Variations in calcaneonavicular morphology demonstrated with radiography.

PURPOSE: To determine and classify radiographically demonstrated variations in calcaneonavicular morphology and to estimate prevalence in a clinically relevant patient population. MATERIALS AND METHODS: Retrospective review was performed of foot radiographs obtained during diagnostic evaluation of 460 consecutive patients who presented to the emergency department with acute foot pain. Variations in calcaneonavicular morphology depicted on the medial oblique view (obtained at a 45 degrees angle) were classified into four groups according to morphologic type (types 1-4), and the prevalence of each type was calculated. Chi2 analysis was used to compare the prevalence of each type in male patients and in female patients. One-way analyses of variance were used to compare mean ages of patients for each type and mean calcaneonavicular gaps for each type. RESULTS: The prevalence of morphologic types 1, 2, and 3 was 94.3%, 2.8%, and 2.8%, respectively. The combined prevalence of types 2 and 3 (calcaneonavicular coalitions produced by synchondrosis and syndesmosis, respectively) was 5.6% (95% CI: 3.5%, 7.8%). There were no patients with type 4 morphology (synostosis). The numbers of male patients and female patients with morphologic types 1-3 were approximately equal (P =.9), and there was no statistically significant correlation between any of these three morphologic types and patient age (P =.2). The calcaneonavicular gap was significantly narrower in types 2 and 3 than in type 1 (P =.01), which was characterized as the normal morphology. CONCLUSION: The general prevalence of calcaneonavicular coalition (synchondrosis and syndesmosis) may be greater than previously reported, but further research is needed to prove the validity of this hypothesis.

The sensitivity of carpal bone indices to rotational malpositioning.

We investigated the dependence of 20 radiographic carpal measurements (carpal indices) on rotational positioning errors in posteroanterior and lateral radiographs. The measurements were made from "true perspective" digitally reconstructed radiographs created from computed tomography data. Most posteroanterior indices were not affected by rotation. Carpal height, carpal height ratio, revised carpal height ratio, capitate-radius distance, and carpal ulnar translocation were particularly robust. Lateral-view indices involving the scaphoid were the most sensitive to simulated malpositioning: radioscaphoid, scapholunate, and scaphocapitate angles were reduced from 58 degrees, 48 degrees, and 56 degrees at true lateral to 30 degrees, 24 degrees, and 34 degrees, respectively, at 20 degrees external rotation. Observers were unable to estimate the degree of malpositioning accurately in either view. Our results support use of the "scaphopisocapitate" criterion for assessing correct positioning in lateral plain radiographs.