The effects of smoking on perioperative outcomes and pseudarthrosis following anterior cervical corpectomy: Clinical article

The Smokeless Paradox: Nontobacco Nicotine Use and Complications in Anterior Cervical Discectomy and Fusion

INTRODUCTION

Cervical fusion surgeries are commonly performed to stabilize the spine and relieve pain from various conditions. Recent increases in nontobacco nicotine product use, such as electronic cigarettes, present new challenges because of their unknown effects on spinal fusion outcomes. Our study aims to explore the effect of nontobacco nicotine dependence (NTND) on the success of cervical spinal fusions.

METHODS

We analyzed TriNetX database data for patients undergoing primary anterior cervical diskectomy and fusion, identified by specific Current Procedural Terminology codes, and categorized into cohorts based on a preoperative diagnosis of nicotine dependence, excluding those with tobacco use or dependence. Propensity matching in the ratio of 1:1 was done to control for demographics and body mass index. We analyzed 90-day medical and 2-year implant complications using chi-squared exact tests and univariate regressions within the matched cohorts.

RESULTS

The NTND and control cohorts comprised 5,331 and 43,033 patients, respectively. Five thousand two hundred thirty-two matched pairs of patients were included from each cohort as shown in Table 1. Our results indicate notable disparities in complications within 90 days postoperation between the cohorts. The NTND cohort had higher risks for opioid use (85.6% vs. 80.3%, P < 0.001), emergency department visits (13.0% vs. 8.40%, P < 0.001), opioid abuse (0.4% vs. 0.2%, P < 0.001), inpatient hospitalizations (20.0% vs. 17.4%, P < 0.001), and sepsis (1.40% vs. 0.80%, P = 0.01). At the 2-year follow-up, increases were observed in pseudarthrosis (14.0% vs. 9.60%, P < 0.001), adjacent segment disease (3.70% vs. 2.20%, P < 0.001), dysphagia (8.90% vs. 6.3%, P = 0.001), and revision surgery (2.00% vs. 1.40%, P = 0.02).

CONCLUSION

This study highlights notable postoperative complications in patients with NTND undergoing cervical spinal fusion.

Development and Validation of a Risk Prediction Model for Pseudarthrosis Following Transforaminal Lumbar Interbody Fusion: A Retrospective Analysis

BACKGROUND

Pseudarthrosis is a common complication of transforaminal lumbar interbody fusion (TLIF) that can affect the long-term prognosis and increase revision surgery risk. Therefore, it is crucial to investigate the risk factors associated with pseudarthrosis and develop a predictive model.

METHODS

Patients who underwent TLIF at a single hospital between January 2019 and June 2021 were included. Each patient's fusion status was determined based on thin-section lumbar spine computed tomography scans performed at least 1 year postoperatively. A nomogram was subsequently established to predict the probability of pseudarthrosis based on the results of least absolute shrinkage and selection operator and multivariable analysis. Receiver operating characteristic curve, calibration curve, and decision curve analysis were applied to evaluate the prediction effect and clinical value of the model.

RESULTS

In total, 284 patients (131 men [46.1%]; mean [standard deviation, SD] age, 63.0 [12.1] years) were included in the analysis (mean [SD] follow-up, 19.2 [9.2] months). The incidence of pseudarthrosis was 13.4% (38/284). In least absolute shrinkage and selection operator and multivariable analysis, independent risk factors for pseudarthrosis included history of smoking (odds ratio [OR]:2.966, 95% confidence interval [CI]: 1.135-7.750, P = 0.027), osteoporosis (OR = 6.362, 95% CI: 2.433-16.636, P < 0.001), and the change of mean disc height (OR = 2.401, 95% CI: 1.638-3.519, P < 0.001). The areas under the curves in the training and validation cohorts were 0.870 and 0.809, respectively.

CONCLUSIONS

History of smoking, osteoporosis, and change of mean disc height are all independent risk factors of pseudarthrosis following TLIF surgery; a nomogram based on these may help predict the probability of pseudarthrosis.

Pulsed Electromagnetic Fields for Cervical Spine Fusion in Patients with Risk Factors for Pseudarthrosis

Background

Certain demographics and/or risk factors contribute to complications following cervical spinal surgery including pseudarthrosis, prolonged pain, and reduced quality of life (QoL). Pulsed electromagnetic field (PEMF) stimulation is a non-invasive therapy that may enhance fusion success in at-risk patients.

Objective

To evaluate the safety and efficacy of post-operative adjunctive PEMF therapy following cervical spinal surgery in subjects at risk for pseudarthrosis.

Methods

This prospective, multicenter study investigated PEMF as an adjunctive therapy to cervical spinal fusion procedures in subjects at risk for pseudarthrosis based on having at least one of the following: prior failed fusion, multi-level fusion, nicotine use, osteoporosis, or diabetes. Radiographic fusion status and patient-reported outcomes (SF-36, EQ5D, NDI, and VAS-arm pain and VAS-neck pain) were assessed.

Results

A total of 160 subjects were assessed for fusion 12-months postoperative, and 144 subjects were successfully fused (90.0%). Fusion success for subjects with 1, 2+, or 3+ risk factors was 91.7%, 89.0%%, and 90.9%, respectively. Significant improvements in NDI, VAS-arm and VAS-neck were observed compared to baseline scores (p < 0.001) along with improvements in SF-36 and EQ5D (p < 0.001).

Conclusions

Adjunctive treatment with PEMF provides a high rate of successful fusion and significant improvements in pain, function, and quality of life despite having risk factors for pseudarthrosis.

Impact of surgical risk factors for non-union on lumbar spinal fusion outcomes using cellular bone allograft at 24-months follow-up

BACKGROUND

The current report investigates fusion rates and patient-reported outcomes following lumbar spinal surgery using cellular bone allograft (CBA) in patients with risk factors for non-union.

METHODS

A prospective, open label study was conducted in subjects undergoing lumbar spinal fusion with CBA (NCT02969616) to assess fusion success rates and patient-reported outcomes in subjects with risk factors for non-union. Subjects were categorized into low-risk (≤ 1 risk factors) and high-risk (> 1 risk factors) groups. Radiographic fusion status was evaluated by an independent review of dynamic radiographs and CT scans. Patient-reported outcome measures included quality of life (EQ-5D), Oswestry Disability Index (ODI) and Visual Analog Scales (VAS) for back and leg pain. Adverse event reporting was conducted throughout 24-months of follow-up.

RESULTS

A total of 274 subjects were enrolled: 140 subjects (51.1%) were categorized into the high-risk group (> 1 risk factor) and 134 subjects (48.9%) into the low-risk group (≤ 1 risk factors). The overall mean age at screening was 58.8 years (SD 12.5) with a higher distribution of females (63.1%) than males (36.9%). No statistical difference in fusion rates were observed between the low-risk (90.0%) and high-risk (93.9%) groups (p > 0.05). A statistically significant improvement in patient-reported outcomes (EQ-5D, ODI and VAS) was observed at all time points (p < 0.05) in both low and high-risk groups. The low-risk group showed enhanced improvement at multiple timepoints in EQ-5D, ODI, VAS-Back pain and VAS-Leg pain scores compared to the high-risk group (p < 0.05). The number of AEs were similar among risk groups.

CONCLUSIONS

This study demonstrates high fusion rates following lumbar spinal surgery using CBA, regardless of associated risk factors. Patient reported outcomes and fusion rates were not adversely affected by risk factor profiles.

TRIAL REGISTRATION

NCT02969616 (21/11/2016).

Adjunctive Use of Bone Growth Stimulation Increases Cervical Spine Fusion Rates in Patients at Risk for Pseudarthrosis

STUDY DESIGN

A prospective multicenter clinical trial (NCT03177473) was conducted with a retrospective cohort used as a control arm.

OBJECTIVE

The purpose of this study was to evaluate cervical spine fusion rates in subjects with risk factors for pseudarthrosis who received pulsed electromagnetic field (PEMF) treatment.

SUMMARY OF BACKGROUND DATA

Certain risk factors predispose patients to pseudarthrosis, which is associated with prolonged pain, reduced function, and decreased quality of life.

METHODS

Subjects in the PEMF group were treated with PEMF for 6 months postoperatively. The primary outcome measure was fusion status at the 12-month follow-up period. Fusion status was determined using anterior/posterior, lateral, and flexion/extension radiographs and computed tomography (without contrast).

RESULTS

A total of 213 patients were evaluated (PEMF, n=160; Control, n=53). At baseline, the PEMF group had a higher percentage of subjects who used nicotine ( P =0.01), had osteoporosis ( P <0.05), multi-level disease ( P <0.0001), and were >65 years of age ( P =0.01). The PEMF group showed over two-fold higher percentage of subjects that had ≥3 risk factors (n=92/160, 57.5%) compared with the control group (n=14/53, 26.4%). At the 12-month follow-up, the PEMF group demonstrated significantly higher fusion rates compared with the control (90.0% vs. 60.4%, P <0.05). A statistically significant improvement in fusion rate was observed in PEMF subjects with multi-level surgery ( P <0.0001) and high BMI (>30 kg/m 2 ; P =0.0021) when compared with the control group. No significant safety concerns were observed.

CONCLUSIONS

Adjunctive use of PEMF stimulation provides significant improvements in cervical spine fusion rates in subjects having risk factors for pseudarthrosis. When compared with control subjects that did not use PEMF stimulation, treated subjects showed improved fusion outcomes despite being older, having more risk factors for pseudarthrosis, and undergoing more complex surgeries.

Factors Associated With Nonunion After Cervical Fusion Surgery

Background Bony fusion is a critical factor in the outcome of cervical spinal fusion surgery. While several factors have been proposed to affect bony fusion, their relative importance remains unclear. This study aimed to investigate the factors associated with bony fusion after cervical spinal fusion surgery. Methods We retrospectively evaluated the significance of the various factors on bone fusion after cervical fusion surgery. Then, multivariate logistic regression analyses were performed to determine the independent factors associated with bony fusion. A receiver operating characteristic (ROC) analysis was performed to evaluate the cutoff threshold. Results This study included a total of 52 patients with a mean age of 64 years. Among them, 28 (54%) were male, and 39 (75.0%) achieved bony fusion. The multivariate logistic regression analysis showed that preoperative intact parathyroid hormone (PTH) levels (odds ratio, 1.04; 95% confidence interval, 1.01-1.08; p-value = 0.02) and hemoglobin A1c (HbA1c) levels (odds ratio, 2.87; 95% confidence interval, 1.07-8.74; p-value = 0.04) were significant factors associated with bony fusion after cervical fusion surgery. The optimum cutoff values of intact PTH and HbA1c were 63.5 pg/mL and 6.2%, respectively. Conclusions This study identified preoperative intact PTH and HbA1c as significant factors associated with bony fusion after cervical fusion surgery. These biomarkers can be used to identify patients at higher risk of nonunion to optimize patient conditions and guide preoperative and postoperative management strategies.

Longer Screws Decrease the Risk of Radiographic Pseudarthrosis Following Elective Anterior Cervical Discectomy and Fusion

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

In patients undergoing elective anterior cervical discectomy and fusion (ACDF), we sought to determine the impact of screw length on: (1) radiographic pseudarthrosis, (2) pseudarthrosis requiring reoperation, and (3) patient-reported outcome measures (PROMs).

METHODS

A single-institution, retrospective cohort study was undertaken from 2010-21. The primary independent variables were: screw length (mm), screw length divided by the anterior-posterior vertebral body diameter (VB%), and the presence of any screw with VB% < 75% vs all screws with VB% ≥ 75%. Multivariable logistic regression controlled for age, BMI, gender, smoking, American Society of Anesthesiology grade, number of levels fused, and whether a corpectomy was performed.

RESULTS

Of 406 patients undergoing ACDF, levels fused were: 1-level (39.4%), 2-level (42.9%), 3-level (16.7%), and 4-level (1.0%). Mean screw length was 14.3 ± 2.3 mm, and mean VB% was 74.4 ± 11.2. A total of 293 (72.1%) had at least one screw with VB% < 75%, 113 (27.8%) had all screws with VB% ≥ 75%, and 141 (34.7%) patients had radiographic pseudarthrosis at 1-year. Patients who had any screw with VB% < 75% had a higher rate of radiographic pseudarthrosis compared to those had all screws with VB% ≥ 75% (39.6% vs 22.1%, P < .001). Multivariable logistic regression revealed that a higher VB% (OR = .97, 95%CI = .95-.99, P = .035) and having all screws with VB% ≥ 75% (OR = .51, 95%CI = .27-.95, P = .037) significantly decreased the odds of pseudarthrosis at 1-year, with no difference in reoperation or PROMs (all P > .05).

CONCLUSION

Longer screws taking up ≥75% of the vertebral body protected against radiographic pseudarthrosis at 1-year. Maximizing screw length in ACDF is an easily modifiable factor directly under the surgeon's control that may mitigate the risk of pseudarthrosis.

Pseudoarthrosis after anterior cervical discectomy and fusion: rate of occult infections and outcome of anterior revision surgery

BACKGROUND

Pseudoarthrosis after anterior cervical discectomy and fusion (ACDF) is relatively common and can result in revision surgery. The aim of the study was to analyze the outcome of patients who underwent anterior revision surgery for pseudoarthrosis after ACDF.

METHODS

From 99 patients with cervical revision surgery, ten patients (median age: 48, range 37-74; female: 5, male: 5) who underwent anterior revision surgery for pseudoarthrosis after ACDF with a minimal follow up of one year were included in the study. Microbiological investigations were performed in all patients. Computed tomography (CT) scans were used to evaluate the radiological success of revision surgery one year postoperatively. Clinical outcome was quantified with the Neck Disability Index (NDI), the Visual Analog Scale (VAS) for neck and arm pain, and the North American Spine Society Patient Satisfaction Scale (NASS) 12 months (12-60) after index ACDF surgery. The achievement of the minimum clinically important difference (MCID) one year postoperatively was documented.

RESULTS

Occult infection was present in 40% of patients. Fusion was achieved in 80%. The median NDI was the same one year postoperatively as preoperatively (median 23.5 (range 5-41) versus 23.5 (7-40)), respectively. The MCID for the NDI was achieved 30%. VAS-neck pain was reduced by a median of 1.5 points one year postoperatively from 8 (3-8) to 6.5 (1-8); the MCID for VAS-neck pain was achieved in only 10%. Median VAS-arm pain increased slightly to 3.5 (0-8) one year postoperatively compared with the preoperative value of 1 (0-6); the MCID for VAS-arm pain was achieved in 14%. The NASS patient satisfaction scale could identify 20% of responders, all other patients failed to reach the expected benefit from anterior ACDF revision surgery. 60% of patients would undergo the revision surgery again in retrospect.

CONCLUSION

Occult infections occur in 40% of patients who undergo anterior revision surgery for ACDF pseudoarthrosis. Albeit in a small cohort of patients, this study shows that anterior revision surgery may not result in relevant clinical improvements for patients, despite achieving fusion in 80% of cases.

LEVEL OF EVIDENCE

Retrospective study, level III.

The Effects of Nicotine- and Cigarette-Related Products on Osteogenesis, Bone Formation, and Bone Mineralization: A Systematic Review

BACKGROUND

Many clinicians associate nicotine as the causative agent in the negative and deleterious effects of smoking on bone growth and spine fusion. Although nicotine is the primary driver of physiological addiction in smoking, isolated and controlled use of nicotine is one of the most effective adjuncts to quitting smoking.

OBJECTIVE

To explore the relationship between nicotine and noncombustion cigarette products on bone growth.

METHODS

One thousand five studies were identified, of which 501 studies were excluded, leaving 504 studies available for review. Of note, 52 studies were deemed to be irrelevant. Four hundred fifty-two studies remained for eligibility assessment. Of the remaining 452, 218 failed to assess study outcomes, 169 failed to assess bone biology, 13 assessed 5 patients or fewer, and 12 were deemed to be ineligible of the study criteria. Forty studies remained for inclusion within this systematic review.

RESULTS

Of the 40 studies identified for inclusion within the study, 30 studies were classified as "Animal Basic Science," whereas the remaining 10 were categorized as "Human Basic Science." Of the 40 studies, 11 noted decreased cell proliferation and boney growth, whereas 8 showed an increase. Four studies noted an increase in gene expression products, whereas 11 noted a significant decrease.

CONCLUSION

The results of this study demonstrate that nicotine has a variety of complex interactions on osteoblast and osteoclastic activities. Nicotine demonstrates dose-dependent effects on osteoblast proliferation, boney growth, and gene expression. Further study is warranted to extrapolate the effects of solitary nicotine on clinical outcomes.

Intervertebral disc degeneration-Current therapeutic options and challenges

Degeneration of the intervertebral disc (IVD) is a normal part of aging. Due to the spine's declining function and the development of pain, it may affect one's physical health, mental health, and socioeconomic status. Most of the intervertebral disc degeneration (IVDD) therapies today focus on the symptoms of low back pain rather than the underlying etiology or mechanical function of the disc. The deteriorated disc is typically not restored by conservative or surgical therapies that largely focus on correcting symptoms and structural abnormalities. To enhance the clinical outcome and the quality of life of a patient, several therapeutic modalities have been created. In this review, we discuss genetic and environmental causes of IVDD and describe promising modern endogenous and exogenous therapeutic approaches including their applicability and relevance to the degeneration process.

Comparative Study of Anterior Transvertebral Foraminotomy and Anterior Cervical Discectomy and Fusion for Unilateral Cervical Spondylotic Radiculopathy

OBJECTIVE

To study the compared surgical and radiographic outcomes of Transvertebral foraminotomy (TVF) with anterior cervical discectomy and fusion (ACDF) in patients with unilateral cervical spondylotic radiculopathy (CSR).

METHODS

We performed a retrospective comparative study of 72 consecutive patients with 1- or 2-level CSR treated with ACDF or TVF. 27 patients who underwent TVF (group T) and 45 patients who underwent ACDF (group A) with a minimum 2-year follow-up were enrolled. We evaluated clinical outcomes and radiological assessment. Clinical outcome included Visual analog scale (VAS) scores for axial, arm pain at preoperatively and final follow-up. VAS score for painful swallowing was also evaluated 1 week after surgery. Radiological assessment included C2-7 sagittal Cobb angle (C2-7 CA), range of motion (ROM) of C2-7 CA, the height, angle and ROM of the functional spinal unit (FSU), and tip of the spinous process of the operated segment. We also evaluated the disc height, FSU angle, and ROM of the FSU at the cranial adjacent segment.

RESULTS

Both groups had good clinical outcomes. Soft tissue swelling was significantly less prominent in group T than that for group A. VAS scores for painful swallowing is lower in group T without significant difference. The ROM of C2-7 CA, FSU, and spinous processes demonstrated a significant reduction in group A compared with group T.(P < 0.05). Disc height at the cranial adjacent segment was maintained in group T.

CONCLUSIONS

TVF is as effective as ACDF for unilateral CSR and preserves whole cervical spine and segmental alignment.

The Risk of Adverse Events in Smokers Undergoing Spinal Fusion: A Systematic Review and Meta-Analysis

STUDY DESIGN

Systematic review and meta-analysis.

OBJECTIVES

Determine if tobacco use is associated with increased risk of postoperative adverse events within 90 days in patients undergoing spinal fusion surgery.

METHODS

Databases were queried to identify cohort studies that directly compared smokers with non-smokers and provided the absolute number of adverse events and the population at risk. Data quality was evaluated using the Quality in Prognosis Studies tool. Risk ratios (RR) and 95% confidence intervals were calculated and compared between studies. The grading of recommendation, assessment, development and evaluation (GRADE) criteria were used to assess the strength of the evidence.

RESULTS

Seventeen studies assessing 37 897 participants met the inclusion criteria. Of these, 10 031 (26.5%) were smokers and 27 866 (73.5%) were nonsmokers. The mean age for the study population was 58 years, and 45% were males. Smoking was not associated with increased risk of one or more major adverse events within 90 days following spine surgery (seven studies, pooled RR 1.13, 95% CI [.75-1.71], I2 = 41%). However, smoking was significantly associated with one or more major adverse events in ≤2 level fusion (three studies, pooled RR 2.46, 95% CI [1.18-5.12], I2 = 0%), but not in fusions of ≥3 levels (four studies, pooled RR .87, 95% CI [.70-1.08], I2 = 0%). Additionally, there was no statistically significant association between smoking and any adverse event, nor increased reoperation risk due to adverse events.

CONCLUSIONS

In this meta-analysis, tobacco use was not associated with a statistically significant increased risk of adverse events within 90 days in patients undergoing spinal fusion surgery. Our results are limited by the variable reporting methodology for both complication rates as well as smoking incidence between the included individual studies.

Anesthesiologists and the Other Pandemic: Tobacco Use

Tobacco use will kill a projected 1 billion people in the 21st century in one of the deadliest pandemics in history. Tobacco use disorder is a disease with a natural history, pathophysiology, and effective treatment options. Anesthesiologists can play a unique role in fighting this pandemic, providing both immediate (reduction in perioperative risk) and long-term (reduction in tobacco-related diseases) benefits to their patients who are its victims. Receiving surgery is one of the most powerful stimuli to quit tobacco. Tobacco treatments that combine counseling and pharmacotherapy (e.g., nicotine replacement therapy) can further increase quit rates and reduce risk of morbidity such as pulmonary and wound-related complications. The perioperative setting provides a great opportunity to implement multimodal perianesthesia tobacco treatment, which combines multiple evidence-based tactics to implement the four core components of consistent ascertainment and documentation of tobacco use, advice to quit, access to pharmacotherapy, and referral to counseling resources.

Relationship between smoking and postoperative complications of cervical spine surgery: a systematic review and meta-analysis

To determine whether smoking has adverse effects on postoperative complications following spine cervical surgery (PROSPERO 2021: CRD42021269648). We searched PubMed, Embase, Cochrane Library, and Web of Science through 13 July 2021 for cohort and case–control studies that investigated the effect of smoking on postoperative complications after cervical spine surgery. Two researchers independently screened the studies and extracted data according to the selection criteria. The meta-analysis included 43 studies, including 27 case–control studies and 16 cohort studies, with 10,020 patients. Pooled estimates showed that smoking was associated with overall postoperative complications (effect estimate [ES] = 1.99, 95% confidence interval [CI]: 1.62–2.44, p < 0.0001), respiratory complications (ES = 2.70, 95% CI: 1.62–4.49, p < 0.0001), reoperation (ES = 2.06, 95% CI: 1.50–2.81, p < 0.0001), dysphagia (ES = 1.49, 95% CI: 1.06–2.10, p = 0.022), wound infection (ES = 3.21, 95% CI: 1.62–6.36, p = 0.001), and axial neck pain (ES = 1.98, 95% CI: 1.25–3.12, p = 0.003). There were no significant differences between the smoking and nonsmoking groups in terms of fusion (ES = 0.97, 95% CI: 0.94–1.00, p = 0.0097), operation time (weighted mean difference [WMD] = 0.08, 95% CI: −5.54 to 5.71, p = 0.977), estimated blood loss (WMD = −5.31, 95% CI: −148.83 to 139.22, p = 0.943), length of hospital stay (WMD = 1.01, 95% CI: −2.17 to 4.20, p = 0.534), Visual Analog Scale-neck pain score (WMD = −0.19, 95% CI: −1.19 to 0.81, p = 0.707), Visual Analog Scale-arm pain score (WMD = −0.50, 95% CI: −1.53 to 0.53, p = 0.343), Neck Disability Index score (WMD = 11.46, 95% CI: −3.83 to 26.76, p = 0.142), or Japanese Orthopedic Association Scores (WMD = −1.75, 95% CI: −5.27 to 1.78, p = 0.332). Compared with nonsmokers, smokers seem to be more significantly associated with overall complications, respiratory complications, reoperation, longer hospital stay, dysphagia, wound infection and axial neck pain after cervical spine surgery. It is essential to provide timely smoking cessation advice and explanation to patients before elective cervical spine surgery.

Pseudarthrosis of the Cervical Spine

Pseudarthrosis of the cervical spine represents a common and challenging problem for spine surgeons. Rates vary greatly from as low as 0%-20% to >60% and depend heavily on patient factors, approach, and number of levels. While some patients remain asymptomatic from pseudarthrosis, many require revision surgery due to instability, continued neck pain, or radiculopathy/myelopathy. We aimed to provide a practical, narrative review of cervical pseudarthrosis to address the following areas: (1) definitions, (2) incidence, (3) risk factors, (4) presentation and workup, (5) treatment decision-making, and (6) postoperative care. It is our hope the current review provides a concise summary for how to diagnose and treat challenging cervical nonunions.

The Risk of Nonunion in Smokers Revisited: A Systematic Review and Meta-Analysis

STUDY DESIGN

Systemic review and meta-analysis.

OBJECTIVE

To review and establish the effect of tobacco smoking on risk of nonunion following spinal fusion.

METHODS

A systematic search of Medline, Embase, Cochrane Central Register of Controlled Trials, and the Cochrane Database of Systematic Reviews from inception to December 31, 2020, was conducted. Cohort studies directly comparing smokers with nonsmokers that provided the number of nonunions and fused segments were included. Following data extraction, the risk of bias was assessed using the Quality in Prognosis Studies Tool, and the strength of evidence for nonunion was evaluated using the GRADE working group criteria. All data analysis was performed in Review Manager 5, and a random effects model was used.

RESULTS

Twenty studies assessing 3009 participants, which included 1117 (37%) smokers, met inclusion criteria. Pooled analysis found that smoking was associated with increased risk of nonunion compared to not smoking ≥1 year following spine surgery (RR 1.91, 95% CI 1.56 to 2.35). Smoking was significantly associated with increased nonunion in those receiving either allograft (RR 1.39, 95% CI 1.12 to 1.73) or autograft (RR 2.04, 95% CI 1.54 to 2.72). Both multilevel and single level fusions carried increased risk of nonunion in smokers (RR 2.30, 95% CI 1.64 to 3.23; RR 1.79, 95% CI 1.12 to 2.86, respectively).

CONCLUSION

Smoking status carried a global risk of nonunion for spinal fusion procedures regardless of follow-up time, location, number of segments fused, or grafting material. Further comparative studies with robust methodology are necessary to establish treatment guidelines tailored to smokers.

Diagnosis of reoperated cervical non-union: Multicenter retrospective study about 45 patients

INTRODUCTION

Non-union is one of the main complications of single- or multi-level cervical spine fusion, considerably impairing functional results. The aim of this study was to evaluate the respective contributions of imaging examinations in the diagnostic process, the challenge being to avoid inappropriate surgery and unnecessary complementary examinations.

MATERIAL AND METHOD

A retrospective multicenter study included all patients managed for cervical spine non-union between 2008 and 2018. We evaluated the imaging examinations performed on each patient and determined signs of non-union in each image.

RESULTS

The study included 45 patients in 4 centers: 55% female; mean age, of 48±8.0 years; 57% smokers. Systematic static radiography showed signs of non-union in 55% of cases. Dynamic X-ray was performed in 34% of patients, and showed hypermobility of the level in 80% of cases. CT supported diagnosis of non-union in 97% of cases, and MRI in 48%. SPECT-CT was positive in all cases of non-union.

DISCUSSION

Dynamic X-ray is rarely prescribed, but frequently provided an objective measure of hypermobility of the level in non-union, justifying first-line use. Millimetric-slice CT was reliable for diagnosis. MRI is relevant only once diagnosis has been made, as part of preoperative work-up. Nuclear imaging can be useful in order to solve doubtful cases.

CONCLUSION

In suspected cervical spine non-union, we recommend dynamic X-rays (flexion/extension) and CT-scan as first-line diagnosis examinations.

LEVEL OF EVIDENCE

IV.

The Effect of Smoking on the Fusion Rate of Spinal Fusion Surgery: A Systematic Review and Meta-Analysis

OBJECTIVE

To conduct a systematic review and meta-analysis comparing the fusion rate after spinal fusion surgery between smokers and nonsmokers.

METHODS

We searched PubMed, Embase, Cochrane Library, and Web of Science electronic databases through March 10, 2021 for cohort and case-control studies assessing the effect of smoking on the fusion rate of spinal fusion surgery. Two researchers independently screened the literature and extracted data according to the inclusion and exclusion criteria. Statistical analysis was performed using RevMan, version 5.4.

RESULTS

A total of 26 studies, including 4 case-control studies and 22 cohort studies, with 4409 patients, were included in the present meta-analysis. Follow-up was at least 6 months. Overall, the pooled results demonstrated that the fusion rate of smokers after spinal fusion was significantly lower than that of nonsmokers. The odds ratio (OR) was 0.55 (95% confidence interval [CI] 0.45-0.67, P < 0.0001). Subgroup analyses by fusion level showed the adverse effect of smoking on the fusion rate at single level (OR 0.61, 95% CI 0.41-0.91, P = 0.02) was more significant than that of multiple levels (OR 0.55, 95% CI 0.38-0.80, P = 0.0010). Subgroup analysis according to the type of bone graft revealed an apparent association between smoking and fusion rate in the autograft subgroup (OR 0.47, 95% CI 0.33-0.66, P < 0.0001) but not in the allograft subgroup (OR 0.69, 95% CI 0.47-1.01, P = 0.06).

CONCLUSIONS

The fusion rate of smokers is significantly lower than that of nonsmokers in spinal fusion surgery. Smokers should be encouraged to quit smoking to improve the outcome of spinal fusion surgery.

Safety and efficacy of low-dose rhBMP-2 use for anterior cervical fusion

OBJECTIVE

The use of recombinant human bone morphogenetic protein 2 (rhBMP-2) in routine anterior cervical fusion (ACF) is controversial. Early reports described high complication rates. A variety of dosing regimens ranging from 0.6 to 2.1 mg per level fused have been reported. The authors hypothesized that the high amounts of rhBMP-2 used in these studies led to the high complication rates observed; therefore, they set out to evaluate the safety and efficacy of low-dose rhBMP-2 for use in ACFs.

METHODS

Patient inclusion criteria were 1) age 18 to 70 years; 2) initial stand-alone ACF construct; 3) fusion augmentation with rhBMP-2; and 4) at least 1 year of radiographic follow-up. A successful fusion was defined by either 1) lateral flexion-extension radiographs with less than 1 mm of movement across the fused spinous processes, or 2) bone bridging at least half of the fusion area originally achieved by surgery on fine-cut CT. Patient demographics, perioperative data, and postoperative complications were recorded.

RESULTS

A total of 198 patients met the inclusion criteria and were included for analysis. Sixty-two patients (31%) were smokers. The median number of levels fused was 2 (IQR 1.25). The mean dose of rhBMP-2 was 0.50 ± 0.09 mg per level. Twenty-two (11%) patients experienced dysphagia. Eleven (6%) patients experienced cervical swelling. Two (1%) patients returned to the operating room (OR) for postoperative hematoma. One (0.5%) patient returned to the OR for seroma. Two (1%) patients experienced pseudarthrosis requiring a posterior fusion. Three (2%) patients experienced a new postoperative neurological deficit that had recovered by last the follow-up. Overall, 190 (96%) patients experienced solid arthrodesis over an average of 15 months of follow-up. There was no difference in fusion rates between patients who were either smokers or nonsmokers (p = 0.7073).

CONCLUSIONS

The use of low-dose rhBMP-2 safely and effectively augmented anterior cervical arthrodesis. The low-dose protocol assessed in this study appeared to significantly reduce complications associated with rhBMP-2 use in ACF compared with the literature. The authors have determined that using low-dose rhBMP-2 in patients who are smokers, those with multilevel ACFs, or others at high risk of developing pseudarthrosis is recommended.

Failure in Cervical Spinal Fusion and Current Management Modalities

Failed fusion in the cervical spine is a multifactorial problem stemming from a combination of patient and surgical factors. Patient-related risk factors such as steroid use, poor bone quality, and smoking can be optimized preoperatively. Age, prior radiation, prior surgery, and underlying genetics are nonmodifiable patient-centered risk factors. Surgical risks for failed fusion include the number of segments fused, anterior versus posterior approach for fusion, the type of bone graft, and the instrumentation utilized. Many symptomatic cases of failed fusion (pseudarthrosis) result in pain, neurological deficits, or loosened hardware necessitating a revision surgery consisting of extending the prior construct and utilizing additional allografts or autografts to augment the fusion. Given the relatively mobile nature of the cervical spine, pseudoarthrosis (either known or anticipated) must be recognized by the spine surgeon, and steps should be considered to optimize the likelihood of future fusion. This consists of both performing a rigid fixation and using appropriate bone graft to enhance the environment for arthrodesis. Vascularized bone grafts are a useful tool to augment fusion and provide added structural stability in cases at high risk of pseudoarthrosis.

Adverse impact of smoking on the spine and spinal surgery

Background

Tobacco smokers and companies are well aware that smoking increases the risks for cancers, vascular morbidity, and early mortality. This is a review of the plethora of adverse effects chronic smoking has on spinal tissues and spinal surgery.

Methods

Medline (PubMed) and Google Scholar databases were searched for pertinent literature through keywords related to smoking, spondylosis, and spinal surgery.

Results

Smoking accelerates spondylosis by impairing spinal tissue vascular supply through atherosclerosis and thrombosis, while inducing local hypoxia, inflammation, proteolysis, and cell loss. It, thus, compromises disc, cartilage, synovium, bone, and blood vessels. It can lead to early surgery, delayed wound healing, increased surgical site infection, failed fusion, more re-operations, and chronic spinal pain.

Conclusion

There is ample evidence to support surgeons' declining to operate on chronic smokers. The need for immediate and permanent smoking cessation and its potential benefits should be emphasized for the patient considering or who has undergone spinal surgery.

Three- and 4-Level Lumbar Arthrodesis Using Adjunctive Pulsed Electromagnetic Field Stimulation: A Multicenter Retrospective Evaluation of Fusion Rates and a Review of the Literature

BACKGROUND

The incidence of 3- and 4-level lumbar arthrodesis is rising due to an aging population, and fusion rates affect clinical success in this population. Pulsed electromagnetic field (PEMF) stimulation is used as an adjunct to increase fusion rates following multilevel arthrodesis. The purpose of the study was to evaluate the fusion rates for subjects who underwent 3- and 4-level lumbar interbody arthrodesis following PEMF treatment.

METHODS

In this retrospective, multicenter study, patient charts that listed 3- or 4-level lumbar arthrodesis with adjunctive use of a PEMF device were evaluated. Inclusion criteria included patients who were diagnosed with lumbar degenerative disease, spinal stenosis, and/or spondylolisthesis (grade 1 or 2). A radiographic evaluation of fusion status was performed at 12 months by the treating physicians. Fusion rates were stratified by graft material, surgical interbody approach, and certain clinical risk factors for pseudoarthrosis.

RESULTS

A total of 55 patients were identified who had a 12-month follow-up. The radiographic fusion rate was 92.7% (51 patients) at 12 months. There were no significant differences in fusion rates for patients treated with allograft or autograft, for patients with different interbody approaches, or for those with or without certain clinical risk factors.

CONCLUSIONS

With modern fusion techniques and PEMF, the overall fusion rate was high following 3- and 4-level lumbar arthrodesis.

LEVEL OF EVIDENCE

4.

CLINICAL RELEVANCE

PEMF may be a useful adjunct for treatment of patients with surgical risk factors, such as multilevel arthrodesis, and clinical risk factors.

Nonunion Rates After Anterior Cervical Discectomy and Fusion: Comparison of Polyetheretherketone vs Structural Allograft Implants

BACKGROUND

Although advances in implant materials, such as polyetheretherketone (PEEK), have been developed aimed to improve outcome after anterior cervical discectomy and fusion (ACDF), it is essential to confirm whether these changes translate into clinically important sustained benefits.

OBJECTIVE

To compare the radiographic and clinical outcomes of patients undergoing up to 3-level ACDF with PEEK vs structural allograft implants.

METHODS

In this cohort study, radiographic and symptomatic nonunion rates were compared in consecutive patients who underwent 1 to 3 level ACDF with allograft or PEEK implant. Prospectively collected clinical data and patient-reported outcome (PRO) scores were compared between the allograft and PEEK groups. Regression analysis was performed to determine the predictors of nonunion.

RESULTS

In total, 194 of 404 patients met the inclusion criteria (79% allograft vs 21% PEEK). Preoperative demographic variables were comparable between the 2 groups except for age. The rate of radiographic nonunion was higher with PEEK implants (39% vs 27%, P = .0035). However, a higher proportion of nonunion in the allograft cohort required posterior instrumentation (14% vs 3%, P = .039). Patients with multilevel procedures and PEEK implants had up to 5.8 times the risk of radiographic nonunion, whereas younger patients, active smokers, and multilevel procedures were at higher risk of symptomatic nonunion.

CONCLUSION

Along with implant material, factors such as younger age, active smoking status, and the number of operated levels were independent predictors of fusion failure. Given the impact of nonunion on PRO, perioperative optimization of modifiable factors and surgical planning are essential to ensure a successful outcome.

The Association of Preoperative Smoking With Postoperative Outcomes in Patients Undergoing Total Hip Arthroplasty

BACKGROUND

Preoperative smoking is an easily modifiable risk factor and has associations with increased postoperative morbidity and mortality. It is important to clarify these risks for specific procedures to provide improved and evidence-based quality of care. The purpose of the present study aims to identify the associations between preoperative smoking and 30-day postoperative outcomes in patients undergoing total hip arthroplasty.

METHODS

We used R statistics to conduct a multivariable logistic regression analysis followed by a propensity score matching analysis to explore the association between preoperative smoking and postoperative outcomes.

RESULTS

A final cohort of 67,897 patients who underwent total hip arthroplasty was selected for analysis. After adjusting for potential confounders, the odds of postoperative pulmonary complications (odds ratio [OR], 1.352; 95% confidence interval [95% CI], 1.075-1.700; P = .01), infectious complications (OR, 1.310; 95% CI, 1.094-1.567; P = .003), and extended hospital stay (OR, 1.17; 95% CI, 1.099-1.251; P < .001) were all significantly higher in the smoking population. After propensity matching these cohorts, both infectious complications (P = .017) and extended hospital stays (P = .001) were significantly higher in smoking patients.

CONCLUSIONS

After controlling for potential confounding variables, our multivariable regression analysis revealed a significant increase in pulmonary and infectious complications as well as significantly longer hospital stays in our smoking population. When using a propensity score matching analysis, an increase in infectious complications as well as extended hospital stay was observed. Given the concerning prevalence of smoking in the United States, our data provide updated information toward a growing mass of literature supporting smoking cessation before surgical operations.

The influence of smoking in minimally invasive spinal fusion surgery

Background

The impact of smoking on spinal surgery has been studied extensively, but few investigations have focused on minimally invasive surgery (MIS) of the spine and the difference between complication rates in smokers and non-smokers. We evaluated whether a history of at least one pack-year preoperatively could be used to predict adverse peri- and postoperative outcomes in patients undergoing minimally invasive fusion procedures of the lumbar spine. In a prospective study, we assessed the clinical effectiveness of MIS in an unselected population of 187 patients.

Methods

We evaluated perioperative and postoperative complication rates in MIS fusion techniques of the lumbar spine in smoking and non-smoking patients. MIS fusion was performed using interbody fusion procedures and/or posterolateral fusion alone.

Results

Smokers were significantly younger than non-smokers. We did not encounter infection at the site of surgery or severe wound healing disorder in smokers. We registered no difference between the smoking and non-smoking groups with regard to peri- or postoperative complication rate, blood loss, or length of stay in hospital. We found a significant influence of smoking (p = 0.049) on the overall perioperative complication rate.

Conclusion

MIS fusion techniques seem to be a suitable tool for treating degenerative spinal disorders in smokers.

Does Smoking Status Influence Health-Related Quality of Life Outcome Measures in Patients Undergoing ACDF?

STUDY DESIGN

Retrospective comparative study.

OBJECTIVE

Whereas smoking has been shown to affect the fusion rates for patients undergoing an anterior cervical discectomy and fusion (ACDF), the relationship between smoking and health-related quality of life outcome measurements after an ACDF is less clear. The purpose of this study was to evaluate whether smoking negatively affects patient outcomes after an ACDF for cervical degenerative pathology.

METHODS

Patients with tumor, trauma, infection, and previous cervical spine surgery and those with less than a year of follow-up were excluded. Smoking status was assessed by self-reported smoking history. Patient outcomes, including Neck Disability Index, Short Form 12 Mental Component Score, Short Form 12 Physical Component Score (PCS-12), Visual Analogue Scale (VAS) arm pain, VAS neck pain, and pseudarthrosis rates were evaluated. Outcomes were compared between smoking groups using multiple linear and logistic regression, controlling for age, sex, and body mass index (BMI), among other factors. A P value <.05 was considered significant.

RESULTS

A total of 264 patients were included, with a mean follow-up of 19.8 months, age of 53.1 years, and BMI of 29.6 kg/m2. There were 43 current, 69 former, and 152 nonsmokers in the cohort. At baseline, nonsmokers had higher PCS-12 scores than current smokers (P = .010), lower VAS neck pain than current (P = .035) and former (P = .014) smokers, as well as lower VAS arm pain than former smokers (P = .006). Postoperatively, nonsmokers had higher PCS-12 scores than both current (P = .030) and former smokers (P = .035). Smoking status was not a significant predictor of change in patient outcome in multivariate analysis.

CONCLUSIONS

Whereas nonsmokers had higher function and lower pain than former or current smokers preoperatively, smoking status overall was not found to be an independent predictor of outcome scores after ACDF. This supports the notion that smoking status alone should not deter patients from undergoing ACDF for cervical degenerative pathology.

No Difference in Functional Outcome but Higher Revision Rate Among Smokers Undergoing Cervical Artificial Disc Replacement: Analysis of a Spine Registry

BACKGROUND

Smoking is a known predictor of negative outcomes in spinal surgery. However, its effect on the functional outcomes and revision rates after ADR is not well-documented. This study is a retrospective analysis of prospectively collected data at a major tertiary center. The objective was to elucidate the impact of smoking on functional outcomes in cervical artificial disc replacement (ADR).

METHODS

Patients who underwent cervical ADR for myelopathy or radiculopathy from 2004 to 2015 with a minimum of 2 years of follow-up were included in the study. Patient function was assessed using Short Form-36 (SF-36), American Association of Orthopaedic Surgery (AAOS) cervical spine, and Japanese Orthopaedic Association (JOA) scoring systems preoperatively and at 2 years postoperatively. Incidence of further surgery on affected and adjacent segments was analyzed as well.

RESULTS

A total of 137 patients were included in the study, consisting of 117 nonsmokers and 20 smokers. There were 60 patients who presented with myelopathy and 77 with radiculopathy. The mean age of smokers was 42.6 years, compared with 46.4 years in the nonsmoker group (P < .01). Statistical improvement was noted in postoperative range of motion, as well as AAOS, SF-36, and JOA scores in both groups, with no difference between groups at 2 years of follow-up. A total of 84.2% of nonsmokers and 87.5% of smokers reported as surgery having met their expectations. A total of 5 of 117 nonsmokers (5.1%) and 4 of 20 smokers (20%) needed revision surgery (P = .018). Three of the 4 smokers who required surgery for adjacent or multisegment disease, whereas only 2 of the nonsmokers needed an operation for adjacent segment disease.

CONCLUSIONS

Our analysis indicates that there is no difference in functional outcome or patient satisfaction between smokers and nonsmokers. Smokers have a higher chance of revision surgery after an artificial disc replacement compared with nonsmokers at 2 years.

LEVEL OF EVIDENCE

3.

Impact of Tobacco Smoking on Outcomes After Posterior Decompression Surgery in Patients With Cervical Spondylotic Myelopathy: A Retrospective Multicenter Study

STUDY DESIGN

This was a case-control study.

OBJECTIVE

The objective of this study was to clarify the surgical outcomes after cervical posterior decompression in patients who smoked.

SUMMARY OF BACKGROUND DATA

Smoking is associated with poor outcomes in the field of spinal surgery. However, the impact of tobacco smoking on the outcomes after posterior decompression surgery has not been fully evaluated in patients with cervical spondylotic myelopathy.

MATERIALS AND METHODS

In this retrospective multicenter study, 587 patients with cervical spondylotic myelopathy were enrolled at 17 institutions in Japan. Patients underwent cervical laminoplasty or laminectomy and were followed up for at least 1 year after surgery. Outcome measures were: preoperative smoking status, perioperative complications, the Japanese Orthopedic Association scale, and the Visual Analog Scale for neck pain. After adjusting for age and sex by exact matching, smoking and nonsmoking groups were compared using an unpaired t test for continuous variables or a χ test for categorical variables.

RESULTS

There were 182 (31%) current smokers and 405 (69%) nonsmokers including previous smokers. After matching, 158 patients were extracted from each group. Demographic data and surgical information were almost the same between the groups. Regarding postoperative complications, there was no significant difference in the rate of surgical site infection, cerebrospinal fluid leakage, hematoma, segmental motor paralysis, or neurological deficit. However, smokers showed a significantly higher risk for delirium (3.8% vs. 0.0%, P=0.039). Smokers and nonsmokers showed comparable changes in functional recovery according to Japanese Orthopedic Association scores (3.2±2.1 vs. 3.0±2.1, P=0.425) and in neck pain reduction using the Visual Analog Scale (-1.7±3.1 vs. -1.4±2.8, P=0.417) at the final follow-up.

CONCLUSIONS

Smokers exhibited functional restoration and neck pain reduction after cervical posterior decompression. Attention is required, however, for the postoperative complication of delirium, which could be caused by the acute cessation of tobacco smoking after admission.

LEVEL OF EVIDENCE

Level III.

Smoking has a dose-dependent effect on the incidence of preoperative opioid consumption in female geriatric patients with spine disease

Tobacco use and narcotic medication have been associated with worse functional outcomes after surgery. Our goal was to investigate potential associations between smoking and preoperative opioid consumption in a geriatric population undergoing spine surgery, and their impact on postoperative outcomes. The records of 536 consecutive patients aged more than 65 years who underwent elective spinal surgery between November 2014 and August 2017 at a single institution were reviewed. Primary outcomes included rates of preoperative opioid consumption and postoperative hospital length of stay and complications. Males were more likely to be smokers than females (p < 0.001), whereas females were more likely to take opioid analgesics preoperatively (p = 0.022). Women with a history of smoking were more likely to have increased preoperative opioid consumption compared to those with no history of smoking (63.64% vs. 42.04%; p < 0.001). Such a relationship was not found in men. Subgroups analysis of female patients with a history of tobacco use comparing current and former smoker status showed that both groups exhibited increased preoperative opioid consumption compared to patients who never smoked (88.89% vs 42.04%; p < 0.001 for current users; 59.42% vs 42.04% for former users; p = 0.008). There was also a dose-depended relationship between smoking and increased preoperative opioid consumption. Geriatric female spine patients with a history of smoking have a higher incidence of preoperative opioid consumption. Opioid intake appears to increase with the number of pack-years, both in patients with a history of smoking and in those who currently smoke.

Development and Validation of Cervical Prediction Models for Patient-Reported Outcomes at 1 Year After Cervical Spine Surgery for Radiculopathy and Myelopathy

STUDY DESIGN

Retrospective analysis of prospectively collected registry data.

OBJECTIVE

To develop and validate prediction models for 12-month patient-reported outcomes of disability, pain, and myelopathy in patients undergoing elective cervical spine surgery.

SUMMARY OF BACKGROUND DATA

Predictive models have the potential to be utilized preoperatively to set expectations, adjust modifiable characteristics, and provide a patient-centered model of care.

METHODS

This study was conducted using data from the cervical module of the Quality Outcomes Database. The outcomes of interest were disability (Neck Disability Index:), pain (Numeric Rating Scale), and modified Japanese Orthopaedic Association score for myelopathy. Multivariable proportional odds ordinal regression models were developed for patients with cervical radiculopathy and myelopathy. Patient demographic, clinical, and surgical covariates as well as baseline patient-reported outcomes scores were included in all models. The models were internally validated using bootstrap resampling to estimate the likely performance on a new sample of patients.

RESULTS

Four thousand nine hundred eighty-eight patients underwent surgery for radiculopathy and 2641 patients for myelopathy. The most important predictor of poor postoperative outcomes at 12-months was the baseline Neck Disability Index score for patients with radiculopathy and modified Japanese Orthopaedic Association score for patients with myelopathy. In addition, symptom duration, workers' compensation, age, employment, and ambulatory and smoking status had a statistically significant impact on all outcomes (P < 0.001). Clinical and surgical variables contributed very little to predictive models, with posterior approach being associated with higher odds of having worse 12-month outcome scores in both the radiculopathy and myelopathy cohorts (P < 0.001). The full models overall discriminative performance ranged from 0.654 to 0.725.

CONCLUSIONS

These predictive models provide individualized risk-adjusted estimates of 12-month disability, pain, and myelopathy outcomes for patients undergoing spine surgery for degenerative cervical disease. Predictive models have the potential to be used as a shared decision-making tool for evidence-based preoperative counselling.

LEVEL OF EVIDENCE

2.

Role of oxidative metabolism in osseointegration during spinal fusion

Spinal fusion is a commonly performed orthopedic surgery. Autologous bone graft obtained from the iliac crest is frequently employed to perform spinal fusion. Osteogenic bone marrow stromal (a.k.a. mesenchymal stem) cells (BMSCs) are believed to be responsible for new bone formation and development of the bridging bone during spinal fusion, as these cells are located in both the graft and at the site of fusion. Our previous work revealed the importance of mitochondrial oxidative metabolism in osteogenic differentiation of BMSCs. Our objective here was to determine the impact of BMSC oxidative metabolism on osseointegration of the graft during spinal fusion. The first part of the study was focused on correlating oxidative metabolism in bone graft BMSCs to radiographic outcomes of spinal fusion in human patients. The second part of the study was focused on mechanistically proving the role of BMSC oxidative metabolism in osseointegration during spinal fusion using a genetic mouse model. Patients’ iliac crest-derived graft BMSCs were identified by surface markers. Mitochondrial oxidative function was detected in BMSCs with the potentiometric probe, CMXRos. Spinal fusion radiographic outcomes, determined by the Lenke grade, were correlated to CMXRos signal in BMSCs. A genetic model of high oxidative metabolism, cyclophilin D knockout (CypD KO), was used to perform spinal fusion in mice. Graft osseointegration in mice was assessed with micro-computed tomography. Our study revealed that higher CMXRos signal in patients’ BMSCs correlated with a higher Lenke grade. Mice with higher oxidative metabolism (CypD KO) had greater mineralization of the spinal fusion bridge, as compared to the control mice. We therefore conclude that higher oxidative metabolism in BMSCs correlates with better spinal fusion outcomes in both human patients and in a mouse model. Altogether, our study suggests that promoting oxidative metabolism in osteogenic cells could improve spinal fusion outcomes for patients.

Effects of smoking on pedicle screw-based dynamic stabilization: radiological and clinical evaluations of screw loosening in 306 patients

OBJECTIVE

Cigarette smoking has been known to increase the risk of pseudarthrosis in spinal fusion. However, there is a paucity of data on the effects of smoking in dynamic stabilization following lumbar spine surgery. This study aimed to investigate the clinical outcomes and the incidence of screw loosening among patients who smoked.

METHODS

Consecutive patients who had lumbar spondylosis, recurrent disc herniations, or low-grade spondylolisthesis that was treated with 1- or 2-level surgical decompression and pedicle screw-based Dynesys dynamic stabilization (DDS) were retrospectively reviewed. Patients who did not complete the minimum 2 years of radiological and clinical evaluations were excluded. All screw loosening was determined by both radiographs and CT scans. Patient-reported outcomes, including visual analog scale (VAS) scores of back and leg pain, Japanese Orthopaedic Association (JOA) scores, and Oswestry Disability Index (ODI), were analyzed. Patients were grouped by smoking versus nonsmoking, and loosening versus intact screws, respectively. All radiological and clinical outcomes were compared between the groups.

RESULTS

A total of 306 patients (140 women), with a mean age of 60.2 ± 12.5 years, were analyzed during an average follow-up of 44 months. There were 34 smokers (9 women) and 272 nonsmokers (131 women, 48.2% more than the 26.5% of smokers, p = 0.017). Postoperatively, all the clinical outcomes improved (e.g., VAS back and leg pain, JOA scores, and ODI, all p < 0.001). The overall rate of screw loosening was 23.2% (71 patients), and patients who had loosened screws were older (61.7 ± 9.6 years vs 59.8 ± 13.2 years, p = 0.003) and had higher rates of diabetes mellitus (33.8% vs 21.7%, p = 0.038) than those who had intact DDS screws. Although the patients who smoked had similar clinical improvement (even better VAS scores in their legs, p = 0.038) and a nonsignificantly lower rate of screw loosening (17.7% and 23.9%, p = 0.416), the chances of secondary surgery for adjacent segment disease (ASD) were higher than for the nonsmokers (11.8% vs 1.5%, p < 0.001).

CONCLUSIONS

Smoking had no adverse effects on the improvements of clinical outcomes in the pedicle screw-based DDS surgery. For smokers, the rate of screw loosening trended lower (without significance), but the chances of secondary surgery for ASD were higher than for the nonsmoking patients. However, the optimal surgical strategy to stabilize the lumbar spine of smoking patients requires future investigation.

The Utility of Cervical Spine Bracing As a Postoperative Adjunct to Multilevel Anterior Cervical Spine Surgery

Background

Use of cervical bracing/collar subsequent to anterior cervical spine discectomy and fusion (ACDF) is variable. Outcomes data regarding bracing after ACDF are limited. Here, we study the impact of bracing on short-term outcomes related to safety, quality of care, and direct costs in multilevel ACDF.

Methods

Retrospective cohort analyses of all consecutive patients undergoing multilevel ACDF with or without bracing from 2013 to 2017 was undertaken (n = 616). Patient demographics and comorbidities were analyzed. Tests of independence and logistic regressions were used to assess differences in length of stay (LOS), discharge disposition (home, assisted rehabilitation facility [ARF], or skilled nursing facility [SNF]), quality-adjusted life year (QALY), direct cost, readmission within 30 days, and emergency room (ER) visits within 30 days.

Results

Amongst the study population, 553 were braced and 63 were not braced. There was no difference in comorbidities (P > .05) such as obesity, smoking, chronic obstructive pulmonary disease, hypertension, coronary artery disease, congestive heart failure, and problem list number. A significant difference in American Society of Anesthesiologists (ASA) score was found, with more ASA 2 patients in the braced cohort and more ASA 3 patients in the unbraced cohort (P = .007). LOS was extended for the unbraced group (median 156.9 ± 211.4 versus 86.67 ± 130.6 h, P = .003), and ER visits within 30 days were 0.21 times less likely in the braced group (P = .006). There was no difference in readmission (P = .181), QALY gain (P = .968), and direct costs (P = .689).

Conclusion

Bracing following multilevel cervical fixation does not alter short-term postoperative course or reduce the risk for early adverse outcomes in a significant manner.

Perioperative Implications of Vaping

Over the past 10 - 15 years, there has been a significant increase in the use of electronic cigarettes. These devices are generally used to deliver nicotine through inhalation by aerosolization. While the long-term risk of lung cancer is yet to be known, the chemicals and impurities in the solutions may have other acute and chronic effects on the respiratory system including respiratory failure from adult respiratory distress syndrome. Recent concerns have been raised regarding the potential for significant acute and chronic health care risks of these devices including pneumonitis, airway reactivity and respiratory failure. Given that many of the acute effects are related to the respiratory system, anesthetic care may be required during diagnostic procedures including bronchoscopy to investigate the etiology of acute respiratory symptomatology. We present an adolescent who presented to the operating room for bronchoscopy and bronchoalveolar lavage to investigate the etiology of respiratory involvement following an episode of vaping. The healthcare and end-organ effects of nicotine, tobacco smoke and vaping are discussed, and potential anesthetic implications are presented.

Miniplate-Augmented Interlaminar Fusion in C1-C2 Screwing

OBJECTIVE

The interlaminar fusion combination involving C1-C2 screwing fixation is one of the most effective techniques for atlantoaxial dislocation or subluxation, and the bone graft is usually stabilized by wiring constructs. However, some adverse events were reported during the insertion of sublaminar wiring, such as accidentally damaging the spinal cord or dura. Thus we used the miniplate to stabilize the harvest bone graft on the C1-C2 laminar, which led to a shorter operation time and prevented spinal canal violation. This study investigated the safety and efficacy of the novel surgical technique, namely miniplate-augmented interlaminar fusion.

METHODS

We retrospectively reviewed 43 patients who underwent posterior atlantoaxial fusion with the miniplate-augmented iliac crest autograft at our institute. Complications related to surgery were recorded and calculated. After operation, patients were followed up through routine radiography to examine whether the fusion of the atlantoaxial segment was achieved. Success of fusion was defined as follows: 1) the presence of bone bridging between the bone graft and both the atlas and axis; and 2) the absence of movement of the atlantoaxial spinous process on flexion-extension radiography, which meant that the variation of length measured in 2 views, respectively, was <1 mm. The first time when radiography showed successful fusion after surgery was termed as fusion time and was recorded individually. In addition, overall fusion rates and mean fusion times were analyzed.

RESULTS

Of 43 patients, long-term follow-up data were available for 31 patients, whereas the remaining 12 patients had dropped out (mean follow-up duration, 24.91 months; range, 6-72 months). Among 31 patients, 22 (70.96%) were women and 9 (29.03%) were men. The mean age was 63.33 years. Regarding the etiology, atlantoaxial dislocations or subluxations were caused due to degeneration, rheumatoid arthritis, odontoid fracture, trauma, and os odontoideum in 14 (45%), 3 (10%), 5 (16%), 8 (26%), and 1 (3%) patient(s), respectively. Successful fusion was achieved in 30 (96.77%) patients, with a mean fusion time of 6.23 months, whereas only 1 (3.23%) patient did not meet the fusion criteria. No complications related to the miniplate occurred. We noted vertebral artery rupture not requiring blood transfusion in 1 patient, aspiration pneumonia in 1 patient, urinary tract infection in 1 patient, anemia requiring transfusion in 1 patient, and leg dysesthesia in 1 patient. No neurologic deficit was found.

CONCLUSIONS

Miniplate-augmented interlaminar fusion with C1-C2 screwing resulted in excellent fusion rates with a considerably low probability of complications. Hence this novel technique for bone graft fixation with atlantoaxial screwing has a good efficacy and safety and can serve as an alternative for bone graft fixation during C1-C2 fusion.

Complications of anterior cervical spine surgery: a systematic review of the literature

The anterior approach to the cervical spine is commonly utilized for a variety of degenerative, traumatic, neoplastic, and infectious indications. While many potential complications overlap with those of the posterior approach, the distinct anatomy of the anterior neck also presents a unique set of hazards. We performed a systematic review of the literature to assess the etiology, presentation, natural history, and management of these complications. Following the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), a PubMed search was conducted to evaluate clinical studies and case reports of patients who suffered a complication of anterior cervical spine surgery. The search specifically included articles concerning adult human subjects, written in the English language, and published from 1989 to 2019. The PubMed search yielded 240 articles meeting our criteria. The overall rates of complications were as follows: dysphagia 5.3%, esophageal perforation 0.2%, recurrent laryngeal nerve palsy 1.3%, infection 1.2%, adjacent segment disease 8.1%, pseudarthrosis 2.0%, graft or hardware failure 2.1%, cerebrospinal fluid leak 0.5%, hematoma 1.0%, Horner syndrome 0.4%, C5 palsy 3.0%, vertebral artery injury 0.4%, and new or worsening neurological deficit 0.5%. Morbidity rates in anterior cervical spine surgery are low. Nevertheless, the unique anatomy of the anterior neck presents a wide variety of potential complications involving vascular, aerodigestive, neural, and osseous structures.

Infection prevention in cervical spine surgery

Surgical site infections (SSI) following cervical spine surgery can lead to significant patient morbidity and costs. Prevention of SSIs is multifactorial and can be divided in to preoperative patient optimization and intraoperative surgical factors. We performed a literature review to identify methods that can be used to prevent SSI development specifically in the cervical spine. We also present specific surgical pearls and techniques that have the potential to significantly decrease rates of cervical SSIs.

The Effect of Tobacco Use on Postoperative Pain Following Anterior Cervical Discectomy and Fusion

STUDY DESIGN

This was a retrospective cohort study.

OBJECTIVE

To identify the differences in inpatient pain scores, narcotic consumption, and patient-reported outcomes (PROs) between tobacco users and nonusers following an anterior cervical discectomy and fusion (ACDF).

SUMMARY OF BACKGROUND DATA

Previous studies have investigated tobacco use as a risk factor for negative postsurgical outcomes following spine surgery; however, few studies have analyzed the effects of tobacco on pain following ACDF.

METHODS

Patients undergoing primary, 1-level, or 2-level ACDF were retrospectively reviewed and stratified by tobacco use at the time of surgery. Inpatient pain scores and narcotic consumption were collected. Neck Disability Index and Visual Analogue Scale (VAS) neck and arm pain scores were collected preoperatively and at 6-week, 3-month, and 6-month follow-up visits. Differences in demographics and perioperative characteristics were assessed using χ analysis and multivariate linear regression. An association between immediate postoperative pain, narcotics consumption, and long-term PROs was tested for using multivariate linear regression.

RESULTS

A total of 192 patients were included and stratified by tobacco use: tobacco (n=25) and nontobacco (n=167). There were no significant differences in demographic and perioperative characteristics. No statistical differences were observed in inpatient VAS pain scores and narcotic consumption on postoperative day 0 and postoperative day 1. Preoperative VAS neck pain and arm pain was greater in tobacco users, however, improvements in neck and arm pain were similar in the postoperative period through 6-month follow-up. In addition, no statistical differences in Neck Disability Index were observed preoperatively or at any postoperative time points.

CONCLUSIONS

Our study suggests that tobacco use does not influence inpatient pain scores, narcotic consumption, and improvements in PROs following ACDF. As such, tobacco users and nonusers should receive similar postoperative pain management protocols following surgery.

LEVEL OF EVIDENCE

Level III.

Factors Influencing Interbody Cage Subsidence Following Anterior Cervical Discectomy and Fusion

STUDY DESIGN

This is a prospective study.

OBJECTIVE

The purpose of this study was to analyze the factors influencing subsidence following anterior cervical discectomy and fusion (ACDF) using a stand-alone cage.

SUMMARY OF BACKGROUND DATA

The relationship between cage subsidence and cage height and material has been reported in previous studies.

METHODS

Clinical and radiologic data from 78 patients, 105 levels, undergoing single-level and 2-level ACDF without plates from 2007 to 2015 were collected prospectively. Patients were followed for at least 12 months after surgery. Radiographs were obtained preoperatively, at 1 week, and at 1, 3, 6, and 12 months postoperatively to determine the presence of fusion and cage subsidence.

RESULTS

There was a correlation in cage height and subsidence (Spearman P<0.05). Cage subsidence was significantly shorter in the polyetheretherketone cages than in titanium cages (P<0.05). However, when cage height was <5 mm, the difference between the 2 groups was not significant. Large subsidence (>3 mm) was observed in 17 patients, 20 levels, many of whom exhibited sinking in the first month after surgery.

CONCLUSIONS

The greater the cage height, the greater the risk of cage subsidence in ACDF. Polyetheretherketone cages are superior to titanium cages for the maintenance of intervertebral height in cases where cage height is >5.5 mm.

LEVEL OF EVIDENCE

Level 3.

Urinary N-Telopeptide Can Predict Pseudarthrosis After Anterior Cervical Decompression and Fusion: A Prospective Study

STUDY DESIGN

Prospective cohort study.

OBJECTIVE

To examine preoperative urinary cross-linked n-telopeptide (uNTx) and assess for association with fusion rates in patients undergoing single and multi-level anterior cervical decompression and fusion (ACDF).

SUMMARY OF BACKGROUND DATA

Although high rates of fusion have been reported for ACDF, the risk of pseudarthrosis remains substantial. An established marker of bone turnover, uNTx may prove useful as a predictor of fusion.

METHODS

Patients undergoing primary ACDF with allograft/plating technique from 2015 to 2017 by a single surgeon were consecutively enrolled and preoperative uNTx was collected. Patients undergoing revision, with creatinine >1.2, and with improperly-collected uNTx were excluded. Demographics, laboratory values, and fusion status were assessed at 6 months, 1 year, and 2 years postoperatively.

RESULTS

Of the 97 patients enrolled, 69 met inclusion criteria. Of included cases, 41%, 33%, 18%, and 8% underwent 1-, 2-, 3-, and 4-level ACDF, respectively. Overall, fusion rates were 37.3%, 70.9%, and 95.3% at 6 months, 1 year, and 2 years, respectively. uNTx was higher in the fusion group (31.1 vs. 22.2, P = 0.001) at 6 months and 1 year (30.0 vs. 21.0, P = 0.006), with no difference at 2 years. No differences were identified in the proportion of smokers, immunomodulatory agents, corpectomies, or fusion levels between groups. Multivariate regression analysis demonstrated that uNTx is an independent predictor of fusion (odds ratio, OR, 1.124, P = 0.003). Both groups experienced improvements in NDI and VAS neck pain at 6 months with no significant differences noted between groups. Of 16 patients with pseudarthrosis at 1 year, 2 underwent posterior cervical fusion for symptoms.

CONCLUSION

Preoperative uNTx was greater in patients with successful ACDF fusion compared with patients with pseudarthrosis at 6 months and 1 year. A negative correlation was found between preoperative uNTx and motion on dynamic imaging. These results suggest that uNTx could serve to identify patients at risk for pseudarthrosis after ACDF.

LEVEL OF EVIDENCE

3.

The Utility of Cervical Spine Bracing as a Postoperative Adjunct to Single-level Anterior Cervical Spine Surgery

Background Context:

Use of cervical bracing/collar subsequent to anterior cervical spine discectomy and fusion (ACDF) is variable. Outcomes data regarding bracing after ACDF are limited.

Purpose:

The purpose of the study is to study the impact of bracing on short-term outcomes related to safety, quality of care, and direct costs in single-level ACDF.

Study Design/Setting:

This retrospective cohort analysis of all consecutive patients (n = 578) undergoing single-level ACDF with or without bracing from 2013 to 2017 was undertaken.

Methods:

Patient demographics and comorbidities were analyzed. Tests of independence (Chi-square, Fisher's exact, and Cochran–Mantel–Haenszel test), Mann–Whitney–Wilcoxon tests, and logistic regressions were used to assess differences in length of stay (LOS), discharge disposition (home, assisted rehabilitation facility-assisted rehabilitation facility, or skilled nursing facility), quality-adjusted life year (QALY), surgical site infection (SSI), direct cost, readmission within 30 days, and emergency room (ER) visits within 30 days.

Results:

Among the study population, 511 were braced and 67 were not braced. There was no difference in graft type (P = 1.00) or comorbidities (P = 0.06–0.73) such as obesity (P = 0.504), smoking (0.103), chronic obstructive pulmonary disease hypertension (P = 0.543), coronary artery disease (P = 0.442), congestive heart failure (P = 0.207), and problem list number (P = 0.661). LOS was extended for the unbraced group (median 34.00 + 112.15 vs. 77.00 + 209.31 h, P < 0.001). There was no difference in readmission (P = 1.000), ER visits (P = 1.000), SSI (P = 1.000), QALY gain (P = 0.437), and direct costs (P = 0.732).

Conclusions:

Bracing following single-level cervical fixation does not alter short-term postoperative course or reduce the risk for early adverse outcomes in a significant manner. The absence of bracing is associated with increased LOS, but cost analyses show no difference in direct costs between the two treatment approaches. Further evaluation of long-term outcomes and fusion rates will be necessary before definitive recommendations regarding bracing utility following single-level ACDF.

Effects of smoking on cervical disc arthroplasty

Objective

Cigarette smoking can adversely affect bone fusion in patients who undergo anterior cervical discectomy and fusion. However, there is a paucity of data on smoking among patients who have undergone cervical disc arthroplasty (CDA). The present study aimed to compare the clinical and radiological outcomes of smokers to those of nonsmokers following CDA.

Methods

The authors retrospectively reviewed the records of consecutive patients who had undergone 1- or 2-level CDA for cervical disc herniation or spondylosis and had a minimum 2-year follow-up. All patients were grouped into a smoking group, which consisted of those who had consumed cigarettes within 6 months prior to the CDA surgery, or a nonsmoking group, which consisted of those who had not consumed cigarettes at all or within 6 months of the CDA. Clinical outcomes were evaluated according to the visual analog scale for neck and arm pain, Neck Disability Index, Japanese Orthopaedic Association Scale, and Nurick Scale at each time point of evaluation. Radiological outcomes were assessed using radiographs and CT for multiple parameters, including segmental range of motion (ROM), neutral lordotic curve, and presence of heterotopic ossification (HO).

Results

A total of 109 patients completed at least 2 years of follow-up and were analyzed (mean follow-up 42.3 months). There were 89 patients in the nonsmoking group and 20 in the smoking group. The latter group was younger and predominantly male (both p < 0.05) compared to the nonsmoking group. The two groups had similar improvements in all clinical outcomes after CDA compared to preoperatively. Radiological evaluations were also very similar between the two groups, except for two factors. The smoking group had well-preserved segmental ROM after CDA at an average of 8.1° (both pre- and postoperation). However, while the nonsmoking group remained mobile, segmental ROM decreased significantly (8.2° to 6.9°, p < 0.05) after CDA. There was a trend toward more HO development in the nonsmoking group than in the smoking group, but the difference was without significance (59.6% vs 50.0%, p = 0.43).

Conclusions

During an average 3.5 years of follow-up after 1- and 2-level CDA, cigarette smokers and nonsmokers had similar improvements in clinical outcomes. Moreover, segmental mobility was slightly better preserved in smokers. Since smoking status did not negatively impact outcomes, CDA may be a reasonable option for selected patients who have smoked.

Abbreviations

ACDF = anterior cervical discectomy and fusion; ASD = adjacent-segment degeneration; CDA = cervical disc arthroplasty; FDA = Food and Drug Administration; HO = heterotopic ossification; JOA = Japanese Orthopaedic Association; NDI = Neck Disability Index; ROM = range of motion; VAS = visual analog scale.

Clinical Outcomes After Four-Level Anterior Cervical Discectomy and Fusion

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

Anterior cervical discectomy and fusion (ACDF) demonstrates reliable improvement in neurologic symptoms associated with anterior compression of the cervical spine. There is a paucity of data on outcomes following 4-level ACDFs. The purpose of this study was to evaluate clinical outcomes for patients undergoing 4-level ACDF.

METHODS

All 4-level ACDFs with at least 1-year clinical follow-up were identified. Clinical outcomes, including fusion rates, neurologic outcomes, and reoperation rates were determined.

RESULTS

Retrospective review of our institutional database revealed 25 patients who underwent 4-level ACDF with at least 1-year clinical follow-up. Average age was 57.5 years (range 38.2-75.0 years); 14 (56%) were male, and average body mass index was 30.2 kg/m² (range 19.9-43.4 kg/m²). Two (8%) required secondary cervical surgery at an average of 94.5 days postoperatively while the remaining 23 did not with an average follow-up of 19 months. Of 23 patients not requiring revision surgery, 16 (69%) patients fused by definition of less than 1 mm of spinous process motion per fused level in flexion and extension. Fifteen (65%) had at least one muscle group with one grade of weakness preoperatively. Nineteen of these patients (83%) had improved to full strength while no patients lost muscle strength.

CONCLUSIONS

Review of our institution's experience demonstrated a low rate of revision cervical surgery for any reason of 8% at mean 19 months follow-up, and neurological examinations consistently improved, despite a high rate of radiographic nonunion (31%).

Diagnosing Pseudoarthrosis After Anterior Cervical Discectomy and Fusion

Radiographic confirmation of fusion after anterior cervical discectomy and fusion (ACDF) surgery is a critical aspect of determining surgical success. However, there is a lack of established diagnostic radiographic parameters for pseudoarthrosis. The purpose of this study is to summarize the findings of previous studies, review the advantages and disadvantages of frequently employed diagnostic criteria, and present our recommended protocol of fusion assessment. This study identified randomized controlled trials, case-control studies, and prospective and retrospective cohort studies reporting on spinal fusion and how successful fusion after ACDF. Among the 39 articles reviewed, bridging bone across the operated levels on static radiographs was the most commonly used criteria to confirm fusion (31 of 39, 79%). Dynamic flexion-extension radiographs were used to assess for interspinous movement (ISM) (22 of 39, 56.4%) and change in Cobb angle (12 of 39, 30.8%). Computed tomography (CT) based findings (21 of 39, 53.8%) were employed in ambiguous cases with improved sensitivity and specificity. Reconstructed CT scans were used to assess for intragraft bridging bone and extragraft bridging bone (ExGBB). ExGBB were proved to have the highest diagnostic sensitivity and specificity for pseudoarthrosis detection when compared to all other radiographic criteria. The ISM <1 mm on dynamic flexion-extension radiographs had high diagnostic sensitivity and specificity as well. After our reviewing, we recommend using dynamic lateral flexion-extension cervical spine radiographs at 150% magnificationin which the interspinous motion <1 mm and superjacent interspinous motion ≥4 mm confirms fusion. In ambiguous cases, we recommend using reconstructed CT scans to evaluate for ExGBB.

Opioids delay healing of spinal fusion: a rabbit posterolateral lumbar fusion model

BACKGROUND CONTEXT

Opioid use is prevalent in the management of pre- and postoperative pain in patients undergoing spinal fusion. There is evidence that opioids downregulate osteoblasts in vitro, and a previous study found that morphine delays the maturation and remodeling of callus in a rat femur fracture model. However, the effect of opioids on healing of spinal fusion has not been investigated before. Isolating the effect of opioid exposure in humans would be limited by the numerous confounding factors that affect fusion healing. Therefore, we have used a well-established rabbit model to study the process of spinal fusion healing that closely mimics humans.

PURPOSE

The objective of this work was to study the effect of systemic opioids on the process of healing of spinal fusion in a rabbit posterolateral spinal fusion model.

STUDY DESIGN/SETTING

This is a preclinical animal study.

MATERIALS AND METHODS

Twenty-four adult New Zealand white rabbits were studied in two groups after approval from the Institutional Animal Care and Use Committee (IACUC). The opioid group (n=12) received 4 weeks' preoperative and 6 weeks' postoperative transdermal fentanyl. Serum fentanyl levels were measured just before surgery and 4 weeks postoperatively to ensure adequate levels. The control group (n=12) received only perioperative pain control as necessary. All animals underwent a bilateral L5-L6 posterolateral spinal fusion using iliac crest autograft. Animals were euthanized at the 6-week postoperative time point, and assessment of fusion was done by manual palpation, plain radiographs, microcomputed tomography (microCT), and histology.

RESULTS

Twelve animals in the control group and 11 animals in the opioid group were available for analysis at the end of 6 weeks. The fusion scores on manual palpation, radiographs, and microCT were not statistically different. Three-dimensional microCT morphometry found that the fusion mass in the opioid group had a lower bone volume (p=.09), a lower trabecular number (p=.02), and a higher trabecular separation (p=.02) compared with the control group. Histologic analysis found areas of incorporation of autograft and unincorporated graft fragments in both groups. In the control group, there was remodeling of de novo woven bone to lamellar organization with incorporation of osteocytes, formation of mature marrow, and relative paucity of hypertrophied osteoblasts lining new bone. Sections from the opioid group showed formation of de novo woven bone, and hypertrophied osteoblasts were seen lining the new bone. There were no sections showing lamellar organization and development of mature marrow elements in the opioid group. Less dense trabeculae on microCT correlated with histologic findings of relatively immature fusion mass in the opioid group.

CONCLUSIONS

Systemic opioids led to an inferior quality fusion mass with delay in maturation and remodeling at 6 weeks in this rabbit spinal fusion model. These preliminary results lay the foundation for further research to investigate underlying cellular mechanisms, the temporal fusion process, and the dose-duration relationship of opioids responsible for our findings.