Anterior Cervical Discectomy and Fusion Pseudarthrosis: Posterior Versus "Redo" Anterior

Pseudarthrosis of the Cervical Spine

Pseudarthrosis of the cervical spine represents a common and challenging problem for spine surgeons. Rates vary greatly from as low as 0%-20% to >60% and depend heavily on patient factors, approach, and number of levels. While some patients remain asymptomatic from pseudarthrosis, many require revision surgery due to instability, continued neck pain, or radiculopathy/myelopathy. We aimed to provide a practical, narrative review of cervical pseudarthrosis to address the following areas: (1) definitions, (2) incidence, (3) risk factors, (4) presentation and workup, (5) treatment decision-making, and (6) postoperative care. It is our hope the current review provides a concise summary for how to diagnose and treat challenging cervical nonunions.

Clinical Practice in Spine Surgery: An International Survey

BACKGROUND

 The availability of diverse and sophisticated surgical options to treat spine conditions is compounded by the scarcity of high-level evidence to guide decision-making. Although studies on discrete treatments are frequently published, little information is available regarding real-world surgical practice. We intended to survey spine surgeons to assess clinical management of common spine diagnosis in day-to-day settings.

METHODS

 An online survey was distributed among neurosurgeons and orthopaedic surgeons worldwide. The obtained assessment of common surgical practice is contextualized in a review of the best available evidence.

RESULTS

 The survey was answered by more than 310 members of several European, Australasian, and South African professional societies. The submitted responses translate a surgical practice generally grounded on evidence, favoring well-tried techniques, providing comprehensive treatment for the most severe diagnoses. Such practice comes mostly from neurosurgeons focused on spine surgery, practicing in teaching hospitals.

CONCLUSION

 We believe that the pragmatic, day-to-day approach to spine conditions captured in the present survey offers an informative insight to involved surgeons.

Effectiveness of cervical zero profile integrated cage with and without supplemental posterior Interfacet stabilization

BACKGROUND

Conditions requiring cervical decompression and stabilization are commonly treated using anterior cervical discectomy and fusion using an anterior cage-plate construct. Anterior zero profile integrated cages are an alternative to a cage-plate construct, but literature suggests they may result in less motion reduction. Interfacet cages may improve integrated cage stability. This study evaluated the motion reduction of integrated cages with and without supplemental interfacet fixation. Motion reduction of integrated cages were also compared to published cage-plate results.

METHODS

Seven cadaveric (C2-T1) spines were tested in flexion-extension, lateral bending, and rotation. Specimens were tested: 1) intact, 2) C6-C7 integrated cage, 3) C6-C7 integrated cage + interfacet cages, 4) additional integrated cages at C3-C4 and C4-C5, 5) C3-C4, C4-C5 and C6-C7 integrated cages + interfacet cages. Motion, lordosis, disc and neuroforaminal height were assessed.

FINDINGS

Integrated cage at C6-C7 decreased flexion-extension by 37% (P = .06) and C3-C5 by 54% (P < .01). Integrated + interfacet cages decreased motion by 89% and 86% compared to intact (P < .05). Integrated cages increased lordosis at C4-C5 and C6-C7 (P < .01). Integrated + interfacet cages returned C3-C5 lordosis to intact values, while C6-C7 remained more lordotic (P = .02). Compared to intact, neuroforaminal height increased after integrated cages at C3-C5 (P ≤ .01) and at all levels after interfacet cages (P < .01).

INTERPRETATION

Anterior integrated cages provides less stability than traditional cage-plate constructs while supplemental interfacet cages improve stabilization. Integrated cages provide more lordosis at caudal levels and increase neuroforaminal height more at cranial levels. After interfacet cages, posterior disc height and neuroforaminal height increased more at the caudal segments.

Disappearance of Anterior Cervical Corpectomy Cage

Although cage subsidence and dislodgement are not uncommon in anterior cervical spine surgery, missing cages have seldom been reported. This is the first report of the disappearance of a metallic corpectomy cage after anterior cervical fusion.

A 63-year-old man, who had a history of ankylosing spondylitis and diabetes mellitus, was involved in a motor vehicle accident that broke his neck. The traumatic C6 burst fracture caused myelopathy and instability, which required surgery. He then underwent anterior C6 corpectomy with circumferential fixation, including anterior plating and posterior lateral mass screws from C5-C7. There was a significant improvement in neurological function after the surgery and he could ambulate independently. However, upon a visit at six months postoperation, there was dislodgement of the anterior cervical plate and cage. An attempt to revise the anterior fusion construct was made subsequently, but this surgery could only remove the plate. The metallic cage was left in place during the revision surgery because it was firmly incorporated into the C5 and C7 vertebra and could hardly be adjusted intraoperatively. There were no other interventions during the interval. Upon his visit at 23 months after the initial surgery, the metallic cage was missing. No examinations could locate the cage anywhere in the body, including 36-inch radiographs that demonstrated completely the disappearance of the metallic corpectomy cage. The posterior arthrodesis seemed stable and the patient had no dysphagia or any other gastrointestinal symptoms. The process of the disappearance of the corpectomy cage was never noticed by the patient and he remains free of symptoms to date.

The complete dislodgement of a cervical corpectomy cage that was placed anteriorly could happen without symptoms. The cage might have been expelled during bowel movements and caused little problem. Failure to achieve arthrodesis in anterior cervical fusion, therefore, must be closely monitored.