[Idiopathic high patella in adolescents. Apropos of 61 surgical cases].

The patellar height was measured according to the index of Caton and Deschamps. The normal index equals 1, the patella considered as being high with an index of 1.2 or greater. The authors reviewed 50 patients presenting with such an anomaly in patellar height to verify whether this patella alta said to be idiopathic was simply a radiographic sign or represented a true anatomic and clinical entity. 61 knees were hence operated on between 1963 and 1988, 50% of which had a lowering of the tibial tuberosity. In 8 cases, the lowering was performed secondarily, after a failure of the first operation to correct the anomaly. The mean pre-operative index of patellar height was 1.34 and the trochlea appeared indisputably dysplastic in 50 of the 61 cases. The mean age at the time of surgery was 17 years. Medial translation of the tibial tuberosity averaged 9.5 mm and the lowering 7 mm allowing a normalization of the patellar index. 76.8% of patients had a perfect post-operative stability, evaluated as a score of 8 or 9 on the ARPEGE scale. At the completion of this study it appeared that patella alta is rarely an isolated finding and is most often part of a regional patello-femoral dysplasia. Its existence, when responsible for a functional problem, must absolutely be taken into account and treated to obtain a satisfactory result.