Beiyu Wang

Transplantation of mesenchymal stem cells and nucleus pulposus cells in a degenerative disc model in rabbits: a comparison of 2 cell types as potential candidates for disc regeneration

OBJECT The aim of this study was to compare transplanted mesenchymal stem cells (MSCs) with nucleus pulposus cells (NPCs) in a degenerative disc model in rabbits to determine the better candidate for disc cell therapy. METHODS Mesenchymal stem cells and NPCs were transplanted in a rabbit model of disc degeneration. Changes in disc height, according to plain radiography, T2-weighted signal intensity on MR imaging, histology, sulfated glycosaminoglycan (sGAG)/DNA, and associated gene expression levels, were evaluated among healthy controls without surgery, sham-operated animals in which only disc degeneration was induced, MSC-transplanted animals, and NPC-transplanted animals for a 16-week period. RESULTS Sixteen weeks after cell transplantation, in the MSC- and NPC-transplanted groups, the decline in the disc height index was reduced and T2-weighted signal intensity increased compared with the sham-operated group. Safranin O staining showed a high GAG content, which was also supported by sGAG/DNA assessment. Disc regeneration was also confirmed at the gene expression level using real-time polymerase chain reaction. However, no significant differences in expression were found between the NPC- and MSC-transplanted groups. CONCLUSIONS Study data showed that MSC transplantation is effective for the treatment of disc degeneration and seems to be an ideal substitute for NPCs.

The Facet Orientation of the Subaxial Cervical Spine and the Implications for Cervical Movements and Clinical Conditions

Study Design. Computed tomography study. Objective. To obtain detailed information on the facet orientation in the subaxial cervical spine and explore the correlation to the cervical movements and relevant clinical conditions. Summary of Background Data. Although facet orientation was well studied in the lumbar spine, the literatures on the cervical facet orientation were limited and the descriptions were nonspecific. Methods. The computed tomography scans of 100 individuals were reconstructed. For each level from C2/C3 to C6/C7, the horizontal plane, the mid-sagittal plane, the coronal plane, and the two facet planes were established. The normal vectors of the five planes were used for the calculation of the facet orientation and the facet tropism. Results. The angle of the facet plane with respect to the horizontal plane at the C6/7 level was the largest (left side: 64.34° ± 6.60°, right side: 63.37° ± 6.81°, P >0.05). The angle of the facet plane with respect to the coronal plane decreased from C2/C3 level to C6/C7 level. Regarding the angle of the facet plane with respect to the sagittal plane, for the paired facet joints, three types were found: posteromedially oriented, posterolaterally oriented, and ipsilaterally oriented. All (100%) of the facet joints at the C2/C3 level and 65% at the C3/C4 level were posteromedially oriented. In the lower levels of the cervical spine, the posteromedially oriented facet joints were less common. The facet tropism was common phenomenon in the subaxial cervical spine. Conclusion. This study provided detailed information on the facet orientation in the subaxial cervical spine. The cervical facet orientation correlated well with the spinal movements and related clinical conditions. Level of Evidence: 3

Multilevel cervical disc replacement versus multilevel anterior discectomy and fusion: A meta-analysis

Background: Cervical disc replacement (CDR) has been developed as an alternative surgical procedure to anterior cervical discectomy and fusion (ACDF) for the treatment of single-level cervical degenerative disc disease. However, patients with multilevel cervical degenerative disc disease (MCDDD) are common in our clinic. Multilevel CDR is less established compared with multilevel ACDF. This study aims to compare the outcomes and evaluate safety and efficacy of CDR versus ACDF for the treatment of MCDDD. Methods: A meta-analysis was performed for articles published up until August 2016. Randomized controlled trials (RCTs) and prospective comparative studies associated with the use of CDR versus ACDF for the treatment of MCDDD were included in the current study. Two reviewers independently screened the articles and data following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis statement. Results: Seven studies with 702 enrolled patients suffering from MCDDD were retrieved. Patients who underwent CDR had similar operative times, blood loss, Neck Disability Index (NDI) scores, and Visual Analog Scale (VAS) scores compared to patients who underwent ACDF. Patients who underwent CDR had greater overall motion of the cervical spine and the operated levels than patients who underwent ACDF. Patients who underwent CDR also had lower rates of adjacent segment degeneration (ASD). The rate of adverse events was significantly lower in the CDR group. Conclusion: CDR may be a safe and effective surgical strategy for the treatment of MCDDD. However, there is insufficient evidence to draw a strong conclusion due to relatively low-quality evidence. Future long-term, multicenter, randomized, and controlled studies are needed to validate the safety and efficacy of multilevel CDR.

Comparison of the incidence of patient-reported post-operative dysphagia between ACDF with a traditional anterior plate and artificial cervical disc replacement

PURPOSE Compared with anterior cervical discectomy and fusion (ACDF), cervical disc replacement (CDR) has provided satisfactory clinical results. The incidence of post-operative dysphagia between ACDF with a traditional anterior plate and CDR remains controversial. Considering the limited studies and knowledge in this area, a retrospective study focusing on post-operative dysphagia was conducted. METHODS The Bazaz grading system was used to assess the severity of dysphagia at post-operative intervals including 1 week, 1 month, 3 months, 6 months, 12 months and 24 months respectively. The Chi-square test, Student t-test, Mann-Whitney U tests and Ordinal Logistic regression were used for data analysis when appropriate. Statistical significance was accepted at a probability value of <0.05. RESULTS Two hundred and thirty-one patients in the CDR group and one hundred and fifty-eight patients in Plate group were included in this study. The total incidences of dysphagia in the CDR and plate group were 36.58% and 60.43% at one week, 29.27% and 38.85% at one month, 21.95% and 31.65% at three months, 6.83% and 17.99% at six months, 5.85% and 14.39% at 12 months, and 4.39% and 10.07% at the final follow-up respectively (All P<0.05, Mann-Whitney U test). Ordinal Logistic regression analysis showed that female patients, two-level surgery, C4/5 surgery, and anterior cervical plating were significant risk factors for post-operative dysphagia (all P<0.05). CONCLUSION Comparing ACDF with a plate, CDR with a Prestige LP can significantly reduce both transient and persistent post-operative dysphagia. Female patients, two-level surgery, C4/5 surgery and anterior cervical plating were associated with a higher incidence of dysphagia. Future prospective, randomized, controlled studies are needed to further validate these findings.

Geometry of inferior endplates of the cervical spine

OBJECTIVES Device subsidence is a well-known complication following cervical disc arthroplasty. Its occurrence has been closely tied with the endplate-implant contact interface. But current literature on the geometry of cervical endplate is very scarce. The aim of this anatomical investigation was to analyze geometry of inferior endplates of the cervical vertebrae, thereby identifying the common endplate shape patterns and providing morphological reference values consummating the design of the implant. PATIENTS AND METHODS Reformatted CT scans of 85 individuals were analyzed and endplate concave depth, endplate concave apex location, sagittal diameter of endplate, coronal concave angle, as well as transverse diameter of endplate were measured in mid-sagittal plane and specified coronal plane. According to the endplate concave apex location, the inferior endplates in mid-sagittal plane were classified into 3 types: type I with posteriorly positioned apex, type II with middle situated concave apex and type III with anteriorly positioned apex. Moreover, the inferior endplates in specified coronal plane were also classified into three types: concave, flat and irregular. RESULTS Based on visual assessment, for the mid-sagittal plane, type I endplate accounted for 26.9% of all the 510 endplates of 85 individuals, while the proportion of type II and type III endplates were 53.9 and 19.2% respectively. For the specified coronal plane, 68.6% of all the 510 endplates were evaluated as concave, 26.9% as flat and the remaining 4.5% as irregular. Among all measured segments, C3 had the largest endplate concave depth values in mid-sagittal plane, while C7 the least; C5 and C6 had the largest sagittal endplate diameter values, while C2 the least. For each level, the sagittal endplate concave depth and endplate diameter of females were significantly smaller than those of males (P<0.05). Among all measured segments, C7 had the least coronal concave angle. Gender did not influence coronal concave angle significantly (P>0.05). Increasing from C2 to C7, the endplate transverse diameters of females were significantly smaller than those of males (P<0.05). CONCLUSION The exact shape and geometry of cervical endplate are crucial for the design and improvement of cervical disc prosthesis. Gender difference of sagittal and transverse diameters of cervical endplate should be given more attention when implanting a disc prosthesis. These endplate geometrical parameters should be taken into consideration when calculating most suitable geometric parameters of new disc prosthesis.

Use of rapid prototyping drill template for the expansive open door laminoplasty: A cadaveric study.

OBJECTIVE Trough preparation is a technically demanding yet critical procedure for successful expansive open door laminoplasty (EOLP), requiring both proper position and appropriate bone removal. We aimed to use the specific rapid prototyping drill template to achieve such requirement. METHODS The 3D model of the cadaveric cervical spine was reconstructed using the Mimics 17.0 and Geomagic Studio 12.0 software. The drilling template was designed in the 3-Matic software. The trough position was simulated at the medial margin of the facet joint. Two holders were designed on both sides. On the open side, the holder would just allow the drill penetrate the ventral cortex of the lamina. On the hinge side, the holder was designed to keep the ventral cortex of the lamina intact. One orthopedic resident performed the surgery using the rapid prototyping drill template on four cadavers (template group). A control group of four cadavers were operated upon without the use of the template. RESULTS The deviation of the final trough position from the simulated trough position was 0.18mm±0.51mm in the template group. All the troughs in the template group and 40% of the troughs in the control group were at the medial side of the facet joint. The complete hinge fracture rate was 5% in the template group, significantly lower than that (55%) in the control group (P=0.01). CONCLUSION The rapid prototyping drill template could help the surgeon accomplish proper trough position and appropriate bone removal in EOLP on the cadaveric cervical spine.

Posterior distraction reduction and occipitocervical fixation for the treatment of basilar invagination and atlantoaxial dislocation

OBJECT To introduce a novel distraction technique for the treatment of basilar invagination (BI) and atlantoaxial dislocation (AAD) via a posterior-only approach. METHODS Twenty-one consecutive patients with BI and AAD who underwent posterior distraction reduction and occipitocervical fixation between January 2009 and June 2013 were enrolled in the present study. This novel distraction technique included two steps. First, the distraction between the occipitocervical junction of the rod (OCJR) and the occipital screws was performed to achieve horizontal and partial vertical reduction. Secondly, the distraction was performed between the C2 screws and OCJR to achieve complete vertical reduction. The pre- and postoperative JOA score, the extent of reduction, the fusion status, and the complications were recorded and analyzed. RESULTS The mean follow-up was 18.3 months with a range of 10-32 months. No patient incurred neurovascular injury during surgery. The mean JOA score at the last follow-up (15.4) showed significant improvement (P<0.01) compared with the pre-operative parameters (11.2). Complete horizontal reduction was achieved in 18 patients (85.7%), and complete vertical reduction was achieved in 17 patients (80.9%). The rest patients are all received greater than 50% horizontal and vertical reduction. Solid fusion was achieved in 20 patients (95.2%). Mild dysphagia was observed in two patients. One patient suffered from postoperative fever and pulmonary infection. CONCLUSION This novel distraction technique may provide satisfactory reduction via a posterior-only approach without exposure of the C1/2 facet joint. Therefore, it is a safe and effective method for the treatment of BI with AAD.

Clinical and radiographic features of hybrid surgery for the treatment of skip-level cervical degenerative disc disease: A minimum 24-month follow-up

We describe the radiographic changes of IS and investigate the safety and feasibility of hybrid surgery (HS) coupling cervical disc arthroplasty (CDA) and anterior cervical discectomy and fusion (ACDF) for the treatment of skip-level cervical degenerative disc disease (CDDD). Twenty-seven patients who received HS were retrospectively reviewed. Clinical evaluation based on the Japanese Orthopedic Association (JOA) and Neck Disability Index (NDI) and Visual Analog Scale (VAS) scores. Radiographic parameters included cervical alignment (CA), functional spine unite (FSU) angle of intermediated segment (IS), range of motion (ROM) and intervertebral disc height (IDH). Data regarding radiographic changes at IS were collected. The mean follow-up duration of 30.10months. Compared with preoperative value, JOA, NDI and VAS scores significantly improved after surgery (p<0.05). The CA was recovered significantly after surgery (p<0.05). There was no significant difference in the FSU angle and the IDH of IS between before and at 24months postoperatively (p>0.05). The ROM of IS significantly decreased at the first week after surgery (p<0.05), was similar to preoperative value at 3months postoperatively and significantly increased after 6months (p<0.05). Radiographic changes at IS were observed in 2 patients and Class II Heterotopic ossification (HO) was detected in 2 patients. HS is a safe and feasible alternative procedure for the treatment of skip-level CDDD. It preserved the IS intact and achieved satisfactory clinical and radiographic outcomes over a 24-month follow-up.

Cervical disc arthroplasty for the treatment of adjacent segment disease: A systematic review of clinical evidence

The safety and efficacy of cervical disc arthroplasty (CDA) performed adjacent to previous fusion for the treatment of adjacent segment disease (ASD) remains unknown. This systematic review summarizes clinical evidence on the outcomes of CDA performed adjacent to previous cervical fusion. A systematic search of PubMed, Cochrane Central Register of Controlled Trials (CENTRAL), Medline and Embase for literature published through March 2017 was conducted. All the studies on CDA for the treatment of ASD after cervical fusion surgery were included. Two independent reviewers searched and assessed the literature according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines (PRISMA). A total of 5 studies were identified. The overall quality of evidence was low. All included studies demonstrated that clinical outcomes reflected by several assessment scales improved after arthroplasty. Cervical lordosis range of motion (ROM) after arthroplasty remained and was even enhanced postoperatively. The rate of complications and subsequent surgeries was low. There is a dearth of information regarding the outcomes of CDA for the treatment of ASD in the literature. In general, CDA may be a safe and effective surgical procedure to treat ASD, but this conclusion needs to be confirmed by future long-term, prospective clinical trials.

Artificial cervical disc replacement with the Prestige-LP prosthesis for the treatment of non-contiguous 2-level cervical degenerative disc disease: A minimum 24-month follow-up

OBJECTIVE We describe the features of non-contiguous 2-level cervical degenerative disc disease (NCDDD), investigate the safety and feasibility of artificial cervical disc replacement (ACDR) for the treatment of NCDDD, and expect that our study will provide spine surgeons with an alternative procedure for NCDDD. METHODS Twenty-five patients with NCDDD received ACDR with a Prestige-LP prosthesis. Clinical outcomes were evaluated using the 36-Short Form (SF-36, Mental Component Summary [MCS] and Physical Component Summary [PCS]), Visual Analog Scale (VAS), Japanese Orthopedic Association (JOA), and Neck Disability Index (NDI) scores. Radiographic evaluations included cervical lordosis (CL), range of motion (ROM), and disc height (DH). Data regarding complications were collected as well. RESULTS The mean follow-up period was 32.24 months. Clinical outcomes, including SF-36 MCS and PCS, VAS, JOA, and NDI scores significantly improved at the 24-month follow-up (p<0.05). There were no significant differences in CL and ROM at the 24-month follow-up (p>0.05). Although there was a significant difference between the before and 3-month follow-up (p<0.05), the ROM of the intermediate segment (IS) showed a tendency of returning to the preoperative state. The DH of the IS was maintained at each measurement while the DH of the upper and lower operated segments significantly increased at the 24-month follow-up (p<0.05). One patient, whose prosthesis remained mobile at the last follow-up, showed evidence of heterotopic ossification (HO). CONCLUSION ACDR with the Prestige-LP prosthesis is a safe and feasible alternative procedure for treatment of NCDDD. In the future, a large-sample, prospective randomized controlled study with long-term follow-up will be needed to further demonstrate noncontiguous ACDR as an optimal surgical option for NCDDD.