A coronal imaging classification of neurofibromatosis type Ⅰ with dystrophic upper thoracic scoliosis

English Keywords:Neurofibromatosis type Ⅰ  Dystrophic scoliosis  Upper thoracic scoliosis  Coronal classification  Reliability

English Abstract:

  【Abstract】 Objectives: To propose a coronal imaging classification of neurofibromatosis type Ⅰ with dystrophic upper thoracic scoliosis(DUTS-NF1), to verify its reliability and reproducibility, and to explore its clinical significance. Methods: We retrospectively analyzed the data of patients diagnosed with neurofibromatosis type Ⅰ with dystrophic spinal scoliosis in the database of our hospital from June 2009 to December 2023. The patients whose main curve apex located in the upper thoracic vertebrae(T1-T5) were screen out and were classified according to the coronal scoliosis pattern on standing spinal X-rays: Type A, shoulder-neck type; Type B, distal thoracic compensatory curve type; Type C, trunk inclination type. The Cobb angle, upper thoracic kyphosis angle, clavicle angle(CA), T1 tilt, neck tilt(NT), head shift(HS), coronal balanced distance(CBD), and deformity angular ratio(DAR) were measured and calculated for each type of patients. Three spine surgeons, who had been specially trained, independently performed two classifications according to the method. The results of the two classifications of the same observer were analyzed for reproducibility by applying the Kappa value, and the results of the classification were analyzed for confidence between different observers. Results: 29 patients(7.9%) with DUTS-NF1 were identified from the 367 NF1 patients with dystrophic scoliosis, and the main Cobb angle was 78.7°±12.9°. The classification results of the designer were 16 patients of type A, 8 of type B, and 5 of type C. The DAR of type B and type C was significantly higher than that of type A(20.6±2.2, 20.0±3.0 vs 13.2±1.8, P<0.001); Type C had more significant head and coronal shift distances than type A(HS: 27.6±11.7mm vs 13.5±6.7mm, P<0.001; CBD: 34.8±20.5mm vs 13.9±10.9mm, P<0.001); The T1 tilt of type C was significantly higher than that of type A（P<0.05）; The other imaging parameters were not statistically different between the three types(P>0.05). 174 times of classifications were performed by the 3 observers using the DUTS-NF1 coronal imaging classification method, including 96 classifications of type A, 45 classifications of type B, and 33 classifications of type C. The intra-observer classification concordance rate was(82.57±8.44)%, with a Kappa value of 0.771-0.81, which was considered to be "Basically reliable"; The inter-observer classification concordance rate was(84.19±8.65)%, with a Kappa value of 0.884-0.886, which was considered to be "Completely reliable". Conclusions: Based on the coronal imaging features, patients with DUTS-NF1 can be classified into three types of shoulder-neck type, distal thoracic compensatory curve type, and trunk inclination type. This classification system has satisfied reproducibility and reliability, which is helpful for assessing the coronal compensation of DUTS-NF1 patients, and thus guides the clinical diagnosis and treatment.