Spontaneous anterior arch fracture of the atlas following C1 laminectomy without fusion: A report of three cases and finite element analysis

Posterior arch reconstruction in cervical surgery to restore the global biomechanics of the Atlas: a technical note

The posterior arch of the atlas is usually not considered one of the main stabilizers of the cranio-cervical junction, allowing surgeons to its removal when needed with a relative certainty to preserve the stability of the atlo-axial segment. However, these considerations do not reflect the importance to examine the integrity of the posterior arch in the whole biomechanics of the atlas. Authors like Gebauer and Panjabi revealed, respectively in experimental and clinical conditions, how the atlas responds to an axial loading force, proving that the whole atlas is involved into horizontal conversion of axial forces and providing evidence supporting the preservation of the posterior arch. Other authors evaluated the risk for anterior arch fracture following C1 laminectomy. In this technical note three different techniques of posterior atlas arch reconstruction after surgical iatrogenic disruption are presented, considering both neoplastic and degenerative disease.

Floating Laminoplasty for the Treatment of Compressive Myelopathy Accompanied by C1 Posterior Ring Hypoplasia: A Technical Note and Case Series

Posterior ring hypoplasia of the atlas (C1) is not common and in most cases is found by chance without symptoms. This disorder is sometimes accompanied by a mild C1-C2 instability or the presence of a space-occupying lesion such as ossification of posterior longitudinal ligament, pannus, or retro-odontoid pseudo-tumor, which are indications for surgery if symptomatic cord compression is present. A C1 posterior arch resection has been the procedure of choice but is associated with several fatal complications. We here present a novel posterior arch decompression technique that is relatively safer and easier and that involves mobilization and posterior translation of the posterior arch as a whole, similar to a vertebral body sliding osteotomy.

Maximum Safety Limits of Laminectomy of the C1 Vertebra for Chiari Malformation Surgery: A Finite Element Analysis

Background

The treatment of Chiari malformations generally consists of posterior fossa decompression. C1 laminectomy is required in selected cases. However, cases of iatrogenic anterior arch fractures at C1 without high-energy trauma have been reported. Developing theoretical models of atlas C1 bones that have undergone a laminectomy can help researchers identify the regions where fractures may occur as a result of sudden loads.

Methods

In this study, we created a detailed three-dimensional solid finite element model of the human atlas bone (C1) using geometric data. The loadings of the laminectomy dimension were evaluated on the basis of three groups. Group I comprised atlas bones that had not undergone a laminectomy. For Group II, the lateral border of the laminectomy was determined as the projection of the lateral mass medial border on the lamina. For Group III, the bilateral sulcus arteriosus was determined as the border for the lateral border of the laminectomy. The analysis results, which are in good agreement with those of previous reports, showed high concentrations of localized stress in the anterior and posterior arches of the atlas bone.

Results

The analysis results showed that the stress increased in the laminectomy models. The maximum stress observed was consistent with the clinical observations of fracture sites in previous studies.

Conclusion

In the treatment of patients with Chiari malformations, C1 laminectomy is often required. The width of this laminectomy can lead to iatrogenic anterior arch fractures. This is the first study to evaluate C1 laminectomy width using finite element modeling.

A case of anterior arch fracture of the atlas associated with C1 laminectomy

Background

Spontaneous anterior arch fracture of the atlas after a C1 laminectomy (CIL) is an extremely rare complication.

Case Description

A 72-year-old male presented with the sudden onset of neck pain. His prior history included; a CIL for atlantoaxial subluxation, shunt closure for a spinal dural arteriovenous fistula at C3, a cervical laminoplasty from C3 to C6 for stenosis, and a prior anterior C4/5 and C5/6 fusion 14 years ago. Once the computed tomography documented a right C1 anterior arch fracture, and occipital-cervical fusion was performed utilizing C2 laminar screws and C4 pedicle screws with halo-vest placement. Postoperatively, the neck pain resolved and he remained stable.

Conclusion

Neurosurgeons should be aware of the risk of anterior arch fractures following a CIL and may alternatively consider a C1 laminoplasty in the future.

Effect of C1 Single-door Laminoplasty on Symptomatic Atlas Canal Stenosis

OBJECTIVE

To verify the effect of single-door laminoplasty combined with atlantoaxial fusion in the treatment of symptomatic atlas canal stenosis.

METHODS

This is a single-center retrospective analysis. From February 2014 to January 2019, 16 patients (five were females) with an average age of 63.4 years (56-71 years) were enrolled in this study. Patients with compressive cervical myelopathy with CT scan showed an inner sagittal diameter (ISD) of C₁ less than 29 mm or C1 canal space available for cord (SAC) of <12 mm were included, while isolated C1 stenosis without myelopathy or isolated C1 stenosis without atlantoaxial subluxation were excluded in this study. All patients underwent continuous heavy-weight skull traction, atlas single-door laminoplasty and atlantoaxial fusion. The differences in the pre- and post-operative inner sagittal diameter, space available for cord, atlas-dens interval (ADI) and compression of the spinal cord were analyzed by using CT and MRI. Functional evaluation was performed by using the Japanese Orthopaedic Association scoring system and the Neck Disability Index scoring system.

RESULTS

Single-door laminoplasty provided a full decompression for the spinal cord while retaining the whole posterior arch. No complications were encountered except a superficial wound infection in one patient. At final follow-up, The ADI was significantly reduced from 5.2 ± 1.8 mm to 1.7 ± 0.6 mm after surgery on average (P < 0.05). Average inner sagittal diameter of C1 was increased from 26.3 ± 2.6 mm to 34.9 ± 2.9 mm and the space available for cord was increased from 6 ± 1.7 mm to 17.8 ± 3.6 mm (P < 0.05). Meanwhile, the Japanese Orthopaedic Association (JOA) score of the 16 cases was improved from 11.4 ± 1.8 to 14.1 ± 1.4 on average (P < 0.05). The postoperative neck pain VAS score decreased significantly, from 2.6 ± 1.0 preoperatively to 1.3 ± 0.9 postoperatively (P < 0.05). The influence of neck pain on patient's life was improved from 17.8 ± 3.9 to 13.9 ± 3.3 after surgery (P < 0.05). At the last follow-up, the healing of the hinge fracture and the fusion between atlas and axis were observed in all patients.

CONCLUSIONS

Single-door laminoplasty combined with atlantoaxial fusion not only provides enough space for decompression but also offers intact arch for bone grafting, suggesting that it might provide a more feasible method for the correction of symptomatic atlas canal stenosis.

Anterior Atlas Fracture After C1 Laminectomy Which Was Successfully Treated by Brace Therapy: A Case Report

CASE

We report a case of a 67-year-old male patient who underwent a C1 laminectomy with laminoplasty at C2-3 because of cervical ossification of the posterior longitudinal ligament. At 6 weeks after surgery, neck pain occurred after minor trauma without neurological deterioration. Computed tomography (CT) demonstrated C1 anterior atlas fracture with a 3-mm gap. After a 3-month brace therapy using a Philadelphia collar, the patient's neck pain disappeared with complete bone union according to the CT.

CONCLUSION

Among 14 cases that were reported previously, none of the adult patients achieved bone union by brace therapy. Therefore, this is the only case report in which bone union could be achieved by brace therapy.

Radiographic and Clinical Results of C1 Laminoplasty for the Treatment of Compressive Myelopathy

Study Design

Case series.

Purpose

To evaluate the radiographic and clinical results of C1 laminoplasty without fusion.

Overview of Literature

C1 laminectomy has been the standard procedure for decompression at the C1 level. However, there have been some reports of trouble cases after C1 laminectomy. C1 laminoplasty might be superior to C1 laminectomy with regard to maintaining the original C1 anatomical shape, preventing compression from the posterior soft tissue, and ensuring an adequate bone-grafting site around the C1 posterior part if additional salvage fusion surgery is necessary afterward.

Methods

Seven patients with spinal cord compression without obvious segmental instability at the C1/2 level treated by C1 laminoplasty were included. The indication of C1 laminoplasty was same as that of C1 laminectomy. C1 laminoplasty was performed in the same way as subaxial double-door laminoplasty. The imaging findings were evaluated using X-ray, computed tomography, and magnetic resonance imaging. The clinical results were evaluated using the Japanese Orthopaedic Association (JOA) Cervical Myelopathy Evaluation Questionnaire (JOACMEQ) and JOA score. Peri- and postoperative complications were also investigated.

Results

No patient showed increased C1/2 segmental instability after the surgery. The mean pre- and postoperative JOA scores were 8.6 and 11.7, respectively. The mean recovery rate was 40.2%. The effective rate in the JOACMEQ was 50% for the cervical spine function, 33% for the upper extremity function, 50% for the lower extremity function, 17% for the bladder function, and 17% for the quality of life. No major complication that seemed to be unique to C1 laminoplasty was observed over a period of about 4 years follow-up.

Conclusions

C1 laminoplasty for patients without obvious segmental instability might be a viable alternative procedure to C1 laminectomy.

Incidence and Risk Factors of Anterior Arch Fracture of the Atlas Following C1 Laminectomy Without Fusion

STUDY DESIGN

A retrospective multicenter study.

OBJECTIVE

To identify the incidence of anterior arch fracture (AAF) of the atlas following C1 (first cervical vertebra) laminectomy without fusion, and its risk factors.

SUMMARY OF BACKGROUND DATA

C1 laminectomy without fusion is a widely accepted surgical procedure performed to decompress the spinal cord that is compromised at the C1/C2 level, but without instability. Several case series have reported spontaneous AAF following this procedure. However, the incidence of post-laminectomy AAF and its risk factors have not been studied.

METHODS

This retrospective study included patients who underwent C1 laminectomy without fusion in any of the four participating institutions between April 2002 and March 2016. The incidence of AAF following C1 laminectomy was determined, and the included patients were grouped into those who developed AAF (AAF group) and those who did not (non-AAF group). Patient demographics and radiographic parameters including subaxial cervical balance on x-ray (C2-7 sagittal vertical axis, C2-7 lordosis, C2-7 coronal cobb angle, and T1-slope), and morphology of the atlas on computed tomography (CT) scan were compared with the AAF and non-AAF groups.

RESULTS

Seventy patients who underwent C1 laminectomy without fusion were included in the study. The incidence of AAF was 14.2% (10/70). Multivariate analysis revealed that a large inferior facet angle (IFA, defined as the coronal inclination angle of the C1/2 facet as measured on CT) and the presence of subaxial ankylosis (bony ankylosis below C2 on CT) were independent risk factors for AAF. There were no significant differences in the subaxial cervical balance as measured on x-ray between the AAF and non-AAF groups (P > 0.05).

CONCLUSION

The incidence of AAF after C1 laminectomy without fusion is not uncommon. Preoperative assessment using CT may identify patients at high risk of AAF.

LEVEL OF EVIDENCE

4.