Purpose of the study: In 1983, we reported 5 cases of a type of tarsal abnormality which often went unrecognized in children and adolescents, the so-called "too long antero-medial process of the calcaneus" (TLAP). This report analyzes 59 such abnormalities observed in 37 children and adolescents. Treatment of the 48 symptomatic cases is presented.
Material: A retrospective study was done on the files of all patients in whom oblique foot radiographs, CT scan or MRI of the foot showed an abnormal antero-medial process of the calcaneus. Of this group, patients were re-examined and radiographs of both feet (AP, lateral and oblique views) were obtained.
Methods: Gender, age at occurrence of symptoms, diagnosis and follow-up, patient complaints and successive treatment were assessed. Final clinical results were graded according to patient's complaints of pain and functional limitation as well as clinical evaluation of subtalar motion.
Results: Fifty-nine TLAPs have been found in 37 patients, 30 girls and 7 boys of 11.6 years on average at the first symptoms. Delay of diagnosis from onset of symptoms to final diagnosis averaged 2 years. First symptoms were so-called ankle sprains in 19 patients, ankle instability with tarsal pain in 17, pain and tarsal stiffness in 11, spastic flat foot in 1. In 11 patients, the abnormality was found on the opposite foot. In 2 patients, the TLAP was combined to a calcaneo-navicular bridge of the other foot. Eleven strapping managements resulted in 11 failures, 36 plaster immobilizations led to 12 good, 2 fair and 22 poor results; 25 resections gave 23 good, 1 fair and 1 poor result at a 4.6 years follow-up on average.
Discussion: In some people, the antero-medial process of the calcaneus is elongated and becomes interposed between the head of the talus and the cuboïd, far enough to cause impingement on the navicular. Because of the elongation, supination produces a "nutcracker" phenomenon with compression of the process between the talus and the cuboïd; this may result in a chondral injury of the talus head at its inferior and lateral part which faced the TLAP. Authors suggest that calcaneo-navicular coalition and TLAP represent a spectrum of types of errors in embryologie mesenchymal formation with lack of normal joint formation of the tarsal ossicles during fetal life. Immobilization treatment as primary management was particularly unsuccessful in the group with recurrent ankle sprains and persistent pain. Process resection proved a highly successful technique in management of those patients who failed to achieve good results with plaster immobilization.
Conclusion: The "too long antero-medial process of the calcaneus" should be considered when assessing possible causes of recurrent ankle sprain or persistent tarsal pain in adolescents. An oblique X-ray is usually satisfactory for diagnosis. In patients who failed a conservative management, resection of the process produced good results and painless, supple feet.