Is Central Sacral Vertical Line (CSVL) Reliable for Level Selection in AIS Patients with Axial Pelvic Rotation?
Abstract
Introduction and Objective. Central Sacral Vertical Line (CSVL) is traditionally utilized to determine the Stable Vertebrae (SV) in scoliosis in pre-operative planning. Axial Pelvic rotation (APR) in patients with AIS can affect the position of SV based on CSVL. The purpose of this study is to investigate the reliability of CSVL in AIS patients with APR to help further guide pre-operative planning in the selection of the appropriate lower instrumented vertebra. Methods. A single-center retrospective review of 111 patients with AIS and 50 non-scoliotic patients (≤ 18 yrs) was conducted. Following radiographic parameters were measured: left and right iliac wing length (distance between ASIS and inferomedial corner of SI joint), distance from left ASIS to mid-pelvic vertical line (MPVL, mid-point of distance between left and right ASIS), CSVL, symphysis pubis vertical line (SPVL), central hip vertical line (CHVL- vertical line bisecting the line joining the centers of the femoral heads). Axial pelvic rotation (APR) was determined indirectly by the left to right iliac wing ratio (LRIWR). Two cohorts were defined: Minimal APR: 0.8 > LRIWR < 1.2 and moderate APR: LRIWR < 0.8/ LRIWR > 1.2. Mean differences between MPVL and CSVL, SPVL and CHVL were calculated and compared respectively using ANOVA (SciPy ver.1). Results. AIS Cohort: 77 patients had LRIWR < 1 and 34 had the ratio > 1. In patients with LRIWR between 0.8 and 1, no difference was noted between MPVL and CSVL, SPVL and CHVL (p> 0.05 for all). In patients with LRIWR < 0.8, significant differences were noted between MPVL and CSVL (10mm, p= 0.04), CSVL and SPVL (10mm, p=0.04, Figure 1). In patients with LRIWR > 1.2, the difference between CSVL and MPVL was 9 mm (p = 0.14), between CSVL and SPVL was 4 mm (p = 0.69) and between CSVL and CHVL was 2 mm (p = 0.45). Non-Scoliosis Cohort: In non-scoliotic cohort, 30 patients (60%) patients had LRIWR < 1 and 20 (40%) had the ratio > 1. Only 4% of cases had LRIWR < 0.8. No significant differences between above mentioned lines noted in LRIWR > 0.8 and < 0.8. Conclusions-Implications. In patients with moderate pelvic rotation (LRIWR < 0.8), there is a significant difference between CSVL, MPVL and SPVL. Our data suggests that CSVL is not a reliable indicator for determining stable vertebra in patients with AIS with axial pelvic rotation.
Keywords
AIS, scoliosis, axial pelvic rotation
Presentation Type
Oral Presentation
Is Central Sacral Vertical Line (CSVL) Reliable for Level Selection in AIS Patients with Axial Pelvic Rotation?
Introduction and Objective. Central Sacral Vertical Line (CSVL) is traditionally utilized to determine the Stable Vertebrae (SV) in scoliosis in pre-operative planning. Axial Pelvic rotation (APR) in patients with AIS can affect the position of SV based on CSVL. The purpose of this study is to investigate the reliability of CSVL in AIS patients with APR to help further guide pre-operative planning in the selection of the appropriate lower instrumented vertebra. Methods. A single-center retrospective review of 111 patients with AIS and 50 non-scoliotic patients (≤ 18 yrs) was conducted. Following radiographic parameters were measured: left and right iliac wing length (distance between ASIS and inferomedial corner of SI joint), distance from left ASIS to mid-pelvic vertical line (MPVL, mid-point of distance between left and right ASIS), CSVL, symphysis pubis vertical line (SPVL), central hip vertical line (CHVL- vertical line bisecting the line joining the centers of the femoral heads). Axial pelvic rotation (APR) was determined indirectly by the left to right iliac wing ratio (LRIWR). Two cohorts were defined: Minimal APR: 0.8 > LRIWR < 1.2 and moderate APR: LRIWR < 0.8/ LRIWR > 1.2. Mean differences between MPVL and CSVL, SPVL and CHVL were calculated and compared respectively using ANOVA (SciPy ver.1). Results. AIS Cohort: 77 patients had LRIWR < 1 and 34 had the ratio > 1. In patients with LRIWR between 0.8 and 1, no difference was noted between MPVL and CSVL, SPVL and CHVL (p> 0.05 for all). In patients with LRIWR < 0.8, significant differences were noted between MPVL and CSVL (10mm, p= 0.04), CSVL and SPVL (10mm, p=0.04, Figure 1). In patients with LRIWR > 1.2, the difference between CSVL and MPVL was 9 mm (p = 0.14), between CSVL and SPVL was 4 mm (p = 0.69) and between CSVL and CHVL was 2 mm (p = 0.45). Non-Scoliosis Cohort: In non-scoliotic cohort, 30 patients (60%) patients had LRIWR < 1 and 20 (40%) had the ratio > 1. Only 4% of cases had LRIWR < 0.8. No significant differences between above mentioned lines noted in LRIWR > 0.8 and < 0.8. Conclusions-Implications. In patients with moderate pelvic rotation (LRIWR < 0.8), there is a significant difference between CSVL, MPVL and SPVL. Our data suggests that CSVL is not a reliable indicator for determining stable vertebra in patients with AIS with axial pelvic rotation.