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Peter G. Passias, Haddy Alas, Sara Naessig, Han Jo Kim, Renaud Lafage, Christopher Ames, Eric Klineberg, Katherine Pierce, Waleed Ahmad, Douglas Burton, Bassel Diebo, Shay Bess, D. Kojo Hamilton, Munish Gupta, Paul Park, Breton Line, Christopher I. Shaffrey, Justin S. Smith, Frank Schwab, Virginie Lafage, and the International Spine Study Group

OBJECTIVE

The goal of this study was to assess the conversion rate from baseline cervical alignment to postoperative cervical deformity (CD) and the corresponding proximal junctional kyphosis (PJK) rate in patients undergoing thoracolumbar adult spinal deformity (ASD) surgery.

METHODS

The operative records of patients with ASD with complete radiographic data beginning at baseline up to 3 years were included. Patients with no baseline CD were postoperatively stratified by Ames CD criteria (T1 slope–cervical lordosis mismatch [TS-CL] > 20°, cervical sagittal vertical axis [cSVA] > 40 mm), where CD was defined as fulfilling one or more of the Ames criteria. Severe CD was defined as TS-CL > 30° or cSVA > 60 mm. Follow-up intervals were established after ASD surgery, with 6 weeks postoperatively defined as early; 6 weeks–1 year as intermediate; 1–2 years as late; and 2–3 years as long-term. Descriptive analyses and McNemar tests identified the CD conversion rate, PJK rate (< −10° change in uppermost instrumented vertebra and the superior endplate of the vertebra 2 levels superior to the uppermost instrumented vertebra), and specific alignment parameters that converted.

RESULTS

Two hundred sixty-six patients who underwent ASD surgery (mean age 59.7 years, 77.4% female) met the inclusion criteria; 103 of these converted postoperatively, and the remaining 163 did not meet conversion criteria. Thirty-eight patients converted to CD early, 26 converted at the intermediate time point, 29 converted late, and 10 converted in the long-term. At conversion, the early group had the highest mean TS-CL at 25.4° ± 8.5° and the highest mean cSVA at 33.6 mm—both higher than any other conversion group. The long-term group had the highest mean C2–7 angle at 19.7° and the highest rate of PJK compared to other groups (p = 0.180). The early group had the highest rate of conversion to severe CD, with 9 of 38 patients having severe TS-CL and only 1 patient per group converting to severe cSVA. Seven patients progressed from having only malaligned TS-CL at baseline (with normal cSVA) to CD with both malaligned TS-CL and cSVA by 6 weeks. Conversely, only 2 patients progressed from malaligned cSVA to both malaligned cSVA and TS-CL. By 1 year, the former number increased from 7 to 26 patients, and the latter increased from 2 to 20 patients. The revision rate was highest in the intermediate group at 48.0%, versus the early group at 19.2%, late group at 27.3%, and long-term group at 20% (p = 0.128). A higher pelvic incidence–lumbar lordosis mismatch, lower thoracic kyphosis, and a higher thoracic kyphosis apex immediately postoperatively significantly predicted earlier rather than later conversion (all p < 0.05). Baseline lumbar lordosis, pelvic tilt, and sacral slope were not significant predictors.

CONCLUSIONS

Patients with ASD with normative cervical alignment who converted to CD after thoracolumbar surgery had varying radiographic findings based on timing of conversion. Although the highest number of patients converted within 6 weeks postoperatively, patients who converted in the late or long-term follow-up intervals had higher rates of concurrent PJK and greater radiographic progression.

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Samantha R. Horn, Peter G. Passias, Cheongeun Oh, Virginie Lafage, Renaud Lafage, Justin S. Smith, Breton Line, Neel Anand, Frank A. Segreto, Cole A. Bortz, Justin K. Scheer, Robert K. Eastlack, Vedat Deviren, Praveen V. Mummaneni, Alan H. Daniels, Paul Park, Pierce D. Nunley, Han Jo Kim, Eric O. Klineberg, Douglas C. Burton, Robert A. Hart, Frank J. Schwab, Shay Bess, Christopher I. Shaffrey, Christopher P. Ames, and the International Spine Study Group

OBJECTIVE

Cervical deformity (CD) correction is clinically challenging. There is a high risk of developing complications with these highly complex procedures. The aim of this study was to use baseline demographic, clinical, and surgical factors to predict a poor outcome following CD surgery.

METHODS

The authors performed a retrospective review of a multicenter prospective CD database. CD was defined as at least one of the following: cervical kyphosis (C2–7 Cobb angle > 10°), cervical scoliosis (coronal Cobb angle > 10°), C2–7 sagittal vertical axis (cSVA) > 4 cm, or chin-brow vertical angle (CBVA) > 25°. Patients were categorized based on having an overall poor outcome or not. Health-related quality of life measures consisted of Neck Disability Index (NDI), EQ-5D, and modified Japanese Orthopaedic Association (mJOA) scale scores. A poor outcome was defined as having all 3 of the following categories met: 1) radiographic poor outcome: deterioration or severe radiographic malalignment 1 year postoperatively for cSVA or T1 slope–cervical lordosis mismatch (TS-CL); 2) clinical poor outcome: failing to meet the minimum clinically important difference (MCID) for NDI or having a severe mJOA Ames modifier; and 3) complications/reoperation poor outcome: major complication, death, or reoperation for a complication other than infection. Univariate logistic regression followed by multivariate regression models was performed, and internal validation was performed by calculating the area under the curve (AUC).

RESULTS

In total, 89 patients with CD were included (mean age 61.9 years, female sex 65.2%, BMI 29.2 kg/m2). By 1 year postoperatively, 18 (20.2%) patients were characterized as having an overall poor outcome. For radiographic poor outcomes, patients’ conditions either deteriorated or remained severe for TS-CL (73% of patients), cSVA (8%), horizontal gaze (34%), and global SVA (28%). For clinical poor outcomes, 80% and 60% of patients did not reach MCID for EQ-5D and NDI, respectively, and 24% of patients had severe symptoms (mJOA score 0–11). For the complications/reoperation poor outcome, 28 patients experienced a major complication, 11 underwent a reoperation, and 1 had a complication-related death. Of patients with a poor clinical outcome, 75% had a poor radiographic outcome; 35% of poor radiographic and 37% of poor clinical outcome patients had a major complication. A poor outcome was predicted by the following combination of factors: osteoporosis, baseline neurological status, use of a transition rod, number of posterior decompressions, baseline pelvic tilt, T2–12 kyphosis, TS-CL, C2–T3 SVA, C2–T1 pelvic angle (C2 slope), global SVA, and number of levels in maximum thoracic kyphosis. The final model predicting a poor outcome (AUC 86%) included the following: osteoporosis (OR 5.9, 95% CI 0.9–39), worse baseline neurological status (OR 11.4, 95% CI 1.8–70.8), baseline pelvic tilt > 20° (OR 0.92, 95% CI 0.85–0.98), > 9 levels in maximum thoracic kyphosis (OR 2.01, 95% CI 1.1–4.1), preoperative C2–T3 SVA > 5.4 cm (OR 1.01, 95% CI 0.9–1.1), and global SVA > 4 cm (OR 3.2, 95% CI 0.09–10.3).

CONCLUSIONS

Of all CD patients in this study, 20.2% had a poor overall outcome, defined by deterioration in radiographic and clinical outcomes, and a major complication. Additionally, 75% of patients with a poor clinical outcome also had a poor radiographic outcome. A poor overall outcome was most strongly predicted by severe baseline neurological deficit, global SVA > 4 cm, and including more of the thoracic maximal kyphosis in the construct.