Management of Cyst Adjacent to the Superior Margin of the Navicular Bone
For a cyst adjacent to the superior navicular margin, proceed with MRI to characterize the lesion and determine whether it represents an osteochondral lesion, simple bone cyst, or aneurysmal bone cyst, followed by surgical curettage with bone grafting for symptomatic lesions.
Initial Diagnostic Approach
Advanced Imaging is Essential
MRI is the preferred next imaging study for characterizing cystic lesions adjacent to the navicular bone, as it effectively identifies osteochondral lesions with high sensitivity (96%) and can detect adjacent cysts associated with osteochondral injuries 1.
MRI demonstrates cyst characteristics including septations, fluid levels (suggesting aneurysmal bone cyst), and relationship to surrounding structures 1.
CT without contrast may be helpful to visualize subchondral cysts and assess cortical integrity, particularly when surgical planning is needed 1.
Differential Diagnosis Considerations
The location adjacent to the superior navicular margin suggests several possibilities:
Osteochondral lesion-associated cyst: MRI shows high signal on T2-weighted images deep to osteochondral lesions, indicating instability 1.
Simple bone cyst: Typically presents as a solitary, fluid-filled lesion that may be asymptomatic or cause pain 2, 3.
Aneurysmal bone cyst (ABC): Rare in the foot (4-6.3% of all ABCs), typically presents in the second decade of life with pain and potential deformity 4.
Treatment Algorithm
For Symptomatic Lesions
Surgical intervention is recommended for symptomatic cysts resistant to conservative management:
Curettage with bone grafting achieves 90% healing rates regardless of whether autograft or allograft is used 5.
Minimally invasive endoscopic curettage through a single uni-osseous portal reduces the risk of iatrogenic navicular fracture 2.
For simple bone cysts, continuous decompression using hydroxyapatite cannulated pins after curettage provides 81% recurrence-free survival at 5 years with shorter operative times compared to calcium phosphate cement filling 3.
Aneurysmal bone cysts require curettage and packing with allograft, with successful outcomes reported in navicular lesions despite recurrence rates up to 22% 4.
Contraindications to Minimally Invasive Approach
The single-portal endoscopic technique is contraindicated in multiple septated cysts, presence of pathologic fracture, or aggressive cystic lesions 2.
Important Clinical Caveats
Age under 10 years is an independent risk factor for recurrence (particularly for simple bone cysts), requiring closer surveillance 3.
In pediatric patients with flatfoot deformity, focal navicular pain should raise suspicion for underlying osseous lesions that may be missed if attributed solely to the deformity 4.
Active phase cysts and those in long bones have higher recurrence rates, though navicular location may behave differently 3.
Local recurrence following curettage occurs in up to 22% of aneurysmal bone cysts, with patient age and lesion size comprising the main risk factors 4.
Surgical Technique Considerations
For optimal outcomes:
Minimally invasive curettage with ethanol cauterization, disruption of the cystic boundary, and synthetic calcium sulfate bone-graft substitute placement achieves the highest healing rates (92%) and shortest time to union (3.7 months) 6.
Placement of a cannulated screw for drainage after bone substitute insertion provides continuous decompression with 89% healing rates 5.