The characteristic lesion in the nine cases of osteochondritis of the tarsal navicular in adult women which have been described is an oblique splitting of the navicular and separation of the two fragments: the inner fragment gradually glides over the head of the astragalus to its medial side; the outer fragment overrides the dorsal surface of the second and third cuneiforms. This breech between the two fragments reduces the distance between the proximal articular surfaces of the second and third cuneiforms, on the one hand, and the head of the astragalus, on the other, and ultimately these cuneiform surfaces may even articulate with the head of the astragalus. In the later stages, severe osteo-arthritic changes develop in the abnormal mid-tarsal joint. A lesion of this severity may be found on both sides. More frequently, however, while one side presents the appearances described, the other shows less extensive changes such as osteochondritis dissecans or mere compression of the plastic outer third of the navicular. All of these nine patients showed evidence of pathological changes in the navicular of each foot.
The ages of the affected patients were as follows: twenty-two, thirty-two, forty-five, fifty-one, fifty-two, fifty-two, fifty-six, fifty-seven, and fifty-nine. In the two younger patients, no secondary arthritic changes could be detected in the affected bones, but in all the others, with the exception of Case 3, marked osteo-arthritic changes were evident. The roentgenograms of Case 3, when the patient was fifty-two years of age, showed almost complete medial dislocation of the inner fragment of the navicular, but no secondary arthritic changes were detectable. Six years later, severe arthritic changes were observed. This suggests that the displacement had occurred within a year or so of the first roentgenographic examination.
In three patients—Cases 2, 3, and 4—the first metatarsal was short, the second metatarsal was hypertrophied, and the third, fourth, and fifth metatarsals were atrophied. The other cases did not demonstrate these features, although in Cases 5 and 7 some atrophy of the metatarsals was suggested.
No cases presenting similar roentgenographic appearances were observed in men.