Abstract
Introduction
We report 3 cases from different centres of infantile tibia vara in which the deformity was due to slippage of the proximal tibial epiphysis on the metaphysis; the aim of this study was to define the features of this previously unreported condition, and their implications for management.
Method
Three cases of tibia vara secondary to atraumatic slippage of the upper tibial epiphysis on the metaphysis were identified from three different centres. The case notes and imaging studies were retrospectively reviewed to distinguish common clinical and radiographic features.
Results
There were one male and two females, all of non-Caucasian origin, (age 3–7 years). All patients' weights were above the 97th centile for age. In all cases there was an infero-medial subluxation of the tibial epiphysis over a dome shaped proximal tibial metaphysis, with disruption of continuity between their lateral borders. The height of the medial tibial plateau was preserved in all cases.
New bone formation suggests this is a chronic process. The evolution of one case indicates that pathogenesis is shared with infantile Blount's disease. A gradual deformity correction was performed in all cases using circular external fixation, with the proximal ring secured to both the proximal epiphysis and metaphysis.
Conclusion
Slipped upper tibial epiphysis is an uncommon but distinct cause of tibia vara. The radiological features are completely different from those previously described for infantile tibia vara and not encompassed by the existing classification. The unusual morphology has consequences for treatment. Management is analogous to a slipped upper femoral epiphysis – the physis has to be stabilized to the metaphysis and an osteotomy performed to restore the mechanical axis. We believe this is best achieved with a circular external fixator because this permits multiaxial correction including translation and rotation.
