Anterior cervical pseudarthrosis
Difficult to assess because of lack of validated criteria. Estimate: 2–20%. Higher with dowel technique (Cloward) than with the keystone technique of Bailey & Badgley or with the interbody method of Smith-Robinson (10%) or with non-fusion advocated by Hirsch. One criterion: motion>2mm between the tips of the spinous processes on lateral flexion/extension X-rays.
Other criteria that are specific but not sensitive: lucencies around the screws of an anterior plate, toggling of the screws on flexion/extension X-rays.
Not uniformly associated with symptoms or problems. Some patients may have chronic or recurrent neck pain, some may present with radicular symptoms. (NB: when DePalma’s data is analyzed with patients reclassified as failures if the neck and/or arm symptoms persist, the success rate of surgery is lower with pseudarthrosis)
More than 2 mm movement between spinous processes on dynamic (flexion-extension) cervical spine X-rays is recommended as a criterion for pseudarthrosis (Level B Class II); this measurement is unreliable when performed by the treating surgeon (Level C Class II).
Visualization of bone trabeculation across the fusion on static films is a less reliable marker for fusion (Level D Class III) (2D reformatted CT increases the accuracy (Level D Class III)).
see Cervical fusion criteria.
No treatment is required for asymptomatic pseudarthrosis. Options for symptomatic patients include re-resection of the bone graft with repeat fusion (some recommend using autologous bone if allograft was used; a plate may be considered if one was not used previously), cervical corpectomy with fusion, or posterior cervical fusion.
Revision of symptomatic pseudarthrosis should be considered (Level D Class III). Postrior approaches may be associated with higher fusion rates on revision than anterior approaches (Level D Class III).
In 1- and 2-level ACDF with plating involving the same number of fusion levels, there was no statistically significant difference in the pseudarthrosis rate, revision surgery rate, subsidence, and lordosis loss between PEEK cages and structural allograft 1).
Common interbody graft options for anterior cervical discectomy and fusion (ACDF) include structural allograft and polyetheretherketone (PEEK). PEEK has gained popularity due to its radiolucency and its elastic modulus, which is similar to that of bone.
A study sought to compare the rates of pseudarthrosis, a lack of solid bone growth across the disc space, and the need for revision surgery with the use of grafts made of allogeneic bone versus PEEK.
127 cases in which patients had undergone a 1-level ACDF followed by at least 1 year of radiographic follow-up. Data on age, sex, body mass index, tobacco use, pseudarthrosis, and the reoperation rate for pseudarthrosis were collected. These data were analyzed by performing a Pearson’s chi-squared test.
Of 127 patients, 56 had received PEEK implants and 71 had received allografts. Forty-six of the PEEK implants (82%) were stand-alone devices. There were no significant differences between the 2 treatment groups with respect to patient age, sex, or body mass index. Twenty-nine (52%) of 56 patients with PEEK implants demonstrated radiographic evidence of pseudarthrosis, compared to 7 (10%) of 71 patients with structural allografts (p < 0.001, OR 9.82; 95% CI 3.836-25.139). Seven patients with PEEK implants required reoperation for pseudarthrosis, compared to 1 patient with an allograft (p = 0.01, OR 10.00; 95% CI 1.192-83.884). There was no significant difference in tobacco use between the PEEK and allograft groups (p = 0.586).
The results of this study demonstrate that the use of PEEK devices in 1-level ACDF is associated with a significantly higher rate of radiographically demonstrated pseudarthrosis and need for revision surgery compared with the use of allografts. Surgeons should be aware of this when deciding on interbody graft options, and reimbursement policies should reflect these discrepancies 2).
The objective of a systematic review done by Kaiser et al. from the Department of Neurological Surgery, Columbia University, New York, USA, was to use evidence-based medicine to identify the best methodology for diagnosis and treatment of anterior pseudarthrosis.
The National Library of Medicine and Cochrane Database were queried using MeSH headings and key words relevant to pseudarthrosis and cervical spine surgery. Abstracts were reviewed, after which studies meeting inclusion criteria were selected. The guidelines group assembled an evidentiary table summarizing the quality of evidence (Classes I-III). Disagreements regarding the level of evidence were resolved through an expert consensus conference. The group formulated recommendations that contained the degree of strength based on the Scottish Intercollegiate Guidelines network. Validation was done through peer review by the Joint Guidelines Committee of the American Association of Neurological Surgeons/Congress of Neurological Surgeons.
Evaluation for pseudarthrosis is warranted, as there may be an association between clinical outcome and pseudarthrosis. The strength of this association cannot be accurately determined because of the variable incidence of symptomatic and asymptomatic pseudarthroses (Class III). Revision of a symptomatic pseudarthrosis may be considered because arthrodesis is associated with improved clinical outcome (Class III). Both posterior and anterior approaches have proven successful for surgical correction of an anterior pseudarthrosis. Posterior approaches may be associated with higher fusion rates following repair of an anterior pseudarthrosis (Class III).
If suspected, pseudarthrosis should be investigated because there may be an association between arthrodesis and outcome. However, the strength of this association cannot be accurately determined. Anterior and posterior approaches have been successful 3).