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

Abstract

Introduction:

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

Methods:

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

Results:

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

Conclusion:

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

Keywords

irreducible atlantoaxial dislocation irreducible dislocation reduction and fixation submandibular approach

Introduction

Irreducible atlantoaxial dislocation (IAAD) has various etiologies^1

–5 and can result in occipitocervical cord compression. IAAD treatment is challenging for spine surgeons, and various procedures have been used.^{6

–14} Irrespective of the procedure type, sufficient release of the dislocated atlantoaxial joint is of key importance. The anterior transoral or posterior approach or a combination of both is common. The transoral approach has a high risk of infection,^6,15 while the posterior approach has a high risk of nerve root injury and massive bleeding.^13,14 Thus, an approach to sufficiently release the dislocated atlantoaxial joint without complications is required.

The anterior retropharyngeal approach by removing the submandibular gland is performed in the vascular plane and is entirely extraoral and extramucosal. When IAAD becomes reducible after sufficient anterior submandibular retropharyngeal release, sequential posterior fixation of C1 and C2 can be performed to complete the final reduction. Therefore, the anterior submandibular retropharyngeal release and sequential posterior reduction and fixation may be a good option to treat IAAD. The present study reports the feasibility and clinical outcomes of the technique.

Materials and methods

Patients

Following the institutional review board’s approval, the records of 13 consecutive patients surgically treated at the Affiliated Hospital of Qingdao University (Qingdao, China) from March 2007 to May 2015 were retrieved from the database. There were eight men and five women, with a mean age of 47.1 years and age range of 21–70 years. The inclusion criterion was IAAD. IAAD diagnosis was based on Yuan’s criteria¹⁶ of sagittal atlantoaxial joint inclination >32.5° and atlantoaxial joint reduction index <27.9%. The exclusion criteria were previous surgery in the cervical spine, tumor, and trauma. The cause of IAAD was os odontoideum (n = 4), atlantoaxial transverse ligament rupture (n = 3), or old odontoid fracture (n = 6; Table 1). The patients had neck pain, numbness of extremities, weakness, and gait abnormality (Table 1).

Table 1.

Patient demographic and clinical data.

Case no.	Gender	Age	Etiology	Atlantoaxial reduction index (%)	Sagittal atlantoaxial joint inclination	Preoperative JOA score	Final follow-up JOA score	Follow-up time (months)
1	Male	21	Os odontoideum	19.2	38°	6	14	36
2	Female	43	Altantoaxil transverse ligament rupture	15.6	41°	7	13	18
3	Male	54	Old odontoid fracture	23.5	36°	7	14	24
4	Male	60	Os odontoideum	25.7	35°	9	16	24
5	Male	54	Altantoaxil transverse ligament rupture	21	39°	10	16	30
6	Female	48	Altantoaxil transverse ligament rupture	14.7	46°	9	13	30
7	Female	70	Old odontoid fracture	20.6	34°	6	10	12
8	Male	62	Os odontoideum	18.2	40°	8	14	18
9	Female	58	Old odontoid fracture	26.3	37°	9	17	24
10	Male	25	Os odontoideum	19.7	36°	10	16	24
11	Female	49	Old odontoid fracture	20.5	38°	9	15	20
12	Male	38	Old odontoid fracture	14.3	47°	6	13	24
13	Male	30	Old odontoid fracture	18.5	41°	6	14	36

Preoperative preparation

The patients underwent a careful physical examination. The routine preoperative Japanese Orthopaedic Association (JOA) scoring was also performed. The patients were assessed by cervical plain radiography and dynamic radiography, three-dimensional computed tomography (3DCT) reconstruction, and magnetic resonance imaging (MRI). Preoperative skull traction of a weight of 6–10 kg was performed to estimate the reducibility of atlantoaxial dislocation and to release the soft tissues surrounding the joint. Each surgical procedure was performed by the same senior spine surgeon (correspondence author).

Anterior submandibular retropharyngeal release

Following general anesthesia and endotracheal intubation, the patients were placed in a supine position, with a pillow under the shoulder and skull traction of a weight of 6–10 kg using Gardner-Well tongs was performed. Somatosensory evoked potential and motion evoked potential monitoring were performed for spinal cord function during the operation. A 5-cm transverse incision was made 2 cm inferior to the right angle of the mandible. The superficial fascia and platysma were divided in line with the incision. The submandibular gland was retracted superiorly. Care was taken not to injure the superior laryngeal nerve. Subsequently, a blunt dissection was performed in the retropharyngeal space between the lateral carotid sheath and the medial larynx and pharynx. The anterior longitudinal ligament and the longus colli muscle were subperiosteally elevated to expose the atlantoaxial joint capsule and space. The osteophytes and the scar tissue inside the atlantodental interval were resected. A curette or elevator was inserted in the joint space to lever the joint under continuous traction and remove the tissue that was hindering reduction. A successful tissue release was achieved when the joint space between the lateral masses of C1 and C2 was elevated to 3–5 mm. Subsequently, the atlantoaxial surface was abraded using a bur to permit bone fusion. A drainage tube was placed, and the incision was sutured. During the whole process of anterior release, a surgical headlight was used to provide necessary lighting to the operative field.

Posterior reduction and fixation

Following anterior submandibular retropharyngeal release, the patient was placed in a prone position, with the head fixed using a Mayfield head holder. A routine midline incision was made to expose the posterior edge of the foramen magnum, C1 lateral mass, C2 lamina, and C2 pars. Based on Tan’s method,¹⁹ 3.5-mm polyaxial pedicle screws (length: 20–26 mm, Medtronic, Memphis, Tennessee, USA) were inserted in C1 and C2. The screw positions were confirmed on fluoroscopy. Two pre-bent titanium rods (diameter: 3.5 mm) were connected longitudinally between the bilateral pedicle screws. The locking caps were locked in C2, and the rods were pushed down to connect the pedicle screws of C1. Subsequently, the locking caps were tightened at C1. Using the strength of the pullout, final reduction was accomplished by locking the caps. A grainy autologous iliac crest graft was placed. After placing the drainage tube, the incision was closed.

Postoperative management

The patients were extubated in the operating room uneventfully. They were routinely administered with antibiotics for 24–48 postoperative hours. The drainage tube was removed after the drainage was less than 50 mL/day. The patients were asked to wear a cervical collar for 6–8 weeks and start cervical muscle rehabilitation exercises after 3 postoperative weeks.

Follow-up and therapeutic evaluation

The patients underwent cervical plain radiography and dynamic radiography scans at 3–4 postoperative days, after the drainage tube was removed. The patients were asked to follow up postoperatively at 3, 6, 12, 24, and 36 months. Patients’ neurological functions were evaluated in clinical follow-ups every 6 months. The operation time, blood loss, and intraoperative and postoperative complications were recorded. At the final follow-up, the JOA score was recorded, and cervical 3DCT reconstruction was performed to confirm that the internal fixation devices were in position and graft had fused with the bone. MRI was performed to evaluate the spinal cord.

Statistical analysis

The Statistical Package for the Social Sciences software (version 19.0; SPSS, Inc., Chicago, Illinois, USA) was used for data analysis. The t-test was used for the comparison and analysis of JOA scores. The value of p < 0.05 was considered statistically significant.

Ethical approval

The study was approved from the Ethics Committee of Qingdao University. The study was conducted in accordance with the Helsinki Declaration. Due to the retrospective nature of the study, written informed consent from the patients was waived.

Results

The surgeries were successfully accomplished. Neurological deterioration or tracheal or esophageal injury did not occur intraoperatively. A satisfactory screw position was confirmed in all patients. The mean operation time was about 3.8 h, and the mean estimated blood loss was 130 ± 27 mL. The patients were followed up for 12–36 months, with a mean follow-up period of 22.8 months. During the follow-up, the patients’ neck pain, numbness of extremities, and weakness were found to have improved. The preoperative mean JOA score was 7.85 ± 2.28, while the final follow-up mean JOA score was 14.23 ± 3.1, showing a significant difference (p < 0.05). Rigid internal fixation and atlantoaxial reduction were confirmed on the cervical radiograph (Figure 1). At the final follow-up, the cervical 3DCT reconstruction showed rigid internal fixation with no screw loosening or screw or rod breakage. MRI showed good spinal cord decompression.

Figure 1.

Case 12, 38-year-old male with IAAD from old dens fracture underwent anterior submandibular retropharyngeal release and posterior reduction and fixation. (a) and (b) Preoperative dynamic radiograph showed IAAD. (c) Sagittal CT scan showed that the sagittal atlantoaxial joint inclination is 47°, which means IAAD. (d) Intraoperative skull traction using Gardner-Well tongs. (e) Anterior exposure via submandibular retropharyngeal approach. (f) Postoperative lateral X-ray at the 6-month follow-up showed satisfactory atlantoaxial reduction. IAAD: irreducible atlantoaxial dislocation; CT: computed tomography; MRI: magnetic resonance imaging.

Postoperatively, the patients experienced pharyngeal pain, which was considered to be associated with intraoperative traction. One patient had a vague voice and increased oral discharge postoperatively, which disappeared after 5 days. No patient had pharyngeal or chest infection, deep vein thrombosis, or dyspnea.

Discussion

Various etiologies,^1

–4 such as congenital os odontoideum, old dens fracture, and transverse ligament rupture, can cause IAAD and result in neck pain, dizziness, and occipitocervical cord compression. There are various methods to treat IAAD, including transoral odontoidectomy and posterior decompression and fixation,⁶ transoral atlantoaxial reduction plate internal fixation,^7
–9 transoral atlantoaxial release and posterior internal fixation,^10
–12 and direct posterior reduction and fixation.^13,14 However, these methods have several disadvantages. For example, the transoral approach, which can provide a direct vision of the C1–C2 pathologies, has a high tendency to cause infections^6,15 and cannot be used in patients with limited mouth opening. The posterior facet joint release is difficult to manipulate. An aberrant vertebral artery is common in the craniovertebral junction, C2 nerve roots, and venous plexus around the C2 lateral mass; hence, care should be taken not to damage these structures. Although rare, the damage is catastrophic. This procedure also has a long learning curve for young surgeons.¹⁴

The anterior submandibular retropharyngeal approach is entirely extraoral and extramucosal and familiar to spine surgeons. There is no risk of infection due to oral flora. Hao et al.¹⁷ reported 22 patients with IAAD who underwent single-stage anterior retropharyngeal release and sequential posterior fusion. The patients had bone fusion at an average follow-up of 32 months. JOA scores of 12 patients with myelopathy improved from 8.3 to 13.9, and the mean improving rate was 87.5%. Transient hoarseness and dysphagia developed in two cases in the immediate postoperative period. No complications associated with the marginal branch of the facial nerve, hypoglossal nerve, or submandibular gland occurred. No infection, cerebrospinal fluid leak, or thromboembolism was found in the series. Sirvastava et al.¹⁸ reported 19 consecutive patients with IAAD who underwent posterior fusion after anterior release. The anterior release was performed via the transoral approach in 12 patients and the retropharyngeal approach in 7. The JOA score improved from the preoperative mean of 12.89 to a postoperative mean of 16.84. Fusion was achieved in all patients. As the results obtained were similar using both the approaches, the choice of approach depends on the surgeon’s familiarity. In the present study, the 13 patients with IAAD underwent posterior reduction and fixation after sufficient anterior submandibular retropharyngeal release. JOA scores improved from the preoperative mean of 7.85 to the postoperative mean of 14.23. No neurological deterioration or tracheal or esophageal injury occurred. The patients experienced postoperative pharyngeal pain, which was probably associated with intraoperative traction. No pharyngeal infection, chest infection, deep vein thrombosis, or dyspnea occurred.

The anterior release is of key importance in treating IAAD. In the present study, a curette or elevator was inserted in the atlantoaxial joint space to lever the joint under continuous traction and remove the tissue that was hindering reduction. According to Tan et al.,¹⁹ a successful tissue release was achieved when the joint space between the lateral masses of C1 and C2 was elevated to 3–5 mm. This was verified in the present study. After the successful anterior release, posterior fixations of C1 and C2 were performed for the final reduction.

There are certain limitations to the present study: (1) small sample size, (2) retrospective design, and (3) no control group. For patients with a big body habitus and short neck, the anterior submandibular retropharyngeal release may be difficult. We have seldom experienced such patients. Future prospective comparative studies may provide insight in the advantages and disadvantages of the procedure.

Conclusion

Footnotes

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

ORCID iD

Yongming Xi

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