Lisfranc Injuries: Miss it and Regret it

The Lisfranc joint complex (tarsometatarsal joint) is the "Keystone" of the midfoot. It provides the structural integrity for the longitudinal arch and transfers force from the midfoot to the forefoot during gait. Injuries to this complex are notorious for two reasons:

1. They are commonly missed (up to 20% in some series), often dismissed as "midfoot sprains."
2. The outcomes of missed injuries are poor, leading to rapid post-traumatic arthritis and chronic disability.

This guide covers the anatomy, subtle radiological signs, and the surgical algorithms required for FRACS.

Visual Element: An exploded view of the midfoot bones, highlighting the Lisfranc Ligament (running from Medial Cuneiform to 2nd Metatarsal Base) and the lack of a ligament between MT1 and MT2.

Anatomy: The Roman Arch

The stability of the midfoot relies on the "Roman Arch" configuration.

• Bony Stability: The base of the 2nd Metatarsal is recessed into a mortise formed by the medial, middle, and lateral cuneiforms. It is the "Keystone."
• Ligamentous Stability:
  • Lisfranc Ligament: The strongest ligament. Runs obliquely from the Medial Cuneiform (C1) to the Base of the 2nd Metatarsal (M2).
  • Intermetatarsal Ligaments: Connect the bases of the lesser metatarsals (2-5).
  • Crucial Fact: There is NO transverse ligament connecting the 1st and 2nd metatarsal bases. The Lisfranc ligament is the only structure preventing diastasis (separation) of the 1st and 2nd rays.

Diagnosis: High Index of Suspicion

Mechanism

• Direct: Crush injury (industrial accident).
• Indirect: Axial load on a plantarflexed foot (e.g., foot caught in stirrup, missing a step, sports tackle).

Clinical Signs

• Plantar Ecchymosis: If you see bruising on the sole of the foot in the arch, it is a Lisfranc injury until proven otherwise. This sign is pathognomonic.
• Midfoot Tenderness: Over the TMT joints.
• Provocative Tests: Pain with pronation/abduction of the forefoot.

Radiology

You need weight-bearing films. Non-weight-bearing films can miss 50% of unstable injuries because the arch recoils when unloaded.

The Checklist:

1. AP View: Medial border of 2nd MT should align with Medial border of Middle Cuneiform.
2. Oblique View: Medial border of 4th MT should align with Medial border of Cuboid.
3. Lateral View: Dorsal bony step-off ("Step-up" sign). Flattening of the arch.
4. The Fleck Sign: A tiny avulsion fracture in the space between the 1st and 2nd metatarsal bases. This represents avulsion of the Lisfranc ligament and is diagnostic of instability.

Visual Element: X-ray with overlays showing the alignment lines (AP and Oblique) and identifying the Fleck Sign.

Classification

Myerson Classification (Modified Hardcastle)

Used for high-energy injuries.

• Type A: Total incongruity (All metatarsals displace in one direction).
• Type B: Partial incongruity.
  • B1: Medial displacement (1st ray only).
  • B2: Lateral displacement (Lesser rays).
• Type C: Divergent (1st ray goes medial, lesser rays go lateral).

Nunley-Vertullo Classification

Used for subtle, low-energy athletic injuries (Sprains).

• Stage 1: Pain, non-displaced on X-ray, positive bone scan/MRI. (Stable).
• Stage 2: Diastasis 2-5mm. Lisfranc ligament ruptured. (Unstable).
• Stage 3: Diastasis > 5mm + Loss of arch height. (Frank rupture/Dislocation).

Treatment Algorithm

Non-Operative

• Indication: Nunley Stage 1 (Stable sprain). No displacement on weight-bearing views.
• Protocol: Non-weight bearing cast/boot for 6 weeks. High risk of displacement, needs close X-ray monitoring.

Operative: The Great Debate (ORIF vs Fusion)

1. Open Reduction Internal Fixation (ORIF)

• Philosophy: Restore anatomy, let ligaments heal, remove metal later to restore motion.
• Technique:
  • Incisions: Dorsomedial (1st/2nd ray) and Dorsolateral (3rd/4th ray).
  • Dorsal Bridge Plating: The modern preference. Plates span the joint. Advantage: Does not damage articular cartilage. More stable than screws.
  • Trans-articular Screws: The traditional method. Screws go through the joint. Advantage: Compression. Disadvantage: Cartilage damage.

2. Primary Arthrodesis (Fusion)

• Philosophy: Ligaments heal with scar (creep). Even perfect ORIF often leads to arthritis. Fusion solves the problem once and for all.
• Evidence: The Ly and Coetzee study (JBJS 2006) was a landmark RCT showing Primary Fusion had better functional outcomes and fewer revision surgeries than ORIF for purely ligamentous injuries.
• Indication: Purely ligamentous injuries, severe comminution, delayed presentation, or older patients.
• Which joints? Fuse the Medial (1st) and Middle (2nd/3rd) columns. NEVER fuse the Lateral (4th/5th) column (it needs mobility for gait). Fix the 4th/5th with K-wires only.

Visual Element: Side-by-side intra-operative X-rays showing Bridge Plating vs Screw Fixation.

Rehabilitation

• 0-2 Weeks: NWB Splint. Elevation.
• 2-6 Weeks: NWB Cast/Boot.
• 6-12 Weeks: Progressive weight bearing in boot.
• 3-6 Months: Hardware removal (if ORIF) usually required before return to impact sports (screws will break).
• Outcomes: Even with perfect treatment, many patients have some residual stiffness and difficulty with sprinting.

Summary

• Suspect it: Plantar bruising.
• Stress it: Weight-bearing X-rays or CT.
• Fix it: Stable fixation is mandatory for displacement.
• Fuse it: Consider fusion for ligamentous injuries.

Related Topics:

• Midfoot Arthritis
• Jones Fracture (5th Metatarsal)
• Compartment Syndrome of the Foot