A novel geometrical planning method to restore knee joint obliquity in double-level osteotomies

PURPOSE: Precise preoperative planning is mandatory when a double-level osteotomy (DLO) is required to correct a severe knee deformity. Literature does not report a validated planning method regarding DLO that could be performed directly on digital radiographs using simple measurement tools. This study aims to validate a novel DLO planning method called New Mikulicz-Joint Line (NM-JL) based on essential measurement tools, in which the correction angles are induced by the predicted post-operative joint line obliquity (JLO). METHODS: Twenty-three patients who satisfied the inclusion criteria were enrolled. NM-JL planning method was performed using basic measurement tools to detect corrective angles and gaps. The correction was then simulated using a Virtual Segmentation Software method to obtain the osteotomy fragments. Both planning procedures were performed independently and later repeated by two orthopaedic surgeons to assess the inter and intra-observer reliability. RESULTS: The intraclass correlation coefficient (ICC) regarding corrective angles and gaps showed a significant positive correlation between the values determined using the two procedures by both raters (p < 0.05). Pearson’s correlation analysis revealed a significant correlation between the measured results of the two planning methods. (p < 0.05). Finally, the Bland–Altman analysis showed an excellent agreement (p < 0.05) for all measurements performed. CONCLUSIONS: The NM-JL method showed high values of intra and inter-rater reliability. The procedure is built up starting from the predicted value of post-operative joint line obliquity, allowing to maintain this parameter fixed. Other advantages include the quickness, adaptability, and possibility to be performed on any Digital Imaging and Communication in Medicine (DICOM) viewer. LEVEL OF EVIDENCE: Level IV. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00402-023-04997-6.