Occipitocervical Fusion: An Updated Review

Multirod posterior occipitocervical instrumentation constructs: a biomechanical analysis and initial case series of 10 patients with complex craniocervical pathology

BACKGROUND CONTEXT

Stabilization of the occipitocervical (OC) junction with posterior instrumentation plays a vital role in addressing a spectrum of pathologies. Due to limited bone surfaces of the occiput and C1 lamina, achieving union across the OC junction is challenging.

PURPOSE

To explore the biomechanics and a clinical series of patients treated with multirod constructs across the OC junction using a novel occipital plate with single- and dual-headed, modular tulip heads.

STUDY DESIGN/SETTING

Biomechanical analysis and retrospective case series.

PATIENT SAMPLE

Adults at a single institution who underwent posterior cervical multirod constructs across the OC junction.

OUTCOME MEASURES

OC-C4 range of motion (ROM), maximum von Mises stress on the rods, and adjacent segment ROMs and intradiscal parameters. Patient demographics, revision operations, rod breakages, wound complications.

METHODS

A validated occiput-cervical finite element (FE) model was used to simulate OC-C4 cervical fixation under multidirectional pure moment loading. A total of 4 rod configurations were simulated: (A) 2-rod-Ti (4.0 mm titanium rods); (B) 2-rod-CoCr (3.5 mm cobalt chrome rods); (C) 3-rods (4.0 mm titanium rods); (D) 4-rods (4.0 mm titanium rods). The aforementioned measures were compared. A retrospective analysis was also performed of adults at a single institution who underwent posterior cervical multirod constructs across the OC junction.

RESULTS

Biomechanically, lowest primary rod stresses were observed for 3- and 4-rod constructs. Compared to 2-rod-Ti (121.8 MPa), 2-rod-CoCr showed a 43.2% stress increase in the rods, while 3- and 4-rods experienced rod stress reductions of 20% and 23.2%, respectively. No appreciable differences in OC-C4 ROM, C4-5 ROM, and C4-5 discal stresses were found between multirod and 2-rod constructs. Maximum occipital and C4 screw stresses were decreased in multirod constructs compared to 2-rods, with least stresses noted in the 4-rod construct. Maximum plate stresses were slightly increased in the 4-rod construct compared to 2- and 3-rod fixation, though the forces were largely similar among the constructs. Ten patients (average age 66.4±10.6 years; 8 males) were assessed clinically. Nine of the ten operations were for primary stabilization of pathological fractures and associated craniocervical and/or atlantoaxial instability using 4-rods across the OC junction. At an average follow-up time of 1.58±0.5 years (range, 1-2.3 years), there were no instrumentation failures, no adjacent segment failures, and no wound complications.

CONCLUSIONS

In this proof-of-concept investigation, multiple rods (3- and 4-rods) across the OC junction using a novel occipital plate with single- and dual-headed, modular tulips was safe and effective in stabilizing the OC junction. Accompanying FE analysis demonstrated that multirod constructs decreased primary rod stresses and had lower stresses on occipital and C4 screws compared to 2-rod constructs, while occipital plate stresses were largely similar. Additional clinical studies are needed to confirm these findings and to determine the ultimate utility of multirod constructs across the OC junction.

Endoscopic Endonasal Occipitocervical Fixation with a Customized Three-Dimensional Printed Titanium Plate-Screw Construct: A Cadaveric Feasibility Study

OBJECTIVE

To evaluate the feasibility of a novel method for occipitocervical fixation (OCF) through the endonasal corridor.

METHODS

Thin-cut computed tomography scans were obtained for 5 cadaveric specimens. Image segmentation was used to reconstruct 3D models of each O-C1 joint complex. Using computer-aided design software, plates were custom-designed to span each O-C1 joint, sit flush onto the bony surface, and accommodate screws. The final models were 3D-printed in titanium. For implantation, specimens were held in pin-fixation and registered to neuronavigation. A rigid 0º endoscope was used for endonasal visualization. An inverted U-shaped nasopharyngeal flap was raised to expose the occipital condyles and C1. The plates were introduced and fixed with bone screws. Computed tomography scans were obtained to assess screw accuracy and proximity to critical neurovascular structures. Screw entry points and trajectories were recorded.

RESULTS

Endonasal OCF was performed on 5 cadaveric specimens. The mean starting point for occipital condyle screws was 6.17 mm lateral and 5.38 mm rostral to the medial O-C1 joint. Mean axial and sagittal trajectories were 7.98° and 6.71°, respectively. The mean starting point for C1 screws was 16.11 mm lateral to the C1 anterior tubercle and 6.39 mm caudal to the medial O-C1 joint. Mean axial and sagittal trajectories were 10.97° and -9.91°, respectively.

CONCLUSIONS

Endonasal OCF is technically and anatomically feasible. The application of this technique may allow for same-stage endonasal decompression and fixation, offering a minimally invasive alternative to current methods of fixation and advancing surgeons' ability to treat pathology of the craniovertebral junction. Next steps will focus on biomechanical testing.

Technical note: Traumatic atlanto-occipital dislocation and severe subaxial cervical distraction injury in an infant

INTRODUCTION

Traumatic injuries of the spine requiring surgery are rare in infancy. Fusion procedures in the very young are not well-described at the atlanto-occipital junction or subaxial spine. Here we describe novel segmental posterior instrumentation in a severe spinal column disruption in an infant.

CASE PRESENTATION

A 13-month-old male with atlanto-occipital dislocation and severe C6-7 distraction (ASIA impairment scale A) presented after a motor vehicle accident. He underwent instrumented fusion (occiput-C2 and C6-7) and halo placement. Postoperative imaging demonstrated reduction of the C6-7 vertebral bodies. Physical examination showed lower limb paraplegia and preserved upper extremity strength except for mild weakness in hand grip (3/5 on the MRC grading scale). Occiput-C2 instrumentation was performed using occipital keel and C2 pedicle screws with sublaminar C1 polyester tape. C6-7 reduction and fixation was performed with laminar hooks. Arthrodesis was promoted with lineage-committed cellular bone matrix allograft and suboccipital autograft. Anterior column stabilization was deferred secondary to a CSF leak. Intraoperative monitoring was performed throughout the procedure. Within 1 month after surgery the patient was able to manipulate objects against gravity. CT imaging revealed bony fusion and spontaneous reduction of C6-7.

DISCUSSION

Spinal instrumentation is technically challenging in infants, regardless of injury mechanism, particularly in cases with complete spinal column disruption, but an anterior fusion may be avoided in infants and small children with posterior stabilization and halo placement.

Surgical treatment of craniocervical instability: comparison of two constructs regarding clinical and radiological outcomes of 100 patients

PURPOSE

There is an increased demand for surgical solutions to treat craniocervical instability. This retrospective study demonstrates the clinical and radiological outcomes of unstable craniocervical junction treated with occipitocervical fusion.

MATERIAL AND METHODS

The mean age of 52 females and 48 males was 56.89 years. The clinical and radiological outcomes were assessed, including NDI, VAS, ASIA score, imaging, complications and bony fusion in two used constructs: a modern occipital plate-rod-screw system (n = 59) and previous bilateral contoured titanium reconstruction plates-screws (n = 41).

RESULTS

Clinically and on imaging, patients presented with neck pain, myelopathy, radiculopathy, vascular symptoms and craniocervical instability. The mean follow-up was 6.47 years. A solid bony fusion was achieved in 93.81% of the patients. The NDI and the VAS improved significantly from 28.3 and 7.67 at the presentation to 16.2 and 3.47 at the final follow-up. The anterior and posterior atlantodental interval (AADI and PADI), the clivus canal angle (CCA), the occipitoaxial angle (OC2A) and the posterior occipitocervical angle (POCA) improved significantly. Six patients required early revision.

CONCLUSION

Occipitocervical fusion can yield excellent results regarding clinical improvement and long-term stability with a high fusion rate. Simple reconstruction plates, though more demanding surgically, achieve similar results. Preserving a neutral patient's position for fixation avoids postoperative dysphagia and may help prevent adjacent segment disease development.

Endoscopic odontoidectomy for brainstem compression in association with posterior fossa decompression and occipitocervical fusion

OBJECTIVE

Endonasal endoscopic odontoidectomy (EEO) is an alternative to transoral surgery for symptomatic ventral compression of the anterior cervicomedullary junction (CMJ), allowing for earlier extubation and feeding. Because the procedure destabilizes the C1-2 ligamentous complex, posterior cervical fusion is often performed concomitantly. The authors' institutional experience was reviewed to describe the indications, outcomes, and complications in a large series of EEO surgical procedures in which EEO was combined with posterior decompression and fusion.

METHODS

A consecutive, prospective series of patients who underwent EEO between 2011 and 2021 was studied. Demographic and outcome metrics, radiographic parameters, extent of ventral compression, extent of dens removal, and increase in CSF space ventral to the brainstem were measured on the preoperative and postoperative scans (first and most recent scans).

RESULTS

Forty-two patients (26.2% pediatric) underwent EEO: 78.6% had basilar invagination, and 76.2% had Chiari type I malformation. The mean ± SD age was 33.6 ± 3.0 years, with a mean follow-up of 32.3 ± 4.0 months. The majority of patients (95.2%) underwent posterior decompression and fusion immediately before EEO. Two patients underwent prior fusion. There were 7 intraoperative CSF leaks but no postoperative CSF leaks. The inferior limit of decompression fell between the nasoaxial and rhinopalatine lines. The mean ± SD vertical height of dens resection was 11.98 ± 0.45 mm, equivalent to a mean ± SD resection of 74.18% ± 2.56%. The mean increase in ventral CSF space immediately postoperatively was 1.68 ± 0.17 mm (p < 0.0001), which increased to 2.75 ± 0.23 mm (p < 0.0001) at the most recent follow-up (p < 0.0001). The median (range) length of stay was 5 (2-33) days. The median time to extubation was 0 (0-3) days. The median time to oral feeding (defined as, at minimum, toleration of a clear liquid diet) was 1 (0-3) day. Symptoms improved in 97.6% of patients. Complications were rare and mostly associated with the cervical fusion portion of the combined surgical procedures.

CONCLUSIONS

EEO is safe and effective for achieving anterior CMJ decompression and is often accompanied by posterior cervical stabilization. Ventral decompression improves over time. EEO should be considered for patients with appropriate indications.

C1-C2 Rotatory Subluxation in Adults “A Narrative Review”

The atlantoaxial joint C2 (axis) with the anterior arch of C1 (atlas) allows 50% of cervical lateral rotation. It is responsible for precise and important movements that allow us to perform precise actions, both in normal and working life. Due to low incidence in adults, this condition often goes undiagnosed, or the diagnosis is delayed and the outcome is worse. An early diagnosis and treatment are essential to ensure satisfactory neurological and functional outcomes. The aim of this review is to analyze C1-C2 rotatory subluxation in adults, given its rarity. The time between injury and reduction is key, as it is directly related to prognosis and the severity of the treatment options. Due to low incidence in adults, this condition often goes undiagnosed, or the diagnosis is delayed as a lot of cases are not related to a clear trauma, with a poor prognosis just because of the late diagnosis and the outcome is worse. The correct approach and treatment of atlantoaxial dislocation requires a careful study of the radiological findings to decide the direction and plane of the dislocation, and the search for associated skeletal anomalies.

Clinical Behavior of General Practitioners for Patients who Underwent an Operative or Conservative Treatment for a Craniocervical Fracture

Craniocervical fractures are socially important pathology. They represent one-third of the fractures in the cervical region. It is typical that elderly patients suffer from low-energy traumas such as falls, while younger patients suffer from high-energy traumas such as motor vehicle accidents, sport falls and etc. Craniocervical fractures are associated with an increased risk of craniocervical instability or neurological deficit. Primary therapeutic options depend on the type of fracture. Predictors of nonunions are the displacement of fractures, patients’ age, and comorbidities. The observership of the general practitioner in the postoperative period or the period of cervical immobilization could recognize possible malpositioning of the instrumentation, nonunion of the fracture, malsanation of the wound, and possible complications in case of the external immobilization. There is a lack of information on that topic. The goal of the paper is to summarise the most common fractures of the craniocervical region, their etiology, and treatment options and to present the results of our study of patients who underwent operative treatment for craniocervical fracture(s). Mastering the details, the treatment options, and the possible complication of the fractures in the craniocervical region, general practitioners could play an important role in the treatment of patients. 

Complications of occipitocervical fixation: retrospective review of 128 patients with 5-year mean follow-up

PURPOSE

Occipitocervical fusion is necessary for many pathologies of the craniocervical junction. The anatomy of the region is unique, and fusion can cause significant morbidity. This retrospective review aims to investigate the complication rates and outcomes of occipitocervical fixation.

MATERIAL AND METHODS

This is a retrospective review of 128 patients with occipitocervical fixation operated between 1994 and 2020. The average follow-up is 63 months.

RESULTS

The indications of occipitocervical fixation were basilar invagination (53 patients; 41.4%), trauma (25 patients; 19.5%), tumor (23 patients; 18%), instability due to rheumatoid arthritis (13 patients; 10.2%), cervical deformity (7 patients; 5.5%) and os odontoideum (7 patients; 5.5%). There were six early postoperative (1st month) deaths. We observed complications in 67 patients (52%). Most common complication was implant-related (32%), followed by wound problems (23.4%), systemic and other complications (11.7%), neurologic complications (6.2%). Implants are removed in 31 patients (24%) for different reasons: deep wound infection (7), local pain and restriction of head movements (21), respiratory distress and swallowing problems (2), screw fracture and local pain (1).

CONCLUSIONS

Occipitocervical fixation has quite large number of complications and significantly restricts head movements. With the advent of our biomechanical concepts, indications should be limited, and shorter cervical fixations should be preferred.

LEVEL OF EVIDENCE

Diagnostic: individual cross-sectional studies with consistently applied reference standard and blinding.

Evaluation of an occipito-cervico fusion with a new implant design: a biomechanical study

Background

A novel implant for occipitocervical fusion consisting of a median plate with an additional hook inserting in the foramen magnum was tested. Aim of this study was to test the stability of a new implant for occipitocervical fusion against the already available and employed median plate implant without hook.

Material and method

36 rigid polyurethane foams occipital artificial bones were used. The two occipital implants, namely the occipital plate with hook (Group 1) and the one without hook (Group 2), were applied to the artificial occiput trough three occipital screws and ensured into the experimental setup trough a crossbar. The test parameters were set using the testing machine software as follows: (1) test speed: 10 mm/ min, with 25 mm/ min maximum; (2) preload: 5 N; (3) force switch-off threshold: 90% force drop from F_max. Failure force and path were recorded. Failure force is defined as the maximum reaction force under which failure occurs (F_max), while failure path is the travel path during which failure occurs (dL).

Results

Group 1 (plate with hook) showed a mean failure force of 459.3 ± 35.9 N and a mean failure path of 5.8 ± 0.3 mm Group 2 (plate without hook) showed a mean failure force of 323.9 ± 20.2 N and a mean failure path of 7.2 ± 0.4 mm. The Shapiro-Wilk test score was not significant (P >  0.1), assuming that data were normally distributed. Group 1 had a statistically significant greater F_max (+ 135.37; P >  0.0001) and less dL (− 1.52; P > 0.0001) compared to group 2.

Conclusions

Medial plates with foramen magnum hooks showed to be more stable that plates without a hook. These new implants may represent a new tool in OCJ fixation, but further studies are required to investigate their behavior in an anatomical setting.

Surgical treatment of a complex craniocervical malformation combined with posterior cranial fossa teratoma: a case report and literature review

Background

Basilar invagination (BI) with atlantoaxial dislocation (AAD) is not uncommon in patients with scoliosis, Klippel-Feil syndrome (KFS), and other bone deformities. Cases with combinations of the abovementioned dislocations and deformities with posterior cranial fossa teratoma are rare in the clinic and difficult to handle.

Case presentation

This case presents a 34-year-old woman diagnosed with atlantoaxial dislocation and posterior cranial fossa mass. After two surgeries, the posterior cranial teratoma was completely removed with satisfactory atlantoaxial reduction. The postoperative 1-year follow-up examination showed that the bone graft fusion was successful, without remaining significant dysfunction.

Conclusions

The surgical risk of irreducible atlantoaxial dislocation combined with posterior cranial fossa tumor is huge. Thus, it needs to be fully preoperatively evaluated and managed carefully in accordance with sound surgical principles.

[Biomechanical stability evaluation of the fixation technique for crossed rods consisting of occipital plate and C 2 bilateral lamina screws]

OBJECTIVE

To evaluate the stability of the fixation technique for the crossed rods consisting of occipital plate and C 2 bilateral lamina screws by biomechanical test.

METHODS

Six fresh cervical specimens were harvested and established an atlantoaxial instability model. The models were fixed with parallel rods and crossed rods after occipital plate and C 2 bilateral laminae screws were implanted. The specimens were tested in the following sequence: atlantoaxial instability model (unstable model group), under parallel rods fixation (parallel fixation group), and under crossed rods fixation (cross fixation group). The range of motion (ROM) of the C 0-2 segments were measured in flexion-extension, left/right lateral bending, and left/right axial rotation. After the test, X-ray film was taken to observe the internal fixator position.

RESULTS

The biomechanical test results showed that the ROMs in flexion-extension, left/right lateral bending, and left/right axial rotation were significantly lower in the cross fixation group and the parallel fixation group than in the unstable model group ( P<0.05). There was no significant difference between the cross fixation group and the parallel fixation group in flexion-extension and left/right lateral bending ( P>0.05). In the left/right axial rotation, the ROMs of the cross fixation group were significantly lower than those of the parallel fixation group ( P<0.05). After the test, the X-ray film showed the good internal fixator position.

CONCLUSION

The axial rotational stability of occipitocervical fusion can be further improved by crossed rods fixation when the occipital plate and C 2 bilateral lamina screws are used.

Deep surgical site infection after posterior instrumented fusion for rheumatoid upper cervical subluxation treated with antibiotic-loaded bone cement: Three case reports

INTRODUCTION

Patients with rheumatoid arthritis (RA) tend to be immunosuppressed due to RA itself and the therapeutic drugs administered. The management of surgical site infection (SSI) following upper cervical spinal instrumented fusion in RA patients is challenging; however, literature on the treatment for such conditions is scarce. We report 3 consecutive patients with RA, who developed deep SSI following upper cervical posterior fusion and were treated using antibiotic-loaded bone cement (ALBC).

PATIENT CONCERNS

All 3 patients reported in the current study experienced compression myelopathy with upper cervical spinal deformity and received prednisolone and methotrexate for controlling RA preoperatively. The patient in Case 1 underwent C1-2 posterior fusion and developed deep SSI due to methicillin-sensitive Staphylococcus aureus at 3 months postoperatively; the patient in Case 2 underwent occipito-C2 posterior fusion and developed deep SSI due to methicillin-sensitive Staphylococcus aureus at 2 weeks postoperatively; and the patient in Case 3 underwent occipito-C2 posterior instrumented fusion and laminoplasty at C3-7, and developed deep SSI due to methicillin-resistant coagulase negative staphylococci at 3 weeks postoperatively.

DIAGNOSIS

All patients developed deep staphylococcal SSI in the postoperative period.

INTERVENTIONS

All 3 patients were treated using ALBC placed on and around the instrumentation to cover them and occupy the dead space after radical open debridement.

OUTCOMES

The deep infection was resolved uneventfully after the single surgical intervention retaining spinal instrumentation. Good clinical outcomes of the initial surgery were maintained until the final follow-up without recurrence of SSI in all 3 cases.

CONCLUSION

ALBC embedding spinal instrumentation procedure can be a viable treatment for curing SSI in complex cases, such as patients with RA who undergo high cervical fusion surgeries without implant removal.

Morphometric Trajectory Analysis for Occipital Condyle Screws

Objectives

Occipitocervical fusion (OCF) is an effective treatment for instability of occipitocervical junction (OCJ). The occipital condyle screw serves as a novel surgical technique for occipitocervical fixation. However, the intraoperative procedures for the occipital condyle screw technique have relied on surgeons’ experience, so the pool of surgeons who are able to perform this surgery safely is limited. The present study aims to evaluate the feasibility and safety of the occipital condyle screw technique using human cadavers and to provide image anatomy for clinical application basis.

Methods

The scientific study comprised 10 fresh‐frozen cadaveric specimens from the anatomy department of Qingdao University. Placement of the occipital condyle screws (3.5 mm diameter and 20.0 mm length) was performed in the 10 fresh‐frozen cadaveric specimens with intact occipitocervical junctions, respectively. Occipitocervical CT was performed for all specimens and the DICOM data was obtained. Occipitocervical CT three‐dimensional (3D) reconstruction was performed for the cadavers. Morphometric analysis was performed on the bilateral occipitocervical junction of 10 cadaveric specimens based on the 3D reconstruction CT images. Detailed morphometric measurements of the 20 occipital condyles screws were conducted including the average length of the screw trajectory, inside and upper tilting angles of screws, distance to the hypoglossal canal, and to the medial wall of occipital condyle.

Results

Placement of the occipital condyle screws into the 20 occipital condyles of the 10 cadaveric specimens was performed successfully and the trajectory of implantation was satisfactory according to 3D CT reconstruction images, respectively. There was no obvious injury to the spinal cord, nerve root, and vertebral artery. The length of the bilateral screw trajectory was, respectively, 20.96 ± 0.91 mm (left) and 20.59 ± 0.77 mm (right) (t = 1.306, P > 0.05). The upper tilting angle of bilateral screws was, respectively, 11.24° ± 0.74° (left) and 11.11° ± 0.64° (right) (t = 0.681, P > 0.05). The inside tilting angle of bilateral screws was, respectively, 31.00° ± 1.32° (left) and 30.85° ± 1.27° (right) (t = 0.307, P > 0.05). The screw's distance to the bilateral hypoglossal canal was, respectively, 4.84 ± 0.54 mm (left) and 4.70 ± 0.54 mm (right) (t = 0.685, P > 0.05). The screw's distance to the medial wall of the bilateral occipital condyle was, respectively, 5.13 ± 0.77 mm (left) and 5.04 ± 0.71 mm (right) (t = 0.384, P > 0.05).

Conclusion

The occipital condyle screw technique can serve as a feasible and safe treatment for instability of the occipitocervical junction with meticulous preoperative planning of the screw entry point and direction based on individual differences. Morphometric trajectory analysis is also an effective way to evaluate the surgical procedure.