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Friday, April 24, 2015

Results of industry-sponsored IDE trials comparing cervical disk arthroplasty (CDA) to ACDF have been promising, demonstrating low complication rates, similar patient-reported outcomes, and significantly lower re-operation rates over the short-term. However, adoption of CDA has been relatively slow, likely due to a lack of surgeon enthusiasm related to skepticism of industry-sponsored studies, relatively good outcomes with ACDF, concern about long-term durability, and difficulty obtaining reimbursement. Given the possible cost-savings associated with CDA with its similar upfront costs and a potentially lower re-operation rate compared to ACDF, Dr. Radcliff and associates used the Blue Health Intelligence database to evaluate costs and re-operation rates for CDA and ACDF in a “real-world” retrospective cohort study. While the study was funded by Synthes, the database includes 110 million patients covered by BlueCross BlueShield and reflects actual practice outside the strict confines of an IDE trial. From 2008-2009, they identified 6635 single level ACDF patients and 327 single level CDA patients between the ages of 18 and 60. The CDA group was almost 3 years younger and had a slightly lower comorbidity burden. About 2/3 of patients had claims data for at least two years post-operatively, with follow-up dropping off substantially after that as patients changed healthcare coverage. The authors reported a reoperation rate twice as high for ACDF compared to CDA (approximately 10% vs. 5%). It should be noted that only 10 CDA patients underwent re-operation, so the numbers involved are quite small. The causes of re-operation were not reported, but the authors did report a significantly higher rate of “mechanical complications” in the ACDF cohort, with no such complications being reported in the CDA group. Index surgery costs were about $2,000 less for the CDA group, likely reflecting local differences in contracted prices rather than differences in implant or hospitalization costs. Overall costs of the index operation and three years of follow-up were about $5,000 less for the CDA group, though the causes of these differences were not explored. The average length of stay was about 3.5 hours less for CDA, and there were no significant differences in readmission rates.

 

The findings from this retrospective database study support the findings of prior RCTs demonstrating lower re-operation rates for CDA. However, the results of the current study should be interpreted carefully due to many of the limitations inherent to all database studies as well as some that are unique to the current investigation. The decision to reoperate reflects a subjective choice made by patient and surgeon, and this can be influenced by patient and surgeon characteristics. Given that only 327 CDA patients were included in the study and only 10 of these patients underwent reoperation, specific patient and surgeon factors could influence this rate. As such, the results may not reflect practice across the entire spine community. Additionally, there were likely substantial unmeasured differences between the CDA and ACDF populations, and the authors did not compare characteristics like gender, smoking status, BMI, worker’s compensation status, psychosocial comorbidities, and socioeconomic status between the two groups. All of these factors could have affected outcomes. Costs beyond the initial surgery and hospitalization were undoubtedly affected by reoperation rates, but other factors such as the use of physical therapy, injections, and imaging also affected costs and could have been utilized differently by ACDF and CDA patients. This paper adds to the growing literature that suggests CDA is a reasonable alternative to ACDF with similar clinical outcomes and possibly a lower rate of reoperation and lower costs over the short- and medium-term. Long-term data will likely be needed prior to widespread adoption.

 

Please read Dr. Radcliff’s article on this topic in the April 15 issue. Does this paper change how you view CDA as an alternative to ACDF? Let us know by leaving a comment on The Spine Blog.

Adam Pearson, MD, MS

Associate Web Editor

 


Friday, April 17, 2015

Antifibrinolytics have been used with increasing frequency in cardiac surgery, total joint replacement surgery, and spinal deformity surgery in order to reduce blood loss and complications associated with anemia and transfusion. The results from the spine surgery literature on this topic have been somewhat mixed, though many studies have suggested an advantage for the fibrinolytics. These prior studies have varied substantially in the medication used, dosage, type of surgery, and use of intra-operative hypotension, which likely accounts for the mixed results. In the current study, Dr. Peters and his colleagues from New York performed a double-blinded RCT comparing tranexamic acid (TXA), aminocaproic acid (ACA), and placebo in adult deformity surgery, defined as thoracolumbar fusion involving at least five levels. While the details of the power analysis were not provided, the authors noted the investigation was stopped early given the positive results of the adolescent idiopathic scoliosis study on the same topic. As a result, the number of enrolled patients was relatively low, with 19 in the TXA and ACA groups and 13 patients in the control group. The average fusion length was 12 levels, and this was similar for the three groups. The TXA group was significantly older (60 years) compared to the ACA (47 years) and placebo (43 years) groups. The average duration of surgery was about 5 hours. Intraoperative blood loss was 1400 cc for the TXA group, 1100 cc for the ACA group, and 2200 for the control group. Despite the large differences, these were not statistically significant. Total blood loss (intraoperative plus post-operative drain collection) was significantly lower for ACA vs. placebo (2400 cc vs. 4100 cc), with the TXA group having an intermediate result (3100 cc). Post-operative transfusion rates were 53% for TXA, 11% for ACA, and 46% for placebo, with the ACA rate being significantly lower than the TXA rate. There was one case of pulmonary embolism in both the TXA and ACA groups.

 

This investigation had the potential to be a high quality, level 1 study, but the ethical decision to stop the study early limited the conclusions that could be drawn due to the study being markedly underpowered. Despite the lack of statistical significance for many of the comparisons—likely representing Type II error due to insufficient enrollment—the data suggest that TXA and ACA both reduce intraoperative and total blood loss. There were trends suggesting that ACA was somewhat more efficacious than TXA, though the low numbers and limited power precluded strong conclusions comparing the two medications. This and other studies indicate that fibrinolytics have a place in spinal deformity surgery, however, the best agent and dosing strategy remain unknown. Future RCTs can help to answer these questions, but this study demonstrates the need for sufficient enrollment numbers in order to draw meaningful conclusions that can dictate practice. While large numbers of patients are likely needed to determine the best agent and dosing strategy, even greater numbers are required to evaluate the safety of the regimens given the low frequency of adverse events associated with the medications, such as thromboembolism. Enrolling large numbers of adult deformity patients is difficult—it took nearly four years to enroll 52 patients in the current study at a high volume deformity center—and a multicenter study is likely needed to advance the science on this topic.

 

Please read Dr. Peters’s article on this topic in the April 15 issue. Will it change how you use antifibrinolytics in your spinal deformity practice? Let us know by leaving a comment on The Spine Blog.

Adam Pearson, MD, MS

Associate Web Editor


Friday, April 10, 2015

Civilian gunshot wounds (CGSW) involving the spinal column are relatively rare, and no large, modern case series has been published on this topic. Spine fractures commonly occur when a bullet strikes a vertebra, and neurologic deficits frequently result from direct damage to neural structures or from the energy imparted to the soft tissues as the bullet passes nearby. There has been a general trend towards non-operative treatment of these fractures, though no GSW-specific classification system exists to classify instability or guide treatment decision-making. Given the gaps in the literature, Dr.Bumpass and colleagues from Washington University in St. Louis reviewed their experience with spinal CGSWs from 2003-2011. Over this nine year time frame, they treated 159 spinal CGSW patients, equivalent to about 18 such patients per year. I’m not sure what this suggests about the crime rate in St. Louis, but it represents one of the largest case series ever assembled on this topic. Not surprisingly, the patients were overwhelmingly young and male, with an average age of 28 and including 92% men. Fifty percent of patients presented with a neurological deficit, and half of these patients were ASIA A (complete cord injury). There was roughly an even distribution of injuries affecting the cervical, thoracic, and lumbar spine. The vast majority (94%) were treated non-operatively, with only 10 patients undergoing surgical treatment. Of those 10, 2 were treated in a delayed fashion for infection and 1 for persistent CSF leak 6 days after the GSW. Five underwent decompression and stabilization for incomplete cord injuries with residual cord compression, and 2 had early surgery for presumed instability. About 1/3 of patients with an initial neurological deficit had some degree of improvement over the course of follow-up, and this rate was similar for those treated with and without surgery. Similar to non-GSW cord injuries, improvement was less likely for ASIA A patients. Complications were common, affecting 80% of surgery patients and 43% of non-operative patients, with complication risk correlating strongly with severity of neurological deficit. There were no cases of progressive neurological deficit or delayed instability in those treated non-operatively.

 

The authors should be congratulated for assembling such a large series of spinal CGSWs. The results make it clear that initial non-operative treatment is indicated in the vast majority of cases. Persistent spinal fluid leak and infection are clear indications for surgery. The role of surgery for patients with incomplete cord injuries with residual cord compression remains unclear. It is likely that most of the cord damage occurred at the time of injury, and the degree of improvement that can be expected from decompression is uncertain. Presumed instability is another ambiguous indication for surgery as there is no clear definition of instability in the case of spinal GSW. While blunt trauma usually leads to ligamentous injury in addition to fracture, the soft-tissue stabilizers are generally intact with GSW, making instability uncommon. The fact that no patients had to undergo surgery for delayed instability supports this concept. While we always prefer Level I evidence to support our decision-making, this is a subject on which such a study will likely never be performed. The current paper is probably the best evidence that will be compiled for spinal CGSWs, and it provides further support to the trend of initial non-operative treatment for the vast majority of these injuries.

 

Please read Dr. Bumpass’s paper in the April 1 issue. Does this change how you approach spinal CGSWs? Let us know by leaving a comment on The Spine Blog.

Adam Pearson, MD, MS

Associate Web Editor


Friday, April 03, 2015

Adjacent level ossification development (ALOD) has been recognized as a sequela of anterior cervical plating for over a decade, though its clinical significance is poorly understood. While ALOD shares some features with adjacent segment degeneration (ASD), it is unknown if ALOD and ASD result from similar pathological processes and if ALOD progresses to ASD affecting the entire motion segment. Authors have recognized that ALOD is more common when the distance from the plate to the adjacent disk space (plate disk distance, PDD) is small, suggesting that ALOD could be a local response to the plate or dissection near the adjacent disk. With this background, Dr. Yang and his colleagues from Shanghai reviewed 218 ACDF cases to evaluate the relationships between PDD, ALOD, and ASD. Plate disk distance was classified as long (>5 mm), short (0-5 mm) or none (plate overlapped adjacent disk space). Previously described grading systems were used for ALOD and ASD, which were evaluated on post-operative films and MRI at an average follow-up of over 5 years. Radiographic adjacent segment degeneration was defined based on either disk height loss or hypermobility on x-rays or loss of T2 signal on MRI. Patients with radiographic ASD plus radiculopathy or myelopathy attributable to the ASD were classified as having symptomatic ASD. The authors reported that 61% of patients had ALOD at the cranial level, and 24% developed it at the caudal level. Cranial ALOD developed in 31% of the “long” PDD group, 66% in the “short” group, and 100% in the “none” group. On the other hand, ASD occurred about 45% of the time, was equally common cranially and caudally, and was not related to PDD. Symptomatic ASD occurred in only 3% of patients and was also not related to PDD. Based on these results, the authors concluded that short PDD led to ALOD but not radiographic or symptomatic ASD.

 

This paper represents a good retrospective study demonstrating a clear relationship between PDD and ALOD, supporting the results of prior studies that have also reported this association. The paper would have been stronger if they had reported the relationship—or more likely the lack thereof—between ALOD and ASD. Rather than looking at this directly, the authors implied that ALOD and ASD were not related as PDD was shown to be associated with ALOD but not ASD. This study also has all the limitations inherent in a retrospective design. Since the follow-up time was not set, it varied widely from 3-10 years. It is possible that patients treated earlier in the series had smaller PDDs as the author was not familiar with PDD and ALOD at that time, and these patients would have more time to develop ALOD. The timing of MRI was also not well defined and could also affect the rate of ASD (i.e. patients with longer follow-up were more likely to have ASD). Multiple plate designs were used, and plate design could also affect PDD and ALOD. The lack of patient reported outcomes is a significant limitation as it remains unclear if ALOD affects clinical results. The paper does a nice job distinguishing ALOD from ASD and suggests that they represent two distinct pathologic processes. The development of ALOD appears to be a local phenomenon due to either the interaction between the plate and the adjacent disk space or dissection at the adjacent disk space leading to anterior osteophyte formation. It does not seem to result in degeneration in the disk space or facet joints, and, unlike posterior osteophyte formation or uncovertebral hypertrophy, anterior osteophytes do not compress neural structures. The authors raised the possibility of a prospective observational study including patient reported outcomes, and that would certainly improve that quality of evidence for this topic.


Please read Dr. Yang’s article on this topic in the April 1 issue. Have you changed your anterior cervical plating technique in order to maximize PDD and minimize ALOD? Let us know by leaving a comment on The Spine Blog.

Adam Pearson, MD, MS

Associate Web Editor


Friday, March 27, 2015

Many studies have demonstrated high rates of “abnormal” MRI findings in asymptomatic patients. However, most of these have been lumbar spine studies. Cervical spine studies on the topic have generally included small numbers of patients across a limited age spectrum. Recently, some spine surgeons have advocated surgery in asymptomatic patients with cervical spinal cord compression with T2 cord signal changes. To shed more light on the topic, Dr. Nakashima and colleagues from Japan performed a study in which over 1,200 asymptomatic subjects equally distributed across the age spectrum and across both genders underwent cervical spine MRI. They evaluated disk bulging (defined as over 1 mm of bulging into the canal), spinal cord compression (SCC), and increased T2 cord signal intensity (ISI). Not surprisingly, the vast majority of subjects across all age ranges had some degree of disk bulging, with the frequency of disk bulging increasing with age. Spinal cord compression and ISI were very rare in patients under 50, though over 15% of men in their 70s had SCC and 8% had ISI. Rates of SCC and ISI were lower in women.

 

The authors should be congratulated on obtaining funding for and successfully completing this large scale study. Such large numbers are required in order to compare trends across the age spectrum, especially when rates of SCC and ISI are relatively low. For practicing spine practitioners, these findings come as no surprise. We frequently see patients with SCC and ISI who are not myelopathic and present only with neck pain. This cross sectional study represents a snapshot in time, so while it identifies asymptomatic patients with SCC and ISI, it does provide any prognostic information. The authors performed physical exams on all patients, but these results are not presented or correlated with the MRI findings. It would be interesting to know if those with SCC and ISI were more likely to have myelopathic signs on exam. Hopefully the authors will follow this cohort to see if those with SCC and ISI develop myelopathy. Those data would be very helpful for surgeons trying to decide what to do with asymptomatic patients or those with subtle myelopathic findings who have SCC and/or ISI on MRI. Currently, we do not know how they are best treated as we do not know the natural history of their condition.

 

Please read Dr. Nakashima’s article on this topic in the March 15 issue. Does this change how you view the asymptomatic patient with SCC or ISI on cervical spine MRI? Let us know by leaving a comment on The Spine Blog.

Adam Pearson, MD, MS

Associate Web Editor

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Spine Journal
This Blog provides a forum for discussion about high impact articles published in Spine, including the bi-annual publication of "Evidenced-Based Recommendations for Spine Surgery." Website users can use this forum to discuss how the articles have affected their practice and query the authors about their findings and recommendations.