Effects of Cervical Fusion Surgery by Different Methods on Stability in Upper Cervical Spine with Jefferson Fracture / 医用生物力学

Objective To establish the finite element model of upper cervical vertebrae C0-3 with Jefferson fracture, and to analyze the influence of posterior atlantoaxial fusion (PSF) and occipitocervical fusion (OCF) on biomechanical properties of the vertebral body and mechanical conduction of the screw-rod system. Methods Based on CT images, the C0-3 segment Jefferson fracture model of human upper cervical spine was established. PSF, OCF1 and OCF2 internal fixation were performed according to surgical plan in clinic, and 50 N concentrated force and 1.5 N·m torque were applied to bottom of the occipital bone. The stress distribution and range of motion (ROM) of the cervical vertebral body, the maximum stress of the screw-rod system and the stress distribution of the intervertebral disc for C0-3 segment during flexion, extension, bending and rotation of the upper cervical spine were studied. Results Compared with PSF, the ROM of OCF1 and OCF2 vertebral bodies increased, and the stress of the nail rod decreased. OCF had a better fixation effect. Conclusions PSF, OCF1 and OCF2 fixation method can reduce the upper cervical ROM and restore stability of the upper cervical spine, which make stress distributions of the vertebral body and intervertebral disc tend to be at normal level. The research result can provide a theoretical basis for clinical surgery plan.

Influence of Atlantoaxial Fusion on Sagittal Alignment of the Occipitocervical and Subaxial spines in Os Odontoideum with Atlantoaxial Instability

STUDY DESIGN: Retrospective case analysis. PURPOSE: We hypothesized that larger the C1–C2 fusion angle, greater the severity of the sagittal malalignment of C0–C1 and C2–C7. OVERVIEW OF LITERATURE: In our experience, instances of sagittal malalignment occur at C0–C1 and C2–C7 following atlantoaxial fusion in patients with Os odontoideum (OO). METHODS: We assessed 21 patients who achieved solid atlantoaxial fusion for reducible atlantoaxial instability secondary to OO. The mean patient age at the time of the operation was 42.8 years, and the mean follow-up duration was 4.9 years. Radiographic parameters were preoperatively measured and at the final follow-up. The patients were divided into two groups (A and B) depending on the C1–C2 fusion angle. In group A (n=11), the C1–C2 fusion angle was ≥22°, whereas in group B, it was <22°. The differences in the radiographic parameters of the two groups were evaluated. RESULTS: At the final follow-up, the C1–C2 angle was increased. However, this increase was not statistically significant (18° vs. 22°, p=0.924). The C0–C1 angle (10° vs. 5°, p<0.05) and C2–C7 angle (22° vs. 13°, p<0.05) significantly decreased. The final C1–C2 angle was negatively correlated with the final C0–C1 and C2–C7 angles. The final C0–C1 angle (4° vs. 6°, p<0.05) and C2–C7 angle (8° vs. 20°, p<0.05) were smaller in group A than in group B. After atlantoaxial fusion, the C0–C1 range of motion (ROM; 17° vs. 9°, p<0.05) and the C2–C7 ROM (39° vs. 31°, p<0.05) were significantly decreased. CONCLUSIONS: We found a negative association between the sagittal alignment of C0–C1 and C2–C7 after atlantoaxial fusion and the C1–C2 fusion angle along with decreased ROM. Therefore, overcorrection of C1–C2 kyphosis should be avoided to maintain good physiologic cervical sagittal alignment.

One stage temporary atlantoaxial segmental fixation and reduction for Grauer type IIB dens fractures in teenagers / 中国骨伤

OBJECTIVE@#To assess the clinical results of one stage temporary atlantoaxial segmental fixation and reduction for Grauer type IIB dens fractures in teenagers.@*METHODS@#From February 2009 to April 2015, 19 teenagers with Grauer type IIB dens fractures not amenable to anteiror screw fixation were enrolled and treated using one stage temporary atlantoaxial segmental fixation and reduction without fusion. There were 14 males and 5 females, aged from 14 to 32 years with an average of (24.6±5.0 ) years. The internal fixation was removed after bone healing confirmed by CT scan. At the last follow-up (at least 1 year after internal fixation removal), dynamic CT was used to assess the atlantoaxial rotation activity. Visual analogue scale (VAS) was recorded before the first operation, before the second operation (removal of internal fixation) and at the last follow-up. Neck Disability Index(NDI) was used to evaluate the efficacy before the second operation (removal of internal fixation) and the last follow-up.@*RESULTS@#After operation, 2 patients developed the symptoms of occipital nerve stimulation such as numbness and pain in the occipitocervical region, and were treated with drugs such as dehydration and neurotrophic drugs, and the symptoms were relieved after 1 to 2 months. All the internal fixations were removed and all the patients were followed up more than 1 year, with time ranging from 18 to 25 months and an average of (21.47±2.41) months. The time of bone fusion after operation was 6 to 10 months with the mean of(8.21±1.27) months. Secondary surgical removal of internal fixation were performed immediately after fracture healing without internal fixation failure. The symptoms of neck pain improved significantly after operation, VAS score decreased from 6.74±0.65 before operation to 0.42±0.51 at the last follow-up after the second operation (removal of internal fixation), with statistically significant differences(<0.01). The NDI value decreased from (10.58±2.04)% before the second operation (removal of internal fixation) to (3.79±2.23)% at the last follow-up after the second operation (removal of internal fixation), with statistically significant difference(<0.01). At the last follow-up after the second operation (removal of internal fixation), dynamic CT showed that the unilateral rotation of the atlantoaxial spine reached (15.73±5.57)° to the left, (15.55±5.78)° to the right, and the overall rotation of the atlantoaxial spine was (31.28±10.71)°.@*CONCLUSIONS@#One stage temporary atlantoaxial segmental fixation and reduction for the treatment of Grauer type IIB dens fractures not amenable to anteiror screw fixation in teenagers can avoid the loss of atlantoaxial rotation function caused by atlantoaxial fusion, and to some extent retain the rotation activity of atlanto-axial joint.

Cold Allodynia after C2 Root Resection in Sprague-Dawley Rats

OBJECTIVE: The purpose of this study was to evaluate pain-related behaviors after bilateral C2 root resection and change in pain patterns in the suboccipital region in rats. METHODS: Male Sprague-Dawley rats were randomly assigned to three groups (n=25/group); näive, sham, and C2 resection. Three, 7, 10, and 14 days after surgery, cold allodynia was assessed using 20 μL of 99.7% acetone. c-Fos and c-Jun were immunohistochemically stained to evaluate activation of dorsal horn gray matter in C2 segments of the spinal cord 2 hours, 1 day, 7 days, and 14 days after surgery.

Cold Allodynia after C2 Root Resection in Sprague-Dawley Rats

OBJECTIVE: The purpose of this study was to evaluate pain-related behaviors after bilateral C2 root resection and change in pain patterns in the suboccipital region in rats.METHODS: Male Sprague-Dawley rats were randomly assigned to three groups (n=25/group); näive, sham, and C2 resection. Three, 7, 10, and 14 days after surgery, cold allodynia was assessed using 20 μL of 99.7% acetone. c-Fos and c-Jun were immunohistochemically stained to evaluate activation of dorsal horn gray matter in C2 segments of the spinal cord 2 hours, 1 day, 7 days, and 14 days after surgery.RESULTS: Three days after surgery, the response to acetone in the sham group was significantly greater than in the näive group, and this significant difference between the näive and sham groups was maintained throughout the experimental period (p < 0.05 at 3, 7, 10, and 14 days). Seven, 10, and 14 days after surgery, the C2 root resection group exhibited a significantly greater response to acetone than the näive group (p < 0.05), and both the sham and C2 resection groups exhibited significantly greater responses to acetone compared with 3 days after surgery. No significant difference in cold allodynia was observed between the sham and C2 root resection groups throughout the experimental period. Two hours after surgery, both the sham and C2 root resection groups exhibited significant increases in c-Fos- and c-Jun-positive neurons compared with the naive group (p=0.0021 and p=0.0358 for the sham group, and p=0.0135 and p=0.014 for the C2 root resection group, respectively). One day after surgery, both the sham and C2 root resection groups exhibited significant decreases in c-Fos -positive neurons compared with two hours after surgery (p=0.0169 and p=0.0123, respectively), and these significant decreases in c-Fos immunoreactivity were maintained in both the sham and C2 root resection groups 7 and 14 days after surgery. The sham and C2 root resection groups presented a tendency toward a decrease in c-Jun-positive neurons 1, 7, and 14 days after surgery, but the decrease did not reach statistical significance.CONCLUSION: We found no significant difference in cold allodynia and the early expression of c-Fos and c-Jun between the sham and C2 resection groups. Our results may support the routine resection of the C2 nerve root for posterior C1–2 fusion, but, further studies are needed.

Application of preoperatively vertebral artery CTA in screw setting of upper cervical spine / 局解手术学杂志

Objective To study the application of cervical vertebral artery CT angiography(CTA) preoperatively in the screw setting of upper cervical spine.Methods The data of 170 patients who underwent upper cervical spine surgery from January 2014 to December 2015 in our hospital were retrospectively analyzed,of whom 80 cases with typeⅡodontoid fractures,90 cases with atlantoaxial dislocation;20 cases were operated with occipitocervical fusion,150 cases treated with atlantoaxial fusion.Seventy-eight cases were examinated by cervical vertebral artery CTA before sugery(observation group) but the other 92 cases(control group).The rate of the vertebral arterial lesion between the two groups were compared.Results Six cases with vertebral artery injury in control group,the incidence of arterial injury was 7％;unilateral vertebral artery was found in 3 cases,small congenital development of left cervical vertebral artery in 5 case,abnormal branch in 5 cases.The rate of dysplasia was 17％,and the rate of vertebral artery injury was 0.The rate of vertebral artery injury in control group was higher than observation group,the difference was significant(P<0.05).Conclusion Vertebral artery CTA examination preoperatively may become a routine examination,in order to make the operator carefully evaluate the relationship between the vertebral artery with atlantoaxial vertebral,choose the accurate screw-setting and avoid the vertebral artery injury in the upper cervical spine surgery.

Comparison of Cervical Alignment and Clinical Outcomes in Patients with Os Odontoideum versus Non-Os Odontoideum after Atlantoaxial Fixation

OBJECTIVE: The purpose of this study was to compare the effect of atlantoaxial fixation on cervical alignment and clinical outcomes in patients with os odontoideum (OO) versus non-os odontoideum (non-OO). METHODS: A total of 119 patients who underwent atlantoaxial fixation for instability were identified between January 1998 and January 2014. Inclusion criteria included age more than 21 years and diagnosis of OO and non-OO. There were 22 OO patients, and 20 non-OO patients. Measuring the Oc–C1 Cobb angle, C1–2 Cobb angle, C2–7 Cobb angle, and C2–7 sagittal vertical axis (SVA) was assessed. Clinical outcome was assessment of suboccipital pain was determined using a visual analogue scale (VAS), and Japanese Orthopedic Association (JOA) scores were obtained in all patients pre- and postoperatively. RESULTS: The preoperative C1–2 angle in the OO group (26.02°±10.53°) was significantly higher than the non-OO group (p=0.04). After C1–2 fixation, the OO group had significantly higher kyphotic change in the C1–2 angle (ΔC1–2) (3.2°±7.3° [OO] vs. −1.46°±7.21° [non-OO]) (p=0.04), and higher decrease in postoperative C2–7 SVA (ΔC2–7 SVA) (5.64±11.56 mm [OO] vs. −0.51± 6.57 mm [non-OO]) (p=0.04). Both groups showed improvements in the health related quality of life (HRQOL) after surgery based on the VAS and JOA score (p < 0.001). CONCLUSION: After fixation, kyphotic angular change in atlantoaxial joint and decrease C2–7 SVA were marked in the OO group. Both the OO and non-OO groups improved in neurological function and outcome after surgery.

Repeated Complication Following Atlantoaxial Fusion: A Case Report

A patients with atlantoaixial instability and osodontoideum underwent atlantoaixial fusion (Harms and Melcher technique) with demineralized bone matrix. But, unfortunately, the both pedicle screws in C2 were fractured within 9 weeks follow-up periods after several suspected episode of neck hyper-flexion. Fractured screws were not contact to occipital bone in several imaging studies, but it could irritate the occipital bone when neck extension because the relatively close distance between the occipital bone and C1 posterior arch. The patient underwent revision operation with translaminar screw fixation with autologus iliac bone graft. Postsurgical course were uneventful except donor site pain, but the bony fusion was not satisfied after 4 months follow-up. The patient re-underwent revision operation in other hospital. Continuous complication after atlantoaixial fusion is rare, but the clinical course could be unlucky to patients. Postoperative immobilization could be important to prevent the unintended clinical course of patients.

The Clinical Experience of Computed Tomographic-Guided Navigation System in C1-2 Spine Instrumentation Surgery

OBJECTIVE: To identify the accuracy and efficiency of the computed tomographic (CT)-based navigation system on upper cervical instrumentation, particularly C1 lateral mass and C2 pedicle screw fixation compared to previous reports. METHODS: Between May 2005 and March 2014, 25 patients underwent upper cervical instrumentation via a CT-based navigation system. Seven patients were excluded, while 18 patients were involved. There were 13 males and five females; resulting in four degenerative cervical diseases and 14 trauma cases. A CT-based navigation system and lateral fluoroscopy were used during the screw instrumentation procedure. Among the 58 screws inserted as C1-2 screws fixation, their precise positions were evaluated by postoperative CT scans and classified into three categories : in-pedicle, non-critical breach, and critical breach. RESULTS: Postoperatively, the precise positions of the C1-2 screws fixation were 81.1% (47/58), and 8.6% (5/58) were of non-critical breach, while 10.3% (6/58) were of critical breach. Most (5/6, 83.3%) of the critical breaches and all of non-critical breaches were observed in the C2 pedicle screws and there was only one case of a critical breach among the C1 lateral mass screws. There were three complications (two vertebral artery occlusions and a deep wound infection), but no postoperative instrument-related neurological deteriorations were seen, even in the critical breach cases. CONCLUSION: Although CT-based navigation systems can result in a more precise procedure, there are still some problems at the upper cervical spine levels, where the anatomy is highly variable. Even though there were no catastrophic complications, more experience are needed for safer procedure.

Radiographic Analysis of Atlantoaxial Fusion for Atlantoaxial Instability: Comparison of Posterior wiring, Transarticular screw, Posterior screw-rod fixation

STUDY DESIGN: This is a retrospective study. OBJECTIVES: We wanted to clarify the association between the position of the atlantoaxial fusion angle and the change of the subaxial cervical spine alignment (SCA) and the reduction loss after atlantoaxial fusion (AAF) using the posterior wiring technique (PWT), transarticular screw fixation (TAF) and posterior screw-rod fixation (PSR) for treating atlantoaxial instability (AAI). SUMMARY OF LITERATURE REVIEW: There are not many studies on the change of the SCA and the reduction loss after AAF. MATERIALS AND METHODS: Thirty five patients underwent AAF for AAI from 1986 to 2008. The mean follow-up period was 59.5 months. The surgical techniques were divided into three groups, that is, PWT: 17 patients, TAS: 10 and PSR: 8. The causes of instability were transverse ligament rupture in 12 patients, rheumatoid arthritis in 11, Os odontoideum in 6 and nonunion of an odontoid fracture in 6. Plain radiographs were used to assess the atlanto-dental interval, the posterior arch-lamina angle, the change of the SCA and the time of fusion. RESULTS: Fusion was achieved in all the patients within 3.5 months (range: 3-5 months). The radiologic findings in the 5 PWT patients showed a reduction loss and 3 patients showed subaxial cervical kyphosis (SCK). The TAS group had no reduction loss or SCK. The PSR group had no reduction loss and one patient showed SCK. A statistically significant reduction loss and SCK occurred in the group in which there was a posterior arch-laminar angle greater than 10 degrees before and after surgery. CONCLUSIONS: For the treatment of AAI, the position of the AAF is associated with the change of the postoperative SCA. The preoperative lodortic position of C1-2 should be maintained to prevent the change of the SCA.

C1-2 Fixation Using Polyaxial Screws and Rods Assisted by Computer Simulation for Revision of Failed Posterior Fusion: A Technical Report / 대한정형외과학회잡지

Segmental C1-2 screw fixation using C1 lateral mass screws and C2 pedicle screws is a technically demanding procedure which can cause injuries to the vertebral artery or neural structures as well as massive bleeding from the epidural venous plexus. In particular, this procedure is more difficult in revision cases because of the lack of normal anatomical landmarks, adhesion, and bleeding. The authors report a case of a patient in whom preoperative surgical simulation and planning using computer software was very helpful in the direct screwing of the atlas and axis for a revision of atlantoaxial fusion.

Computed Tomographical Evaluation of C1-2 for Transarticular Posterior Screw Fixation / 대한정형외과학회잡지

PURPOSE: To avoid neurovascular injuries and to establish the ideal trajectory of screw insertion, a computed tomographical evaluation was conducted. MATERIALS AND METHODS: Twenty volunteers without cervical disease were employed for this study. Axial and oblique CT scans were selected for evaluation. Oblique CT scans were obtained in the direction of provisional screw insertion, starting from the junction of the lamina and the inferior articular facet of the axis and extending to the center of anterior tubercle of the atlas. In the axial and oblique reconstructed views, the screw length, the diameters of the medial and lateral cortexes of the isthmus, the vertical distance, and the angle of C1 were measured. RESULTS: The screw lengths averaged 37.6 mm (35.1-40.5 mm) in males and 37.2 mm (33.6-43.4 mm) in females. The diameters of the medial cortex of the isthmus were 4.3 mm (3.3-5.2 mm) in males and 4.0 mm (2.8-5.6 mm) in females. No measurement was statistically different between males and females. CONCLUSION: Due to individual variations of atlantoaxial anatomy, especially in terms of the size of cortical diameter of the isthmus, 3-D reconstruction CT is a useful tool for planning transarticular C1-2 screw insertion.

Synovial Cyst of Transverse Ligament of Axis in a Patient with Os Odontoideum and Atlantoaxial Instability: A Case Report / 대한척추외과학회지

STUDY DESIGN: A case report and review of the literature. OBJECTIVES: To describe the diagnosis and successful treatment of the synovial cyst arising from the transverse ligament in a patient with Os odontoideum and atlantoaxial instability. SUMMARY OF LITERATURE REVIEW: Synovial cyst arising from the transverse ligament of the axis is extremely rare and thought to be attributed to degenerative changes of the C1-C2 facet joints or microtraumas. Direct excision of the cyst is the only treatment method described in previous reports. MATERIALS AND METHODS: A case of synovial cyst arising from the transverse ligament of the axis in a 45-year-old man with Os odontoideum and atlantoaxial instability was managed with posterior atlantoaxial fusion alone. The characteristic MRI findings and surgical treatment, and related literature are reviewed. RESULTS: MRI of the cervical spine showed a large cystic mass located at the transverse ligament of the axis which was com-pressing the spinal cord near the C1-C2 junction: the images showed a low signal intensity on T1WI; high signal intensity on T2WI; and rim enhancement with no internal enhancement on Gadolinium enhanced T1WI. The spontaneous resolution of the cyst was identified on the follow-up MRI taken at 3 months after operation and clinical improvement was achieved. CONCLUSIONS: The MRI findings of spontaneous resolution of synovial cyst arising from the transverse ligament of the axis after posterior atlantoaxial fusion alone suggest that stable fusion rather than direct excision of the cyst should be considered over the surgical option when the location of the cyst is difficult or dangerous to approach surgically.

Anatomical Suitability of Posterior C1/2 Transarticular Screw Fixation in Korean

Although C1-C2 transarticular screw fixation has become a popular surgical method of treating atlantoaxial instability, we remain concerned about the potential for injury to the vertebral artery. Because of the lack of an objective measuring method, surgical unsuitability has been decided on the basis of individual experiences as reported in 18-23% of cases. In this study, the point of screw intersection(the passing points) on the superior articular surface of C2 were measured and the directions of these were thus objectified. Sixty-four healthy volunteers underwent 1mm fine-slice C1-C2 CT scanning, and sagittal images were reconstructed at 3.5mm(3.5mm lateral image) and 6mm(6mm lateral image) lateral to the spinal canal. The C1/2 transarticular screw trajectories making the longest paths or violating the transverse foramen(dangerous trajectory) were drawn and the distance from their points of screw intersection on the superior articular surface of C2 were measured from the posterior rim of the superior articular surface of C2. When the space available for screw(SAS) posterior to the passing point of the dangerous trajectory was equal to or less than 3.5mm(major diameter of the commonly used screw), the case was considered unacceptable, when SAS was over 3.5mm but equal to or less than 4.5mm, screw placement were considered risky. The trajectories made the longest paths when they passed 3.6+/-1.6mm(mean+/-S.D.) and 2.8+/-1.7mm(mean+/-S.D.) anterior to the posterior rim of the posterior articular surface of C2 as seen on 3.5mm lateral images and 6mm lateral images, respectively. While four of 64 cases(6.3%) were unilaterally unacceptable or risky on 3.5mm lateral images, 21 cases(32.8%) were unacceptable or risky on 6mm lateral images(unilateral, 15cases; bilateral, 6 cases). When the trajectories inclined forward to 0%, 25%, 50%, 75% and 100% points of AP diameter of the superior articular surface of C2 from the posterior rim, the respective risks of the involvement of the transverse foramen increased to 0.78%, 1.5%, 25%, 74% and 100%, as seen on 3.5mm lateral images and 10.9%, 14%, 62.5%, 95% and 100%, on 6mm lateral images.