Cervical Deformity Correction Research Articles

Despite a Multifactorial Etiology, Rates of Distal Junctional Kyphosis After Adult Cervical Deformity Corrective Surgery Can be Dramatically Diminished by Optimizing Age Specific Radiographic Improvement.

Retrospective cohort study of a prospectively collected single-center database. Distal Junctional Kyphosis (DJK) is one of the most common complications in adult cervical deformity (ACD) correction. The utility of radiographic alignment alone in predicting and minimizing DJK occurrence warrants further study. To investigate the impact of post-operative radiographic alignment on development of DJK in ACD patients. ACD patients (≥18yrs) with complete baseline (BL) and two-year (2Y) radiographic data were included. DJF was defined as DJK greater than 15° (Passias et al) or DJK with reop. Multivariable logistic regression (MVA) identified 3-month predictors of DJK. Conditional inference tree (CIT) machine learning analysis determined threshold cutoffs. Radiographic predictors were combined in a model to determine predictive value using area under the curve (AUC) methodology. "Match" refers to ideal age-adjusted alignment. 140 cervical deformity patients met inclusion criteria (61.3yrs, 67% F, BMI: 29kg/m2, CCI: 0.96 ± 1.3). Surgically, 51.3% had osteotomies, 47.1% had a posterior approach, 34.5% combined approach, 18.5% anterior approach, with an average 7.6 ± 3.8 levels fused and EBL of 824mL. Overall, 33 patients (23.6%) developed DJK, and 11 patients (9%) developed DJF. MVA controlling for age, and baseline deformity, followed by CIT found 3M cSVA <3.7cm (OR: .2, 95% CI:.06-.6), and TK T4-T12 <50 (OR:.17, 95% CI:.05-.5, both P < .05) were significant predictors of a lower likelihood of DJK. Receiver operator curve AUC using age, T1S match, TS-CL match, LL-TK match, cSVA <3.7cm, and T4-T12 <50 predicted DJK with an AUC of .91 for DJK by 2Y, and .88 for DJF by 2Y. These findings suggest post-operative radiographic alignment is strongly associated with distal junctional kyphosis. When utilizing age-adjusted realignment in addition to newly developed thresholds, a suggested post-operative cSVA target of 3.7cm and thoracic kyphosis less than 50, it is possible to substantially reduce the occurrence of distal junctional kyphosis and distal junctional failure.

The Conceptualization and Derivation of the Cervical Lordosis Distribution Index.

Yilgor et al developed the lumbar Lordosis Distribution Index to individualize the pelvic mismatch to each patient's pelvic incidence. The cervical lordosis distribution in relation to its apex has not been characterized. Tailor correction of cervical deformity by incorporating the cervical apex into a distribution index(CLDI) to maximize clinical outcomes while lowering rates of junctional failure. Retrospective cohort. CD patients with complete 2Y data were included. Optimal outcome is defined by no DJF, and meeting Virk et al Good Clinical Outcome Criteria:[Meeting 2 of 3: 1)an NDI<20 or meeting MCID, 2)mJOA>=14, 3)an NRS-Neck<=5 or improved by 2 or more points]. C2-T2 lordosis was divided into cranial (C2 to apex) and caudal (apex to T2) arches postoperatively. A cervical lordosis distribution index(CLDI) was developed by dividing the cranial lordotic arch(C2 to apex) by the total segment(C2-T2) and multiplying by 100. Cross-tabulations developed categories for CLDI producing the highest chi-square values for achieving Optimal Outcome at two years and outcomes were assessed by multivariable analysis controlling for significant confounders. 84 CD patients were included. Cervical apex distribution postoperatively was: 1% C3, 42% C4, 30% C5, 27% C6. Mean cervical LDI was 117±138. Mean cranial lordosis was 23.2±12.5°. Using cross-tabulations, a CLDI between 70 and 90 was defined as 'Aligned'. Chi-square test revealed significant differences among CLDI categories for DJK, DJF, Good Clinical Outcome, and Optimal Outcome(all P<0.05). Patients aligned in CLDI were less likely to develop DJK(OR: 0.1, [0.01-0.88]), more like to achieve GCO (OR: 3.9, [1.2-13.2]) and Optimal Outcome (OR: 7.9, [2.1-29.3] at two years. Patients aligned in CLDI developed DJF at a rate of 0%. The cervical lordosis distribution index, classified through the cranial segment, takes each unique cervical apex into account and tailors correction to the patient in order to better achieve good clinical outcomes and minimize catastrophic complications following cervical deformity surgery. III.

Necessity of posterior osteotomies for mild flexible cervical deformity correction.

Correction of mild flexible cervical deformity (CD) via the posterior approach has been described with and without the use of posterior osteotomies (POs), despite a lack of clarity regarding their necessity or risks. The purpose of this study was to determine whether the use of POs when correcting mild flexible CD leads to improved clinical or radiographic outcomes, as well as defining the relative risks in utilizing them. A prospective multicenter registry of operative CD patients was analyzed. Inclusion criteria were cervical kyphosis > 10°, cervical scoliosis > 10°, cervical sagittal vertical axis (cSVA) > 4 cm, or chin-brow vertical angle > 25°. Mild deformity was defined by a cSVA of 3-5 cm and/or kyphosis < 15°. Flexibility was defined by a C2-7 angular change > 5° on preoperative flexion/extension radiographs. Patients who received a posterior column osteotomy (PCO) (Ames grades 1 and 2) were compared with patients who did not undergo a PCO (noPCO) as well as those who underwent a three-column osteotomy (3CO) (Ames grades 3-6). Ninety-five patients (33 PCO, 49 noPCO, 13 3CO) met the inclusion criteria. Both the number of levels fused (9.2 vs 7.7, p = 0.001) and the estimated blood loss (EBL) (1027 vs 486 mL, p = 0.012) were higher in the PCO cohort. Patients in the noPCO group were more likely to have a cervical apex of kyphosis (71.1%, p = 0.046), while those undergoing 3COs were more likely to have a thoracic apex (58.3%, p = 0.005). Preoperative cSVA (PCO vs noPCO: 45.4 vs 37.9 cm, p = 0.084), T1 slope (32.5° vs 29.6°, p = 0.376), C2-7 lordosis (-8.9° vs -9.2°, p = 0.942), and modified Japanese Orthopaedic Association (mJOA) score (13.4 vs 13.5, p = 0.854) were similar; however, both Neck Disability Index (NDI) (55.6 vs 42, p = 0.002) and numeric rating scale (NRS) neck (7.2 vs 5.8, p = 0.028) scores were higher in the PCO group before surgery. When adjusting for the use of an anterior approach, there was no significant difference in 1-year postoperative cSVA (35.7 and 35.6 cm, respectively; p = 0.969), C2-7 lordosis (13.7° and 10.1°, respectively; p = 0.393), and patient-reported outcome measures (NRS, NDI, and mJOA) between the PCO and noPCO groups. Two-year radiographic outcomes were largely similar, except for C2 slope, which was higher in the PCO group (29.1° vs 18°, p = 0.026). The overall complication rates progressively increased with more complex osteotomy use (noPCO 68.8% vs PCO 71.9% vs 3CO 75%) but did not reach significance (p = 0.063). The use of POs for mild flexible adult CD may not be necessary to achieve desirable radiographic correction. They are associated with greater EBL and fusion burden. Further studies are needed to fully delineate the risks of adverse events for various types of osteotomies.

A Meta-Analysis of Surgical Outcomes in 25727 Patients Undergoing Anterior Cervical Discectomy and Fusion or Anterior Cervical Corpectomy and Fusion for Cervical Deformity.

Systematic Review. To evaluate which cervical deformity correction technique between anterior cervical discectomy and fusion (ACDF) and anterior cervical corpectomy and fusion (ACCF) produces better clinical, radiographic, and operative outcomes. We conducted a meta-analysis comparing studies involving ACDF and ACCF. Adult patients with either original or previously treated cervical spine deformities were included. Two independent reviewers categorized extracted data into clinical, radiographic, and operative outcomes, including complications. Clinical assessments included patient-reported outcomes; radiographic evaluations examined C2-C7 Cobb angle, T1 slope, T1-CL, C2-7 SVA, and graft stability. Surgical measures included surgery duration, blood loss, hospital stay, and complications. 26 studies (25727 patients) met inclusion criteria and were extracted. Of these, 14 studies (19077 patients) with low risk of bias were included in meta-analysis. ACDF and ACCF similarly improve clinical outcomes in terms of JOA and NDI, but ACDF is significantly better at achieving lower VAS neck scores. ACDF is also more advantageous for improving cervical lordosis and minimizing the incidence of graft complications. While there is no significant difference between approaches for most surgical complications, ACDF is favorable for reducing operative time, intraoperative blood loss, and length of hospital stay. While both techniques benefit cervical deformity patients, when both techniques are feasible, ACDF may be superior with respect to VAS neck scores, cervical lordosis, graft complications and certain perioperative outcomes. Further studies are recommended to address outcome variability and refine surgical approach selection.

Are insufficient corrections a major factor in distal junctional kyphosis? A simulated analysis of cervical deformity correction using in-construct measurements.

The present study utilized recently developed in-construct measurements in simulations of cervical deformity surgery in order to assess undercorrection and predict distal junctional kyphosis (DJK). A retrospective review of a database of operative cervical deformity patients was analyzed for severe DJK and mild DJK. C2-lower instrumented vertebra (LIV) sagittal angle (SA) was measured postoperatively, and the correction was simulated in the preoperative radiograph in order to match the C2-LIV by using the planning software. Linear regression analysis that used C2 pelvic angle (CPA) and pelvic tilt (PT) determined the simulated PT that matched the virtual CPA. Linear regression analysis was used to determine the C2-T1 SA, C2-T4 SA, and C2-T10 SA that corresponded to DJK of 20° and cervical sagittal vertical axis (cSVA) of 40 mm. Sixty-nine cervical deformity patients were included. Severe and mild DJK occurred in 11 (16%) and 22 (32%) patients, respectively; 3 (4%) required DJK revision. Simulated corrections demonstrated that severe and mild DJK patients had worse alignment compared to non-DJK patients in terms of cSVA (42.5 mm vs 33.0 mm vs 23.4 mm, p < 0.001) and C2-LIV SVA (68.9 mm vs 57.3 mm vs 36.8 mm, p < 0.001). Linear regression revealed the relationships between in-construct measures (C2-T1 SA, C2-T4 SA, and C2-T10 SA), cSVA, and change in DJK (all R > 0.57, p < 0.001). A cSVA of 40 mm corresponded to C2-T4 SA of 10.4° and C2-T10 SA of 28.0°. A DJK angle change of 10° corresponded to C2-T4 SA of 5.8° and C2-T10 SA of 20.1°. Simulated cervical deformity corrections demonstrated that severe DJK patients have insufficient corrections compared to patients without DJK. In-construct measures assess sagittal alignment within the fusion separate from DJK and subjacent compensation. They can be useful as intraoperative tools to gauge the adequacy of cervical deformity correction.

Systematic Review and Meta-Analysis of the Effect of Osteoporosis on Fusion Rates and Complications Following Surgery for Degenerative Cervical Spine Pathology.

As the elderly population grows, the increasing prevalence of osteoporosis presents a unique challenge for surgeons. Decreased bone strength and quality are associated with hardware failure and impaired bone healing, which may increase the rate of revision surgery and the development of complications. The purpose of this review is to determine the impact of osteoporosis on postoperative outcomes for patients with cervical degenerative disease or deformity. A systematic review using Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and Medical Subject Headings terms involving spine surgery for cervical degenerative disease and osteoporosis were performed. This review focused on radiographic outcomes, as well as surgical and medical complications. There were 16 studies included in the degenerative group and 9 in the deformity group. Across degenerative studies, lower bone mineral density was associated with increased rates of cage subsidence in osteoporotic patients undergoing operative treatment for cervical degenerative disease. Most studies reported varied results on the relationship between osteoporosis and other outcomes such as revision and readmission rates, costs, and perioperative complications. Our meta-analysis suggests that osteoporotic patients carry a greater risk of reduced fusion rates at 6 months and 1 year postoperatively. With respect to cervical deformity correction, although individual complication rates were unchanged with osteoporosis, the collective risk of incurring any complication may be increased in patients with poor bone stock. Overall, the literature suggests that outcomes for osteoporotic patients after cervical spine surgery are multifactorial. Osteoporosis seems to be a significant risk factor for developing cage subsidence and pseudarthrosis postoperatively, whereas reports on medical and hospital-related metrics were inconclusive. Our findings highlight the challenges of caring for osteoporotic patients and underline the need for adequately powered studies to understand how osteoporosis changes the risk index of patients undergoing cervical spine surgery. In patients undergoing cervical spine surgery for degenerative disease, osteoporosis is a significant risk factor for long-term postoperative complications-notably cage subsidence and pseudarthrosis. Given the elective nature of these procedures, interdisciplinary collaboration between providers should be routinely implemented to enable medical optimization of patients prior to cervical spine surgery.

Gout-Induced Cervical Deformity and Progressive Myelopathy Mimicking Infection Requiring Cervical Reconstruction

IntroductionThis study describes a rare case where gout, a condition primarily associated with joint inflammation, initially manifested as a progressive cervical kyphotic deformity, mimicking infection and causing myelopathy. The patient, a previously healthy 56-year-old female, presented with severe jaw pain and a temporomandibular joint (TMJ) abscess, alongside two months of worsening balance and arm/hand tingling. Extensive clinical and radiographic assessments revealed a severe cervical kyphotic deformity with bony erosion at multiple vertebral levels, raising suspicion of an infectious cause of compressive myelopathy. MethodsThe patient underwent an urgent staged surgical intervention involving multilevel cervical decompression and fusion, coupled with cervical deformity correction. Post-surgery, she received antibiotics for seven days, during which pathological analysis unveiled collections of macrophages reacting to urate crystal deposition in a pattern consistent with gouty tophus. This unexpected diagnosis marked a novel case of undiagnosed gout-induced severe cervical deformity presenting with myelopathic symptoms and successfully managed through cervical spine deformity correction. ConclusionThis report underscores the significance of considering gout as a potential cause when encountering unusual spinal pathologies, especially in cases where gout-related symptoms are atypical. The presented 540-degree surgical approach effectively addressed both the cervical deformity and gout-induced myelopathic symptoms. To the best of our knowledge, this study represents the first documented instance of a patient with undiagnosed gout-induced severe cervical deformity successfully treated through cervical spine deformity correction, emphasizing the importance of vigilance and innovative management approaches in such rare clinical scenarios. As of the two-year follow-up, the patient exhibited significant symptom improvement and overall well-being.

428 Accomplishing Realignment Goals Withstands the Test of Time: The Outcomes of a Prospective Consecutively Enrolled Single-Center Adult Cervical Deformity Series With Minimum 5-Year Follow-Up

INTRODUCTION: Adult cervical deformity(CD) realignment has shown promising short-term and two-year clinical results, but longer-term outcomes of CD surgery remain unclear. METHODS: Operative CD patients&gt;18 years eligible for 5-year (5Y) follow-up were included. Optimal thresholds for C2 Slope and T1 Slope by Passfall et al were assessed. Student’s t-test, paired t-test, binary and multivariable logistic regression analyses were used to evaluate the clinical, radiographic, and complications outcomes of the five-year eligible cohort. RESULTS: 58 patients were enrolled from 2012 to 2017(54.5±10.3 years,57% female, BMI: 30.0 ± 7.3 kg/m2, 16% osteoporosis), and underwent surgical correction (levels fused: 5.2 ± 2.6, EBL: 772 ± 672 mL, operative time: 372 ± 139 min, LOS: 5.9 ± 8.1 days). By surgical approach, 13.8% anterior-only, 51.7% posterior-only, 34.5% combined. 53% had previous cervical surgery, 41% a fusion. The most common UIV was C3, LIV was T1. By three months (3M), patients improved in cervical lordosis, C2-C7 SVA (cSVA), and T1 Slope(all p &lt;.02), but not C2 Slope or TS-CL (both p&gt;.5). The cohort significantly improved from baseline (BL) to 2Y in NDI, NRS-Neck, and EQ-5D(all P&lt;.02). From 2Y to last follow-up, patients did not improve in mJOA or NDI, but did in EQ-5D (0.441 to 0.509) and NRS-Neck (5.9 to 5.0, both p&lt;.05). There were 14(24.1%) cases of DJK, 6 were distal junctional failure (10.3%), and 17(29.3%) underwent reoperation. Patients corrected below the T1 Slope threshold of 26.5° and maintained at last follow-up experienced DJK less often(OR: 0.1,[0.02-0.74]). Patients corrected below the C2 Slope threshold of 10° and maintained at last follow-up experienced no DJK, DJF or reoperations. CONCLUSIONS: Although complications including distal junctional failure and reoperation remain prevalent, correction of cervical deformity and achievement of realignment targets results in notable clinical and radiographic improvement with most patients achieving favorable outcomes by two years, with further improvement seen until last follow-up.

A Hierarchical Approach to Realignment Strategies in Adult Cervical Deformity Surgery.

Retrospective cohort study. Construct an individualized cervical realignment strategy based on patient parameters at the presentation that results in superior 2-year health-related quality of life metrics and decreased rates of junctional failure and reoperation following adult cervical deformity surgery. Research has previously focused on adult cervical deformity realignment thresholds for maximizing clinical outcomes while minimizing complications. However, realignment strategies may differ based on patient presentation and clinical characteristics. We included adult cervical deformity patients with 2-year data. The optimal outcome was defined as meeting good clinical outcomes without distal junctional failure or reoperation. Radiographic parameters assessed included C2 Slope, C2-C7, McGregor's slope, TS-CL, cSVA, T1 slope, and preoperative lowest-instrumented vertebra (LIV) inclination angle. Conditional inference trees were used to establish thresholds for each parameter based on achieving the optimal outcome. Analysis of Covariance and multivariable logistic regression analysis, controlling for age, comorbidities, baseline deformity and disability, and surgical factors, assessed outcome rates for the hierarchical approach within each deformity group. One hundred twenty-seven patients were included. After correction, there was a significant difference in meeting the optimal outcome when correcting the C2 slope below 10 degrees (85% vs. 34%, P <0.001), along with lower rates of distal junctional failure (DJF) (7% vs. 42%, P <0.001). Next, after isolating patients below the C2 slope threshold, the selection of LIV with an inclination between 0 and 40 degrees demonstrated lower rates of distal junctional kyphosis and higher odds of meeting optimal outcome(OR: 4.2, P =0.011). The best third step was the correction of cSVA below 35mm. This hierarchical approach (11% of the cohort) led to significantly lower rates of DJF (0% vs. 15%, P <0.007), reoperation (8% vs. 28%, P <0.001), and higher rates of meeting optimal outcome (93% vs. 36%, P <0.001) when controlling for age, comorbidities, and baseline deformity and disability. Our results indicate that the correction of C2 slope should be prioritized during cervical deformity surgery, with the selection of a stable LIV and correction of cervical SVA below the idealized threshold. Among the numerous radiographic parameters considered during preoperative planning for cervical deformity correction, our determinations help surgeons prioritize those realignment strategies that maximize the health-related quality of life outcomes and minimize complications. Level-III.

3D Printing in Surgical Planning and Intra-Operative Assistance: A Case Report on Cervical Deformity Correction Surgery

Three-dimensional (3D)-printed anatomical models of the bones play a key role in complex surgical procedures. These subject-specific physical models are valuable in pre-operative planning and may also offer assistance during surgery by improving the visibility of inaccessible anatomical structures, particularly in spine surgery. Starting from medical imaging, virtual 3D bone models are reconstructed, and these can also be used for quantifying original, planned, and achieved bone-to-bone alignments. The purpose of this study is to report on an original exploitation of these techniques on a patient with a severe cervical deformity to undergo corrective and stabilizing surgery. A virtual anatomical model of the cervical spine before surgery was obtained from computer tomography to assess the original deformity and for surgical planning. The corresponding 3D model was printed in acrylonitrile-butadiene-styrene and used to simulate the surgery by performing bone cuts, implanting the screws, and placing and shaping the fixation elements. During surgery, this physical 3D-printed model was used as a reference for each surgical action. The comparisons between pre- and post-operative virtual models confirmed that the planned correction was achieved. Virtual and 3D-printed anatomical models of the cervical spine offer advantages in the planning and execution of personalized complex surgeries, in addition to improving surgical safety.

Proximal and distal reciprocal changes following cervical deformity malalignment correction.

Hyperextension of C0-2 is a debilitating compensatory mechanism used to maintain horizontal gaze, analogous to high pelvic tilt in the lumbopelvic complex to maintain an upright posture. This study aims to investigate the impact of cervical deformity (CD) correction on this hyperextension. The authors hypothesize that correction of cervical sagittal malalignment allows for relaxation of C0-2 hyperextension and improved clinical outcomes. A retrospective review was conducted of a multicenter database of patients with CD undergoing spinal realignment and fusion caudal to C2 and cephalad to the pelvis. Range of motion (ROM) and reserve of extension (ROE) were calculated across C2-7 and C0-2. The association between C2-7 correction and change in C0-2 ROE was investigated while controlling for horizontal gaze, followed by stratification into ΔC2-7 percentiles. Sixty-five patients were included (mean age 61.8 ± 9.6 years, 68% female). At baseline, patients had cervical kyphosis (C2-7, -11.7° ± 18.2°; T1 slope-cervical lordosis mismatch, 38.6° ± 18.6°), negative global alignment (sagittal vertical axis [SVA] -12.8 ± 71.2 mm), and hyperlordosis at C0-2 (mean 33.2° ± 11.8°). The mean ROM was 25.7° ± 17.7° and 21.3° ± 9.9° at C2-7 and C0-2, respectively, with an ROE of approximately 9° for each segment. Limited C0-2 ROM and ROE correlated with the Neck Disability Index (r = -0.371 and -0.394, p < 0.01). The mean number of levels fused was 7.0 ± 3.1 (24.6% anterior, 43.1% posterior), with 87.7% undergoing at least an osteotomy. At 1 year, mean C2-7 increased to 5.5° ± 13.4°, SVA became neutral (11.5 ± 54.8 mm), C0-2 hyperlordosis decreased to 27.8° ± 11.7°, and thoracic kyphosis (TK) increased to -49.4° ± 18.1° (all p < 0.001). Concurrently, mean C0-2 ROM increased to 27.6° ± 8.1° and C2-7 ROM decreased significantly to 9.0° ± 12.3° without a change in ROE. Controlling for horizontal gaze, change in C2-7 lordosis significantly correlated with increased TK (r = -0.617, p < 0.001), decreased C0-2 (r = -0.747, p < 0.001), and increased C0-2 ROE (r = 0.550, p = 0.002). CD correction can significantly impact cephalad and caudal compensation in the upper cervical and thoracic spine. Restoration of cervical alignment resulted in increased C0-2 ROE and TK and was also associated with improved clinical outcome.

Predicting the Magnitude of Distal Junctional Kyphosis Following Cervical Deformity Correction.

Retrospective review of a cervical deformity database. This study aimed to develop a model that can predict the postoperative distal junctional kyphosis angle (DJKA) using preoperative and postoperative radiographic measurements. Distal junctional kyphosis (DJK) is a complication following cervical deformity correction that can reduce of patient quality of life and functional status. Although researchers have identified the risk factors for DJK, no model has been proposed to predict the magnitude of DJK. The DJKA was defined as the Cobb angle from the lower instrumented vertebra (LIV) to LIV-2 with traditional DJK having a DJKA change >10°. Models were trained using 66.6% of the randomly selected patients and validated in the remaining 33.3%. Preoperative and postoperative radiographic parameters associated with DJK were identified and ranked using a conditional variable importance table. Linear regression models were developed using the factors most strongly associated with postoperative DJKA. A total of 131 patients were included with a mean follow-up duration of 14±8 months. The mean postoperative DJKA was 14.6±14° and occurred in 35% of the patients. No significant differences between the training and validation cohort were observed. The variables most associated with postoperative DJK were: preoperative DJKA (DJKApre), postoperative C2-LIV, and change in cervical lordosis (∆CL). The model identified the following equation as predictive of DJKA: DJKA=9.365+(0.123×∆CL)-(0.315×∆C2-LIV)-(0.054×DJKApre). The predicted and actual postoperative DJKA values were highly correlated ( R =0.871, R2 =0.759, P <0.001). The variables that most increased the DJKA were the preoperative DJKA, postoperative alignment within the construct, and change in cervical lordosis. Future studies can build upon the model developed to be applied in a clinical setting when planning for cervical deformity correction.

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?

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. 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. 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. 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.

14. Despite a multifactorial etiology, rates of distal junctional kyphosis after adult cervical deformity corrective surgery can be dramatically diminished by optimizing age-specific radiographic improvement

<h3>BACKGROUND CONTEXT</h3> Distal junctional kyphosis (DJK) is one of the most common complications in adult cervical deformity (ACD) correction. The utility of radiographic alignment alone in predicting and minimizing DJK occurrence warrants further study. <h3>PURPOSE</h3> To investigate the impact of postoperative radiographic alignment on development of DJK in ACD patients. <h3>STUDY DESIGN/SETTING</h3> Retrospective cohort study of a multicenter prospective ACD database. <h3>PATIENT SAMPLE</h3> A total of 450 ACD patients. <h3>OUTCOME MEASURES</h3> DJK after cervical deformity surgery. <h3>METHODS</h3> ACD patients (18 yrs) with complete baseline (BL) and two-year (2Y) radiographic data were included. DJF was defined as DJK greater than 15 or DJK with reop. Multivariable logistic regression (MVA) identified 3-month predictors of DJK. Conditional inference tree (CIT) machine learning analysis determined threshold cutoffs. Radiographic predictors were combined in a model to determine predictive value using area under the curve (AUC) methodology. "Match" refers to ideal age-adjusted alignment. <h3>RESULTS</h3> A total of 140 cervical deformity patients met inclusion criteria (61.3yrs, 67%F, BMI 29kg/m², CCI 0.96±1.3). Surgically, 51.3% had osteotomies, 47.1% had a posterior approach, 34.5% combined approach, 18.5% anterior approach, with an average 7.6± 3.8 levels fused and EBL of 824 mL. Overall, 33 patients (23.6%) developed DJK, and 11 patients (9%) developed DJF. MVA controlling for age, and baseline deformity, followed by CIT found 3M cSVA <3.7 cm (OR .2, 95% CI .06-.6), and TK T4-T12 <50 (OR .17, 95% CI .05-.5, both p <.05) were significant predictors of a lower likelihood of DJK. Receiver operator curve AUC using age, T1S match, TS-CL match, LL-TK match, cSVA <3.7 cm, and T4-T12 <50 predicted DJK with an AUC of .91 for DJK by 2 years, and .88 for DJF by 2 years. <h3>CONCLUSIONS</h3> These findings suggest postoperative radiographic alignment is strongly associated with distal junctional kyphosis. When utilizing age-adjusted realignment in addition to newly developed thresholds, a suggested postoperative cSVA target of 3.7 cm and thoracic kyphosis less than 50, it is possible to substantially reduce the occurrence of distal junctional kyphosis and distal junctional failure. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

137. The impact of delayed surgical intervention for cervical deformity on patient recovery and cost effectiveness

<h3>BACKGROUND CONTEXT</h3> Surgical correction of cervical deformity is a proven treatment option that provides functional restoration and pain relief. It is unclear whether patient outcomes and costs of the procedure are influenced by the time between initial symptom onset and definitive surgical intervention. This study sought to determine how long nonoperative treatment should be exhausted prior to offering surgery for cervical deformity. <h3>PURPOSE</h3> To identify whether delayed procedures influence patients' ability to recover and cervical deforminty corrective surgery cost effectiveness. <h3>STUDY DESIGN/SETTING</h3> Retrospective cohort. <h3>PATIENT SAMPLE</h3> This study included 290 cervical deformity patients. <h3>OUTCOME MEASURES</h3> Delayed surgical intervention, recovery kinetics, cost effectiveness. <h3>METHODS</h3> Cervical deformity patients with baseline (BL) and two-year (2Y) follow-up data were included. Patients were stratified by time to surgery following the onset of their neck pain: >5 years=Delayed; <5 years=not Delayed. Normalized HRQL scores at BL and follow-up intervals (3M, 6M, 1Y, 2Y) were generated. Normalized HRQLs were plotted and area under the curve was calculated, generating one number describing overall recovery (Integrated Health State [IHS]). Cost was calculated using the PearlDiver database, which represents national average Medicare cost. Cost per Quality-Adjusted Life Year (QALY) at 2Y was calculated. Multivariable regression analysis assessed the impact of Delayed surgery on patient outcomes and cost. <h3>RESULTS</h3> A total of 123 patients were included (54 Delayed, 69 not Delayed). Demographic and surgical characteristics were similar between groups (p > 0.05). Normalized HRQLs showed that Delayed patients exhibit worse NDI and NRS Neck at 2Y follow-up, both p 0.05. Utility gained at 2Y follow-up was 0.172 for Delayed and 0.2847 for not Delayed. This translated to QALY gained at 2Y of 0.334 for Delayed and 0.553 for not Delayed, p 0.05. Multivariable analysis found Delayed patients were less likely to gain utility (OR 0.125 [CI 0.019-0.840]) and QALYs (OR 0.343 [CI 0.129-0.914]) at 2Y postoperatively, both p< 0.05. <h3>CONCLUSIONS</h3> Patients who had a 5-year or greater delay to surgery from the onset of neck pain had more significant postoperative neck disability. Cost by procedure and cost-effectiveness when stratified by time to surgery following enrollment were comparable. While both patient cohorts had postop improvement, patients without delay had greater utility gained and quality adjusted life years at 2-year follow-up. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

Trends in Outcomes of a Prospective Consecutively Enrolled Single-Center Adult Cervical Deformity Series.

Retrospective cohort. The aim was to describe the two-year outcomes for patients undergoing surgical correction of cervical deformity (CD). Adult CD has been shown to compromise health-related quality of life. While advances in spinal realignment have shown promising short-term clinical results in this parameter, the long-term outcomes of CD corrective surgery remain unclear. Operative CD patients >18 years with two-year (2Y) health-related quality of life/radiographic data were included. Improvement in radiographic, neurologic, and health-related quality of life outcomes were reported. Patients with a prior cervical fusion and patients with the greatest and smallest change based on Neck Disability Index (NDI), numeric rating scale (NRS) neck, modified Japanese Orthopaedic Association (mJOA) were compared using multivariable analysis controlling for age, and frailty, and invasiveness. One hundred and fifty-eight patients were included in this study. By 2Y, 96.3% of patients improved in Ames cervical sagittal vertical axis modifier, 34.2% in T1 slope minus cervical lordosis (TS-CL), 42.0% in horizontal gaze modifier, and 40.9% in SVA modifier. In addition, 65.5% of patients improved in Passias CL modifier, 53.3% in TS-CL modifier, 100% in C2-T3 modifier, 88.9% in C2S modifier, and 81.0% in MGS modifier severity by 2Y. The cohort significantly improved from baseline to 2Y in NDI, NRS Neck, and mJOA, all P <0.05. 59.3% of patients met minimal clinically important difference for NDI, 62.3% for NRS Neck, and 37.3% for mJOA. Ninety-seven patients presented with at least one neurologic deficit at baseline and 63.9% no longer reported that deficit at follow-up. There were 45 (34.6%) cases of distal junctional kyphosis (DJK) (∆DJKA>10° between lower instrumented vertebra and lower instrumented vertebra-2), of which 17 were distal junctional failure (distal junctional failure-DJK requiring reoperation). Patients with the greatest beneficial change were less likely to have had a complication in the two-year follow-up period. Correction of CD results in notable clinical and radiographic improvement with most patients achieving favorable outcomes after two years. However, complications including DJK or failure remain prevalent.

Cervical Deformity Correction Fails to Achieve Age-Adjusted Spinopelvic Alignment Targets.

To assess whether surgical cervical deformity (CD) patients meet spinopelvic age-adjusted alignment targets, reciprocal, and lower limb compensation changes. Retrospective review. CD was defined as C2-C7 lordosis >10°, cervical sagittal vertical angle (cSVA) >4 cm, or T1 slope minus cervical lordosis (TS-CL) >20°. Inclusion criteria were age >18 years and undergoing surgical correction with complete baseline and postoperative imaging. Published formulas were used to create age-adjusted alignment target for pelvic tilt (PT), pelvic incidence and lumbar lordosis (PI-LL), sagittal vertical angle (SVA), and lumbar lordosis and thoracic kyphosis (LL-TK). Actual alignment was compared with age-adjusted ideal values. Patients who matched ±10-year thresholds for age-adjusted targets were compared with unmatched cases (under- or overcorrected). A total of 120 CD patients were included (mean age, 55.1 years; 48.4% women; body mass index, 28.8 kg/m2). For PT, only 24.4% of patients matched age-adjusted alignment, 51.1% overcorrected for PT, and 24.4% undercorrected. For PI-LL, only 27.6% of CD patients matched age-adjusted targets, with 49.4% overcorrected and 23% undercorrected postoperatively. Forty percent of patients matched age-adjusted target for SVA, 41.3% overcorrected, and 18.8% undercorrected. CD patients who had worsened in TS-CL or cSVA postoperatively displayed increased TK (-41.1° to -45.3°, P = 1.06). With lower extremity compensation, CD patients decreased in ankle flexion angle postoperatively (6.1°-5.5°, P = 0.036) and trended toward smaller sacrofemoral angle (199.6-195.6 mm, P = 0.286) and knee flexion (2.6° to -1.1°, P = 0.269). In response to worsening CD postoperatively, patients increased in TK and recruited less lower limb compensation. Almost 75% of CD patients did not meet previously established spinopelvic alignment goals, of whom a subset of patients were actually made worse off in these parameters following surgery. This finding raises the question of whether we should be looking at the entire spine when treating CD.

Optimizing Cervicothoracic Junction Biomechanics after C7 Pedicle Subtraction Osteotomy: A Cadaveric Study of Stability and Rod Strain

To compare biomechanical stability and rod strain among uniform rod (UR), tapered rod (TR), and UR+accessory rod (AR) constructs in a human cadaveric C7 pedicle subtraction osteotomy (PSO) model of cervical deformity correction. Fourteen human cadaveric C2-T4 specimens were divided into 2 statistically equivalent groups. Specimens were instrumented from C2 to T3, and a 25° PSO was performed at C7. Group 1 was instrumented with 3.5-mm to 5.5-mm titanium TRs, and group 2 received 4.0-mm titanium URs. The UR group was also tested with lateral 4.0-mm titanium ARs (UR+AR) at C5-T2. All conditions were tested with 2.0 Nm pure moment and 70 N compressive load. Intervertebral range of motion (ROM) and posterior rod strain (pRS) were measured at C2-C3, T2-T3, and the PSO level. Statistical comparisons used 1-way analysis of variance. ROM was significantly reduced in the TR versus UR construct for right axial rotation (P= 0.04) at the PSO level; ROM with TR was significantly greater than with UR and UR+AR in compression (P ≤ 0.02). At the PSO level, pRS was significantly greater in TR than in UR+AR in flexion, extension, and right axial rotation (P ≤ 0.02). At T2/3, pRS was higher in UR than TR in left axial rotation (P= 0.003). C7 PSO is highly destabilizing. Maximal rod strain was concentrated across the PSO and the cranial fixation site. TR provided higher stability than did UR in 1 direction of movement; however, UR+AR provided the greatest reduction of pRS.

Baseline Frailty Status Influences Recovery Patterns and Outcomes Following Alignment Correction of Cervical Deformity

Pierce, Katherine E BS; Passias, Peter G MD; Daniels, Alan H MD; Lafage, Renaud MS; Ahmad, Waleed MS; Naessig, Sara BS; Lafage, Virginie PhD; Protopsaltis, Themistocles MD; Eastlack, Robert MD; Hart, Robert MD; Burton, Douglas MD; Bess, Shay MD; Schwab, Frank MD; Shaffrey, Christopher MD; Smith, Justin S MD, PhD; Ames, Christopher MD, on behalf of the International Spine Study Group (ISSG)

Front-Back Cervical Deformity Correction by Anterior Cervical Discectomy and Fusion With Posterior Instrumentation: 2-Dimensional Operative Video.

Front-back procedures for cervical deformity permit the correction of cervical kyphosis in the setting of unfused facets. Here, we highlight the operative treatment of a 65-yr-old female entailing a 4-level anterior cervical discectomy and fusion (ACDF) at C3-C4, C4-C5, C5-C6, and C6-C7 with hyperlordotic interbody implants, supplemented by a posterior C2-T2 instrumented fusion. The patient initially presented with symptoms of treatment-refractory neck pain while neurologically intact on examination. Her imaging demonstrated significant cervical kyphosis measuring 46° as the Cobb angle between C2 and C7 without neural compression. The patient consented to the procedure and publication of their image. After 2 d of traction, the operation proceeded with the patient initially in a supine position with dissection medial to the sternocleidomastoid muscle down to the vertebral bodies. Discectomies were performed at each level followed by installation of the interbody implants. After closure of this access wound, the patient was turned to a prone position for the posterior element of the operation. The posterior bony elements were exposed and a C2-T2 instrumented fusion performed. Postoperative imaging demonstrated improvement of her sagittal cervical curvature and the patient described improvement in her neck pain.