Is Modified K-line a Powerful Tool of Surgical Decision Making for Patients With Cervical Spondylotic Myelopathy? Study Design: Prospective observational single-center study. Objective: To evaluate anterior decompression and fusion (ADF) or posterior surgery (PS) for patients with cervical spondylotic myelopathy (CSM) using the modified K-line (mK-line) and to compare clinical and radiologic outcomes between these 2 techniques. Summary of Background Data: The authors have previously reported that insufficient posterior decompression is often seen after laminoplasty for CSM in patients with preoperative anterior clearance of the spinal cord <4 mm on the basis of the mK-line. However, to our knowledge, no study has investigated the role, if any, of the mK-line in surgical decision making for patients with CSM. Methods: A total of 87 patients were enrolled who underwent surgery for treatment of CSM between 2011 and 2015 at our hospital and who could be followed up for at least 2 years. ADF was selected as a more favorable procedure than PS in patients with anterior spinal clearance of <4 mm on preoperative midsagittal magnetic resonance imaging. On the basis of the Japanese Orthopedic Association (JOA) scoring system for cervical myelopathy, the rate of recovery of the JOA scores at 2 years after surgery was investigated as a clinical outcome to compare these 2 groups. Results: Mean age was 65.1 (±12.9) years in the ADF group (n=26) and 70.5 (±8.6) years in the PS group (n=61). In the PS group, 10 patients underwent posterior decompression with fusion. Mean preoperative and postoperative JOA scores were 10.5 and 14.1 points in the ADF group and 9.8 and 13.1 points in the PS group, respectively, showing no significant difference in recovery rate of JOA score between the ADF (58.9%) and PS (47.1%) groups. However, patients with a minimum interval between the mK-line and the anterior compression factor on the midsagittal image (minimum interval of the spinal cord) <4 mm tended to have unsatisfactory outcomes (recovery rate 29.6%) compared with patients with minimum interval of the spinal cord >4 mm (53.6%, P=0.07) in the PS group. Conclusion: Preoperative intervention using the mK-line is useful to predict residual cord compression and might homogenize postoperative clinical outcomes in both anterior surgery and PS.

Can the American College of Surgeons Risk Calculator Predict 30-Day Complications After Cervical Spine Surgery? Study Design: This was a retrospective cohort study. Objective: The objective of this study was to assess the American College of Surgeons (ACS) Risk Calculator’s ability to accurately predict complications after cervical spine surgery. Summary of Background Data: Surgical risk calculators exist in many fields and may assist in the identification of patients at increased risk for complications and readmissions. Risk calculators may allow for improved outcomes, an enhanced informed consent process, and management of modifiable risk factors. The American College of Surgeons National Surgery Quality Improvement Program (ACS NSQIP) Risk Calculator was developed from a cohort of over 1.4 million patients, using 2805 unique Current Procedural Terminology (CPT) codes. The risk calculator uses 21 patient predictors (eg, age, American Society of Anesthesiologists class, body mass index, hypertension) and the planned procedure (CPT code) to predict the chance that patients will have any of 12 different outcomes (eg, death, any complication, serious complication, reoperation) within 30 days following surgery. The purpose of this study is to determine if the ACS NISQIP risk calculator can predict 30-day complications after cervical fusion. Methods: A retrospective chart review was performed on patients that underwent primary cervical fusions between January 2009 and 2015 at a single institution, utilizing cervical fusion CPT codes. Patients without 30 days of postoperative follow-up were excluded. Descriptive statistics were calculated for the overall sample, anterior versus posterior fusion, and single versus multilevel fusion. Logistic regression models were fit with actual complication occurrence as the dependent variable in each model and ACS estimated risk as the independent variable. The c-statistic was used as the measure of concordance for each model. Receiver operating characteristic curves were plotted to visually depict the predictive ability of the estimated risks. Acceptable concordance was set at c>0.80. All analyses were conducted using SAS, v9.4. Results: A total of 404 patients met the inclusion criteria for this study. Age, body mass index, sex, and a number of levels of fusion were gathered as input data the ACS NSQIP Risk Calculator. Results of Risk Calculator were compared with observed complication rates. Descriptive statistics of the Risk Calculator risk estimates showed a significant prediction of “any complication” and “discharge to skilled nursing facility” among the cohort. Because there were no deaths or urinary tract infections, no models were fit for these outcomes. Conclusions: The ACS Risk Calculator accurately predicted complications in the categories of “any complication” (P<0.0001) and “discharge to the skilled nursing facility” (P<0.001) for our cohort. We conclude that the ACS Risk Calculator was unable to accurately predict specific complications on a more granular basis for the patients of this study. Although the ACS risk calculator may be useful in the field of general surgery and in the development of new institutional strategies for risk mitigation, our findings demonstrate that it does not necessarily provide accurate information for patients undergoing cervical spinal surgery.

Progression of Cervical Ossification of Posterior Longitudinal Ligament After Laminoplasty or Laminectomy With Posterior Fixation Study Design: Retrospective case analysis. Objective: This study was conducted to investigate the course of ossification of the posterior longitudinal ligament (OPLL) progression after laminoplasty (LP) or laminectomy with posterior fixation (PF). Summary of Background Data: LP is now recognized as a standard technique for the treatment of cervical multisegment OPLL; however, PF is beneficial for patients with severe stenosis. In recent years, there has been increasing interest in mechanical stress in OPLL, which is assumed to significantly impact progression. Methods: The progression of OPLL was assessed using midline sagittal computed tomography images of the cervical spine at various follow-up points. Radiographic parameters including the C2–C7 Cobb angle, C2–C7 range of motion (ROM), and adjacent cranial and caudal segmental ROMs were measured. Postoperative changes and differences between the LP and PF groups in the radiographic parameters were calculated to assess biomechanical stress. Logistic regression analysis was used to analyze the risk factors affecting the progression rate. Results: The authors included 14 PF and 36 LP patients, with a mean follow-up period of 28.9±20.8 and 37.6±16.8 months, respectively (P=0.069). After surgical treatment, both groups showed loss of cervical lordosis (9.2±6.9 vs. 5.3±8.2 degrees, P=0.220) and C2–C7 ROM (14.6± 13.5 vs. 13.1±12.2 degrees, P=0.861). The decrease of ROM in the cranial adjacent segment was larger in the LP group than in the PF group (0.7±4.1 vs. 1.4±5.5 degrees, P=0.453). The ROM in the caudal adjacent segment decreased in the LP group but increased in the PF group (−1.4±6.2 vs. 2.6±5.1 degrees, P=0.041). The progression rate was 2.15±1.31 mm2/mo in the PF group and 1.53±1.04 mm2/mo in the LP group (P=0.041). PF showed an odds ratio of 12.917 for a higher progression rate (95% confidence interval, 1.397–119.443; P=0.024). Conclusion: The rate of progression of cervical OPLL was significantly higher after PF than after LP. Level of Evidence: Level III—a retrospective analysis.

The Effect of Surgical Decompression on Functional Balance Testing in Patients With Cervical Spondylotic Myelopathy Study Design: A prospective cohort study. Objective: Quantify the extent of change in dynamic balance and stability in a group of patients with cervical spondylotic myelopathy (CSM) after cervical decompression surgery and to compare them with matched healthy controls. Summary of Background Data: CSM is a naturally progressive degenerative condition that commonly results in loss of fine motor control in the hands and upper extremities and in gait imbalance. Whereas this was previously thought of as an irreversible condition, more recent studies are demonstrating postoperative improvements in balance and stability. Materials and Methods: Thirty subjects with symptomatic CSM and 25 matched asymptomatic controls between the ages of 45 and 75 years underwent functional balance testing using a 3D motion capture system to gather kinematic and spatiotemporal parameters. CSM subjects underwent testing 1 week before surgery and again 3 months postoperatively. Results: Patients with CSM exhibited markedly diminished balance as indicated by increased sway on a Romberg test and requiring significantly more time and a wider stance to complete tandem gait tests. The surgical intervention resulted in improved balance at the 3-month postoperative time point; however, kinematic and spatiotemporal parameters did not completely normalize to the levels observed in asymptomatic controls. Conclusions: Human motion video capture can be used to robustly quantify balance parameters in the setting of CSM. Compared with healthy controls, such patients exhibited increased standing sway and poorer performance on a tandem gait task. The surgical intervention resulted in significant improvement in many of the measures of functional balance, but overall profiles had not completely returned to normal when measured 3 months after surgery. These data reinforce the importance of operative intervention in the treatment of symptomatic CSM with the goal of halting disease progress but the expectation that balance may actually improve postoperatively.

Crossing the Cervicothoracic Junction in Cervical Arthrodesis Results in Lower Rates of Adjacent Segment Disease Without Affecting Operative Risks or Patient-Reported Outcomes Study Design: Retrospective cohort study. Objective: To evaluate the risks and benefits of crossing the cervicothoracic junction (CTJ) in cervical arthrodesis. Summary of Background Data: Whether the CTJ should be crossed in cervical arthrodesis remains up for debate. Keeping C7 as the distal end of the fusion risks adjacent segment disease (ASD) and can result in myelopathy or radiculopathy. Longer fusions are thought to increase operative risk and complexity but result in lower rates of ASD. Materials and Methods: Patients undergoing cervical spine fusion surgery ending at C7 or T1 with ≥1-year follow-up were included. To evaluate operative risk, estimated blood loss (EBL), operative time, and length of hospital stay were collected. To evaluate patient-reported outcomes (PROs), Neck Disability Index (NDI) and SF-12 questionnaires (PCS12 and MCS12) were obtained at follow-up. Revision surgery data were also obtained. Results: A total of 168 patients were included and divided into a C7 end-of-fusion cohort (NC7=59) and a T1 end-of-fusion cohort (NT1=109). Multivariate regression analysis adjusting for age, sex, race, surgical approach, and number of levels fused showed that EBL (P=0.12), operative time (P=0.07), and length of hospital stay (P=0.06) are not significantly different in the C7 and T1 end-of-fusion cohorts. Multivariate regression of PROs showed no significant difference in NDI (P=0.70), PCS12 (P=0.23), or MCS12 (P=0.15) between cohorts. Fisher analysis showed significantly higher revision rates in the C7 end-of-fusion cohort (7/59 for C7 vs. 2/109 for T1; odds ratio, 6.4; 95% confidence interval, 1.2–65.1; P=0.01). Conclusions: Crossing the CTJ in cervical arthrodesis does not increase operative risk as measured by blood loss, operative time, and length of hospital stay. However, it leads to lower revision rates, likely because of the avoidance of ASD, and comparable PROs. Thus, crossing the CTJ may help prevent ASD without negatively affecting operative risk or long-term PROs.

Impact of K-Line (–) in the Neck-Flexion Position on Patient-reported Outcomes After Cervical Laminoplasty For Patients With Ossification of the Posterior Longitudinal Ligament Study Design: This study was a post hoc analysis of prospective data. Objective: The objective of this study was to investigate whether K-line (–) in the neck-flexion position [f-K-line (–)] affects patient-reported outcome measures after cervical laminoplasty for patients with ossification of the posterior longitudinal ligament (OPLL). Summary of Background and Data: The f-K-line was recently proposed as a predictor of poor outcomes after laminoplasty for patients with OPLL. However, its impact on patient-reported outcome measures remains to be elucidated. Patients and Methods: We analyzed prospectively collected data from 68 patients with cervical myelopathy due to OPLL who underwent double-door laminoplasty between 2008 and 2015. Patients were categorized into f-K-line (–) and f-K-line (+) groups on a baseline neck-flexion radiograph. Outcome measures included the Japanese Orthopaedic Association score, EuroQol 5-Dimensional Questionnaire, the Japanese Orthopaedic Association Cervical Myelopathy Evaluation Questionnaire, and 11-point Numerical Rating Scale for pain. The degree of satisfaction with the outcome was assessed at the 2-year follow-up using a 7-point Numerical Rating Scale. Results: Of the 68 patients, 22 (32%) and 46 (68%) were grouped into the f-K-line (–) and f-K-line (+) groups, respectively. The 2 groups showed no significant difference in baseline functions. The f-K-line (–) group showed a significantly lower recovery rate of the Japanese Orthopaedic Association score and a significantly lower gain in EuroQol 5-Dimensional Questionnaire score than compared with the f-K-line (+) group at the 2-year follow-up. Among the 5 domains of the Japanese Orthopaedic Association Cervical Myelopathy Evaluation Questionnaire, cervical function, and upper extremity function were significantly lower in the f-K-line (–) group than in the f-K-line (+) group. Patients in the f-K-line (–) group also reported a significantly higher pain intensity in the upper and lower extremities and a significantly lower degree of satisfaction compared with those in the f-K-line (+) group. Conclusion: The f-K-line (–) was significantly associated with poorer functional recovery, higher pain intensity in the extremities, and lower patient satisfaction after cervical laminoplasty for patients with OPLL.

Does the Duration of Cervical Radicular Symptoms Impact Outcomes After Anterior Cervical Discectomy and Fusion? Study Design: Retrospective cohort study. Objective: To compare clinical outcomes after anterior cervical discectomy and fusion (ACDF) based on preoperative duration of radiculopathy symptoms. Summary of Background Data: There is no clear indication of when outcomes after ACDF become less effective in the setting of acute versus chronic symptoms from cervical nerve root compression. Materials and Methods: A retrospective cohort study of consecutive patients who underwent an ACDF between 2008 and 2015 for radiculopathy was performed. Patients were divided into 3 groups: radicular symptoms lasting for <6 months, symptoms lasting for 6–12 months, and those with symptoms for ≥12 months. Neck Disability Index (NDI) and Visual Analog Scale (VAS) scores for both the neck and arms were obtained at preoperative and final postoperative visits. Radiographs were assessed for adjacent segment degeneration, fusion, and subsidence. Bivariate and multivariate regressions were subsequently used to compare outcomes between groups. Results: A total of 379 patients were included. Patients with symptoms lasting for 6–12 months and those with symptoms lasting for ≥12 months had worse preoperative VAS neck pain compared with patients with symptoms lasting for < 6 months (P=0.000 and P=0.004, respectively). Patients with symptoms lasting for ≥12 months had worse baseline functional status compared with patients with symptoms lasting for <6 months (P=0.009). At final follow-up, there were no significant differences in VAS neck, VAS arm, or NDI between symptom duration groups. However, differences in outcomes were noted when considering the type of preoperative symptom. Patients with pain symptoms of ≥12 months had worse preoperative VAS neck (P=0.001), VAS arm (P=0.008), and NDI (P<0.001) and had significantly worse final VAS arm (P=0.019) and NDI (P=0.016) compared with patients with preoperative pain symptoms lasting for <6 months. The overall reoperation rate was 4.5%. Fusion was achieved in 97.6% of the patients, and subsidence was observed in 5.5%. There were no significant differences in the risk of adjacent segment degeneration, reoperations, fusion rates, or subsidence rates based on preoperative symptom duration. Conclusions: Despite worse preoperative neck pain and functional status in patients with preoperative duration of symptoms >6 months, there were no differences in final clinical outcomes across groups.

Minimal Clinically Important Difference and Substantial Clinical Benefit Using PROMIS CAT in Cervical Spine Surgery Study Design: This was a prospective cohort study. Objective: The objective of this study was to establish minimal clinically important difference (MCID) and substantial clinical benefit (SCB) thresholds for Patient-Reported Outcomes Measurement Information System (PROMIS) in cervical spine pathology. Summary of Background Data: PROMIS enables improved psychometric properties with reduced questionnaire burden through computer adaptive testing. Despite studies showing good correlation with “legacy” outcome measures, literature on the clinical significance of changes in PROMIS scores is scarce. Materials and Methods: Adult patients undergoing cervical spine surgery at a single institution between 2016 and 2018 were prospectively enrolled. Patients completed questionnaires [Short Form-36 (SF-36), Neck Disability Index (NDI), Visual Analogue Scale Arm/Neck, and PROMIS Pain Interference (PI) and Physical Function (PF)] preoperatively and at 6 months postoperatively. MCID was calculated using distribution-based and SCB using anchor-based methods. The SF-36 Health Transition Item was utilized as an anchor with the cutoff values chosen using receiver operating characteristic curve analysis. Results: There were 139 patients meeting inclusion criteria, with a mean age of 56.4 years and diagnoses of myelopathy (n=36), radiculopathy (n=48) and myeloradiculopathy (n=49). There were significant improvements in PROMIS PF, PROMIS PI, NDI, and SF-36 preoperatively to postoperatively (P<0.001). The test-retest reliability of all tests was excellent (intraclass correlation coefficients=0.87–0.94). PROMIS, SF-36, and NDI were all correlated with the anchor question (|r|=0.34–0.48, P<0.001). MCIDs were 8.5 (NDI), 11.1 (SF-36 Physical Component Score), 9.7 (SF-36 Mental Component Score), 4.9 (PROMIS PI), and 4.5 (PROMIS PF). SCB was 13.0 (NDI), 24.0 (SF-36 Physical Component Score), 11.8 (SF-36 Mental Component Score), 6.9 (PROMIS PI), and 6.8 (PROMIS PF). MCIDs were greater than standard error of measurement for all measures. Conclusions: We report MCID of 4.9 (PI) and 4.5 (PF) and SCB of 6.9 (PI) and 6.8 (PF). These data support the use of PROMIS computer adaptive tests in cervical spine patients and provide important reference as PROMIS reporting becomes more widespread in the literature.

How Does Screw Migration or Fracture After Anterior Cervical Plate Fixation Affect the Radiographic and Clinical Outcomes? Study Design: A retrospective cohort study. Objective: The objective of this article is to assess the effect of screw migration and fracture associated with anterior cervical plating on long-term radiographic and clinical outcomes. Background Data: Screw migration and breakage detected after anterior cervical discectomy/corpectomy and fusion with plating may cause various implant-related complications and reduce solid fusion rate. However, little is known about their long-term prognosis. Materials and Methods: Medical records and radiographic data of 248 consecutive patients who underwent anterior cervical discectomy and fusion or anterior cervical corpectomy and fusion with a dynamic plating system and were followed up for ≥2 years were retrospectively reviewed. Patients who experienced screw migration or breakage were classified as screw failure group (SF group, n=25). Patients without screw loosening or fracture until the last follow-up were defined as the nonfailure group (NF group, n=223). Visual analogue scales for neck pain, arm pain, and neck disability index were assessed. Radiologic measurements were performed to analyze solid fusion. The solid union was defined as interspinous motion ≤1 mm on flexion/extension lateral x-rays. Results: A number of levels fused was significantly associated with increased risk of screw failure (P<0.01). A total of 13 patients in the SF group achieved solid fusion at final follow-up, although fusion rates at all postoperative time points were significantly lower in the SF group than in the NF group, including at final follow-up (P<0.01). Failures in 23 (92%) screw failure patients developed at the lowermost instrumented vertebra. The SF and NF groups experienced similar degrees of neck pain, arm pain, and neck disturbance index scores. There were no cases of complete screw extrusion or related complications requiring revision surgery. Conclusion: Although screw failure increased the incidence of pseudarthrosis, it did not aggravate postoperative arm pain, neck pain, or neck disability. As failed implants rarely migrate to an extent that endangers tracheoesophageal structures, immediate removal is rarely necessary.

Improvements in Grip and Pinch Strength and Patient-reported Outcomes After Anterior Cervical Discectomy and Fusion Study Design: Prospective. Objective: To evaluate improvements in grip and pinch strength in patients with or without myelopathy and determine patient factors that are predictive of continued postoperative grip strength weakness. Summary of Background Data: The degree to which cervical myelopathy can diminish upper extremity muscle strength has not been objectively characterized. Few studies have investigated the association between the expected improvements in patient-reported outcomes (PROs) and strength in grip and pinch after anterior cervical discectomy and fusion (ACDF). Methods: Patients were asked to perform grip and pinch strength tests both preoperatively and at 6-month follow-up. Patients were also administered PRO surveys, which included Neck Disability Index, Short-Form-12 physical composite score and mental composite score, and Visual Analog Scale neck and arm pain scores. Receiver operating characteristic (ROC) curve analysis was used to determine optimum cutoff values of preoperative patient factors to predict postoperative dominant handgrip weakness after ACDF. Results: Patients with radiculopathy demonstrated a significantly greater improvement in Visual Analog Scale arm pain compared with patients with myelopathy. The ROC curve analysis determined the optimum cutoff for preoperative dominant handgrip strength to be 22 kgf. This value demonstrated a sensitivity of 0.89 and a specificity of 0.62. The area under the ROC curve value was 0.71 (95% confidence interval, 0.55–0.88), indicating fair prognostic accuracy of the cutoff for postoperative dominant handgrip weakness. Conclusions: In this prospective, observational study, postoperative increase in grip and pinch strength demonstrated an association with improvement of pain and disability of the neck and overall quality of health regardless of the presence of cervical myelopathy. Preoperative grip strength weakness was found to be predictive of postoperative grip strength deficiency after ACDF. Our investigation suggests the recovery of hand function may be correlated with improvement of PROs after ACDF.