Do the newly proposed realignment targets for C2 and T1 slope bridge the gap between radiographic and clinical success in corrective surgery for adult cervical deformity?

Abstract

OBJECTIVE Surgical correction of cervical deformity (CD) has been associated with superior alignment and functional outcomes. It has not yet been determined whether baseline or postoperative T1 slope (T1S) and C2 slope (C2S) correlate with health-related quality-of-life (HRQoL) metrics and radiographic complications, such as distal junctional kyphosis (DJK) and distal junctional failure (DJF). The objective of this study was to determine the impact of T1S and C2S deformity severity on HRQoL metrics and DJF development in patients with CD who underwent a cervical fusion procedure. METHODS All operative CD patients with upper instrumented vertebra above C7 and preoperative (baseline) and up to 2-year postoperative radiographic and HRQoL data were included. CD was defined as meeting at least one of the following radiographic parameters: C2–7 lordosis < −15°, TS1–cervical lordosis mismatch > 35°, segmental cervical kyphosis > 15° across any 3 vertebrae between C2 and T1, C2–7 sagittal vertical axis > 4 cm, McGregor’s slope > 20°, or chin-brow vertical angle > 25°. Spearman’s rank-order correlation and linear regression analysis assessed the impact of T1S and C2S on HRQoL metrics (Neck Disability Index [NDI], modified Japanese Orthopaedic Association [mJOA] scale, EuroQOL 5-Dimension Questionnaire [EQ-5D] visual analog scale [VAS] score, and numeric rating scale [NRS]–neck) and complications (DJK, DJF, reoperation). Logistic regression and a conditional inference tree (CIT) were used to determine radiographic thresholds for achieving optimal clinical outcome, defined as meeting good clinical outcome criteria (≥ 2 of the following: NDI < 20 or meeting minimal clinically important difference, mild myelopathy [mJOA score ≥ 14], and NRS-neck ≤ 5 or improved by ≥ 2 points), not undergoing reoperation, or developing DJF or mechanical complication by 2 years. RESULTS One hundred five patients with CD met inclusion criteria. By surgical approach, 14.7% underwent an anterior-only approach, 46.1% a posterior-only approach, and 39.2% combined anterior and posterior approaches. The mean baseline radiographic parameters were T1S 28.3° ± 14.5° and C2S 25.9° ± 17.5°. Significant associations were found between 3-month C2S and mJOA score (r = −0.248, p = 0.034), NDI (r = 0.399, p = 0.001), EQ-5D VAS (r = −0.532, p < 0.001), NRS-neck (r = 0.239, p = 0.040), and NRS-back (r = 0.264, p = 0.021), while significant correlation was also found between 3-month T1S and mJOA score (r = −0.314, p = 0.026), NDI (r = 0.445, p = 0.001), EQ-5D VAS (r = −0.347, p = 0.018), and NRS-neck (r = 0.269, p = 0.049). A significant correlation was also found between development of DJF and 3-month C2S (odds ratio [OR] 1.1, 95% confidence interval [CI] 1.01–1.1, p = 0.015) as well as for T1S (OR 1.1, 95% CI 1.01–1.1, p = 0.023). Logistic regression with CIT identified thresholds for optimal outcome by 2 years: optimal 3-month T1S < 26° (OR 5.6) and C2S < 10° (OR 10.4), severe 3-month T1S < 45.5° (OR 0.2) and C2S < 38.0° (no patient above this threshold achieved optimal outcome; all p < 0.05). Patients below both optimal thresholds achieved rates of 0% for DJK and DJF, and 100% met optimal outcome. CONCLUSIONS The severity of CD, defined by T1S and C2S at baseline and especially at 3 months, can be predictive of postoperative functional improvement and occurrence of worrisome complications in patients with CD, necessitating the use of thresholds in surgical planning to achieve optimal outcomes.

Highest Achievable Outcomes for Patients Undergoing Cervical Deformity Corrective Surgery by Frailty

“…Many CD classifications have been proposed to address this issue, but the disassociation between these 2 prominent outcomes continues to riddle the spine surgeon. 22,27-30 Our study concluded NF patients demonstrated equivocal mean improvement in NDI by 2 years, despite experiencing the least amount of improvement in 2 of the 3 radiographic modifiers. Furthermore, they also had the highest rates of deterioration in the horizontal modifier by 2 years.…”

Clinical Impact and Correlations of Odontoid Parameters Following Multilevel Posterior Cervical Fusion Surgery

“…The patient's compensation to maintain a horizontal gaze may be represented by C2S. 11 Incremental inclination is represented by C2S, which reflects the need for more extension of the upper cervical spine. Thus, the capacity to extend the upper cervical spine is related to a patient's ability to maintain the horizontal gaze during cervical malalignment.…”

“…C2S presents a simplified understanding of cervical alignment and is suggested as a unified key to understanding cervical alignment relative to the thoracic spine. 11 OT, like PT, denotes the spatial orientation of the dens, which may vary according to the balance of the cranium and horizontal gaze. OI, like PI, is related to the compensatory reservoir of cervical extension.…”

“…10 Functional improvement in patients with cervical deformity and the likelihood of achieving optimal outcomes can be predicted with C2S. 11 Nonetheless, unlike the pelvic parameters, C2S is limited in that it is a positional parameter based only on the horizontal axis. The optimal range of C2S may vary among individuals, as the thoracolumbar positional parameters differ between individuals depending on PI.…”

“…To simplify the assessment of cervical malalignment, a novel parameter—C2 slope (C2S), which is mathematically approximated as T1S–CL—has been proposed [ 10 ]. Functional improvement in patients with cervical deformity and the likelihood of achieving optimal outcomes can be predicted with C2S [ 11 ]. Nonetheless, unlike the pelvic parameters, C2S is limited in that it is a positional parameter based only on the horizontal axis.…”