What is the initial approach to treating issues related to the os navicular and accessory os peroneum in the foot?

Initial Management of Os Navicular and Accessory Os Peroneum

Begin with plain radiographs of the foot as the initial imaging study, followed by MRI without contrast if radiographs are negative or equivocal and symptoms persist. 1

Diagnostic Approach

Initial Imaging

• Obtain standard foot radiographs first to identify the presence of accessory ossicles, assess for synchondrosis disruption, or rule out fracture 1
• Plain radiographs can identify the three types of accessory navicular: Type I (ossicle within posterior tibial tendon), Type II (synchondrosis with navicular), and Type III (cornuate navicular) 2
• The os peroneum appears as a small sesamoid bone within the peroneus longus tendon adjacent to the cuboid on standard views 3

Advanced Imaging When Radiographs Are Inconclusive

• MRI without IV contrast is the preferred next study for symptomatic accessory ossicles when radiographs are negative or equivocal 1
• MRI optimally visualizes bone marrow edema within the ossicle, the synchondrosis integrity, and associated tendon pathology (posterior tibialis for accessory navicular; peroneus longus for os peroneum) 1
• Contrast administration is not routinely needed unless MR arthrography is performed to demonstrate synchondrosis disruption 1
• Bone scintigraphy with Tc-99m-MDP can show increased uptake at the synchondrosis due to chronic stress reaction, but a negative scan excludes symptomatic ossicles while positive findings lack specificity 1, 2

Key Diagnostic Pitfall

• Many accessory ossicles are incidental findings discovered after trauma and are not the source of pain 4
• Clinical correlation is essential—the mere presence of an accessory ossicle does not confirm it as the pain source 4
• Type II accessory naviculars with synchondrosis are most likely to become symptomatic due to tension, shear, and compression forces from the posterior tibial tendon pull and foot pronation 2

Conservative Management (First-Line Treatment)

For Symptomatic Accessory Navicular

• Initiate analgesics (acetaminophen first-line) combined with shoe inserts providing medial arch support 4
• Consider orthotics to reduce stress on the synchondrosis by controlling foot pronation 2
• Immobilization with casting may be attempted if orthotics fail 2
• Physical therapy focusing on stretching and progressive strengthening of ankle and hip muscles 5

For Symptomatic Os Peroneum

• Bracing, taping, and foot orthotics to allow healing of involved tissues 5
• Stretching exercises for the peroneus longus tendon 5
• Analgesics for pain control 5
• Conservative treatment typically spans 10-13 weeks with progressive functional restoration 5

Duration and Expectations

• Conservative management should be attempted for at least 8-12 weeks before considering surgical intervention 5, 2
• Success rates with conservative treatment vary, but approximately 15-20% of patients may ultimately require surgery 6

Surgical Management (When Conservative Treatment Fails)

Indications for Surgery

• Persistent symptoms after adequate trial of conservative measures (minimum 8-12 weeks) 6, 2
• Continued restriction of activities despite orthotics and analgesics 6
• Difficulty with shoe fitting due to prominent ossicle 6

Surgical Options for Accessory Navicular

• Simple excision of the ossicle with its synchondrosis is equally effective as the Kidner procedure (excision plus posterior tibial tendon transposition to undersurface of navicular) 6
• Both procedures achieve symptom relief in approximately 83% of cases (15 of 18 patients) 6
• The Kidner procedure does not confer additional advantage over simple excision 6
• Do not transpose the posterior tibial tendon routinely—simple excision with synchondrosis removal is sufficient 2

Surgical Option for Os Peroneum

• Surgical excision of the ossicle provides symptomatic relief when multipartite or fractured 3
• The procedure involves excising the os peroneum from within the peroneus longus tendon 3

Postoperative Rehabilitation

• Focus on joint mobilization and progressive strengthening 5
• Typical rehabilitation spans 9-18 weeks with 18 visits 5
• Expected outcomes include 70-100% return of range of motion, 100% strength restoration in hip and ankle, and return to full activity level 5

Common Clinical Pitfalls

• Misdiagnosing incidental accessory ossicles as the pain source after trauma—always correlate imaging findings with clinical examination 4
• Failing to recognize that accessory ossicles exist in approximately 4% of asymptomatic subjects 1
• Unnecessary immobilization or surgery when the ossicle is not truly symptomatic 4
• Overlooking associated tendon pathology (posterior tibialis or peroneus longus tears) that may be the actual pain generator 1
• Performing the more complex Kidner procedure when simple excision achieves equivalent results 6