Navicular fractures

The navicular is the keystone of the medial longitudinal arch, between the talar head and the three cuneiforms. Its centre is a watershed zone with a poor blood supply, which explains the slow healing of body and stress fractures. Body fractures shorten the medial column and drive the forefoot into abduction or adduction.

Mechanism

Dorsal avulsion: plantarflexion and eversion (talonavicular capsule and dorsal ligaments). Tuberosity: eversion against the pull of tibialis posterior and the spring ligament. Body: axial load on a plantarflexed foot (fall, car crash), often with midfoot injuries. Stress fracture: repetitive loading in sprinters, jumpers and basketball players.

Clinical findings

• Dorsal midfoot pain and swelling; tenderness over the navicular.
• Tuberosity: tenderness at the medial bump; weak inversion.
• Stress fracture: vague dorsomedial midfoot ache with activity, tender "N spot" on the dorsum; often missed for months.
• Body fractures: look for an associated Lisfranc, cuboid or calcaneocuboid injury (the whole midfoot is loaded).

Imaging

• AP, oblique and lateral of the foot, weight-bearing when possible.
• CT for body fractures and to confirm stress fractures; MRI for early stress reactions.

• AP, oblique and lateral of the foot; weight-bearing films when the patient can stand.
• Do not mistake an accessory navicular (smooth, rounded edges, often bilateral) or an os supranaviculare for a fracture.
• CT for body fractures (pattern, comminution, talonavicular step) and to confirm stress fractures; MRI detects early stress reactions.

Classification

83A

Extra-articular: dorsal lip avulsion, tuberosity fracture.

83B

Partial articular.

83C

Complete articular (body).

Sangeorzan 1

Fracture in the coronal plane of the navicular (dorsal–plantar split), dorsal fragment less than half the bone, no forefoot angulation.

Sangeorzan 2

Line from dorsolateral to plantar-medial; the large dorsomedial fragment and the forefoot shift medially (adduction). The most common type.

Sangeorzan 3

Central or lateral comminution, forefoot abducted; often with calcaneocuboid injury.

Stress (Saxena)

I dorsal cortex only, II into the body, III through to the plantar cortex.

Types shown in 3D

Dorsal avulsion

A flake from the dorsal lip, pulled off by the talonavicular capsule (83A). The most common navicular fracture: treat like a sprain unless the fragment is large.

Tuberosity

The medial tuberosity is pulled off by tibialis posterior during eversion (83A). Distinguish from an accessory navicular. Displaced more than about 5 mm: screw.

Sangeorzan 1

Fracture in the coronal plane of the navicular (dorsal–plantar split), dorsal fragment less than half the bone, no forefoot angulation.

Sangeorzan 2

The commonest body fracture: the line runs from dorsolateral to plantar-medial; the large dorsomedial fragment and the forefoot shift medially (adduction). ORIF with lag screws.

Sangeorzan 3

Central or lateral comminution with lateral displacement of the forefoot (abduction); look for a calcaneocuboid injury. Bridge plating to the cuneiforms or external fixation, sometimes primary fusion.

Stress fracture

Sagittal fracture in the avascular central third, starting at the dorsal-proximal cortex (Saxena I–III). Often invisible on X-ray: CT or MRI. Strict non-weight-bearing cast or screw fixation in athletes.

Treatment

Dorsal avulsion

Symptomatic: boot or cast 4–6 weeks. Excise or fix only a large fragment that carries more than about a quarter of the talonavicular surface or a symptomatic non-union.

Tuberosity

Undisplaced: cast 4–6 weeks. Displaced more than about 5 mm (tibialis posterior insufficiency): screw fixation. Painful non-union: excise the fragment and reattach the tendon.

Body

Undisplaced: non-weight-bearing cast 6–8 weeks. Displaced (> 1–2 mm articular step or medial column shortening): ORIF with lag screws through a dorsomedial approach, restoring the length of the medial column; bridge plating to the cuneiforms or an external fixator when comminuted (type 3). Primary fusion for unreconstructable crush.

Stress fracture

Incomplete: strict non-weight-bearing cast for 6 weeks. Complete, displaced, sclerotic or in elite athletes: percutaneous screw fixation (with grafting for non-union).

Aftercare

Body fractures: non-weight-bearing 8–12 weeks, then an arch support. Stress fractures: graduated return to sport after CT-proven healing.

Complications

• Avascular necrosis and collapse of the central fragment
• Talonavicular arthritis
• Non-union (stress fractures, tuberosity)
• Loss of medial column length: flatfoot or forefoot malalignment