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Clinical effect and prognosis of transoral or endoscope-assisted transoral release for irreducible atlantoaxial dislocation: A retrospective cohort study

BackgroundThe clinical applications of endoscope-assisted transoral release for irreducible atlantoaxial dislocations are limited. This study aimed to investigate the clinical effect and prognostic factors of traditional and endoscope-assisted transoral release, as well as posterior reduction and fixation, in treating irreducible atlantoaxial dislocations. Materials and methodsWe conducted a retrospective study on 59 patients with irreducible atlantoaxial dislocation who underwent either traditional or endoscope-assisted transoral release, posterior fixation, and fusion between January 2018 and January 2023. Various data, including surgical time, blood loss, drainage volume, oral intake, hospital stay, complications, and neurological status (assessed by the Japanese Orthopedic Association [JOA] score and Oswestry Disability Index [ODI]), were recorded. Imaging parameters such as the atlantodontoid interval (ADI), space available for the cord (SAC), and cervicomedullary angle (CMA) were analyzed and compared. In addition, the correlation between ODI, JOA and patient age, course of disease, preoperative ADI, SAC and CMA were analyzed. ResultsNo significant differences were observed in age, sex, BMI, preoperative ADI, preoperative SAC, or preoperative CMA. All patients achieved excellent reduction with no significant differences between the two groups. Patients in the endoscopic group experienced significantly reduced blood loss, earlier oral intake, and shorter hospital stays compared to those in the open group (P < 0.05). The ODI and JOA scores improved significantly in both groups at 1, 6, 12, 18, and 24 months postoperatively (P < 0.05). Postoperative ADI, SAC, and CMA values in both groups were significantly better than preoperative values (P < 0.001). The patient age, course of disease and the preoperative ADI were negatively correlated with the postoperative ODI and the JOA improvement ratio (P < 0.01), and the preoperative SAC and preoperative CMA had positive correlations with the postoperative ODI and the JOA improvement ratio (P < 0.01) at 6, 12 and 24 months postoperatively. ConclusionPatient age, course of disease, preoperative ADI, SAC and CMA are correlated with the operative prognosis of irreducible atlantoaxial dislocation. The endoscope-assisted transoral approach, compared to the traditional transoral approach, is minimally invasive, resulting in less operative blood loss, earlier oral intake and a shorter length of hospital stay, which could be offered as an alternative for irreducible atlantoaxial dislocation.

Surgical treatment of craniovertebral junction instability in children with Down syndrome: a systematic review.

Down syndrome (DS) affects 1 in 700 live births and approximately one-third of patients develop craniovertebral junction (CVJ) instability, diagnosed by clinical examination and radiological measures such as the atlantodens interval (ADI) and space available for the cord (SAC). Patients with symptomatic CVJ instability are at increased risk for spinal cord injury. There are no guidelines for surgical management of CVJ instability in DS, the existing literature is sparse, and there is a lack of consistent pediatric data. This systematic review aimed to synthesize practice patterns of the surgical management of CVJ stability in pediatric DS patients to facilitate future standardization of care. Peer-reviewed studies reporting surgical management of CVJ instability in pediatric DS patients were systematically reviewed. Inclusion criteria were studies reporting primary data on patients younger than 18 years with DS, who had CVJ instability evaluation and underwent surgical treatment. Bias risk was assessed. Descriptive statistics of the independent patient data were presented. Interval variables were analyzed using the Wilcoxon rank-sum test. Of 1056 records, 38 studies were included. Of the included patients, 169 (6%) underwent surgery. The surgical indication was symptomatic, radiologically confirmed CVJ instability in 81% of the patients, presenting with myelopathy (30%), weakness (25%), abnormal gait (24%), torticollis (15%), and neck pain (14%). A cutoff of ADI ≥ 4 mm or SAC ≤ 14 mm, cord compression, cord signal change, and anomalous bony anatomy were used in diagnosing CVJ instability. Surgical approaches focused on internal fixation with posterior occipitocervical or atlantoaxial instrumented fusion in 57% and 44% of patients, respectively. Autograft, wiring, and allograft constructs were used in 48%, 45%, and 9% of patients. Anterior cervical approaches were performed in 6% of patients. Preoperative and postoperative external orthoses were used in approximately 50% of patients. The surgical mortality rate was 3%, and the complication rate was 36%. Assessment of CVJ instability in DS is based on radiographic and clinical factors. Surgery is recommended if symptoms are present, and the procedure type depends on patient factors, degree of instability, anomalous bony anatomy, and reduction results to relieve cord compression. Most commonly, posterior instrumented fusion is used. However, further research is required to determine the strength of evaluation methods, create standardized guidelines for evaluation and surgical treatment, and investigate the long-term results of different surgical techniques.

Spinal Canal and Spinal Cord in Rat Continue to Grow Even after Sexual Maturation: Anatomical Study and Molecular Proposition.

Although rodents have been widely used for experimental models of spinal cord diseases, the details of the growth curves of their spinal canal and spinal cord, as well as the molecular mechanism of the growth of adult rat spinal cords remain unavailable. They are particularly important when conducting the experiments of cervical spondylotic myelopathy (CSM), since the disease condition depends on the size of the spinal canal and the spinal cord. Thus, the purposes of the present study were to obtain accurate growth curves for the spinal canal and spinal cord in rats; to define the appropriate age in weeks for their use as a CSM model; and to propose a molecular mechanism of the growth of the adult spinal cord in rats. CT myelography was performed on Lewis rats from 4 weeks to 40 weeks of age. The vertical growth of the spinal canal at C5 reached a plateau after 20 and 12 weeks, and at T8 after 20 and 16 weeks, in males and females, respectively. The vertical growth of the C5 and T8 spinal cord reached a plateau after 24 weeks in both sexes. The vertical space available for the cord (SAC) of C5 and T8 did not significantly change after 8 weeks in either sex. Western blot analyses showed that VEGFA, FGF2, and BDNF were highly expressed in the cervical spinal cords of 4-week-old rats, and that the expression of these growth factors declined as rats grew. These findings indicate that the spinal canal and the spinal cord in rats continue to grow even after sexual maturation and that rats need to be at least 8 weeks of age for use in experimental models of CSM. The present study, in conjunction with recent evidence, proposes the hypothetical model that the growth of rat spinal cord after the postnatal period is mediated at least in part by differentiation of neural progenitor cells and that their differentiation potency is maintained by VEGFA, FGF2, and BDNF.

Changes in retro-odontoid mass after upper cervical spine surgery

A non-neoplastic mass posterior to the dens is termed a retro-odontoid mass (R-OM). This retrospective study evaluated radiographic and clinical outcomes and R-OM changes after upper cervical spine surgery. This study included 69 patients who underwent upper cervical spine surgery, including atlantoaxial fusion, occipitocervical fusion, or decompression. All patients underwent preoperative magnetic resonance imaging (MRI). Six-month follow-up MRI examinations were performed in 30 patients who had preoperative R-OMs. Radiographic outcomes of the anterior and posterior atlantodental intervals were measured using X-rays and computed tomography. The R-OM and space available for the cord (SAC) were measured using MRI. Clinical outcomes were evaluated using neck and arm pain visual analog scales, the Japanese Orthopedic Association score, the neck disability index, and the patient-reported subjective improvement rate. The anterior atlantodental interval decreased, while the posterior atlantodental interval and SAC increased postoperatively. Among the clinical outcomes, the neck and arm pain and the neck disability index decreased postoperatively, while the Japanese Orthopedic Association score increased. All clinical and radiographic outcomes improved postoperatively. The R-OM either decreased in size or disappeared after fusion surgery in all cases, except in one patient who underwent decompression surgery. In conclusion, stabilization through fusion surgery is essential for treating R-OM.

Measurement of Space Available for Cord of Cervical Spine in MRI

Introduction: Cervical spinal stenosis has been established as a predisposing factor of cervical myelopathy and is associated with cord injury. Space available for the cord (SAC) can be used as an indicator of spinal stenosis.&#x0D; Methods: This study was performed on patients referred for MRI examinations of the cervical spine for various clinical indications to a tertiary centre in Nepal. Data were collected for a period of four months from January to April after IRB approval. Convenience sampling was employed and a total of 72 examinations were included. Data were obtained from the 1.5T Magnetom Amira Siemens MRI scanner. Sagittal diameters of the spinal canal and spinal cord were traced and measured from C3 to the C7 vertebra. The space available for the spinal cord (SAC) was calculated by subtracting the sagittal cord diameter from the corresponding sagittal canal diameter.&#x0D; Results: The average space available for cord was 4.48mm±1.04mm at C3, 4.44mm±1.03mm at C4, 4.63mm±1.01mm at C5, 5.11mm±1.07mm at C6, 5.87mm±1.14mm at C7 vertebral level. The SAC value was not significant according to gender and age (p&gt;0.05).&#x0D; Conclusions: The smallest SAC value was detected at the C4 vertebral level with a mean value of 4.44mm and the greatest value was at C7 vertebral level with a mean value of 5.87mm. There was no significant gender difference in SAC values.&#x0D;

Successful Motor Evoked Potential Monitoring in Cervical Myelopathy : Related Factors and the Effect of Increased Stimulation Intensity.

ObjectiveIntraoperative neurophysiological monitoring (IONM) has been widely used during spine surgery to reduce or prevent neurologic deficits, however, its application to the surgical management for cervical myelopathy remains controversial. This study aimed to assess the success rate of IONM in patients with cervical myelopathy and to investigate the factors associated with successful baseline monitoring and the effect of increasing the stimulation intensity by focusing on motor evoked potentials (MEPs). MethodsThe data of 88 patients who underwent surgery for cervical myelopathy with IONM between January 2016 and June 2018 were retrospectively reviewed. The success rate of baseline MEP monitoring at the initial stimulation of 400 V was investigated. In unmonitorable cases, the stimulation intensity was increased to 999 V, and the success rate final MEP monitoring was reinvestigated. In addition, factors related to the success rate of baseline MEP monitoring were investigated using independent t-test, Wilcoxon rank-sum test, chi-squared test, and Fisher’s exact probability test for statistical analysis. The factors included age, sex, body mass index, diabetes mellitus, smoking history, symptom duration, Torg-Pavlov ratio, space available for the cord (SAC), cord compression ratio (CCR), intramedullary increased signal intensity (SI) on magnetic resonance imaging, SI length, SI ratio, the Medical Research Council (MRC) grade, the preoperative modified Nurick grade and Japanese Orthopedic Association (JOA) score. ResultsThe overall success rate for reliable MEP response was 52.3% after increasing the stimulation intensity. No complications were observed to be associated with increased intensity. The factors related to the success rate of final MEP monitoring were found to be SAC (p<0.001), CCR (p<0.001), MRC grade (p<0.001), preoperative modified Nurick grade (p<0.001), and JOA score (p<0.001). The cut-off score for successful MEP monitoring was 5.67 mm for SAC, 47.33% for the CCR, 3 points for MRC grade, 2 points for the modified Nurick grade, and 12 points for the JOA score. ConclusionIncreasing the stimulation intensity could significantly improve the success rate of baseline MEP monitoring for unmonitorable cases at the initial stimulation in cervical myelopathy. In particular, the SAC, CCR, MRC grade, preoperative Nurick grade and JOA score may be considered as the more important related factors associated with the success rate of MEP monitoring. Therefore, the degree of preoperative neurological functional deficits and the presence of spinal cord compression on imaging could be used as new detailed criteria for the application of IONM in patients with cervical myelopathy.

Anterior release without odontoidectomy for irreducible atlantoaxial dislocation: transoral or endoscopic transnasal?

To compare transoral and endoscopic transnasal anterior release without odontoidectomy and posterior reduction and fixation to treat irreducible atlantoaxial dislocation (IAAD). From June 2006 to January 2017, 35 consecutive patients with IAAD underwent transoral (Tr-Oral group) or endoscopic transnasal (Tr-Nasal group) release and posterior fixation and fusion in our department. Clinical neurological recovery (Japanese Orthopedic Association (JOA) score) and radiological reduction parameters including atlantodontoid interval (ADI), space available for the cord (SAC) and cervicomedullary angle (CMA) were analyzed and compared. The operation duration, blood loss, length of intensive care unit (ICU)/hospital stay and complications were recorded. All 35 patients (18 and 17 patients in the Tr-Oral and Tr-Nasal groups, respectively) were followed up for a mean of 36.4months (range, 21-60months). All patients achieved excellent anatomical reduction and clinical neurological recovery, with no significant differences between the two groups. The JOA score, ADI, SAC and CMA were not significantly different between the two groups at various postoperative points. Although the Tr-Oral group had shorter operation time and less blood loss than the Tr-Nasal group, the Tr-Nasal group tended to have a significantly shorter hospital/ICU stay, earlier extubation and earlier oral intake than the Tr-Oral group. The transoral and endoscopic transnasal approaches can achieve equivalent release and reduction effects when treating IAAD. Compared to the transoral approach, the endoscopic transnasal route is less invasive with earlier extubation and oral intake, shorter hospital/ICU stays and lower medical costs, which is conducive to enhancedrecoveryafter surgery.

Bilateral atlantoaxial lamina hook and atlantoaxial joint space screw for the treatment of acute type I transverse ligament injury in school-age children

To evaluate the effect of bilateral atlantoaxial lamina hook and atlantoaxial joint space screw combined with autologous iliac bone graft on atlantoaxial dislocation caused by acute type I transverse ligament injury in school-age children. From February 2006 to February 2019, 8 school-age children with atlantoaxial dislocation caused by acute type I transverse ligament injury were systematically reviewed, including 6 males and 2 females; aged 9 to 12 years old; 8 acute injuries included 4 high-level falls, 2 car accidents and 2 sports injuries; the atlantoaxial interval(ADI) was 5 to 8 mm. Eight cases presented with pain, stiffness, numbness and cervical spine dysfunction in different degrees. Two of them were accompanied by nerve compression and ASIA grade D. The preoperative C₁,₂ angle averaged 20.7° to 23.4°. All patients received cranial traction and surgical treatment after complete reduction or atlantoaxial reduction. The changes of Japanese Orthopaedic Association(JOA) score, space available for the cord(SAC), neck disability index(NDI), ADI, ASIA classification(ASIA) injury classification(1992) and C₁,₂ angle before and after treatment were observed. The average follow-up time was 8 to 156 months. Clinical and radiological follow-up showed that the atlantoaxial joint was completely relieved, the reduction was satisfactory and the arthrodesis was stable. Nerve and vascular injuries associated with this technique were not observed. JOA score, SAC, NDI, C₁,₂ angle of the last follow-up of the children were significantly improved. Two children of ASIA grade D recovered to grade E. Bilateral atlantoaxial lamina hook and atlantoaxial joint space screw combined with autologous iliac bone graft is simple, less bleeding, strong stability and high fusion rate. It is an ideal surgical procedure for acute type I transverse ligament injury with atlantoaxial dislocation in school-age children.

Clinical implications morphometric study of the cervical spine on MRI

Degenerative changes, history of trauma or inflammation usually progressed to cervical spinal canal stenosis. This condition leads to cervical spondylosis neuropraxia and cervical spondylotic myelopathy (CSM). SAC (space available for the cord) value is important to understand the symptoms of spinal cord compression in cervical canal stenosis. The aim of our study is to establish cervical spinal canal morphometry in Western Maharashtra population observed by MRI of cervical region.70 subjects aged between 18-70 years. The sagittal vertebral body diameter, the sagittal spinal canal diameter and the sagittal spinal-cord diameter were measured at the C3 - C7 level. The SAC was determined. For each variable a two-way ANOVA was performed, sagittal canal diameter, sagittal spinal cord diameter and SAC were significant with p-value P&lt; 0.0001**. Mean vertebral body diameters observed were 1.49-1.51. Values of SAC observed were C3-1.5 cm, C4- 1.51cm, C5- 1.49cm, C6- 1.5cm, C7- 1.49cm. Average sagittal spinal canal diameter from C3-C7 was 14.1± 1.3 mm. The range of SAC was between 6.4-9.5mm, least at the C5 level. We conclude that subjects in our study do not have an increased risk of spinal cord compression.

Dynamic MRI in the Evaluation of Atlantoaxial Stability in Pediatric Down Syndrome Patients

Background/Aims: Down syndrome is the most common inherited disorder. Some patients develop atlantoaxial instability. Existing screening guidelines were developed prior to availability of MRI. We present predictors for deficit using dynamic MRI of the craniocervical junction. Methods: A retrospective review of Down syndrome patients from 2001 to 2015 was carried out. Patients were considered symptomatic if they had clinical deficits or signal change on MRI. Measurements were taken at the atlantoaxial junction and structural abnormalities noted. Analysis was performed with SPSS. Results: A total of 36 patients were included. Patients averaged 93 months of age with a follow-up of 57 months. No asymptomatic patients developed myelopathy during follow-up. During dynamic imaging, symptomatic patients had greater changes in space available for the cord (SAC) (5.2 vs. 2.7 mm; p < 0.001) and atlantodental interval (ADI) (2.8 vs. 1.3 mm; p = 0.04). These patients were also more likely to have a bony anomaly (50 vs. 13%; p = 0.03). Conclusion: This study characterizes the range of motion seen on dynamic MRI and provides parameters that can be used to distinguish patients at risk for neurologic injury. Changes greater than 3 mm in ADI or 5 mm in SAC during dynamic MRI or any bony abnormality warrants further investigation. Patients without these features may be able to avoid an unnecessary intervention.

Secondary posterior internal fixation after transoral anterior atlantoaxial release under 3D operative microscopy for irreducible atlantoaxial dislocation

Objective To explore the clinical efficacy of secondary posterior internal fixation after transoral anterior atlantoaxial release under 3D operative microscopy for treatment of irreducible atlantoaxial dislocation. Methods From January 2014 to May 2016, 12 patients with irreducible atlantoaxial dislocation were treated with secondary posterior internal fixation after transoral anterior atlantoaxial release under 3D operative microscopy in our hospital. They were 7 males and 5 females, with an average age of 37.1 years (from 25 to 54 years). The efficacy was analyzed in terms of their visual analogue scale (VAS), Japanese Orthopaedic Association (JOA) scoring, improvement rate of neurological function, American Spinal Injury Association (ASIA) grading, atlas-dens interval (ADI), space available for the cord (SAC) and cervicomedullary angle (CMA) before and one year after operation. Results The patients were followed up for more than one year.All the atlantoaxial joints obtained anatomic reduction. Their preoperative values of VAS (5.73±1.36 points), JOA score (9.03±2.12 points), ADI (8.34±1.12 mm), SAC (9.53±0.69 mm) and CMA (121.23°±4.32°) were significantly improved one year after operation (1.21±0.63 points, 14.32±2.51 points, 2.83±0.36 mm, 14.23±1.22 mm and 153.53°±9.25°, respectively) (P<0.05). The improvement rate of neurological function increased gradually with the postoperative time, reaching 94.14%±5.11% one year after operation. The postoperative ASIA grading was significantly improved too one year after operation (P<0.05). Conclusion Secondary posterior internal fixation after transoral anterior atlantoaxial release under 3D operative microscopy may lead to fine clinical efficacy one year after operation for patients with irreducible atlantoaxial dislocation. Key words: Atlantoaxial joint; Dislocation; Skeletal tracting reposition; Posterior fixation

Guidance value of TOI classification for treatment of traumatic T-type atlantoaxial dislocation

Objective To investigate the guidance value of TOI classification in treating traumatic T-type atlantoaxial dislocation (ADD). Methods A retrospective case series study was made on 32 cases of traumatic TOI T-type ADD treated between January 2012 and December 2015. There were 19 males and 13 females, aged (38.4±14.7)years. Fifteen cases of T1-type underwent external fixation or internal fixation without fusion, while 17 cases of T2-type underwent internal fixation with fusion. Symon-Lavender clinical standard, Japanese orthopedic association score (JOA), visual analogue scale (VAS), atlas-dens interval (ADI) and space available for the cord (SAC) were used to evaluate the therapeutic effect. Results Patients were followed up for 6-54 months (mean, 32.4 months). At final follow-up, ADI was decreased to (2.3±1.4)mm from preoperative (5.6±1.6)mm, but SAC was increased to (15.4±1.9)mm from preoperative (12.0±2.9)mm (P<0.01). At final follow-up, cervical axial rotation range of motion was 102°-154° in T1-type cases and 57°- 93° in T2-type cases. Range of motion for atlantoaxial joint was preserved in T1-type cases, but lost in T2-type cases. According to the Symon-Lavender clinical standard, there were 14 cases of mild disability, nine moderate disability, eight severe disability and one extremely severe disability before operation; there were 21 cases of mild disability, nine moderate disability and two severe disability at last follow-up. Significant difference was observed in the grades according to the Symon-Lavender clinical standard before operation and at last follow-up (P<0.05). At last follow-up, JOA score was increased to (14.6±2.9)points from preoperative (9.9±3.2)points, and VAS was decreased to (2.7±1.3)points from preoperative (6.0±1.6)points (P<0.01). Conclusions By using TOI classification, reconstruction of stability and improved neurological function can be achieved in treatment of traumatic T-type atlantoaxial dislocation. Non-fusion treatment of T1-type atlantoaxial dislocation can preserve range of motion for atlantoaxial joint. Key words: Atlanto-axial joint; Dislocations; Classification

Magerl technique for children atlantoaxial rotatory subluxation

Objective To discuss the feasibility and prognosis of magerl technique for children. Atlantoaxial Rotatory Subluxation. Methods 63 patients with Atlantoaxial Rotatory Subluxation were treated in our hospital, and 16 of whom were treated with bilateral C1, 2 posterior transarticular screw fixation and fusion. All cases aged from 8 to 14, with an average age of 11±2.3 years old. According to Fielding classification, 10 cases were in type II, and 6 in type III. 1 patient showed dizziness, 11 patients showed obvious appearance of deviation of head and neck; 14 patients showed varying degrees of occipito-cervical pain, and one patient showed incomplete paralysis. All patients had undergone Halo traction, then the Magerl surgery for atlantoaxial fixation fusion. Through follow-up and photograph of atlantoaxial mouth opening, lateral cervical X-ray and atlantoaxial 3D CT, the screw position and bone graft fusion were evaluated. The clinical and radiological outcomes were evaluated according to the Symon and Lavender clinical standard, the imaging index space available for the cord (SAC), and the atlas-dens interval (ADI). Results All cases were followed up for 3 to 98 months (mean 38±14.6 months). All patients had completed the bilateral UCSS screw fixation, and the symptoms were improved significantly, without neurological symptoms aggravated or complications such as neurovascular injury. All UCSS screw position through the atlantoaxial joint was accurate, without atlanto occipital joint activity limitation. All patients got bony fusion 3 to 6 months post-operation. The clinical recovery rate was 93.8%. The SAC of C1,2 segment increased by 6.06±1.29 mm postoperatively, which showed a significant difference compared with preoperative SAC. The SAC at the latest follow-up was 15.31±0.79 mm, showing no significant difference compared with that just postoperatively. The ADI at one month post-operatively decreased by 5.75±1.53 mm, showing a significant difference compared with preoperative SAC. The ADI at the latest follow-up was 1.94±0.57 mm, showing no significant difference compared with that just postoperatively. Conclusion Preoperative Halo-traction combined with Magerl surgery in treatment of children with atlantoaxial rotatory subluxation is a safe and effective method. Key words: Atlanto-axial joint; Dislocations; Child; Internal fixators; Spinal fusion

Spinolaminar Line Test as a Screening Tool for C1 Stenosis.

Study Design Retrospective cohort. Objective To clarify the sensitivity of C3–C2 spinolaminar line test as a screening tool for the stenosis of C1 space available for the cord (SAC). Methods Spine clinic records from April 2005 to August 2011 were reviewed. The C1 SAC was measured on lateral radiographs, and the relative positions between a C1 posterior arch and the C3–C2 spinolaminar line were examined and considered “positive” when the C1 ring lay ventral to the line. Computed tomography (CT) scans and magnetic resonance imaging (MRI) were utilized to measure precise diameters of C1 and C2 SAC and to check the existence of spinal cord compression. Results Four hundred eighty-seven patients were included in this study. There were 246 men and 241 women, with an average age of 53 years (range: 18 to 86). The mean SAC at C1 on radiographs was 21.2 mm (range: 13.5 to 28.2). Twenty-one patients (4.3%) were positive for the spinolaminar line test; all of these patients had C1 SAC of 19.4 mm or less. Eight patients (1.6%) had C1 SAC smaller than C2 on CT examination; all of these patients had a positive spinolaminar test, with high sensitivity (100%) and specificity (97%). MRI analysis revealed that two of the eight patients with a smaller C1 SAC had spinal cord compression at the C1 level. Conclusion Although spinal cord compression at the level of atlas without instability is a rare condition, the spinolaminar line can be used as a screening of C1 stenosis.

Anterior arch resection combined with posterior fixation for odontoid malunion

Objective To study the clinic efficacy of anterior arch resection, atlantoaxial joint release combined with posterior fixation and fusion for odontoid malunion associated with irreducible atlantoaxial dislocation. Methods From February 2007 to February 2012,6 patients (5 males, 1 female) were diagnosed with odontoid malunion associated with irreducible atlanto-axial dislocation. The ages ranged from 36 to 57 years (average 45.5 years). There were traumatic histories and spinal injury symptoms in all patients. The preoperative Japanese Orthopaedic Association (JOA) score was 7.5±2.2 (range, 4-10), and the space available for the cord (SAC) of preoperation ranged from 5 to 11 mm (8.1±2.5 mm). All cases received anterior arch resection, atlantoaxial joint release combined with posterior fixation and fusion. They all wore cervical collar for 3 months after operation. The function of spinal cord was observed and atlanto-axial reduction and fusion was evaluated by postoperative X-ray and CT scan. Results All the patients underwent surgery successfully and their atlanto-axial reductions were complete. 6 cases were followed up for 12-20 months (average 16 months). No instrument failure or dislocation was observed during follow-up. Bone graft fusion was achieved 3 months after operation. The JOA score at the last follow-up was 10-15 (average 14.7±2.1), which showed significant difference compared with preoperative score. The average improving rate of JOA was 75.5%. The SAC at the last follow-up was 11-17mm (average 13.5±2.6 mm), which had significant difference compared with preoperative score. On the 5th day after operation, one patient experienced exudation and poor healing of posterior incision which was resolved by lateral position avoiding compression of wound. The posterior incision healed within 3 weeks. On the 3th day after operation, apathy occurred in one case and laboratory tests showed hypernatremia and hypokalemia. The consciousness of the patient recovered within 1 day after venous fluid infusion timely. Conclusion Anterior arch resection, atlantoaxial joint release combined with posterior fixation and fusion is a safe and efficient method with satisfactory short-term outcome for odontoid malunion associated with irreducible atlantoaxial dislocation. Key words: Odontoid process; Spinal fractures; Fracture healing; Atlanto-axial joint; Dislocations; Spinal cord compression

MRI morphometric characterisation of the paediatric cervical spine and spinal cord in children with MPS IVA (Morquio‐Brailsford syndrome)

Nearly all children with MPS IVA develop skeletal deformities affecting the spine. At the atlanto-axial spine, odontoid hypoplasia occurs. GAG deposition around the dens, leads to peri-odontoid infiltration. Transverse/alar ligament incompetence causes instability. Atlanto-axial instability is associated with cord compression and myelopathy, leading to major morbidity and mortality. Intervention is often required. Does the presence of widened bullet shaped vertebra in platyspondily encroach on the spinal canal and cause spinal stenosis in MPS IVA? So far, there have been no standardised morphometric measurements of the paediatric MPS IVA cervical spine to evaluate whether there is pre-existing spinal stenosis predisposing to compressive myelopathy or whether this is purely an acquired process secondary to instability and compression. This study provides the first radiological quantitative analysis of the cervical spine and spinal cord in a series of affected children. MRI morphometry indicates that the MPS IVA spine is narrower at C1–2 level giving an inverted funnel shape. There is no evidence of a reduction in the Torg ratio (canal-body ratio) in the cervical spine. The spinal canal does not exceed 11 mm at any level, significantly smaller than normal historical cohorts (14 mm). The sagittal diameter and axial surface area of both spinal canal and cord are reduced. C1–2 level cord compression was evident in the canal-cord ratio but the Torg ratio was not predictive of cord compression. In MPS IVA the reduction in the space available for the cord (SAC) is multifactorial rather than due to congenital spinal stenosis.

Atlantoaxial pedicle screw system for treatment of unstable atlantoaxial dislocation post traction

Objective To explore the technique and clinical outcome of the atlantoaxial pedicle screw system in the treatment of the unstable atlantoaxial dislocation post traction.Methods The study involved 32 patients with atlantoaxial dislocation(type T2 of TOI classification)admitted from March 2005 to September 2009.There were 17 patients with fresh odontoid fracture and two with old odontoid fracture,five with traumatic disruption of the transverse atlantal ligament and eight with congenital odontoid dysplasia.JOA scores of neurological function before operation was at a range of 5-13(average 8.38).The average of space available for the cord(SAC)was 9.15 mm.Before the atlantoaxial pedicle screw system was carried out,the skull traction was performed in all the patients preoperatively.Results A total of 128 pedicle screws were inserted safely,with mean operation time and perioperative blood loss for 1.5 hours and 300 ml,respectively.No injury to the vertebral artery or spinal cord was observed.All the patients were followed up for 12-24 months,which showed that JOA scores one year after operation was increased to 10-17(average 14.56),with the improvement rate of 71.70%,and that the SAC was average 14.86 mm.The X-ray and SCT scans verified the proper position of the screws,with no internal fixation failure or atlantoaxial redislocation.After 3-6 months,all the patients except for one patient achieved a solid bone fusion.One year after operation,the one patient with no bone graft fusion was removed of the internal fixation system and obtained satisfactory restoration of the rotational function.Conclusions Atlantoaxial pedicle screw system is an effective method for the treatment of the unstable atlantoaxial dislocation post traction,for it has the advantages of stable three-dimension fixation,direct screw placement,intraoperative reduction and high fusion rate. Key words: Atlanto-axial joint; Fracture fixation,internal; Pedical screw

Advanced imaging of the cervical spine and spinal cord in 22q11.2 deletion syndrome: Age-matched, double-cohort, controlled study

The 22q11.2 deletion syndrome is a common genetic syndrome with a wide spectrum of abnormalities. We have previously described multiple anomalies of the upper cervical spine in this disorder. The objective of this study was to use advanced imaging to further define the morphology of the cervical spine and spinal cord in the 22q11.2 deletion syndrome, with a comparison to age-matched controls. A total of 32 patients with a 22q11.2 deletion underwent advanced imaging (computed tomography/magnetic resonance imaging; CT/MRI) of the cervical spine. In 27 patients, space available for the cord (SAC); the sagittal diameter of the vertebral body, spinal canal, cerebrospinal fluid (CSF), and spinal cord; and the cross sectional area of the spinal canal, CSF, and spinal cord were measured at each cervical level and compared to 29 age-matched controls. Statistical analysis was performed and potential implications were hypothesized. In 22q11.2 patients, advanced imaging identified 40 pathologies not evident on plain radiographs with potential mechanical and/or neurological implications. These patients also had significantly smaller values (P </= 0.05) of the following parameters at one or more cervical levels, relative to age-matched controls: width of the vertebral body, spinal canal, CSF, and spinal cord; area of the spinal canal, CSF, and spinal cord. Neurologic symptoms were observed in 4/32 patients, with one patient requiring surgical intervention. Advanced imaging of the cervical spine can detect findings not evident on plain radiographs in the 22q11.2 deletion syndrome. CT and/or MRI may be indicated when there is a high index of suspicion for clinical instability or neurologic compromise in order to rule out dynamic encroachment or impending neurologic sequelae. Spinal canal and spinal cord dimensions are reduced in these patients relative to controls with currently unknown clinical significance.

2008 Young Investigator Award: The Role of Congenitally Fused Cervical Segments Upon the Space Available for the Cord and Associated Symptoms in Klippel-Feil Patients

A prospective radiographic and retrospective clinical chart review. This study evaluated the role of congenitally fused cervical segments in relation to the space available for the cord (SAC) and associated cervical spine-related symptoms (CSS) in patients with Klippel-Feil Syndrome (KFS). KFS is a developmental disorder presenting with congenital fusion of at least 2 cervical vertebrae. The effects of congenitally fused cervical segments in relation to the SAC and associated symptoms in KFS patients remain speculative and have not been thoroughly addressed in the literature. At a single institution, a prospective radiographic and clinical evaluation of 29 KFS patients was conducted. Based on plain radiographs, assessment of the SAC consisted of the posterior atlantodens interval, the midvertebral body SAC (C2-C7), and the interbody SAC (C2-C3-C7-T1). Vertebral body width (VBW) from C2 to C7 and the presence of occipitalization (O-C1) were also noted. Torg ratios were obtained at each level. Demographics, medical history, and the presence of CSS were noted based on clinical chart review. Ten males and 19 females were reviewed (mean age, 13.4 years). A significant correlation was noted between the overall VBWs to the number of fused segments, age, and skeletal maturity (P < 0.05), but not to sex-type, O-C1, and SAC levels (P > 0.05). In the presence of a fused segment, individualized SAC levels tended to have greater canal dimensions and cephalad/caudal VBWs were less. Cephalad and caudal Torg ratios in relation to a segment were greater in all fused segments, and with 4 or greater fused segments (P < 0.05). Number of levels fused, sex-type, skeletal maturity, and O-C1 were not significantly associated with the presence of symptoms (P > 0.05). Symptomatic patients had smaller VBWs than nonsymptomatic patients (P = 0.027) and an overall decrease in SAC at the interbody disc level, primarily at C6-C7 (P > 0.05). Smaller Torg ratios were noted in symptomatic patients, specifically myelopathic patients. Congenital fusion in KFS may arrest the normal vertebral development, which may affect appositional bone growth. Such effects on the VBW could potentially contribute to an increase in the SAC. Such a development may delay neurologic compromise stemming from the congenital fusion process and subsequent degenerative manifestations.

Upper Cervical Spine Instability in Pseudoachondroplasia

Pseudoachondroplasia (PSACH) is a rare autosomal dominant skeletal dysplasia associated with os odontoideum and atlantoaxial instability. This study aims to define the characteristics of upper cervical spine instability in patients with PSACH and analyze the relation between the incidence of upper cervical instability and os odontoideum. Fifteen patients (10 women and 5 men) with PSACH of Korean ethnicity with mean age of 23.7 years (range, 3-44 years) at presentation to our hospital with varied complaints, including short stature, limb deformity, neck pain, and neurological symptoms, were evaluated clinicoradiologically for upper cervical spine instability. The patients were separated into group 1 (n = 9) with os odontoideum and group 2 (n = 6) without os odontoideum. Comparisons were made using parameters such as instability index, rotational instability, atlantodens interval and space available for cord, and analysis done to correlate cervical instability with age and Japanese Orthopedic Association (JOA) score. Significant differences were found statistically when the 2 groups were compared on the basis of the space available for the cord (SAC), JOA scoring, and rotational instability. Linear relationship was found between instability and age and JOA score. Incidence of os odontoideum was 60% in our study group. Os odontoideum led to an increase in the incidence of upper cervical spine instability. Instability increased with the age. The presence of os odontoideum and atlantoaxial instability did not warrant for surgery because no signs of cervical myelopathy developed or progressed in our patients during the follow-up period, but these patients should undergo regular clinical and radiological evaluation. Level IV prognostic study.