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The Spine Blog

Saturday, February 15, 2020

Studies across orthopaedics, spine surgery, and most medical specialities have demonstrated worse outcomes for depressed patients and those with other mental health problems. However, the magnitude of the effect has been highly variable and depended on the condition under study and how depression and mental health were defined. To better understand the association between baseline mental health and patient reported physical function following MIS-TLIF, Dr. Yoo and colleagues analyzed 172 patients with baseline SF-12 mental component summary (MCS) scores and post-operative PROMIS physical function (PF) scores out to one year. They divided the patients into a low MCS cohort (< 50) and a high MCS cohort (>50), with approximately 50% of patients in each group. The low MCS group was significantly younger (49 vs. 53), more likely to have worker's compensation insurance (38% vs. 15%), and had worse baseline PF scores (34 vs. 37). After controlling for age and worker's compensation status, the low MCS group had significantly worse PF scores at each time point. However, the PF change scores were very similar, with the only significant difference being a greater improvement in PF for the high MCS group at 1 year (11 vs. 9).

The authors have performed a straightforward study demonstrating significantly worse absolute PF scores in the low MCS group but similar change scores other than at 1 year. The two groups were fairly similar at baseline on the measured variables other than age and worker's compensation status. Worker's compensation status is a strong predictor of worse outcomes, though the authors did control for this with multivariate analysis. However, they did not measure many other well-known outcome predictors including diagnosis (i.e. outcomes are worse for degenerative disk disease than degenerative spondylolisthesis), duration of symptoms, opioid use, socioeconomic status, educational attainment, and work status. These variables may have been associated with MCS score and could have been confounders as they were not controlled for in the analysis. By dividing patients into MCS groups using the population mean (50) as the cut-point, the authors likely obscured an even stronger effect of more severe mental health problems. Prior studies have indicated that a score of less than 35 was strongly associated with depression. In a similar analysis, the Spine Outcome Research Trial (SPORT) compared change in ODI scores following surgery and non-operative treatment for degenerative spondylolisthesis between patients with MCS above and below 35.1 This SPORT showed the MCS < 35 group improved significantly less with surgery and non-operative treatment than the MCS > 35 group over 4 years. As such, the treatment effect of surgery (the difference between the surgery and non-operative change scores) was similar for both groups. While it is clear that depressed patients and those with other mental health problems generally do not do as well with surgery as those with normal mental health, the literature indicates that surgery still offers an advantage over non-operative care. What remains unclear is how much benefit patients get from treating depression pre-operatively, and hopefully future studies can answer that question.

Please read Dr. Yoo's article on this topic in the February 15 issue. Does this change how you consider the role of surgery for patients with mental health problems?

Adam Pearson, MD, MS

Associate Web Editor  

REFERENCE

1.            Pearson AM, Lurie JD, Tosteson TD, Zhao W, Abdu WA, Weinstein JN. Who should undergo surgery for degenerative spondylolisthesis? Treatment effect predictors in SPORT. Spine (Phila Pa 1976) 2013;38:1799-811.

 

 


Friday, February 7, 2020

Spine surgeons have been focused on achieving appropriate sagittal balance in their adult deformity patients for at least the last 10 or 15 years.1 When the topic was initially introduced, it was felt that the goal for all patients was to achieve "optimal" sagittal balance, namely a sagittal vertical axis (SVA) < 5 cm, pelvic tilt (PT) < 20⁰, and pelvic incidence (PI) minus lumbar lordosis (LL) < 9⁰.2 This approach resulted in a period of very aggressive correction, even in elderly patients, and was associated with a high rate of proximal junctional failure and revision surgery. More recently, spine surgeons have recognized that correcting elderly patients to these sagittal alignment "norms" derived from a younger population is not ideal. To better individualize alignment goals, Dr. Protopsaltis and the International Spine Study Group performed an analysis of over 900 adult deformity patients and over 100 asymptomatic volunteers. In addition to considering age, they also considered the role of pelvic incidence in establishing alignment goals. They also evaluated the T1 pelvic angle (TPA), an overall measure of sagittal alignment that is independent of lower extremity alignment. They created linear regression equations predicting sagittal alignment parameters (TPA, SVA, PT, and PI – LL) based on PI and SF-36 PCS score. They used these equations in their adult deformity cohort to determine SVA values that corresponded to normative age-specific PCS scores for different PIs. They reported that the ideal SVA based on the deformity cohort increased with age and increasing PI. For example, a patient under 45 with a PI < 40⁰ achieved a typical age-matched PCS score when SVA was -4 mm. On the other end of the spectrum, for patients over 65 with a PI > 75⁰, the optimal SVA was +57 mm. A similar pattern was observed for TPA using the asymptomatic cohort, with ideal TPA increasing from -3⁰ for younger patients with low PI to +25⁰ for elderly patients with high PI.

This group continues to publish insightful papers based on their very large adult deformity database, and they have done a nice job adjusting their beliefs about ideal correction as they have gained more data. The current paper supports the concept that less aggressive correction is desirable in elderly patients and also addresses the role that pelvic morphology plays. It is intuitive that patients with high pelvic incidence tend to tolerate higher degrees of positive sagittal "imbalance". For a fixed sacral slope (SS), pelvic tilt increases directly with pelvic incidence (i.e. PI = SS + PT). High PI patients have the femoral heads relatively anterior in relation to the sacrum, so a more forward alignment of the head is tolerated well as the C7 plumb-line can remain over the pelvic base of support. The strength of the correlations in this paper for the linear regression equations predicting sagittal alignment parameters based on PI and patient reported outcomes (PROs) are relatively modest (i.e. r2 < 0.3), indicating that these equations explain less than 30% of the observed variance. In other words, many other factors beyond sagittal balance parameters are driving outcomes in this population. Additionally, this paper looks only at baseline PROs and does not validate the concept that correction to the norms generated by these equations results in better outcomes and fewer re-operations. Nonetheless, the authors have made a compelling case that a "one size fits all" approach is inappropriate for adult deformity surgery, and factors such as age and pelvic morphology need to be considered while planning the magnitude of correction.

Please read Dr. Protopsaltis's paper on this topic in the February 15 issue. Does this change how you view the role of age and pelvic morphology while planning adult deformity surgery?

Adam Pearson, MD, MS

Associate Web Editor

REFERENCES

1.            Glassman SD, Bridwell K, Dimar JR, Horton W, Berven S, Schwab F. The impact of positive sagittal balance in adult spinal deformity. Spine 2005;30:2024-9.

2.            Schwab F, Patel A, Ungar B, Farcy JP, Lafage V. Adult spinal deformity-postoperative standing imbalance: how much can you tolerate? An overview of key parameters in assessing alignment and planning corrective surgery. Spine 2010;35:2224-31.

 


Friday, January 31, 2020

Early mobilization after spine surgery is generally viewed in a positive light, though the time point at which neck exercises are started following ACDF is highly variable. An RCT demonstrated no benefit to collar use after one level ACDF, though there is very limited data available on the role of collar use following multilevel ACDF.1 While many surgeons no longer recommend hard cervical collars following ACDF, activity restrictions following surgery remain commonplace. Few surgeons seem to advocate range of motion (ROM) and strengthening exercises prior to 6 weeks after surgery. There is essentially no evidence supporting the use of activity restrictions following surgery, and it is possible that such restrictions slow rehabilitation and return to work and activities. In order to better assess the role of an early home exercise program (HEP) following ACDF, Dr. Coronado and colleagues at Vanderbilt performed a small pilot RCT in which 30 ACDF patients were randomized to an early HEP or usual care. The program consisted of home stretching (up to 30 degrees of motion in any plane), gentle strengthening, non-pharmacologic pain management strategies (i.e. relaxation, deep breathing), and a weekly phone call from a physical therapist to discuss progress. The vast majority (87%) underwent one or two level surgery, and a high proportion (73%) had myelopathy. The only significant baseline difference between the groups was a greater comorbidity burden in the early HEP group. Following surgery, the only difference in patient reported outcomes (PROs) was a greater improvement (1.7 points on a 10-point scale) in neck pain at 6 weeks in the early HEP group. There were no differences in PROs at 6 or 12 months. At 12 months, the early HEP group had a significantly lower proportion of patients using opioid medications (13% vs. 47%, p = 0.05). There were no adverse events related to the early HEP and no differences in fusion rates, though fusion was not evaluated in a rigorous fashion. There were no re-operations in the first 12 months in either group.

The authors have done a nice job completing a pilot study that raises awareness of an important issue that is frequently ignored by surgeons. As a group, surgeons tend to be much more interested in technical details that rarely affect outcomes than topics such as post-operative rehabilitation protocols. Other than the significant difference in opioid use at one year, this paper did not demonstrate much benefit to the early HEP other than subjective support among patients in the early HEP group. However, the authors may have failed to capture the relevant outcomes for this study. More important than traditional PROs at 6 weeks, 6 months and a year after surgery may have been early outcomes such as pain at 2-4 weeks, timing of return to work and activities (i.e. driving), early analgesic use, and early ROM. The huge difference in opioid use at 12 months is somewhat hard to understand, especially since baseline opioid use in both groups was not reported. A nearly 50% opioid use rate in the usual care group would not be expected unless the study population had a high baseline opioid use rate. The protocol for determining fusion rate was very weak, but there are no data to suggest that early activity is associated with nonunion following ACDF using an anterior plate. This study should raise awareness of the issues surrounding post-operative activity and restrictions following ACDF. Hopefully the authors are designing a larger trial with more relevant outcome measures that could help us better understand the risks and benefits of early exercises following ACDF.

Please read Dr. Coronado's paper on this topic in the February 15 issue. Does this change how you view early activity following ACDF?

Adam Pearson, MD, MS
Associate Web Editor

REFERCENCE

1.            Campbell MJ, Carreon LY, Traynelis V, Anderson PA. Use of cervical collar after single-level anterior cervical fusion with plate: is it necessary? Spine (Phila Pa 1976) 2009;34:43-8.

 

Saturday, January 25, 2020

Proximal junctional failure (PJF) is one of the main contributors to the high reoperation rate following adult deformity surgery. Overcorrection of sagittal deformity and stiff pedicle screw instrumentation at the upper instrumented vertebra (UIV) have been identified as two modifiable risk factors for PJF. However, there is little published evidence indicating that less aggressive correction or using alternative instrumentation at the cranial end of the construct will reduce PJF. In order to better assess the role of these two PJF risk factors, Breton Line and the International Spine Study Group queried their prospectively collected adult spinal deformity database to analyze the associations between overcorrection and cranial implant type and PJF. They defined PJF as proximal junctional angle greater than 28⁰, proximal junctional angle change greater than 22⁰, or an increase in proximal junctional anterolisthesis of 8 mm in the upper thoracic spine and 3 mm in the lower thoracic spine. Patients with a pelvic incidence – lumbar lordosis difference less than age appropriate norms were classified as overcorrected. The cranial instrumentation was classified as traditional pedicle screw, transverse hook, pedicle screw plus cement at the UIV and UIV + 1, or polyethylene tether at UIV +1 and/or UIV + 2. They included 625 adult deformity patients with a mean age of 62, including over 70% females, with an average of 13 levels fused. Almost 90% had a fusion to the pelvis. Two cohorts of patients were propensity score matched on risk factors for PJF and stratified on the use of PJF-reducing implants at the cranial end of the construct (i.e. hook, tether, cement vs. traditional pedicle screws alone). Over a mean follow-up of 2.6 years, 14% developed PJF and 7.4% underwent revision surgery for PJF. Patients treated with traditional pedicle screws at the cranial end of the construct had a PJF rate of 20% compared to 10% for the PJF-reducing implant group. The overcorrected group with traditional pedicle screws at the UIV had a PJF rate of 24% compared to 13% for the pedicle screw group without overcorrection. For those treated with a PJF-reducing construct at the UIV, overcorrection had no significant effect on PJF (11% vs. 10%).

As usual, this group has performed a high quality observational study using their extensive international database. All observational studies run the risk of selection bias and confounding by unmeasured variables, and it is possible that patient and surgeon characteristics were different among the cohorts defined by degree of correction and implant type. There were some differences among the different implant groups at baseline (i.e. the hook group was slightly younger, had less severe sagittal deformity, and were less likely to be fused to the pelvis), so the authors did not focus on comparisons among the PJF-reducing implant groups. Other unmeasured factors could have differed among the groups also, which could bias the results. The authors also did not include the use of 3-column osteotomy in their analysis as a variable, though overcorrection was likely associated with this risk factor. Despite the potential for selection bias and confounding by unmeasured variables, the effect size of using a PJF-reducing construct and avoiding overcorrection was huge (i.e. risk reduction of approximately 50% for each). The recent literature on this topic has made it clear that overcorrection, especially in the elderly population, should be avoided. This paper also supports prior literature suggesting that PJF-reducing implants at the cranial end of the construct may be helpful. Please read Mr. Line's paper in the February 15 issue. Does this change your view on strategies to reduce the risk of PJF in adult deformity surgery? Let us know by leaving a comment on The Spine Blog.

Adam Pearson, MD, MS
Associate Web Editor


Friday, January 17, 2020

Surgical site infection (SSI) is a dreaded complication following spine surgery that results in significant morbidity to patients and high costs to the healthcare system. The topic has been studied extensively, and the past decade has seen a decrease in SSI thanks to the use of intrawound vancomycin powder. In order to provide a broad, epidemiological snapshot of the topic, Dr. Zhou and colleagues from China performed a wide-reaching meta-analysis evaluating the prevalence of SSI and SSI risk factors. They excluded administrative database studies due to their lack of sufficiently detailed clinical information and analyzed 27 studies including over 22,000 patients. They reported an overall SSI rate of 3.1%. The surgical indication with the highest rate was for neuromuscular scoliosis (13%). Somewhat surprisingly, trauma and tumor cases were not associated with an increased rate compared to degenerative cases. The posterior approach had an SSI rate twice that of the anterior approach (5% vs. 2.3%), and instrumentation was also associated with an increased risk of SSI (4.4% vs. 1.4%). Minimally invasive surgery, surgical duration less than 3 hours, and blood loss less than 500 mL also had lower SSI rates. The use of intrawound vancomycin powder had a significant effect on SSI rate reduction (4.8% vs. 1.9%). Staph aureus was the most common pathogen (50% of infections), of which nearly half were methicillin-resistant.

The authors have performed a fairly exhaustive meta-analysis of SSI in spine surgery, and these rates can serve as useful benchmarks. The biggest game changer in SSI prevention—as this study indicates—has been the use of intrawound vancomycin powder, which has markedly reduced the SSI rate, especially in multilevel posterior instrumented fusions. Only 12 of the 27 studies stratified results based on the use of vancomycin powder, and this makes it more difficult to benchmark rates in the vancomycin era. It would have been helpful if the authors had stratified approach (i.e. anterior vs. posterior) by location (i.e. cervical vs. lumbar). Traditionally, the posterior cervical approach has been associated with the highest SSI rate and the anterior cervical approach with the lowest infection rate, but they did not look at this specifically. The overall rate is also difficult to interpret as it is not clear that the sample included is representative of the overall practice of spine surgery. A multivariate approach would have been useful to determine the independent risk factors for infection, as covariance plays a role with many of the variables (i.e. surgical duration and blood loss are tightly related). Overall, this paper provides some useful information for benchmarking SSI rates and again demonstrates the benefit of intrawound vancomycin powder in reducing SSI. Hopefully similar studies in the future including more patients treated with vancomycin powder will allow for new benchmarks for the different approaches and indications.

Please read Dr. Zhou's article on this topic in the February 1 issue. Does this change how you view SSI rates and risk factors? Let us know by leaving a comment on The Spine Blog.

Adam Pearson, MD, MS
Associate Web Editor