Related Basic Research On The Phenomenon Of Thoracic Hypokyphosis In Adolescent Idiopathic Scoliosis And Its Clinical Significances

Chapter 1 Association between a Promoter Polymorphism of Tissue Inhibitor of Metalloproteinase-2 (TIMP-2) Gene and Adolescent Idiopathic ScoliosisObjective. To determine whether a promoter polymorphism of TIMP-2 gene correlates with the occurrence and curve severity of AIS.Methods. This study included a total of 570 female AIS patients, who were divided into two groups according to the curve patterns.354 patients with right thoracic curve were in group A (326 cases with Lenke 1 type and 28 cases with Lenke 2 type), while 216 patients with a single lumber curve were in group B (216 cases with Lenke 5 type).210 age-matched healthy girls were recruited as normal controls. One SNP-418G/C (rs8179090) in the promoter region were selected for TIMP-2 gene. Genotyping was performed by PCR-restriction fragment length polymorphism in each group respectively.Results. No significant differences of genotype and allele frequency distributions between AIS patients and normal controls were found either in group A or in group B. The frequency of C allele was significantly higher in patients with Cobb angle≥40° when compared with those with Cobb angle<40° in group A (P<0.05), while this difference was not noted in group B (P>0.05). Among the patients who reached skeletal maturity without any interference of natural history, significantly higher average maximum Cobb angle was found in patients with C allele when compared with those without C allele in group A (P<0.05). However, in group B, the mean maximum Cobb angle were similar between patients with different genotypes in both cases with left-side curves and cases with right-side curves (P>0.05). Furthermore, for the patients whose values of thoracic kyphosis (TK) were recorded, those with C allele had smaller average TK than those without C allele in Group A (P<0.05). However, such significant difference was not observed in Group B.Conclusions. The SNP-418G/C (rs8179090) in the promoter region of TIMP-2 gene was not associated with the occurrence of AIS. However, it may predict curve severity of thoracic AIS.Hence, TIMP-2 gene is a disease-modifier gene of thoracic AIS.Chapter 2 Comparison of the sagittal profiles between thoracic idiopathic scoliosis patients with different curve progressionObjectives:To compare the sagittal profiles between thoracic idiopathic scoliosis (IS) patients with different curve progression and to determine the risk factors associated with curve progression.Methods:A total of 83 thoracic IS patients were included in this study and were divided into 3 groups according to different curve progression. All the patients did not receive any previous treatments so that the natural histories of the curve developments were not disturbed. There were 26 skeletally mature patients (Risser sign=5 degree) with Cobb angle< 40° in non-curve progression group (NCP group),29 mature patients with Cobb angle>40° in moderate curve progression group (MCP group) and 28 immature patients (Risser sign< 3 degree) with Cobb angle>40° in severe curve progression group (SCP group). Five sagittal parameters, including thoracic kyphosis, lumbar lordosis, sacral slope, pelvic incidence and pelvic tilt were measured on the lateral X-ray films. Analysis of variance was used to compare these parameters between the 3 groups.Results:The average thoracic Cobb angle was significantly smaller in NCP group when compared with MCP group and SCP group (p<0.05), but not significantly different between the 2 latter groups (p>0.05).The average TK was 19.0°±7.0° in NCP group,12.7°±■6.2° in MCP group and 8.5°±■4.6° in SCP group. The average TK was significantly smaller in SCP groups when compared with MCP group or NCP group (p<0.05) while the average TK was significantly smaller in MCP group when compared with NCP group (p<0.05). None of the other 4 parameters showed any significant difference between the 3 groups (p>0.05).Conclusion:Thoracic hypokyphosis was found to be a risk factor related to curve progression in thoracic IS patients. Sagittal pelvic profile may not be involved in the underlying mechanism of curve progression in thoracic IS patients.Chapter 3 The changed relative position of trachea in the proximal thoracic curve of patients with adolescent idiopathic scoliosis:A computed tomography studyObjectives:To determine the changed relative position of trachea to spine in the proximal thoracic curve (T1-T4) and to analyze potential risk of tracheal injury from pedicle screw insertion in AIS patients.Methods:Twenty patients with complete proximal thoracic curve (CPT group), twenty-two patients with fractional proximal thoracic curve (FPT group) and fourteen normal patients with a straight spine (normal group) were included. Axial computed tomography images from T1 to T4 level of all subjects were analyzed with respect to the following parameters:(1) trachea-vertebral angle (TVA, defined as 0° when the trachea was located directly lateral to the left and 180° when directly lateral to the right), (2) trachea-vertebral distance (TVD, the closet distance between trachea and vertebral body). The percentages of trachea located adjacent to vertebrae and in the direction of screw passage were calculated to analyze potential risks of tracheal injuries during screw insertion.Results:The average TVA in CPT group was significantly larger than that in FPT group and normal group (P<0.05) while the TVA in FPT group was significantly larger than that in normal group (P<0.05) at T2 to T4 level. The TVD in FPT group was significant smaller than that in CPT group and normal group (P<0.05) at each level while the TVD in CPT group was significantly smaller than that in normal group (P<0.05) at T2 and T3 levels. In FPT group, the percentage of trachea at risk of injury from right screw insertion was 36.7% at T1 level,95.5% at T2 level,100% at both T3 and T4 levels. No trachea was found to be at risk of injury from left screw insertion in FPT group. Trachea was safe from screw insertion on both two sides in both CPT group and normal group.Conclusions:The trachea is positioned much closer to the proximal thoracic vertebrae in AIS patients with fractional PT curve when compared with patients with complete PT curve and normal patients. This position places the trachea at a high risk of injury from anterior cortex penetration during right pedicle screw insertion in the proximal thoracic region.