A Retrieval Analysis of Impingement in Dual-Mobility Liners.

BACKGROUND: Implant-related impingement is likely a major causative factor of total hip arthroplasty (THA) instability. Dual-mobility (DM) cups can theoretically improve stability in THA, but impingement rates with DM cups are not well studied. We examined retrieved DM THA liners to determine if less evidence existed for prosthetic impingement between the neck and the polyethylene liner than historical studies from our institution on fixed-bearing THAs. METHODS: DM components from 93 THAs were identified from 164 THAs whose DM components were revised between 2008 and 2015 through our institutional review board-approved implant retrieval program. The mean age was 63 ± 11 years, mean body mass index was 30 ± 7 kg/m2, and mean length of implantation was 2.08 ± 1.89 years. Two independent graders scored each liner for the presence and severity of impingement. Radiographs were evaluated for inclination, anteversion, change in leg length, and combined offset. RESULTS: Only 21.5% (20/93) of DM cups showed evidence of impingement compared to 77% (75/97) of fixed-bearing cups found in a previous study performed at our institution (P < .001). Of the revision components, 35.2% (5/14) demonstrated evidence of impingement compared to 19.7% (14/71) implanted in primary surgery (P = .189). In the cohort revised for instability, the rate of impingement was 35.3% (6/17); for the implants revised for any other reason, the impingement rate was 18.4% (14/77) (P = .126). CONCLUSION: This study demonstrates that DM liners significantly reduce the rate of impingement (21.5%) when compared to fixed-bearing liners (77%).

Missed cervical disc bulges diagnosed with kinematic magnetic resonance imaging.

PURPOSE: To determine if adding flexion and extension MRI studies to the traditional neutral views would be beneficial in the diagnosis of cervical disc bulges. METHODS: Five hundred patients underwent MRI in neutral, flexion and extension positions. The images were analyzed using computer software to objectively quantify the amount of disc bulge. RESULTS: Compared to the neutral position, cervical disc bulges were significantly increased in the extension position (P < 0.05), but on flexion position, there was no significant difference (P > 0.05). For patients without or <3 mm of disc bulge in neutral, 2.97% demonstrated an increase in bulge to ≥3 mm bulge in flexion, and 16.41% demonstrated an increase to ≥3 mm bulge in extension. For patients in the neutral view that had a baseline disc bulge of 3-5 mm, 3.73% had increased bulges to ≥5 mm in flexion and 11.57% had increased bulges to ≥5 mm in extension. CONCLUSION: A significant increase in the degree of cervical disc bulge was found by examining extension views when compared with neutral views alone. Kinematic MRI views provide valuable added information, especially in situations where symptomatic radiculopathy is present without any abnormalities demonstrated on traditional neutral MRI.

Patterns of Lumbar Disc Degeneration: Magnetic Resonance Imaging Analysis in Symptomatic Subjects.

STUDY DESIGN: Cross-sectional study. PURPOSE: To evaluate lumbar disc degeneration (LDD) on magnetic resonance imaging (MRI) in symptomatic subjects to accumulate baseline data on the pattern of degeneration. OVERVIEW OF LITERATURE: LDD plays an important role in the diagnosis and treatment of low-back pain in patients. Few studies have focused on the pattern of LDD to understand how the lumbar spine ages. METHODS: This study included 1,095 patients (mean age, 44.29 years; range, 16-85 years) who underwent upright lumbar MRI. LDD was graded into five categories (I-V). Positive LDD was defined as grade III or greater. The prevalence and pattern of LDD were analyzed, and the correlations between age and total grade of LDD were evaluated. RESULTS: The average number of LDD levels and the total grade of LDD increased with age. LDD moved cephalad with age. The rate of LDD increased rapidly during the decade before the prevalence of LDD and became >50%. In the single-level LDD group, the levels L5-S1 were the most common levels (60.3%). In the two-level group, L4-L5 and L5-S1 were the most common levels (53.5%). In the three-level group, L3-L4, L4-L5, and L5-S1 were the most common levels (55.7%). In the multilevel LDD group, contiguous multilevel disc degeneration (CMDD) was more common than the skipped level disc degeneration (SLDD). The levels L4-L5 were the most common levels in the CMDD group, and L5-S1 were the most common levels among SLDD. CONCLUSIONS: LDD was found to correlate with age, and the specific patterns and rates of LDD depended on lumbar disc level and age. These LDD pattern data can be used before spinal procedures to predict the probability of natural LDD progression with age.

Patterns of Cervical Disc Degeneration: Analysis of Magnetic Resonance Imaging of Over 1000 Symptomatic Subjects.

STUDY DESIGN: Cross-sectional study. OBJECTIVES: The aim of this study was to evaluate cervical disc degeneration on magnetic resonance imaging (MRI) in a large population of symptomatic patients and to provide baseline data on the pattern of degeneration in order to understand how the cervical spine ages. METHODS: We performed a cross-sectional study of 1059 patients who underwent upright cervical MRI for neck pain with and without neurological symptoms. A total of 6354 cervical discs from C2/3 to C7/T1 were evaluated. Cervical disc degeneration was evaluated on T2-weighted MRI and graded into 4 categories (Grades 0-III). Positive degeneration was defined as greater than Grade II. The correlation between age and total grade of degeneration of each patient was evaluated, as well as the prevalence and pattern of degeneration. RESULTS: The average number of degenerated disc levels and the total grade of cervical disc degeneration significantly increase with age. In the patient group with 1-level degeneration, C5/6 was the most common degenerated level followed by C4/5 and C6/7. In the group with 2-level degeneration, C5/6 & C6/7 was most common followed by C4/5 & C5/6 and C3/4 & C4/5. Skip level degeneration was significantly rarer than contiguous level degeneration, and C7/T1 and C2/3 were the most unlikely to degenerate in multilevel degeneration. CONCLUSION: Disc degeneration is most common in the middle cervical spine (C5/6) and progresses to contiguous levels, except for C7/T1 and C2/3. This pattern may play a role in adjacent-level disc degeneration associated with spinal fusion.

Magnetic Resonance Classification System of Cervical Intervertebral Disk Degeneration: Its Validity and Meaning.

STUDY DESIGN: Retrospective analysis of kinetic magnetic resonance images (kMRIs). OBJECTIVE: (1) To analyze the changes seen on MRI related to disk degeneration and to develop a new grading system for cervical disk degeneration. (2) To evaluate the reliability and validity of the grading system. SUMMARY OF BACKGROUND DATA: Few have studied the relationship between changes seen on MRI with cervical disk degeneration and the chronological order of disk degeneration. A few grading systems for cervical disk degeneration have been reported; however, there have been problems related to subjectivity and lack of a clear, reliable algorithm. METHODS: A total of 300 cervical intervertebral disks were graded for nucleus color, structure, disk bulge, and disk height. On the basis of the analysis, a new grading system consisting of 4 grades (grade 0-III) and algorithm were developed. Intraobserver and interobserver reliabilities were assessed. A total of 2802 intervertebral disks were then evaluated using the grading system to correlate disk degeneration grades with patient age and function and to evaluate the validity of the new system. RESULTS: On the basis of cross-table analysis, disk degeneration presents in the following order: (1) decrease and/or change of nucleus intensity; (2) loss of distinction between nucleus and annulus; (3) positive disk bulge; and (4) disk height decrease. The κ-coefficients for intraobserver and interobserver agreements were 0.96 and 0.90, respectively. Severe disk degeneration is most common at C5/C6 followed by C6/C7 and C4/C5, and total disk degeneration grade is correlated with age (R=0.467). There was a decrease of angular motion in grades I-III and an increase in translational motion and decrease of space available for the cord in grades II-III. CONCLUSIONS: We developed a new classification system of cervical disk degeneration based on analysis of the changes seen on MRI. Reliability tests indicated high reproducibility of this system, and further analysis confirmed its validity and clinical significance.

Dynamic Evaluation of the Cervical Spine and the Spinal Cord of Symptomatic Patients Using a Kinetic Magnetic Resonance Imaging Technique.

PURPOSE: The purpose of this study was to examine the movement of the spinal cord and its relationship to the spinal canal in patients with mild spondylosis using kinetic magnetic resonance imaging (kMRI). METHODS: Weight-bearing, multiposition kMRI was performed on symptomatic patients through a full range of flexion-extension. A total of 52 study patients were selected based on the C2-C7 Cobb angle of sagittal alignment: lordotic (from 30 to 45 degrees). We evaluated dynamic changes in different parameters from flexion-extension: spinal canal diameter (CD), spinal cord diameter (SCD), space available for the cord, anterior space available for the cord (ASAC), posterior space available for the cord (PSAC), average distance between the anterior canal and the cord (d-value), and global angle for the spinal canal and cord. RESULTS: The CD tended to decrease from flexion to extension from C3/C4 to C6/C7, however, there were no significant differences at the proximal and distal levels, C2/C3 and C7/T1. There were no significant differences of SCD between different postures. The SCD tended to decrease from C2/C3 to C7/T1. The ASAC followed the same pattern as CD-values. The ASAC was narrowest at C4/C5 and C5/C6. The PSAC tended to increase from C2/C3 to C7/T1. The spinal cord shifted anteriorly with extension and posteriorly with flexion. In addition, the spinal cord maintained its curve with the movement. CONCLUSIONS: The kinematics of spinal cord motion may be associated with the pathogenesis of cervical spondylotic myelopathy. However, the spinal cord maintains its curve with position changes. Consequently, different motions of the cervical spine may affect spinal cord migration and cause changes in ASAC and PSAC.

The Compensatory Relationship of Upper and Subaxial Cervical Motion in the Presence of Cervical Spondylosis.

STUDY DESIGN: This study was an in vivo kinematic magnetic resonance imaging analysis of cervical spinal motion in human subjects. OBJECTIVE: The objective of the study was to identify associations between disk degeneration in the subaxial cervical spine and upper cervical spinal motion in patients with general age-related cervical spondylosis. SUMMARY OF BACKGROUND DATA: The kinematic relationship between the occipital-atlantoaxial complex and subaxial cervical spine in patients with cervical spondylosis and decreased cervical motion is not well understood. METHODS: A total of 446 symptomatic patients who had neck pain with and without neurogenic symptoms were included in this study. Kinematic magnetic resonance imaging was performed with dynamic motion of the cervical spine in upright, weight-bearing neutral, flexion, and extension positions. Intervertebral disk degeneration for each segment from C2-3 to C7-T1 and sagittal angular motion between flexion and extension for each segment from Oc-C1 to C7-T1 was evaluated. Depending on the amount of sagittal subaxial angular motion, the patients were classified into 3 groups by sagittal angular motion using cutoff points based on tertile (<36-degree group: 149 cases; 36-47-degree group: 148 cases; and >47-degree group: 149 cases). RESULTS: A significant correlation was found between subaxial angular motion and intervertebral disk degeneration, indicating that the subaxial motion decreases according to the degree of disk degeneration. Mean angular motion of the occipital-atlantoaxial complex, especially of Oc-C1, was significantly higher in the <36-degree and 36-47-degree group than in the >47-degree group, whereas no significant difference was found at C1-C2. CONCLUSIONS: Our study demonstrates that decreased subaxial cervical spinal motion is associated with intervertebral disk degeneration in a symptomatic population. This decrease in mobility at the subaxial cervical spine is compensated for by an increase in angular mobility of the upper cervical spine at the occipital-atlantoaxial complex, especially at Oc-C1.

A comparison of commercially available demineralized bone matrices with and without human mesenchymal stem cells in a rodent spinal fusion model.

OBJECTIVE The efficacy of some demineralized bone matrix (DBM) substances has been demonstrated in the spinal fusion of rats; however, no previous comparative study has reported the efficacy of DBM with human mesenchymal stem cells (hMSCs). There is an added cost to the products with stem cells, which should be justified by improved osteogenic potential. The purpose of this study is to prospectively compare the fusion rates of 3 different commercially available DBM substances, both with and without hMSCs. METHODS Posterolateral fusion was performed in 32 mature athymic nude rats. Three groups of 8 rats were implanted with 1 of 3 DBMs: Trinity Evolution (DBM with stem cells), Grafton (DBM without stem cells), or DBX (DBM without stem cells). A fourth group with no implanted material was used as a control group. Radiographs were obtained at 2, 4, and 8 weeks. The rats were euthanized at 8 weeks. Overall fusion was determined by manual palpation and micro-CT. RESULTS The fusion rates at 8 weeks on the radiographs for Trinity Evolution, Grafton, and DBX were 8 of 8 rats, 3 of 8 rats, and 5 of 8 rats, respectively. A significant difference was found between Trinity Evolution and Grafton (p = 0.01). The overall fusion rates as determined by micro-CT and manual palpation for Trinity Evolution, Grafton, and DBX were 4 of 8 rats, 3 of 8 rats, and 3 of 8 rats, respectively. The Trinity Evolution substance had the highest overall fusion rate, however no significant difference was found between groups. CONCLUSIONS The efficacies of these DBM substances are demonstrated; however, the advantage of DBM with hMSCs could not be found in terms of posterolateral fusion. When evaluating spinal fusion using DBM substances, CT analysis is necessary in order to not overestimate fusion.

Growth-Factor Nanocapsules That Enable Tunable Controlled Release for Bone Regeneration.

Growth factors are of great potential in regenerative medicine. However, their clinical applications are largely limited by the short in vivo half-lives and the narrow therapeutic window. Thus, a robust controlled release system remains an unmet medical need for growth-factor-based therapies. In this research, a nanoscale controlled release system (degradable protein nanocapsule) is established via in situ polymerization on growth factor. The release rate can be finely tuned by engineering the surface polymer composition. Improved therapeutic outcomes can be achieved with growth factor nanocapsules, as illustrated in spinal cord fusion mediated by bone morphogenetic protein-2 nanocapsules.

Kinematic analysis of diseased and adjacent segments in degenerative lumbar spondylolisthesis.

BACKGROUND CONTEXT: Degenerative spondylolisthesis is a common pathologic condition that leads to lumbar instability and significant clinical symptoms. The effect of this pathology on adjacent lumbar motion segments, however, has not yet been studied. PURPOSE: To characterize the motion characteristics of lumbar degenerative spondylolisthesis at both the diseased and adjacent levels in patients with low-grade, single-level lumbar degenerative spondylolisthesis using kinetic magnetic resonance imaging (kMRI). STUDY DESIGN: Retrospective study of patient kMRIs. PATIENT SAMPLE: One-hundred twelve patient MRIs with low-grade, single-level lumbar spondylolisthesis were included. OUTCOME MEASURES: Angular and translational motion. METHODS: This study compared 112 patients diagnosed with low-grade (Grade 1 or 2), single-level lumbar degenerative spondylolisthesis at L3-L4, L4-L5, or L5-S1 with 296 control patients without spondylolisthesis. Angular and translational motion were measured using patient kMRIs. The level of slip was graded according to the Meyerding classification system, and disc degeneration was classified according to the Pfirrmann system. Instability was defined as translational motion greater than 4 mm. RESULTS: Lumbar hypomobility was often present regardless of the level of degenerative spondylolisthesis. A slip at L3-L4 resulted in the largest decrease in lumbar range of motion. Instability at the diseased level was most common at L3-L4 (36%), followed by L5-S1 (31%) and L4-L5 (30%). Instability at the adjacent segments was most frequent at L4-L5 (49%), followed by L5-S1 (34%) and L3-L4 (23%). Patients with stable spondylolisthesis generally had decreased angular motion at all lumbar levels. Translational motion at the diseased level was consistently increased. Disc degeneration was significantly greater at the level of slip for the L3-L4 and L4-L5 spondylolisthesis groups and equal to the control group in the L5-S1 group. There was no significant difference in disc degeneration at adjacent segments in L3-L4 and L4-L5 degenerative spondylolisthesis patients, but there was a significant decrease with an L5-S1 slip. CONCLUSIONS: There were a similar percentage of patients in each degenerative spondylolisthesis group with lumbar instability. Angular motion decreased at the diseased level with L3-L4 and L5-S1 spondylolisthesis, but increased with L4-L5 spondylolisthesis. Translational motion, however, increased at the diseased level in all three groups. There was compensatory hypermobility at adjacent levels in patients with unstable spondylolisthesis at L3-L4 and L4-L5, but not at L5-S1.

Trends in the surgical treatment of lumbar spine disease in the United States.

BACKGROUND CONTEXT: There is a lack of agreement among spine surgeons as to the best surgical treatment modality for many degenerative lumbar diseases. Although there are many studies examining trends in spinal surgery, specific studies reporting the variations in surgical treatment in the United States for these diseases are lacking. PURPOSE: The aim of this study was to analyze trends in lumbar spinal fusion methods for common lumbar pathologies in the United States. STUDY DESIGN/SETTING: National insurance database review: 2004-2009. PATIENT SAMPLE: Data is taken from United Healthcare and represents more than 25 million patients. OUTCOME MEASURES: No outcomes were measured in this study. METHODS: Using a private insurance database, we identified patients who underwent one of five types of instrumented single-level lumbar spinal fusion for the 10 most common primary diagnoses. Surgery rates were reviewed from 2004 to 2009 and were stratified according to patient age, patient gender, and region in the United States. Poisson regression analysis was performed to determine regional and demographic differences in treatment modality. The authors received no funds in support of this work. RESULTS: A total of 23,986 patients met our search criteria. Of the five fusion types, posterior lumbar interbody fusion (PLIF) with posterolateral fusion (PLF) was the most common (45%), followed by PLF (19%), anterior lumbar interbody fusion (ALIF, 16%), PLIF (10%), and ALIF with PLF (9%). There was a significant increase in PLIF with PLF (p<.0001), PLIF (p<.0001), PLF (p=.012), ALIF (p<.0001), and ALIF with PLF (p<.0001) from 2004 to 2009. After controlling for gender, there were significant differences between regions for all fusion types (p<.0001). The likelihood of a posterior fusion increased with age. Anterior fusions were more common in the 30- to 49-year-old age range than in patents older than 50. For patients in age groups older than 30, there was an increased number who underwent a circumferential fusion or an ALIF (p<.022). Fusion types were significantly different between genders (p<.026). Both genders had an overall increase in the number of fusions (p<.001) over the time period studied. CONCLUSIONS: There are large differences in the United States for surgical treatment methods for lumbar spine pathology. These differences are likely multifactorial, with both patient and surgeon traits playing a role. Illustrating these differences will hopefully lead to outcomes research to determine the indications, efficacy, and appropriateness of these surgical methods, an important step on the path toward standardization of care.

When Is It Safe to Return to Driving After Spinal Surgery?

Study Design Prospective study. Objective Surgeons' recommendations for a safe return to driving following cervical and lumbar surgery vary and are based on empirical data. Driver reaction time (DRT) is an objective measure of the ability to drive safely. There are limited data about the effect of cervical and lumbar surgery on DRT. The purpose of our study was to use the DRT to determine when the patients undergoing a spinal surgery may safely return to driving. Methods We tested 37 patients' DRT using computer software. Twenty-three patients (mean 50.5 ± 17.7 years) received lumbar surgery, and 14 patients had cervical surgery (mean 56.7 ± 10.9 years). Patients were compared with 14 healthy male controls (mean 32 ± 5.19 years). The patients having cervical surgery were subdivided into the anterior versus posterior approach and myelopathic versus nonmyelopathic groups. Patients having lumbar spinal surgery were subdivided by decompression versus fusion with or without decompression and single-level versus multilevel surgery. The patients were tested preoperatively and at 2 to 3, 6, and 12 weeks following the surgery. The use of opioids was noted. Results Overall, the patients having cervical and lumbar surgery showed no significant differences between pre- and postoperative DRT (cervical p = 0.49, lumbar p = 0.196). Only the patients having single-level procedures had a significant improvement from a preoperative DRT of 0.951 seconds (standard deviation 0.255) to 0.794 seconds (standard deviation 0.152) at 2 to 3 weeks (p = 0.012). None of the other subgroups had a difference in the DRT. Conclusions Based on these findings, it may be acceptable to allow patients having a single-level lumbar fusion who are not taking opioids to return to driving as early as 2 weeks following the spinal surgery.

Effect of disc degeneration on lumbar segmental mobility analyzed by kinetic magnetic resonance imaging.

STUDY DESIGN: Retrospective radiographical study. OBJECTIVE: To define the relationship between the grade of disc degeneration and the motion of the lumbar spine by using kinetic magnetic resonance imaging. SUMMARY OF BACKGROUND DATA: Disc degeneration is common after middle age. Lumbar instability has generally been recognized as a potential risk factor of low back pain. However, correlations between the grade of disc degeneration and the motion of the lumbar spine need more investigation. METHODS: Kinetic magnetic resonance imaging was performed in 162 patients with symptomatic low back pain without prior history of surgery. The lumbar intervertebral discs were graded by spine surgeons according to the degenerative grading system (grades I-V). Translational motion and angular variation were measured at each segment from L1-L2 through L5-S1. The relationship between the degree of lumbar disc degeneration and extent of lumbar spine mobility was analyzed. RESULTS: The translational motion in discs with grade I through IV increased gradually, but decreased with grade V. Compared with other less degenerative grades, grade V discs had significantly decreased total intervertebral translational motion (P < 0.05). The angular variation in discs with grade I through IV was fairly constant, but decreased with grade V. Compared with other degenerative grades (I-IV), grade V discs had significantly decreased total intervertebral translational motion (P < 0.05). For less degenerative grades I and II discs, the L2-L3 and L3-L4 segmental units contributed the majority of total angular mobility of the spine. However, for the severely degenerated segments, grade V discs, the contributions of the L2-L3 and L3-L4 significantly decreased (P < 0.01). CONCLUSION: As disc degeneration developed from the normal to an increasingly severe stage, the motion of lumbar spine progressed from the normal stage to an unstable phase with higher mobility and finally to an ankylosed stage where stability was increased. LEVEL OF EVIDENCE: 3.

Motion characteristics and related factors of Modic changes in the lumbar spine.

OBJECT Most studies of Modic changes (MCs) have focused on investigating the relationship between MCs and lowback pain, whereas the kinematic characteristics and degenerative disc disease associated with MCs are not well understood. To the authors' knowledge, no previous study has reported on the kinematics of MCs. The purpose of this study was to elucidate the relationship of MCs to segmental motion and degenerative disc disease. METHODS Four hundred fifty symptomatic patients underwent weight-bearing lumbar kinematic MRI in the neutral, flexion, and extension positions. Segmental displacement and intervertebral angles were measured in 3 positions using computer analysis software. Modic changes, disc degeneration, disc bulging, spondylolisthesis, angular motion, and translational motion were recorded, and the relationship of MCs to these factors was analyzed using a logistic regression model. To control the influence of disc degeneration on segmental motion, angular and translational motion were analyzed according to mild and severe disc degeneration stages. The motion characteristics and disc degeneration among types of MCs were also evaluated. RESULTS Multivariate analysis revealed that age, disc degeneration, angular motion, and translational motion were factors significantly related to MCs. In the severe disc degeneration stage, a significant decrease of angular motion and significant increase of translational motion were found in segments with MCs, indicating that a disorder of the endplate had an additional effect on segmental motion. Disc degeneration increased and angular motion decreased significantly and gradually as the type of MC increased. Translational motion was significantly increased with Type 2 MCs. CONCLUSIONS Age, disc degeneration, angular motion, and translational motion were significantly linked to MCs in the lumbar spine. The translational motion of lumbar segments increased with Type 2 MCs, whereas angular motion decreased as the type of MC increased, indicating that Type 2 MCs may have translational instability likely due to degenerative changes. A disorder of the endplates could play an important role in spinal instability.

Comparison of a novel oxysterol molecule and rhBMP2 fusion rates in a rabbit posterolateral lumbar spine model.

BACKGROUND CONTEXT: The nonunion rate after lumbar spinal fusion is as high as 25%. Recombinant human bone morphogenetic protein 2 (rhBMP2) has been used as a biological adjunct to promote bony fusion. However, recently there have been concerns about BMP2. Oxysterol 133 (Oxy133) has been shown to promote excellent fusion rates in rodent lumbar spine models and offers a potential alternative to rhBMP2. PURPOSE: The purpose of this study was to compare the fusion rate of rhBMP2 and Oxy133 in a randomized controlled trial using a posterolateral lumbar rabbit spinal fusion model. STUDY DESIGN: This was a randomized control animal study. METHODS: Twenty-four male adult white New Zealand rabbits (3-3.5 kg) underwent bilateral posterolateral lumbar spinal fusion at L4-L5. Rabbits were divided into four groups: control (A), 30-µg rhBMP2 (B), 20-mg Oxy133 (C), and 60-mg Oxy133 (D). At 4 weeks, fusion was evaluated by fluoroscopy, and at 8 weeks, the rabbits were sacrificed and fusion was evaluated radiographically, by manual palpation, and with microcomputed tomography. RESULTS: Fusion rates by radiographic analysis at 8 weeks were Group A, 40.0%; Group B, 91.7%; Group C, 91.7%; and Group D, 100%. Evaluation of fusion masses by manual palpation of excised spines after sacrifice showed the following fusion rates: Group A, 0%; Group B, 83.3%; Group C, 83.3%; and Group D, 90%. Microcomputed tomography scanning confirmed these findings. CONCLUSIONS: These findings in a rabbit model demonstrate that both 20- and 60-mg Oxy133 doses promote fusion that is equivalent to fusion induced by 30-µg rhBMP2 and significantly greater than the control group. The present findings confirm that Oxy133 is a promising candidate for therapeutic development as an alternative to rhBMP2 to promote spinal fusion.

Secreted phosphoprotein 24 kD inhibits nerve root inflammation induced by bone morphogenetic protein-2.

BACKGROUND CONTEXT: Bone morphogenetic protein-2 (BMP-2) has been used to successfully promote spine fusion, but side-effects including nerve inflammation have been observed. PURPOSE: To investigate the direct neurotoxic effects of BMP-2 and test the hypotheses that the use of BMP binding proteins, such as secreted phosphoprotein 24 kD (Spp24), can reduce or eliminate these effects. STUDY DESIGN: In vitro experiments and in vivo analysis in a rodent model. METHODS: In vitro, dorsal root ganglion cells were cultured in the presence of BMP-2 with and without Spp24 and calcitonin gene-related peptide and Substance P, markers of neuroinflammation, were measured by immunohistochemistry. In vivo, rats underwent a left-sided laminotomy at L5 to expose the S1 nerve root and were randomized into four different groups according to the intervention at the laminotomy site: collagen sponge only (no BMP-2 or Spp24), BMP-2 in a collagen sponge only, BMP-2 in a collagen sponge+an empty collagen sponge to act as a barrier, and BMP-2 in a collagen sponge+Spp24 in a collagen sponge to act as a barrier. Functional evaluation was done using the Basso, Beattie, and Bresnahan scale and immunohistochemical analyses were performed using calcitonin gene-related peptide and Substance P staining. RESULTS: The neuroinflammatory effects of BMP-2 in vitro were ameliorated by the addition of Spp24. Similarly, in vivo, Spp24 reduced the expression of markers on neuroinflammation in animals treated with BMP-2 and also improved the function after BMP-2 administration. CONCLUSIONS: These results confirm that BMP binding proteins have great potential as adjuvant therapies to limit BMP-2 related side-effects in spine surgery.

Risk factors for missed dynamic canal stenosis in the cervical spine.

STUDY DESIGN: Retrospective analysis of kinematic magnetic resonance (MR) images. OBJECTIVE: To elucidate the distribution and risk factors associated with missed dynamic stenosis in cervical spine. SUMMARY OF BACKGROUND DATA: Motion of the cervical spine is widely accepted to be associated with cervical spondylotic myelopathy; however, the distribution and the risk factors for dynamic spinal stenosis are not well understood. METHODS: A total of 435 symptomatic patients (2610 cervical segments) obtained upright kinematic MR images in neutral, flexion, and extension postures. Spinal cord compression (SCC), spondylolisthesis, disc bulging, angular motion, translational motion, disc degeneration grade, Modic changes, segmental alignment, and developmental stenosis were all evaluated. Cervical segments C2-C3 to C7-T1 were divided into 2 groups, determined by the presence of SCC. After excluding segments with SCC in the neutral position, a multivariate logistic regression model was used to evaluate for associated risk factors of SCC in flexion and extension that were not present in the neutral position. RESULTS: SCC in neutral position was observed in 5.3% (139/2610) of segments. After excluding these segments, missed dynamic stenosis was found in 8.3% (204/2471) of segments in extension and 1.6% (40/2471) in flexion. Missed dynamic stenosis in both extension and flexion was most frequent at C5-C6. Multivariate logistic regression analysis for dynamic stenosis in extension revealed that disc bulge greater than 2.4 mm, angular motion greater than 4.8°, moderate and severe disc degeneration, segmental kyphosis, and developmental stenosis were significant risk factors. In flexion, significant risk factors were a disc bulge of 1.9 mm or greater, moderate to severe disc degeneration, and segmental kyphosis. CONCLUSION: Dynamic cord compression was most common at the C5-C6 segment. Cervical segments with greater disc bulge, more severe disc degeneration, greater angular motion, segmental kyphosis, and developmental stenosis may be at risk for missed dynamic stenosis.

Effect of cervical kyphotic deformity type on the motion characteristics and dynamic spinal cord compression.

STUDY DESIGN: Retrospective analysis of kinematic magnetic resonance images. OBJECTIVE: To provide baseline data on the segmental angular and translational motion of the degenerated cervical spine by subtype of kyphotic cervical deformity and to elucidate the relationship between motion and degree of spinal cord compression. SUMMARY OF BACKGROUND DATA: Kyphotic deformities of the cervical spine are relatively common and are classified as either global or focal. Nevertheless, the effects of kyphotic subtype on cervical segmental motion and degree of spinal cord compression are unknown. METHODS: A total of 1171 symptomatic patients (618 females, 553 males) underwent cervical kinematic magnetic resonance imaging in the neutral, flexion, and extension positions. Cervical spines demonstrating kyphosis were included and classified into 3 groups: (1) "global kyphotic deformity" (C-type) (n = 54); (2) "sigmoid deformity" (S-type) with kyphotic upper and lordotic lower cervical segments (n = 29); and (3) "reverse sigmoid deformity" (R-type) with lordotic upper and kyphotic lower cervical segments (n = 39). Translational motion, angular motion, and degree of spinal cord compression were evaluated for each cervical level along with the changes associated with flexion and extension. RESULTS: In the C- and R-types, angular motion with extension was increased in the upper cervical spine, where there was kyphosis; when compared with the S-type, in which there was lordosis in the upper segments. The results were opposite for flexion angular motion. R-type displayed more translational motion at C3-C4 and C5-C6. Degree of static spinal cord compression of R-type was higher than the others at C3-C4. The dynamic spinal cord compression increased in extension more than flexion in all subtypes. CONCLUSION: Cervical spine studies that aim to investigate kyphotic deformities should make efforts to discern the different subtypes of kyphotic deformities to more accurately characterize and study the effects that the sagittal alignment has on the kinematics of the spine and the degree of spinal cord compression.