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A Novel Clinical Classification for Atlantoaxial Dislocation: Based on Surgical Outcomes of 1032 Cases
Xiangyang Ma1,2, Zexing Chen1,2, Xiaobao Zou1
1Department of Orthopedics, General Hospital of Southern Theater Command of PLA, Guangzhou, 510010, China.
Study Design:
A retrospective cohort study.
Objectives:
To propose a novel clinical classification system for atlantoaxial dislocation (AAD) that modifies and subclassifies existing systems.
Summary Of Background Data:
Driven by the controversial definition of irreducible atlantoaxial dislocation (IAAD) and recent advancements in reduction techniques, existing AAD classifications require modification to enhance their clinical applicability.
Methods:
We retrospectively reviewed 1032 patients diagnosed with AAD who had a minimum two-year follow-up. Clinical and neurological outcomes were assessed using the japanese orthopaedic association (JOA) score, while primary outcomes included reduction status, bone fusion, complications, and the change in atlantoaxial angle (ΔAAA). Beyond standard dynamic radiographs, CT, and skull traction assessments, a novel classification system was developed incorporating the ΔAAA. Furthermore, receiver operating characteristic (ROC) curve analysis was employed to establish the optimal ΔAAA cut-off value for subclassifying IAAD.
Results:
The cohort comprised 537 males and 495 females. Patients were classified into six types: 231 cases as Type I, 304 as Type II, 209 as Type III, 212 as Type IV, 49 as Type V, and 27 as Type VI. Except for three patients who died, the remaining 1029 patients were followed up for a mean of 33 months. Anatomical reduction was achieved in 661 patients, functional reduction in 324 patients, and partial reduction in 41 patients; six patients required odontoidectomy. At the last follow-up, the mean JOA score improved significantly from 12.40 ± 3.71 to 15.18 ± 2.32 (t=-35.714, P<0.001).
Conclusion:
In this novel system, AAD is classified into six subtypes: atlantoaxial instability (Type Ⅰ), reducible AAD (Type Ⅱ), IAAD is subdivided into traction-loosen (Type III) and traction-stable (Type IV) types, while the fixed atlantoaxial dislocation (FAAD) is categorized into limited fusion (Type V) and extensive fusion (Type VI) types. Consequently, surgical strategies can be optimized according to these specific subtypes.
