Application of the O-arm Intraoperative Imaging System to Assist Anterior Cervical Screw Fixation for Odontoid Fractures

Summary

This study describes the application of the O-arm intraoperative imaging system in odontoid fractures.

Abstract

Odontoid fractures account for a large proportion of cervical spine fractures in the elderly, causing pain in the occiput and the back of the neck and restricting neck movement. Anterior cervical screw fixation is a common surgical procedure to treat odontoid fractures. Due to the special location and complex anatomy of the odontoid, surgeons need to perform intraoperative fluoroscopies repeatedly to ensure correct screw position and avoid damage to the peripheral nerves and vessels of the odontoid. The traditional anterior cervical screw fixation is usually conducted with the assistance of a C-arm. However, compared to the C-arm, an O-arm intraoperative imaging system can provide 3D images during surgery, which improves the accuracy of screw placement. This study retrospectively analyzed patients with anterior cervical odontoid fractures treated in our hospital. The application of the O-arm intraoperative imaging system for assisting screw placement in the treatment of odontoid fractures can reduce intraoperative blood loss, operation time, and trauma to the patients.

Introduction

Odontoid fracture is a common form of cervical spine fracture, accounting for approximately 20% of all cervical spine fractures. Odontoid fracture mainly occurs in adults over the age of 65¹. Odontoid process displacement resulting from an external force acting on the cervical spine is the main cause of odontoid process fractures. The main symptoms of odontoid fracture are pain in the occiput and the back of the neck and immobility. According to Anderson's classification², odontoid fractures can be divided into three types. Type I and type III odontoid fractures can achieve satisfactory results with conservative treatments, while patients with type II odontoid fractures often need surgical treatments^3,4.

Current surgical treatments are anterior and posterior screw fixations. The posterior screw fixation technique provides more stable fixation, while the anterior screw fixation technique maintains 80%-100% of the rotational function of the atlantoaxial vertebra. However, because posterior cervical screw fixation causes greater trauma to patients^5,6, treatment of odontoid fractures using anterior screw fixation is increasingly accepted by spine surgeons. The traditional anterior cervical screw fixation is usually conducted with the assistance of a C-arm. However, the complex structures of the anterior neck, the free fracture end, and the size of the patients all obstruct the accurate placement of screws through the anterior neck. High-quality images are desired when navigating accurate screw placement, which is difficult to achieve using the current C-arm system. Therefore, unexpected intraoperative blood loss and longer operation time, as well as more trauma to the patients, may occur when using C-arm to assist the surgery.

The O-arm intraoperative imaging system can provide CT scan images during the operation. Compared with the traditional 2D intraoperative fluoroscopy, the O-arm intraoperative imaging system can detect screw dislocation during the operation, enabling the surgeon to make timely revisions and avoid secondary surgery⁷. The advanced O-arm intraoperative imaging and navigation system can achieve intraoperative 3D CT imaging and provide precise intraoperative navigation. Studies have confirmed that the application of the O-arm navigation-assisted technique in complex surgery can improve the accuracy of screw placement and reduce internal fixation-related complications^6,8,9. Figure 1 shows the application of the O-arm intraoperative imaging system. This study aims to investigate the application of the O-arm intraoperative imaging system in the treatment of odontoid fractures with anterior cervical screws.

Protocol

This study has been approved by the Ethics Committee of the Third Hospital of Hebei Medical University. The patients signed informed consent, and the patients consented to film and allowed the investigators to use their surgical data. A total of 40 patients were included in this study.

1. Preoperative preparation

1. Select patients based on the following inclusion criteria: i) patients who need surgical treatment due to trauma to the odontoid process of the axis, ii) patients operated by the same surgeon, and iii) cervical MRI images that show no degeneration and obvious edema of the cervical spinal cord.
2. Ensure the following exclusion criteria while selecting patients: i) patients with spinal ankylosis, tumors, and other diseases, ii) combined atlantoaxial joint transverse ligament injury, and iii) severe bleeding tendency or coagulation disorder.
3. Have the patients undergo a routine preoperative examination after admission. Ensure that the patients are accompanied by a doctor to perform imaging examinations, including the anterior and lateral X-ray of the cervical spine, X-ray with mouth open, atlantoaxial CT examination, and the patient's cervical spine MRI.
4. Make it routine for patients to undergo cranial traction (traction weight 2-5 kg) before the operation.
   1. Keep horizontal maintenance traction (traction weight of 2 kg) for patients with no obvious displacement of odontoid fractures.
   2. For those with posterior displacement of the odontoid fractures, perform horizontal traction first, and then increase the traction weight according to the reset situation. After the X-ray shows complete reduction of the fracture end, reduce the traction weight to 2 kg.
5. Review the patients' bedside X-ray films every 2 days. Have the surgeons adjust the position and traction weight according to the displacement of the odontoid process. After the fracture reaches full reduction, perform surgery to fix the fracture. Ensure that the patients have fasted for 12 h before surgery and that the surgical site is well prepared. Take the 20 cm area around the surgical incision as the skin preparation area. Use a razor to remove hair from the skin preparation area.

2. Surgical procedures

1. Place the patient in a supine position on the operating table. Sedate the patient by intravenous administration of propofol, rocuronium bromide, sufentanil, and midazolid at dosages of 2 mg/kg, 0.15 mg/kg, 0.4 µg/kg, and 0.05 mg/kg, respectively.
2. After the patient loses consciousness, perform endotracheal intubation.
   1. Have the anesthesiologist prop up the patient's occiput properly and tilt the head back.
   2. After the patient has inhaled pressurized, pure oxygen through a mask for 3-5 min, have the anesthesiologist open the patient's mouth with the right thumb, forefinger, and middle finger. Hold the laryngoscope with the left hand to expose the glottis and then pass the catheter through the mouth in an arc through the glottis and into the pharynx and trachea with the right hand.
3. Place the tooth pad, take out the laryngoscope, inflate the cuff, and then auscultate both lungs. After confirming the position of the catheter, fix the catheter and the tooth pad with adhesive tape, and connect the ventilator for respiratory support.
4. Take an X-ray before the start of surgery to ensure that the odontoid is in reduction.
5. Perform routine disinfection and draping to the surgical incision site (the right side of the upper edge of the C4-5). Use 2% iodine to sterilize the surgical incision 3x and use 75% alcohol for deiodination and alcohol disinfection 3x. Disinfect up to the lower lip, down to the nipple, and both sides to the front edge of the trapezius muscle. During the drape laying process, take care to move the drape only from the inside to the outside.
6. Use a scalpel to make a 4-5 cm transverse incision on the right side at the upper edge of C4-5. Cut the skin, subcutaneous tissue, and platysma in sequence, and use high-frequency electrocautery to stop the bleeding. Instruct the assistant to use tissue forceps to separate the upper and lower platysma muscle to facilitate retraction and blunt separation of the vascular sheath and visceral sheath. Use the skin retractor to retract to both sides to expose the prevertebral fascia and longus neck muscle and peel it off with a periosteal peeler to separate the prevertebral fascia.
7. Secure the inside of the O-arm workflow with a sterile cloth. Move the O-arm to the surgical site. After turning on the O-arm intraoperative imaging system, perform a 3D scan of the surgical site to determine the C2-3 space.
8. After the C2-3 segment is confirmed, tilt the O-arm 45° to make room for surgery. Use a rongeur to remove a small amount of the labial bone at the lower edge of the C2 vertebra.
9. Under O-arm fluoroscopy, place a 1.5 mm diameter guide wire in the middle of the lower border of the C2 vertebral body. Keep the guidewire in the midsagittal position of the odontoid and tilt it back 15-20°. Under the supervision of the O-arm, drill the guide wire to the tip of the odontoid. Use a hollow drill to create a nail channel along the guide wire and a hollow tap to shape a thread channel.
10. After the guide needle reaches the top of the odontoid, measure the length of the guide wire entering the vertebral body and wait for the surgeon to screw in a 3.5 mm diameter, hollow titanium screw of a suitable length along the guide needle.
11. After screw placement, perform 3D scanning again with the O-arm to observe the screw implantation in all directions and carefully withdraw the guide needle.
12. Fully rinse the wound and perform indwelling drainage. Use a No. 10 thread wire to fix the drainage tube. Suture the platysma muscle with the No. 10 thread, the fascia between the platysma and the skin with the No. 4 thread, and the skin intradermally with the No. 0 thread.

3. Post-surgery

1. Administer antibiotics to the patients for 3 days after the operation. Pull the drainage out 3 days after the operation.
2. Instruct the patients to start walking on the ground while wearing a cervical collar and use the cervical collar continuously for 3 months.

Results

Anterior cervical screw fixations were performed in 40 patients with odontoid fractures, of whom 21 patients underwent surgeries with the assistance of the O-arm intraoperative imaging system (Group O), and 19 patients underwent surgeries with the assistance of the C-arm (Group C). Data are presented as mean (± SD). The average age of Group O was 42.86 (± 10.36) years, while the average age of Group C was 41.05 (± 9.83) years. There was no significant difference in age between the two groups of patients. B...

Discussion

Odontoid fractures are usually caused by violent injury; common symptoms are pain and limited mobility. Some patients also experience nerve compression symptoms. In some patients, the degree of fracture displacement is relatively large, and the fracture fragments compress the spinal cord and cause symptoms of paraplegia and neuralgia. Some patients with odontoid fractures also have symptoms of hand weakness and difficulty in walking. Type II odontoid fractures have poor self-healing potential and often require surgical t...

Materials

Name	Company	Catalog Number	Comments
Bipolar electrocoagulation tweezers	Juan'en Medical Devices Co.Ltd	BZN-Q-B-S	1.2 mm x 190 mm
Cannulated Lag Screws	Medtronic Sofamor Danek USA ,Inc	873-146	4.0 mm x 46 mm
High frequency active electrodes	ZhongBangTianCheng	GD-BZ	GD-BZ-J1
Laminectomy rongeur	Qingniu	2054.03	220 x 3.0 x 130°
Laminectomy rongeur	Qingniu	2058.03	220 x 5.0 x 130°
Pituitary rongeur	Qingniu	2028.01	220 x 3.0 mm
Pituitary rongeur	Qingniu	2028.02	220 x 3.0 mm
Surgical drainage catheter set	BAINUS MEDICAL	SY-Fr16-C	100-400 mL
Surgical film	3L	SP4530	45 x 30 cm