Surgery result assessment of C1 lateral mass and C2 pedicle screw fixation in treating unstable C2 odontoid/ dens fracture in phu tho general hospital – Son Nguyen Van

JMR 116 E3 (7) - 2018 53 JOURNAL OF MEDICAL RESEARCH SURGERY RESULT ASSESSMENT OF C1 LATERAL MASS AND C2 PEDICLE SCREW FIXATION IN TREATING UNSTABLE C2 ODONTOID/ DENS FRACTURE IN PHU THO GENERAL HOSPITAL Son Nguyen Van1, Toan Do Thi Thanh2, Ngoc Nguyen Huy1, Hoat Luu Ngoc2 1Phu Tho General Hospital, Vietnam; 2Hanoi Medical University, Vietnam Superior cervical spinal lesions account for 25% of cervical spinal lesion. Due to the special structure of superior cervical spine and the diversity of anatomical lesions, various non-surgical treatment methods such as Mini Verve powder, Halo frame, continuous traction, as well as surgical methods such as occipital splints, screwing through joints, C1 - C2 posterior arch binding, screwing through the odontoid process...have been applied to treat these lesions.Comparing these techniques, the fixation of the C1 lateral mass and C2 pedicle with polyaxial screws has many advantages and has been widely applied in recent years. The aim of this study was to assess the result of Atlantal lateral mass and axis pedicle screw fixation for the treatment of unstable C2 odontoid fracture. We investigated the clinia records of 20 patients suffered from unstable C2 odontoid fracture whom received an Atlantal lateral mass and axis pedicle screw fixation at Phu Tho General hospital from 1/2012 to 12/2015. Of all the patients, no intraoperative complications were observed. The av- erage recovery time was 15 days, as being judged by clinical systems after surgery without major neurologi- cal complications and wound infection. We concluded that the C1 lateral mass and C2 pedicle screw fixation for treatment of unstable odontoid fracture is a suitable option for these conditions with a high success rate and few complications. Keywords: C1 lateral mass, C2 pedicle screw fixation, unstable C2 odontoid/dens fracture I. INTRODUCTION C2 Odontoid fractures account for 10 - 20% of cervical spine fractures. However, only type II unstable odontoid fractures, or included with C1 - C2 dislocation, are candidates for surgery [1 - 3]. These surgeries would solidify the vertebrae and decompress it if needed. There are multiple treatment methods for C2 odontoid fracture and two main types of treat- ments are anterior fusion and posterior fusion: Anterior fusion by screw inter-articulation odontoid was first performed by Bohler. This technique involves directly fixing the fractured line, solidifying the vertebrae and maintaining C1 - C2 rotational movement. The bone weld- ing rate with this technique is approximately 90%. However, this technique is difficult to perform when the fractured odontoid is com- bined with C1 - C2 dislocation [3]. Posterior fusion to achieve stable fixation of C1 - C2 junction consists of multiple differ- ent methods such as Magerl’s screw inter- articulation C1 - C2 surgery with a relatively high bone welding rate of 78 - 99%. However, the risk of damage to the vertebral artery is high and this method is difficult to perform to severe C1 - C2 dislocation in patients with a thoracic kyphosis (Hunchbacked) [4; 5]. In 2001, Harms and Melcher disseminated the technique of C1 lateral mass and C2 pedicle screw fixation. Harms’ C1 - C2 fixation method Corresponding author: Do Thi Thanh Toan, Ha Noi Medical University Email: [email protected] Received: 15/7/2018 Accepted: 18/11/2018 54 JMR 116 E3 (7) - 2018 JOURNAL OF MEDICAL RESEARCH is a suitable option with low risk, easily mend- able C1 - C2 and high bone welding rate [6]. We studied and applied the posterior C1 lateral mass and C2 pedicle screw fixation for treating unstable C2 odontoid fracture and dislocated C1 - C2 in order to evaluate the result as well as the advantages and disad- vantages of this method. II. METHODS 1. Subjects Patients who suffered from unstable C2 odontoid fracture and received a atlantal lat- eral mass and axis pedicle screw fixation at Phu Tho General Hospital in 3 years, from 01/2012 to 12/2015. Inclusion criteria + Suffered from unstable C2 odontoid frac- ture. + Were operated in atlantal lateral mass and axis pedicle screw fixation. 2. Methods - Study design: A case series study . - Time: from 1/2012 to 12/2015. - Place: Phu Tho General hospital. - Sample size and Sampling: Total sam- pling during the study period is 20 patients met criteria. They were all included in the study. - Variables + Perioperative clinical symptoms. + Assessment of nerve damage according to ASIA scale. + Assessment and classification of C1 - C2 damage through conventional X-ray imaging (straight, lateral, open- mouth). + Assessment of the condition of the vertebrae, classification of the spinal damage, determination of the anatomical structure of the vertebrae and C1 lateral mass and meas- urement the size of C2 stem and to have a post-op precision of the position and location of screw insertion by 64 rows of computed tomography with perioperative vertebral artery rendering. + Assessment of the spinal cord, soft tissue and to determine patient prognosis through MRI. Operative technique The patients received tracheal intubation in the prone position and their heads were fixed on May-Few frame. The incision was made along to the ligamentum flavum, in the bottom of the occipital C5, C6. The lower bone mem- brane of muscle mass next to spondylosis was then incised to the outer edge of C2 - C3 joint. The lower bone membrane above the C1 pos- terior arch was then exposed to enable the visualization of the C1 lateral mass and to al- low for the inner side of the C1 lateral mass. The vertebral artery runs along artery channel above C1 posterior arch, and the C2 nerve root usually lies from lateral mass to the C1 posterior arch. After protecting vertebral artery and C2 root by high-speed grinding with 3mm drill bit into the center of C1 lateral mass, aim the screw a 10 - 15 degrees to the center ac- cording to horizontal plane. The screw fixa- tions into the C1 lateral mass are 26 – 34 mm long and 3.5 mm in diameter was then per- formed. The guiding mark to place the screw on the C2 stem was one third the length in the center of C2 joint block. The screw was then directed to the inner, upper edge of C2 arch, and thereafter was aimed 15 -20 degrees to center and upwards 20 degrees. The fixation JMR 116 E3 (7) - 2018 55 JOURNAL OF MEDICAL RESEARCH rod for the C1 - C2 was then placed. The outer section of the C1 and C2 posterior arches were then grinded and grafted by part of the C3 spondylosis. Muscles are then grafted into the spondylosis behind the C2. Closure of the skin by sutures. 3. Research ethics The research protocol was conformed to the Helsinki Declaration and all the interviews have been conducted with the consent form sent to the study subjects or to their parents if they were under 17 years old at the point of being interviewed. Respondents had the right to refuse answering questions that they did not want to answer and stop at anytime they wanted. III. RESULTS The average age of patients was 35.2 years old; the youngest patient was 15 years old while the oldest was 75 years old. There were 18 male and 2 female patients who par- ticipated in the study. The primary causes for fractured odontoid were traffic accidents and falls. Among 20 study patients, traffic accidents accounted for 8 and falls accounted for 12. Table 1. Clinical signs Clinical signs Cases number Ratio % High neck pain 18 90% Sensory disorder 10 50% Circular muscle disorder 2 10% Quadriplegia 1 5% According to the Anderson and D’Alonzo classification, all 20 study participants had type 2 odontoid fracture. Result from Table 1 shows that 18 patients (90%) had neck pain, 10 patients (50%) reported numbness on both hands and 2 (10%) patients had post-traumatic circular muscle disorder. There was only 1 patient who has quadriplegia, MRI showed spinal stenosis correspond- ing to the injury but no obtrusion to the artery. The C1 lateral mass and the C2 pedicle screw fixation had been, as indicated by comparing pre- and postoperative images, successfully performed in all patients. There were no cases of vertebral artery injury or other complications during operation. Mending was performed relatively easily. Two patients with sensory disorder and circular muscle disorder were required to decom- press C1 posterior arc, MRI revealed compressed muscles caused by dislocated C1 - C2. After the surgery, 18 patients had reported fewer bouts of neck pain as well as hand numbness. Ninety percent of them report no circular muscle disorder post-operation. One patient who had quadriple- gia due to compressed C2 - C3 spinal cord are able to walk again after 1 year undergoing surgery but have not completely recovered with numbness in both hands still occurred. 56 JMR 116 E3 (7) - 2018 JOURNAL OF MEDICAL RESEARCH Pre-surgery images Post surgery images a. Odotoid/ dens fracture pre-surgery images b. Post surgery images of C1 lateral mass screw fixation c. Images of vertebral arteries d. Image of post C1 and C2 screw fixation e. Images of posterior C2 spinous process fracture f. Post screw fixation image of C1 and C2 Figure 1. Pre and post surgery images JMR 116 E3 (7) - 2018 57 JOURNAL OF MEDICAL RESEARCH Case illustration A 33-year-old male patient was the victim of a road accident with his head and neck bump against the road. After falling, he remained conscious but with severe neck pain, exacerbated by movement. With neck movement restrained, CT scan of the neck spine showed C2 odontoid process fracture type II. The patient was scanned by 64-slide CT scanner to determine the anatomical structure of the C1 - C2 vertebral body, the C1 lateral mass, examine the size of the pedicle of C2, and the vertebral artery location when passing C2 and C1. Surgerical Technique: Endotracheal anes- thesia with the posture of lying in the prone position. The head was fixed on May-Few frame. Incision of skin was along the posterior interspinous line from the point under the outer occiput to the C5, C6 spinous process. Dis- section of the muscle mass beside the bilat- eral spinal spinosity under the periosteum to the outer edge of joint C2 - C3. Dissection be- neath the periosteum, above C1 posterior arch to both sides to see the C1 lateral mass. The inner edge of C1 lateral mass was palpable. The vertebral artery was in the artery groove above the C1 posterior arch. Normally, C2 radicle is located from lateral mass to the C1 posterior arch. After protecting the vertebral artery and C2 radicle, high-speed grinding drills with a 3-mm bit were used in the middle of C1 lateral mass to screw toward the center crossing horizontal plane made the angle of 10 degrees. After Taro set screw 34mm long, diameter 3.5 mm into the C1 lateral mass. The point to place the screw through the C2 pedi- cle was in the middle of the upper one third of the C2 pedicle. Placing the screw on the inner upper edge of the C2 pedicle, direct toward the center at an angle of 20 degrees and upward of 20 de- grees. Set fixed rod to join C1 - C2. The corti- cal bone in the outermost of arcs C1 and C2 was crusted and transplanted by bone of C3 posterior spinosity. The tendon was stitched into C2 posterior spinosity. Close the skin ac- cording to the anatomical layers. Postoperative patient was given antibiotics, , then could sit up and exercise early, thread cut and discharged from the hospital 15 days after the surgery. IV. DISCUSSION Surgical treatment for C2 odontoid process fracture has many different methods. In gen- eral, there are two main types of surgery: fron- tal way surgery and posterior way surgery Frontal way surgery by screwing through the odontoid apophysis was first performed by Bohler [7; 8]. This technique directly fixes the fracture, strengthens the spine of the neck, preserves the rotation of C1C2. Bone weld rate is about 90%. But this technique is difficult to perform when odontoid process fractures involve severe C1C2 dislocations. Posterior way surgery to harden C1C2 also has many different methods such as lateral mass screwing surgery C1 and the C2 pedicle that has many advantages. In 2002, Author Goel reported 160 cases that were operated with splint screw at C1 lateral mass and C2 pedicle; no patient then had neurological and vascular complications [9]. In 2001, Harms and Melcher reported 37 cases of screwing C1 lateral mass and C2 pedicle that also resulted in 100% bone and no vascular and neurologic complication [6]. In 2010, Mummaneni studied 42 cases of C1 lateral mass screwing showing 58 JMR 116 E3 (7) - 2018 JOURNAL OF MEDICAL RESEARCH high bone weld rate, reduced neck pain and improved neurological function [4]. Regarding to determining the bolt point on C1 lateral mass, there are many different views: The authors Harms and Goel screwed directly to the mass under posterior arch C1 after rolling up the C2 radicle downward [1]. Tan, Wang and associates screwed on C1 to the lateral mass for good results. In this case, we screwed directly on C1 posterior arch and found many advantages: there is no need to roll up C2 radicle, the screw was quite firm because the part of screw in the bone was long, which was favorable for C1C2 dislocation treatment. However, the bolt point was just on the posterior arch, near the vertebral artery groove, thus, vertebral artery is vulnerable [10]. Therefore, according to us, understanding of the path of the vertebral artery before the surgery by using 64-slide construction scan would help to avoid this complication. Through the study, we found that preoperative screening was of paramount importance. Patients are required to have a 64 -slide construction scan to determine the anatomy of the path of lateral vertebral artery because, according to the literature, 15 to 20% of patients have abnormalities of anatomical vertebral artery. We met a case of odontoid process fracture type II, 64-slide construction scan showed abnormality of the path of left vertebral artery that went over the posterior anterior facet of C1 lateral mass. In that case, we had to use the surgical method of screwing through the C1C2 joint and the patient also had surgery successfully. Vertebral arterial abnormality image It is important to take 64-slide scan to have anatomical determination of the size of the C2 pedicle, because if the C2 pedicle were too small, this technique could not be applied. During surgery, continuously use C-Arm 3D to well control the path of the screw to reduce the risk of injury to vertebral artery and spinal cord. Figure 2. Vertebral arterial abnormality image V. CONLUSION Screwing surgery through C1 lateral mass and C2 pedicle should be applied to patient with sprained C1C2, odontoid process fracture type II as it results in high bone weld rate, firm fix but keeping ability to exercise cervical spine after surgery and it’s safe. However, it is needed to carry out preoperative examination thoroughly together with modern medical equipment, and it needs high accuracy and surgeon’s experiences. ACKNOWLEDGEMENTS We highly appreciate the Phu Tho provin- cial general hospital for providing the data, allowing and supporting us to perform our re- search. We would like to thank Department of Biostatistic and Health Informatic, Hanoi Medi- cal University for technical assistance and ed- iting the manuscript. JMR 116 E3 (7) - 2018 59 JOURNAL OF MEDICAL RESEARCH REFERENCES 1. Aryan HE., Newman CB., Acosta FL (2008). 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