Abstract
Objective
Cable‐dragged reduction and cantilever beam internal fixation can provide promising results in the treatment of atlantoaxial dislocation or instability. However, bilateral atlantoaxial joints bone autografting has not been conducted in this technique. We aim to evaluate the safety and effectiveness of bilateral atlantoaxial joints bone autografting in posterior cable‐dragged reduction and cantilever‐beam internal fixation.
Methods
In this retrospective study, we included 14 patients with a minimum 24‐month follow‐up from December 2019 to September 2020. The granular bone harvested from the iliac crest was packed into the bilateral atlantoaxial joints of 14 patients in posterior cable‐dragged reduction and cantilever‐beam internal fixation. X‐ray imaging and cervical computed tomography (CT) were performed during follow‐up. The time required for bone fusion was recorded. The clinical outcomes were evaluated using the JOA scores, NDI, and VAS scores. Mann–Whitney U test, the chi‐squared test, or the Fisher exact test were used to compare the two groups regarding patient characteristics, clinical outcomes, bone fusion rates, and cervical sagittal alignment.
Results
The operations were successfully performed in all patients without any intraoperative complications. The mean operation time was (169.64 ± 20.91) minutes, and the intraoperative blood loss was (130.71 ± 33.62) mL. All patients received satisfactory reductions and firm bony fusion at the final follow‐up. The fusion rates were 64.29% in the atlantoaxial joints and 21.43% in post bone graft area at 3 months postoperatively, and a significant difference was observed (p = 0.022). Besides, the cervical sagittal alignment in all patients was well maintained in the last follow‐up compared to preoperatively. Importantly, a complete bony fusion in the atlantoaxial joints was observed in all patients. Moreover, the JOA, NDI, and VAS scores had improved significantly at the last follow‐up.
Conclusion
Bone autografting of the bilateral atlantoaxial joints is a safe and effective technique to increase bone fusion rates, shorten bone fusion time, and reduce complication rates when the cable‐dragged reduction and cantilever beam internal fixation approach is used. Therefore, it is a cost‐effective surgical procedure for treating patients with atlantoaxial dislocation or instability.
Keywords: Atlantoaxial Fusion, Atlantoaxial Joints, Bone Graft, Cable, Cantilever Beam
The management of atlantoaxial instability and dislocation has always been challenging. And bone graft fusion is key to achieving long‐term maintenance of stability. This study reported a modified bone autografting technique with adequate longitudinal compression using the cantilever beam internal fixation approach. This technique may lessen the potential risk of vertebral artery injury while still providing promising results.
Introduction
Atlantoaxial dislocation or instability is usually secondary to congenital deformities, trauma, inflammatory disease, or neoplastic factors. 1 , 2 , 3 Given the particular anatomical location, such dysfunction could threaten the brain stem and upper spinal cord. Therefore, decompressing the neurological structures, realignment of the cervical spine, and stabilizing the unstable atlantoaxial complex are necessary for patients suffering from atlantoaxial dislocation or instability. 4 , 5 , 6
Posterior surgical procedures have been considered effective treatment strategies for atlantoaxial dislocation or instability, and the fusion rates ranged from 89%–100%. 7 , 8 , 9 The bone graft is usually placed across C1–C2 for fusion in these procedures. Of note, the long‐term stability of the atlantoaxial complex relies on the occurrence of firm bone fusion even in the context of solid screw‐rod fixation. 2 , 10 , 11 However, some patients still experience long‐term postoperative non‐unions 1 , 9 which may be secondary to long bony bridge distance 1 or the small size of the bone graft bed. 12 In addition, when the posterior arch of the atlas requires intraoperative removal for decompression, the fusion becomes more complex. 13 Therefore, bone autografting in the bilateral atlantoaxial joints provides a possible superior alternative to achieve a fusion after undergoing posterior stabilization to treat atlantoaxial dislocation or instability. 1 , 14
Liu et al. 4 introduced an alternative technique called cable‐dragged reduction and cantilever beam internal fixation to achieve intraoperative reduction from a posterior approach to manage atlantoaxial instability or dislocation that is secondary to anterior displacement of the atlas. This technique may lessen the potential risk of vertebral artery injury while still providing promising results. 4 , 15 , 16 Therefore, the aims of our study were: (i) to evaluate the feasibility and effectiveness of placing autograft bone in the atlantoaxial joints bilaterally for fusion after undergoing cable‐dragged reduction and cantilever beam internal fixation, and assess the advantages of autologous bone grafting in surgery; (ii) to follow up the clinical and radiological outcomes in patients with the modified bone autografting technique; and (iii) to introduce the surgery tips for bone autografting of the atlantoaxial joints.
Patients and Methods
Patients
This retrospective study was approved by the Ethics Committee of the West China hospital (No. 2021–925), and informed consent for participation was obtained from all patients. Patients who were diagnosed with atlantoaxial dislocation or instability in our institute from December 2019 to September 2020 were included (Figure 1). The inclusion criteria were (1) patients who were diagnosed with atlantoaxial dislocation or instability; (2) failure to be reduced by traction; (3) with detailed postoperative radiological and clinical data; (4) followed for at least 24 months. The medical records of these patients were collected and evaluated in this study. The exclusion criteria were (1) atlantoaxial dislocation that cannot be reduced by posterior approach alone; (2) tumor, tuberculosis, or rheumatoid arthritis; (3) severe occipitocervical malformation or skull base depression; (4) atlas posterior arch fracture or fineness; (5) poor general condition, unable to tolerate anesthesia and surgery.
FIGURE 1.
Serial radiological examinations of a 50‐year‐old male patient with numbness in the fingertips of both hands accompanied by walking instability for almost 1 year. Plain radiographs in the neutral (A), flexion (B), and extension (C) showing atlantoaxial instability. Preoperative computed tomography reconstruction images (F, G) showing atlantoaxial dislocation with dens nonunion. Preoperative magnetic resonance image (H) showing a protruding dens and severe compression of the medulla oblongata. The signal of the medulla oblongata is starting to change. The postoperative immediate plain radiograph (D) demonstrated relatively satisfactory cervical sagittal alignment restoration and CT reconstruction images (I) showed bone graft on the atlantoaxial joints (I, white arrow) and the posterior area (I, red arrow). At the last follow‐up, the cervical sagittal alignment was well maintained (E) and bone fusion in the atlantoaxial joint (J, white arrow) and posterior area (J, red arrow) was observed. PO‐IM: postoperative immediately; Last FU: last follow‐up.
Surgical Technique
All interventions were performed by the same spine surgeon at our center under neuromonitoring. After the induction of general anesthesia, the patient was placed in the prone position, and a Mayfield headstock was used to maintain the head and cervical spine in a neutral position. Epinephrine was diluted to a concentration of 1:500,000 and was injected subcutaneously before incision. A conventional posterior midline skin incision was made to achieve exposure of the posterior arch of C1 and posterior appendicular structures of the C2 and C3 vertebrae. All procedures were done within a distance of 1.5 cm from the midline bilaterally to avoid possible injury to the vertebral artery or vein.
The Procedure of Reduction
Next, using the Magerl method, 17 two multidirectional lateral mass screws were inserted into C2, and another two multidirectional lateral mass screws were inserted into C3 bilaterally. Then a rod was bent into a U‐shaped structure. To provide adequate reduction space, the head of the rod was slanted slightly backward according to the size of the atlantoaxial complex and the degree of dislocation.
The U‐shaped rod was then fixed to the four screws to form a cantilever beam. And the head of the cable was fastened to the U‐shaped cantilever beam to link it to the posterior arch of C1 and was tightened with a cable tensioner (Medtronic Co., Minneapolis, MN). The atlas was pulled by the U‐shaped rod, causing the atlas and odontoid process to move backward.
Bone Autografting Procedure of the Bilateral Atlantoaxial Joints
A nerve dissector was meticulously used to perform subperiosteal dissection across the interior surface of the posterior arch of C1. Then the cable head was molded into a hook and stretched across the interior surface of the posterior arch carefully on each side. The lateral masses of the atlantoaxial joints were bilaterally exposed by retracting the paravertebral muscles using a sharp subperiosteal dissection, then the joint capsule was excised, and the articular cartilage was scraped by a curette. The cancellous bone particles harvested from the posterior superior iliac crest were trimmed into granular bones and then punched into the bilateral atlantoaxial joints space (Figures 2 and 3).
FIGURE 2.
Intraoperative photograph showing bone autografting in the right atlantoaxial lateral mass joint. Two nerve dissectors mark the internal and external boundaries of the right lateral mass to protect the dural sac and vertebral artery. The articular cartilage was scraped using a curette, and the medial dural sac was marked by the triangle. The yellow arrow marked the posterior margin space, while the asterisk marked the axial spinous process.
FIGURE 3.
The postoperative plain radiograph of a 50‐year‐old patient (A) shows the cantilever beam composed of two pairs of lateral mass screws inserted into C2 and C3 and the “U”‐shaped rod. When the cable wired across the posterior arch of C1 is retracted with a cable tensioner, it drags the posterior arch of C1 backwards and the dislocation is thereby reduced. Once successful reduction is achieved, the posterior arch is fixed to the cantilever beam with the cable. The coronal (B, D) and sagittal (C) plain reconstructive images of computed tomographic scan show the bone autografting in the atlantoaxial joints (white arrow) and posterior area.
The Procedure of Fixation
Once the intraoperative C‐arm fluoroscopy showed a satisfactory reduction, the redundant part of the cable was removed, the remaining end of the cable was bent into a snap‐lock to avoid unnecessary injury, and the nuts were then wrenched tight to fasten the cantilever beam (Figure 3).
Following the above interventions, the wound was repeatedly irrigated with normal saline. The posterior arch of C1 and C2 vertebral lamina decortication were performed using nucleus pulposus forceps and a bone knife. A gelatin sponge was placed behind the atlantoaxial space to avoid the collapse of the bone graft into the spinal canal. The granular bone was implanted into the space between the posterior arch of the atlas and the lamina of C2, the lamina of C2‐3 vertebrae, and the posterolateral facet of the articular process. The incision was closed, and a drainage tube was left inside after meticulous hemostasis.
Postoperative Management and Follow‐Up
The drainage tube was usually removed within 24 to 48 hours postoperatively depending on the amount of drainage fluid. Moreover, a custom‐built orthosis was applied for 6 to 8 weeks for additional fixation and protection when patients became ambulatory. Data collected during the patient's stay in the hospital included the patient's age, sex, diagnosis, neck disability index (NDI), Japanese Orthopaedic Association (JOA) scales and visual analog scale (VAS) scores, the amount of intraoperative blood loss and operation time.
During the follow‐up, plain radiograph and computed tomographic (CT) reconstructive images were obtained at 3, 6, and 12 months after surgery and at the last follow‐up. The clinical outcomes based on the NDI, JOA, and VAS scores were evaluated at the last follow‐up visit. The results of reduction and fusion were assessed according to both plain radiograph and CT three‐dimensional reconstructive images (Figures 3 and 4). Bone fusion was defined as obvious bridging of bone across the bone graft interface. 18 The cervical sagittal alignment was evaluated by OC2 angle (OC2A: C0–C2 Cobb angle measured between McGregor's line and the line passing through the lower end plate of C2), cervical lordosis (CL: angle measured between lower endplates of C2 and C7), T1 slope (T1s: the angle between the superior end plate of T1 and a horizontal line.) and C2–C7 sagittal vertical axis (SVA: the distance between the plumb line from the center of C2 and the superior posterior corner of C7). (Figure 5).
FIGURE 4.
Computed tomography (CT) reconstruction image series of a 61‐year‐old female patient. Preoperative images (A, G) showing atlantoaxial dislocation with dens nonunion. Postoperative occipitocervical alignment was satisfactorily and promptly restored (B, H). Bone graft was visible on the atlantoaxial joints (B, white arrow) and the posterior area (H, red arrow). During the follow‐up intervals, the bone fusion of the atlantoaxial joints was observed in the early stage (C–F, white arrow). Although bone fusion of the posterior area was achieved in the last follow‐up, there was also significant bone resorption (H–L, red arrow). Pre‐op: Preoperatively; PO‐IM: postoperative immediately; Last FU: last follow‐up.
FIGURE 5.
Cervical sagittal alignment measurement. The OC2 angle was measured between McGregor's line and the line passing through the lower end plate of C2. The CL was formed by the line between the lower endplates of C2 and C7. T1 slope was measured between the superior end plate of T1 and a horizontal line. C2–C7 sagittal vertical axis was measured as the distance between the plumb line from the center of C2 and the superior posterior corner of C7.
Statistical Analysis
Standard statistical analysis was conducted using SPSS software version 25.0 (SPSS Inc., Chicago, IL). Continuous variables were summarized by mean ± standard deviation (SD), while categorical variables were summarized by count and percentage. The Mann–Whitney U test was used to compare continuous variables, and the chi‐squared test or the Fisher exact test was used to compare bone fusion rates at each follow‐up time point. A value of p < 0.05 indicated that there were significant differences.
Results
Patient Characteristics
Between December 2019 and September 2020, 14 patients underwent posterior cable‐dragged reduction and cantilever‐beam internal fixation with bone autografting of the bilateral atlantoaxial joints at our hospital. There were six male and eight female patients with a mean age of 49.07 (range, 12–78) years. The mean duration of follow‐up was 26.29 months (range, 24–41 months). The baseline data of the patients are presented in Table 1.
TABLE 1.
Baseline data for all patients.
| Case no. | Sex | Age (years) | BMI (kg/m2) | Diagnosis |
|---|---|---|---|---|
| 1 | F | 55 | 20.81 | Dens nonunion, Atlantoaxial instability |
| 2 | F | 56 | 22.48 | Atlantoaxial dislocation |
| 3 | M | 50 | 19.14 | Dens nonunion, Atlantoaxial dislocation |
| 4 | M | 25 | 22.15 | Atlantoaxial dislocation |
| 5 | F | 61 | 19.47 | Dens nonunion, Atlantoaxial dislocation |
| 6 | F | 12 | 19.20 | Atlantoaxial dislocation |
| 7 | F | 45 | 23.59 | Dens nonunion, Atlantoaxial dislocation |
| 8 | F | 69 | 23.37 | Atlantoaxial dislocation |
| 9 | M | 63 | 19.45 | Dens nonunion, Atlantoaxial dislocation |
| 10 | F | 30 | 22.22 | Atlantoaxial dislocation |
| 11 | M | 70 | 24.04 | Atlantoaxial dislocation |
| 12 | F | 60 | 16.53 | Atlantoaxial dislocation |
| 13 | M | 13 | 25.71 | Dens nonunion, Atlantoaxial dislocation |
| 14 | M | 78 | 25.26 | Atlantoaxial dislocation |
| Summary | M:6 (42.86%), F:8 (57.14%) | 49.07 ± 21.21 | 21.67 ± 2.66 |
Abbreviations: BMI, body mass index; F, female; M, male.
Clinical Data and Functional Outcomes
The surgeries were completed successfully in all patients without intraoperative complications, such as vertebral artery or spinal cord injury. The mean operative time and blood loss volume were 169.64 (range, 135–220) minutes and 130.71 (range, 80–200) mL, respectively. All patients were reviewed postoperatively at 3, 6, 12 months and last follow‐up. No surgical site infection, wound dehiscence, and hematoma occurrence happened in the donor site of iliac crest harvesting. However, some patients complained about pain and dysesthesias of the donor site in the early stage postoperatively, and it gradually improved during the follow‐up. Only one patient had chronic pain of the donor site at the last follow‐up. At the last follow‐up, all patients achieved symptomatic relief, and the clinical outcomes, including the JOA, NDI, and VAS scores were markedly improved compared to preoperatively. The clinical data and functional outcomes are presented in Table 2.
TABLE 2.
Clinical data for all patients.
| Case no. | Operative time (min) | Blood loss (mL) | NDI | JOA | VAS | |||
|---|---|---|---|---|---|---|---|---|
| Pre‐op | Last follow‐up | Pre‐op | Last follow‐up | Pre‐op | Last follow‐up | |||
| 1 | 220 | 150 | 30 | 10 | 14 | 15 | 6 | 2 |
| 2 | 180 | 150 | 26 | 12 | 12 | 15 | 6 | 2 |
| 3 | 135 | 100 | 10 | 6 | 10 | 14 | 5 | 1 |
| 4 | 170 | 150 | 27 | 11 | 12 | 14 | 5 | 1 |
| 5 | 185 | 100 | 31 | 15 | 9 | 13 | 6 | 1 |
| 6 | 184 | 150 | 16 | 10 | 13 | 17 | 4 | 0 |
| 7 | 159 | 150 | 30 | 13 | 9 | 14 | 7 | 2 |
| 8 | 169 | 200 | 28 | 12 | 11 | 15 | 5 | 1 |
| 9 | 180 | 150 | 28 | 11 | 11 | 14 | 4 | 1 |
| 10 | 175 | 100 | 30 | 14 | 12 | 16 | 8 | 3 |
| 11 | 145 | 80 | 32 | 15 | 8 | 13 | 6 | 2 |
| 12 | 165 | 100 | 25 | 13 | 13 | 15 | 6 | 1 |
| 13 | 150 | 150 | 24 | 14 | 12 | 14 | 6 | 2 |
| 14 | 158 | 100 | 24 | 12 | 12 | 14 | 5 | 1 |
| Summary | 169.64 ± 20.91 | 130.71 ± 33.62 | 25.79 ± 6.09 | 12.00 ± 2.39 | 11.29 ± 1.73 | 14.50 ± 1.09 | 5.64 ± 1.08 | 1.43 ± 0.76 |
Abbreviation: Pre‐op, preoperatively.
Bone Fusion Rates and Cervical Sagittal Alignment
Satisfactory bone fusion in the bilateral atlantoaxial joints was observed in nine patients in the first 3 months, and a significant difference was observed at this time point when comparing the fusion rate of the atlantoaxial joints to the fusion mass seen at the site of the posterior on‐lay bone graft (p = 0.022). At the last follow‐up, all patients achieved satisfactory bone fusion within the atlantoaxial joints, while not all patients obtained a solid fusion at the site of the posterior on‐lay bone graft (Figure 4, Table 3). Cervical sagittal alignment results of each patient are summarized in Table 4. In terms of the four parameters, OC2A, CL, T1S, and SVA, the preoperative and the last follow‐up measurements were almost consistent, and no significant differences were observed (p > 0.05).
TABLE 3.
Comparison of bone fusion rates between atlantoaxial joint and posterior area.
| Atlantoaxial joints | Posterior area | χ2 | p value | |
|---|---|---|---|---|
| 3 months | 9/14 (64.29%) | 3/14 (21.43%) | 5.250 | 0.022 |
| 6 months | 12/14 (85.71%) | 10/14 (71.43%) | 0.848 | 0.648 |
| 12 months | 14/14 (100%) | 12/14 (85.71%) | 2.154 | 0.481 |
| Last follow‐up | 14/14 (100%) | 13/14 (92.86%) | 1.037 | 1.000 |
TABLE 4.
Cervical sagittal alignment.
| OC2 (°) | CL (°) | T1 S (°) | SVA (cm) | |
|---|---|---|---|---|
| Pre‐op | 13.23 ± 15.86 | 15.28 ± 14.42 | 25.05 ± 11.25 | 1.18 ± 1.59 |
| Last follow‐up | 10.94 ± 10.90 | 18.19 ± 11.77 | 26.32 ± 8.05 | 1.24 ± 0.81 |
| Z value | 0.735 | 0.919 | 0.505 | 0.575 |
| p value | 0.482 | 0.376 | 0.635 | 0.571 |
Abbreviation: Pre‐op, preoperatively.
Discussion
The management of atlantoaxial instability and dislocation has always been challenging. And internal fixation is conducive to restoring the stability of the upper cervical region immediately after operation. However, bone graft fusion is key to achieving long‐term maintenance of stability. 1 , 2 Regarding fusion, although several studies have shown that the rate of bone graft fusion with internal fixation was higher, 1 , 2 , 5 some patients still experience unsatisfactory bone graft healing and postoperative complications resulting from postoperative nonunion of bone grafts. 19 It has been reported that the rates of instrumentation failure after nonunion were about 6.7% during atlantoaxial fusion. 9 To maintain solid fixation in these patients, prolonged external immobilization and even revision surgeries are often needed. In the present study, we firstly showed the safety and effectiveness of bilateral atlantoaxial joints bone autografting in posterior cable‐dragged reduction and cantilever‐beam internal fixation. All patients received firm bony fusion with no loosening or rupture of the fixation at the final follow‐up. Besides, clinical and radiological outcomes were satisfactory in all patients. Thus, it is a cost‐effective surgical procedure for treating patients with atlantoaxial dislocation or instability.
The Outcomes of Placing Autograft Bone in the Atlantoaxial Joints
In previous surgical interventions, bone grafting was performed between the posterior arch of C1 and the C2 spinous process and lamina, 4 , 20 , 21 with the bony bridge distance making it difficult for firm bone fusion in the early postoperative stage. 1 Additionally, the bone graft bed provided by the occipital squama, posterior arch of atlas and lamina of axis for bony fusion was not large enough. 12 This has been linked with complications and delayed the process of postoperative rehabilitation. 22
Herein, we introduced a modified bone autografting technique with adequate longitudinal compression using the cantilever beam internal fixation approach. In addition to the posterior bone graft, we also performed bone autografting of the bilateral atlantoaxial joints. The atlantoaxial joints are located between the vertebral artery and the cervical spinal dura. 12 , 13 Previous studies have demonstrated that the surface area and blood supply of the atlantoaxial joint are large enough to easily provide a safe and sufficient zone to place autograft bone in order to obtain a solid posterior fusion in the treatment of atlantoaxial dislocation or instability. 13 , 23 , 24 Besides, we carefully placed the cancellous bone particles harvested from the posterior superior iliac crest into the joints during the surgery. During postoperative follow‐up, we observed that most patients in our study received satisfactory bone fusion in bilateral atlantoaxial joints in the early stage, while the fusion rates in the posterior area were poorer in contrast.
Anatomical Advantages of Bone Autografting of the Atlantoaxial Joints
The atlantoaxial joint carries most of the head weight, similar to spinal intervertebral discs. 25 The mechanical force could generate stress on the bilateral atlantoaxial joints and posterior bone graft when patients were kept in a sitting or upright position. The longitudinal pressure load between atlantoaxial vertebrae is mainly transmitted down through the atlantoaxial lateral mass, 13 , 26 and the bone graft is prone to fuse and reconstruct with specific stress stimulation according to Wolff's law. 27 Zhou et al. 2 compared the techniques of placing a cancellous morselized bone graft on decorticated surfaces of the atlantoaxial complex and securing a structural iliac bone graft between C1 and C2 and demonstrated that both techniques were effective for posterior C1‐C2 screw rod fixation and fusion. Yang et al. 1 placed granular bone into the bilateral atlantoaxial joints during posterior occipitocervical fusion surgery and revealed that the atlantoaxial joint fusion was more likely to be achieved compared to posterior occipitocervical fusion, which is in agreement with our findings. Moreover, a longer distance is required for osteogenesis between the posterior arch of the atlas and the lamina of the C2 vertebrae, making it difficult to form firm bone fusion in the early postoperative period.
Surgery Tips for Bone Autografting of the Atlantoaxial Joints
Sufficient preparation of the bone‐graft bed, stable internal fixation, and strong external fixation are necessary to promote bone fusion. 28 The removal of cartilage and roughing up of the atlantoaxial joints bilaterally provide an ideal environment for postoperative fusion. Besides, the contact area of the bone‐graft bed in the atlantoaxial joints is large enough for the placement of bone autograft, which make it more conducive to the fusion of the autograft. 5 , 29 , 30 Additionally, the bone autograft acts as a stimulus for living bone growth and maintains structural strength immediately. So, careful preparation of the surfaces of the atlas and cervical vertebrae should be performed to promote the fusion process. Moreover, it has been proven that autologous bone has better histocompatibility and osteogenic properties, indicating that autologous bone graft is safer and more effective in cervical fusion surgery. 1 More importantly, the cancellous bone could attach to the decorticated bone graft site easier than to the cortical bone, and the porous characteristics of cancellous bone could facilitate more satisfactory revascularization and complete incorporation. 31 Therefore, considering the reasons above, it is not unexpected to find that the fusion procedure can be performed between atlantoaxial lateral masses, and that a more reasonable fusion could occur on the bilateral atlantoaxial joints.
Additionally, bone autografting at the bilateral atlantoaxial joints broadens surgical indications by avoiding the restrictions caused by an atlantoaxial posterior arch abnormality. In conventional techniques, an intact posterior arch of the atlas is usually necessary to secure a bone graft across C1–C2 for fusion. 4 , 20 , 32 However, the atlantoaxial posterior arch is absent in certain patients, 13 making it challenging to place bone grafts in this area and limiting the application of the posterior fusion approach. Thus, this bone autografting technique provides a means for patients who are not suitable for conventional bone graft techniques. However, whether bone grafting in the atlantoaxial joint alone is sufficient for bone fusion in treating these cases warrants further in‐depth study. Besides, the postoperative cervical sagittal alignment maintenance plays an important role in patients' health‐related quality of life. 33 In our study, the sagittal alignment parameters regarding OC2A, CL, T1S, and SVA did not deteriorate at the last follow‐up, which indicate the effect of cervical sagittal alignment maintenance is satisfactory in this technique.
Strengths and Limitations
The present study first reported the safety and efficiency of bilateral atlantoaxial joints bone autografting in cable‐dragged reduction and cantilever‐beam internal fixation. Patients with atlantoaxial dislocation or instability could achieve promising clinical and radiological results with fewer complications. It is also a cost‐effective procedure in the surgical treatment of patients with atlantoaxial dislocation or instability. Nevertheless, our study has several limitations. First, it was a retrospective study with inherent limitations. Second, the sample size was relatively small due to the low incidence of the disease and the limited follow‐up period. Third, there were a variety of posterior surgical techniques for atlantoaxial dislocation, but we only investigated the cable‐dragged reduction and cantilever beam internal fixation in this study. Taken together, the early outcomes of bone autografting in the bilateral atlantoaxial joints in cable‐dragged reduction and cantilever beam internal fixation demonstrated safety and effectiveness in treating atlantoaxial dislocation or instability. Thus, prospective studies with larger sample sizes and longer follow‐up duration will be the focus of our future study.
Conclusion
Bone autografting of the bilateral atlantoaxial joints is safe and effective in the surgical treatment of atlantoaxial dislocation or instability. The technique has the advantages of increasing bone fusion rates, shorting bone fusion time and reducing complication rates when the cable‐dragged reduction and cantilever beam internal fixation approach is used. As evidenced in this study, we believe bone autografting of the bilateral atlantoaxial joints is a safe and cost‐effective surgical procedure for treating patients with atlantoaxial dislocation or instability.
Conflict of Interest Statement
All authors have no conflicts of interest in this work.
Authorship Declaration
We declare that all authors listed meet the authorship criteria according to the latest guidelines of the International Committee of Medical Journal Editors. All authors agree to the final submitted manuscript.
Author Contributions
Xing‐jin Wang and Hao Liu collected the raw data and prepared the manuscript. Bei‐yu Wang and Ting‐kui Wu performed statistical analysis and interpreted the data. Jun‐bo He and Lu Yan performed radiograph analysis. Chen Ding designed the study. All authors have read and approved the final manuscript.
Acknowledgments
We would like to thank the editors, reviewers, and other persons for their assistance to improve the manuscript. This work is supported by the Cadre Health Research Project of Sichuan Province (Grant no ZH2023‐105 to Hao Liu), the 1.3.5 project for Postdoctoral Foundation of West China Hospital of Sichuan University (Grant no 2023HXBH080 to Ting‐kui Wu) and the 1.3.5 project for disciplines of excellence—Clinical Research Incubation Project of West China Hospital of Sichuan University (Grant no 2022HXFH017 to Chen Ding).
Xing‐jin Wang and Hao Liu contributed equally to this work and should be considered co‐first authors.
References
- 1. Yang JS, Chen H, Chu L, Liu P, Yan L, Liu TJ, et al. Does additional bone grafting of atlantoaxial joint increase bone fusion rate of iliac crest autograft in posterior occipitocervical fusion? Retrospective, controlled study with 2‐year follow‐up. World Neurosurg. 2019;125:e29–e34. [DOI] [PubMed] [Google Scholar]
- 2. Zhou X, Li S, Liu H, Guo Q, Guo X, Chen F, et al. Comparison of two bone grafting techniques applied during posterior C1‐C2 screw‐rod fixation and fusion for treating reducible atlantoaxial dislocation. World Neurosurg. 2020;143:e253–e260. [DOI] [PubMed] [Google Scholar]
- 3. Zhang L, Wang H. Biomechanical effects of lateral inclination C(1) and C(2) pedicle screws on atlantoaxial fixation. Orthop Surg. 2021;13(7):2027–2033. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 4. Liu X, Liu H, Li T, Gong Q, Song Y, Liu L, et al. Treatment of irreducible old atlantoaxial subluxation with cable‐dragged reduction and cantilever beam internal fixation. Spine. 2011;36(15):E983–E992. [DOI] [PubMed] [Google Scholar]
- 5. Shen Q, Xia Y, Xu T. Clinical outcomes of atlantoaxial dislocation combined with osteoporosis using posterior atlantoaxial rod, screw fixation, and posterior interfacet fusion: a retrospective study of 21 cases. Med Sci Monit. 2020;26:e925187. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 6. Li C, Li L, Li Z, Mei Y, Huang S. Surgical management for posterior atlantoaxial dislocation without fracture and atlantoaxial dynamic test to confirm the integrity of the transverse ligament: a case report. Orthop Surg. 2022;14(2):451–455. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 7. Wang HW, Yin YH, Li T, Yu XG, Qiao GY. Effects of transverse connector on reduction and fixation of atlantoaxial dislocation and basilar invagination using posterior C1‐C2 screw‐rod technique. Spine J. 2019;19(12):1995–2002. [DOI] [PubMed] [Google Scholar]
- 8. Ghaith AK, Yolcu YU, Alvi MA, Bhandarkar AR, Sebastian AS, Freedman BA, et al. Rate and characteristics of vertebral artery injury following C1‐C2 posterior cervical fusion: a systematic review and meta‐analysis. World Neurosurg. 2021;148:118–126. [DOI] [PubMed] [Google Scholar]
- 9. Lall R, Patel NJ, Resnick DK. A review of complications associated with craniocervical fusion surgery. Neurosurgery. 2010;67(5):1396–1403. [DOI] [PubMed] [Google Scholar]
- 10. Rajinda P, Towiwat S, Chirappapha P. Comparison of outcomes after atlantoaxial fusion with C1 lateral mass‐C2 pedicle screws and C1‐C2 transarticular screws. Eur Spine J. 2017;26(4):1064–1072. [DOI] [PubMed] [Google Scholar]
- 11. Zhang YH, Shen L, Shao J, Chou D, Song J, Zhang J. Structural allograft versus autograft for instrumented atlantoaxial fusions in pediatric patients: radiologic and clinical outcomes in series of 32 patients. World Neurosurg. 2017;105:549–556. [DOI] [PubMed] [Google Scholar]
- 12. Goel A, Laheri V. Plate and screw fixation for atlanto‐axial subluxation. Acta Neurochir. 1994;129(1–2):47–53. [DOI] [PubMed] [Google Scholar]
- 13. Li S, Ni B, Xie N, Wang M, Guo X, Zhang F, et al. Biomechanical evaluation of an atlantoaxial lateral mass fusion cage with C1‐C2 pedicle fixation. Spine. 2010;35(14):E624–E632. [DOI] [PubMed] [Google Scholar]
- 14. Wang YL, Wang XY. Improved bone graft method for upper cervical surgery with posterior approach: technical description and report of 52 cases. World Neurosurg. 2018;114:e66–e69. [DOI] [PubMed] [Google Scholar]
- 15. Wang LN, Li T, Yang X, Wang L, Liu LM, Liu H, et al. Comparison of two temporary fixation techniques for the treatment of type II odontoid fracture. Acta Orthop Belg. 2018;84(1):108–115. [PubMed] [Google Scholar]
- 16. Zhu C, Wang L, Liu H, Song Y, Liu L, Li T, et al. Treatment of type II odontoid fracture with a novel technique: titanium cable‐dragged reduction and cantilever‐beam internal fixation. Medicine. 2017;96(44):e8521. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 17. Stemper BD, Marawar SV, Yoganandan N, Shender BS, Rao RD. Quantitative anatomy of subaxial cervical lateral mass: an analysis of safe screw lengths for Roy‐Camille and magerl techniques. Spine. 2008;33(8):893–897. [DOI] [PubMed] [Google Scholar]
- 18. Eck KR, Lenke LG, Bridwell KH, Gilula LA, Lashgari CJ, Riew KD. Radiographic assessment of anterior titanium mesh cages. J Spinal Disord. 2000;13(6):501–509. [DOI] [PubMed] [Google Scholar]
- 19. Elliott RE, Tanweer O, Boah A, Morsi A, Ma T, Smith ML, et al. Atlantoaxial fusion with screw‐rod constructs: meta‐analysis and review of literature. World Neurosurg. 2014;81(2):411–421. [DOI] [PubMed] [Google Scholar]
- 20. Guo X, Ni B, Xie N, Lu X, Guo Q, Lu M. Bilateral C1‐C2 transarticular screw and C1 laminar hook fixation and bone graft fusion for reducible atlantoaxial dislocation: a seven‐year analysis of outcome. PLoS One. 2014;9(1):e87676. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 21. Huang DG, Zhang XL, Hao DJ, Yu CC, Mi BB, Yuan QL, et al. Posterior atlantoaxial fusion with a screw‐rod system: allograft versus iliac crest autograft. Clin Neurol Neurosurg. 2017;162:95–100. [DOI] [PubMed] [Google Scholar]
- 22. Ishida W, Ramhmdani S, Xia Y, Kosztowski TA, Xu R, Choi J, et al. Use of recombinant human bone morphogenetic protein‐2 at the C1‐C2 lateral articulation without posterior structural bone graft in posterior atlantoaxial fusion in adult patients. World Neurosurg. 2019;123:e69–e76. [DOI] [PubMed] [Google Scholar]
- 23. Goel A. Atlantoaxial joint jamming as a treatment for atlantoaxial dislocation: a preliminary report. Technical note. J Neurosurg Spine. 2007;7(1):90–94. [DOI] [PubMed] [Google Scholar]
- 24. Martin MD, Bruner HJ, Maiman DJ. Anatomic and biomechanical considerations of the craniovertebral junction. Neurosurgery. 2010;66(3):2–6. [DOI] [PubMed] [Google Scholar]
- 25. Ghostine SS, Kaloostian PE, Ordookhanian C, Kaloostian S, Zarrini P, Kim T, et al. Improving C1‐C2 complex fusion rates: an alternate approach. Cureus. 2017;9(11):e1887. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 26. Bogduk N, Mercer S. Biomechanics of the cervical spine. I: Normal kinematics. Clinical Biomechanics. Volume 15. Bristol, Avon: Elsevier; 2000. p. 633–648. [DOI] [PubMed] [Google Scholar]
- 27. Frost HM. Wolff's law and bone's structural adaptations to mechanical usage: an overview for clinicians. Angle Orthod. 1994;64(3):175–188. [DOI] [PubMed] [Google Scholar]
- 28. He B, Yan L, Xu Z, Chang Z, Hao D. The causes and treatment strategies for the postoperative complications of occipitocervical fusion: a 316 cases retrospective analysis. Eur Spine J. 2014;23(8):1720–1724. [DOI] [PubMed] [Google Scholar]
- 29. de Carvalho PS, Vasconcellos LW, Pi J. Influence of bed preparation on the incorporation of autogenous bone grafts: a study in dogs. Int J Oral Maxillofac Implants. 2000;15(4):565–570. [PubMed] [Google Scholar]
- 30. He X, Meng Y, Zhang J, Hang Y, Yang J, Wu Q, et al. Bone grafting of atlantoaxial joints and occipitocervical or atlantoaxial fusion for the reduction and fixation of basilar invagination with atlantoaxial dislocation by a posterior approach: a preliminary study. World Neurosurg. 2017;100:230–235. [DOI] [PubMed] [Google Scholar]
- 31. Kaufman HH, Jones E. The principles of bony spinal fusion. Neurosurgery. 1989;24(2):264–270. [DOI] [PubMed] [Google Scholar]
- 32. Huang DG, Hao DJ, He BR, Wu QN, Liu TJ, Wang XD, et al. Posterior atlantoaxial fixation: a review of all techniques. Spine J. 2015;15(10):2271–2281. [DOI] [PubMed] [Google Scholar]
- 33. Tang C, Li GZ, Liao YH, Tang Q, Ma F, Wang Q, et al. Importance of the occipitoaxial angle and posterior occipitocervical angle in occipitocervical fusion. Orthop Surg. 2019;11(6):1054–1063. [DOI] [PMC free article] [PubMed] [Google Scholar]