Does Medicare Insurance Mitigate Racial/Ethnic Disparities in Access to Lumbar Spinal Surgery When Compared to Commercial Insurance?

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: Compare disparities in lumbar surgical care utilization in Commercially insured versus Medicare patients. SUMMARY OF BACKGROUND DATA: While disparities in spinal surgery have been previously described, less evidence exists on effective strategies to mitigate them. Theoretically, universal health care coverage under Medicare should improve health care access. MATERIALS AND METHODS: Utilizing National Inpatient Sample data (2003-2018), we included inpatient lumbar discectomy or laminectomy/fusion cases in black, white, or Hispanic patients aged 18-74 years, with Commercial or Medicare insurance. A multivariable Poisson distribution model determined race/ethnicity subgroup-specific rate ratios (RRs) of patients undergoing lumbar surgery compared to their respective population distribution (using US Census data) based on race/ethnicity, region, gender, primary payor, and age (Commercially insured age subgroups: 18-39, 40-54, and 55-64 y; Medicare age subgroup: 65-74 y). RESULTS: Of the 2,310,956 lumbar spine procedures included, 88.9%, 6.1%, and 5.0% represented white, black, and Hispanic patients, respectively. Among Commercially insured patients, black and Hispanic (compared to white) patients had lower rates of surgical care utilization; however, these disparities decreased with increasing age: black (RR=0.37, 95% CI: 0.37-0.38) and Hispanic patients (RR=0.53, 95% CI: 0.52-0.54) aged 18-39 years versus black (RR=0.72, 95% CI: 0.71-0.73) and Hispanic patients (RR=0.64, 95% CI: 0.63-0.65) aged 55-64 years. Racial/ethnic disparities persisted in Medicare patients, especially when compared to the neighboring age subgroup that was Commercially insured: black (RR=0.61, 95% CI: 0.60-0.62) and Hispanic patients (RR=0.61, 95% CI: 0.60-0.61) under Medicare. CONCLUSIONS: Disparities in surgical care utilization among black and Hispanic patients persist regardless of health care coverage, and an expansion of Medicare eligibility alone may not comprehensively address health care disparities. LEVEL OF EVIDENCE: Level III.

Combining adhesive and nonadhesive injectable hydrogels for intervertebral disc repair in an ovine discectomy model.

Background: Intervertebral disc (IVD) disorders (e.g., herniation) directly contribute to back pain, which is a leading cause of global disability. Next-generation treatments for IVD herniation need advanced preclinical testing to evaluate their ability to repair large defects, prevent reherniation, and limit progressive degeneration. This study tested whether experimental, injectable, and nonbioactive biomaterials could slow IVD degeneration in an ovine discectomy model. Methods: Ten skeletally mature sheep (4-5.5 years) experienced partial discectomy injury with cruciate-style annulus fibrosus (AF) defects and 0.1 g nucleus pulposus (NP) removal in the L1-L2, L2-L3, and L3-L4 lumbar IVDs. L4-L5 IVDs were Intact controls. IVD injury levels received: (1) no treatment (Injury), (2) poly (ethylene glycol) diacrylate (PEGDA), (3) genipin-crosslinked fibrin (FibGen), (4) carboxymethylcellulose-methylcellulose (C-MC), or (5) C-MC and FibGen (FibGen + C-MC). Animals healed for 12 weeks, then IVDs were assessed using computed tomography (CT), magnetic resonance (MR) imaging, and histopathology. Results: All repaired IVDs retained ~90% of their preoperative disc height and showed minor degenerative changes by Pfirrmann grading. All repairs had similar disc height loss and Pfirrmann grade as Injury IVDs. Adhesive AF sealants (i.e., PEGDA and FibGen) did not herniate, although repair caused local endplate (EP) changes and inflammation. NP repair biomaterials (i.e., C-MC) and combination repair (i.e., FibGen + C-MC) exhibited lower levels of degeneration, less EP damage, and less severe inflammation; however, C-MC showed signs of herniation via biomaterial expulsion. Conclusions: All repair IVDs were noninferior to Injury IVDs by IVD height loss and Pfirrmann grade. C-MC and FibGen + C-MC IVDs had the best outcomes, and may be appropriate for enhancement with bioactive factors (e.g., cells, growth factors, and miRNAs). Such bioactive factors appear to be necessary to prevent injury-induced IVD degeneration. Application of AF sealants alone (i.e., PEGDA and FibGen) resulted in EP damage and inflammation, particularly for PEGDA IVDs, suggesting further material refinements are needed.

Equity-Driven Implementation of Patient-Reported Outcome Measures in Musculoskeletal Care: Advancing Value for All.

ABSTRACT: The clinical use of patient-reported outcome measures (PROMs) in musculoskeletal care is expanding, encompassing both individual patient management and population-level applications. However, without thoughtful implementation, we risk introducing or exacerbating disparities in care processes or outcomes. We outline examples of opportunities, challenges, and priorities throughout PROM implementation to equitably advance value-based care at both the patient and population level. Balancing standardization with tailored strategies can enable the large-scale implementation of PROMs while optimizing care processes and outcomes for all patients.

Postoperative Opioid Use and Prescribing Patterns among Patients Undergoing Cervical Laminectomy with Instrumented Fusion versus Cervical Laminoplasty with Reconstruction.

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: To compare patterns in opioid usage and prescriptions between patients who undergo cervical laminectomy with instrumented fusion (LF) vs cervical laminoplasty with reconstruction (LP) within single surgeon and national database cohorts. METHODS: We identified patients with cervical myelopathy undergoing primary LF or LP in both a single-surgeon series cohort (2004-2018) and a nationally representative cohort drawn from the IBM® Marketscan® database (2014-2016). We recorded opioid usage within 6 months of surgery and identified differences in unadjusted opioid use rates between LF and LP patients. Multivariable logistic regression was used to evaluate the association between procedure type and postoperative opioid use. RESULTS: Without adjusting for covariates, LF patients had a higher rate of 6-month opioid use in the single-surgeon cohort (15.7% vs 5.1%, P = .02). After adjusting for covariates, LF patients had higher odds of 6-month postoperative opioid use (OR 2.8 [95% CI 1.0-7.7], P = .04). In the national cohort, without adjusting for covariates, there was no significant difference in 6-month opioid use between LF and LP patients. Even after adjusting for covariates, we found no significant difference in odds. CONCLUSIONS: Findings from a single-surgeon cohort reveal that LF is associated with a higher rate of 6-month opioid use than LP. This is at odds with findings from a national database cohort, which suggested that LP and LF patients have similar rates of opioid usage at 6-months postoperatively. To prevent overuse of narcotics, surgeons must consider the distinct pain requirements associated with different procedures even in treatment of the same condition.

Can a Spine Robot Be More Efficient and Less Expensive While Maintaining Accuracy?

BACKGROUND: Spinal surgical robots are in the early phases of development and adoption. These systems need to be easier to use, less costly, and more workflow-efficient. METHODS: A portable, operating room table-mounted spine robot and camera system are described. Accuracy and workflow efficiency were assessed in comparison to another commonly utilized spinal robotic system. RESULTS: For the surgical task of inserting 4 pedicle screws into 2 adjacent lumbar vertebrae, equivalent accuracy was seen with both systems. The new robotic system was more efficient in terms of total procedure time, system setup time, and screw planning to in-position time (p<0.05). CONCLUSIONS: Spinal robotic systems can be more efficient and less expensive while maintaining accuracy. CLINICAL RELEVANCE: Spinal robots are being increasingly utilized in clinical practice. Lowering the cost of these systems and increasing their workflow efficiency should help patients and spine surgeons alike.

Postoperative C5 Palsy Following Cervical Laminectomy With Instrumented Fusion Versus Cervical Laminoplasty With Reconstruction: Single Surgeon and National Inpatient Cohort Analyses.

STUDY DESIGN: This was a retrospective cohort study. OBJECTIVE: The objective of this study was to investigate whether cervical laminectomy with instrumented fusion (LF) and cervical laminoplasty with reconstruction (LP) are associated with different rates C5 palsy (C5P) at 1-month follow-up in a single surgeon and nationally representative cohort. SUMMARY OF BACKGROUND DATA: LF and LP both carry a well-known risk of nerve root injury that most commonly presents as C5P which can reduce patient satisfaction, patient function, and impede patient recovery. The procedure type that is more frequently associated with C5P remains largely unclear. METHODS: We identified patients undergoing primary LF or LP procedures for the treatment of cervical myelopathy in both a single-surgeon series cohort (2004-2018; Mount Sinai Hospital) and a nationally representative cohort drawn from the American College of Surgeons National Surgical Quality Improvement Program (NSQIP) database (2006-2017). For the single-surgeon cohort, C5P within 1 month of surgery was recorded. For the NSQIP cohort, peripheral nerve injury (PNI) within 1 month of surgery was recorded and used as a proxy for C5P. Postoperative complications including C5P were compared between cohorts. Multivariable logistic regression was used to evaluate the association between procedure type and postoperative C5P or PNI. RESULTS: Without adjusting for covariates, LF patients had a higher rate of 1-month C5P in the single-surgeon cohort (8% vs. 0%, P=0.01). An adjusted odds ratio could not be obtained due to the absence of C5P in the LP group. In the national cohort, LP patients had a significantly higher rate of 1-month PNI on unadjusted analysis (11% vs. 16%, P<0.001). After adjusting for covariates, we found no significant difference in odds of 1-month PNI between LF and LP (adjusted odds ratio=0.84, P=0.07). CONCLUSIONS: Overall, the single-surgeon series suggest that cervical LF is associated with significantly higher rates of postoperative C5P as compared with LP. These findings are not corroborated by nationally representative data, which showed no difference in PNI rates between LF and LP. A surgeon's training and experience likely contribute to which procedure has a higher propensity for a C5P as a complication. Regardless, both LF and LP patients should be closely monitored for new-onset C5P during follow-up visits. LEVEL OF EVIDENCE: Level III.

Accelerometry Data Delineate Phases of Recovery and Supplement Patient-Reported Outcome Measures Following Lumbar Laminectomy.

BACKGROUND: Patient-reported outcome measures (PROMs) are traditionally used to track recovery of patients after spine surgery. Wearable accelerometers have adjunctive value because of the continuous, granular, and objective data they provide. We conducted a prospective study of lumbar laminectomy patients to determine if time-series data from wearable accelerometers could delineate phases of recovery and compare accelerometry data to PROMs during recovery tracking. METHODS: Patients with lumbar stenosis for whom lumbar laminectomy was indicated were prospectively recruited. Subjects wore accelerometers that recorded their daily step counts from at least 1 week preoperatively to 6 months postoperatively. Subjects completed the Oswestry Disability Index and the 12-Item Short Form Health Survey preoperatively and at 2 weeks, 1 month, 3 months, and 6 months postoperatively. Daily aggregate median steps and individual visit-specific median steps were calculated. The Pruned Linear Exact Time method was used to segment aggregate median steps into distinct phases. Associations between visit-specific median steps and PROMs were identified using Spearman rank correlation. RESULTS: Segmentation analysis revealed 3 distinct postoperative phases: step counts rapidly increased for the first 40 days postoperatively (acute healing), then gained more slowly for the next 90 days (recovery), and finally plateaued at preoperative levels (stabilization). Visit-specific median steps were significantly correlated with PROMs throughout the postoperative period. PROMs significantly exceeded baseline at 6 months postoperatively, while step counts did not (all P < 0.05). CONCLUSIONS: Continuous data from accelerometers allowed for identification of 3 distinct stages of postoperative recovery after lumbar laminectomy. PROMs remain necessary to capture subjective elements of recovery.

Enhanced Recovery Components for Posterior Lumbar Spine Fusion: Harnessing National Data to Compare Protocols.

STUDY DESIGN: This was a retrospective cohort study. OBJECTIVE: The aim of this study was to assess the most commonly used components of enhanced recovery after surgery (ERAS) combinations and their relative effectiveness. SUMMARY OF BACKGROUND DATA: Data is lacking on use and effectiveness of various ERAS combinations which are increasingly used in spine surgery. MATERIALS AND METHODS: Posterior lumbar fusion cases were extracted from the Premier Healthcare claims database (2006-2016). Seven commonly included components in spine ERAS protocols were identified: (1) multimodal analgesia, (2) tranexamic acid, (3) antiemetics on the day of surgery, (4) early physical therapy, (5) no urinary catheter, (6) no patient-controlled analgesia, and (7) no wound drains. Outcomes were: length of stay, "any complication," blood transfusion, and hospitalization cost. Mixed-effects models measured associations between the most common ERAS combinations and outcomes, separately for 2006-2012 and 2013-2016. Odds ratios (ORs) and 95% confidence intervals (CIs) are reported. RESULTS: Among 97,419 (74%; 2006-2012) and 34,932 (26%; 2013-2016) cases ERAS component variations decreased over time. The most commonly used combinations included multimodal analgesia, antiemetics, early physical therapy, avoidance of a urinary catheter, patient-controlled analgesia and drains (10% n=9401 and 19% n=6635 in 2006-2012 and 2013-2016, respectively), and did not include tranexamic acid. Multivariable models revealed minor differences between ERAS combinations in terms of length of stay and costs. The most pronounced beneficial effects in 2006-2012 were seen for the second most commonly (compared with less often) used ERAS combination(s) in terms of blood transfusion (OR: 0.65; CI: 0.59-0.71) and "any complication" (OR: 0.73; CI: 0.66-0.80), both P<0.05. In 2013-2016 the third most commonly used ERAS combination showed the strongest effect: blood transfusion OR: 0.63; CI: 0.50-0.78, P<0.05. CONCLUSIONS: ERAS component variations decreased over time; maximum benefits were particularly seen in terms of transfusion and complication risk reduction. These findings may inform future ERAS utilization and clinical trials comparing various ERAS protocols.

Combining Expandable Interbody Cage Technology With a Minimally Invasive Technique to Harvest Iliac Crest Autograft Bone to Optimize Fusion Outcomes in Minimally Invasive Transforaminal Lumbar Interbody Fusion Surgery.

STUDY DESIGN: This was a retrospective cohort review. OBJECTIVE: The objective of this study was to determine the rate of fusion associated with an expandable cage and iliac crest bone graft in minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) surgery. SUMMARY OF BACKGROUND DATA: MI-TLIF is a commonly performed procedure, but challenges inherent in MI-TLIF technique can make achieving an interbody fusion difficult. METHODS: A retrospective review was performed on consecutive patients treated with an MI-TLIF for degenerative lumbar pathology. Patients that completed patient-reported outcome measures and 1-year computed tomography (CT)-scans for fusion analysis were included. Fusion morphology was analyzed by evaluating CT scans for location of bridging trabecular bone in relation to the cage. Patients with bridging bone were considered fused. Preoperative and postoperative health-related quality of life scores were compared. A Kolmogrov-Smirnoff test was used to determine normality of health-related outcome scores. A Friedman 2-way analysis of variance by ranks with pairwise comparisons to determine statistical significance of differences between the date of a follow-up examination and preoperative examination was done. RESULTS: Of 75 patients evaluated 23 patients were excluded due to loss to follow-up, adjacent segment degeneration, inability to obtain a CT scan, or reoperation for nonfusion related symptoms. Of 61 disk spaces that were included, 55 had bridging bone through the intervertebral cage, resulting in an overall fusion rate of 90.2%. There was a higher rate of fusion at L5-S1 as compared to L4-L5. There was mean improvement in patient-reported outcome measures for Oswestry Disability Index, Short Form-12 Physical Component Score, Visual Analog Scale Back/Leg pain, and Patient-Reported Outcome Measurement Information System Physical Function. There were no complications associated with iliac crest bone graft harvesting. CONCLUSION: Combining an expandable cage with iliac crest autograft bone harvested through a minimally invasive technique can allow for improved fusion rates without graft-site complications in MI-TLIF surgery.

Local insulin application has a dose-dependent effect on lumbar fusion in a rabbit model.

The purpose of this study was to determine if locally applied insulin has a dose-responsive effect on posterolateral lumbar fusion. Adult male New Zealand White rabbits underwent posterolateral intertransverse spinal fusions (PLFs) at L5-L6 using suboptimal amounts of autograft. Fusion sites were treated with collagen sponge soaked in saline (control, n = 11), or with insulin at low (5 or 10 units, n = 13), mid (20 units, n = 11), and high (40 units, n = 11) doses. Rabbits were euthanized at 6 weeks. The L5-L6 spine segment underwent manual palpation and radiographic evaluation performed by two fellowship trained spine surgeons blinded to treatment. Differences between groups were evaluated by analysis of variance on ranks followed by post-hoc Dunn's tests. Forty-three rabbits were euthanized at the planned 6 weeks endpoint, while three died or were euthanized prior to the endpoint. Radiographic evaluation found bilateral solid fusion in 10%, 31%, 60%, and 60% of the rabbits from the control and low, mid, and high-dose insulin-treated groups, respectively (p < 0.05). As per manual palpation, 7 of 10 rabbits in the mid-dose insulin group were fused as compared to 1 of 10 rabbits in the control group (p < 0.05). This study demonstrates that insulin enhanced the effectiveness of autograft to increase fusion success in the rabbit PLF model. The study indicates that insulin or insulin-mimetic compounds can be used to promote bone regeneration.

Surgical Outcomes for Upper Lumbar Disc Herniations: A Systematic Review and Meta-analysis.

STUDY DESIGN: Systematic review and meta-analysis. OBJECTIVE: To conduct a literature review on outcomes of discectomy for upper lumbar disc herniations (ULDH), estimate pooled rates of satisfactory outcomes, compare open laminectomy/microdiscectomy (OLM) versus minimally invasive surgical (MIS) techniques, and compare results of disc herniations at L1-3 versus L3-4. METHODS: A systematic review of articles reporting outcomes of nonfusion surgical treatment of L1-2, L2-3, and/or L3-4 disc herniations was performed. The inclusion and exclusion of studies was performed according to the latest version of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. RESULTS: A total of 20 articles were included in the quantitative meta-analysis. Pooled proportion of satisfactory outcome (95% CI) was 0.77 (0.70, 0.83) for MIS and 0.82 (0.78, 0.84) for OLM. There was no significant improvement with MIS techniques compared with standard OLM, odds ratio (OR) = 0.86, 95% CI (0.42, 1.74), P = .66. Separating results by levels revealed a trend of higher satisfaction with L3-4 versus L1-3 with OLM surgery, OR = 0.46, 95% CI (0.19, 1.12), P = .08. CONCLUSION: Our analysis reveals that discectomy for ULDH has an overall success rate of approximately 80% and has not improved with MIS. Discectomy for herniations at L3-4 trends toward better outcomes compared with L1-2 and L2-3, but was not significant.

Physician Decision-making in Return to Play After Cervical Spine Injury: A Descriptive Analysis of Survey Data.

OF BACKGROUND DATA: Cervical spine injuries commonly occur during athletic play, and such injuries carry significant risk for adverse sequelae if not properly managed. Although guidelines for managing return to play exist, adherence among spine surgeons has not been thoroughly examined. STUDY DESIGN: Prospective analysis of survey data collected from surgeon members of the Cervical Spine Research Society (CSRS) and the International Society for the Advancement of Spine Surgery (ISASS). OBJECTIVE: The objective of this study was to characterize consensus among spine surgeons regarding decision-making on return to competitive sports and level of impact following significant cervical spine injuries from real-life scenarios. MATERIALS AND METHODS: Return to play decisions for 15 clinical cervical spine injury scenarios were compared with current guidelines. Surgeon demographic information such as orthopedic board certification status and years in practice were also analyzed. Weighted kappa analysis was utilized to determine interrater reliability in survey responses. RESULTS: Survey respondents had a poor agreement with both Watkins and Torg guidelines (average weighted κ of 0.027 and 0.066, respectively). Additional kappa analysis of surgeon agreement regarding the "Types of Play" and "Level of Play" for return was still remained poor (Kendall W of 0.312 and 0.200, respectively). Responses were also significantly influenced by surgeon demographics. CONCLUSIONS: There is poor consensus among spine surgeons for return to play following cervical spine injury. These results support the concept that given the gravity of cervical spine injuries, a more standardized approach to decision-making regarding return to play after cervical spine injury is necessary.

Contained-Delivery Route and the Administration of Postoperative Steroids Following Anterior Cervical Spinal Fusion With Low-dose rhBMP-2 Reduces the Magnitude of Respiratory Compromise.

STUDY DESIGN: Retrospective chart review of patients who underwent anterior cervical discectomy and fusion (ACDF) using low-dose recombinant human bone morphogenic protein (rhBMP)-2. OBJECTIVE: Determine whether severity and incidence of respiratory complications after ACDF surgery are decreased when using a low-dose BMP-infused sponge within a constrained carrier and postoperative IV and oral steroids. SUMMARY OF BACKGROUND DATA: Many physicians avoid using BMP in anterior cervical spine fusions because of concern for an increased incidence of dysphagia, significant prevertebral swelling, and airway edema compromise. Pilot studies have shown that the local application of steroids may decrease the incidence of postoperative airway edema and dysphagia. We performed a retrospective study to evaluate the safety of immediate postoperative tapered steroid use following low-dose rhBMP-2 completely contained inside either an allograft or PEEK cage in reducing the severity and incidence of respiratory complications following ACDF. MATERIALS AND METHODS: Forty-seven patients between 33 and 74 years of age, undergoing 1-, 2-, 3-, or 4-level ACDFs augmented with a fraction of a small sponge of rhBMP-2 (0.525 mg/level) within an allograft or PEEK cage and prescribed IV and oral postoperative steroids between January 1, 2008 and November 1, 2016. The incidence of complications such as dyspnea, dysphagia, airway issues, edema ectopic bone osteolysis, radiculitis, and nonunion were collected using medical charts. Additional data regarding length of hospital stay and readmissions were also recorded. RESULTS: No life-threatening respiratory events, such as prolonged intubation, re-intubation, or readmission for labored breathing, were observed. No complications referable to steroids such as delayed healing, uncontrollable blood sugar, or diabetes were encountered in this series. CONCLUSIONS: This study provides evidence that a tapered dose of steroids and a contained delivery route significantly decreases postoperative respiratory compromise incidence and magnitude following anterior cervical spine fusion using low-dose rhBMP-2.

Development and validation of risk-adjustment models for elective, single-level posterior lumbar spinal fusions.

BACKGROUND: There is a paucity of literature examining the development and subsequent validation of risk-adjustment models that inform the trade-off between adequate risk-adjustment and data collection burden. We aimed to evaluate patient risk stratification by surgeons with the development and validation of risk-adjustment models for elective, single-level, posterior lumbar spinal fusions (PLSFs). METHODS: Patients undergoing PLSF from 2011-2014 were identified in the American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP). The derivation cohort included patients from 2011-2013, while the validation cohort included patients from 2014. Outcomes of interest were severe adverse events (SAEs) and unplanned readmission. Bivariate analysis of risk factors followed by a stepwise logistic regression model was used. Limited risk-adjustment models were created and analyzed by sequentially adding variables until the full model was reached. RESULTS: A total of 7,192 and 4,182 patients were included in our derivation and validation cohorts, respectively. Full model performance was similar for the derivation and validation cohorts in both 30-day SAEs (C-statistic =0.66 vs. 0.69) and 30-day unplanned readmission (C-statistic =0.62 vs. 0.65). All models demonstrated good calibration and fit (P≥0.58). Intraoperative variables, laboratory values, and comorbid conditions explained >75% of the variation in 30-day SAEs; ASA class, laboratory values, and comorbid conditions accounted for >80% of model risk prediction for 30-day unplanned readmission. Four variables for the 30-day SAE models (age, gender, ASA ≥3, operative time) and 3 variables for the 30-day unplanned readmission models (age, ASA ≥3, operative time) were sufficient to achieve a C-statistic within four percentage points of the full model. CONCLUSIONS: Risk-adjustment models for PLSF demonstrated acceptable calibration and discrimination using variables commonly found in health records and demonstrated only a limited set of variables were required to achieve an appropriate level of risk prediction.

Zinc has insulin-mimetic properties which enhance spinal fusion in a rat model.

BACKGROUND CONTEXT: Previous studies have found that insulin or insulin-like growth factor treatment can stimulate fracture healing in diabetic and normal animal models, and increase fusion rates in a rat spinal fusion model. Insulin-mimetic agents, such as zinc, have demonstrated antidiabetic effects in animal and human studies, and these agents that mimic the effects of insulin could produce the same beneficial effects on bone regeneration and spinal fusion. PURPOSE: The purpose of this study was to analyze the effects of locally applied zinc on spinal fusion in a rat model. STUDY DESIGN/SETTING: Institutional Animal Care and Use Committee-approved animal study using Sprague-Dawley rats was used as the study design. METHODS: Thirty Sprague-Dawley rats (450-500 g) underwent L4-L5 posterolateral lumbar fusion (PLF). After decortication and application of approximately 0.3 g of autograft per side, one of three pellets were added to each site: high-dose zinc calcium sulfate (ZnCaSO4), low-dose ZnCaSO4 (half of the high dose), or a control palmitic acid pellet (no Zn dose). Systemic blood glucose levels were measured 24 hours postoperatively. Rats were sacrificed after 8weeks and the PLFs analyzed qualitatively by manual palpation and radiograph review, and quantitatively by micro-computed tomography (CT) analysis of bone volume and trabecular thickness. Statistical analyses with p-values set at .05 were accomplished with analysis of variance, followed by posthoc tests for quantitative data, or Mann-Whitney rank tests for qualitative assessments. RESULTS: Compared with controls, the low-dose zinc group demonstrated a significantly higher manual palpation grade (p=.011), radiographic score (p=.045), and bone formation on micro-CT (172.9 mm(3) vs. 126.7 mm(3) for controls) (p<.01). The high-dose zinc also demonstrated a significantly higher radiographic score (p=.017) and bone formation on micro-CT (172.7 mm(3) vs. 126.7 mm(3)) (p<.01) versus controls, and was trending toward higher manual palpation scores (p=.058). CONCLUSIONS: This study demonstrates the potential benefit of a locally applied insulin-mimetic agent, such as zinc, in a rat lumbar fusion model. Previous studies have demonstrated the benefits of local insulin application in the same model, and it appears that zinc has similar effects.

Traumatic atlantoaxial dislocation with Hangman fracture.

BACKGROUND CONTEXT: Traumatic bilateral-atlantoaxial dislocations are rare injuries. Hangman fractures, conversely, represent 4% to 7% of all cervical fractures and frequently involve a combination C1-C2 fracture pattern. Presently, there is no report in the English literature of a traumatic C2-spondylolisthesis associated with a C1-C2 rotatory dislocation. This injury complex cannot be cataloged using current classification schemes and no established treatment recommendations exist. PURPOSE: To report a unique case of a Hangman fracture associated with bilateral C1-C2 rotatory-dislocation, which does not fit into existing classification systems, and discuss our treatment approach. STUDY DESIGN: A clinical case report and review of the literature. METHODS: Chart review and analysis of relevant literature. There were no study-specific conflicts of interest. RESULTS: A 26-year-old man sustained a traumatic C2-spondylolisthesis along with C1-C2 rotatory subluxation in an automobile collision. The patient was originally placed in a halo crown and vest and then taken for an open reduction and stabilization through a posterior approach for persistent C1-C2 subluxation. The patient is currently 16 months postoperative and back to work as a plumber. CONCLUSIONS: The injury complex encountered cannot be described using the available classification systems. Our treatment included initial stabilization with halo placement, followed by a posterior C1, C2, and C3 segmental reduction and fixation resulting in radiographic fusion and a good clinical outcome.

The effects of local insulin application to lumbar spinal fusions in a rat model.

BACKGROUND CONTEXT: The rates of pseudoarthrosis after a single-level spinal fusion have been reported up to 35%, and the agents that increase the rate of fusion have an important role in decreasing pseudoarthrosis after spinal fusion. Previous studies have analyzed the effects of local insulin application to an autograft in a rat segmental defect model. Defects treated with a time-released insulin implant had significantly more new bone formation and greater quality of bone compared with controls based on histology and histomorphometry. A time-released insulin implant may have similar effects when applied in a lumbar spinal fusion model. PURPOSE: This study analyzes the effects of a local time-released insulin implant applied to the fusion bed in a rat posterolateral lumbar spinal fusion model. Our hypothesis was twofold: first, a time-released insulin implant applied to the autograft bed in a rat posterolateral lumbar fusion will increase the rate of successful fusion and second, will alter the local environment of the fusion site by increasing the levels of local growth factors. STUDY DESIGN: Animal model (Institutional Animal Care and Use Committee approved) using 40 adult male Sprague-Dawley rats. METHODS: Forty skeletally mature Sprague-Dawley rats weighing approximately 500 g each underwent posterolateral intertransverse lumbar fusions with iliac crest autograft from L4 to L5 using a Wiltse-type approach. After exposure of the transverse processes and high-speed burr decortication, a Linplant (Linshin Canada, Inc., ON, Canada) consisting of 95% microrecrystalized palmitic acid and 5% bovine insulin (experimental group) or a sham implant consisting of only palmitic acid (control group) was implanted on the fusion bed with iliac crest autograft. As per the manufacturer, the Linplant has a release rate of 2 U/day for a minimum of 40 days. The transverse processes and autograft beds of 10 animals from the experimental and 10 from the control group were harvested at Day 4 and analyzed for growth factors. The remaining 20 spines were harvested at 8 weeks and underwent a radiographic examination, manual palpation, and microcomputed tomographic (micro-CT) examination. RESULTS: One of the 8-week control animals died on postoperative Day 1, likely due to anesthesia. In the groups sacrificed at Day 4, there was a significant increase in insulinlike growth factor-I (IGF-I) in the insulin treatment group compared with the controls (0.185 vs. 0.129; p=.001). No significant differences were demonstrated in the levels of transforming growth factor beta-1, platelet-derived growth factor-AB, and vascular endothelial growth factor between the groups (p=.461, .452, and .767 respectively). Based on the radiographs, 1 of 9 controls had a solid bilateral fusion mass, 2 of 9 had unilateral fusion mass, 3 of 9 had small fusion mass bilaterally, and 3 of 9 had graft resorption. The treatment group had solid bilateral fusion mass in 6 of 10 and unilateral fusion mass in 4 of 10, whereas a small bilateral fusion mass and graft resorption were not observed. The difference between the groups was significant (p=.0067). Based on manual palpation, only 1 of 9 controls was considered fused, 4 of 9 were partially fused, and 4 of 9 were not fused. In the treatment group, there were 6 of 10 fusions, 3 of 10 partial fusions, and 1 of 10 were not fused. The difference between the groups was significant (p=.0084). Based on the micro-CT, the mean bone volume of the control group was 126.7 mm(3) and 203.8 mm(3) in the insulin treatment group. The difference between the groups was significant (p=.0007). CONCLUSIONS: This study demonstrates the potential role of a time-released insulin implant as a bone graft enhancer using a rat posterolateral intertransverse lumbar fusion model. The insulin-treatment group had significantly higher fusion rates based on the radiographs and manual palpation and had significantly higher levels of IGF-I and significantly more bone volume on micro-CT.