Tarsal coalition has been well recognized as the commonest cause of peroneal spastic flat feet in children and adolescents (Mosier and Asher 1984). Other rare causes are tuberculosis and rheumatoid arthritis. If no etiology can be found the term idiopathic peroneal spastic flat foot has been coined by Schoenecker (2000). We prospectively assessed all children and adolescents with peroneal spastic flat feet seen at our clinic in the period 2002 to 2004. Twelve patients (17 feet) were assessed. The average age was 11,9 years (range10 to15years). Seventy five percent of the patients were above the 95th percentile weight for age. Screening for tuberculosis (ESR, Mantoux and chest radiograph) was negative in all patients. Rheumatoid factor was positive in one patient with juvenile idiopathic arthritis (JIA). Radiology was standardized. Plain radiographs were standing lateral and 45 degree oblique views. CT and MRI:
axial: parallel to plantar surface; coronal oblique: gantry perpendicular to the plane of the subtalar joint. This latter view best illustrates a talocalcaneal coalition (Newman 2000). Two patients (four feet) had a calcaneonavicular coalition on the 45 degree oblique plane radiographs. This was also shown on the axial CT and MRI views. No talocalcaneal coalition was visualized on the coronal oblique CT and MRI views. In order to find a diagnosis and to confirm the accuracy of the MRI and CT, the middle facet of the talocalcaneal joint was explored in eight feet and a synovial biopsy done. No talocalcaneal coalition was found. JIA was histologically confirmed in one patient. The authors concluded that the idiopathic type is by far the commonest peroneal spastic flat foot seen in our clinic. The 45 degree oblique plain radiograph is as accurate as axial CT and MRI to diagnose calcaneonavicular coalition. The coronal oblique CT and MRI views are equally accurate to exclude a talocalcaneal coalition.
