42.2 Metatarsal, Clavicle & Common Lower Extremity Fractures

Proximal 5th Metatarsal Fractures: Anatomical Zones & Vascular Watersheds

Fractures of the fifth metatarsal represent the most common metatarsal fractures encountered in primary care and sports medicine clinics, accounting for over 60% of all foot fractures. Clinical management and healing prognosis are entirely governed by the Lawrence and Botte classification, which divides the proximal fifth metatarsal into three distinct anatomical zones based on vascular perfusion patterns.

                 PROXIMAL 5TH METATARSAL ANATOMICAL ZONES

          ┌──────────────────────────────────────────────────┐
          │   ZONE 1: Pseudo-Jones (Tuberosity Avulsion)     │
          │   • >90% of proximal 5th metatarsal fractures    │
          │   • Extra-articular or into cuboid joint         │
          │   • Rich cancellous blood supply ──► HEALS RAPID │
          ├──────────────────────────────────────────────────┤
          │   ZONE 2: True Jones Fracture                    │
          │   • Metaphyseal-diaphyseal junction (1.5 cm)     │
          │   • Enters 4th-5th intermetatarsal articulation  │
          │   • VASCULAR WATERSHED ──► High Nonunion (15-30%)│
          ├──────────────────────────────────────────────────┤
          │   ZONE 3: Diaphyseal Stress Fracture             │
          │   • Distal to 4th-5th intermetatarsal joint      │
          │   • Overuse in athletes / runners                │
          │   • Prodromal pain, cortical sclerosis           │
          └──────────────────────────────────────────────────┘

1. Zone 1: Pseudo-Jones Fracture (Tuberosity Avulsion)

• Anatomy & Mechanism: Represents >90% of proximal 5th metatarsal fractures. Occurs when the foot is subjected to sudden, forceful inversion while plantarflexed. Historically attributed to avulsion by the peroneus brevis tendon, anatomical and biomechanical studies have conclusively demonstrated that the vast majority of these avulsions are driven by the lateral cord of the plantar aponeurosis.
• Vascularity & Prognosis: The metatarsal tuberosity features an exceptionally rich cancellous blood supply derived from metaphyseal perforators. As a result, nonunion is exceedingly rare (<1%).
• Treatment Protocol:
  • Fully conservative management.
  • Symptomatic weight-bearing as tolerated in a rigid-soled post-operative shoe or a short pneumatic walking boot.
  • Transition to supportive athletic sneakers as pain diminishes over 3 to 6 weeks.
  • Non-weight-bearing casting is strictly unnecessary and produces avoidable calf atrophy, joint stiffness, and deep vein thrombosis (DVT) risk.

2. Zone 2: True Jones Fracture

• Anatomy & Definition: First described by Sir Robert Jones in 1902. A transverse fracture occurring at the metaphyseal-diaphyseal junction, precisely within 1.5 cm distal to the tuberosity. Crucially, the fracture line extends into the 4th-5th intermetatarsal articulation, NOT the cuboid-metatarsal joint.
• Mechanism: Sudden, forceful adduction or inversion load applied to the forefoot while the heel is elevated (e.g., pivoting or cutting maneuvers in basketball, soccer, or dance).
• The Vascular Watershed Trap: The metaphyseal-diaphyseal junction represents a critical vascular watershed. The endosteal nutrient artery enters the middle third of the diaphyseal cortex and arborizes proximally, terminating prior to reaching the metaphyseal-diaphyseal border. Consequently, Zone 2 fractures suffer from severe relative ischemia, resulting in delayed union in 30% to 50% and primary nonunion in 15% to 25% of cases if managed with early weight-bearing.
• Management Guidelines:
  • Sedentary / Low-Demand Patients: Strict non-weight-bearing short-leg cast for 6 to 8 weeks, verified by serial radiographic evidence of progressive bridging callus prior to weight advancement.
  • Competitive Athletes & Active Manual Laborers: Early orthopedic referral for percutaneous intramedullary cannulated screw fixation. Operative stabilization achieves union rates >95%, slashes time to union in half, and permits safe return to competitive athletics within 6 to 8 weeks, compared to high refracture rates associated with prolonged casting.

3. Zone 3: Proximal Diaphyseal Stress Fracture

• Anatomy & Mechanism: Located in the proximal diaphysis distal to the 4th-5th intermetatarsal junction. These represent true chronic overuse stress fractures resulting from repetitive cyclical mechanical overload in long-distance runners, military recruits, and basketball players.
• Radiographic Features: Often demonstrate a history of chronic prodromal lateral foot pain. Radiographs reveal focal periosteal reaction, external cortical thickening, or medullary canal sclerosis narrowing the marrow cavity adjacent to a radiolucent fracture line (Torg classification Type II or III).
• Management: Zone 3 stress fractures carry the highest rate of nonunion among all foot fractures. Management requires prolonged non-weight-bearing cast immobilization (12 to 20 weeks) or, much more commonly, surgical intramedullary screw fixation with or without open autologous bone grafting.

Proximal 5th Metatarsal Fracture Classification & Management Comparison

---

Lisfranc Joint Injury (Tarsometatarsal Complex)

The Lisfranc joint complex comprises the articulations between the midfoot (the three cuneiforms and cuboid) and the forefoot (bases of the five metatarsals). The second metatarsal base is deeply recessed proximally between the medial and lateral cuneiforms, forming an osseous "keystone" mortise that provides intrinsic transverse stability.

The Lisfranc Ligament

The Lisfranc ligament is a massive, oblique intra-articular ligament running from the plantar-lateral surface of the medial cuneiform to the plantar-medial base of the second metatarsal. Crucially, while strong transverse ligaments interconnect the bases of the 2nd through 5th metatarsals, there is NO transverse ligament connecting the 1st and 2nd metatarsal bases. Stability of the entire medial midfoot column depends entirely on the integrity of the Lisfranc ligament.

Mechanism of Injury & Clinical Presentation

• Mechanisms: High-energy motor vehicle collisions (foot slammed against floorboard/brake) or low-energy athletic axial loading (an athlete falling forward over an opponent with the foot held in extreme hyperplantarflexion, causing the 2nd metatarsal base to rupture dorsally out of its keystone socket).
• Clinical Presentation: Severe midfoot pain, gross dorsal midfoot edema, inability to bear weight on the heel or toes, and exquisite point tenderness along the tarsometatarsal line.
• PATHOGNOMONIC PHYSICAL SIGN: Plantar midfoot ecchymosis ("Lisfranc sign"). Blood extravasates through the ruptured inferior plantar capsule into the deep plantar vault. Clinical axiom: In acute foot trauma, plantar ecchymosis is pathognomonic for a Lisfranc injury until proven otherwise!
• Provocative Examination: The Midfoot Stress Test: Grasp the hindfoot (calcaneus) firmly with one hand while using the other hand to passively pronate and abduct the forefoot. Severe midfoot pain or palpable instability confirms ligamentous disruption.

Radiographic Diagnostic Criteria

[!IMPORTANT] THE CRITICAL LISFRANC IMAGING PROTOCOL

• Standard non-weight-bearing foot radiographs miss up to 20% to 50% of subtle ligamentous Lisfranc disruptions!
• When clinical suspicion is present, Bilateral Weight-Bearing Plain Radiographs (AP, lateral, and 30° oblique) are mandatory.
• Four Cardinal Radiographic Signs of Lisfranc Disruption:
  1. Widening >2 mm between the 1st and 2nd metatarsal bases on the weight-bearing AP view.
  2. Loss of Colinear Alignment: On the AP view, the medial border of the 2nd metatarsal base must align continuously with the medial border of the intermediate cuneiform. Lateral step-off >1 mm indicates subluxation.
  3. Oblique View Step-off: The medial border of the 4th metatarsal base must align precisely with the medial border of the cuboid.
  4. The "Fleck Sign": A pathognomonic small avulsion bone fragment visible within the 1st-2nd intermetatarsal space, reflecting bony avulsion of the Lisfranc ligament attachment.

                      LISFRANC JOINT RADIOGRAPHIC ALIGNMENT

     Normal AP Alignment                    Lisfranc Disruption (>2 mm Diastasis)
  ─────────────────────────────             ──────────────────────────────────────
      [Medial]    [Middle]                      [Medial]            [Middle]
     Cuneiform   Cuneiform                     Cuneiform           Cuneiform
         │           │                             │                   │
         │           │                             │     ►► GAP ◄◄     │
         ▼           ▼                             ▼    [>2 mm Fleck]  ▼
      [1st MT]    [2nd MT]                      [1st MT]            [2nd MT]
     (Colinear medial borders)                  (Lateral displacement / subluxation)

Management Guidelines

• True Non-Displaced (<2 mm diastasis on weight-bearing views): Strict non-weight-bearing short-leg cast for 6 weeks, followed by repeat weight-bearing radiographs. If alignment remains pristine, transition to a walking boot with custom rigid orthotic arch support.
• Displaced (>2 mm diastasis or any articular step-off): Urgent orthopedic surgical referral for operative reduction and internal fixation (ORIF) using trans-articular cortical screws or primary arthrodesis. Missed or improperly managed Lisfranc injuries lead to progressive longitudinal arch collapse (post-traumatic flatfoot), chronic neuropathic pain, and severe, irreversible midfoot degenerative osteoarthritis.

---

Clavicle Fractures & Allman Classification

Clavicle fractures account for 2% to 5% of all adult fractures and up to 10% to 15% of all pediatric fractures, resulting from direct impacts to the lateral shoulder during athletic collisions, falls from bicycles, or motor vehicle crashes.

Allman Classification System

• Group I: Middle Third / Midshaft (80% of clavicle fractures):
  • Occurs at the transition between the middle and lateral thirds, where the cross-sectional diameter is thinnest and lacks stabilizing muscular or ligamentous attachments.
  • The sternocleidomastoid muscle displaces the proximal medial fragment superiorly and posteriorly, while the weight of the arm and pectoralis major pull the distal lateral fragment inferiorly and medially.
• Group II: Distal / Lateral Third (15% of clavicle fractures):
  • Subclassified by Neer based on the relationship to the coracoclavicular (CC) ligaments (conoid and trapezoid):
    • Type I: CC ligaments intact; minimally displaced; stable.
    • Type II: CC ligaments detached from the medial fragment (Type IIA: conoid and trapezoid intact but medial to fracture; Type IIB: conoid torn, trapezoid intact). Significant superior displacement of the medial fragment; high nonunion rate (up to 30%); frequently requires surgical reconstruction.
    • Type III: Intra-articular fracture entering the acromioclavicular (AC) joint; managed conservatively unless symptomatic AC arthritis develops.
• Group III: Proximal / Medial Third (5% of clavicle fractures):
  • High-energy trauma. Requires meticulous physical and CT evaluation to exclude posterior sternoclavicular dislocation and catastrophic mediastinal vascular injury (subclavian vessels, carotid artery, internal jugular vein) or pneumothorax.

Management: Non-Operative vs. Surgical ORIF

                    MIDSHAFT CLAVICLE MANAGEMENT PROTOCOL

    [Midshaft Clavicle Fracture Confirmed on Upright AP / 15° Cephalic Views]
                                │
             ┌──────────────────┴──────────────────┐
             ▼                                     ▼
    [SURGICAL ORIF INDICATIONS]           [CONSERVATIVE MANAGEMENT CANDIDATE]
    • Open fracture                       • Non-displaced or minimally displaced
    • Neurovascular compromise            • Cortical contact maintained
    • Severe skin tenting / blanching     • Shortening <2 cm (males) / <1.5 cm (females)
    • 100% displacement (no contact)            │
    • Shortening >2 cm                          ▼
    • "Floating shoulder" (scapula neck)  [SIMPLE SLING FOR 4-6 WEEKS]
             │                            • Simple sling = Figure-of-8 (less skin breakdown)
             ▼                            • Gentle pendulum exercises at 2-3 weeks
    [ORTHOPEDIC SURGICAL REFERRAL]        • Progressive active rehab at 4-6 weeks
    • Precontoured superior plate ORIF    • Contact sports restricted until 8-12 weeks

• Non-Operative Protocol: First-line standard of care for non-displaced or minimally displaced midshaft fractures. Randomized trials have conclusively proven that a simple sling provides equivalent clinical union rates, fewer cosmetic/skin complications, and substantially higher patient satisfaction compared to uncomfortable figure-of-eight braces.
• Indications for Surgical ORIF (Superior or Anterior-Inferior Plating):
  • Absolute: Open fractures; acute neurovascular compromise (brachial plexus deficit or diminished distal pulses); severe skin tenting threatening impending ischemic necrosis; "floating shoulder" (ipsilateral clavicle fracture and scapular neck fracture).
  • Relative: Complete displacement with 100% loss of cortical contact; fracture shortening >2 cm in males or >1.5 cm in females (shortening alters scapulothoracic kinematics, decreasing shoulder abduction endurance by up to 20%); symptomatic nonunion after 3 to 6 months.

---

Proximal Fibula Fractures & The Maisonneuve Injury

A Maisonneuve fracture is an unstable pronation-external rotation injury of the lower extremity comprising a rupture of the medial ankle stabilizers associated with a high fracture of the proximal fibula.

                      MAISONNEUVE INJURY KINEMATICS

              1. Violent External Rotation Force at Ankle
                                 │
                                 ▼
              2. Medial Failure: Deltoid Ligament Tear
                 OR Medial Malleolus Avulsion Fracture
                                 │
                                 ▼
              3. Syndesmotic Disruption: AITFL & PITFL Tear;
                 Interosseous Membrane Tears Proximalward
                                 │
                                 ▼
              4. Kinetic Energy Exits Proximally:
                 SPIRAL FRACTURE OF PROXIMAL FIBULAR NECK!

[!CAUTION] THE GOLDEN RULE OF ANKLE TRAUMA: PALPATE THE PROXIMAL FIBULA!

• The Diagnostic Hazard: Patients with a Maisonneuve fracture present complaining exclusively of severe medial ankle pain and swelling. Because the proximal fibular fracture is remote from the ankle and often painless at rest, clinicians who fail to examine the entire leg will misdiagnose this catastrophic injury as an "isolated deltoid ligament sprain" or "isolated medial malleolus fracture"!
• Mandatory Physical Examination: In EVERY patient presenting with an ankle injury—especially those with medial clear space widening, medial tenderness, or syndesmotic pain—the clinician must palpate the proximal fibular head and neck along its entire length.
• Radiographic Protocol: If proximal fibular tenderness is elicited, or if ankle mortise views demonstrate medial clear space widening >4 mm or tibiofibular clear space >6 mm, order Full-Length Anteroposterior and Lateral Tibia-Fibula Radiographs.
• Definitive Treatment: The Maisonneuve fracture represents a complete disruption of the distal tibiofibular syndesmosis. Closed casting is strictly contraindicated due to high failure rates. Treatment is urgent orthopedic referral for surgical syndesmotic fixation using syndesmotic screws or dynamic suture-button constructs (TightRope).

---

Phalanx (Toe) Fractures: Lesser Toes vs. Great Toe

Toe fractures are ubiquitous in ambulatory primary care, typically resulting from direct axial impact ("stubbing" a bare toe against furniture) or crush trauma from dropped heavy objects.

Lesser Toe Fractures (Digits 2 through 5)

• Diagnostic Approach: Obtain 3-view plain radiographs (AP, lateral, oblique) to assess displacement, intra-articular extension, and rotational deformity.
• Management Protocol:
  • Non-displaced or minimally displaced lesser toe fractures are managed conservatively with buddy taping to the adjacent uninjured toe for 3 to 4 weeks.
  • Technique: Place a small piece of gauze or cotton in the interdigital web space between the toes prior to applying tape to prevent moisture accumulation, maceration, and skin breakdown.
  • Provide a stiff-soled post-operative shoe to prevent painful metatarsophalangeal extension during walking.
  • Grossly displaced or angulated fractures: Perform a digital nerve block (1% to 2% plain lidocaine), apply gentle manual axial traction to reduce the deformity, and buddy tape.

Great Toe (Hallux) Fractures

• Biomechanical Significance: The hallux bears over 50% of total body weight during the terminal push-off phase of the normal gait cycle. Malunion of the great toe causes severe gait alterations, metatarsalgia, and debilitating post-traumatic arthritis.
• Orthopedic Surgical Referral Indications:
  • Intra-articular fracture involving >25% of the first metatarsophalangeal (MTP) or interphalangeal (IP) articular surface.
  • Fracture displacement >2 mm after closed reduction attempt.
  • Irreducible fracture or significant rotational malalignment.
  • Open fractures or comminuted intra-articular sesamoid fractures.
• Conservative Protocol: Truly non-displaced extra-articular hallux fractures are immobilized in a short-leg walking boot with a rigid toe plate extension (or toe spica) for 4 to 6 weeks, with heel-weight-bearing initially.