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Background. Rib head dislocation (RHD) in dystrophic scoliosis of type 1 neurofibromatosis (DS-NF1) is a unique disorder caused by skeletal dystrophy and scoliotic instability. No particular surgical manipulation is mentioned in the literature to instruct the spine surgeons to effectively obtain more migration of the dislocated rib head without resection. The present study aimed to investigate the effectiveness of screw/hook insertion at vertebrae with RHDs on the retraction of penetrated rib head from spinal canal.Methods. 37 neurologically intact patients with DS-NF1 and concomitant 53 RHDs undergoing scoliosis surgery without rib head excision were retrospectively reviewed. We used pre and postoperative whole-spine radiographs to determine the Cobb angle and the vertebral translation (VT), and the CT scans to evaluate the intraspinal rib length (IRL) and rib-vertebral angle (RVA). The dislocated ribs were stratified into two groups according to the presence of screw/hook insertion at vertebrae with RHD: screw/hook group and non-screw/hook group. Results. 37 dislocated ribs with screws/hooks insertion at corresponding vertebrae were assigned into the screw/hook group and the remaining 16 dislocated ribs consisted of the non-screw/hook group. In the screw/hook group, the correction rates of Cobb angle and VT were significantly higher than the non-screw/hook group after surgery (58.7±16.0% vs. 30.9±12.4%, p=0.003; 61.8±18.8% vs. 35.1±16.6%, p=0.001; respectively). Similarly, more correction rates of IRL and RVA were found in the screw/hook group than the non-screw/hook group (63.1±31.3% vs. 30.1±20.7%, p=0.008; 17.6±9.7% vs. 7.2±3.6%, p=0.006; respectively). Multiple linear regression analysis revealed that the correction rates of Cobb angle, VT and RVA contributed significantly to correction of IRL (β=0.389, 0.939 and 1.869, respectively; p=0.019, 0.001 and 0.002, respectively).Conclusion. Screw/hook insertion at dystrophic vertebrae with RHDs contributed significantly to the degree of retraction of penetrated rib head from spinal canal. This effectiveness is mediated by more corrections of VT and RVA.

Background. There was a paucity of valid information on how to discriminate between different patterns of convex coronal imbalance (CCI>3cm) in dystrophic scoliosis secondary to Type I neurofibromatosis (DS-NF1), while aggravated postoperative CCI occurred regularly with the causes being insufficiently investigated. We aimed to develop a new classification of CCI in DS-NF1, and to optimize the coronal rebalancing strategies.Methods. NF1-related scoliosis database was reviewed and different types of CCI were identified, and the outcomes of coronal rebalance were analyzed. Results. Two main CCI patterns were defined: thoracic CCI (Type 1) and thoracolumbar/lumbar CCI (Type 2), and were further subtyped by the compensatory behavior of the upper hemi-curve (straight or curved morphology). The incidence of immediate post-op CCI was 0.0% and 63.6% for Type1 and Type 2 groups, respectively. Mismatch of both translation and inclination correction between the upper and lower hemi-curve was significant in the post-op coronal imbalanced group (△Upper Arc Translation/△Lower Arc Translation: 109.6±60.0% vs. 31.8±34.4%, p=0.008; △Upper Arc Inclination/△Lower Arc Inclination: 89.8±36.6% vs. 33.5±37.3%, p=0.012). Multiple linear regression analysis revealed that △UAT/△LAT significantly correlated with the correction of coronal balance distance (β=-21.567; p=0.018). A surgical rebalancing algorithm was proposed to treat each subtype.Conclusion. Thoracolumbar/lumbar CCI in dystrophic scoliosis was prone to suffer high risk of persistent post-op CCI. Satisfying coronal rebalance should rely on maximal translational correction of lower hemi-curve, while the upper hemi-curve played the role of fine-tuning for coronal realignment rather than radical Cobb correction, straight morphology in particular.