Pseudoathrosis Rates after ACDF Studied in Comprehensive Literature Review
Commentary by Michael F. Shriver, BS
The largest and most comprehensive literature review and meta-analysis of pseudoarthrosis rates after anterior cervical discectomy and fusion (ACDF) underscored significant variation in the definition of pseudoarthrosis and found that study design and follow-up criteria influenced how frequently this complication was identified. Although pseudoarthrosis is not always bothersome to patients, it may have negative effects on clinical outcome. To shed some light on the phenomenon of pseudoarthrosis after ACDF, Shriver et al evaluated the role of factors such as bone graft types, study design, follow-up time, and the number of levels fused.
The investigators conducted a database search of prospective cohort studies and randomized controlled trials (RCTs) of ACDF procedures, excluding those without graft fusion and without plate fixation, as well those encompassing more than three disc levels. They performed a meta-analysis of the 17 studies meeting their criteria that were published between 2003 and 2013 (12 RCTs and 5 prospective cohort studies). From the included studies, they recorded the type of study, publication year, graft type, follow-up time, number of pseudoarthrosis events, total study population, surgical technique, number of ACDF operative levels, and the study’s definition of pseudoarthrosis. The investigators used a random-effects model with inverse variance weighting to analyze the data. Two independent reviewers evaluated the studies, and the investigators used The Cochrane Collaboration’s tool to assess risk of bias.
- Overall, 56 the 1,065 patients reported pseudoarthrosis, for a rate of 2.6% (95% CI [Confidence Intervals], 1.3-3.9), with a mean follow-up time of 29.1 months.
The investigators uncovered differences in pseudoarthrosis rates based on graft type. Among patients who underwent allograft fusion procedures, 45 of 736 patients developed pseudoarthrosis, resulting in a rate of 4.8% (95% CI of 1.7-7.9). This compared with 10 of 223 patients who underwent autograft fusion procedures, which resulted in an overall rate of 0.9% (95% CI of –0.4-2.1).
The investigators noted that because there was a lack of studies directly comparing the two surgical approaches, they could not calculate relative risks, but they suggested their findings had “potentially identified a worthwhile difference between the two procedures” and that additional studies are needed to provide knowledge about the differences in pseudoarthrosis rates between graft types to “properly inform surgeons in their choice of graft for surgery.”
Rate of Reporting
The type of trial also influenced the rate of reporting of pseudoarthrosis. Among the 12 RCTs, the rate was 4.8% (95% CI, 2.6-7.0), whereas among the 5 prospective cohort studies, the rate was 0.2% (95% CI, –0.1-0.5). The investigators noted that the “substantial decrease in the diagnosis of pseudoarthrosis among prospective cohort studies may accurately characterize the inadequacy of real-world pseudoarthrosis findings.” They hypothesized that the RCT design with more detailed “follow-up time criteria and radiographic examination” improved the investigators’ ability to recognize pseudoarthrosis. This finding, they suggested, “highlights the need for physicians to follow patients appropriately in the postoperative period for proper recognition of pseudoarthrosis in ACDF patients.”
Length of Follow-up
The length of follow-up time was another parameter the investigators evaluated. Among patients in the 11 studies reporting a follow-up time of 12 to 24 months, the rate of pseudoarthrosis was 3.1% (95% CI, 1.2-5.0). Among those in the 6 studies with a follow-up time longer than 24 months, the pseudoarthrosis rate was 2.3% (95% CI, 0.1-4.4). The investigators noted that the overlapping CIs for these measurements “[suggest] that minimal changes in fusion rates occur beyond a year from surgery.” Similarly, because the rate of pseudoarthrosis in patients who underwent single-level ACDF was 3.7% (95% CI, 1.6-5.7), which was not statistically different from the 2.6% overall rate, the investigators said the rate was likely to be similar for “all ACDF surgeries, no matter the number of levels.”
Comprehensive Estimation of Actual Incidence
The investigators concluded that the overall pseudoarthrosis rate they uncovered in their meta-analysis “likely represents a comprehensive estimation of the actual incidence of pseudoarthrosis across a heterogeneous group of surgeons, patients, and ACDF techniques.” Calling for the development of standardized criteria defining pseudoarthrosis, they noted that their study “should serve as a framework for individual surgeons to understand the impact of various surgical techniques on the rate of pseudoarthrosis.”
Commentary by Michael F. Shriver, BS
Case Western Reserve University School of Medicine
The rate of pseudoarthrosis identified within this meta-analysis likely represents a comprehensive, valid estimation of the actual incidence of pseudoarthrosis. Through our analysis of pseudoarthrosis rates across a diverse group of surgeons, patients and anterior cervical discectomy and fusion (ACDF) techniques, the rates identified among the various subgroups accurately characterize real-world clinical events.
The included studies were separated into various meta-analysis groups, analyzing the date based on graft type (allograft vs autograft), follow-up time, surgical levels and study type (randomized controlled trials vs prospective cohort studies). These sub-group analyses demonstrated a noticeable difference in rates of pseudoarthrosis among these factors. Autograft fusion resulted in a reduced pseudoarthrosis rate relative to allograft fusion, but this did not reach statistical significance. Further studies comparing the rate of pseudoarthrosis in these graft types are needed, because our analysis was limited by small study sample sizes. Pseudoarthrosisrtes also exhibited a large difference between randomized controlled trials and prospective cohort studies, signifying that the amount and degree of follow-up criteria impacts the rate of identified pseudoarthrosis within patient samples.
There is no standardized definition or criteria for the diagnosis of pseudoarthrosis currently. To ensure the proper diagnosis of pseudoarthrosis among patients, standardized criteria are needed. Larger, randomized studies are necessary to properly establish such criteria, which may ultimately improve recognition and treatment of pseudoarthrosis and reduce its potential deleterious effects on patient quality of life following surgery. Our analysis should offer individual surgeons the ability to understand the impact of various surgical techniques and factors on the rate of pseudoarthrosis development in their own patient cohorts.