Clinical application of a revised screw technique via the C1 posterior arch and lateral mass in the pediatric population

Analysis of Risk Factors for Posterior C1 Screw-Related Complication: A Retrospective Study of 358 Posterior C1 Screws

BACKGROUND

Although C1 screw fixation is becoming popular, only a few studies have discussed about the risk factors and the patterns of C1 screw complications.

OBJECTIVE

To investigate the incidence of C1 screw complications and analyze the risk factors of the C1 screw complications.

METHODS

A total of 358 C1 screws in 180 consecutive patients were analyzed for C1 screw complications. Screw malposition, occipital neuralgia, major complications, and total C1 screw complications were analyzed.

RESULTS

The distribution of C1 screw entry point is as follows: inferior lateral mass, 317 screws (88.5 %); posterior arch (PA), 38 screws (10.7 %); and superior lateral mass, 3 screws (0.8 %). We sacrificed the C2 root for 127 screws (35.5 %). C1 instrumentation induced 3.1 % screw malposition, 6.4 % occipital neuralgia, 0.6 % vascular injury, and 3.4 % major complications. In multivariate analysis, deformity (odds ratio [OR]: 2.10, P = .003), traumatic pathology (OR: 4.97, P = .001), and PA entry point (OR: 3.38, P = .001) are independent factors of C1 screw malposition. C2 root resection can decrease the incidence of C1 screw malposition (OR: 0.38, P = .012), but it is a risk factor of occipital neuralgia (OR: 2.62, P = .034). Advanced surgical experience (OR: 0.09, P = .020) correlated with less major complication.

CONCLUSION

The incidence of C1 screw complications might not be uncommon, and deformity or traumatic pathology and PA entry point could be the risk factors to total C1 screw complications. The PA screw induces more malposition, but less occipital neuralgia. C2 root resection can reduce screw malposition, but increases occipital neuralgia.

C2 Pedicle Screws Combined With C1 Laminar Hooks for Reducible Atlantoaxial Dislocation: An Ideal Salvage Technique for C1-C2 Pedicle Screws

BACKGROUND

A C1 laminar hook can theoretically avoid vertebral artery injury and is less technically demanding. However, only few studies with small samples analyzed the short-term outcomes of C2 pedicle screws combined with C1 laminar hooks (C2PS-C1LH) technique in the treatment of atlantoaxial dislocation. Furthermore, it is not confirmed whether similar clinical outcomes can be achieved with C1-C2 pedicle screw and rod construct (PSRC).

OBJECTIVE

To evaluate the outcomes of C2PS-C1LH and C1-C2 PSRC fixation techniques for treating atlantoaxial dislocation.

METHODS

Data of 52 patients with atlantoaxial dislocation treated by C1-C2 PSRC or C2PS-C1LH fixation were retrospectively reviewed. Outcomes evaluated by visual analog scale score for neck pain (VASSNP), Neck Disability Index (NDI), atlantodental interval (ADI), and the perioperative parameters including blood loss and operation time were analyzed and compared between 2 techniques. Patient satisfaction at final follow-up was also investigated.

RESULTS

There were no complications related to the surgical approach and instrumentation in either group. The mean bone fusion time was 5.06 ± 1.65 mo for the C2PS-C1LH group and 3.93 ± 0.99 mo for the C1-C2 PSRC group (P > .05). Hundred percent of fusion rates were achieved in both groups at month 12 after operation. The ADI, VAS scores, the NDI scores, and the JOA scores were greatly improved in both the groups (P < .05), but there were no significant differences between the 2 groups.

CONCLUSION

C2PS-C1LH fixation technique was comparable to C1-C2 PSRC in the treatment of reducible atlantoaxial dislocation. C2PS-C1LH fixation was an ideal alternative strategy to C1-C2 PSRC fixation.

Efficacy and Safety of Atlantoaxial Fluoroscopy-guided Pedicle Screw Fixation in Patients Younger Than 12 Years: A Radiographic and Clinical Assessment

STUDY DESIGN

A retrospective clinical study.

OBJECTIVE

The aim of this study was to evaluate the efficacy and safety of fluoroscopy-guided atlantoaxial pedicle screw fixation in patients younger than 12 years.

SUMMARY OF BACKGROUND DATA

C1-C2 pedicle screw fixation is a widely accepted treatment method for atlantoaxial dislocation (AAD). However, data regarding its use for atlantoaxial fusion (AAF) in children are limited.

METHODS

Thirty-six consecutive patients younger than 12 years underwent C1-C2 pedicle screw fixation for AAD between 2007 and 2017. Anatomical parameters of the C1 pedicle were measured on preoperative computed tomography (CT). Accuracy of pedicle screw fixation was assessed on postoperative CT using the following definitions: Type I, screw threads completely within the bone; Type II, less than half the diameter of the screw violating the surrounding cortex; and Type III, clear violation of the transverse foramen or spinal canal. Demographic, surgical, radiation dose, and clinical data were recorded.

RESULTS

Patients underwent 144 screw fixations (67 C1 pedicle screws, 68 C2 pedicle screws, 5 C1 lateral mass screws, and 4 C-2 laminar screws) for a variety of pediatric AADs, with 36.5 ± 8.5 months of follow-up. Among the 135 pedicle screws, 96.3% were deemed "safe" (Type I or II) and 80.7% (109/135) of the screws were rated as being ideal (Type I); five screws (3.7%) were identified as unacceptable (Type III). Average estimated blood loss (EBL) was 92 mL, and the average total radiation exposure during the operation was 6.2 mGy (in the final 26 cases). There were no neurovascular injuries. All patients showed radiographic stability and symptom resolution.

CONCLUSION

C1-C2 pedicle screw fixation under fluoroscopy is safe and effective for the treatment of AAD in children younger than 12 years. However, it may be technically challenging owing to the special anatomical features of children and should be performed by experienced surgeons.

LEVEL OF EVIDENCE

3.

Endoscopic transnasal anterior release and posterior reduction without odontoidectomy for irreducible atlantoaxial dislocation

Background

To investigate the efficacy and safety of endoscopic transnasal anterior release and posterior reduction without odontoidectomy to treat irreducible atlantoaxial dislocation (IAAD).

Methods

A series of 9 patients with IAAD underwent endoscopic transnasal anterior release and posterior reduction without odontoidectomy. Etiology, instrumentation, fusion rate, and complications were documented. All patients were assessed clinically and radiologically for neurological recovery using the Japanese Orthopedic Association (JOA) score, atlantodontoid interval (ADI), and cervicomedullary angle (CMA).

Results

The mean age of the patients was 41.6 years, ranging from 14 to 60 years. Pathology showed os odontoideum in 3 patients, old traumatic dens fracture in 3 patients, occipitalization of C1 in 2 patients, and rheumatoid arthritis in 1 patient. Seven patients underwent C1–C2 pedicle screw fixations, and 2 patients required occipitocervical fixation. Eight cases resulted in complete reduction and 1 in partial reduction. Complications included one superficial infection related to the posterior approach. All patients were followed up for an average of 17 (range 13–32) months. Bony fusion was confirmed in all cases under radiologic assessment at 1 year postoperatively, and the bony fusion rate reached 100%. Moreover, no instrumental failure occurred during the entire follow-up period. The JOA score improved from 7.21 ± 1.62 to 12.28 ± 0.81 at the last follow-up. The ADI of 9 cases was 7.06 ± 0.85 mm preoperatively, which decreased to 2.26 ± 0.56 mm at the final follow-up. CMA improved from 103.80° ± 4.16° to 143.23° ± 7.47° postoperatively.

Conclusion

With transnasal approach and lack of odontoidectomy, this method could not only treat IAAD safely and effectively, but also reduce the possibility of many complications associated with the traditional transoral approach and odontoidectomy.

Long-Term Clinical and Radiologic Postoperative Outcomes After C1-C2 Pedicle Screw Techniques for Pediatric Atlantoaxial Rotatory Dislocation

BACKGROUND

Although C1-C2 pedicle screw techniques have been extensively reported in pediatric series, reports on their use have examined only small series with short follow-up periods. The aim of this study was to report pediatric patients with atlantoaxial rotatory dislocation treated with these techniques with a minimum 5-year follow-up.

METHODS

Retrospective review was performed of 27 pediatric patients with atlantoaxial rotatory dislocation who underwent C1-C2 pedicle screw fixation between 2004 and 2012. Clinical and radiographic outcomes were collected and compared with a control group.

RESULTS

Follow-up period was 60-142 months (mean 84 months). Torticollis was completely corrected postoperatively in all but 1 patient. All patients experienced significant pain relief and improvement in range of motion, and 6 patients with neurologic deficits experienced significant improvement postoperatively. Both atlantodental interval and space available for the cord were significantly improved compared with preoperative values. At final follow-up, curvature was lordotic in 20 cases and straight in 7 cases. Compared with the control group, range of motion of the patient group was not significantly different in any direction except in flexion and rotation. Mean anteroposterior diameters of the spinal canal at C1 and C2 levels were not significantly different from the control group.

CONCLUSIONS

C1-C2 pedicle screw techniques are safe and effective for treatment of atlantoaxial rotatory dislocation and result in no obvious limitation on growth in older children.

Long-Term Influence of C1-C2 Pedicle Screw Fixation on Occipitoatlantal Angle and Subaxial Cervical Spine in the Pediatric Population

OBJECTIVE

The goal of this study was to evaluate the impact of C1-C2 pedicle screw fixation on the occipitoatlantal angle and subaxial cervical spine for a pediatric population, and the clinical efficacy and adjacent-segment degeneration after C1-C2 pedicle screw fixation with a minimum of 2 years of follow-up.

METHODS

Twenty-two pediatric patients with atlantoaxial dislocation who were enrolled in this study underwent atlantoaxial pedicle screw fixation. The correlation between C0-C1, C2-C7, and C1-C2 pre- and postoperative sagittal angles was assessed using plain radiographs, and adjacent-segment degeneration (ASD) and JOA scores (Japanese Orthopaedic Association scores) were evaluated after atlantoaxial pedicle screw fixation.

RESULTS

The C1-C2 angle increased from 16.1 ± 13.37 to 28.1 ± 5.1° (p < 0.01). The pre- and postoperative C1-C2 angles were negatively correlated with the pre- and postoperative C0-C1 and C2-C7 angles, respectively. In accordance with the optimal atlantoaxial fusion angle (25-30°) obtained from the literature, postoperative JOA scores were greater in the groups with angles of more than 30° and less than 25°, although the difference in ASD was not statistically significant. Postoperative JOA scores were not relevant to the postoperative C1-C2 angle; however, there was a positive correlation between JOA improvement rate and the change of the C1-C2 angle postoperatively.

CONCLUSION

Atlantoaxial pedicle screw fixation can be used easily to reduce atlantoaxial dislocation in the pediatric population; however, outside the range of the optimal atlantoaxial fusion angle it can change the occipitoatlantal angle and subaxial alignment, which induces ASD and influences the clinical efficacy. It is necessary to achieve an optimal atlantoaxial angle when using atlantoaxial pedicle screw fixation.

Structural Allograft versus Autograft for Instrumented Atlantoaxial Fusions in Pediatric Patients: Radiologic and Clinical Outcomes in Series of 32 Patients

BACKGROUND

Allograft with wire techniques showed a low fusion rate in pediatric atlantoaxial fusions (AAFs) in early studies. Using allograft in pediatric AAFs with screw/rod constructs has not been reported. Thus we compared the fusion rate and clinical outcomes in pediatric patients who underwent AAFs with screw/rod constructs using either a structural autograft or allograft.

METHODS

Pediatric patients (aged ≤12 years) who underwent AAFs between 2007 and 2015 were retrospectively evaluated. Patients were divided into 2 groups (allograft or autograft). Clinical and radiographic results were collected from hospital records and compared.

RESULTS

A total of 32 patients were included (18 allograft, 14 autograft). There were no significant group differences in age, sex, weight, diagnosis, or duration of follow-up. A similar fusion rate was achieved (allograft: 94%, 17/18; autograft: 100%, 14/14); however, the average fusion time was 3 months longer in the allograft group. Blood loss was significantly lower in the allograft group (68 ± 8.5 mL) than the autograft group (116 ± 12.5 mL). Operating time and length of hospitalization were slightly (nonsignificantly) shorter for the allograft group. A significantly higher overall incidence of surgery-related complications was seen in the autograft group, including a 16.7% (2/14) rate of donor-site-related complications.

CONCLUSIONS

The use of allograft for AAF was safe and efficacious when combined with rigid screw/rod constructs in pediatric patients, with a similar fusion rate to autografts and an acceptable complication rate. Furthermore, blood loss was less when using allograft and donor-site morbidity was eliminated; however, the fusion time was increased.

Unilateral lag-screw technique for an isolated anterior 1/4 atlas fracture

STUDY DESIGN

Fractures of the atlas are classified based on the fracture location and associated ligamentous injury. Among patients with atlas fractures treated using external immobilization, nonunion of the fracture could be seen.

OBJECTIVE

Ideally, treatment strategy for an unstable atlas fracture would involve limited fixation to maintain the fracture fragments in a reduced position without restricting the range of motion (ROM) of the atlantoaxial and atlantooccipital joints.

SUMMARY OF BACKGROUND DATA

Such a result can be established using either transoral limited internal fixation or limited posterior lateral mass fixation. However, due to high infection risk and technical difficulty, posterior approaches are preferred but none of these techniques can fully address anterior 1/4 atlas fractures such as in this case.

MATERIALS AND METHODS

A novel open and direct technique in which a unilateral lag screw was placed to reduce and stabilize a progressively widening isolated right-sided anterior 1/4 single fracture of C1 that was initially treated with a rigid cervical collar is described.

RESULTS

Radiological studies made after the surgery showed no implant failure, good cervical alignment, and good reduction with fusion of C1.

CONCLUSIONS

It is suggested that isolated C1 fractures can be surgically reduced and immobilized using a lateral compression screw to allow union and maintain both C1-0 and C1-2 motions, and in our knowledge this is the first description of the use of a lag screw to achieve reduction of distracted anterior 1/4 fracture fragments of the C1 from a posterior approach. This technique has the potential to become a valuable adjunct to the surgeon's armamentarium, in our opinion, only for fractures with distracted or comminuted fragments whose alignment would not be expected to significantly change with classical lateral mass screw reduction.

Computed Tomographic Morphometric Analysis of Pediatric C1 Posterior Arch Crossing Screw Fixation for Atlantoaxial Instability

STUDY DESIGN

A CT-based study of pediatric atlas.

OBJECTIVE

The aim of this study was to identify morphometric patterns and dimensions of the pediatric C1 posterior arch to establish guidelines for the posterior arch crossing screw (PACS) fixation.

SUMMARY OF BACKGROUND DATA

The PACS fixation is an alternative or supplement to the C1 lateral mass screw or pedicle screw constructs. However, the anatomic feasibility of this technique has not been well documented in the pediatric population.

METHODS

A total of 123 pediatric patients were assigned into 6 groups based on age at an interval of 3 years. The C1 posterior arch unsuited to PACS fixation was classified as type 1 with synchondrosis, and type 2 without synchondrosis. Three subtypes of type 2 were included: the underdeveloped tubercle, the flat arch, and the undersized tubercle (height < 7 mm or width < 3.5 mm), respectively. The C1 posterior tubercle height and arch width, the projected PACS length and angle were measured, respectively.

RESULTS

There were 19 patients of type 1 and 68 patients of type 2. Type 1 was mostly found in patients under age 3 years, whereas type 2 was largely observed in patients older than 4 years. The tubercle size was the most limiting variable for successful PACS placement. The PACS fixation was feasible for 42% patients over age 7 years and only 5% patients under age 6 years. The posterior tubercle height increased with age, whereas the tubercle width, the PACS length, and axial-plane angle increased with age up to 12 years. The PACS length was between 16 and 18 mm with the angle between 18° and 23° for patients over age 7 years.

CONCLUSION

The PACS fixation was anatomically feasible in patients over age 7 years, but contraindicated in patients under age 6 years. Pediatric patients for the PACS fixation should be assessed before surgery.

LEVEL OF EVIDENCE

4.

Posterior atlantoaxial fixation: a review of all techniques

BACKGROUND CONTEXT

Posterior atlantoaxial fixation is an effective treatment for atlantoaxial instability. Great advancements on posterior atlantoaxial fixation techniques have been made in the past decades. However, there is no article reviewing all the posterior atlantoaxial fixation techniques yet.

PURPOSE

The aim was to review the evolution and advancements of posterior atlantoaxial fixation.

STUDY DESIGN

This was a literature review.

METHODS

The application of all posterior fixation techniques in atlantoaxial stabilization, including wiring techniques, interlaminar clamp fixation, transarticular fixation, screw-plate systems, screw-rod systems, and hook-screw systems, are reviewed and discussed. Recent advancements on the novel technique of atlantoaxial fixation are described. The combination of the C1 and C2 screws in screw-rod systems are described in detail.

RESULTS

All fixation techniques are useful. The screw-rod system appears to be the most popular approach. However, many novel or modified fixation methods have been introduced in recent years.

CONCLUSIONS

Great advancements on posterior atlantoaxial fixation techniques have been made in the past decades. The wiring technique and interlaminar clamps technique have fallen out of favor because of the development of newer and superior fixation techniques. The C1-C2 transarticular screw technique may remain the gold standard for atlantoaxial fusion, whereas screw-rod systems, especially the C1 pedicle screw combined with C2 pedicle/pars screw fixation, have become the most popular fixation techniques. Hook-screw systems are alternatives for atlantoaxial fixation.