Faculty Bibliography

STUDY DESIGN:Retrospective radiographic study. OBJECTIVE:The aim of this study was to compare disks with and without high-intensity zones (HIZ) to understand the impact of an HIZ on the stability of corresponding lumbar spinal segments. SUMMARY OF BACKGROUND DATA:Previous studies have established a relationship between back pain and the presence of HIZ on T2-weighted images of magnetic resonance imaging. These previous studies, however, used either plain radiographs or static (neutral position) magnetic resonance imaging to assess their chosen variables. MATERIALS AND METHODS:We retrospectively reviewed 140 consecutive patients with MR images taken in weight-bearing neutral, flexion, and extension positions. We separated segments into those with HIZ and without HIZ and assessed the grade of disk degeneration for each segment. Subsequently, a matched control group was selected from the segments without HIZ. Multiple factors were compared in a univariate analysis. A multinomial logistic regression analysis was conducted to assess the association between angular range of motion (ROM) >10 degrees and translational motion >2 mm with multiple independent variables. RESULTS:Upon assessment of the 700 lumbar segments, 70 (10%) segments had an HIZ and 68 patients had a single HIZ. On univariate analysis, the presence of an HIZ was not found to be significantly associated with degree of fatty muscle degeneration (P=0.969), muscle volume (P=0.646), degree of facet joint osteoarthritis (P=0.706), intervertebral disk height (P=0.077), Modic change (P=0.951), lower endplate shape (P=0.702), upper endplate shape (P=0.655), or degree of disk degeneration (P=0.607). Multifactorial analysis showed that none of the independent variables significantly correlated with angular ROM >10 degrees. For translational motion, the only significant correlation was the Goutallier classification (P=0.017). CONCLUSIONS:The presence of HIZ did not significantly affect spinal stability as measured by angular ROM and translational motion and was not associated with significant changes in several quantitative measurements of spine pathology.

LEVEL OF EVIDENCE/METHODS:3.

STUDY DESIGN/UNASSIGNED:Retrospective cross-sectional study. OBJECTIVES/UNASSIGNED:To determine if pre-operative albumin and CRP can predict post-operative infections after lumbar surgery. METHODS/UNASSIGNED:Patients who underwent an anterior lumbar interbody fusion (ALIF), posterior lumbar interbody fusion (PLIF), or lumbar discectomy were identified using a patient record database (PearlDiver) and were included in this retrospective study. Patients were stratified by Charlson Comorbidity Index (CCI) scores and pre-operative albumin and CRP status. Post-operative complications included deep infections and urinary tract infections within 3 months of the surgery and revisions within 1 year of the surgery. RESULTS/UNASSIGNED:74,280 patients were included in this study. 21,903 had pre-operative albumin or CRP lab values. 7,191 (33%), 12,183 (56%), and 2,529 (12%) patients underwent an ALIF, PLIF, and a lumbar discectomy, respectively. 16,191 did not have any complication (74%). The most common complication was UTI (16%). Among all patients, hypoalbuminemia was a significant risk factor for deep infection and UTI after ALIF, deep infection, UTI, and surgical revision after PLIF, and deep infection after lumbar discectomy. Elevated CRP was a significant risk factor for deep infection after ALIF, UTI after PLIF, and deep infection after lumbar discectomy in patients with a CCI ≤ 3. CONCLUSIONS/UNASSIGNED:Pre-operative hypoalbuminemia and elevated CRP were significant risk factors for deep infection, UTI, and/or revision, after ALIF, PLIT, and/or lumbar discectomy. Future studies with a larger population of patients with low albumin and high CRP values are needed to further elaborate on the current findings.

PURPOSE:To evaluate the effect of cervical sagittal alignment on craniocervical junction kinematic. METHODS:We retrospectively reviewed 359 patients (119 cervical lordosis, 38 cervical sagittal imbalances, 111 cervical straight, and 91 cervical kyphosis) who underwent cervical spine multi-positional magnetic resonance imaging (mMRI). The C2-7 angle, disc degeneration grading and cSVA were analyzed in neutral position. The C3-5 OCI, O-C2 angle, and OCD were analyzed in neutral, flexion, and extension position. The Kruskal-Wallis test was used to detect difference among four groups. The post hoc analysis was performed by Mann-Whitney U test. RESULTS:The cervical sagittal imbalance, cervical straight, and cervical kyphosis groups had significantly more lordosis angle in C3 and C4 OCI and O-C2 angle than the cervical lordosis group (p < 0.0125). Head motion in relation to C2, C3, and C4 (O-C2 angle, C3-4 OCI) in the kyphosis group was significantly greater than in the cervical lordosis group (p < 0.0125). The cervical sagittal imbalance group showed significantly increased O-C2 angle than the cervical lordosis group (p = 0.008). Regression analysis showed that an increase in O-C2 angle by one unit had a relative risk of 4.3% and 3.5% for a patient to be in the cervical sagittal imbalance and cervical kyphosis groups, respectively. CONCLUSIONS:Cervical sagittal alignment affected craniocervical junction motion with the head exhibiting greater extension and motion in the cervical sagittal imbalance and cervical kyphosis groups. Motion of the head in relation to C2 can be used to predict the cervical sagittal alignment.

BACKGROUND:Despite the extensive use of cellular bone matrices (CBMs) in spine surgery, there is little evidence to support the contribution of cells within CBMs to bone formation. The objective of this study was to determine the contribution of cells to spinal fusion by direct comparisons among viable CBMs, devitalized CBMs, and cell-free demineralized bone matrix (DBM). METHODS:Three commercially available grafts were tested: a CBM containing particulate DBM (CBM-particulate), a CBM containing DBM fibers (CBM-fiber), and a cell-free product with DBM fibers only (DBM-fiber). CBMs were used in viable states (CBM-particulatev and CBM-fiberv) and devitalized (lyophilized) states (CBM-particulated and CBM-fiberd), resulting in 5 groups. Viable cell counts and bone morphogenetic protein-2 (BMP-2) content on enzyme-linked immunosorbent assay (ELISA) within each graft material were measured. A single-level posterolateral lumbar fusion was performed on 45 athymic rats with 3 lots of each product implanted into 9 animals per group. After 6 weeks, fusion was assessed using manual palpation, micro-computed tomography (μ-CT), and histological analysis. RESULTS:The 2 groups with viable cells were comparable with respect to cell counts, and pairwise comparisons showed no significant differences in BMP-2 content across the 5 groups. Manual palpation demonstrated fusion rates of 9 of 9 in the DBM-fiber specimens, 9 of 9 in the CBM-fiberd specimens, 8 of 9 in the CBM-fiberv specimens, and 0 of 9 in both CBM-particulate groups. The μ-CT maturity grade was significantly higher in the DBM-fiber group (2.78 ± 0.55) compared with the other groups (p < 0.0001), while none of the CBM-particulate samples demonstrated intertransverse fusion in qualitative assessments. The viable and devitalized samples in each CBM group were comparable with regard to fusion rates, bone volume fraction, μ-CT maturity grade, and histological features. CONCLUSIONS:The cellular component of 2 commercially available CBMs yielded no additional benefits in terms of spinal fusion. Meanwhile, the groups with a fiber-based DBM demonstrated significantly higher fusion outcomes compared with the CBM groups with particulate DBM, indicating that the DBM component is probably the key determinant of fusion. CLINICAL RELEVANCE/CONCLUSIONS:Data from the current study demonstrate that cells yielded no additional benefit in spinal fusion and emphasize the need for well-designed clinical studies on cellular graft materials.

PURPOSE:To evaluate the reliability and validity of the multi-positional magnetic resonance imaging in measuring occipitocervical parameters using the standard cervical dynamic radiographs as a reference. METHODS:Patients were included if they underwent both dynamic radiograph and cervical multi-positional MRI within a 2-week interval from January 2013 to December 2016. Twelve occipitocervical parameters were measured on both image modalities in all positions (neutral, flexion and extension): Posterior Atlanto-Dental Interval, Anterior Atlanto-Dental Interval (AADI), Dens-to-McRae distance, Dens-to-McGregor distance, Occipito-atlantal Cobb angle (C01 angle), Occipito-axis Cobb angle (C02 Cobb angle), Atlas-axis Cobb angle (C12 angle), Redlund-Johnell, Modified Ranawat, Clivus canal angle, Occiput inclination, and Occiput cervical distance. Pearson correlation and linear regression analysis were used to evaluate the correlation of both modalities for each parameter. A p value of < 0.05 was considered statistically significant. RESULTS:Cervical images of 70 patients were measured and analyzed. There was a significant positive correlation between dynamic X-ray and multi-positional MRI for all parameters (p < 0.05) except AADI. Dens-to-McGregor distance and Redlund-Johnell parameter demonstrated a very strong correlation in the neutral position (r = 0.72, r = 0.79 respectively) and moderate to very strong correlation(r > 0.4) for Modified Ranawat, Clivus canal angle, C02 Cobb angle and C02 distance in all neck position. The intra-class correlation (ICC) of intra- and inter-observer showed good to excellent reliability, and ICCs were 0.67-0.98. CONCLUSIONS:Multi-positional MRI can be a reliable imaging option for diagnosis of occipitocervical instability or basilar invagination compared to standard dynamic radiographs.

STUDY DESIGN/METHODS:Retrospective database study. OBJECTIVE:To assess the intra- and postoperative complications of cervical laminoplasty and to evaluate the effect of intraoperative neuromonitoring use on postoperative limb paralysis incidence. SUMMARY OF BACKGROUND DATA/BACKGROUND:Cervical laminoplasty is a known procedure for the management of cervical spondylotic myelopathy (CSM). METHODS:This was a retrospective study of 532 patients with CSM who underwent cervical laminoplasty between 2007 and the first quarter of 2016 using the Humana subset of the PearlDiver Database. The database was queried using the relevant International Classification of Diseases (ICD-9 and ICD-10) codes for CSM and Current Procedural Terminology (CPT) codes for cervical laminoplasty. The intra- and postoperative incidence of surgical and medical complications and reoperations was then determined and was compared with a propensity score-matched cohort of patients who had posterior laminectomy and fusion (490 patients in each group), using multivariate logistic regression analysis. RESULTS:Laminoplasty was associated with a lower incidence of dysphagia (odds ratio [OR] = 0.37, 95% confidence interval [CI] = 0.16-0.79; P = 0.014), 30-day readmission (OR = 0.51, 95% CI = 0.35-0.75; P < 0.001), urinary tract infection (OR = 0.58, 95% CI = 0.37-0.93; P = 0.023), and incision and drainage, exploration or evacuation (OR = 0.28, 95% CI = 0.08-0.79; P = 0.026). The use of intraoperative neuromonitoring was associated with a non-significant lower incidence of limb paralysis within 1 and 3 months postoperatively (OR = 0.52 and 0.51, 95% CI = 0.23-1.19 and 0.23-1.11; P = 0.119 and 0.091, respectively). CONCLUSION/CONCLUSIONS:Compared with posterior laminectomy and fusion, laminoplasty had lower rates of dysphagia, urinary tract infection, and 30-day readmission. The use of intraoperative neuromonitoring was associated with a lower risk of postoperative limb paralysis, but it did not achieve statistical significance. LEVEL OF EVIDENCE/METHODS:4.

STUDY DESIGN/UNASSIGNED:Classification development. OBJECTIVES/UNASSIGNED:The aim of our study was to develop a 3-tier classification for the levels of evidence for osteobiologics and provide a description of the principles by which osteobiologics can be evaluated. BOnE (Bone Osteobiologics and Evidence) classification evaluates each osteobiologic based on the available evidence, and if the published evidence is based on clinical, in vivo or in vitro studies. METHODS/UNASSIGNED:The process of establishing the BOnE classification included 5 face-to-face meetings and 2 web calls among members of the AOSpine Knowledge Forum Degenerative. RESULTS/UNASSIGNED:The 3 levels of evidence were determined based on the type of data on osteobiologics: level A for human studies, level B for animal studies, and level C for in vitro studies, with level A being the highest level of evidence. Each level was organized into 4 subgroups (eg, A1, A2, A3, and A4). CONCLUSIONS/UNASSIGNED:The use and the variety of osteobiologics for spine fusion has dramatically increased over the past few decades; however, literature on their effectiveness is inconclusive. Several prior systematic reviews developed by AOSpine Knowledge Forum Degenerative reported low level of evidence primarily due to the high risk of bias, small sample size, lack of control groups, and limited patient-reported outcomes. BOnE classification will provide a universal platform for research studies and journal publications to classify a new or an existing product and will allow for creating decision-making algorithms for surgical planning.

STUDY DESIGN/METHODS:Retrospective review of insurance database. PURPOSE/OBJECTIVE:To investigate national trends, complications, and costs after cervical disc replacement (CDR) using an administrative insurance database representative of the United States population. OVERVIEW OF LITERATURE/BACKGROUND:As CDR continues to be used to treat patients with cervical stenosis, it is important to gain a better understanding of its use on a national level, potential complications, and cost. This information will allow for optimal patient counseling, risk stratification, and healthcare cost assessments. Several prior studies have investigated complications associated with CDR, but they have been limited by small sample size, single institution experiences, limited follow-up, and potential conflicts of interest. METHODS:Patients who underwent single or multilevel CDR between 2007 and 2015 were identified using an insurance database. We collected data on annual trends, reimbursement costs, patient demographic information, hospital information, and information on complications from the time of operation to 1 year postoperative. RESULTS:Total of 293 patients underwent either single or multilevel CDR. The number of procedures increased nonlinearly over time at an average of 17% per year, with a greater increase seen in the outpatient setting. Less than 3.7% of patients had new onset pain within 1 year after CDR. Within 1 year, 12.3% of patients reported a mechanical and/or bone-related complication. There were no patients who indicated a new nerve injury within 6 months of follow-up. Less than 3.7% of patients presented with dysphagia or dysphonia within 6 months, infection within 3 months, or a revision or reoperation within 1 year. Average reimbursement for single-level inpatient versus outpatient CDR was US $33,696.28 and US $34,675.12, respectively (p=0.29). CONCLUSIONS:This study demonstrated that the use of CDR continued to increase. The most common complication was mechanical and/or bone-related, and cost analysis demonstrated no significant difference between inpatient and outpatient CDR.