Accessory navicular is an extra bone or ossicle located on the medial side of the foot, adjacent to the navicular bone. It is a common anatomical variant that can sometimes cause pain or dysfunction.
Definition and Classification
Accessory navicular refers to an additional ossicle that is present in some individuals and is classified into three main types:
- Type I: A small sesamoid bone within the posterior tibial tendon.
- Type II: A larger, connected ossicle with a synchondrosis to the navicular.
- Type III: A fused, enlarged navicular tuberosity (cornuate navicular).
Anatomical Location and Relationships
Understanding the position of the accessory navicular is crucial for diagnosis:
- Located on the posteromedial aspect of the navicular bone.
- May affect the insertion point of the posterior tibial tendon.
- Can alter foot biomechanics, specifically arch support.
Clinical Significance
The presence of an accessory navicular can:
- Cause pain due to irritation or inflammation.
- Lead to posterior tibial tendon dysfunction.
- Affect gait and weight distribution.
Prevalence and Demographics: Who is Affected by Accessory Navicular?
Accessory navicular is a relatively common anatomical variant, but its symptomatic presentation varies.
General Prevalence
- Found in approximately 4-21% of the general population.
- More commonly bilateral but can be unilateral.
Age and Gender Distribution
- Often detected in adolescents and young adults due to onset of symptoms.
- Slight female predominance reported in symptomatic cases.
Risk Factors for Symptomatic Accessory Navicular
Certain factors increase the likelihood of developing symptoms:
- High-impact or repetitive foot stress activities (e.g., runners).
- Flatfoot deformities and pes planus.
- Trauma or overuse injuries affecting the medial foot.
Symptoms of Accessory Navicular: Recognizing the Signs
Identifying the symptoms of accessory navicular is essential for early diagnosis and intervention.
Common Symptomatic Presentations
Patients with accessory navicular syndrome often present with:
- Medial foot pain, especially over the navicular prominence.
- Swelling and tenderness along the posterior tibial tendon.
- Difficulty wearing shoes due to prominence irritation.
Activity-Related Symptoms
Symptoms often worsen with:
- Prolonged walking or running.
- Activities involving repetitive foot motion.
- Standing for extended periods.
Physical Signs to Observe
During examination, you might notice:
- A palpable bony prominence on the medial foot.
- Redness or inflammation over the site.
- Limited foot function or altered gait.
Diagnostic Techniques for Accessory Navicular: From Physical Examination to Imaging
Accurate diagnosis depends on combining clinical assessment with appropriate imaging.
Physical Examination Protocol
Key components include:
- Palpation of the medial foot for tenderness.
- Assessing foot arch and posterior tibial tendon function.
- Evaluating gait and weight-bearing patterns.
Imaging Modalities
- X-rays: Primary tool to visualize accessory ossicles.
- MRI: Useful for detecting soft tissue inflammation and tendon involvement.
- CT scans: Provide detailed bony anatomy if surgical planning is needed.
Differential Diagnostic Considerations
Rule out other causes of medial foot pain such as:
- Navicular stress fractures.
- Tendonitis or tendon tears.
- Tarsal coalition.
Importance of Patient History
Inquire about:
- Onset and duration of symptoms.
- Activities that exacerbate pain.
- Previous foot injuries.
Common Misdiagnoses: Distinguishing Accessory Navicular from Other Foot Conditions
Accessory navicular symptoms can mimic other conditions, leading to frequent misdiagnosis.
Conditions Often Confused with Accessory Navicular
- Plantar fasciitis
- Posterior tibial tendon dysfunction
- Navicular stress fractures
- Tarsal coalition
Key Differentiating Features
- Location of pain: accessory navicular pain is localized medially near the navicular tuberosity.
- Imaging findings: presence of accessory ossicle vs. fracture lines or coalition.
Clinical Pitfalls to Avoid
- Attributing medial foot pain solely to soft tissue injury without imaging.
- Overlooking accessory navicular in patients with persistent medial foot pain.
Conservative Treatment Options for Accessory Navicular: Non-Surgical Approaches
Many patients respond well to conservative treatment, which should be the first line of management.
Rest and Activity Modification
- Limiting activities that exacerbate symptoms.
- Avoiding high-impact sports during flare-ups.
Orthotic Support
- Custom orthotics to support the medial arch.
- Cushioned shoes to reduce irritation over the bony prominence.
Physical Therapy
- Strengthening exercises for the posterior tibial tendon.
- Stretching protocols to improve foot flexibility.
- Modalities like ultrasound or ice to reduce inflammation.
Pharmacologic Interventions
- NSAIDs for pain and inflammation control.
- Topical analgesics as adjunct therapy.
Monitoring and Follow-Up
- Regular evaluation to assess symptom progression.
- Adjust treatment plan based on patient response.
Surgical Interventions: When and How to Proceed with Accessory Navicular Excision
Surgery is reserved for cases where conservative treatment fails.
Indications for Surgery
- Persistent pain interfering with daily activities.
- Dysfunction of the posterior tibial tendon.
- Significant bony prominence causing shoe irritation.
Surgical Techniques
- Kidner procedure: Excision of the accessory navicular and reattachment of the posterior tibial tendon.
- Minimally invasive approaches when applicable.
Risks and Benefits
- Benefits: pain relief, improved foot function.
- Risks: infection, tendon weakness, incomplete symptom resolution.
Postoperative Considerations
- Immobilization and limited weight-bearing initially.
- Gradual rehabilitation to restore strength and flexibility.
Rehabilitation and Recovery: Post-Treatment Care for Accessory Navicular
Effective rehabilitation is crucial for optimal recovery post-treatment.
Early Post-Treatment Phase
- Rest and elevation to reduce swelling.
- Use of walking boot or cast as prescribed.
Physical Therapy Focus
- Gradual strengthening of the posterior tibial tendon.
- Balance and proprioception exercises to restore function.
- Gait training to correct compensatory patterns.
Timeline for Recovery
- Conservative treatment recovery: weeks to months.
- Post-surgical recovery: typically 3-6 months depending on procedure.
Patient Education and Prevention
- Importance of compliance with rehabilitation protocols.
- Footwear recommendations to prevent recurrence.
- Awareness of symptoms indicating complication.