Radiographic Anomalies of the Tarsal Navicular.

INTRODUCTION: Radiographic abnormalities of the tarsal navicular are frequently encountered incidentally in children undergoing plain radiography of the foot for pain or deformity. These abnormalities are rarely deemed to be associated with the child's chief complaint or physical examination findings. Whether these radiographic anomalies are due to prior trauma, history of unrecognized osteochondritis dissecans, or avascular necrosis earlier in life remains unclear as the numerous subtle navicular abnormalities have never been characterized. The purpose of this study was thus to describe and categorize radiographic abnormalities of the tarsal navicular in a large cohort of pediatric patients.

METHODS: This was an IRB-approved retrospective review of all patients presenting to a single pediatric institution over a 1-year period in whom weightbearing foot radiographs were obtained for any reason. Radiographs were reviewed for osseous abnormalities of the navicular by a musculoskeletal radiologist, a pediatric orthopaedic surgeon, and an orthopaedic foot and ankle surgeon. Any abnormalities identified by any reviewer were reviewed in committee and jointly characterized by consensus.

RESULTS: Radiographs of 2321 feet were reviewed. One hundred fifty-five were excluded due to poor image quality or navicular immaturity, leaving 2166 for final review. The average age at radiographic exam was 12.1±3.7 years, 49% were female, and 74.5% played a sport. Navicular abnormalities were identified in 3% (64/2166 feet), and of those, dorsal pathology was identified in 64.1% (41/64) of patients. Within the abnormality group, 23.4% (15/64) had dorsal avulsion with an average age at imaging of 14±2.1 years. Dorsal ossification was identified in 18.8% (12/64) at an average age of 11.4±3.3 years. 15.6% (10/64) had dorsal bossing (average age 15.1±1.8 y). 15.6% (10/64) had avascular necrosis (average age of 6.8±3.7 y). 14.1% (9/64) had osteochondritis dissecans (average age of 11.1±1.6 y). Dorsal spurring was found in 6.3% (4/64) at an average age of 12.1±5.2 years, and OS supranaviculare was identified in 6.3% (4/64) at an average age of 14.1±0.5 years. These radiographic findings were deemed incidental in 79.7% (51/64) feet.

CONCLUSIONS: Incidental radiographic abnormalities of the navicular are present in 3% of patients and are often not the source of reported pain or symptoms. Clinicians can be armed with these findings, which may prove to be useful in the decision-making process when identifying potential targets for treatment in the management of pediatric foot pain.

SIGNIFICANCE: Various radiographic abnormalities of the navicular exist, which are often not associated with symptomatology. Clinicians should be aware of these abnormalities when treating children with foot pain or when these findings are encountered in the evaluation of other foot/ankle pathology.

LEVEL OF EVIDENCE: Level III-therapeutic.