Occipitocervical fusion: A review and current concepts

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Abstract

Occipitocervical fusion is not a routine operation and is a challenging procedure due to complex anatomy of the craniocervical junction. Its unique anatomic and biomechanical property subjects any instrumentation construct to significant stress. Instability at this region can be caused by a variety of acute and chronic conditions and subtle neurological symptoms in patients. Recognition of OC instability, followed by treatments including reduction, immobilization, and operative fixation, are the goals. Bony fusion is the ultimate goal of OC reconstruction. Several instrumented fixation systems have evolved from wire and cable techniques to plates, rods, and screws. Recently screw-rod constructs are more favored because of ease of use and superior biomechanical properties. Rigid internal fixation eliminates the need for prolonged rigid external orthotics and results in improved arthrodesis rate.

Introduction

Occipitocervical fusion (OCF) is a surgical method to provide biomechanical stability when treating various craniovertebral junction (CVJ) pathologies.1., 2., 3. These conditions include rheumatological diseases, trauma, degenerative disease processes, tumor, infection, and congenital malformation.1., 2., 3., 4. In most cases occipitocervical arthrodesis is performed by appropriate spinal instrumentation and decortication, and placement of supplemental bone graft around the decorticated bony elements of the cranium and cervical vertebra. The intent is to create a stable biomechanical environment and provide the biological requirements for osseous fusion.5 Over the years the surgical techniques for OCF have evolved with resulting in increased rate of successful arthrodesis, improved maintenance of alignment, while minimizing complications.6 The aim of this study is to describe the relevant anatomy, surgical indications, and techniques as well as pearls to prevent complications based on current available evidence.

Section snippets

Anatomy and osteology

There are 4 synovial joints in the occipitoatlantoaxial complex. This multijoint complex is the most mobile portion of the cervical spine (50% of all head and neck movements).7 The occiput–C1 motion segment makes the largest contribution to flexion (21°) and extension (3.5°), while the primary movement of the C1–C2 motion segment is axial rotation (23.3–38.8° per side).7 Patients should be informed about the substantial restrictions in the neck's range of motion following OCF (40% of total

Surgical indications and contraindications

The main indication for OCF is instability of the craniocervical junction (CCJ) due to aforementioned causes listed in.1., 2., 3., 4. Posterior internal stabilization prevents compression of the neural structures, enables correction of cervical deformity and reduces pain.13., 14., 15.,16., 17., 18. There are a few contraindications to fusion in patients with OC instability. They include patients with severe medical comorbidities or coagulation problems who are unable to tolerate general

Perioperative considerations

Lu et al. concisely described the perioperative considerations as follows: preoperatively, patients are often immobilized using a rigid collar or halo. In the operating room, intubation is typically best performed in a neutral supine position with or without the use of a fiberoptic scope. It is recommended to use somatosensory evoked potentials (SSEPs) and motor evoked potentials (MEPs) during surgery to monitor neurologic function. Baseline SSEP and MEP signal are obtained after intubation,

Operative approaches

Typically the midline skin incision extends from the inion to the lowest level to be incorporated into the fusion construct. The midline avascular plane is dissected to split the paraspinal muscles, then subperiosteal dissection of the occiput and the posterior spine elements is performed using electrocautery to minimize blood loss. Lu et al. describes the different fixation techniques as followed:

For occipital wiring, we typically place 2 small, parallel burr holes in the suboccipital bone.

Fixation techniques

Occipitocervical fusion has advanced significantly since 1927, when Foerster was the first surgeon to reported successful stabilization of the CCJ by in situ onlay application of a fibular strut graft.21,22 Others followed, using iliac crest onlay graft after decorticating the dorsal OC surface.23 These patients required long-term immobilization (12 weeks) in a halo vest or Min erva jacket. Currently there are 4 common techniques utilized for cranial fixation with OC instrumentation.

One-piece

Arthrodesis

Rigid fixation is required to promote arthrodesis. The complex anatomy of occipitocervical region requires special attention when planning arthrodesis. In addition to several mobile joints, the sharp angle at which the occiput meets the upper cervical spine creates a significant lever arm that works against surgical fixation devices.7 The bony surface of the occiput, and the posterior elements of the cervical spine (including the facet joints) should be decorticated to bleeding cancellous bone

Potential complications

The general complication rate in OCF varies from 10% to 33%.45,46 Minor complications include wound infection or dehiscence, dural tear and cerebrospinal fluid leakage. A preventable complication associated with OCF is proper head alignment. Excessive flexion results in the patient having an impaired line of sight and swallowing difficulties. Fixation in exaggerated extension results in poor visualization of the ground. Major potential complications include the vertebral artery, posterior fossa

Alternative treatments

External immobilization including prolonged immobilization in a Minerva jacket or a halo vest is rarely performed today as a result of the rigid fixation achieved from the newer techniques.

Summary

Occipitocervical fusion is not a routine operation and is a challenging procedure due to complex anatomy of the craniocervical junction. Its unique anatomic and biomechanical property subjects any instrumentation construct to significant stress. Instability at this region can be caused by a variety of acute and chronic conditions and subtle neurological symptoms in patients. Recognition of OC instability, followed by treatments including reduction, immobilization, and operative fixation, are

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