on thigh

Incision:

• Longitudinal incision over lateral aspect of 5th metatarsal base
• 4-5cm centered over tuberosity
• Identify and protect sural nerve and branches

Surgical Steps

Step 1 - Exposure:

• Incise skin and subcutaneous tissue
• Identify peroneus brevis tendon insertion
• Develop interval between tendon and bone

Step 2 - Fragment Preparation:

• Clear soft tissue from fracture site
• Remove fibrous tissue from fracture ends
• Reduce fragment anatomically
• Use pointed reduction clamp to hold

Step 3 - Fixation:

• Insert guidewire across fracture
• Measure screw length
• Drill and tap
• Insert 3.5mm or 4.0mm cortical screw with washer
• Achieve interfragmentary compression

Step 4 - Closure:

• Irrigate wound
• Repair peroneus brevis if disturbed
• Close in layers
• Apply well-padded below-knee splint

Alternative Technique - Tension Band

For Large Tuberosity Fragments:

• Insert two parallel K-wires across fracture
• Apply figure-of-8 tension band wire
• Bend and cut K-wires
• Provides excellent compression

Advantages:

• Excellent compression across fracture
• Good for larger fragments
• Dynamic compression with loading

Postoperative Protocol:

• See Postoperative Care section below

Potential Complications

Nonunion (Under 5%)

Fibrous Union:

• Radiographic nonunion but asymptomatic
• Occurs in up to 30% of cases
• Does NOT require treatment if painless
• Provides adequate functional stability

Symptomatic Nonunion (Under 2%):

• Persistent pain with activity
• Tenderness over fracture site
• Pain with peroneal muscle contraction

Management:

• Conservative trial first (extend immobilization)
• Surgical options: ORIF with bone graft or fragment excision
• Excellent results with surgery if truly symptomatic

Malunion

Description:

• Healing in displaced position
• Usually asymptomatic
• Rarely affects function

Management:

• Observation if asymptomatic
• Surgery rarely needed

Hardware Complications (If ORIF Performed)

Screw Prominence:

• Irritation of peroneus brevis tendon
• Painful over lateral foot
• May require hardware removal

Hardware Failure:

• Screw breakage (rare)
• Loss of fixation
• Usually occurs with inadequate fragment size

Sural Nerve Injury

Incidence:

• 2-5% with surgical approach
• Temporary dysesthesia common
• Permanent numbness rare

Prevention:

• Careful surgical dissection
• Identify and protect sural nerve branches

Peroneus Brevis Pathology

Tendon Injury:

• Rare with conservative treatment
• Can occur with surgical dissection
• Chronic irritation from hardware

Weakness:

• Transient weakness common after injury
• Resolves with rehabilitation
• Persistent weakness rare (under 5%)

Complex Regional Pain Syndrome

Incidence:

• Rare (under 1%)
• More common with prolonged immobilization

Presentation:

• Disproportionate pain
• Swelling, skin changes
• Allodynia, vasomotor changes

Management:

• Early mobilization
• Physical therapy
• Pain management referral

Refracture

Incidence:

• Very rare with Zone 1 fractures (under 1%)
• More common with premature return to activity

Prevention:

• Adequate healing time (6-8 weeks minimum)
• Progressive return to activity
• Gradual increase in loading

Post-ORIF Rehabilitation Protocol

Immediate Postoperative (Weeks 0-2)

Immobilization:

• Below-knee splint or cast
• Non-weight-bearing with crutches
• Elevate foot above heart level
• Ice therapy

Wound Care:

• First dressing change at 48 hours
• Monitor for infection, swelling
• Sutures removed at 10-14 days

Goals:

• Pain control
• Reduce swelling
• Protect fixation

Early Mobilization (Weeks 2-6)

Weeks 2-4:

• Transition to CAM boot at 2 weeks
• Begin partial weight-bearing (25-50%)
• Gentle ankle ROM exercises (non-resistance)
• Continue elevation and ice

Weeks 4-6:

• Progress to full weight-bearing in boot
• Active ROM exercises
• Begin light strengthening (theraband)
• Clinical and radiographic assessment at 6 weeks

Radiographic Monitoring:

• X-ray at 2 weeks (check hardware position)
• X-ray at 6 weeks (assess healing)
• Further imaging only if symptomatic

Advanced Rehabilitation (Weeks 6-12)

Weeks 6-8:

• Transition out of boot if healing progresses
• Progress to supportive athletic shoe
• Progressive weight-bearing exercises
• Balance and proprioception training
• Initiate impact activities (walking program)

Weeks 8-12:

• Sport-specific rehabilitation
• Plyometric exercises if athlete
• Running progression
• Agility drills

Return to Sport:

• 10-12 weeks for full contact sports
• Must demonstrate full ROM, strength
• No pain with activity
• Clearance from surgeon

Weight-Bearing Progression

Complications to Monitor

Early (0-2 weeks):

• Wound infection
• Compartment syndrome (rare)
• DVT (rare)

Delayed (2-6 weeks):

• Fixation failure
• Delayed union
• Sural nerve symptoms

Late (6+ weeks):

• Hardware prominence/irritation
• Chronic pain
• Stiffness

Hardware Removal

Indications:

• Symptomatic hardware (irritation)
• Patient preference after healing
• Peroneal tendon irritation

Timing:

• Minimum 6-9 months after surgery
• Only if fracture fully healed
• Not routinely required

High-Yield Exam Facts

Classification Must-Knows

1. The 4-5 intermetatarsal articulation is the critical landmark:

   • Zone 1: PROXIMAL to this joint
   • Zone 2: Extends INTO this joint
   • Zone 3: DISTAL to this joint

2. Zone 1 accounts for 93% of proximal fifth metatarsal fractures - it's the most common pattern.

3. Terminology confusion:

   • "Pseudo-Jones" = Zone 1 (NOT a true Jones fracture)
   • "True Jones" = Zone 2
   • Don't confuse them on exams

Mechanism Differentiation

4. Zone 1 mechanism: Inversion with plantarflexion (ankle sprain mechanism) causing avulsion by peroneus brevis

5. Zone 2 mechanism: Adduction force to forefoot - different from Zone 1

6. Avulsion structures: Peroneus brevis (dorsolateral) or lateral band of plantar fascia (plantar)

Blood Supply and Healing

7. Zone 1 has excellent blood supply - metaphyseal bone with abundant periosteal and medullary vessels

8. Zone 2 is a watershed zone - where nutrient artery meets periosteal supply = poor healing

9. This vascular difference explains the nonunion rates:

   • Zone 1: Under 5%
   • Zone 2: 25-50%

Treatment Principles

10. Over 95% of Zone 1 fractures heal with conservative treatment - this is the key point

11. Standard treatment: CAM boot, weight-bearing as tolerated, 4-6 weeks

12. Surgery is indicated in less than 5% of Zone 1 fractures:

    • Over 2mm intra-articular step-off
    • Symptomatic nonunion (rare)
    • NOT indicated for routine Zone 1 fractures

13. Fibrous union is common (up to 30%) but asymptomatic - NOT an indication for surgery

Common Exam Traps

14. TRAP: Assuming all proximal 5th metatarsal fractures need surgery

    • CORRECT: Zone 1 is conservative, Zone 2/3 consider surgery

15. TRAP: Treating radiographic fibrous union with surgery

    • CORRECT: Only treat symptomatic nonunion (under 2% incidence)

16. TRAP: Confusing Zone 1 location

    • CORRECT: Zone 1 is PROXIMAL to 4-5 joint, not INTO the joint

17. TRAP: Ordering routine follow-up X-rays

    • CORRECT: Only needed if symptoms not improving

Differential Diagnosis Pearls

18. Os vesalianum: Smooth corticated margins, may be bilateral, doesn't "fit" with adjacent bone

19. Acute fracture: Irregular margins, fits with adjacent bone, acute tenderness

20. Associated injuries to check: Lateral ankle ligaments (ATFL, CFL), peroneal tendons, anterior process of calcaneus

Return to Activity

21. Conservative treatment return to activity: 6-8 weeks (faster than Zone 2)

22. Surgical treatment return to activity: 10-12 weeks (slower than conservative!)

23. This is why conservative treatment is preferred - better outcomes, faster recovery

Key Numbers to Memorize

• 93% - Percentage of proximal MT5 fractures that are Zone 1
• Over 95% - Union rate with conservative treatment
• Under 5% - Nonunion rate for Zone 1
• 4-6 weeks - Duration of CAM boot treatment
• 6-8 weeks - Return to full activity
• 30% - Incidence of asymptomatic fibrous union
• Under 2% - Symptomatic nonunion requiring surgery