Avascular Necrosis of the Navicular Bone
Avascular necrosis (AVN) of the navicular bone is a rare condition in adults characterized by bone death due to compromised blood supply, most commonly presenting as Müller-Weiss disease—a progressive, idiopathic fragmentation of the navicular with talonavicular joint destruction that typically requires surgical intervention for symptomatic relief. 1, 2
Definition and Pathophysiology
AVN involves death of both trabecular bone and bone marrow elements due to compromised blood supply through three main mechanisms: vascular interruption, vascular occlusion, and extravascular intraosseous compression. 1 While the femoral head is the most commonly affected site, AVN can affect other bones including the navicular, lunate, humeral head, scaphoid, and talus. 1
Risk Factors for Navicular AVN
The risk factors for navicular AVN mirror those for AVN at other sites but with some location-specific considerations:
Medication-Related Factors
- High-dose corticosteroid therapy (particularly prednisolone ≥30 mg daily) markedly increases AVN risk, especially with rapid dose escalation. 3, 4, 5
- Chemotherapy and radiation therapy are recognized risk factors. 3, 4
Systemic Diseases
- Systemic lupus erythematosus (SLE) carries significant risk, with documented cases of bilateral navicular and medial cuneiform AVN. 5
- Diabetes mellitus has been implicated in tarsal bone AVN. 2
- HIV infection significantly raises AVN risk. 3, 4
Lifestyle and Other Factors
- Excessive alcohol consumption is a major non-traumatic risk factor. 3, 2
- Foot deformity (pes planovalgus) may predispose to navicular AVN. 2
- Trauma can compromise vascular supply. 2
Spontaneous/Idiopathic Forms
- Müller-Weiss disease represents spontaneous, bilateral AVN of the navicular in adults, characterized by progressive navicular fragmentation without clear precipitating factors. 2, 6
Clinical Presentation
Pain is the predominant symptom, typically presenting as:
- Chronic midfoot pain over the dorsomedial aspect of the foot. 6
- Pain that worsens with activity and weight-bearing, not relieved by activity. 4
- Progressive symptoms associated with midfoot deformity in Müller-Weiss disease. 7
Critical consideration: Unlike inflammatory conditions, AVN pain increases with weight-bearing and does not improve with movement. 4 Night pain that is unrelenting suggests alternative diagnoses such as inflammatory arthropathy, infection, or malignancy rather than AVN. 4
Diagnostic Approach
Initial Imaging
Start with plain radiographs (anteroposterior and lateral foot views) as the first-line imaging study, despite limited sensitivity in early disease. 4 Look for:
- Navicular fragmentation and collapse (particularly lateral portion in Müller-Weiss disease). 6
- Medial protrusion of the talar head. 6
- Peri-navicular osteoarthritis and talonavicular joint destruction. 2, 6
Advanced Imaging
If radiographs are normal or equivocal with high clinical suspicion, proceed immediately to MRI without IV contrast, which is the gold standard with sensitivity and specificity approaching 100%. 4 MRI provides:
- Detection of early disease before radiographic changes. 4
- Characterization of necrotic volume and extent. 4
- Differentiation from mimics (transient bone marrow edema syndrome, subchondral insufficiency fracture). 1, 4
Optimal MRI protocol: A coronal STIR sequence alone shows 100% sensitivity, with addition of coronal T1-weighted sequence increasing confidence and specificity. 4
When to Avoid Alternative Modalities
- CT without IV contrast is less sensitive than MRI for early detection but superior for showing articular collapse extent and osseous details for surgical planning. 4
- Bone scintigraphy offers poor spatial resolution, low specificity, and inability to quantify lesion size. 4
Management
Non-Operative Management
Weight reduction and walking aids (canes or walkers) may reduce symptoms in early stages. 1 However, spontaneous navicular AVN in adults, particularly Müller-Weiss disease, typically follows a painful progressive course requiring surgical intervention. 7
Surgical Options
For symptomatic navicular AVN, surgical intervention is generally required, with options including:
Percutaneous decompression of the navicular bone for early disease. 7
Debridement with bone grafting:
Talonavicular or talonaviculocuneiform arthrodesis:
- This is the most commonly reported definitive treatment for Müller-Weiss disease with severe talonavicular arthrosis. 2, 5
- Can be performed with distal tibial autograft. 5
- Bilateral staged procedures may be necessary for bilateral disease. 2
- Significant functional improvement: American Orthopaedic Foot and Ankle Society midfoot scores improved from 34 to 80 (right) and 37 to 90 (left) in documented cases. 5
Treatment Selection Algorithm
Choose surgical approach based on:
- Early disease without collapse: Consider core decompression or debridement with bone grafting. 7, 6
- Progressive fragmentation with talonavicular joint destruction: Proceed to talonavicular or talonaviculocuneiform arthrodesis. 2, 5
- Failed non-operative therapy in younger patients: Consider vascularized bone graft as a joint-preserving option. 7
Special Considerations and Pitfalls
Bilateral Disease
Müller-Weiss disease is characteristically bilateral, though symptoms may be sequential rather than simultaneous. 2 Always evaluate both feet even when symptoms are unilateral, as the contralateral foot may develop AVN during recovery from initial surgical intervention. 5
Multifocal Involvement in Systemic Disease
Patients with SLE can develop multifocal AVN in unusual anatomic locations, including simultaneous involvement of navicular and medial cuneiform. 5 Maintain high index of suspicion in patients with rheumatologic disorders on corticosteroids.
Timing of Intervention
Joint-preserving interventions are only effective before subchondral collapse occurs. 1 Early diagnosis is critical because by the time symptoms prompt medical attention, the disease process is already underway. 4