Irreducible Atlantoaxial Dislocation Research Articles

A Novel Stepwise Technique for Safe and Effective Transoral Release of Irreducible Atlantoaxial Dislocation: A Retrospective Study of 201 cases.

Retrospective cohort study. To verify the clinical efficacy of a novel Transoral Stepwise Release Technique (TSRT) for treatment of irreducible atlantoaxial dislocations (IAAD). Anterior release for IAAD remains challenging, with 3.2 times higher complication rate than posterior release. However, there are some patients who cannot achieve successful reduction from a posterior approach, and require the higher-risk anterior release. Our work presents a novel anterior release technique that aims to minimize iatrogenic injury and associated complications from an anterior release. IAAD cases who were treated with TSRT were retrospectively studied. Primary outcomes included fusion rate, complications, and neurological function over the course of minimum one-year follow-up. Radiographic differences between preoperative and postoperative imaging were also considered. A preoperative prediction model for the actual release grade was developed using multivariate logistic regression based on demographic factors and the craniovertebral abnormalities identified on preoperative images, evaluating the need for higher-grade TSRT release. We included 201 IAAD cases, with 42% (84/201) demonstrating degeneration of the atlantoaxial joint or anterior-hook-like dens. Reduction was achieved in all cases, with 80% (160/201) of cases only requiring relatively low-grade (grade I) TSRT release. Degeneration of the atlantoaxial joint was significantly associated with the need for higher-grade TSRT release (OR 16.68, CI: 2.91-94.54, P=0.002). The overall complication rate was 4.5% (9/201). Over the course of follow-up, the fusion rate reached 98.5%, and the ASIA and JOA score were significantly improved to 97.28 and 16.25 (P<0.01 and P<0.01), respectively. This study demonstrated that our novel TSRT anterior release technique demonstrated complication rates similar to those published in the literature for posterior release. TSRT can be used as an alternative to posterior release techniques for refractory cases or when a posterior approach is not considered viable.

Effect of a new type of head and neck fixation and traction device in the surgical treatment of patients with irreducible atlantoaxial dislocation

BackgroundIn order to improve the clinical medical technology, enhance the clinical effect and improve the disease detection rate, the clinical incidence rate of atlantoaxial dislocation and vertebral body malformation that are difficult to summarize is increasing year by year.MethodsA total of 80 patients with atlantoaxial dislocation deformity treated in our hospital from January 2017 to May 2021 are selected for this study. According to the number table method, 80 patients are randomly divided into the auxiliary group and the traditional group, with 40 cases in each group. The traditional group is treated with posterior atlantoaxial pedicle screw system internal fixation and intervertebral fusion, and the auxiliary implementation and application of a new head and neck fixation and traction device through nasal cannula and oral release decompression fixation for posterior fusion. The patients in the two groups are compared changes and differences in efficacy, spinal cord function index, pain score, surgery, and quality of life.ResultsCompared with the traditional group, the total clinical effective rate, cervical spine extension and flexion range of motion, physical function, physical function, psychological function, and social function in the auxiliary group are significantly improved. The operation time, intraoperative blood loss, and VAS score are significantly reduced (P < 0.05).ConclusionThe new head and neck fixation traction device can improve the surgical efficacy and quality of life of patients with irreversible atlantoaxial dislocation, enhance spinal cord function, reduce pain symptoms and surgical risks, and is worthy of clinical application.

Transoral Surgery for Irreducible Atlantoaxial Dislocation Complicated by Concomitant Aberrant Internal Carotid Arteries.

Transoral Surgery for Irreducible Atlantoaxial Dislocation Complicated by Concomitant Aberrant Internal Carotid Arteries.

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

BackgroundThere are many classification systems for atlantoaxial dislocation (AAD). Among these systems, the definitions of irreducible AAD remain vague, and its treatments are not unified.ObjectiveTo explore the surgical strategies and efficacy for the treatment of os odontoideum (OO) with AAD.MethodsThe 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.ResultsThere 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).ConclusionOO 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.

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

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

The clinical validity of atlantoaxial joint inclination angle and reduction index for atlantoaxial dislocation.

Atlantoaxial dislocation patients with neurological defects require surgery. Sometimes, release surgery is necessary for irreducible atlantoaxial dislocation to further achieve reduction. Whether release surgery is essential relies on the surgeon's experience and lacks objective reference criteria. To evaluate the value of atlantoaxial joint inclination angle (AAJI) in sagittal and coronal planes and reduction index (RI) in the surgical approach selection for atlantoaxial dislocation. Retrospectively analyzed 87 cases (42 males and 45 females, 9-89 years) of atlantoaxial dislocation from January 2011 to November 2020. In addition, 40 individuals without atlantoaxial dislocation were selected as the control group. Imaging parameters were compared between the two groups. According to surgical methods, the experiment group was divided into two groups including Group A(release surgery group) and Group B (conventional operation group). The parameters were measured based on CT and x-ray. The relevant imaging parameters and clinical scores, including the AAJI in sagittal and coronal planes, the atlas-dens interval (ADI) before and after traction, the RI, and JOA scores were measured and analyzed. The sagittal and coronal atlantoaxial joint inclination angles(SAAJI and CAAJI) in the control group were 7.91 ± 0.42(L), 7.99 ± 0.39°(R), 12.92 ± 0.41°(L), 12.97 ± 0.37°(R), in A were 28.94 ± 1.46°(L), 28.57 ± 1.55°(R), 27.41 ± 1.29°(L), 27.84 ± 1.55°(R), and in B were 16.16 ± 0.95°(L), 16.80 ± 1.00°(R), 24.60 ± 0.84°(L), 24.92 ± 0.93°(R) respectively. Statistical analysis showed that there was a statistical difference in the SAAJI between the control group and the experiment group (P < 0.01), as well as between groups A and B (P < 0.01). The RI in groups A and B was 27.78 ± 1.46% and 48.60 ± 1.22% respectively, and there was also a significant difference between the two groups (P < 0.01). There was negative correlation between SAAJI and RI. The SAAJI and RI can be used as objective imaging indexes to evaluate the reducibility of atlantoaxial dislocation. And these parameters could further guide the selection of surgery methods. When the RI is smaller than 48.60% and SAAJI is bigger than 28.94°, anterior release may be required.

Surgical Management Of Irreducible Atlanto-Axial Dislocation With OS Odontoideum And Klippel-Feil Syndrome.

Klippel-Feil syndrome (KFS) is the congenital fusion of two or more cervical vertebrae which is often associated with various other abnormalities in the cervical spine. Involvement the upper cervical segments leads to atlanto-axial instability which manifests as progressive neurological symptoms due to compression on the spinal cord. These cases pose a surgical challenge due the abnormal and unique anatomy of each patient. A 37-year-old patient presented with neck pain and cervical myelopathy due to a posterior subluxation of C2-3 fused segment over C4-6 fused segment. The patient had an os odontoideum, incomplete posterior arch of C1, anomalous course of vertebral artery and C3 hemi-vertebra. The patient was successfully managed with transoral odontoidectomy and occipeto-cervical fusion. Irreducible atlanto-axial dislocation in a patient with an abnormal upper cervical spine anatomy may require transoral decompression followed by posterior fusion.

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

Investigate a novel method for treating irreducible atlantoaxial dislocation (IAAD) or with basilar invagination (BI) by bony deformityosteotomy, remodeling, releasing, and plate fixating through transoral approach. 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. The operation time was 144 [Formula: see text] 25min with blood loss of 102 [Formula: see text] 35ml. The average pre-operative ADI improved from 7.5 [Formula: see text] 3.2mm pre-surgery to 2.5 [Formula: see text] 1.5mm post-surgery (p < 0.05). The average VDI improved from 12.3 [Formula: see text] 4.8mm pre-surgery to 3.3 [Formula: see text] 2.1mm 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. In addition to soft tissue factors, bony obstruction was another important factor impeding atlantoaxial reduction. Transoral bony deformity osteotomy, remodeling, releasingcombined withplate fixating was effective in treating IAAD/BI with bony obstruction factors.

Open Reduction for Potentially Reducible Atlantoaxial Dislocation Secondary to Transverse Ligament Laxity in Patients with Rheumatoid Arthritis

Atlantoaxial dislocation (AAD) is classified into reducible AAD and irreducible AAD (IRAAD). Anterior or posterior releasing followed by occipitocervical/atlantoaxial fusion is often performed for IRAAD, but is technically demanding. This study aimed to evaluate the results of the posterior open reduction technique without releasing the atlantoaxial joint in the treatment of potentially reducible AAD (PRAAD) caused by transverse ligament laxity in patients with rheumatoid arthritis (RA). Data from 38 RA patients who experienced PRAAD due to transverse ligament laxity were retrospectively reviewed. They all underwent posterior open reduction and fusion without releasing the atlantoaxial joint. Outcomes were evaluated by using atlantodental interval, modified Japanese Orthopedic Association scores, Nurick grade, Neck Disability Index, and visual analog scale score for neck pain. All the patients achieved solid bone fusion at follow-up. The mean atlantodental interval was reduced to 5.6±0.7mm and 2.1±0.5mm after traction and operation, respectively, from a preoperative score of 8.2±0.6mm(P<0.05). Compared with the respective preoperative values, the mean modified Japanese Orthopedic Association score and Nurick grade were significantly increased at the final follow-up (both P<0.05), whereas the Neck Disability Index and visual analog scale score for neck pain were significantly decreased (both P<0.05). AAD with partial reduction after skeletal traction for 48hours should be defined as PRAAD, not IRAAD. Open reduction with a C1-C2 pedicle screw-rod system can be safely and effectively applied in the treatment of PRAAD due to transverse ligament laxity in patients with RA.

Arterial Fencing: A Challenge During Complex Craniovertebral Junction Surgery

A 32-year-old woman presented with chronically progressive spastic quadriparesis. Detailed clinicoradiological evaluation led to the diagnosis of irreducible atlantoaxial dislocation and basilar invagination, with associated "kissing" carotids and an anomalous right vertebral artery (VA). Both internal carotid arteries had an abnormally tortuous course, "kissing" retropharyngeally at the level of C1-C2. The right VA became intradural at the level of C2-C3, an extremely rare anomaly-C3 segmental artery. Despite the deformed joints and the possibility of injuring the anomalous right VA during C2-C3 instrumentation, a tailored posterior-only approach was used to circumvent the arterial fence created by both vascular anomalies. The patient underwent bilateral C1-C2 joint opening and left C1-C2 joint spacer placement, followed by bilateral occipito-C3-C4 fixation. This is possibly the first reported case of a complex craniovertebral junction anomaly associated with both kissing carotids and a C3 segmental VA.

Posterior one is not the only approach: Ventral odontoid decompression in the spectrum of complex irreducible atlantoaxial dislocation with basilar invagination-When and why?

Posterior one is not the only approach: Ventral odontoid decompression in the spectrum of complex irreducible atlantoaxial dislocation with basilar invagination-When and why?

Efficacy of a Lateral Mass Fusion Device Combined with a Three-Dimensional–Printed Model in the Treatment of Craniovertebral Junction Abnormalities

To investigate the efficacy of a lateral mass fusion device combined with a three-dimensional-printed model in treatment of craniovertebral junction abnormalities. This retrospective study comprised 56 patients with irreducible atlantoaxial dislocation who underwent posterior fixation between January 2016 and December 2019. Patients were divided into 2 groups according to whether or not cages were used-cage group and autograft group. Visual analog scale score, Japanese Orthopaedic Association score, health-related quality of life, American Spinal Injury Association spinal cord injury grade, atlas-dens interval, space available for the cord, cervicomedullary angle, and fusion rate were compared between groups. Medical follow-up was >1 year. There was no statistical difference between groups in preoperative visual analog scale score, Japanese Orthopaedic Association score, 12-Item Short Form Health Survey score, American Spinal Injury Association grade, atlas-dens interval, space available for the cord, and cervicomedullary angle, and these indexes significantly improved after surgery (P < 0.05). Visual analog scale score and atlas-dens interval were lower in the cage group than in the autograft group (P < 0.05). Japanese Orthopaedic Association score, 12-Item Short Form Health Survey score, space available for the cord, and cervicomedullary angle were significantly higher in the cage group than in the autograft group (P < 0.05). Fusion rate of the cage group 4-6 months after surgery was higher than that of the autograft group (P= 0.068). American Spinal Injury Association grade was significantly higher in the cage group than in the autograft group (P < 0.05). During 1-year follow-up, neurological function improvement and atlantoaxial joint reduction were satisfactory. The lateral mass fusion device combined with a three-dimensional printed model may be a clinically useful technique.

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

BackgroundThree-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.MethodsTwelve 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).ResultsAll 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).ConclusionsThree-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.

Usefulness of a Three-Dimensional-Printed Model in the Treatment of Irreducible Atlantoaxial Dislocation with Transoral Atlantoaxial Reduction Plate.

ObjectiveTo evaluate the usefulness of a 3D‐printed model for transoral atlantoaxial reduction plate (TARP) surgery in the treatment of irreducible atlantoaxial dislocation (IAAD).MethodsA retrospective review was conducted of 23 patients (13 men, 10 women; mean age 58.17 ± 5.27 years) with IAAD who underwent TARP from January 2015 to July 2017. Patients were divided into a 3D group (12 patients) and a non‐3D group (11 patients). A preoperative simulation process was undertaken for the patients in the 3D group, with preselection of the TARP system using a 3D‐printed 1:1 scale model, while only imaging data was used for the non‐3D group. Complications, clinical outcomes (Japanese Orthopaedic Association [JOA] and visual analogue score [VAS]), and image measurements (atlas–dens interval [ADI], cervicomedullary angle [CMA], and clivus‐canal angle [CCA]) were noted preoperatively and at the last follow up.ResultsA total of 23 patients with a follow‐up time of 16.26 ± 4.27 months were included in the present study. The surgery duration, intraoperative blood loss, and fluoroscopy times in the 3D group were found to be shorter than those in non‐3D group, with statistical significance. The surgery duration was 3.29 ± 0.45 h in the 3D group and 4.68 ± 0.90 h in the non‐3D group, and the estimated intraoperative blood loss was 131.67 ± 43.03 mL in the 3D group and 185.45 ± 42.28 mL in the non‐3D group. No patients received blood transfusions. The intraoperative fluoroscopy times were 5.67 ± 0.89 in the 3D group and 7.91 ± 1.45 in the non‐3D group. Preoperatively and at last follow up, JOA and VAS scores and ADI, CCA, and CMA were improved significantly within the two groups. However, no statistical difference was observed between the two groups. However, surgical site infection occurred in 1 patient in the 3D group, who underwent an emergency revision operation of the removal of TARP device and posterior occipitocervical fixation; the patient recovered 2 weeks after the surgery. In 2 patients in the traditional group, a mistake occurred in the placement of screws, with no neurological symptoms related to the misplacement.ConclusionPreoperative surgical simulation using a 3D‐printed real‐size model is an intuitive and effective aid for TARP surgery for treating IAAD. The 3D‐printed biomodel precisely replicated patient‐specific anatomy for use in complicated craniovertebral junction surgery. The information was more useful than that available with 3D reconstructed images.

Transoral release to realign postoperative loss of reduction following occipitocervical fixation for congenital basilar invagination.

Revision surgery in an irreducible atlantoaxial dislocation (IAAD) previously operated with a posterior approach is challenging. Multiple modalities using anterior, posterior, and dual approaches have been described. We report a so far unreported technique of revision surgery by posterior implant removal and decompression with anterior transoral release followed by posterior instrumentation. 14-year male with basilar invagination (BI) with IAAD, previously operated with posterior decompression and instrumented occipitocervical fusion presented three months later with post-traumatic recurrence of myelopathy with quadriparesis with Di Lorenzo grade 4 and loss of reduction. He was operated with a posterior implant and early fusion mass removal with extended foramen magnum decompression (FMD), followed by anterior transoral release with a satisfactory reduction on traction, and finally, a posterior revision instrumented occipitocervical fusion. At 2-year follow-up, the patient was symptom-free with Di Lorenzo grade 1 and cervicomedullary angle improvement from 97.4° to 141.2°; achieving bony fusion. Single-stage posterior-anterior transoral-posterior approach can be used to achieve satisfactory reduction for a revision BI with IAAD with prior posterior instrumentation.

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

BackgroundTreatment 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.MethodsA 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).ResultsImprovement 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.ConclusionsThe 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

BackgroundBasilar 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 presentationThis 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.ConclusionsThe 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.

Nasoseptal flap revision in endoscopic endonasal odontoidectomy for acute atlantoaxial osteomyelitis with atlantoaxial subluxation

Vertebral osteomyelitis compromises approximately 1%–7% of all cases of osteomyelitis, whereas the cervical region is affected in 3%–10% of all cases. Not surprisingly, osteomyelitis at the craniocervical junction is a rare occurrence that poses certain challenge to surgeons. With the advancement of antibiotics, most patients with vertebral osteomyelitis can be successfully treated by conservative treatment. However, surgical intervention is indicated in cases presented with neurological deficits, spinal deformity, or instability. We present one case of retropharyngeal abscess involving the craniocervical junction that led to irreducible atlantoaxial rotatory dislocation and significant ventral cord compression. Staged procedures with endoscopic endonasal odontoidectomy assisted by nasoseptal flap reconstruction for decompression and posterior occipitocervical fusion were arranged in sequence. Nevertheless, postoperative magnetic resonance imaging revealed incomplete decompression at C2 level of the cervical spine. Prompt revision surgery with nasoseptal flap takedown and reuse performed uneventfully. The patient recovered well and was able to ambulate 5 weeks later. This case illustrated long-term radionecrosis complicated with osteomyelitis and craniocervical instability. An aggressive surgical decompression followed by staged spinal fusion would be beneficial in such complex osteomyelitis cases.

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.