Reduction techniques in the management of atlantoaxial subluxation

Background:

The traditional approach to atlantoaxial subluxation which is irreducible after traction is transoral decompression and reduction or odontoid excision and posterior fixation. Transoral approach is associated with comorbidities. However using a posterior approach a combination of atlantoaxial joint space release and a variety of manipulation procedures, optimal or near optimal reduction can be achieved. We analysed our results in this study based on above procedure.

Materials and Methods:

66 cases treated over a 5 year period were evaluated retrospectively. Three cases treated by occipito cervical fusion were not included in the study. The remaining 63 cases were classified into three types. All except two cases were subjected to primary posterior C1-C2 joint space dissection and release followed by on table manipulation which was tailored to treat the type of atlantoaxial subluxation. Optimal or near optimal reduction was possible in all cases. An anterior transoral decompression was needed only in two cases where a bony growth (callus) between the C1 anterior arch and the odontoid precluded reduction by posterior manipulation. All cases then underwent posterior fusion and fixation procedures. Patients were neurologically and radiologically evaluated at regular followups to assess fusion and stability for a minimum period of 6 months.

Results:

Of the 63 cases who underwent posterior manipulation, 49 cases achieved optimum reduction and the remaining 14 cases showed near optimal reduction. Two cases expired in the postoperative period. None of the remaining cases showed neurological worsening after the procedure. Evaluation at 6 months after surgery revealed good stability and fusion in all except three cases.

Conclusion:

Atlantoaxial joint release and manipulation can be used to achieve reduction in most cases of atlantoaxial subluxation, obivating the need of transoral odontoid excision.     

Atlantoaxial subluxation in different intraoperative head positions in patients with rheumatoid arthritis

BACKGROUND: Disorders of the cervical spine are often observed in patients with rheumatoid arthritis (RA). However, the best head position for RA patients with atlantoaxial subluxation in the perioperative period is unknown. This study investigated head position during general anesthesia for the patients with RA and proven atlantoaxial subluxation. METHODS: During anesthesia of patients with RA and proven atlantoaxial subluxation, the authors used fluoroscopy to obtain a lateral view of the upper cervical spine in four different positions: the mask position, the intubation position, the flat pillow position, and the protrusion position. Copies of the still fluoroscopic images were used to determine the anterior atlantodental interval, the posterior atlantodental interval, and the angle of atlas and axis (C1-C2 angle). RESULTS: The anterior atlantodental interval was significantly smaller in the protrusion position (2.3 mm) than in the flat pillow position (5.1 mm) (P < 0.05). The posterior atlantodental interval was significantly greater in the protrusion position (18.9 mm) than in the flat pillow position (16.2 mm) (P < 0.05). The C1-C2 angle was, on average, 9.3 degrees greater in the protrusion position than in the flat pillow position (P < 0.05). CONCLUSION: This study showed that the protrusion position using a flat pillow and a donut-shaped pillow during general anesthesia reduced the anterior atlantodental interval and increased the posterior atlantodental interval in RA patients with atlantoaxial subluxation. This suggests that the protrusion position, which involves support of the upper cervical spine and extension at the craniocervical junction, might be advantageous for these patients.     

Endoscopic transcervical anterior release and posterior fixation in the treatment of irreducible vertical atlantoaxial dislocation

Vertical atlantoaxial dislocation is a type of atlantoaxial instability with upper cervical spinal cord compression. The transoral ondontoid resection with posterior fixation is the gold standard for ventral decompression. Results are satisfying though surgery can be challenging due to its invasiveness. The endoscopic transcervical anterior release could provide sufficient ventral decompression with less collateral damage. In the illustrative case, anatomic reduction was achieved with significant improvement in neurological function and radiographic parameters. Endoscopic transcervical anterior release and posterior fixation appears to be a viable and interesting alternative for the treatment of vertical atlantoaxial dislocation in properly selected individuals, and its implementation could significantly reduce the post-surgical complications.     

寰枢关节类风湿性关节炎的影像学分析(附21例报告)

目的评估累及寰枢关节的21例RA患者经联合治疗的临床效果及其影像学特征。方法对平均病程为7．95年（2～26年）的21例患者行MTX＋其他DMARDs的联合治疗,同时行临床和影像学评估,明确16例存在寰枢椎前向半脱位、3例垂直半脱位、2例侧方半脱位。6例有明显枕颈部症状的寰枢不稳息者行后路寰枢或枕颈融合治疗。结果联合治疗的有效率为85．7％。RA病程越长,越易发生寰枢椎不稳和椎管矢状径减小,本组前向寰枢椎半脱位最常见。6例手术患者的齿突周围血管翳在随访中较术前明显减小。结论对累及寰枢关节的RA患者,无论有无寰枢椎不稳、有无症状或脊髓损伤的体征,均可成功行影像学评估且行MTX＋其他DMARDs的联合治疗可取得较好的疗效;为防止枕颈部脊髓压迫,宜对此类患者行常规、定期的临床和影像学评估。     

Atlantoaxial Subluxation in Different Intraoperative Head Positions in Patients with Rheumatoid Arthritis

Background: Disorders of the cervical spine are often observed in patients with rheumatoid arthritis (RA). However, the best head position for RA patients with atlantoaxial subluxation in the perioperative period is unknown. This study investigated head position during general anesthesia for the patients with RA and proven atlantoaxial subluxation.

Methods: During anesthesia of patients with RA and proven atlantoaxial subluxation, the authors used fluoroscopy to obtain a lateral view of the upper cervical spine in four different positions: the mask position, the intubation position, the flat pillow position, and the protrusion position. Copies of the still fluoroscopic images were used to determine the anterior atlantodental interval, the posterior atlantodental interval, and the angle of atlas and axis (C1-C2 angle).

Results: The anterior atlantodental interval was significantly smaller in the protrusion position (2.3 mm) than in the flat pillow position (5.1 mm) (P < 0.05). The posterior atlantodental interval was significantly greater in the protrusion position (18.9 mm) than in the flat pillow position (16.2 mm) (P < 0.05). The C1-C2 angle was, on average, 9.3[degrees] greater in the protrusion position than in the flat pillow position (P < 0.05).     

Subaxial subluxation after atlantoaxial transarticular screw fixation in rheumatoid patients

The most common cervical abnormality associated with rheumatoid arthritis (RA) is atlantoaxial subluxation, and atlantoaxial transarticular screw fixation has proved to be one of the most reliable, stable fixation techniques for treating atlantoaxial subluxation. Following C1–C2 fixation, however, subaxial subluxation reportedly can bring about neurological deterioration and require secondary operative interventions. Rheumatoid patients appear to have a higher risk, but there has been no systematic comparison between rheumatoid and non-rheumatoid patients. Contributing radiological factors to the subluxation have also not been evaluated. The objective of this study was to evaluate subaxial subluxation after atlantoaxial transarticular screw fixation in patients with and without RA and to find contributing factors. Forty-three patients who submitted to atlantoaxial transarticular screw fixation without any concomitant operation were followed up for more than 1 year. Subaxial subluxation and related radiological factors were evaluated by functional X-ray measurements. Statistical analyses showed that aggravations of subluxation of 2.5 mm or greater were more likely to occur in RA patients than in non-RA patients over an average of 4.2 years of follow-up, and postoperative subluxation occurred in the anterior direction in the upper cervical spine. X-ray evaluations revealed that such patients had a significantly smaller postoperative C2–C7 angle, and that the postoperative AA angle correlated negatively with this. Furthermore, anterior subluxation aggravation was significantly correlated with the perioperative atlantoaxial and C2–C7 angle changes, and these two changes were strongly correlated to each other. In conclusion, after atlantoaxial transarticular screw fixation, rheumatoid patients have a greater risk of developing subaxial subluxations. The increase of the atlantoaxial angel at the operation can lead to a decrease in the C2–C7 angle, followed by anterior subluxation of the upper cervical spine and possibly neurological deterioration.     

Transoral anterior revision surgeries for basilar invagination with irreducible atlantoaxial dislocation after posterior decompression: a retrospective study of 30 cases

Purpose

To report the surgical techniques and clinical results of one-stage transoral anterior revision surgeries for basilar invagination (BI) with atlantoaxial dislocation (AAD) after posterior decompression.

Methods

From September 2008 to June 2012, 30 patients (16 men and 14 women) who had BI with irreducible atlantoaxial dislocation (IAAD) after posterior decompression underwent anterior revision surgeries in our department. Dynamic cervical radiographs, computed tomographic scans and magnetic resonance imaging were obtained pre- and postoperatively to assess the degree of AAD and ventral compression on the cervical cord. The JOA scoring system was used to evaluate the neurological status. The revision surgeries were conducted by anterior approach, using the transoral atlantoaxial reduction plate (TARP) system.

Results

The revision surgeries were successfully performed in all of the cases. The average follow-up duration was 16 months (range 6–39 months). For all of the cases, complete or more than 50 % reduction and decompression of C1–C2 were achieved. The cervicomedullary angle was improved by an average of 32.9°. Bone fusion was achieved within 3–6 months in all of the cases. Clinical symptoms were alleviated in 29 patients (96.7 %) and stabilised in 1 patient (3.3 %). No patients have developed recurrent or progressive atlantoaxial instability so far.

Conclusion

Anterior revision surgeries using the TARP system achieved reduction, decompression and fixation of C1–C2 in one stage for BI with IAAD. This technique offers an effective, simple and safe method for the revision of such cases after posterior decompression.     

Surgical procedures on the cervical spine in polyarthritis.

Summary Patients with rheumatoid arthritis suffer frequently from instabilities and deformities of the cervical spine which require surgical treatment. The most frequent indication for surgery represents the transverse atlantoaxial instability. As long the atlantoaxial instability remains reducible in extension a limited posterior exposure and screw fixation is adequate. Only situations with fixed dislocations and signs of myelopathy require anterior transoral decompression with simultaneous occipitocervical fusion. In the lower cervical spine, kyphotic deformities require anterior decompression and posterior stabilization in the case of electrophysiologically confirmed neurological deficits. A combined procedure with anterior vertebrectomy and decompression and posterior plate fixation is indicated since the poor bone quality rarely allows anterior stable fixation.      

Management of craniovertebral junction tuberculosis

BACKGROUND: Tuberculosis of the craniovertebral junction (CVJ) is extremely rare. However, recent evidence suggests that the incidence of this condition may be increasing. The diagnosis is often difficult despite advances in imaging using magnetic resonance imaging. The transoral approach to the anterior CVJ provides excellent access to this region, has low mortality and morbidity, and enables biopsy of lesions and decompression of the neuraxis. Management of associated atlantoaxial instability, with regard to timing and method of stabilization, is controversial. METHODS: We report 24 cases of CVJ tuberculosis. Prominent manifestations of the disease included neck pain and stiffness, swelling of the retropharyngeal soft tissues, quadriparesis, osteolytic erosions, and atlantoaxial subluxation. Seven patients had acute presentation. All patients received antituberculous drug treatment for 18 months. Four patients were managed conservatively, 5 underwent only transoral biopsy, 9 patients underwent transoral decompression and posterior fusion, and 6 patients underwent only posterior fusion. RESULTS: Histopathologic analysis of biopsy material revealed abscess only in 5 cases, granulation tissue only in 6, abscess with granulation tissue in 4, granulation tissue with chronic osteomyelitis in 5, and chronic inflammation in 2. All patients improved, with mean improvement in Nurick grading of 1.71. Even patients with spinal cord signal intensity changes on magnetic resonance images showed improvement. CONCLUSIONS: Although CVJ tuberculosis is a rare disease, the outcome of treatment is good. Antituberculous drug therapy remains the mainstay of treatment after confirming the diagnosis. The surgical management options include transoral decompression with or without posterior fusion, depending upon the presence and persistence of atlantoaxial instability.     

Chirurgische Aspekte der rheumatischen Halswirbelsäule

Approximately 20% percent of the patients with rheumatoid arthritis show pathology in the cervical spine, mainly in the atlantoaxial segment. The translational instability between axis and atlas might be painful and leads in the long term to myelopathic changes due to chronic traumatization of the myelon. Ongoing osseous resorption of the lateral masses of the atlas cause upward migration of the dens into the foramen magnum. In the subaxial cervical spine, the inflammatory process causes instability and deformity. Neck pain is the most common indication for surgery, but neurological symptoms with myelopathy or radicular deficits might be the primary cause for surgery. It has to be kept in mind that clinical assessment in rheumatoid patients might be extremely difficult since previous surgeries on various articulations of the extremities make interpretation of clinical findings difficult. Neurophysiological investigation is suitable to obtain objective results. Stabilization of the atlantoaxial segment is the most common procedure for treatment of atlantoaxial instability. It is performed by screw fixation technique from a posterior approach. In case of severe occipitocervical dislocation, the fixation has to be extended to the occiput. Persistent dislocation or compression by the dislocated dens has to be treated by transoral decompression. In the subaxial spine, instabilities may be treated by posterior plate fixation with lateral mass screws or pedicle screws. Concomitant narrowing of the spinal canal should be approached by anterior decompression with corpectomy and/or posterior laminectomy. The timing of surgery in rheumatoid patients is crucial to obtain satisfactory clinical results.     

颈后路手术治疗类风湿性寰枢椎不稳

目的：对类风湿性寰枢椎不稳患者颈后路植骨融合、内固定手术进行探讨。方法：对21例类风湿性寰枢椎不稳患者采用颈后路植骨融合、内固定手术，其中7例可复性寰枢椎半脱位行寰枢椎间植骨钛缆或Apofix固定术；14例难以复位者行枕颈间植骨cervifix固定术。结果：随访6～28个月(平均18个月)。21例均无并发症发生，X线显示均获骨性融合，19例患者神经功能获不同程度改善，2例虽无改善但无神经损害发展。结论：颈后路植骨融合、内固定术可为类风湿性寰枢椎不稳的患者提供牢固的融合固定，且以早期手术为佳。     

Surgical aspects of the cervical spine in rheumatoid arthritis

Approximately 20% percent of the patients with rheumatoid arthritis show pathology in the cervical spine. The translational instability between axis and atlas might be painful and leads in the long term to myelopathic changes due to chronic traumatization of the myelon. Ongoing osseous resorption of the lateral masses of the atlas cause upward migration of the dens into the foramen magnum. In the subaxial cervical spine, the inflammatory process causes instability and deformity. Neck pain is the most common indication for surgery, but neurological symptoms with myelopathy or radicular deficits might be the primary cause for surgery. Neurophysiological investigation is suitable to obtain objective results. Stabilization of the atlantoaxial segment is the most common procedure for treatment of atlantoaxial instability. It is performed by screw fixation technique from a posterior approach. In case of severe occipitocervical dislocation, the fixation has to be extended to the occiput. Persistent dislocation or compression by the dislocated dens has to be treated by transoral decompression. In the subaxial spine, instabilities may be treated by posterior plate fixation with lateral mass screws or pedicle screws. Concomitant nar-rowing of the spinal canal should be approached by anterior decompression with corpectomy and/or posterior laminectomy. The timing of surgery in rheumatoid patients is crucial to obtain satisfactory clinical results.     

经口咽前路寰枢椎复位钢板内固定的外科解剖学研究

目的为经口咽前路寰枢椎复位钢板内固定设计和应用提供解剖学依据。方法对10例新鲜的头颈部标本使用经口咽前入路进行逐层的显微外科解剖,观察咽后壁的层次、椎动脉的走行、寰枢椎的解剖毗邻关系和寰枢椎前路钢板内固定的相关解剖参数等。结果(1)咽后壁分两层和两个间隙粘膜层、椎前筋膜层,咽后间隙和椎前间隙;(2)经此入路可显露从枕骨大孔前缘至C3椎体的范围;(3)寰椎和枢椎椎动脉距中线的距离分别为寰椎(252±23)mm和枢椎(184±26)mm;(4)寰椎和枢椎可显露宽度分别为(394±22)mm和(390±21)mm,寰椎进钉点(侧块中点)间距(a)为(314±33)mm,寰椎进钉点连线与枢椎进钉点(枢椎前表面中部上关节面内缘连线与前唇下缘线之间的等距离线位于矢状中线两侧旁开3～4mm的位置)连线的垂直间距(b)为(187±27)mm,a/b比值为15～17。结论经口咽前入路行寰枢椎前路钢板内固定可行,钢板的设计应以上述测量数据为依据。     

一期前路松解后路椎弓根钉固定融合治疗难复性寰枢椎脱位

目的 探讨经口咽入路前路松解一期后路寰枢椎椎弓根钉内固定植骨融合治疗难复性寰枢椎前脱位的临床疗效,方法 2005年1月～2010年2月,采用经口咽入路前路松解,一期后路寰枢椎椎弓根钉内固定植骨融合治疗难复性寰枢椎脱位合并高位颈脊髓压迫共21例.男15例,女6例;年龄26～70岁,平均51岁;病程6～30年.陈旧性齿状突...     

Rheumatoid arthritis of the cervical spine. Current concepts for diagnosis and therapy

The involvement of the cervical spine in patients with rheumatoid arthritis (RA) is common,and has recently received growing attention. In the early stage of the disease, there is an isolated atlantoaxial subluxation (AAS). With further progression, osseous destruction of the joints can lead to vertical instability. While the involvement of the middle and lower cervical spine can cause a subaxial instability, neurological deficits can occur at any time. The onset of cervical myelopathy in patients with RA is often missed because of additional problems related to the hands and feet. If patients show clear symptoms of cervical myelopathy, the progression of the disease cannot be stopped by conservative treatment. Other indications for operative treatment are severe pain and radiological evidence of progressive instability. In the case of an isolated AAS, fusion can be restricted to the C1/C2 segment. If there is evidence for vertical or subaxial instability, an occipitocervical fusion has to be performed. To avoid instability adjacent to the fusion, the surgeon must check for signs of potential subaxial instability. If this is the case, fusion should include the entire cervical spine. Additional transoral decompression may be necessary when there is persistent retrodental pannus or osseous compression by an irreducible transverse dislocation or cranial migration of the dens. Non-ambulatory myelopathic patients are more likely to present severe surgical complications with limited prospects of functional recovery. Therefore, it is important to avoid the development of severe cervical myelopathy by early surgical intervention.     

Transoral approach using the mandibular osteotomy for atlantoaxial vertical subluxation in juvenile rheumatoid arthritis associated with mandibular micrognathia

We report a case of atlantoaxial vertical subluxation with mandibular micrognathia associated with juvenile rheumatoid arthritis. The patient was treated by odontoidectomy via the transoral approach and required a sagittal split mandibular osteotomy because of the mandibular micrognathia. The clinical outcome was excellent.     

Chiari I malformation associated with atlanto-axial dislocation: focussing on the anterior cervico-medullary compression

Summary Background. Chiari I malformation with atlantoaxial dislocation may cause both posterior and anterior cervicomedullary compression. We studied the clinicoradiological features and surgical outcome in patients having Chiari I malformation with atlantoaxial dislocation. Method. Thirty-nine patients with Chiari I malformation with atlanto-axial dislocation underwent preoperative and follow-up neurological status assessment. In Chiari I malformation with reducible atlanto-axial dislocation (n = 11), a direct posterior stabilization was done. In Chiari I malformation with irreducible atlanto-axial dislocation (n = 28), a single stage transoral decompression with posterior stabilization and/or posterior decompression and duraplasty were done in 18 patients. In 10 patients, only posterior decompression and/or posterior stabilization was performed. Seven among the latter patients subsequently deteriorated and required transoral decompression. Comparison of mean neurological status scores of patients with Chiari I malformation with irreducible atlanto-axial dislocation who underwent single stage transoral decompression with posterior stabilization versus the posterior procedure alone was done using T-test and proportional significance also calculated. Findings. Patients with Chiari I malformation with atlanto-axial dislocation have a high incidence of long tract signs and sphincteric disturbances with a decrease in the mean foramen magnum diameter. The mean neurological status scores of patients with Chiari I malformation with irreducible atlanto-axial dislocation who underwent single stage transoral decompression with posterior stabilization were significantly better than those patients who underwent the posterior procedure alone. The latter patients also showed significant clinical improvement following transoral decompression. In the presence of Chiari I malformation with reducible atlanto-axial dislocation, reduction and stabilization of atlanto-axial dislocation resulted in neurological improvement. The follow up neurological status scores of these patients improved after surgical intervention even in the presence of poor preoperative grades. Conclusions. Patients with Chiari I malformation should be investigated for the presence of atlanto-axial dislocation. In case atlantoaxial dislocation coexists, priority must be given to relieving anterior cervicomedullary compression.     

Transoral decompression, anterior plate fixation, and posterior wire fusion for irreducible atlantoaxial kyphosis in rheumatoid arthritis

STUDY DESIGN: Fifteen consecutive patients with irreducible atlantoaxial kyphosis caused by rheumatoid arthritis were treated by combined transoral odontoid resection, anterior plate fixation, and posterior wire fusion. OBJECTIVES: To investigate the clinical results of this new surgical procedure. SUMMARY AND BACKGROUND DATA: Irreducible atlantoaxial kyphosis in rheumatoid arthritis results from a destruction of the craniocervical joint ligaments and the anterior aspects of the lateral atlantoaxial joints. The development of a paradental synovial pannus and atlantoaxial joint impaction prevents reduction by conservative treatment, such as skull traction. Posterior surgical procedures for the treatment of the irreducible atlantoaxial kyphosis with spinal cord compression have been associated with high morbidity and mortality. METHODS: Fifteen consecutive patients were treated by transoral odontoid resection. The fixation was performed with anterior plating, according to the method of Harms in combination with posterior wire fusion according to Brooks. Before and after surgery, evaluation was performed using the parameters of pain (visual analog scale), range of motion, and subjective assessment of improvement and the Health Assessment Questionnaire. The neurologic deficit was defined according to the classifications proposed by Ranawat, Frankel, and Nurwick. Plain radiographs, including lateral flexion and extension views, and magnetic resonance scans were obtained. RESULTS: No perioperative fatality occurred. The average clinical and radiographic follow-up was 50.7 +/- 15.6 months (range, 26-77). Postoperative pain was relieved (mean pain score before surgery, 7.9 +/- 1.87; after surgery, 3.8 +/- 1.27), and the range of motion of all patients increased (mean 21.5 +/- 14.0 degrees for rotation; mean 17.2 +/- 5. 54 degrees for bending). The score on the Health Assessment Questionnaire increased in three patients, remained unchanged in three and decreased in six patients (three had died). All patients improved at least one Ranawat level after surgery, except a patient in Ranawat Class II, whose condition remained unchanged. All patients were satisfied with the procedure and reported subjective improvement. CONCLUSION: Transoral plate fixation combined with posterior wire fixation after transoral odontoid resectionis an effective, reliable, and safe procedure for the treatment of irreducible atlantoaxial kyphosis in rheumatoid arthritis.     

经口咽齿突切除结合H—V环复位治疗重度陈旧性寰枢椎脱位

目的：探讨经口咽齿突切除结合H－V环复位治疗重度陈旧性寰枢椎脱位的方法及重度寰枢椎脱位的病理机制。方法：对2例重度陈旧性寰枢椎脱位患者采用经口咽齿突切除前方松解、减压,结合H－V环缓慢复位,二期行后路减压枕颈融合方法治疗。结果：1例术前Frankel C级恢复至正常,1例术前Frankel C级恢复至D级。结论：重度陈旧性寰枢椎脱位,在寰椎前弓与枢椎体间形成纤维组织增生,这种纤维连接使寰枢椎相对趋向稳定是障碍复位的主要因素。结合H－V环缓慢牵引,复位制动,经口咽入路行齿突切除前方松解减压,二期行后路减压枕颈融合,确能从前后方解除致压因素,结合H－V环制动、复位能够保障复位和手术过程中头颈部的运动在H－V环控制下,对手术和复位提供了极大的安全保证。     

Rheumatoid vertical and subaxial subluxation can be prevented by atlantoaxial posterior screw fixation

Purpose

Literature has described a risk for subsequent vertical subluxation (VS) and subaxial subluxation (SAS) following atlantoaxial subluxation in rheumatoid patients; however, the interaction of each subluxation and the radiographic findings for atlantoaxial fixation has not been described. The purpose of this study was to evaluate the effects of two different posterior atlantoaxial screw fixation on the development of subluxation in patients with rheumatoid atlantoaxial subluxation.

Methods

Between 1996 and 2006, rheumatoid patients treated with transarticular fixation and posterior wiring (TA) or C1 lateral mass–C2 pedicle screw fixations (SR) in the Nagoya Spine Group hospitals, a multicenter cooperative study group, were included in this study. VS, SAS, craniocervical sagittal alignment, and range of motion (ROM) at the atlantoaxial adjacent segments were investigated to determine whether posterior atlantoaxial screw fixation is a prophylactic or a risk factor for the development of VS and SAS.

Results

The mean follow-up was 7.2 years (4–12). No statistically significant difference was observed among the patients treated with either of the procedure during the follow-up period. Of 34 patients who underwent posterior atlantoaxial screw fixation, SAS was observed in 26.5 % during the follow-up period; however, VS was not observed. Postoperative C2–7 angle, and Oc–C1 and C2–3 ROM were significantly different between patients with and without postoperative SAS. The incidence of SAS was 38.9 % for TA and 12.5 % for SR; statistically significant differences were observed in the postoperative C1–2 and C2–7 angles, and C2–3 ROM.

Conclusions

Atlantoaxial posterior screw fixation may be an appropriate prophylactic intervention for VS and SAS if the atlantoaxial joint develops bony fusion following physiological alignment. Compared to TA, SR provided optimal atlantoaxial angle and prevented lower adjacent segment degeneration, thereby reducing SAS.