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The Spine Blog

Friday, June 21, 2019

Care pathways have been embraced as a way to standardize treatment for a wide variety of conditions in order to avoid unnecessary variation and encourage compliance with evidence-based guidelines. They have been popular for common surgical procedures such as total joint arthroplasty and have been shown to reduce length of stay (LOS) and decrease costs. Less has been published about their role in spine surgery, likely due to the heterogeneity and complexity of spine procedures as compared to total joint replacement. However, given the greater duration of surgery and physiological insult associated with major spine surgery, the potential benefits of care standardization could be even greater in the complex spine surgery population. In order to assess their results associated with a care pathway for major spine surgery, Dr. Dagal and colleagues from Harborview Medical Center in Seattle compared outcomes before and after implementation of their care pathway for major spine surgery. The pathway included preoperative, intraoperative, and postoperative phases and focused on education, nutrition, minimizing physiological disruption, pain control, and early postoperative mobilization. Their main outcome measures were hospital and ICU LOS. Postoperative complications, 30-day readmission, and cost were secondary outcomes. Eligible patients were undergoing major spine surgery (defined as primary fusion involving at least 4 levels, revision surgery including at least 3 levels, AP fusion, anticipation of greater than 6 hours of surgery or greater than 1L of blood loss, corpectomy, pedicle subtraction osteotomy, or revision anterior fusion), had significant medical comorbidities, were taking buprenorphine, or had a pain pump or stimulator present.  The pre-pathway cohort included 183 patients who underwent surgery between 2012-2013, and the post-pathway cohort included 267 patients who underwent surgery between 2015-2016. The authors also included a cohort of 108 patients who underwent surgery from 2015-2016 who were eligible for the pathway but who were not placed on the pathway due to logistical issues as a contemporaneous control group. They found that the pathway patients had significantly lower hospital LOS (6.1 days) compared to the pre-pathway (8.2 days) and contemporaneous control (7.6 days) groups. The average ICU stay was also one day shorter for the pathway group compared to the other two groups. The pathway and contemporaneous control groups were both less likely to be admitted to the ICU compared to the pre-pathway group. Complication and readmission rates were similar for the three cohorts. The total cost of care was about $9000 less for the pathway group compared to the pre-pathway group and about $4,500 less compared to the contemporaneous control group.

The authors should be congratulated for performing the multidisciplinary work necessary to create such a pathway in a bureaucratic academic medical center. Their study demonstrates a significant improvement in length of stay and cost, without an increase in complication or readmission rate. Before-after studies evaluating outcomes in a real practice environment are always limited by potential confounders and secular trends (i.e. practice change over time not related to the intervention), though the authors attempted to mitigate this through the use of a contemporaneous control group. While that group may have been different in unmeasured ways compared to the pathway group, inclusion of that group is probably the best the authors could do in order to control for secular trends. This study does demonstrate the benefit of a care pathway for complex spine surgery, and many institutions have made efforts to adopt spine surgery care pathways. The most difficult aspects of implementing such a pathway are getting a diverse group of providers to agree on the details of the pathway and then actually getting the multidisciplinary (i.e. nurses, physical therapists, social workers, anesthesiologists, orthopaedic spine surgeons, and neurosurgeons) group to follow it. Hopefully this paper can be an inspiration to other institutions to do the hard work necessary to implement such a pathway.

Please read Dr. Dagal's paper on this topic in the July 1 issue. Does this motivate you to work on a care pathway in your institution? Let us know by leaving a comment on The Spine Blog.

Adam Pearson, MD, MS
Associate Web Editor

 


Friday, June 14, 2019

The literature makes it very clear that preoperative opioid use is associated with worse outcomes and more frequent complications following spine surgery. However, most of these studies have used large administrative databases with limitations inherent with that type of study design. In order to get a more detailed understanding of how preoperative opioid use affects postoperative outcomes, Dr. Hills and colleagues from Vanderbilt used their institution's spine surgery registry to identify over 2000 elective spine surgery patients from 2010-2017. They then queried the Tennessee Prescription Drug Monitoring Program (PDMP) to determine opioid prescription volumes for the 9 months prior to surgery and 12 months after surgery. They converted prescribed opioids to morphine milligram equivalents (MME) and defined high preoperative opioid use as greater than 30 MME per day for the two weeks preceding surgery. They defined chronic opioid use as using opioids on at least 50% of the days for at least a three-month period. At baseline, the chronic opioid users were significantly younger, more likely to be smoking, more likely to have arthritis, more likely to have Medicare or Medicaid, more likely to be ASA class 3 or 4, more likely to have anxiety or depression, more likely to be undergoing revision surgery, and had worse baseline symptoms. In their unadjusted analyses, they found that chronic opioid users were less likely to see a clinically meaningful improvement (defined as a 30% improvement vs. baseline) on the numeric rating scale for arm/leg pain, neck/back pain, the NDI/ODI or the EQ-5D. They were also less likely to be satisfied, less likely to return to work, more likely to have postoperative complications, and much more likely to use opioids chronically after surgery. Multivariate logistic regression showed all of these results to hold true while controlling the measured baseline differences. After controlling for chronic opioid use, high dose use did not portend worse outcomes than lower dose use other than increasing the odds of chronic use postoperatively. Only one third of chronic opioid users stopped their chronic use postoperatively.

While much has been written about the association between preoperative opioid use and poor outcomes following spine surgery, this study adds to the literature by looking at the topic in closer detail and including patient reported outcomes. The authors looked at both chronicity of use and dose and found that chronicity was a much stronger predictor of poor outcomes than high dose use. These results suggest that lower dose use over many months could be just as harmful for outcomes as higher dose use. The results held true even after accounting for the significant baseline differences between the two groups. This study begs the question about the effect of preoperative weaning of opioids but does not provide any data on whether or not that is effective. It is not clear if chronic opioid use causes permanent changes in pain pathways that are the driver of poor outcomes or if these changes are reversible with weaning. Additionally, chronic opioid use may be associated with other unmeasured confounders that are the true causative agents behind the poor outcomes. In reality, the relationship between preoperative chronic opioid use and outcomes is highly complex. There is essentially no doubt that patients would do better postoperatively if they wean down or stop opioid use preoperatively, though the magnitude of that benefit on patient reported outcomes is unclear. Observational studies likely cannot definitively answer the question about whether or not weaning opioids is helpful due to the potential for unmeasured confounders. Similarly, an RCT would be challenging to interpret on an intention to treat basis due to a likely high rate of failure to wean among those randomized to weaning. Determining the magnitude of benefit of preoperative opioid weaning may be academic as it seems almost certain to convey some benefit. Additionally, many patients are likely not willing to be weaned preoperatively and draconian weaning efforts would most likely result in illicit opioid use. Hopefully the opioid problem will improve over the long-term as physicians continue to change their prescribing habits and surgeons encounter fewer spine surgery patients on chronic opioid therapy. Until then, patients and their surgeons will likely continue to struggle with this.

Please read Dr. Hill's article on this topic in the June 15 issue. Does this change how you view the effect of preoperative chronic opioid use on spine surgery outcomes? Let us know by leaving a comment on The Spine Blog.

Adam Pearson, MD, MS

Associate Web Editor


Friday, June 7, 2019

Spinal hardware is subject to very high loads following adult deformity surgery, and the bone-screw interface is essential in order to prevent loss of fixation. Additionally, fracture within the fusion construct or adjacent to it can also occur in patients with low bone density. The deformity literature and anecdotal surgeon experience have made it clear that osteoporosis is a major risk factor for failure following adult deformity surgery, yet surgeons have little to no evidence-based guidance about how to determine if bone density is sufficient for a planned surgery. Additionally, there are no guidelines addressing which patients need bone density evaluation or treatment of low bone density pre-operatively. Given this void in the literature, Dr. Kuprys and colleagues from New York retrospectively reviewed a cohort of 314 patients undergoing spinal fusion of five or more levels. They performed a chart review to determine how many patients had bone density was documented in the pre-operative evaluation, how many underwent evaluation with DEXA or vitamin D level analysis, how many were treated with vitamin D, calcium, or medications to increase bone density, and how many were referred to a bone density specialist. They studied trends in these outcomes over time from 2012-2017. The average age of the cohort was 63, and 65% were female, indicating that a high proportion of their cohort was at risk for osteoporosis. In general, rates of bone health evaluation and treatment did not change significantly over time other than documenting bone health in the record, which increased form 12% in 2012-2014 to 26% in 2016-2017. Overall, 24% had a pre-operative DEXA scan documented in the record, which did not increase significantly over the study period. The rate of DEXA in men did increase over time, from 0% in 2012-2014 to 19% in 2016-2017. Not surprisingly, the rates of bone density evaluation and treatment were higher for females and those over 65.

This paper does not offer guidelines for how to consider low bone density while planning adult deformity surgery or how to evaluate and treat it pre-operatively. However, it does shine a light on the glaring lack of guidelines and knowledge in this field. The study demonstrates relatively low rates of work-up for low bone density in this population, which is probably not appropriate. Overall, 29% of women had pre-operative DEXA scans documented, as did 32% of patients over age 65. Given the high rate of low bone density in these populations and the importance of good bone density to have a successful outcome with major deformity surgery, a higher proportion of female and elderly patients should have probably undergone bone density evaluation. Currently, surgeons are left to practice the art of medicine without evidence-based guidance when determining who to work-up and treat for low bone density and how to determine if bone density if sufficient for a given surgery. Is it reasonable to perform a pedicle subtraction osteotomy and scoliosis correction in a 65 year old female with a T-score of -2.8 at her femoral neck? No one knows the answer to this question, though the chance of failure is higher than in the same patient with a T-score of -1.8. If low bone density is being treated, to what level does the bone density have to improve prior to going ahead with surgery? Do patients need to be off their antiresorptive therapy perioperatively, and, if so, for how long pre- and post-operatively? Surgeons currently do not have guidelines to allow them to answer these questions, and they are important questions encountered daily in a busy spine practice. Hopefully this article and others will serve as an impetus for spine societies to produce guidelines for the evaluation and management of bone density in spine fusion surgery.

Please read Dr. Kuprys's article on this topic in the June 15 issue. How do you consider bone density when planning adult deformity surgery? Let us know by leaving a comment on The Spine Blog.

Adam Pearson, MD, MS
Associate Web Editor


Friday, May 31, 2019

The role of chemical anticoagulation following spine surgery remains unclear, and current NASS guidelines do not suggest the routine use of chemical anticoagulation following elective spine surgery. Cancer and immobility secondary to neurological deficit are known risk factors for venous thromboembolism (VTE), and major decompression and stabilization surgery increases the risk of VTE even further. As such, spine tumor surgery patients are at increased risk of VTE, and there is no consensus on when to start chemical anticoagulation (AC), what AC agent to use, the appropriate dosing of the AC agent, and duration of its use. In order to gain some insight on this topic, Dr. Ramos and colleagues from New York reviewed sixty-five spine tumor surgery cases from a single institution from 2012-2018. All patients had at least 30 days of follow-up. They reported that patients had early surveillance for DVT, though they did not specify what this entailed. The attending surgeon was responsible for the decisions regarding AC (i.e. whether to initiate, timing of initiation, agent, dose, and duration). Overall, they reported a 17% DVT rate in the first 30 days, and a 3% rate of non-fatal PE (no fatal PEs occurred). They then stratified the patients according to post-operative AC status, with an early chemical AC group in which AC was started from post-operative day 1-3 (n=22), a late group started on post-operative day 4 or later (n=14), and a no AC group (n=29). All patients received sequential compressive devices following surgery. For unclear reasons, they did not include the no AC group in their analysis. The early group had a VTE rate of 9% compared to 36% for the late group, and this was statistically significant. While there were no statistically significant baseline differences between the early and late groups, the early group had a higher rate of prior VTE (14% vs. 7%), while the late group included more males (64% vs. 40%), more smokers (50% vs. 23%), and had lower modified Bauer scores (1.7 vs. 2.4). Controlling for these differences did not change the conclusion, and multivariate analysis yielded an odds ratio of 6.4 comparing the odds of VTE in the late vs. early groups. There was one epidural hematoma requiring surgical evacuation in the early group and none in the late group. Based on these data, the authors suggested that early initiation of chemical AC reduced the rate of VTE in spine tumor surgery patients.

This paper shines a light on how little is known about this topic, though the small numbers included preclude any strong conclusions. The most serious concern with this paper is that the authors elected not to include the no AC group, and this decision is not discussed. A back of the envelope calculation demonstrates that the no AC had a VTE rate of 14%. This is not statistically significantly different from the 9% rate in the early group. Given these data, it is not possible to conclude that early anticoagulation reduces the rate of VTE vs. no AC. It is not clear why the late AC group has a higher VTE rate compared to the no AC group, though baseline differences likely account for the finding. The authors did not report the demographic and baseline characteristics of the no AC group, so it is not possible to know how they were different. Given that the surgeons elected not to start AC in this group while they started it on post-operative day number 4 or later in the late group indicates that there were likely clinical differences between the two groups. While this paper does not add much data to the discussion regarding AC following spine tumor surgery, it does shine light on our lack of knowledge on the topic. These patients are at increased risk for both VTE and epidural hematoma, and surgeons are challenged to balance these risks. As this paper demonstrates, it is very difficult to generate a sufficiently large cohort to study the topic, and it would be even harder to perform an RCT on the topic. A large, multicenter observational study is likely the best approach to generate sufficient numbers to answer this question. Until such a study is performed, surgeons will be left with only their judgment to guide this high-risk decision.   

Please read Dr. Ramos's article on this topic in the June 1 issue. Does this change how you view the use of chemical AC following spine tumor surgery? Let us know by leaving a comment on The Spine Blog.

Adam Pearson, MD, MS
Associate Web Editor


Friday, May 24, 2019

Tranexamic acid (TXA) is now widely accepted as an effective means to reduce blood loss during spinal deformity surgery, and it is now being adopted for any fusion surgery in which significant blood loss is anticipated. Most of the spine surgery literature has evaluated IV TXA, typically administered as an initial bolus followed by a continuous infusion for the remainder of the case. The total joints literature has demonstrated the efficacy of oral and topical TXA, though the spine literature has not evaluated the PO preparation. Advocates of PO TXA note the reduced cost and ease of administration. In order to compare IV and PO TXA in spinal fusion, Dr. Yu and colleagues from Detroit performed an RCT in which 83 patients undergoing lumbar or thoracolumbar fusion were randomized to receive IV or PO TXA. The IV medication was given as a 1 g bolus prior to incision followed by a second 1 g bolus prior to closure. The patients randomized to PO TXA received 1.95 g PO 2 hours prior to incision. The average fusion length was 3.8 levels, 15% underwent pedicle subtraction osteotomies, and 26% underwent interbody fusions. The two groups were very similar at baseline, though the IV group had a significantly lower BMI (28.5 vs. 32.1) and lower baseline platelet count (205 vs. 240). The IV group was also less likely to undergo an interbody fusion (16% vs. 38%). The primary outcome, drop in hemoglobin, was not significantly different between the two gropus (3.36 g/dL IV vs. 3.43 g/DL PO). The other outcome measures, including estimated blood loss, drain output, rate of post-operative transfusion, and rate of thromboembolic events, were not significantly different between the two groups. The authors concluded that PO TXA was equally as effective as IV TXA and recommended the use of PO TXA due to its lower cost ($14 vs. $53) and ease of administration.

The authors should be congratulated for successfully performing a Level 1 RCT addressing a clinically relevant question. The results strongly suggest that PO and IV TXA are equally as effective and have similarly safe side effect profiles. The authors do not comment on blinding, so one must assume the study was not blinded. It would have been relatively easy to blind the surgeons (and potentially the patients) to group assignment, though it is not clear that would have affected the results in a meaningful way. The main outcome measure, drop in hemoglobin, is not subjective and was unlikely subject to bias. The only other concern with the methodology is that the authors did not use a continuous IV infusion during surgery, and IV TXA given as a bolus is likely not circulating at a sufficient concentration to be effective in surgeries over four hours long (the average surgery was about 4 ½ hours). As such, the IV TXA patients undergoing longer surgeries may have had lower blood loss if a continuous infusion was performed for the duration of the case. While the conclusion that IV and PO TXA are equally effective is likely valid, it is unclear if PO TXA should be widely adopted. In the scope of a spinal fusion surgery that likely costs tens of thousands of dollars, a $40 savings is negligible. The authors do point out that changing to PO TXA could save the US healthcare system $20 million per year, though sadly that is a rounding error when it comes to national healthcare expenditures. The argument that administering PO TXA is easier than IV TXA is also questionable, as it requires that the medication is given 2 hours prior to incision. Some patients do not arrive until less than two hours before surgery, and it is easy to imagine that the dose is missed or delayed in the pre-operative holding area. At my institution, TXA is administered by anesthesia along with pre-operative antibiotics, and this is confirmed at the time out. In this model, if the TXA is overlooked, it is caught at the time out and administered prior to making the incision. This paper makes it clear that PO TXA is a reasonable option in systems that find using it advantageous. A more pressing question is defining the indications for TXA use. Given its good safety profile, it seems reasonable to consider using it in any lumbar or thoracolumbar fusion.

Please read Dr. Yu’s article on this topic in the June 1 issue. Would you consider using PO TXA at this point based on this article? Let us know by leaving a comment on The Spine Blog.

Adam Pearson, MD, MS
Associate Web Editor