Analysis of cervical sagittal alignment change following correction of thoracic and thoracolumbar Scheuermann's kyphosis.

PURPOSE: To analyse pre-operative and post-operative changes of cervical sagittal alignment (CSA) in Scheuermann's kyphosis (SK) patients. METHODS: 64 SK and 33 control patients were retrospectively reviewed. Whole spine X-rays obtained at pre-op, 3 months post-op and at latest follow-up were reviewed and ten separate CSA radiological parameters were measured. Patients were divided in three groups: thoracic SK (TK group, apex T6-T9, n = 40), thoracolumbar SK (TLK group, apex T10-T12, n = 24), and controls. RESULTS: Pre-operative C2-C7 lordosis was 21.1° ± 8.1°(TK), 6.1° ± 5.0°(TLK), and 11.4° ± 8.3° in control group and correlated significantly with T1 slope in both SK groups (r = 0.640, r = 0.772). Pre-operative T1 slope was dependent on deformity type, thoracic kyphosis (TK, ß = 0.445), and lumbar lordosis (LL, ß = -0.354). At final follow-up C2-C7 lordosis decreased to 15.7° ± 5.5° in TK, and increased to 12.1° ± 4.1° in TLK group. C2-C7 lordosis changes linearly correlated with T1 slope changes post-operatively (r = 0.721). Post-operative T1 slope showed linear correlation with post-operative changes in TK (ß = 0.728) and pelvic tilt (PT, ß = 0.539) in TK, and LL (ß = -0.669), thoracolumbar kyphosis (TLK, ß = -0.434), and PT (ß = 0.760) in TLK group. CONCLUSIONS: Our study suggests that SK is not a homogenous group of patients. Two patterns of pre- and post-operative CSA are demonstrated in TK and TLK groups. T1 slope is the most important parameter in determining pre-operative CSA and correlates with other regional anatomical parameters (TK and LL). Post-operative CSA adaptations also correlate with T1 slope post-operative changes. However, post-surgical T1 slope correlates with different parameters in the two SK groups (TK and PT in TK group; TLK, LL, and PT in TLK group).

Correlation between preoperative spinopelvic alignment and risk of proximal junctional kyphosis after posterior-only surgical correction of Scheuermann kyphosis.

BACKGROUND CONTEXT: Surgical correction of Scheuermann kyphosis (SK) is challenging and plagued by relatively high rates of proximal junctional kyphosis and failure (PJK and PJF). Normal sagittal alignment of the spine is determined by pelvic geometric parameters. How these parameters correlate with the risk of developing PJK in SK is not known. PURPOSE: The study aimed to investigate the relationship between preoperative and postoperative spinopelvic alignment and occurrence of PJK and PJF. STUDY DESIGN/SETTING: This is a retrospective observational cohort study. PATIENT SAMPLE: The sample included 37 patients who underwent posterior correction of SK from January 2006 to December 2012. OUTCOME MEASURES: The outcome measure was correlation analysis between preoperative and postoperative spinopelvic alignment parameters and the development of PJK over the course of the study period. METHODS: Whole spine x-rays obtained before surgery, 3 months after surgery, and at the latest follow-up were analyzed. The following parameters were measured: thoracic kyphosis (TK), lumbar lordosis (LL), sagittal vertical axis (SVA), pelvic incidence (PI), pelvic tilt (PT), and sacral slope (SS). The development of PJK was considered the primary end point of the study. Patient population was split into a control and a PJK group; repeated-measures analysis of variance was used to assess group and time differences. RESULTS: Seven patients developed PJK over the study period. Although the severity of the preoperative deformity (TK) did not differ significantly between the two groups, preoperative PI was significantly higher in the PJK group (51.9°C±8.6°C vs. 42.7°C±8.8°C, p=.018). Postoperative correction of TK was similar between the two groups (39.3% and 41.2%, p=.678) and final LL did not differ as well (53.6°C±9.2°C vs. 51.3°C±11.5°C). However, because PJK patients had larger preoperative PI values, a significant deficit of LL was observed at final follow-up in this group compared with the control group (ΔLL -10.5°C±9.8°C vs. 0.6°C±10.5°C, p=.013). CONCLUSIONS: Scheuermann kyphosis patients who developed PJK appeared to have a significant postoperative deficit of LL (lumbopelvic mismatch). Lumbar lordosis decreases after surgery following correction of TK; therefore, TK correction should be planned according to preoperative PI values to avoid excessive reduction of LL in patients with higher PI values.