Intraoperative alignment goals for distinctive sagittal morphotypes of severe cervical deformity to achieve optimal improvements in health-related quality of life measures

Background Context: Patients with severe cervical deformity (CD) often have profound deficits in numerous activities of daily living. The association between health status and postoperative radiographic goals is difficult to quantify. Purpose: We aimed to investigate the radiographic characteristics of patients who achieved optimal health related quality of life scores following surgery for CD. Study Design: We performed a retrospective review of a prospectively collected database of patients with spinal deformity. Patient Sample: One hundred and fifty-three patients with cervical deformity Outcome Measures: Common health-related quality of life scores (HRQOLs) measurements were taken for patients treated operatively for cervical deformity including neck disability index (NDI), modified Japanese Orthopaedic Association scale (mJOA) for myelopathy and numeric rating scale for neck pain (NRS-neck), Methods: Surgical patients with severe CD were isolated based upon a previously presented discriminant analysis which outlined a combination of preoperative cervical sagittal vertical axis (cSVA), T1 slope, maximum focal kyphosis in extension, C2 slope in extension, and number of kyphotic levels in extension. Those with available preoperative and 1-year postoperative HRQL data were included. Based on a previous study, patients were grouped into three distinct sagittal morphotypes of CD: focal deformity (FD), flat neck (FN = large TS-CL and lack of compensation), or cervicothoracic (CT). Postoperative outcomes were defined as “good” if a patient had ≥2 of the three following criteria (1) NDI <20 or meeting MCID, (2) mild myelopathy (mJOA≥14), and (3) NRS-Neck ≤5 or improved by ≥2 points from baseline. Within each distinct deformity group, patients with good outcomes were compared to those with poor outcomes (ie, not meeting the criteria for good) for differences in demographics, HRQOL scores, and alignment, via Chi-squared or student's t tests. Results: Overall, 83 of 153 patients met the criteria of severe CD and 40 patients had complete 1-year follow-up of clinical/radiographic data. Patient breakdown by deformity pattern was: CT (N=13), FN (N=17), and FD (N=17), with 7 patients meeting criteria for both FD and FN deformities. Within the FD cohort, maximal focal kyphosis (ie, kyphosis at one level) was better corrected in patients with a “good” outcome (p=.03). In the FN cohort, patients with “good” outcomes presented preoperatively with worse horizontal gaze (McGregor Slope 21° vs. 6°, p=.061) and cSVA (72 mm vs. 60 mm, p=.030). “Good” outcome FN patients showed significantly greater postop correction of horizontal gaze (-25° vs. -5°, p=.031). In the CT cohort, patients with “good” outcomes had superior global alignment both pre- (SVA: -17 mm vs. 108 mm, p<.001) and postoperatively (50 mm vs. 145 mm, p=.001). CT patients with “good” outcomes also had better postop cervical alignment (cSVA 35 mm vs. 49 mm, p=.030), and less kyphotic segments during extension (p=.011). In the FD cohort, there were no differences between “good” and “poor” outcomes patients in preoperative alignment; however, “good” outcome patients showed superior changes in postoperative focal kyphosis (−2° vs. 5°, p=.030). Within all three deformity pattern categories, there were no differences between “good” and “poor” outcome patients with respect to demographics or surgical parameters (levels fused, surgical approach, decompression, osteotomy, all p>.050). Conclusions: The results of this study show each CD patient's unique deformity must be carefully examined in order to determine the appropriate alignment goals to achieve optimal HRQOLs. In particular, the recognition of the sagittal morphotype can help assist surgeons to aim for specific alignment goals for CT, FN and FD. Distinct deformity specific intra-operative goals include obtaining proper sagittal global/cervical alignment for cervicothoracic patients, correcting maximal focal kyphosis in focal deformity patients, and correcting horizontal gaze for flatneck patients.