Charles J. Odgers, IV, M.D.,
Robert P. Stanton, M.D., Michael E. Pollack, M.S.
Alfred I. duPont Institute
1600 Rockland Road
Wilmington, Delaware 19803
INTRODUCTION: Tarsal coalition is a congenital abnormality consisting of varying degrees of union of one or more tarsal bones. Current pediatric orthopaedic texts as well as several articles suggest that the occurrence of a double coalition (both calcaneonavicular and subtalar) is frequent enough to warrant routine use of computed tomography (CT) to detect the unrecognized subtalar coalition in patients with symptomatic calcaneonavicular bars. It has been our experience that these studies were not detecting additional coalitions with the degree that one would expect based on previously published reports. The purpose of this study was to determine whether the routine use of CT scans to detect subtalar coalitions is warranted in patients with symptomatic calcaneonavicular bars.
MATERIALS AND METHODS: A retrospective study was performed evaluating all patients with a coded diagnosis of calcaneonavicular coalition from October 1984 to September 1995. Because the CT scan was judged to be the current "gold standard" for imaging a patient with a suspected subtalar coalition, all patients treated at our institution prior to the availability of CT scanning were not included. Patients with congenital anomalies of the lower limb ( i.e. fibular hemimelia) as well as patients with arthrogryposis and clubfoot were also eliminated. Twenty- nine patients were identified with a symptomatic calcaneonavicular coalition diagnosed by plain radiographs that satisfied the aforementioned criteria. Of these patients, 14 demonstrated bilateral involvement (only six had bilateral symptoms) for a total of 43 feet. In every case, both feet were evaluated by plain radiographs and CT scans regardless of whether symptoms were bilateral. Fifteen patients were male and 14 patients were female. The operative report and CT scan report was reviewed for each patient. Independent review of the plain films and CT scans was also performed.
RESULTS: Of the 29 patients who were evaluated by CT imaging, only one patient was noted to have both a calcaneonavicular and a subtalar coalition which was confirmed at surgery. This corresponds to a 3.4% incidence of double coalition. The subtalar coalition consisted of a fibrous bar located at the posteromedial aspect of the middle facet. In two additional cases, the CT scan report indicated one "probable" and one "possible" subtalar coalition. A third report indicated a "suggestive" coalition of the calcaneal-cuboid joint. In each of these three cases, no subtalar coalition was evident at surgical exploration. Thus there was one true positive and three false positive results.
CONCLUSION: This study suggests that the incidence of unrecognized subtalar coalition in this group of patients undergoing treatment for symptomatic calcaneonavicular coalition is too low to justify the use of CT scanning as a routine preoperative test.
[Return to Table of Contents, Back to Research Symposium Home Page, Orthopaedic Department Home Page,]