Jigang Lou

The effect of deviated center of rotation on flexion-extension range of motion after single-level cervical arthroplasty: an in vivo study.

Study Design. A retrospective study. Objective. To report the clinical outcomes and sagittal kinematics after cervical total disc replacement (TDR). To evaluate the in vivo effect of deviated center of rotation (COR) on flexion-extension range of motion (ROM) at the instrumented level. Summary of Background Data. A few studies showed that the location of COR after cervical TDR deviated from its preoperative location or inherent location in healthy subjects. However, little is known about the effect of deviated COR on ROM at the instrumented level. Methods. A total of 24 patients who underwent C5–C6 single-level TDR with Prestige LP (Medtronic Sofamor Danek) were retrospectively included. Japanese Orthopedic Association score and visual analogue scale were used to assess the clinical outcomes. ROM and COR were measured for radiographical analysis. Patients were categorized into 2 groups according to the change of ROM for further evaluation. Group 1, characterized by decreased postoperative ROM, consisted of 16 patients; group 2, characterized by increased postoperative ROM, consisted of 8 patients. Results. Ten males and 14 females comprised the study cohort. The mean age was 45.05 years, and the mean follow-up time was 15.5 months. The Japanese Orthopedic Association score increased significantly and the neck and arm visual analogue scale decreased significantly after cervical TDR. On average, ROM was preserved after cervical TDR. The postoperative COR had a significant cranial shift from its preoperative location. The COR shift in anterior-posterior direction was larger in group 2 than that in group 1. No difference was observed in the COR shift in cranial-caudal direction between the 2 groups. Conclusion. Single-level cervical TDR with Prestige LP obtained satisfactory clinical outcomes and partially restored the natural cervical kinematics. At instrumented level, the deviated COR had a negative correlation with the flexion-extension ROM. 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.

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 a biological reactor and platelet-rich plasma for the construction of tissue-engineered bone to repair articular cartilage defects

Articular cartilage defects are a major clinical burden worldwide. Current methods to repair bone defects include bone autografts, allografts and external fixation. In recent years, the repair of bone defects by tissue engineering has emerged as a promising approach. The present study aimed to assess a novel method using a biological reactor with platelet-rich plasma to construct tissue-engineered bone. Beagle bone marrow mesenchymal stem cells (BMSCs) were isolated and differentiated into osteoblasts and chondroblasts using platelet-rich plasma and tricalcium phosphate scaffolds cultured in a bioreactor for 3 weeks. The cell scaffold composites were examined by scanning electron microscopy (SEM) and implanted into beagles with articular cartilage defects. The expression of osteogenic markers, alkaline phosphatase and bone γ-carboxyglutamate protein (BGLAP) were assessed using polymerase chain reaction after 3 months. Articular cartilage specimens were observed histologically. Adhesion and distribution of BMSCs on the β-tricalcium phosphate (β-TCP) scaffold were confirmed by SEM. Histological examination revealed that in vivo bone defects were largely repaired 12 weeks following implantation. The expression levels of alkaline phosphatase (ALP) and BGLAP in the experimental groups were significantly elevated compared with the negative controls. BMSCs may be optimum seed cells for tissue engineering in bone repair. Platelet-rich plasma (PRP) provides a rich source of cytokines to promote BMSC function. The β-TCP scaffold is advantageous for tissue engineering due to its biocompatibility and 3D structure that promotes cell adhesion, growth and differentiation. The tissue-engineered bone was constructed in a bioreactor using BMSCs, β-TCP scaffolds and PRP and displayed appropriate morphology and biological function. The present study provides an efficient method for the generation of tissue-engineered bone for cartilage repair, compared with previously used methods.

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.

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.

In vitro biomechanical comparison after fixed- and mobile-core artificial cervical disc replacement versus fusion

Abstract In vitro biomechanical analysis after cervical disc replacement (CDR) with a novel artificial disc prosthesis (mobile core) was conducted and compared with the intact model, simulated fusion, and CDR with a fixed-core prosthesis. The purpose of this experimental study was to analyze the biomechanical changes after CDR with a novel prosthesis and the differences between fixed- and mobile-core prostheses. Six human cadaveric C2–C7 specimens were biomechanically tested sequentially in 4 different spinal models: intact specimens, simulated fusion, CDR with a fixed-core prosthesis (Discover, DePuy), and CDR with a mobile-core prosthesis (Pretic-I, Trauson). Moments up to 2 Nm with a 75 N follower load were applied in flexion–extension, left and right lateral bending, and left and right axial rotation. The total range of motion (ROM), segmental ROM, and adjacent intradiscal pressure (IDP) were calculated and analyzed in 4 different spinal models, as well as the differences between 2 disc prostheses. Compared with the intact specimens, the total ROM, segmental ROM, and IDP at the adjacent segments showed no significant difference after arthroplasty. Moreover, CDR with a mobile-core prosthesis presented a little higher values of target segment (C5/6) and total ROM than CDR with a fixed-core prosthesis (P > .05). Besides, the difference in IDP at C4/5 after CDR with 2 prostheses was without statistical significance in all the directions of motion. However, the IDP at C6/7 after CDR with a mobile-core prosthesis was lower than CDR with a fixed-core prosthesis in flexion, extension, and lateral bending, with significant difference (P < .05), but not under axial rotation. CDR with a novel prosthesis was effective to maintain the ROM at the target segment and did not affect the ROM and IDP at the adjacent segments. Moreover, CDR with a mobile-core prosthesis presented a little higher values of target segment and total ROM, but lower IDP at the inferior adjacent segment than CDR with a fixed-core prosthesis.

Migration of titanium cable into spinal cord and spontaneous C2 and C3 fusion: Case report of possible causes of fatigue failure after posterior atlantoaxial fixation.

Introduction:Atlantoaxial instability is a common and serious injury of the upper cervical spine. Brooks’ procedure is widely used to reconstruct the unstable atlantoaxial joint. The migration into spinal cord of titanium cable and spontaneous fusion between C2 and C3 has been little reported and the management of such a patient is difficult. We describe an unusual case of fatigue failure of posterior titanium atlantoaxial cable fixation with migration into the spinal cord and spontaneous fusion between C2 and C3. Case report:A 16-year-old girl complained of cervico-occipital pain with numbness and weakness of extremities 3 months ago. The girl underwent posterior C1–C2 arthrodesis with titanium cables and autogenous iliac crest bone grafting when she was 6 years old. When presented to our emergency department, imaging revealed the cracked titanium atlantoaxial cable and the spontaneous fusion between C2 and C3. Computed tomography demonstrated a broken wire with anterior migration of the cable into the spinal cord. The patient underwent posterior approach cervical spinal surgery to remove the broken cables. She remains neurologically intact a year following the posterior approach cervical spine surgery. Conclusions:Brooks’ posterior stabilization could not effectively control rotation at the atlantoaxial articulation, so surgeons must be aware of the potential of fatigue failure of cables as well as the possibility of its migration into the spinal cord when using Brooks’ posterior stabilization. Bilateral C1 lateral mass and C2 pedicle screw fixation or transarticular screw fixation are recommended by the authors in the event of rotatory instability.

Effect of intervertebral disc height on the range of motion and clinical outcomes after single-level implantation of Prestige LP cervical disc prosthesis

OBJECTIVES Cervical total disc replacement (TDR) is an emerging technology. Cervical arthroplasty theoretically reduces the risk of adjacent level disc degeneration and segmental instability. However, the factors that influence postoperative range of motion (ROM) and clinical outcomes are not fully understood. The aim of our study was to evaluate the effect of intervertebral disc height on the range of motion and clinical outcomes after single-level implantation of Prestige LP cervical disc prosthesis METHODS A total of 160 patients with single-level Prestige LP cervical disc prosthesis were evaluated. Preoperative and postoperative disc height and ROM were measured from lateral and flexion-extension radiographs by the CANVAS, and the clinical outcomes were evaluated by Japanese Orthopaedic Association (JOA) and Neck Disability Index (NDI). RESULTS Patients with less than 4mm of preoperative disc height had a mean 1.4° increase in flexion-extension ROM after cervical arthroplasty, whereas patients with greater than 4mm of preoperative disc height had no change in flexion-extension ROM. Patients with a 6-8mm of postoperative disc height had significantly higher postoperative flexion-extension ROM (11.0°±2.9) than those with less than 6mm of postoperative disc height (8.7°±3.1, p=0.01). Patients with greater than 8mm of postoperative disc height have significantly lower postoperative flexion-extension ROM (mean, 8.9°±3.2) than those with 6-8mm of postoperative disc height (p=0.03). No significant difference was found between patients with <6mm of postoperative disc height and patients with >8mm of postoperative disc height (p=0.12). The postoperative JOA and NDI both have significant difference compared with preoperation(p<0.05). No correlation could be found between disc height and the postoperative ROM, JOA or NDI. CONCLUSION Patients with less than 4mm of preoperative intervertebral disc height have a larger ROM after cervical arthroplasty. A 6-8mm of postoperative intervertebral disc height is the optimum range to maximize ROM. However, the optimal range did not translate into better clinical outcomes.