West Lake Staging: A New Staging System Orchestrated by X-Ray and MRI on Knee Osteoarthritis
Abstract Background: Although widely used of Kellgren - Lawrence (KL) staging system on knee osteoarthritis (KOA), it still had some disadvantages. The purpose of this study was to investigate the differences on X-ray and MRI among each stage of KOA and further propose a new staging system called West Lake (WL) staging.Methods: A cross-sectional study was conducted on patients with KOA. KL stages were defined by two qualified orthopedic surgeons. Joint space widths (JSW) were measured on X-rays, whereas cartilage injuries (CI) and bone marrow lesions (BML) were evaluated on MRI. The differences of them across the groups were calculated by T-test. Receiver operating characteristic (ROC) curves were rendered to obtain the areas under the curves (AUC), Youden index and corresponding cut-off points. Agreement Index (KAPPA) was used to analyze the consistency of KL stages and WL stages assessed by two qualified orthopedic surgeons. Results: Eventually, a total of 220 patients met the criteria. There were significant differences on JSW, CI and BML between KL II/III as well as KL III/IV. In KL II/III, the AUC of JSW, CI, BML was 0.99, 0.76, 0.71 and the Youden index was 0.94, 0.38, 0.45, meanwhile the cut-off points were £5.1mm, >1, >2. In KL III/IV, the AUC of JSW, CI, BML was 0.96, 0.79, 0.74 and the Youden index was 0.84, 0.58, 0.38, meanwhile the cut-off points were £3.2mm, >3, >4. The Kappa coefficients of KL stages and WL stages were 0.31 and 0.76.Conclusion: The WL staging was described as follows: Grade 0, normal X-ray. Grade 1, X-ray shows osteophyte but no joint space narrow, normal MRI or MRI shows cartilage degeneration and only 1 or 2 sections are involved in BML. Grade 2, X-ray shows joint space narrow, MRI shows cartilage defect but no full-thickness cartilage defect, meanwhile 3 or 4 sections are involved in BML. Grade 3, X-ray shows serious joint space narrow even JSW disappeared, MRI shows full-thickness cartilage defect, more than 4 sections are involved in BML.Trial registration: The study was approved by the First Affiliated Hospital of Zhejiang Chinese Medical University (2018-ZX-026-01).