Hardcastle–Myerson — Lisfranc Injuries

Overview — Lisfranc Injuries

Lisfranc injuries encompass a spectrum of fractures and fracture-dislocations at the tarsometatarsal (TMT) joint complex — the articulation between the cuneiforms and cuboid proximally and the bases of the five metatarsals distally, named after Jacques Lisfranc de Saint-Martin (19th-century French surgeon). These injuries are notorious for being missed in the acute setting (up to 40% are initially undiagnosed) and for causing severe long-term disability if not adequately treated. They range from purely ligamentous sprains (`Lisfranc sprain` — the `worst ankle sprain that isn`t`) to complete fracture-dislocations of the entire midfoot. The Hardcastle-Myerson classification remains the most widely used system, guiding surgical decision-making based on the direction and completeness of midfoot displacement.

The Lisfranc ligament: the key stabiliser of the TMT joint complex; the true Lisfranc ligament runs from the medial cuneiform to the base of the 2nd metatarsal — it is the strongest ligament in the TMT complex; there is NO direct ligamentous connection between the 1st and 2nd metatarsal bases (a unique `gap` at the base of the 2nd MT); the 2nd metatarsal base is `keystone-like` — it is recessed proximally between the medial and lateral cuneiforms, locked in by bony walls on both sides; the stability of the entire TMT complex depends on: (1) the bony `lock` of the 2nd MT base, and (2) the Lisfranc ligament connecting the medial cuneiform to the 2nd MT base; disruption of either leads to progressive instability of the entire TMT complex
Mechanism: low-energy (most commonly) — indirect axial loading through the forefoot in a plantarflexed position (falling from a height onto the toes, motor vehicle accidents with the foot on the brake pedal, sports injuries — midfield tackles in football); high-energy — direct crushing force on the dorsum of the foot; the low-energy mechanism is why these injuries are commonly missed — there may be minimal swelling and the patient walks in the ED; associated metatarsal base fractures are common (the `nutcracker` mechanism — the 2nd MT base is fractured by the compression force)

Hardcastle Classification (Modified by Myerson)

Type	Hardcastle Description	Myerson Subtype	X-Ray / CT Features	Treatment
Type A — Total incongruity	ALL FIVE metatarsals are displaced from their corresponding tarsal bones in the SAME direction; the entire TMT complex is disrupted; the displacement is UNIFORM — all 5 metatarsals move together as a unit	No subtype — all 5 metatarsals displaced in the same direction	All 5 TMT joints are incongruent in the same direction; the most commonly lateral displacement of all 5 metatarsals; on the AP view, the medial borders of the 1st-5th metatarsals are all displaced relative to their corresponding cuneiforms/cuboid; often associated with 2nd MT base fracture (`fleck sign`)	ORIF — all 5 metatarsals require reduction and fixation; medial column (1st-3rd MT) fixation with screws; lateral column (4th-5th MT) fixation with K-wires (allows some residual motion in the 4th-5th TMT — these joints have intrinsic mobility that is important to preserve)
Type B — Partial incongruity	SOME but NOT ALL metatarsals are displaced; the displacement is PARTIAL — part of the TMT complex is disrupted and part is intact; two subtypes based on which metatarsals are displaced	B1 (medial) — 1st metatarsal is displaced medially and/or dorsally in isolation (the first TMT joint is disrupted, the 2nd-5th are intact); B2 (lateral) — one or more of the lateral metatarsals (2nd-5th) are displaced; the most common form of Lisfranc partial displacement	B1: the 1st MT is displaced medially/dorsally on the medial cuneiform; the medial cuneiform-1st MT joint is widened; this is often a ligamentous injury without a bony fracture; B2: widening between the 1st and 2nd MT bases on the AP view; the 2nd MT base is displaced laterally; associated 2nd MT base fracture (`nutcracker` 2nd MT fracture) is common	Operative for any displacement >2 mm; B1 — 1st TMT screw fixation; B2 — screws for 2nd and 3rd TMT + K-wires for 4th and 5th; purely ligamentous Lisfranc injuries (no bony fracture) may be managed with primary arthrodesis rather than ORIF (higher non-operative failure rate for purely ligamentous injuries)
Type C — Divergent	DIVERGENT displacement — the metatarsals are displaced in DIFFERENT directions; the 1st metatarsal is displaced MEDIALLY while the 2nd-5th metatarsals are displaced LATERALLY (or in another direction away from the 1st); the classic `opening` pattern; the midfoot is split between medial and lateral components moving in opposite directions	C1 (partial divergent) — 1st MT medial + some lateral MTs lateral; C2 (total divergent) — 1st MT medial + ALL lateral MTs (2nd-5th) displaced laterally; the classic `full split` of the midfoot	The classic `divergent Lisfranc` dislocation on the AP pelvis: the 1st MT diverges medially while the 2nd-5th diverge laterally; the gap between the 1st and 2nd MT bases is dramatically widened; often associated with multiple metatarsal base fractures; this is the most dramatic and most obviously displaced pattern; cannot be missed on a weight-bearing AP foot X-ray	ORIF or primary arthrodesis (depending on bony vs ligamentous injury and degree of displacement); medial column (1st-3rd TMT) — screws (rigid fixation); lateral column (4th-5th TMT) — K-wires; the dorsomedial approach + lateral approach for dual-column access; or single extensile dorsal approach; the medial column must achieve rigid fixation; perfect anatomical reduction is mandatory for good outcomes

Diagnosis — The Subtlety Challenge

Plain X-ray assessment: on a WEIGHT-BEARING AP foot X-ray (the most important diagnostic view): (1) the medial border of the 2nd metatarsal should be collinear with the medial border of the middle cuneiform; (2) the medial border of the 1st MT should be collinear with the medial border of the medial cuneiform; (3) the medial border of the 4th MT should be collinear with the medial border of the cuboid; ANY disruption of these three relationships = Lisfranc injury until proven otherwise; the `fleck sign` — a small avulsion fracture from the base of the 2nd metatarsal (avulsion of the Lisfranc ligament from its metatarsal attachment) — is pathognomonic of a Lisfranc injury even in the absence of gross displacement; weight-bearing films are essential (non-weight-bearing films may appear normal in purely ligamentous injuries)
Fleck sign: a small bony avulsion fragment in the space between the medial cuneiform and the base of the 2nd metatarsal on the AP weight-bearing X-ray; represents an avulsion of the Lisfranc ligament from its metatarsal or cuneiform attachment; pathognomonic of Lisfranc ligament disruption even when overall alignment appears preserved; any patient with midfoot pain after trauma who has a fleck sign = Lisfranc injury requiring formal assessment
CT and MRI: CT is used to assess the extent of fracture and displacement when plain X-ray findings are equivocal or to plan surgical fixation; MRI is the gold standard for purely ligamentous Lisfranc injuries (no bony fractures) — it directly images the Lisfranc ligament, demonstrating partial or complete tears; a partial Lisfranc ligament tear on MRI in a patient with midfoot pain and tenderness = significant injury requiring weight-bearing restrictions and close follow-up; a complete tear on MRI = operative fixation in most cases (ligamentous Lisfranc injuries have very high rates of midfoot instability and arthritis with conservative management)

Management — ORIF vs Primary Arthrodesis

ORIF with screws: standard treatment for fracture-dislocation Lisfranc injuries; the 1st, 2nd, and 3rd TMT joints (medial column) are fixed with solid or cannulated screws — these joints have minimal normal motion and can be rigidly fused or fixed; the 4th and 5th TMT joints (lateral column) are fixed with temporary K-wires — these joints have greater intrinsic mobility (important for normal forefoot pronation/supination during gait) and should NOT be rigidly fused; hardware removal is typically performed at 3–4 months (before this, the rigid medial column screws restrict normal midfoot kinematics and may cause pain); outcomes of ORIF correlate with quality of reduction — anatomical reduction is mandatory
Primary arthrodesis vs ORIF: the REALITY trial (Ly and Coetzee 2006) randomised patients with purely ligamentous Lisfranc injuries (no bony fractures) to ORIF vs primary arthrodesis; at 2-year follow-up, primary arthrodesis had significantly SUPERIOR outcomes (AOFAS scores) compared to ORIF; the rationale — in purely ligamentous injuries, the unstable midfoot joints cannot be reliably stabilised by screws alone (without the bony fragments that would heal to provide structural support); primary arthrodesis permanently stabilises these joints and provides a more reliable long-term outcome; however, primary arthrodesis should be reserved for purely ligamentous injuries — fracture-dislocation injuries (with bony fragments) are better treated with ORIF (the bony fragments provide structural support for the fixation)

Exam Pearls

Hardcastle-Myerson: Type A (total — all 5 MTs same direction); Type B (partial — some MTs displaced; B1 medial, B2 lateral); Type C (divergent — 1st MT medial, 2nd-5th lateral; C1 partial, C2 total); divergent C = most dramatic displacement
Lisfranc ligament: medial cuneiform → base of 2nd metatarsal; strongest TMT ligament; NO direct 1st-2nd MT ligament (the gap between them is the `vulnerable zone`); 2nd MT base is the `keystone` of the TMT complex
Fleck sign: avulsion fragment between medial cuneiform and 2nd MT base = pathognomonic of Lisfranc injury; even without gross displacement, a fleck sign = significant ligamentous disruption; always look for it on AP foot X-ray in midfoot injuries
Weight-bearing X-ray: mandatory for diagnosis; non-weight-bearing films may appear normal in purely ligamentous injuries; 2nd MT medial border collinear with middle cuneiform medial border; 4th MT medial border collinear with cuboid medial border
REALITY trial (Ly and Coetzee 2006): primary arthrodesis SUPERIOR to ORIF for PURELY LIGAMENTOUS Lisfranc injuries at 2 years; bony Lisfranc injuries → ORIF; ligamentous only → primary arthrodesis of medial column; the distinction bony vs ligamentous is critical for treatment selection
Medial vs lateral column fixation: medial (1st-3rd TMT) = screws (rigid — these joints have minimal normal motion; can be fused); lateral (4th-5th TMT) = K-wires only (temporary — these joints have intrinsic mobility for forefoot pronation/supination; rigid fusion causes pain and stiffness)
Missed diagnosis: up to 40% initially missed; `worst ankle sprain that isn`t`; metatarsal pain + bruising plantar midfoot (pathognomonic of TMT injury) + pain with passive abduction of the forefoot = Lisfranc until proven otherwise; weight-bearing films + CT/MRI if equivocal

Hardcastle–Myerson — Lisfranc Injuries

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