[Infra-radiographic decalcifying algodystrophy of the lower limb].

The authors have only reported cases responding to the following criteria: A) necessarily: 1) Clinical appearance of algodystrophy. 2) Intense hyperfixation of the bone scan. 3) X rays repeated a sufficient number of times always normal and submitted to the judgement of six rheumatologists not forewarned, to eliminate the subjective factor in the diagnosis of normality. 4) Clinical cure within the usual period. 5) Return to normal of the bone scan. B) Eventually: 6) Proved decalcifying algodystrophy from another joint site in the past history. 7) Histological appearance compatible with algodystrophy on bone biopsy. Four cases are presented (hip one case, knee two cases, ankle one case) which fulfill the five necessary criteria. The course seems shorter than in the classical decalcifying forms: 2 months instead of 4 1/2 months on average for the hip; 5 months instead of 7 months on average for the knee; 5 months instead of 12 months on average for the foot. This short course is in favour of the theory of early and rapid reconstructive bone changes, which do not leave the algodystrophy the time to demineralise the bone more than 30 to 50% which is the time necessary for the increased radiographic bone transparency to become clear.