C1 Lateral Mass Screw Fixation Research Articles

Atlas Lateral Mass Screw Fixation in Atlanto-Axial Instability, Clinical Case Series

Background Data: Segmental spinal screw fixation has been used effectively for subaxial spine instability for long time. However, atlantoaxial fixation is still challenging due to complex topographical anatomy. So, sublaminar wires werefrequently used despite their complications. Unlike transarticular atlantoaxial screws which necessitate perfect reduction before insertion, C1 lateral mass screws are inserted independently of C2. Purpose: The aim of this work is to assess the safety and efficiency of C1 lateral mass screw fixation in cases with atlantoaxial instability. Study Design: A prospective clinical case study. Patients and Methods: This study was conducted in Al-Manial university hospital, Kasr Al-Aini Medical School, Cairo University, between 2008 and 2013. Ten patients underwent segmental atlantoaxial screw fixation using atlas lateral mass screws and either transpars interarticularis or transpedicular axis screws. Clinical results were evaluated by using the criteria of Japanese Orthopaedic Association Scoring System for Cervical Myelopathy (JOA score). The surgical technique, results and morbidity and mortality were assessed. Results: There were 6 females and 4 males; the average age was 30.2 ±17.5 y (range from 4y-61 years). The most common cause of atlantoaxial instability wastrauma (6 patients), followed by os odontoideum (2 patients ). The most common presentation was quadriparesis (5 patients) followed by neck pain and paresthesia. At the end of follow up (mean 8.5± 4.2 months) the average preoperative JOA score improved from 13.1±1.9 to 15.2±1.6 (P=0.005) and the average recovery rate was48.3±17.8%. Twenty screws were inserted in lateral mass of atlas successfully. The average screw length was 27.8±1.5mm (range 24-31mm). Postoperative CT scans showed the mean atlantodens interval improved from 5.4±1.9 to 1±1.4 (P=0.004), MRI showed that the mean cervico-medullary angle changed from 126.2°±9.4°to 141.1°±12.4° (P=0.005). There was no mortality or vertebral artery injury. One patient had profuse venous bleeding and one unit of blood was transfused and one patient had superficial wound infection and managed conservatively.Conclusion: C1 lateral mass screw fixation is a safe and effective method of atlantoaxial fixation with low complication rate. (2013ESJ052)

Comparative Results Between C1 pedicle screw and C1 lateral mass screw

Objective To compare the clinical outcomes of C1 pedicle screw with C1 lateral mass screw.Methods From Jan 2006 to Jan 2010,60 cases with atlantoaxial instability were randomly divided into two groups:32 cases underwent posterior C1 pedicle screw fixation (the pedicle group) and 28 cases underwent posterior C1 lateral mass screw fixation (the lateral mass group).Patients were followed up at regular intervals.The blood loss,the time of the operation,the JOA Score,VAS Score,and the bone fusion rate were recorded.Results All cases were followed up for an average of 46.6 months (range,12 to 60 months).Bone fusion were achieved 6 month after operations.There were no loose or breakage of screw-rod.Atlantoaxial re-instability was not found in the series.At the last followed up time,the JOA score and VAS score of pedicle group had respectively improved from 7.1±2.8 and 3.0±1.2 preoperatively to 13.3±2.1 and 1.8±0.9 postoperatively; The JOA score and VAS score of lateral mass group had respectively improved from 7.3±2.4 and 3.2±1.0 preoperatively to 13.0±2.6 and 1.9±1.0 postoperatively.There was no difference in JOA Score,VAS Score,and the bone fusion rate between two groups.There were significant difference in blood loss,the time of the operation.Fracture of posterior arch were observed in 2 cases in the pedicle group,and in the lateral mass group,pain and numbness of cervic-occipital region were observed in 3 cases after operation.Conclusion C1 pedicle screw fixation is less invasive and safe technique.Lateral mass screw fixation is a wise option for atlantoaxial instability. Key words: Atlas; Spinal fusion; Internal fixators; Treatment outcome

Radiographic Evaluation of the Technique for C1 Lateral Mass and C2 Pedicle Screw Fixation in Three Hundred Nineteen Cases

Retrospective radiographic study of the technique for C1 lateral mass screw (C1LMS) and C2 pedicle screw (C2PS) fixation. To evaluate (1) the accuracy of the C1LMS and C2PS placement; (2) the fusion rate between C1 and C2; (3) the risk for vertebral artery (VA) injury. C1LMS and C2PS fixation is widely used when treating atlantoaxial instability. Several authors have reported their experience focusing on the technical outcomes, with many reporting fusion rates near 100%. However, most of them are relatively small series, and many have applied only plain postoperative radiographs instead of computed tomography (CT). Thus, we feel that the accuracy of C1LMS and C2PS placement has not been fully analyzed, as well as the anatomic relationship between the VA and the screws. Between December 2000 and September 2008, the fusion status and accuracy of the screws were evaluated on the postoperative reconstructive CT of 319 patients with atlantoaxial instability. Cases with malpositioned screws underwent CT angiography or magnetic resonance angiography after surgery, to evaluate potential VA injury. C1LMS of 95.5% and C2PS of 92.8% were found to be in a "good" position. After 2007, six cases had malpositioned screws, which were all in the "out" or "down" area of the C2 pedicle. Five cases underwent CT angiography and 1 had magnetic resonance angiography to evaluate potential VA injury. No occlusion, associated aneurysm or fistula of the VA was found. All cases (100%) achieved solid fusion between C1 and C2. C1LMS of 95.5% and C2PS of 92.8% were confirmed to be in good position. None of the screws including the malpositioned caused VA injury, clinically or radiographically. The technique for C1LMS and C2PS fixation appears to be safe and effective.

Inferolateral Entry Point for C2 Pedicle Screw Fixation in High Cervical Lesions

The purpose of this retrospective study was to evaluate the efficacy and safety of atlantoaxial stabilization using a new entry point for C2 pedicle screw fixation. Data were collected from 44 patients undergoing posterior C1 lateral mass screw and C2 screw fixation. The 20 cases were approached by the Harms entry point, 21 by the inferolateral point, and three by pars screw. The new inferolateral entry point of the C2 pedicle was located about 3-5 mm medial to the lateral border of the C2 lateral mass and 5-7 mm superior to the inferior border of the C2-3 facet joint. The screw was inserted at an angle 30° to 45° toward the midline in the transverse plane and 40° to 50° cephalad in the sagittal plane. Patients received followed-up with clinical examinations, radiographs and/or CT scans. There were 28 males and 16 females. No neurological deterioration or vertebral artery injuries were observed. Five cases showed malpositioned screws (2.84%), with four of the screws showing cortical breaches of the transverse foramen. There were no clinical consequences for these five patients. One screw in the C1 lateral mass had a medial cortical breach. None of the screws were malpositioned in patients treated using the new entry point. There was a significant relationship between two group (p=0.036). Posterior C1-2 screw fixation can be performed safely using the new inferolateral entry point for C2 pedicle screw fixation for the treatment of high cervical lesions.

La maladie de Grisel treated by combined C1-2 transarticular and C1 lateral mass screw fixation

The authors describe a novel posterior approach to atlantoaxial stabilization combining C1-2 transarticular and C1 lateral mass screws with vertical connecting rods to create a strong construct with four-point fixation. They present here a case of atlanto-axial instability secondary to infection, Grisel's syndrome, necessitating instrumented stabilization after a period of close clinical and radiological observation following the initial cervical decompression and evacuation of retropharyngeal and epidural abscesses.

C1 Lateral Mass Fixation

Abstract OBJECTIVE We review our experience and technique for C1 lateral mass screw fixation. We compare the results of 3 different constructs incorporating C1 lateral mass screws: occipitocervical (OC) constructs, C1–C2 constructs, and C1 to mid/low cervical constructs. METHODS We performed a retrospective chart review of 42 consecutive patients who underwent C1 lateral mass fixation by 2 of the authors (PVM and DC). The patient population consisted of 24 men and 18 women with a mean age of 64 years. Twenty-two patients had C1–C2 constructs. Twelve patients had constructs that started at C1 and extended to the mid/low cervical spine (one extended to T1). Eight patients underwent OC fusions incorporating C1 screws (2 of which were OC-thoracic constructs). All constructs were combined either with a C2 pars screw (38 patients), C2 translaminar screw (1 patient), or C3 lateral mass screw (3 patients). No C2 pedicle screws were used. Fusion was assessed using flexion-extension x-rays in all patients and computed tomographic scans in selected cases. Clinical outcomes were assessed with preoperative and postoperative visual analog scale neck pain scores and Nurick grading. The nuances of the surgical technique are reviewed, and a surgical video is included. RESULTS Two patients (5%) were lost to follow-up. The mean follow-up for the remaining patients was 2 years. During the follow-up period, there were 4 deaths (none of which were related to the surgery). For patients with follow-up, the visual analog scale neck pain score improved a mean of 3 points after surgery (P < .001). For patients with myelopathy, the Nurick score improved by a mean of 1 grade after surgery (P < .001). The postoperative complication rate was 12%. The complication rate was 38% in OC constructs, 17% in C1 to mid/low cervical constructs, and 0% for C1–C2 construct cases. Patients with OC constructs had the statistically highest rate of complications (P < .001). Patients with C1 to mid/low cervical constructs had more complications than those with C1–C2 constructs (P < .001). Of the 42 cases, there were 3 pseudoarthroses (1 in an OC case, 1 in a C1 to midcervical construct, and 1 in a C1–C2 construct). OC constructs had the highest risk of pseudoarthrosis (13%) (P < .001). CONCLUSION Patients treated with C1 lateral mass fixation constructs have a high fusion rate, reduced neck pain, and improved neurologic function. Constructs using C1 lateral mass screws do not need to incorporate C2 pedicle screws. Constructs incorporating C1 lateral mass screws are effective when combined with C2 pars screws, C2 translaminar screws, and C3 lateral mass screws. Constructs using C1 screws are associated with a higher complication rate and a higher pseudoarthrosis rate if extended cranially to the occiput or if extended caudally below C2.

C1 Lateral Mass Anatomy

Cadaveric specimens were measured to determine appropriate placement for C1 lateral mass screws. Instrumentation guidelines were developed and used to instrument a series of cadaveric specimens. Clinical experience with C1 lateral mass fixation was reviewed to evaluate results. Postoperative computed tomographic (CT) scans were reviewed to evaluate screw placement. The cadaveric study measured the dimensions of the atlas and determined ideal trajectory for screw placement. This technique was applied clinically, and 50 cases were retrospectively reviewed for fixation difficulties, neurologic or vascular injuries, and perioperative complications. Postoperative CT scans were reviewed when available. Halo application, posterior wiring, and C1 to C2 transarticular screws have been used to stabilize the upper cervical spine. Each technique has disadvantages, and C1 lateral mass fixation recently has gained popularity as a potential alternative. Recent anatomic studies have documented the dimensions of the C1 lateral mass and its ability to accommodate screw fixation. Small clinical series have documented early success with this technique. Fifteen specimens were stripped of soft tissue and measured by using calipers and CT scans. Guidelines were formulated for C1 lateral mass screw fixation. Additional specimens with intact soft tissue were instrumented without difficulty. A clinical series was reviewed to evaluate for complications related to this technique. Postoperative CT scans were reviewed to evaluate screw placement. The C1 lateral mass safely accommodated screw fixation. Trajectory of 10 degrees medial and 22 degrees cephalad was preferred. The technique was safely applied in a series of 50 patients. Postoperative CT scans showed the ability of the surgeon to achieve the intended goals for starting point and safe trajectory. C1 lateral mass fixation is a safe alternative for upper cervical fixation with several potential advantages versus other techniques, but further clinical evaluation is warranted.

Vertebral Artery Injury During Cervical Spine Surgery

Retrospective survey. To clarify the present incidence and management of iatrogenic vertebral artery injury (VAI) during cervical spine surgery. VAI is a rare complication of cervical spine surgery, but it may be catastrophic. Anterior cervical decompression (ACD) and posterior atlantoaxial transarticular screw fixation (Magerl fixation) have been the main causes, with reported incidences of 0.3% to 0.5% and 0% to 8.2%, respectively. Popular new surgical techniques, such as cervical pedicle screw or C1 lateral mass screw fixation, also entail the potential risk of VAI. A questionnaire was sent to our affiliated hospitals requesting information regarding iatrogenic VAI during cervical spine surgery. Seven spine surgeon groups and 25 general orthopedist groups responded to the questionnaire, with a response rate of 89%. The overall incidence of VAI was 0.14% (8 cases among 5641 cervical spine surgeries). The incidence in anterior cervical decompression procedures was 0.18% and that in Magerl fixation was 1.3%. Inexperienced surgeons tended to commit VAI more frequently. One case of VAI during C1 lateral mass screw fixation was included, whereas there was no case of VAI caused by cervical pedicle screw fixation. In the case of "VAI in the screw hole," hemostasis was obtained by tamponade or screw insertion, whereas "VAI in the open space" sometimes caused uncontrollable bleeding, in which embolization eventually stopped the bleeding. There were no deaths or apparent neurologic sequelae. The incidence of VAI during cervical spine surgery from this survey was similar to or slightly less than that in the literature. Tamponade was effective in many cases, but prompt consultation with an endovascular team is recommended if the bleeding is uncontrollable. Preoperative careful evaluation of the vertebral artery seems to be most important to prevent iatrogenic VAI and to avoid postoperative neurologic sequelae.

P105. Posterior atlantoaxial stabilization: a new alternative to C1-2 transarticular screws

Abstract Purpose of study: Develop new techniques to improve safety and success of C1–C2 fusion procedures. Methods used: A standard posterior C1–C2 exposure is performed. Cross-table lateral fluoroscopy is used to guide and confirm screw trajectories. The C2 pedicle screw entry point is identified and drilled with angles 15 degrees medially and 25 degrees cephalad for pedicle cannulation. Drill depth is stopped short of the C2 transverse foramen. The C1 lateral mass screw insertion point is located beneath the posterior arch of C1 in the midposition of the lateral mass just above the C2 root. The drill is then angled 10 degrees medial to lateral and cephalad toward the anterior tubercle of C1 on lateral fluoroscopy. The C1–C2 joint is then decorticated and packed with local bone fragments. Posterior rods are contoured and connected to polyaxial screw heads, and a cross-connector is applied. of findings: This technique has been used in five cases of atlantoaxial instability at our institution during the past year. There have been no C2 nerve root or vertebral artery injuries. No construct failures have been observed during the current follow-up. Relationship between findings and existing knowledge: C1 lateral mass and C2 pedicle screw fixation offers an alternative means of atlantoaxial fusion. The technique is less demanding than C1–C2 transarticular screw placement and reduces the risk of vertebral artery injury. The linked construct is stable in flexion, extension and rotation. Laminectomy or fracture of the posterior elements does not preclude this fixation technique. We think this procedure will replace the C1–C2 transarticular screw procedure. Overall significance of findings: This new technology has the potential to supplant previous C1–C2 procedures with improved safety and success. Disclosures: Device or drug: pedicle screws. Status: approved. Conflict of interest: No conflicts.