AN ASSESSMENT OF POSTNATAL-GROWTH AFTER IN-UTERO LONG-BONE OSTEOTOMY WITH FIXATION

Researchers have recently suggested that rigid fixation of the immatur e bony skeleton may restrict growth and development. This study assess es the effect on postnatal growth of an in utero tibial osteotomy fixe d with a miniplate in fetal sheep. A midshaft osteotomy was performed on fetal sheep tibia (n = 5) at 95 days' gestation (term 145 days). On e tibia was reduced and fixed with a titanium miniplate and screws, wh ile the contralateral hindlimb served as a control. The newborns were vaginally delivered and sacrificed at 2 months of age. The hindlimbs, control and fractured, were harvested, stripped of soft tissue, and th e tibia, femur, and distal metatarsal were each measured and weighed. Each tibia also underwent radiographic analysis and histologic examina tion (after decalcification) using hematoxylin and eosin, Sirius red, and Alcian blue stains. No prenatal, postnatal, or perioperative medic al complications occurred. Apart from a slight angulation in one opera ted tibia, no gross morphologic differences, either visible or palpabl e, were found between the operated and control limbs. This was confirm ed radiographically where no remnant of the osteotomy site was visible . Measurements of the operated and control tibias, femurs, and metatar sal bones were not statistically different. Histologic analysis showed a total incorporation of bone at the osteotomy site with appositional growth present. All bone was lamellar with longitudinal orientation. In the area of the screw sites, the surrounding bone shaft was the sam e width as its neighboring bone. Epiphyses also appeared normal. In ut ero long bone healing of a midshaft tibial osteotomy (nongrowth center ) with miniplate fixation does not appear to retard postnatal growth.