Variability in Standard Outcomes of Posterior Lumbar Fusion Determined by National Databases

Myocardial Infarction After Lumbar Surgery: A Critical Meta-Analysis of Cohort versus Database Studies for a Rare Complication

BACKGROUND

One potentially fatal complication of spine surgery is myocardial infarction (MI). There is still uncertainty of the true incidence of MI within subsets of spine surgeries. The aim of this study was to survey the contemporary spine literature and ascertain the true incidence of MI after lumbar spine surgery, as well as to provide commentary on the inherent assumptions made when interpreting cohort versus database studies on this topic.

METHODS

A systematic search of 4 electronic databases from inception to November 2020 was conducted following PRISMA guidelines. Articles were screened against prespecified criteria. MI incidence was then estimated by random-effects meta-analyses of proportions based on cohort versus database studies.

RESULTS

A total of 34 cohort studies and 32 database studies describing 767,326 lumbar procedures satisfied all criteria for selection. There were 12,170 (2%) cases from cohort studies and 755,156 (98%) cases from database studies. Cohort studies reported a significantly older patient cohort (P < 0.01) and longer follow-up period than did database studies (P < 0.03). Using cohort studies only, the incidence of MI was 0.44% (P heterogeneity < 0.01), whereas using database studies only, the incidence of MI was 0.41% (P heterogeneity < 0.01). These 2 incidences were statistically different (P interaction = 0.01). Bias analysis indicated that cohort studies were more vulnerable to small-study biases than were database studies.

CONCLUSIONS

Although infrequent, the incidence of MI after lumbar spine surgery is unequivocally nonzero. Furthermore, the literature on this topic remains skewed based on study type, and translation of academic findings into practice should be wary of this.

The incidence of acute myocardial infarction after elective spinal fusions or joint replacement surgery in the United States: a large-scale retrospective observational cohort study in 322,585 patients : Post-surgical myocardial infarction data

Background

Acute myocardial infarction (AMI) is an uncommon but fatal complication among patients undergoing elective spinal fusion surgery (SF), total hip arthroplasty (THA), and total knee arthroplasty (TKA). Our objective was to estimate the incidence of AMI among adults undergoing elective SF, THA, and TKA in different post-operative risk windows and characterize high-risk sub-populations in the United States.

Methods

A retrospective cohort study was conducted using data from a longitudinal electronic healthcare record (EHR) database from January 1, 2007 to June 30, 2018. ICD codes were used to identify SF, THA, TKA, AMI, and selected clinical characteristics. Incidence proportions (IPs) and 95% confidence intervals were estimated in the following risk windows: index hospitalization, ≤ 30, ≤ 90, ≤ 180, and ≤ 365 days post-operation.

Results

A total of 67,533 SF patients, 87,572 THA patients, and 167,480 TKA patients were eligible for the study. The IP of AMI after SF, THA, and TKA ranged from 0.36, 0.28, and 0.25% during index hospitalization to 1.05, 0.93, and 0.85% ≤ 365 days post-operation, respectively. The IP of AMI was higher among patients who were older, male, with longer hospital stays, had a history of AMI, and had a history of diabetes.

Conclusion

The IP of post-operative AMI was generally highest among the SF cohort compared to the THA and TKA cohorts. Additionally, potential high-risk populations were identified. Future studies in this area are warranted to confirm these findings via improved confounder control and to identify effect measure modifiers.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13037-021-00305-6.

The incidence of stroke among selected patients undergoing elective posterior lumbar fusion: a retrospective cohort study

BACKGROUND

Although stroke is a rare complication among spinal surgery patients, the recognition of this adverse event is critical given the aging population undergoing surgical procedures. The objective of this study was to estimate the incidence of stroke among selected adults undergoing elective posterior lumbar fusion (PLF) during various post-operative risk windows and among different subgroups.

METHODS

A retrospective cohort study using a longitudinal electronic healthcare record (EHR) database was conducted from January 1, 2007 to June 30, 2018. Elective PLF, stroke, and select clinical characteristics were defined based on International Classification of Disease codes. Patients aged 18 to 85 years with ≥183 days of enrollment in the database prior to undergoing elective PLF were followed from the index date until the occurrence of stroke, death, loss to follow-up, or end of study period, whichever occurred first. The incidence of stroke was estimated in the following risk windows: index hospitalization, ≤ 30 days, ≤ 90 days, ≤ 180 days, and ≤ 365 days post-operation.

RESULTS

A total of 43,063 patients were eligible for the study. The incidence of stroke following elective PLF was 0.29% (95% confidence interval [CI]: 0.25, 0.35%) during index hospitalization, 0.44% (95% CI: 0.38, 0.50%) ≤ 30 days, 0.59% (95% CI: 0.52, 0.67%) ≤ 90 days, 0.76% (95% CI: 0.68, 0.85%) ≤ 180 days, and 1.12% (95% CI: 1.03, 1.23%) ≤ 365 days post-operation. Stratified analyses revealed that older patients had a higher incidence of stroke. Additionally, black patients had higher stroke incidences. Post-operative stroke incidence was higher among patients with a history of type 2 diabetes than among patients without such history; similarly, stroke incidence was higher among patients with a history of stroke compared to patients without such history.

CONCLUSIONS

The incidence of stroke following elective PLF using an EHR database in this study is slightly higher than that reported in the literature. Our results suggest that stroke risk modification prior to PLF may be important for patients who are older, black, type 2 diabetic, and/or have a history of stroke.

Natural language processing for automated detection of incidental durotomy

BACKGROUND

Incidental durotomy is a common intraoperative complication during spine surgery with potential implications for postoperative recovery, patient-reported outcomes, length of stay, and costs. To our knowledge, there are no processes available for automated surveillance of incidental durotomy.

PURPOSE

The purpose of this study was to develop natural language processing (NLP) algorithms for automated detection of incidental durotomies in free-text operative notes of patients undergoing lumbar spine surgery.

PATIENT SAMPLE

Adult patients 18 years or older undergoing lumbar spine surgery between January 1, 2000 and June 31, 2018 at two academic and three community medical centers.

OUTCOME MEASURES

The primary outcome was defined as intraoperative durotomy recorded in free-text operative notes.

METHODS

An 80:20 stratified split was undertaken to create training and testing populations. An extreme gradient-boosting NLP algorithm was developed to detect incidental durotomy. Discrimination was assessed via area under receiver-operating curve (AUC-ROC), precision-recall curve, and Brier score. Performance of this algorithm was compared with current procedural terminology (CPT) and international classification of diseases (ICD) codes for durotomy.

RESULTS

Overall, 1,000 patients were included in the study and 93 (9.3%) had a recorded incidental durotomy in the free-text operative report. In the independent testing set (n=200) not used for model development, the NLP algorithm achieved AUC-ROC of 0.99 for detection of durotomy. In comparison, the CPT/ICD codes had AUC-ROC of 0.64. In the testing set, the NLP algorithm detected 16 of 18 patients with incidental durotomy (sensitivity 0.89) whereas the CPT and ICD codes detected 5 of 18 (sensitivity 0.28). At a threshold of 0.05, the NLP algorithm had specificity of 0.99, positive predictive value of 0.89, and negative predictive value of 0.99.

CONCLUSIONS

Internal validation of the NLP algorithm developed in this study indicates promising results for future NLP applications in spine surgery. Pending external validation, the NLP algorithm developed in this study may be used by entities including national spine registries or hospital quality and safety departments to automate tracking of incidental durotomies.

Risk Factors Associated With 90-Day Readmissions After Degenerative Lumbar Fusion: An Examination of the Michigan Spine Surgery Improvement Collaborative (MSSIC) Registry

BACKGROUND

Most studies have evaluated 30-d readmissions after lumbar fusion surgery. Evaluation of the 90-d period, however, allows a more comprehensive assessment of factors associated with readmission.

OBJECTIVE

To assess the reasons and risk factors for 90-d readmissions after lumbar fusion surgery.

METHODS

The Michigan Spine Surgery Improvement Collaborative (MSSIC) registry is a prospective, multicenter, and spine-specific database of patients surgically treated for degenerative disease. MSSIC data were retrospectively analyzed for causes of readmission, and independent risk factors impacting readmission were found by multivariate logistic regression.

RESULTS

Of 10 204 patients who underwent lumbar fusion, 915 (9.0%) were readmitted within 90 d, most commonly for pain (17%), surgical site infection (16%), and radicular symptoms (10%). Risk factors associated with increased likelihood of readmission were other race (odds ratio [OR] 1.81, confidence interval [CI] 1.22-2.69), coronary artery disease (OR 1.57, CI 1.25-1.96), ≥4 fused levels (OR 1.41, CI 1.06-1.88), diabetes (OR 1.34, CI 1.10-1.63), and surgery length (OR 1.09, CI 1.03-1.16). Factors associated with decreased risk were discharge to home (OR 0.63, CI 0.51-0.78), private insurance (OR 0.79, CI 0.65-0.97), ambulation same day of surgery (OR 0.81, CI 0.67-0.97), and spondylolisthesis diagnosis (OR 0.82, CI 0.68-0.97). Of those readmitted, 385 (42.1%) patients underwent another surgery.

CONCLUSION

Ninety-day readmission occurred in 9.0% of patients, mainly for pain, wound infection, and radicular symptoms. Increased focus on postoperative pain may decrease readmissions. Among factors impacting the likelihood of 90-d readmission, early postoperative ambulation may be most easily modifiable. Optimization of preexisting medical conditions could also potentially decrease readmission risk.

Thoracolumbar Fusion in Extreme Obesity: Complications and Patient-Reported Outcomes

Background

Extreme obesity (class III) is defined by the Centers for Disease Control as a body mass index (BMI) value ≥40. Recent studies suggest that obese patients have poor outcomes after thoracolumbar spinal fusions. The objective of this study was to analyze 30-day adverse events and patient-reported outcomes (PROs) for this population.

Patients and Methods

A retrospective chart review of spinal fusion surgeries performed at a single institution from 2006 to 2016 was executed. All patients had a preoperative BMI ≥40. Patient characteristics, including age, sex, BMI, American Society of Anesthesiologists (ASA) score, Charlson Comorbidity Index (CCI), and others, were collected. Thirty-day adverse events (complications, readmissions, reoperations, and mortality) and PROs (Oswestry Disability Index [ODI] and visual analog scale [VAS]) were recorded.

Results

Fifty-six patients were identified, including 30 men (54%). Mean age was 55.7 years (range, 31-74 years). Mean BMI was 44.2 (range, 40.0-54.7). Mean ASA was 2.7 (range, 2-3), and mean CCI was 1.1 (range, 0-6). Mean number of fused levels was 2.3 (range, 1-14). Mean length of stay was 4.4 ± 2.1 days. Mean number of complications was 0.7 ± 1.1, with 30.4% of patients having had at least 1 complication. The 30-day all-cause readmission rate was 5.4%, and 30-day reoperation rate was 3.6%. For 30 patients (54%) with 1-year PROs, mean preoperative ODI was 65.2 ± 11.1, and mean preoperative VAS was 6.6 ± 1.6. Mean ODI change was -19.9 ± 20.1 (P < .001), and mean VAS change was -2.6 ± 2.3 (P < .001). A total of 15 patients (50%) achieved the minimum clinically important difference in ODI (12.8), with a mean follow-up of 18.9 months.

Conclusions

Patients with extreme obesity who undergo thoracolumbar fusion have acceptable 30-day adverse events and potentially can achieve significant improvement in pain and disability.

Inaccuracies in ICD Coding for Obesity Would Be Expected to Bias Administrative Database Spine Studies Toward Overestimating the Impact of Obesity on Perioperative Adverse Outcomes

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

To determine if International Classification of Diseases (ICD) coding for obesity is biased toward certain subgroups and how potential bias may influence the outcomes of database research in spine.

SUMMARY OF BACKGROUND DATA

There has been increased use of national databases using administrative data in the spine surgery literature. Past research demonstrates that sensitivity of ICD codes for obesity is poor, but it is unknown if such inaccuracies are systematically biased and if they may bias studies utilizing such data.

METHODS

Patients who underwent elective posterior lumbar fusion, 2013 to 2016, at a large academic hospital were identified. All ICD codes assigned to the encounter were obtained. Body mass index (BMI) was calculated based on height and weight. The sensitivity of ICD coding for obesity was calculated. Sensitivity was compared for subgroups defined by demographic, comorbidity, intraoperative, and postoperative factors. The association of obesity (as defined by BMI≥30 and ICD coding) with 30-day postoperative adverse events was tested with multivariate regression.

RESULTS

The study included 796 patients. The overall sensitivity of ICD coding for obesity was 42.5%. The sensitivity of ICD coding for obesity was significantly higher in patients with greater BMI, diabetes, American Society of Anesthesiologists class≥III, increased length of stay, venous thromboembolism, any adverse event, and major adverse event. Multivariate analysis for determining outcomes of increased risk with obesity as defined by ICD coding included venous thromboembolism, major adverse events, and any adverse events. However, multivariate analysis for determining outcomes of increased risk with obesity defined by BMI did not yield any positive associations.

CONCLUSION

ICD codes for obesity are more commonly assigned to patients with other comorbidities or postoperative complications. Further, use of such nonrandomly assigned ICD codes for obesity has the potential to skew studies to suggest greater associated adverse events than calculated BMI would demonstrate.

LEVEL OF EVIDENCE

3.

Cost-Effectiveness Data Regarding Spinal Cord Stimulation for Low Back Pain

STUDY DESIGN

Review of published literature pertaining to spinal cord stimulation (SCS) cost data analysis.

OBJECTIVE

To acquire, organize, and succinctly summarize the available literature regarding the costs associated with, and the cost-effectiveness of, SCS.

SUMMARY OF BACKGROUND DATA

Chronic back and limb pain is a pervasive complaint in modern society, with estimated annual costs of medical care greater than $100 billion. The traditional standard medical management with or without intermittent surgical decompression/fusion has been plagued by high costs and inconsistent results, leading to poor patient satisfaction and functional outcome, and questions from policy makers regarding use of limited healthcare resources. Neuromodulation techniques, including SCS have recently become more common in the treatment of chronic back/leg pain, with clinical studies showing a high degree of efficacy in alleviating otherwise intractable pain. Given the relatively high upfront costs associated with the hardware and implantation, policy makers have, however, questioned their use in the framework of cost-containment and resource utilization. We reviewed the available literature summarizing cost data of SCS in chronic back and limb pain, as an understanding of these data will be vital to justify continued payment for this expensive, but often very effective, treatment modality.

METHODS

We performed a PubMed literature search utilizing the following terms: "spinal cord stimulation," "SCS," "financial," "cost," "cost-effectiveness," and "cost-utility." All studies published in English and containing complete or partial cost evaluations of SCS for chronic back and limb pain were included.

RESULTS

The search revealed 21 studies that evaluated cost data, with or without outcomes analysis and cost-utility analysis, for patients with chronic back and limb pain. The overwhelming majority of data presented shows that SCS is not only an effective treatment option for these patients, but also represents cost savings and efficient use of healthcare resources relative to current standards of care. Although not all studies performed cost-utility analyses, those that did tended to show SCS falling well within accepted thresholds of "willingness-to-pay" on the part of third-party payers. That being said, the articles included in this review were almost all small, retrospective, single-institution studies. In addition, many of them relied on modeling for their analyses, and published literature values for cost and/or outcomes data rather than prospectively collected patient data. Although the data presented in this review are encouraging, it should serve as a foundation for a thorough, prospective, cost-utility analysis of SCS in chronic back and limb pain so that the role of this important treatment modality may be cemented in the treatment paradigm for these patients without questions from third-party payers.

CONCLUSION

The large majority of data covering costs of SCS argue in favor of the cost-effectiveness of this treatment modality for chronic neuropathic pain, especially in comparison to reoperation and medical management. Although most of the higher-quality evidence is relatively short-term, clinical experience with the durability of treatment benefit of SCS in these patients is promising. Given the pushback regarding high upfront costs of implantation, longer-term, prospective, randomized studies evaluating this topic will be important to help maintain third-party payer reimbursements for SCS.

LEVEL OF EVIDENCE

5.