The "6 Plate": A Novel Open Device for Rotational Guided Growth-A Pilot Research in the Ovine Femur.

Introduction: Guided growth is currently the gold standard technique for manipulating the physis to correct deformities in the coronal and sagittal planes in immature patients. The aim of this study is to evaluate a novel guided growth system in the axial plane. Materials and methods: This prospective animal study utilized a device consisting of a double epiphyseal fixation plate ("6 Plate") designed to convert longitudinal physeal growth into rotational movement. The device was applied to the left distal femur of six immature lambs (aged 3 months), with the right femur serving as control. At 120 days postoperatively, animals were sacrificed, and both femurs were extracted for comparative macroscopic, radiological (plain radiography and CT scan), and morphometric analysis, assessing length, rotation, and morphology. Additionally, a comparative histopathological study of the distal femoral physis was performed. Results: All lambs tolerated the surgical procedures and completed the study, with no significant complications. Surgical technique was deemed correct in four cases (three with open surgery and one with minimally invasive surgery [MIS]). Four of the six femurs showed external rotation, with a mean of 10.1° (range: 0.5°-21.3°), with greater rotation observed in open surgery cases. The two femurs operated on with minimally invasive techniques, both considered suboptimal, exhibited minimal (0.5°) or no external rotation. No significant femoral discrepancies or structural physis damage were detected during follow-up. No other notable complications were observed. Discussion and conclusions: This pilot study suggests that the implant could achieve external rotation of the femur with minimal complications. The results appear to be linked to the appropriate technical execution of the procedure. Being an open system, it minimizes physeal blockage, thereby allowing satisfactory growth of the treated femurs. Key Concepts: (1)Rotational malalignment is a common problem in children for which the only effective solution is derotational osteotomy with internal fixation.(2)We designed a new implant that corrects rotational deformities in vitro using guided growth principles.(3)The present study tests this experimental design in large animals.(4)Rotational correction was achieved in 4 of 6 animals with no major complications. Level of Evidence: Level III.