Novel surgical classification and treatment strategy for atlantoaxial dislocations

Transoral Atlantoaxial Reduction Plate (TARP) Technique for the Treatment of Irreducible Atlantoaxial Dislocation (IAAD) Caused by Old Odontoid Fracture

STUDY DESIGN

Retrospective case series study.

OBJECTIVES

This study aimed to evaluate the clinical efficacy of TARP technique for treating IAAD caused by old odontoid fracture and assess the outcomes of patients who underwent TARP technique over 2 years of follow-up.

METHODS

Between January 2005 and September 2017, 56 patients with IAAD caused by old odontoid fractures were treated with TARP technique. Patients' clinical, radiological, and surgical data were retrospectively analyzed. Radiological parameters included the atlantodental interval (ADI) and the space available for the spinal cord (SAC) were measured. Occipitocervical pain levels and neurologic status were evaluated with Visual Analog Scale (VAS) and Japanese Orthopaedic Association (JOA) score respectively. Degree of cervical dysfunction was assessed by Neck Disability Index (NDI). Fusion status was evaluated by images during the follow-ups.

RESULTS

Surgeries for 56 cases were performed successfully with no injury to the spinal cord, nerve, or blood vessels. All patients achieved satisfactory reduction and fixation. Clinical symptomatic relief was obtained in all cases (100%). Patients were followed up for an average of 33.9 ± 9.6 months (ranged 24-60 months). Improvements in the postoperative ADI, SAC, VAS, JOA score and NDI were significant (P < .05). Besides, Bone fusion was observed in all patients. No hardware failure or re-dislocation occurred during the follow-up period.

CONCLUSIONS

TARP technique is an effective procedure for the treatment of IAAD caused by old odontoid fracture, which can achieve complete release, satisfactory decompression, reduction and fixation, and reliable bone fusion through a single transoral approach.

Tomographic Evaluation of the Upper Cervical Spine in Patients with Cleft lip and Palate and Class III Malocclusion

OBJECTIVE

To perform a morphometric analysis of the upper cervical spine (UCS) by means of cone-beam computed tomography (CBCT) for the diagnosis of malformations or craniocervical instabilities in patients with cleft lip and palate (CLP) and class III malocclusion.

MATERIALS AND METHODS

A total of 72 CBCTs from adult patients (48 male and 24 female) with Angle Class III malocclusion were divided into three groups: 1) Unilateral cleft lip and palate (UCLP) (n = 29; male = 65.5%; age = 24, 2 ± 4.2 years); 2) Bilateral cleft lip and palate (BCLP) (n = 18; male = 83.3%; age = 26.4 ± 6.0 years); 3) Control group (CON) (n = 25; male = 56.0%; age = 27.8 ± 9.3 years). The version 11.7 of the Dolphin® software (Chatsworth, California, USA) was used to evaluate the morphometric measurements and anomalies of the UCS. Data were analyzed by descriptive and inferential statistics (p ≤ 0.05).

RESULTS

For the UCLP, BCLP and CON groups, respectively, the measures were: atlantodental interval (2.1 ± 0.5; 2.1 ± 0.4; 2.0 ± 0.3 mm), basion-opisthion (35.9 ± 3.2; 36.4 ± 3.0; 34.7 ± 1.9 mm), hyoid-C3 (34.5 ± 3.7; 34.5 ± 5.2; 35.3 ± 4.5 mm), and hyoid-sella (108.1 ± 9.8; 111.3 ± 9.2; 109.7 ± 10 mm); clivus-canal angle (152.3 ± 13; 150.3 ± 10; 150.7 ± 10°) and Torg-Pavlov index (1.0 ± 0.2; 1.0 ± 0.1; 1.1 ± 0.2). Potentially unstable anomalies and malformations were more prevalent in the UCLP group (34,4%).

CONCLUSION

Subjects with UCLP presented compressive or unstable anomalies on upper cervical spine, more frequently than controls and BCLP, despite the lack of statistically significant differences among groups. Future studies could increase the safety of patients and healthcare professionals specialized in craniofacial anomalies.

Novel MRI signs of the atlantodental space in patients with atlantoaxial dislocation

OBJECTIVES

The type of atlantodental space tissue in patients with atlantoaxial dislocation (AAD) can help doctors understand the possibility of reduction before surgery. However, relevant research on this topic is lacking. In this study, we aimed to summarise the atlantodental space classification of patients with AAD using magnetic resonance imaging (MRI) and explore their clinical characteristics.

MATERIALS AND METHODS

Preoperative 3T cervical MR images of patients who underwent posterior reduction and fixation surgery for non-traumatic AAD between 1 September 2012 and 31 July 2023 were collected. Two radiologists read and recorded the MRI results based on the standard protocol. The kappa value was used to evaluate intra- and inter-observer agreements. The patient's age, sex, body mass index, clinical symptoms, Japanese Orthopaedic Association (JOA) score, and visual analogue scale information were obtained from medical records.

RESULTS

A total of 135 patients with AAD (mean age, 51.3 ± 14.0 years, 52 men) were included in the analysis. The inter-observer agreement between the two readers was 0.818 (P < 0.0001). The intra-observer consistencies were 0.882 (P < 0.0001) and 0.896 (P < 0.0001). Patients with inflexible tissue signs exhibit more irreducible in hyperextension position, and their range of motion of ADI is smaller. These patients were older and had a higher incidence of abnormal spinal cord signals and JOA scores.

CONCLUSIONS

Novel MRI signs exhibited high inter- and intra-observer consistency and were associated with patient age, abnormal spinal cord signals, reducibility, range of motion of ADI, and symptoms.

Biomechanical differences of three cephalic fixation methods for patients with basilar invagination and atlantoaxial dislocation in the setting of congenital atlas occipitalization: a finite element analysis

BACKGROUND CONTEXT

In cases of basilar invagination-atlantoaxial dislocation (BI-AAD) complicated by atlas occipitalization (AOZ), the approach to cranial end fixation has consistently sparked debate, generally falling into two categories: C1-C2 fixation and occipitocervical fixation. Several authors believe that C1-C2 fixation carries a lower risk of fixation failure than occipitocervical fixation.

PURPOSE

To study the biomechanical differences among 3 different cranial end fixation methods for BI-AAD with AOZ.

STUDY DESIGN

This was a finite element analysis.

PATIENT SAMPLE

A 35-year-old female patient diagnosed with congenital BI-AAD and AOZ.

OUTCOME MEASURES

range of motion (ROM), peak von Mise stress (PVMS), cage micro-subsidence, cage micro-slippage METHOD: Four finite element models were constructed, including unstable group (BI-AAD with AOZ), C1 lateral mass screw group, occipital plate group, occipitocervical rod group. The flexion and extension (FE), lateral bending (LB) as well as axial rotation (AR) were simulated under a torque of 1.5 Nm. Parameters include C1-C2 ROM, PVMS on screw-rod construct, cage micro-subsidence, cage micro-slippage.

RESULTS

The ROM of the C1 lateral mass screw group was smaller than that of the other fixation groups in LB and AR, but not FE. Compared with the occipitocervical rod group, the ROM in LB and AR of the occipital plate group was higher, but not in FE. The PVMS of C1 lateral mass screw group was significantly higher than that of the other groups. The ROM and PVMS of the occipitocervical rod group were in between the other 2 groups. Regarding the screws at the cranial end, the PVMS of the 4-screw occipitocervical rod group was significantly lower than that of the other groups. In general, the cage micro-motion follows the ascending order: C1 lateral mass group < occipitocervical rod group < occipital plate group.

CONCLUSION

In cases of BI-AAD with AOZ, the C1 lateral mass screw group provided the least ROM and cage micro-motion, but the screw-rod PVMS was the largest. The advantage of occipital plate fixation lies in the lowest screw-rod PVMS, but the ROM and cage micro-motion is the highest. Four-screw fixation at the cranial end of occipitocervical rod group helps to reduce the PVMS and may prevent screw failure at the cranial end.

Minimally Invasive Surgery for Posterior Atlantoaxial Lateral Mass Joint Fusion (MIS-PALF): A Muscle-Sparing Procedure for Atlantoaxial Instability or Dislocation

BACKGROUND

Conventional surgical procedures for atlantoaxial instability or dislocation (AAI/D) have been associated with a high prevalence of postoperative occipitocervical pain and dysfunction, as well as substantial perioperative blood loss. We hypothesized that minimally invasive surgery for posterior atlantoaxial lateral mass joint fusion (MIS-PALF), a procedure that can largely avoid disruption of suboccipital musculature, would be superior to the standard Goel-Harms technique in terms of postoperative pain and perioperative blood loss.

METHODS

This was a prospective cohort study of patients undergoing MIS-PALF for AAI/D at Peking University Third Hospital's Department of Orthopaedics from January 2021 to December 2021 and a historical control group of patients with the same diagnoses who were treated with the Goel-Harms technique. The duration of surgery, perioperative blood loss, postoperative length of hospital stay, postoperative body temperature, pain, supplementary use of narcotics, spinal cord function/improvement (assessed using the Japanese Orthopaedic Association [JOA] scores), reduction of AAI/D (determined based on radiographic parameters), rate of successful fusion, and complication rate were all compared between the 2 groups.

RESULTS

No significant differences were noted between the groups (43 MIS-PALF cases, 86 control cases) regarding baseline data, operative time, spinal cord function or improvement, reduction of AAI/D, rate of successful fusion, and complication rate. MIS-PALF was associated with significantly less perioperative blood loss, a shorter postoperative hospital stay (decreased by 30.8%), lower intensity and frequency of postoperative pain (decreased by 10.6% and 61.9%, respectively), less need for supplementary narcotics, and less frequent postoperative fever (decreased by 48.7%).

CONCLUSIONS

This was the first prospective cohort study of which we are aware on minimally invasive procedures for atlantoaxial fusion. Clinical efficacy (AAI/D reduction, rate of successful atlantoaxial fusion, JOA score improvement), efficiency (operative time), and safety (complications) of MIS-PALF appeared to be noninferior to those of the Goel-Harms technique. MIS-PALF was superior in terms of postoperative occipitocervical pain and length of hospital stay, both of which directly affect overall patient satisfaction and postoperative recovery of quality of life.

LEVEL OF EVIDENCE

Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence.

C2 pedicle screw insertion assisted by mobilization of the vertebral artery in cases with high-riding vertebral artery

Objective

To describe the feasibility, safety and efficacy of mobilization of the vertebral artery for C2 pedicle screws in cases with the high-riding vertebral artery (HRVA).
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Methods

During the period January 2020 to September 2022, fifteen patients underwent posterior occipitocervical fixation in our department. All patients had unilateral HRVA on at least one side that prohibited the insertion of C2 pedicle screws. There were 2 males and 13 females aged 47 ± 11.9 years (range: 17-64 years). After the correction of the vertical dislocation during the operation, the C2 pedicle screw insertion and occipitocervical fixation and fusion were performed using the vertebral artery mobilization technique. A routine three-dimensional reconstructed CT examination was executed to confirm the trajectory of C2 pedicle screws post-operation, and a CT angiography examination was performed when necessary. Neurological function was assessed using the Japanese Orthopedic Association (JOA) scale. The preoperative and postoperative JOA score and the main radiological measurements, including anterior atlantodental interval (ADI), the distance of odontoid tip above Chamberlain line, and clivus-canal angle (CCA), were collected and compared by paired t-test.

Results

All 15 patients had atlas assimilation, among which 12 patients had C2-C3 fusion (Klippel-Feil syndrome). Mobilization of the HRVA was successfully completed, and C2 pedicle screws were then fulfilled after the vertebral artery was protected. There was no injury to the vertebral artery during the operation. Meanwhile, no severe surgical complications such as cerebral infarction or aggravated neurological dysfunction occurred during the perioperative period. Satisfactory C2 pedicle screw placement and reduction were reached in all 15 patients. All the patients achieved bone fusion 6 months after surgery. No looseness and shift of internal fixation or reduction loss was observed during the follow-up period. Compared to the preoperative, the postoperative JOA score and the main radiological measurements were remarkably improved and statistically significant.

Conclusions

C2 pedicle screw insertion assisted by mobilization of the vertebral artery is safe and considerably effective, providing a choice for internal fixation in cases with high-riding vertebral arteries.

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

Background

The 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 methods

We 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.

Results

No 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.

Conclusion

Patient 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.

A Method to Evaluate the Reduction Difficulty of Atlantoaxial Dislocation Based on Computed Tomography Quantitative Analysis

BACKGROUND

To evaluate the difficulty of reduction of congenital atlantoaxial dislocation with or without os odontoideum or basilar invagination based on computed tomography (CT) quantitative analysis.

METHODS

From March 2018 to December 2022, the CT features of 108 patients with atlantoaxial dislocation with or without os odontoideum or basilar invagination were analyzed. Quantitative scores were defined according to imaging features, including sloping of the lateral mass; osteophyte between the lateral mass joint; ball-and-socket deformity of the lateral mass joint; vertical interlocking of the lateral mass joint; callus between the lateral mass joint; and atlanto-odontoid joint hyperplasia, blocking, or fusion. Grades were calculated according to the sum of points of the atlanto-odontoid joint and lateral mass joints, as follows: I, 0-1 points; Ⅱ, 2-3 points; Ⅲ, 4-6 points; IV, 7-10 points. After 1 week of bidirectional cervical traction, CT scans were performed, and atlantodens interval and vertical distance from dens to Chamberlain line were measured. The vertical reduction rate, horizontal reduction rate, and overall reduction rate of atlantoaxial dislocation were calculated.

RESULTS

The vertical distance from dens to Chamberlain line values after traction were significantly reduced compared with before traction, including grades I, II, III, and IV. The overall reduction rates were 85.1% ± 11.8%, 65.8% ± 8.3%, 45.0% ± 8.5%, and 38.4% ± 13.0% respectively, after 1 week of bidirectional cervical traction.

CONCLUSIONS

The CT quantitative score system is an effective noninvasive evaluation to judge the reduction difficulty of atlantoaxial dislocation with or without os odontoideum or basilar invagination.

Evaluation of the Anatomical Reference Point in Posterior Minimally Invasive Atlantoaxial Spine Surgery: A Cadaveric Anatomical Study

OBJECTIVE

Minimally invasive atlantoaxial surgery offers the benefits of reduced trauma and quicker recovery. Previous studies have focused on feasibility and technical aspects, but the lack of comprehensive safety information has limited its availability and widespread use. This study proposes to define the feasibility and range of surgical safety using the intersection of the greater occipital nerve and the inferior border of the inferior cephalic oblique as a reference point.

METHODS

Dissection was performed on 10 fresh cadavers to define the anatomical reference point as the intersection of the greater occipital nerve and the inferior border of the inferior cephalic oblique muscle. The study aimed to analyze the safety range of minimally invasive atlantoaxial fusion surgery by measuring the distance between the anatomical reference point and the transverse foramen of the axis, the distance between the anatomical reference point and the superior border of the posterior arch of the atlas, and the distance between the anatomical reference point and the spinal canal. Measurements were compared using Student's t test.

RESULTS

The point where the occipital greater nerve intersects with the inferior border of the inferior cephalic oblique muscle was defined as the anatomical marker for minimally invasive posterior atlantoaxial surgery. The distance between this anatomical marker and the transverse foramen of the axis was measured to be 9.32 ± 2.04 mm. Additionally, the distance to the superior border of the posterior arch of the atlas was found to be 21.29 ± 1.93 mm, and the distance to the spinal canal was measured to be 11.53 ± 2.18 mm. These measurement results can aid surgeons in protecting the vertebral artery and dura mater during minimally invasive posterior atlantoaxial surgery.

CONCLUSIONS

The intersection of the greater occipital nerve with the inferior border of the inferior cephalic oblique muscle is a safe and reliable anatomical landmark in minimally invasive posterior atlantoaxial surgery.

Release, reduction, and fixation of one-stage posterior approach for basilar invagination with irreducible atlantoaxial dislocation

PURPOSE

We evaluate the efficacy, safety and indications of single stage posterior release, reduction, and fixation of basilar invagination (BI) with irreducible atlantoaxial dislocation (IAAD).

MATERIALS AND METHODS

Seventeen patients with BI and IAAD consecutively underwent one-stage release, reduction, and fixation by a posterior approach from July 2000 to June 2015 were followed up for at least 12 months. There were 8 males. Mean age was 56 35.2 ± 13.8 years (range 12-56). The clinical symptoms and signs of the patients were recorded. Pre- and postoperative imaging examinations were performed. Neurological function was assessed using the Japanese Orthopedic Association (JOA) and Ranawat scores.

RESULTS

Average follow-up time was 47.4 months (12-97 months). The JOA score increased from preoperative 4-10 (8.06 ± 2.52) to postoperative 13-16 (15.20 ± 0.62). The preoperative Chamberlain line, McRae line, Wackenheim line, atlantodens interval, and cervico medullary angle were 12.52 ± 5.17 mm, 6.59 ± 3.04 mm, 6.96 ± 4.32 mm, 9.88 ± 1.93 mm, and 115.35 ± 12.40°, respectively. The postoperative values were 2.0 ± 3.67 mm, -3.06 ± 1.85 mm, -1.76 ± 2.88 mm, 1.17 ± 1.18 mm, and 136.76 ± 11.44°, respectively.

CONCLUSION

One-stage release, reduction, and fixation for patients with BI and IAAD through a posterior approach is safe and efficient.

Preoperative radiological indicators for prediction of difficult laryngoscopy in patients with atlantoaxial dislocation

Background

Difficult airway remains a great challenge in patients with atlantoaxial dislocation (AAD). Preoperative evaluation and reliable prediction are required to facilitate the airway management. We aimed to screen out reliable radiological indicators for prediction of difficult laryngoscopy in patients with AAD.

Methods

A retrospective nested case-control study within a single center longitudinal AAD cohort was conducted to investigate the radiological indicators. All the patients with difficult laryngoscopy from 2010 to 2021 were enrolled as the difficult laryngoscopy group. Others in the cohort without difficult laryngoscopy were randomly selected as the non-difficult laryngoscopy group by individually matching with the same gender, same surgery year, and similar age (±5 years) at a ratio of 6:1. Radiological data on preoperative lateral X-ray images between the two groups were compared. Bivariate logistic regression model was applied to screen out the independent predictive indicators and calculate the odds ratios of indicators associated with difficult laryngoscopy. Receiver operating characteristic curve and area under the curve (AUC) were used to describe the discrimination ability of indicators.

Results

A total of 154 patients were finally analyzed in this study. Twenty-two patients with difficult laryngoscopy and matched with 132 controls. Four radiological parameters showed significant difference between the two groups. Among which, ΔC1C2D (the difference of the distance between atlas and axis in the neutral and extension position), owned the largest AUC.

Conclusions

ΔC1C2D could be a valuable radiologic predictor for difficult laryngoscopy in patients with AAD.

Traumatic posterior dislocation of atlanto-axial joint with anterior arch fracture in the patient of atlanto-occipital assimilation: A case report

INTRODUCTION AND IMPORTANCE

Traumatic atlanto-axial dislocation (AAD) is relatively uncommon and can pose life-threatening risks. In this case, we describe a patient with a combination of AAD, an anterior arch fracture of the atlas, and a rare congenital anomaly known as atlanto-occipital assimilation (AOA).

CASE PRESENTATION

A 70-year-old man presented with posterior neck pain and right-sided torticollis following an accident that collision with a car while riding an electric scooter. Radiographic findings confirmed posterior AAD with anterior arch fracture of C1 in the inherent setting of AOA. The patient showed no neurologic deficit, so a closed reduction technique using Gardner-Wells tongs was attempted in an awakened state, and successful reduction could achieve without a neurologic deficit. After about three months of rigid brace application, head and neck motion was allowed, and no recurrence of dislocation or cervical pain occurred during the follow-up period of about one year.

CLINICAL DISCUSSION

Because the posterior AAD is usually accompanied by anterior arch fracture of atlas, the transverse atlantal ligament remained intact. So nonoperative management after manual reduction was possible. The presence of a C1 anterior arch fracture observed in our case can be regarded as an indicator predicting the success of closed reduction of AAD.

CONCLUSION

Our case highlighted the successful nonoperative management of traumatic posterior AAD with an accompanying anterior arch fracture of the atlas in a peculiar inherent combination of AOA through the closed reduction technique and rigid cervical brace application.

Functional and radiological outcomes following craniovertebral junction surgery

Background

Craniovertebral junction (CVJ) pathologies include atlantoaxial instability/deformities resulting in myelopathy, respiratory failure, and even death. Here, we describe the indications, preoperative planning, and intra-operative/postoperative complications following surgical management of CVJ anomalies.

Methods

A prospective analysis of 34 patients with CVJ pathology was evaluated between 2015 and 2022. Their various etiologies included atlantoaxial instability, trauma, tuberculosis, Down's syndrome, Morquio syndrome, os odontoideum, and atlantoaxial abnormalities. Clinical outcomes were assessed using the American spinal injury association (ASIA) impairment scale score and Benzel's modified Japanese Orthopedic Association (mJOA) score. Surgical assessments included length of hospital stay, operative time, blood loss, and intraoperative postoperative complications. Radiological parameters included fusion (i.e., implant loosening/implant failure), preoperative/ postoperative atlanto-dens interval (ADI), clivus canal angle (CCA), and space available for cord (SAC).

Results

Five patients were managed conservatively, while 29 patients had surgery. Operations included occipitocervical fusion (14 patients), C1-2 fusion (10 patients), C1-2 transarticular screw fixation (four patients), and one patient underwent anterior corpectomy decompression/fusion. Seven patients had vertebral artery anomalies, and 13 patients had atlantoaxial abnormalities. At the final follow-up, atlantoaxial instability (i.e., mean preoperative ADI of 6.6 ± 2.3 mm) was restored to 4.2 ± 0.6 mm, significant cord compression (i.e., with mean SAC of 8.3 ± 2.9 mm) was relieved to 17.2 ± 1.6 mm, and the mean preoperative CCA (i.e., 130.2 ± 15.3) was improved to 143.3 ± 8.3°. There was also a statistically significant improvement in the ASIA scale and mJOA score.

Conclusion

Surgical management of CVJ abnormalities requires expertise and meticulous planning to avoid devastating complications such as wound dehiscence and catastrophic vertebral artery injury.

STRANGULATION-INDUCED ATLANTOAXIAL ROTATORY SUBLUXATION TREATED WITH CLOSED REDUCTION

BACKGROUND

Cervical subluxation is a broad class of injuries in which there are degrees of misalignment of vertebral bodies in relationship to adjacent vertebra. Atlantoaxial rotatory subluxation (AARS) is a subtype of cervical subluxation resulting from exaggerated rotation of the C1-C2 complex. Inflammatory, infectious, post-surgical, and traumatic etiologies are recognized and well-described. AARS is predominantly seen in children and occurs rarely in adults.

CASE REPORT

We submit the case of an otherwise healthy adult male patient presenting to the emergency department with strangulation-induced C1-C2 subluxation with a rotational component that was treated at the bedside by neurosurgery with closed reduction. Why Should an Emergency Physician Be Aware of This? Clinicians must consider a broad range of serious pathologies in a patient presenting with torticollis, especially in the setting of strangulation. Although extremely rare in adults, AARS must be considered in the differential diagnosis, as early identification increases the likelihood of successful nonoperative treatment.

Overstrain on the longitudinal band of the cruciform ligament during flexion in the setting of sandwich deformity at the craniovertebral junction: a finite element analysis

BACKGROUND CONTEXT

In the setting of "sandwich deformity" (concomitant C1 occipitalization and C2-3 nonsegmentation), the C1-2 joint becomes the only mobile joint in the craniovertebral junction. Atlantoaxial dislocation develops earlier with severer symptoms in sandwich deformity, which has been hypothesized to be due to the repetitive excessive tension in the ligaments between C1 and C2.

PURPOSE

To elucidate whether and how the major ligaments of the C1-2 joint are affected in sandwich deformity, and to find out the ligament most responsible for the earlier development and severer symptoms of atlantoaxial dislocation in sandwich deformity.

STUDY DESIGN

A finite element (FE) analysis study.

METHODS

A three-dimensional FE model from occiput to C5 was established using anatomical data from a thin-slice CT scan of a healthy volunteer. Sandwich deformity was simulated by eliminating any C0-1 and C2-3 segmental motion respectively. Flexion torque was applied, and the range of motion of each segment and the tension sustained by the major ligaments of C1-2 (including the transverse and longitudinal bands of the cruciform ligament, the alar ligaments, and the apical ligament) were analyzed.

RESULTS

Tension sustained by the longitudinal band of the cruciform ligament and the apical ligament during flexion is significantly larger in the FE model of sandwich deformity. In contrast, tension in the other ligaments is not significantly changed in the sandwich deformity model compared with the normal model.

CONCLUSIONS

Considering the importance of the longitudinal band of the cruciform ligament to the stability of the C1-2 joint, our findings implicate that the early onset, severe dislocation, and unique clinical manifestations of atlantoaxial dislocation in patients with sandwich deformity are mainly due to the enlarged force loaded on the longitudinal band of the cruciform ligament.

CLINICAL SIGNIFICANCE

The enlarged force loaded on the longitudinal band of the cruciform ligament can add to its laxity and thus reducing its ability to restrict the cranial migration of the odontoid process. This is in accordance with our clinical experience that dislocation of the atlantoaxial joint in patients with sandwich deformity is mainly craniocaudal, which means severer cranial neuropathy, Chiari deformity, and syringomyelia, and more difficult surgical treatment.

Traumatic Posterior Atlantoaxial Dislocation With an Associated Fracture: A Systematic Review

STUDY DESIGN

Systematic review.

OBJECTIVE

To investigate the clinical presentation, mechanism of injury, patients' characteristics, diagnosis, treatment, and prognosis of traumatic posterior atlantoaxial dislocation with fracture (TPAD).

BACKGROUND

TPAD is an extremely rare entity, with a limited number of cases reported in the literature. Although rare, a thorough understanding of the pathogenesis and management of such cases is required due to the high risk of spinal cord compression and the severity of neurological deficits. We conducted a systematic review of all cases of TPAD with fractures reported in the literature.

METHODS

This systematic review was conducted following the Preferred Reporting Items for Systematic reviews and Meta-analysis guidelines. Relevant literature was retrieved from the Pubmed database. All published English-written studies involving human subjects with relevant data regarding TPAD were included.

RESULTS

Two case series and 20 case reports published between 1924 and 2021 describing 28 patients with TPAD were included. The median age at presentation was 51.5 years, with male predominance (83%). The most common fracture pattern was Anderson and D'alonzo type II odontoid fracture (78%). Neurological exam at presentation was intact in 52% of patients. The primary diagnostic imaging was computed tomography employed in 96% of cases. The management consisted of 2 stages protocol, initially, a temporary axial traction was employed (54%), and later definitive surgical treatment was employed (93%). The posterior surgical approach was favored in 82% of cases.

CONCLUSION

TPAD with fracture occurred in the majority of cases with Anderson and D'alonzo type II odontoid fracture, predominantly in males. Diagnosis is usually established based on computed tomography imaging; further imaging may not be indicated as it does not seem to alternate the patient's management course. Surgical intervention was employed in almost all cases, with favored results through posterior C1-C2 fusion.

LEVEL OF EVIDENCE

Level-IV.

Traumatic C2-C3 subluxation with atlanto-axial dislocation managed by posterior approach - A rare case report

INTRODUCTION AND IMPORTANCE

Traumatic subluxation of C2-C3 with Atlanto-Axial dislocation is very rare and uncommon condition. Only a very few case reported. What constitutes appropriate management in cases of traumatic C2-C3 subluxation with Atlato-axial dislocation is still controversial due to the infrequency of this injury. We managed a patient who had traumatic C2-C3 subluxation with Atlanto-axial dislocation following a history of trauma through posterior approach successfully.

CASE DESCRIPTION

A 45-year male day laborer presented with neck pain with progressive neurological deficit after two episodes of fall with heavy object within 1 year. Imaging revealed complete dislocation of C2 over C3 with Atlanto-Axial Dislocation. The patient was approached for posterior fixation with attempt to reduction per-operatively with skeletal traction and C1, C2, C3 joint distraction. After distraction of the joint, we achieved to do reduction of the C2-C3 and Atlanto-Axial joint. We did C1 lateral mass, C2 pedical and C3, C4 lateral mass screw and put a spacer in between C1-C2 facet joint. The patient was improved immediately after the operation. One year follow up shows, he was completely well. One year follow up shows in radiography proper alignment with fusion between C1, C2 and C3.

CLINICAL DISCUSSION

Traumatic subluxation of the C2 vertebra is due to fractures of the lamina, articular facets, pedicles, or pars interarticularis and was first described by Bouvier in1843. To the best of our knowledge there has been 3/4 cases reported till now with traumatic C2-C3 subluxation with AAD. In three similar cases before ours, one was reported to be reduced after 3 weeks of bidirectional cervical traction and another two cases were managed by open reduction and stabilization. We managed this rare case surgically successfully through posterior approach with good outcome.

CONCLUSION

Our management through posterior approach between C1 to C4 shows very good outcome with proper fusion. But it needs proper understanding the anatomy and mechanism of reduction by careful reading the image. Its needs more case description and management to establish a standard treatment for this type of disease.

Posterior pedicle screw fixation combined with local steroid injections for treating axial eosinophilic granulomas and atlantoaxial dislocation: A case report

BACKGROUND

Eosinophilic granuloma (EG) is a proliferative condition that affects the cells of bone tissue. There are no specific clinical signs or imaging manifestations in the early stages of the disease, making it simple to overlook and misdiagnose. Because of the disease's rarity, there is presently no standardized treatment principle. There are few accounts of such occurrences affecting the axis among children. We discovered a case of a child whose EG resulted in atlantoaxial joint dislocation and destruction of the axial bone.

CASE SUMMARY

After having pharyngeal discomfort for more than six months without a clear explanation, a 6-year-old boy was brought to our hospital. Following a careful evaluation, the pathology indicated a strong likelihood of an axial EG. Ultimately, we decided to treat the boy with posterior pedicle screw fixation and local steroid injections.

CONCLUSION

EGs of the upper cervical spine are quite uncommon in children, and they are exceedingly easy to overlook or misdiagnose. Posterior pedicle screw fixation and local steroid injections are effective treatments for patients with axial EGs affecting the atlantoaxial junction.

Prevalence and radiographic features of atlantoaxial dislocation in adult patients with Kashin-Beck disease

PURPOSE

Kashin-Beck disease (KBD) is an endemic osteoarthropathy affecting the epiphyseal growth plate of multiple joints in young and adolescent patients. Previous studies have focused on the visible deformed extremities instead of the spinal radiological features, especially the atlantoaxial joint. The aim of this study was to determine the prevalence and radiographic features of atlantoaxial dislocation (AAD) in adult patients with KBD.

METHODS

This study was conducted on KBD patients in three typical endemic counties between October 2017 and November 2019. The patients were evaluated by collecting basic information, clinical signs and symptoms. They underwent dynamic cervical radiography, by which AAD was diagnosed. For those patients with confirmed or suspected AAD, computed tomography (CT) imaging was performed to observe the odontoid morphology and degenerative changes in the lateral atlantoaxial joints. Radiographic evaluations were reviewed to determine the prevalence and features of AAD.

RESULTS

A total of 39 (14.6%) of 267 KBD patients were diagnosed with AAD. Compared with the non-AAD patients, the detection rate of AAD was associated with a longer disease duration and stage and was not associated with age, sex or BMI. Thirty-two patients had symptoms at the neck or neurological manifestations, while seven had no symptoms. There were three types of morphologies of the odontoid process in AAD patients: separating in 19 cases, hypoplastic in 15 cases and intact in five cases. Anterior dislocation was noted in 29 cases, and posterior dislocation was noted in ten cases. Thirty-four cases were reducible, and five were irreducible. The lateral atlantoaxial joints had different severities of degenerative changes in 17 cases.

CONCLUSIONS

This study revealed that the prevalence of AAD was 14.6% in adult KBD patients. The radiographic features of AAD include manifestations of odontoid dysplasia and chronic degenerative changes in atlantoaxial joints. KBD patients with severe stages and longer disease duration were more vulnerable to the occurrence of AAD. We postulate that this atlantoaxial anomaly might originate from chondronecrosis of the epiphyseal growth plate of the odontoid process in young and adolescent individuals. This study may provide a clinical reference to help clinicians screen, prevent and treat AAD in adult patients with KBD.

Clinical and Surgical Characteristics of Patients with Atlantoaxial Dislocation in the Setting of "Sandwich Fusion": A Case-Control Study

BACKGROUND

Patients with "sandwich" fusion (concomitant C1 occipitalization and C2-C3 nonsegmentation), a subtype of Klippel-Feil syndrome, are at particular risk for developing atlantoaxial dislocation (AAD). However, the clinical and surgical characteristics of AAD in patients with sandwich fusion have not been clearly defined.

METHODS

A retrospective case-control study with a large sample size and a minimum 2-year follow-up was performed. From 2000 to 2018, 253 patients with sandwich AAD underwent a surgical procedure; these patients constituted the case group, and a matching number of patients with non-sandwich AAD were randomly selected to form the control group. Clinical data from electronic medical records and various imaging studies were analyzed and compared. The Japanese Orthopaedic Association (JOA) scale was used to evaluate neurological function.

RESULTS

Patients with sandwich AAD, compared with patients with non-sandwich AAD, had symptom onset at a younger age (34.8 compared with 42.8 years; p < 0.001) and had a higher likelihood for myelopathy (87.4% compared with 74.7%; p < 0.001). Patients with sandwich AAD had a higher incidence of lower cranial nerve palsy (7.9% compared with 0.0%; p < 0.001), a lower preoperative JOA score (13.4 compared with 14.2; p < 0.001), and higher incidences of accompanying Type-I Chiari malformation (20.9% compared with 1.2%; p < 0.001) and syringomyelia (21.3% compared with 1.6%; p < 0.001). Finally, patients with sandwich AAD had higher likelihoods of undergoing transoral release (28.5% compared with 5.1%; p < 0.001) and use of salvage fixation techniques (34.4% compared with 6.3%; p < 0.001), and had lower postoperative results for the JOA score (14.9 compared with 15.9; p < 0.001) and improvement rate (43.8% compared with 58.2%; p < 0.001).

CONCLUSIONS

Patients with sandwich AAD demonstrated distinct clinical manifestations. Versatility involving the use of various internal fixation techniques and transoral release procedures was frequently required in the surgical management of these patients, and meticulous and personalized preoperative planning would be of paramount importance.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Analysis of surgical strategies and efficacy in the treatment of Os odontoideum with atlantoaxial dislocation

BACKGROUND

There are many classification systems for atlantoaxial dislocation (AAD). Among these systems, the definitions of irreducible AAD remain vague, and its treatments are not unified.

OBJECTIVE

To explore the surgical strategies and efficacy for the treatment of os odontoideum (OO) with AAD.

METHODS

The clinical data of 56 OO patients with AAD who underwent surgery from January 2017 to June 2021 were retrospectively analyzed. AAD was classified into four types, Type I and type II were treated with posterior fixation and fusion. Type III received posterior fixation and fusion after irreducible dislocations were converted to reducible dislocations by translateral mass release or transoral release. Type IV required transoral release for conversion into reducible dislocations before posterior fixation and fusion. The operation time, blood loss, and complications were recorded. The preoperative and postoperative neurological function changes were assessed using the Japanese Orthopedic Association (JOA) score. Postoperative fusion status was assessed by X-ray.

RESULTS

There were 40 cases of type I-II, 14 cases of type III, and two cases of type IV AAD. The operation times of single posterior fixation and fusion, combined translateral mass release and combined transoral release were 130.52 ± 37.12 min, 151.11 ± 16.91 min and 188.57 ± 44.13 min, the blood loss were 162.63 ± 58.27 mL, 235.56 ± 59.94 mL, 414.29 ± 33.91 mL, respectively. One patient with type III died, one with type III underwent revision surgery due to infection, and three patients with type I had further neurological deterioration after operation. fifty-five patients were followed up for 12-24 months. The follow-up results showed that enough decompression was achieved and that fixation and fusion were effective. The JOA score increased from 9.58 ± 1.84 points preoperative to 13.09 ± 2.68 points at 3 months after operation, 14.07 ± 2.83 points at 6 months and 14.25 ± 2.34 at 12 months after operation, all significant differences compared with preoperative results (P < 0.05).

CONCLUSION

OO patients with irreducible AAD can be treated by translateral mass release or transoral release combined with posterior fixation and fusion, while some of those with bony fusion can be treated by transoral release combined with posterior fixation and fusion.

Treatment of irreducible atlantoaxial dislocation by bony deformity osteotomy, remodeling, releasing, and plate fixating through transoral approach

OBJECTIVE

Investigate a novel method for treating irreducible atlantoaxial dislocation (IAAD) or with basilar invagination (BI) by bony deformity osteotomy, remodeling, releasing, and plate fixating through transoral approach.

METHOD

From March 2015 to December 2019, 213 consecutive patients diagnosed as IAAD/BI were treated with transoral bony deformity remodeling and releasing combined with plate fixation. The main clinical symptoms include neck pain, headache, numbness of the limbs, weakness, unstable walking, inflexible hand-held objects, and sphincter dysfunction. The bony factors that impact reduction were divided into as follows: type A1 (sloping of upper facet joint in C2), type A2 (osteophyte in lateral mass joints between C1 and C2), type A3 (ball-and-socket deformity of lateral mass joint), type A4 (vertical interlocking between lateral mass joints of C1-C2), type A5 (regional bone fusion in lateral mass joints), type B1 (bony factor hindering reduction between the atlas-dens gap), type B2 (uncinate odontoid deformity), and type B3 (hypertrophic odontoid deformity). All of them were treated with bony deformity osteotomy, remodeling, and releasing techs.

RESULT

The operation time was 144 [Formula: see text] 25 min with blood loss of 102 [Formula: see text] 35 ml. The average pre-operative ADI improved from 7.5 [Formula: see text] 3.2 mm pre-surgery to 2.5 [Formula: see text] 1.5 mm post-surgery (p < 0.05). The average VDI improved from 12.3 [Formula: see text] 4.8 mm pre-surgery to 3.3 [Formula: see text] 2.1 mm post-surgery (p < 0.05). The average pre-operative CMA improved from 115 [Formula: see text] 25° pre-surgery to 158 [Formula: see text] 21° post-surgery (p < 0.05); the pre-operative CAA changed from 101 [Formula: see text] 28° pre-surgery to 141 [Formula: see text] 10° post-surgery. After the operation, the clinic symptoms improved, and the JOA score improved from 9.3 [Formula: see text] 2.8 pre-operatively to 13.8 [Formula: see text] 2.5 in the sixth months of follow-up.

CONCLUSION

In addition to soft tissue factors, bony obstruction was another important factor impeding atlantoaxial reduction. Transoral bony deformity osteotomy, remodeling, releasing combined with plate fixating was effective in treating IAAD/BI with bony obstruction factors.

Traumatic lateral atlantoaxial dislocation combined with a type II odontoid fracture in a patient with ankylosing spondylitis: A case report

RATIONALE

Traumatic lateral atlantoaxial dislocation (AAD) combined with an odontoid fracture is extremely rare. The standards applicable to management of the traumatic lateral AAD are still in flux due to the infrequency of this injury.

PATIENT CONCERNS

We present a unique case of traumatic lateral AAD combined with a type II odontoid fracture in a patient with ankylosing spondylitis (AS).

DIAGNOSIS

Spinal computed tomography showed ankylosis of the entire spine from the sacroiliac joint to the cervical spine. On the cervical X-ray the head was rotated to the right with anterior subluxation of the C1 and odontoid tip relative to C2. The coronal computed tomography (CT) scan also revealed left lateral dislocation of C1 on C2 with a horizontal translation of the odontoid tip. On the axial and sagittal CT scan, the left C1 lateral mass was displaced anteriorly and locked by C2 body.

INTERVENTIONS

We performed occipito-cervical fusion (OCF) after successful manual reduction under general anesthesia.

OUTCOMES

The patient's recovery from surgery was uneventful and without complication. At the 3 year follow-up the patient was asymptomatic and reportedly satisfied with the surgery.

LESSONS

Traumatic AAD with an odontoid fracture is an exceedingly uncommon cervical spine injury. A lateral subluxation with a type II odontoid fracture in a patient with AS is rarer still, so much so that this type of subluxation was not classifiable using any of the previously developed classification systems. In this patient with AS, posterior OCF with internal fixation was necessary to avoid hardware failure, particularly in light of the intensive stress caused by AS.

Posterior two-step distraction and reduction for basilar invagination with atlantoaxial dislocation: a novel technique for precise control of reduction degree without traction

PURPOSE

The pathological changes of basilar invagination (BI) and atlantoaxial dislocation (AAD) include vertical and horizontal dislocations. Current surgical techniques have difficulty in accurately controlling the degree of reduction in these two directions and often require preoperative traction, which increases patients' pain, hospital stay, and medical cost. This study aimed to introduce a novel technique for accurately reducing horizontal and vertical dislocation without preoperative traction and report the radiological and clinical outcomes.

METHODS

From 2010 to 2020, patients with BI and AAD underwent posterior two-step distraction and reduction (TSDR) and occipitocervical fixation. Radiological examination was used to evaluate the reduction degree (RD) and compression. Japanese Orthopedic Association (JOA) score was used to evaluate clinical outcome.

RESULTS

A total of 55 patients with BI and AAD underwent TSDR and occipitocervical fusion. The clinical symptoms of 98.2% of them improved. JOA score increased significantly after the operation. Appropriate (50% ≤ RD < 80%) or satisfactory (RD ≥ 80%) horizontal reduction was achieved in 92.7% of patients, and 90.9% obtained appropriate or satisfactory vertical reduction. Thirty-one patients did not undergo preoperative skull traction. There was no significant difference in radiological outcomes or JOA scores between the traction and non-traction groups. However, the length of hospital stay in the traction group was longer than that in the non-traction group.

CONCLUSION

TSDR enables horizontal and vertical reduction. It is a safe, simple, and effective technique for patients with BI and AAD. Despite the absence of preoperative skull traction, the degree of reduction and clinical outcomes were satisfactory.

Anterior Transarticular Crossing Screw Placement for Atlantoaxial Instability in Children: Computed Tomography-Based Study

OBJECTIVE

The feasibility of anterior transarticular crossing screw (ATCS) fixation for atlantoaxial instability was confirmed in adults. However, atlantoaxial instability is more common in children. Therefore this study was aimed to ascertain the pediatric morphometric characteristics of ATCS in C1-2.

METHODS

Morphometric analysis was conducted on computed tomography scan in 87 pediatric patients who were divided into groups based on ages (1-6 years, 7-10 years, and 11-16 years). Measurements were taken in sagittal and axial planes of computed tomography imaging to determine the range of screw lateral angles, incline angles, and screw lengths.

RESULTS

The overall screw lengths were relatively longer in males than females. For those aged 1-6 years, the screw lengths were 25.5-32.8 mm in males and 24.2-31.3 mm in females, respectively. The screw lengths showed no difference in the 7- to 10-year group between sexes, while the incline angle was larger in females than males. And the screw lengths were 33.5-43.2 mm in males and 31.2-40.4 mm in females in the 11- to 16-year group. The screw lengths were increased with age, yet the lateral angles were decreased. We also found that the epiphyseal closure of odontoid reached 93.6% when the age was older than 7 years old. Therefore ATCS was recommended for children older than 7 years.

CONCLUSIONS

The overall screw lengths and lateral angles of ATCS were larger in male children than those in females, but the incline angles were larger in females. ATCS is feasible in children, particularly those aged 7 years or older.

Subaxial lordosis loss and influence factors after posterior atlantoaxial fusion

Summary of background data

Cervical sagittal balance is an important evaluation index of cervical physiological function and surgical efficacy. Subaxial kyphosis after atlantoaxial fusion is negatively associated with worse clinical outcomes and higher incidence of lower cervical disk degeneration.

Objectives

This study aimed to confirm the factors that influence subaxial lordosis loss after posterior atlantoaxial fusion.

Methods

We performed a retrospective review of all patients following posterior C1–C2 fusion for atlantoaxial dislocation between January 2015 and December 2017. All charts, records, and imaging studies were reviewed for each case, and preoperative, immediate postoperative, and final follow-up plain films were evaluated. Comparing final follow-up and preoperative C2–C7 angle, patients were divided into two groups for further comparison: subaxial lordosis loss group and subaxial lordosis increase group.

Results

A total of 18 patients were included in the review, with an average radiographic follow-up of 8.4 ± 3.7 months (range 6–17 months). Subaxial lordosis loss was observed in 5 cases (27.8%) at the final follow-up, whereas 13 cases had an increase in subaxial lordosis. The cervical sagittal parameters of preoperative and final follow-up between two groups were compared, the preoperative C2–C7 angle of the subaxial lordosis loss group was bigger than the subaxial lordosis increase group (27.6° ± 10.5° vs 10.5° ± 10.5°, P < 0.05), but there was no statistical difference in other parameters. Univariate chi-square analysis showed that reduction in subaxial lordosis after posterior atlantoaxial fusion was associated with preoperative C2–C7 angle ≥ 20° (χ² = 4.923, P = 0.026). However, Logistic regression analysis showed that the preoperative C2–C7 angle ≥ 20° was not an independent risk factor (OR = 0.147, P = 0.225).

Conclusion

Our study demonstrates that subaxial lordosis loss may occur after posterior atlantoaxial fusion, and preoperative C2–C7 angle ≥ 20° was a risk factor of postoperative loss of subaxial lordosis.

Atlantoaxial Dislocation with Bony Fusion of C1/2 Facet Joints Treated with Posterior Joint Release, Distraction and Reduction

Introduction

Atlantoaxial dislocation (AAD) is a complicated and challenging deformity with severe morbidities. Irreducible AAD with C1/2 bony fusion requires anterior (transoral or transnasal) odontoidectomy to decompress spinal cord or medulla, which is highly demanding technique that is risky for comorbidities. Here, we report our application of modified Goel's technique to reduce AAD with bony fusion through single-stage posterior approach surgery.

Technical Note

Our technique that can reduce AAD with bony fusion through single-stage posterior approach surgery is reported. Joint release, distraction, cage implantation, and atlantoaxial or occipitocervical fixation can successfully manage AAD with C1/2 bony fusion. Key points for the technique include pinpointing original joint space, thorough release of bony fusion, stepwise distraction, and cage implantation with autograft.

Conclusions

Joint release, distraction, cage implantation, and atlantoaxial or occipitocervical fixation can successfully manage bony irreducible AAD. This technique provided an option for bony fused AAD and improved safety and efficacy of its management.

Three-dimensional reduction method with a modified C2 isthmus screw in irreducible atlantoaxial dislocation: a technical note

BACKGROUND

Three-dimensional reduction plays a vital role in surgical reduction of irreversible atlantoaxial dislocation (IAAD). However, the most commonly used combination of C1 pedicle screw (PS) or lateral mass screw (LMS) and C2 PS or isthmus screw often fails to achieve satisfactory reduction at one time. The difficulty is usually caused by short anteroposterior and vertical distance between heads of C1 and C2 screws, which lack enough space for reduction operation. The objective of this study is to describe a three-dimensional reduction method with a modified C2 isthmus screw and to illustrate its advantage and effectiveness for IAAD.

METHODS

Twelve patients with IAAD underwent reduction and fixation with modified C2 isthmus screw combined with C1 PS or LMS, fusion with autologous bone graft. The insertion point was lateral to the intersection of caudal edge of C2 lamina and lateral mass, with a trajectory towards C2 isthmus, via lateral mass. The three-dimensional reduction was achieved through pulling and distracting. Radiographic evaluation included anteroposterior and direct distance between different insertion points, the occipitoaxial angle (O-C2A), clivus-canal angle (CCA) and cervicomedullary angle (CMA). Clinical outcomes evaluation included the Japanese Orthopaedic Association (JOA) score, Visual analog scale (VAS) and Neck Disability Index (NDI).

RESULTS

All the patients maintained effective reduction during the follow-up. The anteroposterior and direct distance was significantly higher in modified C2 isthmus screw than C2 PS whether combined with C1 PS or LMS (P < 0.05). The degree of O-C2A, CCA and CMA, JOA score, NDI, and VAS were significantly improved after the surgery (P < 0.05).

CONCLUSIONS

Three-dimensional reduction method with a modified C2 isthmus screw is effective and safe in managing IAAD. It can increase the anteroposterior and vertical distance between the heads of C1 and C2 screws, which is benefit for the three-dimensional reduction operation of IAAD.

An unusual injury mechanism of atlantoaxial dislocation: illustrative case

BACKGROUND

Atlantoaxial dislocation (AAD) is a rare and potentially life-threatening condition. Various underlying mechanisms of injury are described in the literature. Here, the authors report an unusual nontraumatic injury mechanism of AAD in a 12-year-old patient.

OBSERVATIONS

A 12-year-old boy presented with intolerable neck pain and numbness in both upper limbs. The patient’s symptoms had started 2 months after the initiation of online classes during the coronavirus disease 2019 pandemic without a history of trauma. He used a computer for personal study and online classes for prolonged hours with no respite. On physical and radiological evaluation, he was diagnosed with AAD. Before surgery, skull traction was applied to reduce the dislocation and posterior C1 lateral mass screw and C2 pedicle screw fixation was performed. An optimal clinical outcome was achieved with no postoperative complications. A preoperative visual analog scale score of 8.0 was reduced to 0 postoperatively.

LESSONS

A prolonged fixed neck posture is an unusual underlying cause of AAD. Posterior C1 lateral mass and C2 pedicle screw fixation results in an optimal clinical outcome.

Morphometric Analysis of the Lateral Atlantoaxial Joints in Patients with an Old Type II Odontoid Fracture and Atlantoaxial Dislocation: A Study Based on CT Analysis

MINI

The morphological features of the lateral atlantoaxial joints (LAJs) in patients with old type II odontoid fractures and atlantoaxial dislocation have not been fully analyzed. Our study found the changes in morphological features of the LAJs in some patients, and revealed the causes and consequences of the changes in morphological features of the LAJs.

TRAUMATIC ATLANTOAXIAL ROTATORY DISLOCATION IN THE PEDIATRIC POPULATION

ABSTRACT Objective: The treatment of C1-C2 rotatory dislocation remains controversial and surgery is rare. Surgical treatment is indicated when the injury satisfies the instability criteria or when it cannot be reduced. The objective of this study is to analyze the principles and the adaptations necessary for treating these injuries in the pediatric population. Methods: A retrospective case series study. Three cases of patients diagnosed with traumatic C1-C2 rotatory dislocation and treated surgically in our hospital were studied. Through critical analysis of the available literature, a practical guide was proposed to establish the principles and competencies for the treatment of these injuries. Results: The operated cases were female patients between 8 and 16 years of age, with a diagnosis of traumatic atlantoaxial dislocation. Two patients required preoperative skeletal traction with halo. All patients underwent posterior instrumented arthrodesis, two with a transarticular screw technique and one with mass and C2 isthmic (Göel-Harms) screws. Conclusion:. It is essential to determine if the injury is stable and reducible. We recommend treating this type of injury keeping the criteria and competencies related to the stability, alignment, biology and function of the spine in mind. Level of evidence IV; Case series.

A novel surgical protocol for safe and accurate placement of C1 lateral mass screws in patients with atlas assimilation, basilar invagination and atlantoaxial instability: technical details, accuracy assessment and perioperative complications

PURPOSE

To introduce a novel surgical protocol for safe and accurate placement of C1 lateral mass screws in patients with atlas assimilation, basilar invagination and atlantoaxial instability, and to categorize the screw accuracy and perioperative complications regarding this technique in a large case series.

METHODS

Between January 2015 and January 2020, patients who had atlas assimilation, basilar invagination and atlantoaxial instability, and underwent atlantoaxial fixation using C1 lateral mass screws were reviewed. C1 lateral mass screws were placed with a novel surgical protocol following a series key steps, including posterior para-odontoid ligament release, panoramic exposure of the invaginated lateral mass, and diligent protection of the abnormal VA. Screw accuracy and related complications were specifically evaluated.

RESULTS

A total of 434 C1 lateral mass screws were placed. Fifteen screws (3.5%) were classified as unacceptable, 54 screws (12.4%) were classified as acceptable, and 365 screws (84.1%) were classified as ideal. Overall, 96.5% of screws were deemed safe. There were no cases of vascular injury or permanent neurological defects. One patient with an unacceptable screw presented with hypoglossal nerve paralysis and recovered after an immediate revision surgery. Thirty-seven patients complained about occipital neuralgia and were successfully managed with medication.

CONCLUSION

Placement of C1 lateral mass screws in patients with atlas assimilation, basilar invagination and atlantoaxial instability following this surgical protocol is safe and accurate. Thorough para-odontoid ligamental release, wide exposure of the invaginated lateral mass, and diligent protection of the vertebral artery are critical to maximize the chances of successful screw placement.

A novel 3D-printed locking cage for anterior atlantoaxial fixation and fusion: case report and in vitro biomechanical evaluation

BACKGROUND

Treatment of atlantoaxial dislocation is aimed at reduction and stabilization of the atlantoaxial joint. 3D printing refers to a process where additive manufacturing is achieved under precise computer control. Literature on its utilization in anterior atlantoaxial fixation and fusion is rare. This study is the first report on a 3D-printed locking cage used in the anterior procedure for atlantoaxial dislocation.

METHODS

A middle-aged male in his 40s presented with weakness and numbness of his extremities for 3 years and could only walk slowly with assistance. Imaging studies revealed severe anterior migration of C1, irreducible atlantoaxial dislocation, and severe cervical-medullary compression. A preoperative plan consisting of trans-oral soft tissue release and fixation using tailor-designed 3D-printed cages was devised. Following fluoroscopic confirmation of reduction of the atlantoaxial joints, two customized 3D-printed cages made of titanium alloy were inserted into the bilateral facet joints, which were then locked by six screws into the lateral masses of C1 and C2. The microstructure of the inserted cages was optimized for improved biomechanical stability and enhanced osseo-integration, without the need for bone grafting. In addition, a biomechanical test was performed on seven human cadaveric specimens comparing the novel implant with the conventional C1 lateral mass-C2 pedicle screw construct in three modes of motion (flexion-extension, lateral bending, axial rotation).

RESULTS

Improvement of neurologic function in the patient was evident immediately after surgery. He was able to walk independently 1 month post-operatively. At the 12-month follow-up, coronal reconstruction of CT demonstrated properly-positioned 3D-printed cages, evidence of osseo-integration at the bone-implant interface, and no subsidence or displacement of the implant. Eighteen months out of surgery, the mJOA score improved to 15, and lateral X-ray confirmed reduction of atlanto-axial dislocation. Additionally, the new construct provided strong fixation comparable to that conferred by conventional constructs as there was no significant difference observed between the two groups in all three directions of motion.

CONCLUSIONS

The novel implant represents a new option in the treatment of irreducible atlantoaxial dislocation. It can provide strong anterior support for solid fixation and fusion with a low profile and a microstructure that obviates the need for bone grafting.

Surgical treatment of a complex craniocervical malformation combined with posterior cranial fossa teratoma: a case report and literature review

Background

Basilar invagination (BI) with atlantoaxial dislocation (AAD) is not uncommon in patients with scoliosis, Klippel-Feil syndrome (KFS), and other bone deformities. Cases with combinations of the abovementioned dislocations and deformities with posterior cranial fossa teratoma are rare in the clinic and difficult to handle.

Case presentation

This case presents a 34-year-old woman diagnosed with atlantoaxial dislocation and posterior cranial fossa mass. After two surgeries, the posterior cranial teratoma was completely removed with satisfactory atlantoaxial reduction. The postoperative 1-year follow-up examination showed that the bone graft fusion was successful, without remaining significant dysfunction.

Conclusions

The surgical risk of irreducible atlantoaxial dislocation combined with posterior cranial fossa tumor is huge. Thus, it needs to be fully preoperatively evaluated and managed carefully in accordance with sound surgical principles.

Kinematic MRI Analysis of Reducible Atlantoaxial Dislocation for Decompression

Background

Many doctors ignored the possibility that there is still a spinal cord compression (SCC) need for decompression after atlantoaxial reduction. Reduction can be achieved on kinematic magnetic resonance imaging (MRI); thus, we want to analyze the role of kinematic MRI in reducible atlantoaxial dislocation and make a preoperative decision whether to perform decompression.

Methods

36 patients with atlantoaxial reduction on preoperative kinematic MRI in extension postures were enrolled retrospectively. Grouping was based on the condition of SCC after atlantoaxial reduction preoperatively. Group A: patients with SCC after atlantoaxial reduction on dynamic cervical MRI were treated with C1 laminectomy for decompression and atlantoaxial fixation. Group B: patients with no significant SCC, according to dynamic MRI, underwent only atlantoaxial fixation. Clinical outcomes were evaluated using JOA score for spinal cord function. Radiological outcomes were assessed by measuring spinal cord diameter on MRI.

Results

The mean follow-up time was 17.1 months. Postoperative JOA score and percentage of SCC in both groups were significantly better than its preoperative score. There were no significant statistical differences in the JOA score at 12 months after surgery and the JOA improvement rate between two groups. All patients in the two groups had a lower percentage of SCC on preoperative extension MRI, compared with neutral MRI. No significant statistical differences in the spinal decompression improvement rate were observed between the two groups.

Conclusions

Decompression should be performed in patients who still have significant SCC on preoperative kinematic MRI. Kinematic MRI could be used to assess SCC and decide whether to perform decompression preoperatively.

Atlantoaxial dislocation with congenital "sandwich fusion" in the craniovertebral junction: a retrospective case series of 70 patients

BACKGROUND

In the setting of congenital C1 occipitalization and C2-3 fusion, significant strain is placed on the atlantoaxial joint. Vertebral fusion both above and below the atlantoaxial joint (i.e., a "sandwich") creates substantial instability. We retrospectively report on a case series of "sandwich fusion" atlantoaxial dislocation (AAD), describing the associated clinical characteristics and detailing surgical treatment. To the best of our knowledge, the present study is the largest investigation to date of this congenital subgroup of AAD.

METHODS

Seventy consecutive patients with sandwich fusion AAD, from one senior surgeon, were retrospectively reviewed. The clinical features and the surgical treatment results were assessed using descriptive statistics. No funding sources or potential conflict of interest-associated biases exist.

RESULTS

The mean patient age was 42.2 years (range: 5-77 years); 36 patients were male, and 34 were female. Fifty-eight patients (82.9%) had myelopathy, with Japanese Orthopaedic Association (JOA) scores ranging 4-16 (mean: 12.9). Cranial neuropathy was involved in 10 cases (14.3%). The most common presentation age group was 31 to 40 years (24 cases, 34.3%). Radiological findings revealed brainstem and/or cervical-medullar compression (58 cases, 82.9%), syringomyelia (16 cases, 22.9%), Chiari malformation (12 cases, 17.1%), cervical spinal stenosis (10 cases, 14.3%), high scapula deformity (1 case, 1.4%), os odontoideum (1 case, 1.4%), and dysplasia of the atlas (1 case, 1.4%). Computed tomography angiography was performed in 27 cases, and vertebral artery (VA) anomalies were identified in 14 cases (51.9%). All 70 patients underwent surgical treatment, without spinal cord or VA injury. Four patients (5.7%) suffered complications, including 1 wound infection, 1 screw loosening, and 2 cases of bulbar paralysis. In the 58 patients with myelopathy, the mean JOA score increased from 12.9 to 14.5. The average follow-up time was 50.5 months (range: 24-120 months). All 70 cases achieved solid atlantoaxial fusion at the final follow-up.

CONCLUSIONS

Sandwich fusion AAD, a unique subgroup of AAD, has distinctive clinical features and associated malformations such as cervical-medullar compression, syringomyelia, and VA anomalies. Surgical treatment of AAD was associated with myelopathy improvement and minimal complication occurrence.

C2 partial transpedicular screw technique for atlantoaxial dislocation with high-riding vertebral artery: A technique note with case series

OBJECTIVE

Although the C2 pedicle screw (C2PS) is currently the most biomechanically robust option for C2 fixation, the high-riding vertebral artery (HRVA) precludes safe C2PS placement. However, unintentional partial C2 pedicle perforation and vertebral foramen violation due to C2PS placement without neurovascular complications occurred frequently in clinic. Therefore, we have attempted to apply C2 partial transpedicular screw (C2PTS) in patients with HRVA with satisfactory preliminary outcomes. The aim of the present study is to introduce the C2PTS technique and report the preliminary radiological and clinical outcomes of application of C2PTS.

PATIENTS AND METHODS

The data of 15 patients with atlantoaxial dislocation underwent atlantoaxial arthrodesis with posterior screw-rod construct were retrospectively reviewed. All patients had unilateral or bilateral HRVA that precluded safe C2PS placement and C2PTS was used as an alternative. In this technique, a Penfield dissector was used to properly mobilize the HRVA inferiorly to preclude vertebral artery injury and pave the way for C2PTS placement. The C2PTS travelled under the superior border of the isthmus and toward the ipsilateral atlantoaxial articulation. The implant position and atlantoaxial reduction were evaluated using computed tomography (CT) scans and vertebral artery (VA) was assessed using CT angiography postoperatively.

RESULTS

Satisfactory C2PTS placement and atlantoaxial reduction were achieved in all patients. Postoperatively, no vertebral artery injury and implant failure were observed, and bone fusion was achieved in all the patients. Additionally, there were no VA occlusion or stenosis due to screws demonstrated on VA CT angiography.

CONCLUSION

C2PTS can achieve three-column fixation of axis and is an efficient alternative to C2PS which is prohibited due to HRVA; also, gently mobilizing the HRVA inferiorly is mandatory to prevent vertebral artery injury during C2PTS placement.

Clinical Outcomes of Atlantoaxial Dislocation Combined with Osteoporosis Using Posterior Atlantoaxial Rod, Screw Fixation, and Posterior Interfacet Fusion: A Retrospective Study of 21 Cases

Background

Surgical procedures on atlantoaxial dislocation combined with osteoporosis remain controversial. This study was established to assess the mid-term clinical outcomes of atlantoaxial dislocation combined with osteoporosis using posterior atlantoaxial rod, screw fixation and posterior interfacet fusion.

Material/Methods

From January 2017 to January 2020, 21 patients (4 males and 17 females) with coexisting atlantoaxial dislocation and osteoporosis who underwent posterior atlantoaxial rod and screw fixation were included in our study with an average age of 64±8.1 years (range, 57–74 years). The subjective and objective symptoms, together with the neurological function of the patients were measured. Radiography and magnetic resonance imaging (MRI) were performed, Japanese Orthopaedic Association (JOA) score for spinal cord function and VAS score for pain recovery was assessed.

Results

JOA and visual analog scale (VAS) score were significantly improved at 14±5.9 month follow-up compared with pretreatment values. Complete or almost complete anatomical reduction was observed in all 21 patients. All patients had good bony fusion at the final follow-up. No screw-loosening or atlantoaxial redislocation occurred in 21 cases. The only complication was mild numbness in the C2 innervation area of the posterior occipital region in 6 cases, which had no effect on life.

Conclusions

The results suggested that posterior atlantoaxial rod, screw fixation system, and posterior interfacet fusion could achieve satisfactory initial results for the treatment of atlantoaxial dislocation combined with osteoporosis.

Classification of the facets of lateral atlantoaxial joints in patients with congenital atlantoaxial dislocation

PURPOSE

To investigate the morphological characteristics and para-positions of the facets of lateral atlantoaxial joints (FLAJs) in patients with congenital atlantoaxial dislocation (CAAD) and to propose a classification system for the FLAJs.

METHODS

A total of 93 cases of CAAD were included in this retrospective study. The obliquity and slippage of the FLAJs in the sagittal and coronal planes were measured and observed in the CT images of all of the cases. The obliquity and slippage of the FLAJs represented the morphological characteristics and the para-positions, respectively, and were used as classification parameters. Accordingly, a classification system for the FLAJs was established. We additionally investigated the correlation between the classifications of the FLAJs and various types of CAAD. The classifications of the FLAJs in 34 patients with irreducible AAD (IAAD) were also investigated.

RESULTS

One hundred eighty-six FLAJs in 93 patients were classified into 6 types (namely, A, B1, B2, C, D1, and D2) for obliquity and 3 types (namely, S₀, S₁, and S₂) for slippage. Among the 186 FLAJs, type B1 and type S₀ were the most common obliquity and slippage types, respectively. There were 11 combination types for obliquity and 5 combination types for slippage of bilateral FLAJ in 93 patients. Most of the patients (69.7%, 47/70) with anteroposterior AAD had accompanying slippage and anteversion of the FLAJ in the sagittal plane. Rotational AAD was found in 10 patients with asymmetrical slippage in both FLAJs in the sagittal plane. Lateral translational AAD was found in 6 patients with an S₁-type FLAJ in the coronal plane. In 5 patients with lateral angular AAD, FLAJs of types D1 and S₂ were observed on one side. Among the 34 patients with IAAD, 31 patients had both obliquity and slippage in the FLAJs on one or both sides.

CONCLUSION

The morphological characteristics and para-positions of the FLAJs on both sides largely determine the types of AAD in patients with CAAD. The types of obliquity and slippage of the FLAJ are related to the reducibility of AAD.

Treatment of irreducible atlantoaxial dislocation using one-stage retropharyngeal release and posterior reduction

INTRODUCTION

Irreducible atlantoaxial dislocation (IAAD) has been challenging for spine surgeons. Various methods have been used to treat IAAD, but no consensus has been reached. This study aimed to retrospectively analyze the efficacy of anterior submandibular retropharyngeal release and posterior reduction and fixation for IAAD.

METHODS

From March 2007 to May 2015, 13 patients diagnosed with IAAD underwent anterior submandibular retropharyngeal release and sequential posterior reduction and fixation. The operation time, blood loss, postoperative complications, and Japanese Orthopaedic Association (JOA) scores were retrospectively recorded.

RESULTS

The surgeries were accomplished successfully. The mean operative time was about 3.8 h. The mean estimated blood loss was about 130 mL. The patients experienced postoperative pharyngeal pain. Only one patient had a vague voice and increased oral discharge postoperatively. At the final follow-up, JOA scores had significantly increased (p < 0.05), and all the patients had solid bony fusion.

CONCLUSION

The present study reinforces the efficacy and safety of anterior submandibular retropharyngeal release and posterior reduction and fixation for IAAD. It can achieve satisfactory clinical outcomes and is safe for experienced spine surgeons.

Design a novel integrated screw for minimally invasive atlantoaxial anterior transarticular screw fixation: a finite element analysis

PURPOSE

To design a new type of screw for minimally invasive atlantoaxial anterior transarticular screw (AATS) fixation with a diameter that is significantly thicker than that of traditional screws, threaded structures at both ends, and a porous metal structure in the middle. The use of a porous metal structure can effectively promote bone fusion and compensate for the disadvantages of traditional AATSs in terms of insufficient fixation strength and difficulty of bone fusion. The biomechanical stability of this screw was verified through finite element analysis. This instrument may provide a new surgical option for the treatment of atlantoaxial disorders.

METHODS

According to the surgical procedure, the new type of AATS was placed in a three-dimensional atlantoaxial model to determine the setting of relevant parameters such as the diameter, length, and thread to porous metal ratio of the structure. According to the results of measurement, the feasibility and safety of the new AATS were verified, and a representative finite element model of the upper cervical vertebrae was chosen to establish, and the validity of the model was verified. Then, finite element-based biomechanical analysis was performed using three models, i.e., atlantoaxial posterior pedicle screw fixation, traditional atlantoaxial AATS fixation, and atlantoaxial AATS fixation with the new type of screw, and the biomechanical effectiveness of the novel AATS was verified.

RESULTS

By measuring the atlantoaxial parameters, the atlantoaxial CT data of the representative 30-year-old normal adult male were selected to create a personalized 3D printing AATS screw. In this case, the design parameters of the new screw were determined as follows: diameter, 6 mm; length of the head thread structure, 10 mm; length of the middle porous metal structure, 8 mm (a middle porous structure containing an annular cylinder ); length of the tail thread structure, 8 mm; and total length, 26 mm. Applying the same load conditions to the atlantoaxial complex along different directions in the established finite element models of the three types of atlantoaxial fusion modes, the immediate stability of the new AATS is similar with Atlantoaxial posterior pedicle screw fixation.They are both superior to traditional atlantoaxial anterior screw fixation.The maximum local stress on the screw head in the atlantoaxial anterior surgery was less than those of traditional atlantoaxial anterior surgery.

CONCLUSIONS

By measuring relevant atlantoaxial data, we found that screws with a larger diameter can be used in AATS surgery, and the new AATS can make full use of the atlantoaxial lateral mass space and increase the stability of fixation. The finite element analysis and verification revealed that the biomechanical stability of the new AATS was superior to the AATS used in traditional atlantoaxial AATS fixation. The porous metal structure of the new AATS may promote fusion between atlantoaxial joints and allow more effective bone fusion in the minimally invasive anterior approach surgery.

Surgical treatment of atlantoaxial subluxation by intraoperative skull traction and C1-C2 fixation

Background

Atlantoaxial subluxation (AAS) is a not rare abnormality between the atlas (C1) and axis (C2). For AAS patients with persistent neck pain and neurologic symptoms, surgical intervention is a good choice. Nevertheless, there were still few reports about the use of intraoperative skull traction and different fixation methods in treatment of AAS.

Methods

From January 2012 to December 2018, a total of 86 cases were admitted to our hospital and diagnosed as AAS. All the patients received atlantoaxial reduction with the help of intraoperative skull traction and C1-C2 fixation. Clinical and radiological parameters were collected through chart review.

Results

There were 86 cases included in this study. The mean operative time was 153.9 ± 73.9 min, and the mean amount of intraoperative blood loss was 219.1 ± 195.6 ml. 81 patients underwent posterior reduction, internal fixation and fusion. 5 patients underwent anterior release, followed by posterior internal fixation and fusion. 82 patients got satisfactory postoperative outcomes while complications occurred in 4 patients. Significant neurologic improvement was observed in these patients. Bone fusion was achieved on the midline sagittal reconstructed CT images at the latest follow-up in all these patients except 1 case. All the patients were followed up for 34.84 ± 15.86 months at average (range 12–60 months). The mean ADI value was 7.55 ± 1.67 mm at average preoperatively, and improved to 4.03 ± 1.21 mm postoperatively, and to 4.21 ± 0.99 mm at the latest follow-up. The mean A-A angle was 15.48 ± 9.82 degrees at average preoperatively, and improved to 21.61 ± 10.43 degrees postoperatively, and to 19.73 ± 8.13 degrees at the latest follow-up. The mean A-A height was 35.61 ± 7.66 mm at average preoperatively, and improved to 40.08 ± 8.5 mm postoperatively, and to 38.83 ± 6.97 mm at the latest follow-up. There were complications in 4 patients, including pedicle misplacement, pedicle screw fracture, infection and one death.

Conclusion

Intraoperative skull traction can effectively facilitate the surgical procedures for ASS caused by different etiologies. Further research will be needed to investigate the safety and effectiveness of this method in the future.

C1-C2 Pedicle Screw Fixation for Pediatric Atlantoaxial Dislocation: Initial Results and Long-term Follow-up

BACKGROUND

There are few studies reporting the use of atlantoaxial pedicle screws and the long-term effects of C1-C2 posterior fusion in children. Our study is to investigate the initial results of C1-C2 pedicle screw fixation for pediatric atlantoaxial dislocation (AAD) and assessed spontaneous change of postoperative radiography after a long-term follow-up period.

METHODS

Posterior pedicle screw fixations were performed in 21 pediatric patients with AAD. All the patients underwent implant removal 1 year after their initial surgery and had regular follow-up with an average duration of 76.4 months (range, 52 to 117 mo). Clinical and radiographic data were then collected and compared.

RESULTS

Frankel Grade was significantly improved at 3 months follow-up compared with pretreatment values. All patients had good bony fusion at a mean of 4.2±0.9 months (range, 3 to 6 mo) after treatment. None of the patients experienced worsening neurological symptoms or injury to the vertebral artery. However, 2 cases experienced minor complications. Following removal of the implants, no spinal deformities or subaxial instabilities were found. The mean angle of sagittal curvature increased from 12.1±2.4 degrees (range, 0 to 22 degrees) immediately postoperatively to 19.1±2.7 degrees (range, 6 to 31 degrees) at the final follow-up (P>0.05).

CONCLUSIONS

The results demonstrated that C1-C2 pedicle screw fixation could achieve satisfactory initial results for the management of the pediatric AAD. Moreover, removal of the metal implant after bony fusion did not increase the risk of spinal deformity or subaxial instability at long-term follow-up.

Ankylosing Spondylitis Complicated with Atlantoaxial Dislocation and Destruction of the Dens and Lateral Atlantoaxial Joint: A Case Report

CASE

Non-neoplastic bone destruction, known as Andersson lesion, is not rare in ankylosing spondylitis (AS) and always appeared as bone destruction and sclerosis in the vertebral body-intervertebral disc region. The Andersson lesion has been reported mostly in the thoracic and lumbar spine and rarely in the lower cervical spine. We surgically treated a patient with AS complicated with atlantoaxial dislocation and destruction of dens and lateral atlantoaxial joint, which was similar to the Andersson lesion.

CONCLUSIONS

AS can cause destructive lesion in the upper cervical spine. Posterior reduction, removal of the lesion, and fusion were possible approaches for the treatment of this destructive lesion.

Posterior Screw-Rod Fixation and Selective Axial Loosening for the Treatment of Atlantoaxial Instability or Dislocation Caused by Os Odontoideum: A Case Series for a Single Posterior Approach

OBJECTIVE

To evaluate the effect of screw-rod fixation and selective axial loosening in the treatment of atlantoaxial instability or dislocation (including reducible and irreducible) caused by os odontoideum (OO) via a single posterior approach.

METHODS

A consecutive series of patients with OO surgically treated in our hospital were retrospectively analyzed. For atlantoaxial instability and reducible atlantoaxial dislocation, C1-C2 screw-rod fixation and fusion were performed. OO combined with irreducible atlantoaxial dislocation was reduced after posterior axial loosening, followed by screw-rod fixation and fusion. The general information, clinical data, and radiographic data were compared between the 2 different procedures.

RESULTS

There were 41 patients with an average age of 40.6 ± 21.7 years. All the patients underwent posterior reduction and C1-2 screw rod fixation, 6 with axial loosening and 35 without axial loosening. The clinical manifestations and radiographic data significantly improved after the operation with a low rate of complications. Except for clivus-canal angle and visual analogue score of cervical pain, there were no differences in clinical and radiographic data between the 2 procedures.

CONCLUSIONS

Posterior screws-rod fixation and selective axial loosening is appropriate for treating OO complicated with atlantoaxial instability or dislocation (including reducible and irreducible) without the need for anterior decompression.

The Value and Limitation of Cervical Traction in the Evaluation of the Reducibility of Atlantoaxial Dislocation and Basilar Invagination Using the Intraoperative O-Arm

OBJECTIVE

To assess the value and limitation of cervical traction in the evaluation of the reducibility of atlantoaxial dislocation (AAD) and basilar invagination (BI) using the intraoperative O-arm.

METHODS

A total of 22 patients with hyperextensive, irreducible AAD were included. The cervical traction test under general anesthesia was performed, and the degree of reduction was evaluated using the O-arm before the operation started. The traction effects both vertically and horizontally were evaluated. All cases then underwent modified direct posterior reduction and fixation. Clinical outcomes were evaluated using the Japanese Orthopaedic Association (JOA) scale. Radiologic measurements included the anterior atlantodental interval, the distance of odontoid tip above Chamberlain line, and the clivus-canal angle. Magnetic resonance imaging signal changes, size of syringomyelia, and the space ventral to medulla also were used to evaluate the postoperative reduction result.

RESULTS

After the cervical traction test, 7 patients achieved incomplete reduction, 5 achieved only vertical reduction, 6 achieved only horizontal reduction, and 4 achieved complete reduction in both horizontal and vertical orientations as assessed by the O-arm. All patients underwent a direct reduction technique. The mean JOA score increased from 11.1 to 14.5. Complete reduction of AAD and BI were achieved in 19 patients (86.4%), with partial reduction achieved in 3 (13.6%). Sufficient cerebrospinal fluid space anterior to the medulla with improved JOA score was achieved in the 3 partially reduced patients.

CONCLUSIONS

With the innovations of direct posterior reduction techniques, cervical traction under anesthesia may not sufficiently predict the reducibility of BI and AAD. Cervical traction still plays an important role during the direct posterior reduction procedure.

Impact of the occiput and external acoustic meatus to axis angle on dysphagia in patients suffering from anterior atlantoaxial subluxation after occipitocervical fusion

BACKGROUND CONTEXT

Dysphagia is a complication that sometimes occurs after occipitocervical fusion (OCF). An appropriate O-C2 angle (O-C2a) is recognized as a critical factor for preventing dysphagia. The occiput and external acoustic meatus to axis angle (O-EAa) has some advantages over the O-C2a and is now recognized to outperform O-C2a in predicting dysphagia. However, there are no data on this topic from patients with anterior atlantoaxial subluxation (AAS).

PURPOSE

To evaluate the relationship between the O-EAa and dysphagia in patients suffering from AAS after OCF surgery.

STUDY DESIGN

A retrospective clinical study.

PATIENT SAMPLE

Data from 22 consecutive AAS patients who had undergone OCF were reviewed retrospectively.

OUTCOME MEASURES

The outcome measures included the O-EAa, O-C2a, the narrowest oropharyngeal airway space (nPAS), and the morbidity of dysphagia after OCF.

METHODS

Between September 2011 and September 2017, data from 22 consecutive AAS patients who had undergone OCF were reviewed retrospectively. The patients were divided into two groups according to whether they had suffered postoperative dysphagia by face-to-face questioning or telephone interview. Lateral radiographs were analyzed to determine the pre- and postoperative O-EAa, O-C2a, angle formed by the inferior endplate of C2 and the EA-line (C2Ta), and smallest anteroposterior diameter of the oropharynx between the levels of the uvula and the tip of the epiglottis (nPAS).

RESULTS

The incidence of dysphagia after OCF was 18.18% (4/22). The pre- and postoperative mean nPAS values were significantly different between the groups (p<.05). The postoperative mean O-EAa of the group with dysphagia was significantly smaller than that of the group without dysphagia (p<.05). The mean change in nPAS was significantly larger in the group with dysphagia than that in the group without dysphagia (p<.05). The changes in the O-EAa, O-C2a, and nPAS were linearly correlated within patients. The marginal R² values for the patients were 0.452 and 0.202 for the O-EAa and O-C2a, respectively.

CONCLUSIONS

The O-EAa impacts dysphagia in patients with AAS after OCF. Measuring this angle intraoperatively may be a simple and effective procedure. The O-EAa may be used as a practical index to avoid postoperative dysphagia in patients with AAS after OCF.

Thrombolysis for atlantoaxial dislocation mimicking acute ischemic stroke

The frequency of stroke mimics among stroke patients has been reported to be up to 30%, and that in patients who receive thrombolytic therapy ranges between 1% and 16%. Atlantoaxial dislocation with myelopathy mimicking stroke is extremely rare. An 83-year-old man with a history of old cerebellar infarction presented to the emergency department with acute left hemiplegia after a chiropractic manipulation of the neck and back several hours before symptom onset. Mild hypoesthesia was observed on his left limbs. No speech disturbance, facial palsy, or neck or shoulder pain was observed. Intravenous thrombolytic treatment was given 238 min after symptom onset. Brown-Sequard syndrome subsequently developed 6 h after thrombolysis with a hypoesthetic sensory level below the right C5 dermatome. An emergent brain magnetic resonance angiography did not reveal an acute cerebral infarct but rather an atlantoaxial dislocation causing upper cervical spinal cord compression. Clinical symptoms did not deteriorate after thrombolysis. He received successful decompressive surgery 1 week later, and his muscle power gradually improved, with partial dependency when performing daily living activities 2 months later. A literature review revealed that only 15 patients (including the patient mentioned here) with spinal disorder mimicking acute stroke who received thrombolytic therapy have been reported. Atlantoaxial dislocation may present as acute hemiplegia mimicking acute stroke, followed by Brown-Sequard syndrome. Inadvertent thrombolytic therapy is likely not harmful for patients with atlantoaxial dislocation-induced cervical myelopathy. The neurological deficits of patients should be carefully and continuously evaluated to differentiate between stroke and myelopathy.

Biomechanical Rationale for the Development of Atlantoaxial Instability and Basilar Invagination in Patients with Occipitalization of the Atlas: A Finite Element Analysis

OBJECTIVE

Occipitalization of the atlas (OA) often is associated with atlantoaxial dislocation and basilar invagination. The purpose of this study is to determine the biomechanical difference between normal and OA conditions in the craniovertebral junction and to further explore the rationale for development of atlantoaxial dislocation and basilar invagination using the finite element model (FEM).

METHODS

A ligamentous, nonlinear, sliding-contact, 3-dimensional FEM of the occipitoatlantoaxial complex was generated. Validation of the model was accomplished by comparing kinematic predictions with experimental data. We defined the atlantooccipital joint as a tie contact to simulate the OA deformity. The range of motion and the value of the maximum Von Mises stress were compared between the intact and OA models.

RESULTS

We found all of the predicted data in the intact FEM fell within 1 standard deviation of the cadaver data for all 6 loadings. The OA simulation significantly reduced the overall range of motion of the occipitoatlantoaxial complex at all loadings. The maximum Von Mises stress was predicted to increase at the transverse ligament and the superior articular facet of the axis for all the flexion, extension, lateral bending, and axial rotation loadings.

CONCLUSIONS

The OA could result in hypermobility of the atlantoaxial segment and cause overstress in the transverse ligament and the lateral atlantoaxial joints. These changes explain the pathogenesis of atlantoaxial dislocation and basilar invagination associated with OA. Follow-up should be scheduled regularly due to the nature of the dynamic development of atlantoaxial dislocation and basilar invagination.