Posteromedial tibial deformity: Radiological evolution and treatment of the discrepancy

Postero-medial deformity (DMPT), unlike other congenital forms that affect the tibia, presents a good evolution spontaneously correcting the important misalignments that present at birth based on the classic orthopedic laws of Wolff and Hueter-Volkmann, leaving slight residual angulations and variable limb length discrepancy.

Authors carry out a retrospective review of cases diagnosed with DPMT, the evolution of the tibial angulation and the discrepancy in the length of fourteen patients (11 males and 3 females) followed and treated between the years 2003 and 2018. Seven of these were treated by callus distraction. We have considered: PA and lateral of the tibia and stand-up entire limbs x-ray during age growth, along with the clinical records of the patients.

The medial diaphyseal radiological deformity of the newborn or neonatal period was 34° and the final 10°. The posterior deformity evolved from 46° to a final angulation of 11°. The physeal angulation in the initial AP projection was 34° and the end view was 8° and in the lateral projection from 44 to 6°. The mechanical axis of the limb was correcting towards a neutral axis in relation to the aforementioned physeal and diaphyseal correction in all cases except two. In five of the cases, although the mechanical axis was normal-aligned, at the tibial level it ran eccentrically and externally to the tibial cortex. The length relationship between the short tibia and the healthy tibia maintains a constant proportion throughout the growth of 89%, that is, the inhibition of growth is 11%. We observe that 80% of the discrepancy is found in the tibia and that the remaining 20% ??was exposed from the height of the tarsus. Two patients presented a traumatic and accidental diaphyseal fracture of the tibia. The difference in the length of the tibia was compensated to seven patients by callus distraction of 5.4cm using the callotasis method with a Healing Index of 34.5 days/cm.

DPMT improves substantially during the first years of life. Joint alignment of the knee and ankle is achieved before the correction of diaphyseal deformity. The tibia length discrepancy increases with the growth of the child since there is an 11% growth inhibition that will cause a skeletal maturity discrepancy between 4-7cm. Callus distraction before skeletal maturity is the method chosen to compensate this discrepancy.