La distraction physaire est un décollement épiphysaire Salter et Harris 1, sans abord chirurgical, provoqué par l'intermédiaire d'un fixateur externe. L'apparition d'un régénérat permet les allongements et les corrections de déviations dans tous les plans, l'ajustement étant toujours possible pendant la correction chez un sujet debout en charge.

Vingt distractions physaires pour déviation axiale et/ou inégalité de longueur chez quinze patients d'âge moyen de 14,4 ans ont été analysées. Le site de distraction a été tibial proximal ou distal, fémoral distal et radial distal. Les fixateurs externes ont été mono-latéraux 11 fois, et circulaires 9 fois. Les complications on été classées selon Caton en quatre stades de gravité.

La date moyenne de la douleur due au décollement épiphysaire était de 7 jours, la correction angulaire moyenne de 22,2°, et l'allongement de 4,75 cm. Les complications restent fréquentes et prédominaient sur les localisations fémorales distales. Elles étaient bénignes dans 17 cas, sérieuses dans six cas et sévères dans deux cas (flessum du genou et équin de cheville).

La correction de la déformation se fait au niveau de son origine, le cartilage de croissance, et l'ouverture de la physe se produit même en présence d'un pont d'épiphysiodèse. Cette technique permet donc de se passer du temps de résection du pont d'épiphysiodèse proposé par Bollini, chez l'enfant de plus de 10 ans. Il faut considérer que le chondrodiastasis entraîne une stérilisation définitive du cartilage de croissance, et prendre en compte le potentiel de croissance perdu dans la correction.

Physeal distraction or chondrodiastasis uses the growth plate as a zone of least resistance. Application of force thus provokes distraction and opening of the plate (Salter and Harris type I epiphyseal detachment). Progressive lengthening allows room for regenerate bone and enables limb lengthening and correction of angular deformations.

Twenty chondrodiastasis procedures were performed in fifteen patients. Mean age was 14.4 years (10.3-15.7). The underlying causes were trauma (n = 6), constitutional deformation (n = 8), infection (n = 2, distal lateral femoral epiphysiodesis), and malformation (n = 4). The localizations were: proximal tibia (n = 11), distal tibia (n = 4), distal femur (n = 4), distal radius (n = 1). The surgical procedure involved installation of an external fixator on either side of the physis after planification of the desired correction and taking into account the remaining growth potential of the physis. The distraction was performed by the patient at the rate of 1 mm per day. A one-sided external fixator was used for eleven patients (distal femoral correction and proximal tibial hemichondrodiastasis for angular deformation) and a circular fixator (to control 3D correction) in nine. Complications were noted according to the four grades of severity described by Caton.

Mean follow-up was 26.1 months. Epiphyseal detachment was achieved in all patients, even in the presence of an epiphysiodesis bridge, in 7.7 days on average (2-15 days). Mean lengthening was 4.75 cm, mean angular correction was 22.2° (mean preoperative angle 20.5°). For chondrodiastasis (symmetrical physeal distraction), the mean duration of correction was 4.6 months (1-9), mean time to healing was 8.3 months (4-13) and mean healing index was 55.6 days/cm (Verone). For hemichondrodiastasis (asymmetrical physeal distraction), mean duration of correction was 1.3 months (1-3), and mean time to healing was 2.7 months (2-5). The healing index was different and was 3 days per degree. Complications were studied using the Caton classification. There were 17 (85%) benign complications (not requiring revision under anesthesia) and 6 (30%) serious complications (requiring anesthesia and unplanned revision). There were 2 (10%) severe complications (knee flexion, ankle equinus).

Chondrodiastasis has specific complications, mainly involving the distal femur (stiff knee, risk of septic arthritis). It provides rapid in situ correction resulting from epiphysiodesis bridges. The resection step proposed by Bollini is not necessary, but the growth plate is definitively sterilized. This implies that the procedure be used for preventive lengthening, depending on the predicted limb length discrepancy. This notion limits indications to older children. Besides the fact that several deformations can be corrected simultaneously, this technique does not require osteotomy and respects vascular supply to the regenerative tissue. It involves the physis responsible for the angular deformation or limb length discrepancy. It does not require internal fixation nor bone grafting and can be performed with weight bearing. Finally, the procedure can be adjusted as needed during the correction phase, with the patient in the standing position.