What is the treatment approach for a female adolescent with an accessory navicular bone causing discomfort and pain?

Treatment Approach for Symptomatic Accessory Navicular in Female Adolescents

Begin with conservative management for 6-8 weeks, including immobilization, NSAIDs, and orthotic support; if pain persists despite these measures, proceed to surgical excision of the accessory navicular bone, which yields excellent outcomes in approximately 87.5% of adolescent patients. 1, 2

Initial Conservative Management

Start with a structured 6-8 week trial of non-operative treatment before considering surgery. 1

• Immobilization: Place the foot in a short-leg cast or brace with limited weight-bearing activity 1, 3
• Pain control: Prescribe NSAIDs for pain relief, combined with rest, ice application, and elevation 1
• Mechanical support: Provide orthotic devices or arch supports to stabilize the foot and reduce strain on the posterior tibialis tendon 1
• Activity modification: Restrict running, jumping, and prolonged walking during the treatment period 3, 4

The rationale for this approach is that while accessory navicular bones are present in approximately 10% of the population, most remain asymptomatic and only a small subset requires surgical intervention 2. Conservative measures can resolve symptoms in some patients, particularly those who are less athletically active 5.

Diagnostic Confirmation During Conservative Treatment

Obtain standard foot radiographs as the initial imaging study, with particular attention to the 45-degree eversion oblique view. 1, 5

• The accessory navicular typically appears triangular or heart-shaped on radiographs 6
• If radiographs are negative or equivocal but clinical suspicion remains high, proceed to MRI without IV contrast 1, 7
• MRI allows visualization of bone marrow edema within the ossicle, assessment of the synchondrosis between the accessory bone and navicular, and evaluation of associated posterior tibialis tendon pathology 1, 7

A critical pitfall: bilateral accessory navicular bones are common, but symptoms are typically unilateral. If considering advanced imaging, MRI or bone scintigraphy will show increased signal or uptake only on the symptomatic side 6.

Surgical Intervention for Failed Conservative Management

When conservative treatment fails after 6-8 weeks, surgical excision is the treatment of choice for young, active patients. 1, 2

Surgical Technique Options

Simple excision of the accessory navicular bone is the preferred approach, particularly in patients without significant flatfoot deformity. 2, 4

• Make a 2 cm incision at the medial prominence of the navicular bone 4
• Partially dissect the posterior tibial tendon to expose the accessory navicular 4
• Excise the accessory navicular bone and shave any prominence of the navicular tuberosity 4
• Repair the posterior tibial tendon before closure 4

Excision with posterior tibial tendon advancement can be considered, though it shows no significant outcome advantage over simple excision and trends toward more complications. 2

• In a series of 32 feet, isolated excision (14 feet) versus excision plus tendon advancement (18 feet) showed no significant difference in outcomes 2
• Overall excellent or good functional outcomes occurred in 87.5% of cases 2
• The tendon advancement procedure had a trend toward more complications and reoperations 2

Postoperative Protocol

Immobilize the foot in inversion position with cast or brace for 2 weeks with no weight-bearing. 4

• Begin weight-bearing as tolerated with crutches at 2 weeks, then wean from crutches 3
• Avoid strenuous jumping or dancing for 3 months postoperatively 4
• Average hospital stay is 5 days 4
• Most patients return to normal activity within 6 weeks 3

Special Considerations

Even in rare cases with multiple accessory navicular bones (two separate ossicles), follow the same treatment algorithm with excellent outcomes. 3

For patients with concurrent flatfoot deformity or old sprain injuries, outcomes may be slightly less favorable (good rather than excellent), but surgery remains beneficial. 4

The histologic basis for symptoms involves inflammatory chondro-osseous changes in the navicular-accessory navicular synchondrosis, consistent with chronic trauma and stress fracture 6. This explains why immobilization can be effective and why athletic adolescents are particularly symptomatic 5, 6.

Simple excision offers advantages of less invasiveness to the posterior tibial tendon and medial longitudinal arch, shorter immobilization time, and smaller incision compared to procedures involving tendon advancement. 4