Multicenter study of Blount disease in Japan by the Japanese Pediatric Orthopaedic Association.

BACKGROUND

In order to investigate the epidemiology and features of Blount disease in Japan, the Japanese Pediatric Orthopaedic Association conducted a multicenter study on Blount disease in 2003.

METHODS

Questionnaires were sent to 1,350 training hospitals of the Japanese Orthopaedic Association. This study included those with stage I or II diagnosed between 1990 and 2002 and those with stage III or higher diagnosed between 1980 and 2002 based on the Langenskiöld classification. The questionnaire items included age at diagnosis, sex, presence or absence of a family history of bowlegs, past history of trauma, birthplace, age when starting to walk, height and weight at the initial presentation, laterality of the affected knee, disease types (infantile or adolescent), treatments, and plain radiographic findings.

RESULTS

The results for 212 patients with 296 affected knees were obtained. The disease types were infantile in 190 patients with 270 affected knees and adolescent in 22 patients with 26 affected knees. There were more girls among cases with both types. Among the infantile-type cases, there were more patients with bilaterally affected knees; however, in the adolescent-type cases, there were more patients with unilaterally affected knees. Patients with either type tended to be obese at diagnosis. There was little difference in age at which patients with either type started to walk, compared with the mean age for the general population. Conservative treatment was applied to most infantile-type cases in stage I or II, whereas surgery was performed in all but one of those with stage III or IV of the disease. Most adolescent-type cases underwent surgery.

CONCLUSIONS

This was the first multicenter study on Blount disease in Japan. Among 296 knees, the majority of these knees had stage I or II Blount disease. Very few cases had stage III or higher disease, and there were 35 knees with the infantile type and 19 with the adolescent type in the 23 years from 1980 through 2002.