The development of posterior reduction forceps for atlantoaxial dislocation and its preliminary application in irreducible atlantoaxial dislocation.

OBJECTIVE: To develop posterior reduction forceps for atlantoaxial dislocation and evaluate the preliminary clinical application of this forceps in assisting simple posterior screw-rod system reduction and fixation in the treatment of irreducible atlantoaxial dislocation. METHODS: Based on the posterior atlantoaxial screw-rod system, posterior reduction forceps was developed to assist simple posterior screw-rod system for the treatment of irreducible atlantoaxial dislocation. From January 2021 to October 2022, 10 cases with irreducible atlantoaxial dislocation were treated with this technique. The Japanese Orthopaedic Association (JOA) score was applied before and after surgery to evaluate the neurological status of the patient, and the Atlanto-dental interval (ADI) was measured before and after surgery to evaluate the atlantoaxial reduction. X-ray and CT were performed to evaluate internal fixation, atlantoaxial sequence and bone graft fusion during regular follow-up. MRI was performed to evaluate the status of atlantoaxial reduction and spinal cord compression after surgery. RESULTS: All 10 patients were successfully operated, and there were no complications such as spinal nerve and vascular injury. Postoperative clinical symptoms were significantly relieved in all patients, and postoperative JOA score and ADI were significantly improved compared with those before surgery (P < 0.05). CONCLUSIONS: The developed posterior reduction forceps for atlantoaxial dislocation can assist the simple posterior screw-rod system in the treatment of irreducible atlantoaxial dislocation to avoid the release in anterior or posterior approach and reduce the difficulty of surgery. The preliminary results of this technique are satisfactory and it has a good application prospect.

Comparison of transoral anterior Jefferson-fracture reduction plate and posterior screw-rod fixation in C1-ring osteosynthesis for unstable atlas fractures.

Objective: To compare the clinical outcomes of transoral anterior Jefferson fracture reduction plate (JeRP) and posterior screw rod (PSR) surgery for unstable atlas fractures via C1-ring osteosynthesis. Methods: From June 2009 to June 2022, 49 consecutive patients with unstable atlas fractures were treated by transoral anterior JeRP fixation (JeRP group) or PSR fixation (PSR group) and followed up at our hospital; 30 males and 19 females were included. The visual analogue scale (VAS) score, neck disability index (NDI), distance to anterior arch fracture (DAAF), distance to posterior arch fracture (DPAF), lateral mass displacement (LMDs), Redlund-Johnell value, postoperative complications, and fracture healing rate were retrospectively collected and statistically analyzed. Results: Compared with that in the PSR group, the bleeding volume in the JeRP group was lower, and the length of hospital stay was longer. The VAS scores and NDIs of both groups were significantly improved after surgery. The postoperative DAAF and DPAF were significantly smaller after surgery in both groups. Compared with the significantly shorter DPAF in the PSR group, the JeRP group had a smaller DAAF, shorter LMDs and larger Redlund-Johnell value postoperatively and at the final follow-up. The fracture healing rate at 3 months after surgery was significantly greater in the JeRP group (P<0.05). Conclusion: Both C1-ring osteosynthesis procedures for treating unstable atlas fractures yield satisfactory clinical outcomes. Transoral anterior JeRP fixation is more effective than PSR fixation for holistic fracture reduction and short-term fracture healing, but the hospital stay is longer.

Surgical Failure and Revision Strategy for Atlantoaxial Dislocation: A retrospective study of 109 Cases.

STUDY DESIGN: Retrospective study. OBJECTIVE: To classify surgical failures following atlantoaxial dislocation, present strategies for revisions and evaluate the clinical results of revision surgery. SUMMARY OF BACKGROUND DATA: With the increase in atlantoaxial dislocation surgery, the number of surgical failures has gradually risen. However, current reports on atlantoaxial surgical revision are limited in scope. There remains a lack of summary regarding the causes of surgical failure, a detailed classification system, and no proposed strategy for revision surgery. METHODS: 109 cases of failed surgery following atlantoaxial dislocation were classified according to the reduction immediately after surgery and the fusion status before revision. The reduction, decompression, fusion status and outcomes following revision surgery were evaluated by X-ray, CT, MRI and JOA score. The data were analyzed statistically with a paired-samples t test and multivaraible logistic regression analysis. RESULTS: The 109 patients were classified into three categories of failure: non-reduction with non-fusion (NR-NF, 73 cases), non-reduction with fusion (NR-F, 19 cases), and reduction with non-fusion (R-NF, 17 cases). Sixty-four patients underwent anterior revision, 21 posterior revision, and 24 anteroposterior revision. Postoperative complications were the primary cause of early revisions. After revision, complete decompression was achieved in all cases, anatomical reduction in 89 cases, significant improvement of JOA score in 77 cases, and fusion achieved in 86 cases. Twelve cases experienced surgical complications and 3 underwent a second revision. CONCLUSIONS: We found that NR-NF was the most common type of failure following surgery for atlantoaxial dislocation. Revision strategies can be guided according to our descriptive classification of failure, and revision surgery should focus on achieving adequate reduction, appropriate fixation and reliable fusion to optimize post-surgical outcomes.

Calcium phosphate cement promotes the stability of osteoporotic lumbar pedicle screw by enhancer-injecters with different number of holes.

BACKGROUNDS: This study aimed to compare whether Calcium phosphate cement (CPC) promotes the stability of osteoporotic lumbar pedicle screw by enhancer-injecters with different number of holes. METHODS: Through a self-designed bone cement injection device, the pedicle screw canal was strengthened with calcium phosphate bone cement, and divided into 4-hole group, 6-hole group, 8-hole group, straight pore group and the control group. The screw was inserted into the mechanical test module, the Maximum insertion torque and Maximum axial pull-out strength were recorded, and the distribution of calcium phosphate bone cement was analyzed by CT and X-ray. The data results were analyzed using SPSS19.0 statistical software package. RESULTS: The distribution of bone cement in different reinforcement groups was different and showed regularity. The bone cement in the 4-hole group was roughly located in the head 1/3 of the screw, the 6-hole group was located in the middle 1/3 of the screw, and the 8-hole group was located in the caudal 1/3 of the screw. Compared with the control group, the maximum axial pull-out force of screws in the lateral hole and full screw tunnel reinforcement group was significantly increased. There was no significant difference between the 4-hole, 6-hole and straight pore groups. There was no difference in the screw-in torque between the reinforcement groups, and they all increased significantly compared with the control group, and the difference was statistically significant. After the screw was pulled out, the interface between the bone cement and the polyurethane material was fractured, and a tight package was formed with the screw. CONCLUSIONS: Enhancer syringes with different hole numbers combined with CPC bone cement injection can significantly increase the maximum screw pull-out force. The 8-hole group has a smaller pull-out force and is relatively prone to leakage of reinforcing material, which lacks safety in use. The local reinforcement of 4-hole and 6-hole sheath can play a similar role to that of total nail tunnel reinforcement.

Could extended laminectomy effectively prevent spinal cord injury due to spinal shortening after 3-column osteotomy?

OBJECTIVE: To explore whether the laminectomy extension can effectively prevent spinal cord injury (SCI) due to spinal shortening after 3-column osteotomy in goat models. METHODS: A total of twenty healthy goats were included and done with 3-column osteotomy of T13 and L1 under the somatosensory evoked potential (SSEP) monitoring. The samples were divided into two groups. The first group underwent regular laminectomy while the second group underwent an extended laminectomy with an extra 10 mm-lamina cranial to L2. The SSEP measured after 3-column osteotomy was set as the baseline, and the SSEP decreased by 50% from the baseline amplitude and/or delayed by 10% relative to the baseline peak latency was set as positive results, which indicated spinal cord injury. The vertebral column was gradually shortened until the SSEP monitoring just did not show a positive result. The height of the initial osteotomy gap (the distance from the lower endplate of T12 to the upper endplate of L2), the shortened distance (△H), the number of spinal cord angulated and the changed angle of the spinal cord (△α) were measured and recorded in each group. Neurological function was evaluated by the Tarlov scores on day 2 postoperatively. RESULTS: All the goats except one of the first group due to changes in the SSEP during the osteotomy were included and analyzed. In the first group, the height of the initial osteotomy segment and the safe shortening distances were 61.6 ± 2.6 mm and 35.2 ± 2.6 mm, respectively; the spinal cord of 5 goats was angulated (46.4 ± 6.6°), the other four goats were kinked and not angulated. In the second group, the height of the initial osteotomy segment and the safe shortening distances were 59.8 ± 1.5 mm and 43.3 ± 1.2 mm, respectively, and the spinal cord of ten goats were angulated (97.6 ± 7.2°). There was no significant difference in the height of the initial osteotomy segment between the two groups by using Independent-Samples T-Test, P = 0.095 (P > 0.05); there were significant difference in the safe shortening distance and the changed angle of the spinal cord between the two groups by using Independent-Samples T-Test (both [Formula: see text]H and [Formula: see text]α of P < 0.001), the difference between their mean were 8.1 mm and 51.2°. Significant difference was found in the number of spinal cord angulation between the two groups through Fisher's exact test (5/9 vs. 10/10, P = 0.033). CONCLUSIONS: An additional resection of 10 mm-lamina cranial to L2 showed the satisfactory effect in alleviating SCI after 3-column osteotomy. Timely and appropriate extend laminectomy could be a promising therapeutic strategy for SCI attributable to facilitating spinal cord angulation rather than spinal cord kinking and increasing the safe shortening distance.

Biomechanical Study of Horizontal Screw-screw Crosslink in C1-2 Pedicle Screw-rod Fixation.

STUDY DESIGN: This is a biomechanical study in vitro. OBJECTIVE: To investigate the biomechanical differences between horizontal rod-rod crosslink (hR-R CL) and the horizontal screw-screw crosslink (hS-S CL) implementation in C1-2 pedicle screw-rod (C1-2 PSR) fixation. SUMMARY OF BACKGROUND: To improve internal fixation stability, transverse connector (TC) is used in C1-2 PSR to increase torsional stiffness. The connection mode of horizontal connection includes hR-R CL and hS-S CL. hS-S CL adopted in C1-2 PSR was rarely reported and its biomechanics are still unclear. MATERIALS AND METHODS: Six fresh cadaveric cervical spine specimens were each tested as an Intact model, then modified and tested as an Instability model (unstable odontoid fractures), and then as 3 internal fixation models, including C1-2 PSR, C1-2 pedicle screw-rod+horizontal rod-rod crosslink (C1-2 PSR+ hR-R CL), C1-2 pedicle screw-rod+horizontal screw-screw crosslink (C1-2 PSR+ hS-S CL). The ROM of the C1-2 segments was measured by applying 1.5 nm load in 6 loading conditions, including flexion-extension (FE), left and right lateral bending (LB), and left and right axial rotation (AR). RESULTS: The C1-2 PSR+hR-R CL and C1-2 PSR+hS-S CL models, respectively, showed 60% and 75% lower ROM than the C1-2 PSR model in LB and AR conditions ( P <0.05). ROM was comparable between the C1-2 PSR+hR-R CL and the C1-2 PSR+hS-S CL models in all loading conditions ( P >0.05). CONCLUSION: Both types of crosslinks showed superior C1-2 stability under LB and AR conditions than PSR without crosslinks. The C1-2 segment stability was comparable between the 2 types of crosslinks themselves.

Management of Unstable C1 Fractures Involving the Lateral Mass: Posterior C1-C2 Screw-Rod Fixation and Fusion.

BACKGROUND Although most unstable C1 fractures can be effectively treated either by conservative treatment with external immobilization or by surgical procedure of C1-ring osteosynthesis, those fractures involving the lateral mass are likely to lead to traumatic arthritis and persistent neck pain. Specific reports of treatment of unstable C1 fractures involving the lateral mass are still scarce. We therefore present this report to evaluate the effectiveness of posterior C1-C2 screw-rod fixation and fusion for unstable C1 fractures involving the lateral mass. MATERIAL AND METHODS From June 2009 to June 2016 in our hospital, 16 cases were diagnosed with C1 fractures involving the lateral mass and treated by posterior C1-C2 screw-rod fixation and fusion from June 2009 to June 2016. The patients' clinical data were retrospectively analyzed. Preoperative and postoperative images were taken to evaluate cervical sequence, location of screws, and bone fusion. Neurological status and neck pain levels were evaluated clinically on follow-up. RESULTS All patients underwent surgery successfully. The mean follow-up duration was 15.3±4.9 months (range 9-24 months). All patients obtained satisfying clinical outcomes with good neck pain alleviation, appropriate screw placement, and reliable bone fusion. None of the patients developed vascular or neurological complications during the operation or follow-up. CONCLUSIONS Posterior C1-C2 screw-rod fixation and fusion is an effective management for unstable C1 fractures involving the lateral mass. This operation can provide reliable stabilization and satisfactory bone fusion.

The use of a novel reduction plate in transoral anterior C1-ring osteosynthesis for unstable atlas fractures.

Background: Transoral anterior C1-ring osteosynthesis has been reported as an effective treatment for unstable atlas fracture, which aims to preserve important C1-C2 motion. However, previous studies have shown that the anterior fixation plates used in this technique were not suitable for the anterior anatomy of the atlas and lacked an intraoperative reduction mechanism. Objective: This study aims to evaluate the clinical effects of a novel reduction plate used in transoral anterior C1-ring osteosynthesis for unstable atlas fractures. Methods: 30 patients with unstable atlas fractures treated by this technique from June 2011 to June 2016 were included in this study. The patients' clinical data and radiographs were reviewed, and the reduction of the fracture, internal fixation placement, and bone fusion were assessed using pre- and postoperative images. The patients' neurological function, rotatory range of motion, and pain levels were evaluated clinically during follow-up. Results: All 30 surgeries were successfully performed, and the average follow-up duration was 23.5 ± 9.5 months (range 9-48 months). One patient suffered atlantoaxial instability during the follow-up and was treated with posterior atlantoaxial fusion. The remaining 29 patients had satisfactory clinical outcomes, with ideal fracture reduction, good screw and plate placement, well-preserved range of motion, neck pain alleviation and solid bone fusion. There were no vascular or neurological complications during the operation or follow-up. Conclusions: The use of this novel reduction plate in transoral anterior C1-ring osteosynthesis is a safe and effective surgical option in the treatment of unstable atlas fractures. This technique offers an immediate intraoperative reduction mechanism, which provides satisfactory fracture reduction, bone fusion, and preservation of C1-C2 motion.

Extreme lateral interbody fusion (XLIF) approach for L5-S1: Preliminary experience.

Study Design: Technical report. Objective: Evaluate technical feasibility of extreme lateral interbody fusion (XLIF) at the L5-S1 level and provide an elaborate description of the surgical technique. Summary of Background Data: With the development of surgical techniques, the indications for oblique lumbar interbody fusion (OLIF) surgery have been broadened to the L5/S1 segment. However, this technique also has limitations. Different from OLIF, the L5/S1 segment used to be considered the main contraindication for XLIF. To date, no authors have reported the application of XLIF at the L5/S1 level. Methods: Only patients whose preoperative lumbar MRI showed the position of the psoas major muscles and blood vessels at the L5/S1 level were similar to those seen at supra-L5 levels were seleted. By folding the operating table, the iliac crest was moved downward to expose the L5/S1 intervertebral space during the operation. The remaining surgical procedures were consistent with routine XLIF surgery. Results: 8 patients successfully underwent XLIF at the L5/S1 level. The L5/S1 disk spaces were always exposed sufficiently for disk preparation and cage insertion. The post operative radiographs showed a satisfactory L5/S1 reconstruction with good cage position. Only 1 patient (12.5%) felt thigh numbness, and the symptoms gradually resolved after surgery and were no longer present in a month. There were no cases of psoas hematoma, retrograde ejaculation or vascular injury. The postoperative VAS score showed that all the patients achieved satisfactory results. Conclusions: XLIF at L5-S1 is feasible in strictly selected cases after thorough preoperative preparation and careful intraoperative procedures. However, we did not recommend XLIF as a routine surgical option at the L5/S1 level.

Cervical Sagittal Alignment in Patients With Basilar Invagination.

STUDY DESIGN: Retrospective study. OBJECTIVE: To present a morphological map of cervical sagittal alignment in basilar invagination (BI), a congenital anomaly of the craniovertebral junction, and contribute to a comprehensive understanding of cervical sagittal alignment in congenital cervical deformities. SUMMARY OF BACKGROUND DATA: Ideal cervical sagittal alignment and surgical targets are debated by scholars. However, most of the literature focuses on the description of cervical sagittal alignment in acquired cervical diseases and normal subjects and few on congenital cervical spine deformities. MATERIALS AND METHODS: This study analyzed cervical spine lateral radiographs of 87 BI patients and 98 asymptomatic subjects. They were analyzed for cranial, cervical spine, and thoracic inlet parameters. RESULTS: Patients with BI manifested significantly larger values for the following parameters than asymptomatic subjects: cranial tilt, cranial incidence angle, sagittal vertical axis (SVA) CGH-C7, C2-C7 angle, cervical tilt, and significantly smaller values for the following parameters: cranial slope, C0-C2 angle, C0-C7 angle, SVA C2-C7, spine tilt, thoracic inlet angle, and neck tilt. In the BI group, SVA C2-C7 was the cervical parameter most strongly correlated with the cranial, cervical spine, and thoracic inlet parameters, and was smaller in BI patients with fusion (atlanto-occipital assimilation) than in those without. CONCLUSION: A significant difference was observed between BI patients and asymptomatic subjects. BI patients have craniums tilted forward and downward, smaller upper cervical lordosis, larger lower cervical lordosis, and smaller thoracic inlet angle. In BI patients, the SVA C2-C7 is an important parameter in cervical sagittal alignment. In both individuals with congenital anomalies of the craniovertebral junction and the asymptomatic population, cervical spine alignment is significantly associated with cranial alignment, particularly thoracic inlet alignment.

Anatomical analysis of the C2 pedicle in patients with basilar invagination.

PURPOSE: To evaluate and describe the morphologic features of the C2 pedicle in patients with basilar invagination (BI) for informing the placement of pedicle screws. C2 pedicle screw placement is an important surgical technique for the treatment of atlantoaxial instability in patients with BI. However, no systematic and comprehensive anatomical study of the C2 pedicle in patients with BI has been reported. METHODS: The data from 100 patients diagnosed with BI (BI group) and 100 patients without head or cervical disease (control group) were included in the study. Radiographic parameters, including the pedicle width, length, height, transverse angle, lamina angle, and superior angle, were measured and analyzed on CT images. After summary analysis, the effect of C2-3 congenital fusion on C2 pedicle deformity in patients with BI was also investigated. RESULTS: The width, length, and height of the C2 pedicle of the BI patients were smaller than those of the control group. The pedicle cancellous bone was smaller in the BI group, while no significant difference in cortical bone was observed. In total, 44% of the pedicles were smaller than 4.5 mm in the BI group. Patients with C2-3 congenital fusion presented with smaller pedicle transverse angles and larger pedicle superior angles than those without fusion. Wide variations in the left and right angles of the pedicle were observed in the BI group with atlantoaxial dislocation or atlantooccipital fusion. CONCLUSION: The C2 pedicle in the BI group was thinner than that in the control group due to a smaller cortical bone. Cases of C2-3 congenital fusion, atlantoaxial dislocation, and atlantooccipital fusion displayed variation in the angle of the C2 pedicle.

A novel surgical management for pediatric patients with irreducible atlantoaxial dislocation: Transoral intraarticular cage distraction and fusion with C-JAWS staple fixation.

Background: Currently, irreducible atlantoaxial dislocation (IAAD) can be treated by a single transoral approach in one stage to reduce surgical injuries to patients. However, the widely used fixation devices are not suitable for pediatric patients because of larger profile of devices. Objective: The purpose of this study is to report the preliminary clinical outcomes of a novel surgical technique by transoral intraarticular cage distraction and fusion with C-JAWS staple fixation for pediatric patients with IAAD. Methods: From June 2011 to June 2014, eight pediatric patients with IAAD were enrolled and treated by this technique in our department. Patients' clinical data were retrospectively analyzed, including neurological status, clinical symptoms, reduction, bone fusion, and complications. Results: The surgeries were successfully performed in all patients without injuries to spinal cord, nerve and blood vessel. Clinical symptomatic relief was presented on all 8 patients (100%). Satisfactory reduction was indicated by significant decrease of atlanto-dental interval postoperatively (P < 0.05). The remarkable improvement of postoperative neurological function has been proved by significant increase of Japanese Orthopaedic Association score (P < 0.05). The average follow-up duration was 19.4 ± 5.8 months (range 12-30 months). Bone fusion was achieved in all 8 cases. No complications were documented after operation and during follow-up. Conclusions: Transoral intraarticular cage distraction and fusion with C-JAWS staple fixation is an effective treatment for pediatric patients with IAAD, which can achieve satisfactory reduction, fixation and bone fusion.

Finite Element Analysis of Horizontal Screw-Screw Crosslink Used in C1-C2 Pedicle Screw-Rod Fixation.

BACKGROUND In the craniocervical junction, a C1-C2 pedicle screw-rod (PSR) fixation is applied to provide stability. The horizontal rod-rod crosslink (hR-R CL) is often used to enhance segmental posterior instrumentation. However, the biomechanics of the alternative horizontal screw-screw crosslink (hS-S CL) in the craniocervical junction are unclear. MATERIAL AND METHODS A nonlinear atlantoaxial instability 3-dimensional C1-C2 finite element model was constructed using computed tomography images. On this basis, 2 fixation models were established with C1-C2 PSR fixation using (1) a rod-rod crosslink (R-R CL), and (2) a screw-screw crosslink (S-S CL). Range of motion (ROM) of the atlantoaxial joint, stress distribution of the implants, and maximum stress value of the vertebral bodies were calculated and compared under 4 loading conditions, including flexion, extension, lateral bending, and axial rotation. RESULTS Atlantoaxial joint ROM was reduced by 90.19% to 98.5% with the hR-R CL, and by 90.1% to 98.7% with the hS-S CL, compared with the instability model. During axial rotation, the total stress peak of the PSR fixation was smaller with hS-S CL than with hR-R CL. The peak stress values of the vertebral bodies were comparable between the 2 fixation models. CONCLUSIONS The 2 tested crosslink models provided comparable stability. However, during axial rotation, the total stress peak of hS-S CL fixation was smaller than that of hR-R CL fixation. Since the atlantoaxial joint primarily functions as a rotational joint, our results suggested that the use of hS-S CL can provide a more stable environment for the implants.

Outcome of Thoracic Column Antedisplacement and Fusion in Treatment of Thoracic Myelopathy Caused by Ossification of Posterior Longitudinal Ligament: A Case Series Study.

BACKGROUND: Up to date, surgical outcome of multilevel thoracic ossification of posterior longitudinal ligament (T-OPLL) with high canal occupation ratio is less satisfactory. OBJECTIVE: To explore the result of thoracic column antedisplacement and fusion (TCAF) in treatment of multilevel T-OPLL with high canal occupation ratio. METHODS: A total of 5 patients who underwent TCAF procedure for T-OPLL were retrospectively reviewed. Parameters including extent of OPLL, thickness of the maximal OPLL (max-OPLL), maximal canal occupying ratio (max-COR) of OPLL, effective canal diameter (ECD) at the max-OPLL level, antedisplacement distance of thoracic columns, ASIA grades, Japanese Orthopedic Association (JOA) scores, and complications were collected and analyzed at preoperation and the last follow-up. RESULTS: All patients (5 F, mean age 61.0 yr, mean follow-up 18.0 months) underwent TCAF successfully and no spinal cord injury or cerebrospinal fluid leakage occurred. The mean extent of OPLL was 2.8 vertebral bodies. The mean preoperative thickness of the max-OPLL was 5.9 mm. The average antedisplacement distance of thoracic columns was 5.6 mm. The mean ECD was improved from 6.5 mm to 10.9 mm, and the max-COR was improved from 50.7% to 7.1% at last follow-up. Two patients showed improvement in ASIA grades and JOA scores were significantly improved from 5.6 points to 10.4 points at final follow-up. The overall therapeutic results of 1 patient were classified into good and 4 into fair at last follow-up. CONCLUSION: TCAF may be a safe and effective procedure in treatment of multilevel T-OPLL with high canal occupation ratio.

Morphological Evaluation of the Subaxial Cervical Spine in Patients with Basilar Invagination: A CT-based Study.

STUDY DESIGN: Retrospective study. OBJECTIVE: To evaluate the morphologic features of the subaixal cervical spine in patients with basilar invagination (BI) and provide information for the accurate screw placement in this region. SUMMARY OF BACKGROUND DATA: BI is a congenital anomaly, comprising a wide range of abnormal structures. The screw fixation can be required in situation that BI is combined with subaxial cervical spine pathologies. However, there are no literatures specifically addressed the subaxial cervical morphology of BI. METHOD: A total of 42 BI patients were included in this retrospective study. Forty-two patients without head or cervical disease were matched for sexes and ages. Information on radiographic features of the subaxial cervical spine was collected and compared systematically. RESULTS: There were no differences in the age and sex between the BI and control group. The BI group manifested a wider pedicle and laminar than the control group at all cervical levels, except for the pedicle of C6 and C7, and the laminar of C3 and C6. In addition, the BI group had a wider lateral mass from C3 to C5 than the control group. There were no differences in most measurements of the length of pedicle, laminar, and lateral mass. CONCLUSION: BI patients have a wider pedicle and laminar than the general population in the subaxial cervical spine, but the same size in length of pedicle, laminar, and lateral mass.Level of Evidence: 4.

A biomechanical comparison of crossed and parallel rod configurations in atlantoaxial internal fixation.

BACKGROUND: Posterior atlantoaxial fixation with screw rod forms an approximate "II" shape or "H" increasing transverse link for better stability. In order to improve stability and in consideration of difficult placement of transverse connecting rod, possibility of inadequate bone graft, some scholars have preliminarily researched biomechanics of a novel crossed rod as an approximate "X" configuration of screw rod. PURPOSE: The aim of this study was to evaluate and compare the biomechanics of the crossed and parallel rod configurations in the screw rod system for posterior atlantoaxial fixation on a cadaveric model. METHODS: Six fresh cervical specimens were used to complete the range of motion (ROM) testing by applying pure moments of ± 2.0 nm. Following intact state and under destabilization testing, screws were implanted. The specimens were then tested in the following sequence: Group BLS + PR (C2 bilateral laminar screws + parallel rod), Group BLS + CR (C2 bilateral laminar screws + crossed rod), LPRLS + PR (C2 left pedicle screw and right laminar screw + parallel rod), LPRLS + CR (C2 left pedicle screw and right laminar screw + crossed rod), BPS + PR (C2 bilateral pedicle screws + parallel rod) and BPS + CR (C2 bilateral pedicle screws + crossed rod). The ROM of the C1-2 segments was measured in flexion-extension, lateral bending and axial rotation. Six surgical constructs were compared between the groups and with intact condition, respectively. RESULTS: The six fixed modes significantly increased stability compared with both the intact and destabilization group in flexion-extension, lateral bending and axial rotation (p < .05). In extension, BPS + CR and BLS + CR showed greater stability than BLS + PR (p < .05). During flexion, the six fixation methods showed no statistical significance (p > .05). In left lateral bending, stability of the other five screw rod fixation techniques significantly increased when compared with BLS + PR (p < .05). In the right lateral bending direction, the stability of BLS + PR was worse than that of BPS + CR and BPS + PR (p < .05). In the left axial rotation, stability of BLS + CR, LPRLS + CR and BPS + CR was greater than that of BLS + PR, LPRLS + PR and BPS + PR (p < .05). In the right axial rotation, the stability of BPS + CR and BLS + CR was greater than that of BLS + PR (p < .05). CONCLUSION: The six investigated fixation methods provide sufficient biomechanical stability. The crossed rod configuration can further enhance the axial rotation stability of the screw rod system, which consists of C1 bilateral pedicle and C2 pedicle, or C2 lamina screws. The crossed rod can also improve the stability of the screw rod system made up of C1 bilateral pedicle and C2 lamina screws in lateral bending and extension. The crossed rod configuration is reliable and provides superior stability for clinical application.

Surgical treatment for basilar invagination with irreducible atlantoaxial dislocation: transoral atlantoaxial reduction plate fixation vs occipitocervical fixation.

BACKGROUND: Transoral atlantoaxial reduction plate (TARP) fixation or occipitocervical fixation (OF) is an effective treatment for basilar invagination (BI) with irreducible atlantoaxial dislocation (IAAD). But, all current clinical studies involved a single surgical procedure. The clinical effects of TARP and OF operation for BI with IAAD have yet to be compared. We therefore present this report to compare the treatment of TARP and OF procedure for BI with IAAD. METHODS: Fifty-six patients with BI with IAAD who underwent TARP or OF operation from June 2011 to June 2017 were retrospectively analyzed. Among these, 35 patients underwent TARP operation (TARP group), and 21 patients underwent OF operation (OF group). We compared the difference of clinical, radiological, and surgical outcomes between the TARP and OF groups postoperatively. RESULTS: Compared with OF group, the operative time and blood loss in TARP group were lower. There was no statistical difference in the atlantodental interval (ADI), clivus canal angle (CCA), cervicomedullary angle (CMA), distance between the top of the odontoid process and the Chamberlain line (CL) and Japanese Orthopaedic Association (JOA) score between the TARP and OF groups preoperatively, but the improvements of these parameters in the TARP group were superior to those in the OF group postoperatively. The fusion rates were higher in the TARP group than those in the OF group at the early stage postoperatively. CONCLUSIONS: TARP and OF operations are effective surgical treatment for BI with IAAD, but the performance of reduction and decompression and earlier bone fusion rates of TARP procedure are superior to those of OF.

Transoral intraarticular cage distraction and C-JAWS fixation for revision of basilar invagination with irreducible atlantoaxial dislocation.

BACKGROUND: The revision surgery of basilar invagination (BI) with irreducible atlantoaxial dislocation (IAAD) after a previous occipitocervical fusion (OCF) is challenging. Transoral revision surgery has more advantages than a combined anterior and posterior approach in addressing this pathology. The C-JAWS is a cervical compressive staple that has been used in the lower cervical spine with many advantages. Up to now, there is no report on the application of C-JAWS in the atlantoaxial joint. We therefore present this report to investigate the clinical outcomes of transoral intraarticular cage distraction and C-JAWS fixation for revision of BI with IAAD. METHODS: From June 2011 to June 2015, 9 patients with BI and IAAD were revised by this technique after previous posterior OCF in our department. Plain cervical radiographs, computed tomographic scans and magnetic resonance imaging were obtained pre- and postoperatively to assess the degree of atlantoaxial dislocation and compression of the cervical cord. The Japanese Orthopedic Association (JOA) score was used to evaluate the neurological function. RESULTS: The revision surgeries were successfully performed in all patients. The average follow-up duration was 18.9 ± 7.3 months (range 9-30 months). The postoperative atlas-dens interval (ADI), cervicomedullary angle (CMA), distance between the top of the odontoid process and the Chamberlain line (CL) and JOA score were significantly improved in all patients (P < 0.05). Bony fusion was achieved after 3-9 months in all cases. No patients developed recurrent atlantoaxial instability. CONCLUSIONS: Transoral revision surgery by intraarticular cage distraction and C-JAWS fixation could provide a satisfactory outcome for BI with IAAD after a previous unsuccessful posterior operation.

Motion-preserving treatment of unstable atlas fracture: transoral anterior C1-ring osteosynthesis using a laminoplasty plate.

BACKGROUND: C1-ring osteosynthesis is a valid alternative to posterior C1-C2 or C0-C2 fusion to preserve important C1-C2 motion in the treatment of unstable atlas fractures. Nevertheless, the fixation instruments used in current studies for transoral anterior C1-ring osteosynthesis were not suitable for anterior anatomy of the atlas or did not have reduction mechanism. We therefore present this report to investigate preliminary clinical effects of transoral anterior C1-ring osteosynthesis using a laminoplasty plate in unstable atlas fractures. METHODS: From January 2014 to December 2017, 13 patients with unstable atlas fractures were retrospectively reviewed. All patients were treated with transoral anterior C1-ring osteosynthesis using a laminoplasty plate. Pre- and postoperative images were obtained to assess reduction of the fracture, internal fixation placement, and bone union. Neurological function, range of motion, and pain levels were evaluated clinically on follow-up. RESULTS: The surgeries were successfully performed in all cases. The average follow-up duration was 16.6 ± 4.4 months (range 12-24 months). One patient suffered screw loosening after operation and underwent replacement operation subsequently. Satisfactory clinical outcomes were achieved in all patients with ideal fracture reduction, reliable plate placement, well-preserved range of motion, and neck pain alleviation. All patients achieved bone union of fractures without loss of reduction or implant failure or C1-C2 instability during the follow-up. No vascular or neurological complication was noted during the operation and follow-up. CONCLUSIONS: Transoral anterior C1-ring osteosynthesis using a laminoplasty plate is a effective surgical treatment for unstable atlas fractures. This technique has a ingenious reduction mechanism, and can provide satisfactory bone union and preservation of C1-C2 motion.

[Comparison of radiological changes after Halo-pelvic traction with posterior spinal osteotomy versus simple posterior spinal osteotomy for severe rigid spinal deformity].

OBJECTIVE: To compare the changes of scoliosis and kyphosis angles after Halo-pelvic traction with posterior spinal osteotomy versus simple posterior spinal osteotomy for severe rigid spinal deformity. METHODS: A clinical data of 28 patients with severe rigid spinal deformity between January 2015 and November 2017 was retrospectively analyzed. Sixteen patients were treated by Halo-pelvic traction with posterior spinal osteotomy (group A) and 12 patients were treated with posterior spinal osteotomy only (group B). There was no significant difference between the two groups ( P>0.05) in gender, age, body mass index, and preoperative pulmonary function, coronal and sagittal Cobb angles, and flexibility. The operation time, intraoperative blood loss, and complications were recorded. The coronal and sagittal Cobb angles were measured on X-ray films before operation (before traction in group A), at 10 days after operation, at last follow-up in the two groups and after traction in group A. The improvement rate of deformity after traction in group A, the correction rate of deformity after operation, and the loss rate of correction at last follow-up were calculated. RESULTS: All patients were followed up 24-30 months (mean, 26.5 months). The operation time and intraoperative blood loss were significantly less in group A than in group B ( t=7.629, P=0.000; t=8.773, P=0.000). In group A, 1 patient occurred transient numbness of both legs during continuous traction and 2 patients needed ventilator support for more than 12 hours. In group B, 7 patients needed ventilator support for more than 12 hours, including 1 patient with deep incision infection. The incidence of complications was 18.75% (3/16) in group A and 58.33% (7/12) in group B, and the difference between the two groups was significant ( χ 2=4.680, P=0.031). The coronal and sagittal improvement rates of deformity after traction in group A were 40.47%±3.60% and 40.70%±4.20%, respectively. There was no significant difference between the two groups ( P>0.05) in the coronal and sagittal Cobb angles at 10 days after operation and at last follow-up, in the correction rate of deformity after operation, and in the loss rate of correction at last follow-up. CONCLUSION: For the severe rigid spinal deformity, Halo-pelvic traction with posterior spinal osteotomy and simple posterior spinal osteotomy can obtain the same orthopedic effect and postoperative deformity correction. However, the Halo-pelvic traction can shorten operation time, reduce blood loss and incidence of perioperative complications.