The Impact of Upper Cervical Spine Alignment on Patient-reported Outcome Measures in Anterior Cervical Decompression and Fusion.

STUDY DESIGN: This was a retrospective cohort study. OBJECTIVE: To determine the extent to which the upper cervical spine compensates for malalignment in the subaxial cervical spine, and how changes in upper cervical spine sagittal alignment affect patient-reported outcomes. SUMMARY OF BACKGROUND DATA: Previous research has investigated the relationship between clinical outcomes and radiographic parameters in the subaxial cervical spine following anterior cervical discectomy and fusion (ACDF). However, limited research exists regarding the upper cervical spine (occiput to C2), which accounts for up to 40% of neck movement and has been hypothesized to compensate for subaxial dysfunction. MATERIALS AND METHODS: Patients undergoing ACDF for cervical radiculopathy and/or myelopathy at a single center with minimum 1-year follow-up were included. Radiographic parameters including cervical sagittal vertical axis, C0 angle, C1 inclination angle, C2 slope, Occiput-C1 angle (Oc-C1 degrees), Oc-C2 degrees, Oc-C7 degrees, C1-C2 degrees, C1-C7 degrees, and C2-C7 degrees cervical lordosis (CL) were recorded preoperatively and postoperatively. Delta (Δ) values were calculated by subtracting preoperative values from postoperative values. Correlation analysis as well as multiple linear regression analysis was used to determine relationships between radiographic and clinical outcomes. Alpha was set at 0.05. RESULTS: A total of 264 patients were included (mean follow-up 20 mo). C2 slope significantly decreased for patients after surgery (Δ=-0.8, P =0.02), as did parameters of regional cervical lordosis (Oc-C7 degrees, C1-C7 degrees, and C2-C7 degrees; P <0.001, <0.001, and 0.01, respectively). Weak to moderate associations were observed between postoperative CL and C1 inclination ( r =-0.24, P <0.001), Oc-C1 degrees ( r =0.59, P <0.001), and C1-C2 degrees ( r =-0.23, P <0.001). Increased preoperative C1-C2 degrees and Oc-C2 degrees inversely correlated with preoperative SF-12 Mental Composite Score (MCS-12) scores ( r =-0.16, P =0.01 and r =-0.13, P =0.04). Cervical sagittal vertical axis was found to have weak but significant associations with Short Form-12 (SF-12) Physical Composite Score (PCS-12) ( r =-0.13, P =0.03) and MCS-12 ( r =0.12, P =0.05). CONCLUSION: No clinically significant relationship between upper cervical and subaxial cervical alignment was detected for patients undergoing ACDF for neurological symptoms. Upper cervical spine alignment was not found to be a significant predictor of patient-reported outcomes after ACDF. LEVEL OF EVIDENCE: Level III.

Patient Factors Impacting Baseline Motor Evoked Potentials (MEPs) in Patients Undergoing Cervical Spine Surgery for Myelopathy or Radiculopathy.

STUDY DESIGN: Retrospective review of 2532 adults who underwent elective surgery for cervical radiculopathy or myelopathy with intraoperative neuromonitoring (IONM) with motor evoked potentials (MEPs) between 2017 and 2019. OBJECTIVE: Evaluate attainability of monitorable MEPs across demographic, health history, and patient-reported outcomes measure (PROM) factors. SUMMARY OF BACKGROUND DATA: When baseline IONM responses cannot be obtained, the value of IONM on mitigating the risk of postoperative deficits is marginalized and a clinical decision to proceed must be made based, in part, on the differential diagnosis of the unmonitorable MEPs. Despite known associations with baseline MEPs and anesthetic regimen or preoperative motor strength, little is known regarding associations with other patient factors. METHODS: Demographics, health history, and PROM data were collected preoperatively. MEP baseline responses were reported as monitorable or unmonitorable at incision. Multivariable logistic regression estimated the odds of having at least one unmonitorable MEP from demographic and health history factors. RESULTS: Age [odds ratio (OR)=1.031, P <0.001], sex (male OR=1.572, P =0.007), a primary diagnosis of myelopathy (OR=1.493, P =0.021), peripheral vascular disease (OR=2.830, P =0.009), type II diabetes (OR=1.658, P =0.005), and hypertension (OR=1.406, P =0.040) were each associated with increased odds of unmonitorable MEPs from one or more muscles; a history of thyroid disorder was inversely related (OR=0.583, P =0.027). P atients with unmonitorable MEPs reported less neck-associated disability and pain ( P <0.036), but worse SF-12 physical health and lower extremity (LE) and upper extremity function ( P <0.016). Compared with radiculopathy, unmonitorable MEPs in myelopathy patients more often involved LE muscles. Cord function was monitorable in 99.1% of myelopathic patients with no reported LE dysfunction and no history of hypertension or diabetes. CONCLUSION: Myelopathy, hypertension, peripheral vascular disease, diabetes, and/or symptomatic LE dysfunction increased the odds of having unmonitorable baseline MEPs. Unmonitorable baseline MEPs was uncommon in patients without significant LE weakness, even in the presence of myelopathy.

The Role of Family-wise Error Rate in Determining Statistical Significance.

The threshold for statistical significance is determined by the maximum allowable probability of Type I error (α). For studies that test multiple hypotheses or make multiple comparisons, the probability of at least 1 Type I error (family-wise error rate; FWER) increases as the number of hypotheses/comparisons increase. It is generally best practice to set the acceptable threshold for FWER to be less than or equal to α. Bonferroni correction and Tukey honestly significant difference test are 2 of the more common methods to control for FWER. When doing exploratory analysis or evaluating secondary outcomes of a study, it may not be necessary or desirable to control for FWER, which reduces the power of the study. However, deciding to control for FWER should be decided during the design of the study.

Power Analysis for Null Hypothesis Significance Testing.

Before conducting a scientific study, a power analysis is performed to determine the sample size required to test an effect within allowable probabilities of Type I error (α) or Type II error (ß). The power of a study is related to Type II error by 1-ß. Most scientific studies set α=0.05 and power=0.80 as minimums. More conservative study designs will decrease α or increase power, which will require a larger sample size. The third and final parameter required for a power analysis is the effect size (ES). ES is a measure of the strength of the observation in the outcome of interest (ie, the dependent variable). ES must be estimated from pilot studies or published values. A small ES will require a larger sample size than a large ES. It is possible to detect statistically significant findings even for very small ES, if the sample size is sufficiently large. Therefore, it is also essential to evaluate whether ES is sufficiently large to be clinically meaningful.

How Does Smoking Influence Patient-reported Outcomes in Patients After Lumbar Fusion?

STUDY DESIGN: A retrospective cohort study. OBJECTIVE: The goal of this study was to determine the effect of smoking on patient-reported outcome measurements (PROMs) after lumbar fusion surgery. SUMMARY OF BACKGROUND DATA: Although smoking is known to decrease fusion rates after lumbar fusion, there is less evidence regarding the influence of smoking on PROMs after surgery. METHODS: Patients undergoing between 1 and 3 levels of lumbar fusion were divided into 3 groups on the basis of preoperative smoking status: never smokers (NS); current smokers (CS); and former smokers (FS). PROMs collected for analysis include the Physical Component Score (PCS-12), Mental Component Score (MCS-12), Oswestry Disability Index (ODI), and Visual Analogue Scale back (VAS back) and leg (VAS leg) pain scores. Preoperative and postoperative PROMs were compared between groups. A multiple linear regression analysis was performed to determine whether preoperative smoking status was a predictor of change in PROM scores. RESULTS: A total of 220 (60.1%) NS, 52 (14.2%) CS, and 94 (25.7%) FS patients were included. Patients in most groups improved within each of the PROMs analyzed (P<0.05). VAS leg pain (P=0.001) was found to significantly differ between groups, with NS and FS having less disability than CS (3.6 vs. 2.0, P=0.010; and 3.6 vs. 2.4, P=0.022; respectively). Being a CS significantly predicted less improvement in ODI (P=0.035), VAS back (P=0.034), and VAS leg (P<0.001) compared with NS. In addition, NS had a significantly lower 30-day readmission rate than CS or FS (3.2% vs. 5.8% and 10.6%, respectively, P=0.029). CONCLUSION: CS exhibited worse postoperative VAS leg pain and a lower recovery ratio than never smokers. In addition, being in the CS group was a significant predictor of decreased improvement in ODI, VAS back, and VAS leg scores. LEVEL OF EVIDENCE: Level III.

Processing and Handling Cost of Single-use Versus Traditional Instrumentation for 1 Level Lumbar Fusions.

STUDY DESIGN: A single center, observational prospective clinical study. OBJECTIVE: The aim of this study was to compare the instrumentation-related cost and efficiency of single-use instrumentation versus traditional reusable instrument trays. SUMMARY OF BACKGROUND DATA: Single-use instrumentation provides the opportunity to reduce costs associated with cleaning and sterilizing instrumentation after surgery. Although previous studies have shown single-use instrumentation is effective in other orthopedic specialties, it is unclear if single-use instrumentation could provide economic advantages in spine surgery. MATERIALS AND METHODS: A total of 40 (20 reusable instrumentation and 20 single-use instrumentation) lumbar decompression (1-3 level) and fusion (1 level) spine surgeries were collected. Instrument handling, opening, setup, re-stocking, cleaning, sterilization, inspection, packaging, and storage were recorded by direct observation for both reusable and single-use instrumentation. The rate of infection was noted for each group. RESULTS: Mean time of handling instruments by the scrub nurse was 11.6 (±3.9) minutes for reusable instrumentation and 2.1 (±0.5) minutes for single-use instrumentation. Mean cost of handling reusable instruments was estimated to be $8.52 (±$2.96) per case, and the average cost to reprocess a single tray by Sterilization Processing Department (SPD) was $58. Thus, the median cost for sterilizing 2 reusable trays per case was $116, resulting in an average total Costresuable of $124.52 (±$2.96). Mean cost of handling single-use instrumentation was estimated to be $1.57 ($0.38) per case. CONCLUSION: Single-use instrumentation provided greater cost savings and reduced time from the opening of instrumentation to use in surgery when compared with reusable instrumentation.

Propensity Score Matching: A Statistical Method.

Propensity score matching (PSM) is a commonly used statistical method in orthopedic surgery research that accomplishes the removal of confounding bias from observational cohorts where the benefit of randomization is not possible. An alternative to multiple regression analysis, PSM attempts to reduce the effects of confounders by matching already treated subjects with control subjects who exhibit a similar propensity for treatment based on preexisting covariates that influence treatment selection. It, therefore, establishes a new control group by discarding outlier control subjects. This new control group reduces the unwanted influences of covariates, allowing for proper measurement of the intended variable. An example from orthopedic spine literature is discussed to illustrate how PSM may be applied in practice. PSM is uniquely valuable in its utility and simplicity, but it is limited in that it requires the removal of data and works primarily on binary treatments. In addition to matching, the propensity score can be used for stratification, covariate adjustments, and inverse probability of treatment weighting, but these topics are outside the scope of this paper. Personnel in the orthopedic field would benefit from learning about the function and application of this method given its common use in the orthopedic literature.

Wearable Technology in Spine Surgery.

Although patient-reported outcome measures (PROMs) provide valuable insight into the effectiveness of spine surgery, there still remain limitations on measuring outcomes in this manner. Among other deficiencies, PROMs do not always correlate with more objective measures of surgery success. Wearable technology, such as pedometers, tri-axis accelerometer, or wearable cameras, may allow physicians to track patient progress following spine surgery more objectively. Recently, there has been an emphasis on using wearable devices to measure physical activity and limb and spine function. Wearable devices could play an important role as a supplement to PROMs, although they might have to be substantiated through adequate controlled studies to identify normative data for patients presenting with common spine disorders. This review will detail the current state of wearable technology applications in spine surgery and its direction as its utilization expands.

Are Outcomes of Anterior Cervical Discectomy and Fusion Influenced by Presurgical Depression Symptoms on the Mental Component Score of the Short Form-12 Survey?

STUDY DESIGN: Retrospective comparative study. OBJECTIVE: The purpose of this study was to investigate whether preoperative depressive symptoms, measured by mental component score of the Short Form-12 survey (MCS-12), influence patient-reported outcome measurements (PROMs) following an anterior cervical discectomy and fusion (ACDF) surgery for cervical degeneration. SUMMARY OF BACKGROUND DATA: There is a paucity of literature regarding preoperative depression and PROMs following ACDF surgery for cervical degenerative disease. METHODS: Patients who underwent an ACDF for degenerative cervical pathology were identified. A score of 45.6 on the MCS-12 was used as the threshold for depression symptoms, and patients were divided into two groups based on this value: depression (MCS-12 ≤45.6) and nondepression (MCS-12 >45.6) groups. Outcomes including Neck Disability Index (NDI), physical component score of the Short Form-12 survey (PCS-12), and Visual Analogue Scale Neck (VAS Neck), and Arm (VAS Arm) pain scores were evaluated using independent sample t test, recovery ratios, percentage of patients reaching the minimum clinically important difference, and multiple linear regression - controlling for factors such as age, sex, and BMI. RESULTS: The depression group was found to have significantly worse baseline pain and disability than the nondepression group in NDI (P < 0.001), VAS Neck pain (P < 0.001), and VAS Arm pain (P < 0.001) scores. Postoperatively, both groups improved to a similar amount with surgery based on the recovery ratio analysis. The depression group continued to have worse scores than the nondepression group in NDI (P = 0.010), PCS-12 (P = 0.026), and VAS Arm pain (P = 0.001) scores. Depression was not a significant predictor of change in any PROMs based on regression analysis. CONCLUSION: Patients who presented with preoperative depression reported more pain and disability symptoms preoperatively and postoperatively; however, both groups achieved similar degrees of improvement. LEVEL OF EVIDENCE: 3.

Does an Uninstrumented Level Increase the Rate of Revision Surgery in a Multilevel Posterior Cervical Decompression and Fusion?

STUDY DESIGN: This was a retrospective cohort study. OBJECTIVE: The goal of this study is to determine if skipping a single level affects the revision rate for patients undergoing multilevel posterior cervical decompression and fusion (PCDF). SUMMARY OF BACKGROUND DATA: A multilevel PCDF is a common procedure for patients with cervical spondylotic myelopathy. With advanced pathology, it can be difficult to safely place screw instrumentation at every level increasing the risk of intraoperative and perioperative morbidity. It is unclear whether skipping a level during PCDF affects fusion and revision rates. PATIENTS AND METHODS: A cervical spine surgeries database at a single institution was used to identify patients who underwent ≥3 levels of PCDF. Inclusion criteria consisted of patients who had screws placed at every level or if they had a single level without screws bilaterally. Patients were excluded if the surgery was performed for tumor, trauma, or infection, and age below 18 years, or if there was <1 year of follow-up. RESULTS: A total of 157 patients met inclusion criteria, with 86 undergoing a PCDF with instrumentation at all levels and 71 that had a single uninstrumented level. Overall mean follow-up was 46.5±22.8 months. In patients with or without a skipped level, the revision rate was 25% and 26%, respectively (P<1.00). Univariate regression analysis demonstrated that proximal fixation level in the upper cervical region, having the fusion end at C7, prior surgery, and myelopathy were significant predictors of revision. Skipping a single level, however, was not predictive of revision. CONCLUSIONS: When performing a multilevel PCDF, there is no increase in the rate of revision surgery if a single level is uninstrumented. Conversely, other surgical factors, including the cranial and caudal levels, affect revision rates. In contrast to other reports, the C2 sagittal vertical axis did not affect reoperation rates. LEVEL OF EVIDENCE: Level IV.

Utilization of Time-driven Activity-based Costing to Determine the True Cost of a Single or 2-level Anterior Cervical Discectomy and Fusion.

STUDY DESIGN: This is a prospective case series. OBJECTIVE: To determine the actual cost of performing 1- or 2-level anterior cervical discectomy and fusion (ACDF) using actual patient data and the time-driven activity-based cost methodology. SUMMARY OF BACKGROUND DATA: As health care shifts to use value-based reimbursement, it is imperative to determine the true cost of surgical procedures. Time-driven activity-based costing determines the cost of care by determining the actual resources used in each step of the care cycle. MATERIALS AND METHODS: In total, 30 patients who underwent a 1- or 2-level ACDF by 3 surgeons at a specialty hospital were prospectively enrolled. To build an accurate process map, a research assistant accompanied the patient to every step in the care cycle including the preoperative visit, the preadmission testing, the surgery, and the postoperative visits for the first 90 days. All resources utilized and the time spent with every member of the care team was recorded. RESULTS: In total, 27 patients were analyzed. Eleven patients underwent a single-level ACDF and 16 underwent a 2-level fusion. The total cost for the episode of care was $29,299±$5048. The overwhelming cost driver was the hospital disposable costs ($13,920±$6325) which includes every item used during the hospital stay. Intraoperative personnel costs including fees for the surgeon, resident/fellow, anesthesia, nursing, surgical technician, neuromonitoring, radiology technician and orderlies, accounted for the second largest cost at $6066±$1540. The total cost excluding hospital overhead and disposables was $9071±$1939. CONCLUSIONS: Reimbursement for a bundle of care surrounding a 1- or 2-level ACDF should be no less than $29,299 to cover the true costs of the care for the entire care cycle. However, this cost may not include the true cost of all capital expenditures, and therefore may underestimate the cost.

Cervical Sagittal Range of Motion as a Predictor of Symptom Severity in Cervical Spondylotic Myelopathy.

STUDY DESIGN: A retrospective review of radiographic data and functional outcomes. OBJECTIVE: The aim of this study was to evaluate whether myelopathy symptom severity upon presentation corresponds to sagittal plane alignment or nonmyelopathy symptoms, such as pain, in patients with cervical spondylotic myelopathy (CSM). SUMMARY OF BACKGROUND DATA: Cervical sagittal balance is an important parameter in the outcome of surgical reconstruction. However, the effect of sagittal alignment on symptom severity in patients who have not undergone spine surgery is not well defined. METHODS: A consecutive series of CSM patients was identified at an academic institution. Preoperative radiographs were analyzed for sagittal vertical axis (C2SVA), C7 slope (C7S), C2-C7 angle in neutral (C27N), flexion (C27F), and extension (C27E), and range of motion (C27ROM). Neutral alignment was categorized as lordotic, kyphotic, or sigmoid/straight. Outcomes collected were SF-12, neck disability index, arm pain, neck pain, and modified JOA (mJOA). Pearson coefficients determined correlations between radiographic and outcome parameters. Multivariate regression evaluated predictive factors of mJOA. RESULTS: Radiographic parameters did not correlate with pain. Increasing age, smaller C27ROM, and smaller flexion angles correlated to lower (more severe) baseline mJOA scores. ROM (and not static alignment) was the only significant predictor of mJOA in the multivariate regression. Despite significant radiographic differences between lordotic, kyphotic, and sigmoid/straight alignment groups, myelopathy severity did not differ between these groups. CONCLUSION: Static, neutral alignment, including SVA and lordosis, did not correlate with myelopathy or pain symptoms. Greater C27ROM and increased maximal flexion corresponded to milder myelopathy symptoms, suggesting that patients with myelopathy may compensate for cervical stenosis with hyperflexion, similar to that which is observed in the lumbar spine. In a CSM patient population, dynamic motion and compensatory deformities may play a more significant role in myelopathy symptom severity than what can be discerned from standard, neutral position radiographs. LEVEL OF EVIDENCE: 3.