Tarsal navicular bone size in diabetics: radiographic assessment

To test the anecdotal observation that isolated navicular collapse is associated with diabetes mellitus, we quantified the size of the tarsal navicular bone in subjects with and without diabetes and tested for association of size with age, height, weight, body mass index (BMI), gender, smoking, bone mineral density (BMD), duration, and level of control of diabetes.

Ankle radiographs of 200 patients (122 female; 78 male; mean age 58 years [27-89]), 100 with type II diabetes and 100 age- and gender-matched controls were selected and reviewed. The anteroposterior (AP) dimension of the mid-navicular bone was measured from lateral radiographs. For standardization, the supero-inferior (SI) dimension of the calcaneal was measured and the navicular-calcaneus ratio calculated. Statistical evaluation included independent sample t tests and linear regression analyses.

Diabetic subjects had a significantly smaller navicular AP dimension and navicular-calcaneus ratio compared with controls (p = 0.02 and p = 0.0001 respectively). Age, gender, height and duration of diabetes had no association with the navicular-calcaneus ratio. The navicular-calcaneus ratio was inversely correlated with weight (p = 0.01) and BMI (p < 0.001) and directly correlated with smoking (p = 0.04). Reliability of the radiographic measurements was excellent (ICC 0.80-0.97; SEM 0.3-1.7 mm).

The anteroposterior dimension of the navicular is smaller in type II diabetic subjects than in age- and gender-matched controls. We hypothesize that this might be due to navicular collapse of multifactorial causes.