The influence of subdiagnosis on radiographic and clinical outcomes after lumbar fusion for degenerative disc disorders: An analysis of the literature from two decades

Study Design. A critical review of published literature from 2 decades. Objective. To critically analyze the literature from 1979 to 2000 in order to examine the influence of subdiagnosis on outcome after fusion for lumbar degenerative disc disorders. Summary of Background Data. Numerous diagnostic subgroups of degenerative disc disorders exist. Although it is commonly believed that surgical outcomes after lumbar fusion are influenced by these subdiagnoses, there is a paucity of literature demonstrating differences in clinical outcomes or fusion rates among them. As the indications for fusion have been under greater scrutiny recently, this information would be useful in prognosticating outcomes and optimizing patient selection. Methods. A computer search of the English literature using the keywords " degenerative," " lumbar," and " fusion" was performed. Disorders were organized according to the following subdiagnostic groups: degenerative spondylolisthesis ( DDDsp), herniated disc ( DH), degenerative scoliosis ( DDDsc), stable DDD ( DDDs), dynamically unstable DDD ( DDDu), and DDD that was not specified as either DDDu or DDDs ( DDDn). For each group, the type of instrumentation, fusion location, fusion rate, clinical outcome, and complication rate were recorded in a computer database. Data were pooled by simple summation and statistically analyzed using a chi(2) test or Fisher exact test. Results. Of 244 articles identified, 78 satisfied inclusion criteria with data from 4454 patients recorded. The most common diagnosis was DDDn ( 50%), followed by DDDsp ( 25%), DH ( 14%), DDDu ( 6%), DDDs ( 3%), and DDDsc ( 2%). The DDDn group had a higher fusion rate than DDDsp ( P = 0.025), but a lower clinical outcome ( P = 0.051). Complication rates were highest in DDDsc, whereas this subdiagnosis also had the best reported clinical outcomes. In comparing individual subgroups, a trend towards higher fusion rate and better clinical outcome was noted in DDDsp cases with instrumentation compared to noninstrumented cases. This trend was reversed for patients in the DDDn group, in whom better clinical outcomes were noted after noninstrumented fusions regardless of a lower fusion rate. Conclusions. The present data indicate that clinical outcomes and fusion rates statistically differ among the various subgroups of degenerative disc disease. Concerning the use of instrumentation, it appears that it may have greater clinical benefit in patients with DDDsp than DDDn. These findings underscore the importance of delineating specific clinical diagnoses when documenting results of lumbar fusion. This information might also be useful for both selecting surgical candidates and discussing anticipated operative outcomes.