Navicular Fracture

Navicular fracture is a fracture of the tarsal navicular bone, the keystone of the medial longitudinal arch of the foot. Three types exist: avulsion or tuberosity fractures (the most common), acute body fractures, and stress fractures in athletes.

Stress fractures occur in sprinters, jumpers, basketball players and footballers, and are often missed for months. The navicular has a watershed blood supply in its central third (blood enters from the dorsalis pedis and the medial plantar arteries), so stress fractures and body fractures are prone to delayed union, nonunion and avascular necrosis.

The Sangeorzan classification describes body fractures. Type 1 is a coronal fracture of the body with a transverse line in the coronal plane, type 2 is a dorsolateral-to-plantar-medial oblique fracture with a large medial fragment, and type 3 is a comminuted fracture with a lateral or medial extension and a poor outcome. Dorsal lip avulsion fractures are common after inversion injuries.

Complications are nonunion (up to 25 to 35% of stress fractures with non-operative care), avascular necrosis, post-traumatic arthritis of the talonavicular joint, flatfoot deformity, chronic pain and refracture.

Pathophysiology.

The tuberosity avulsion follows a forced eversion pull of the tibialis posterior tendon and the spring ligament. Body fractures follow axial loading through a plantar flexed foot, such as a fall or a road traffic collision, and are often part of a midfoot injury. Stress fractures begin with repetitive loading at the poorly perfused central third, usually as a sagittal plane fracture that starts dorsally.

Acute fractures cause medial midfoot pain, swelling, bruising and inability to bear weight. The tuberosity fracture is tender over the medial prominence of the navicular.

Stress fractures give an insidious dorsal midfoot ache that is worse with running and jumping and relieved by rest. The N-spot (tenderness over the dorsal proximal navicular, at the apex of the talonavicular joint) is the key finding. Pain on the single leg hop test and tenderness on rotation of the foot support the diagnosis. Assess foot alignment, pes cavus and limited ankle dorsiflexion.

• Radiographs: weight bearing anteroposterior, lateral and oblique views of the foot. Stress fractures are often invisible at first; look for an accessory navicular or os naviculare, which can mimic a fracture.
• CT is the investigation of choice for stress fractures and body fractures, to define the fracture line, displacement, comminution and the healing.
• MRI is the most sensitive for early stress injury and bone marrow oedema and for avascular necrosis.
• Technetium bone scan if MRI is not available.
• Vitamin D, calcium and bone profile, and a nutritional and hormonal review in athletes (relative energy deficiency).

Differential diagnosis.

• Accessory navicular and posterior tibial tendon dysfunction.
• Midfoot sprain (Lisfranc injury) and cuboid fracture.
• Talar head fracture and tibialis posterior tendinopathy.
• Kohler disease in children and osteonecrosis (Mueller-Weiss syndrome).

Tuberosity or avulsion fracture. Weight bearing as tolerated in a walking boot or a short leg cast for 4 to 6 weeks, followed by physiotherapy. Fix with a screw when displaced by more than 5 mm or when there is symptomatic nonunion.

Stress fracture.

• Non-weight bearing in a short leg cast or boot for 6 to 8 weeks, followed by a gradual return to loading with CT confirmation of union.
• Non-operative treatment gives a better outcome than weight bearing, with a rate of union of about 80 to 90%.
• Surgery (screw fixation, with bone graft for nonunion): complete fractures, displaced fractures, failed non-operative treatment after 3 to 4 months, delayed union and nonunion, and in elite athletes seeking a faster return.
• Return to sport at 4 to 6 months after CT shows union.

Body fractures.

• Undisplaced: non-weight bearing in a short leg cast for 6 to 8 weeks.
• Displaced (over 1 to 2 mm), type 2 and type 3: open reduction and internal fixation with lag screws (3.5 mm), plates or Kirschner wires, and bone graft for comminution. Restore the length and medial arch.
• External fixation for severe swelling or open injuries. A primary talonavicular or naviculocuneiform fusion is used for severe comminution.
• Postoperative: non-weight bearing for 6 to 12 weeks, then progressive weight bearing and physiotherapy.

Open fracture. Intravenous co-amoxiclav 1.2 g every 8 hours (or cefazolin 2 g every 8 hours) within 1 hour of injury.

• Continue until 24 hours after wound closure for types I and II.
• For type III, continue until 72 hours or 24 hours after soft tissue cover, whichever is earlier.
• Co-amoxiclav maximum 3.6 g daily; every 12 hours at creatinine clearance 10 to 30 mL/min; check liver tests in courses over 7 days.

For heavy contamination or soft tissue loss add gentamicin 5 mg/kg intravenously once daily for up to 72 hours. Check creatinine daily and a level before the second dose. Avoid, or extend the interval, at eGFR under 60 mL/min/1.73 m2. With severe penicillin allergy use clindamycin 600 mg intravenously every 8 hours (maximum 2.7 g daily) with gentamicin.

Tetanus booster 0.5 mL intramuscularly if the last dose was over 10 years ago. Add tetanus immunoglobulin 250 units intramuscularly (500 units if over 24 hours since injury or heavily contaminated) when immunisation is incomplete or unknown. Debride and stabilise within 24 hours.

Operative antibiotic prophylaxis. Cefazolin 2 g intravenously (3 g when weight is 120 kg or over) within 60 minutes before incision as a single dose. Repeat after 4 hours or blood loss over 1500 mL. With severe penicillin allergy, give vancomycin 15 mg/kg intravenously starting 90 to 120 minutes before incision as a single dose, with levels and creatinine checked in prolonged cases.

Thromboprophylaxis. Enoxaparin 40 mg subcutaneously once daily for the period of immobilisation and restricted weight bearing (usually 4 to 6 weeks) in patients with a lower limb cast or non-weight bearing. Start within 24 hours of injury or after surgery.

• 20 mg once daily at creatinine clearance under 30 mL/min.
• Adjust by anti-Xa level in obesity and renal impairment.
• Check the platelet count on days 5 to 14 for heparin induced thrombocytopenia.
• Add mechanical prophylaxis as needed.

Analgesia.

• Paracetamol 1 g orally every 6 hours as needed for up to 5 to 7 days (maximum 4 g daily; 3 g daily when weight is under 50 kg, with chronic alcohol use or hepatic impairment).
• Ibuprofen 400 mg orally every 8 hours with food for up to 5 days (maximum 1200 mg daily). Avoid with eGFR under 30 mL/min/1.73 m2, peptic ulcer, heart failure or anticoagulant use. Avoid NSAIDs when union is delayed.
• Oral morphine 5 to 10 mg every 4 hours as needed for severe pain for up to 3 days. Start 2.5 to 5 mg with age over 75 or eGFR under 30 mL/min/1.73 m2. Avoid exceeding 60 mg in 24 hours without senior review. Monitor sedation and respiration and prescribe a laxative.

Complex regional pain syndrome prevention. Vitamin C (ascorbic acid) 500 mg orally once daily for 50 days from the day of injury (maximum 500 mg daily; the evidence is moderate). Avoid with a history of oxalate kidney stones, and limit with eGFR under 30 mL/min/1.73 m2. No routine monitoring.

Monitoring. Radiographs at 2 weeks, 6 weeks and 3 months, and CT at 6 to 8 weeks for stress fractures to check for union. Pain, N-spot tenderness and the single leg hop test before return to sport. MRI at 3 to 6 months if avascular necrosis is suspected. Foot alignment and arch at follow up.

Referral and escalation. Refer displaced body fractures, stress fractures that fail 3 months of treatment, and fractures with a talonavicular dislocation to orthopaedics or foot and ankle surgery within 1 week. Same day referral for open fractures, midfoot dislocations, vascular compromise or compartment syndrome.

Special groups.

• Athletes: stress fractures in runners, sprinters and jumpers need a full training, nutrition and biomechanical review, and screening for bone health and relative energy deficiency.
• Older adults: insufficiency fractures are uncommon; assess bone health.
• Diabetes: neuropathic midfoot fractures can be painless; consider Charcot arthropathy.
• Kidney impairment: avoid ibuprofen and reduce morphine doses.