Influence of diagnosis on outcome after lumbar fusion for degenerative disc disease

Abstract Purpose of study: Numerous stages of the degenerative cascade exist for lumbar degenerative disc disease (DDD). Individual stages can be considered diagnostic subgroups, each with a particular pathology, prognosis and treatment requirement. Numerous series have been published concerning results of lumbar fusion for DDD without differential analysis between subgroups. This can lead to confusion when assessing individual treatment outcomes. It was the authors' purpose to critically analyze the literature from the past 20 years to examine the influence of diagnostic subgroups on surgical outcome after fusion for lumbar DDD. Methods used: A computer search of the English using the keywords degenerative, lumbar, and fusion was performed. Disorders were organized according to the following 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 and not including DDDsp, DDDsc, or DH (DDDn). For each group, the type of instrumentation, fusion, location, fusion rate, clinical outcome, and complication rate were recorded in a computer database. Data was pooled by simple summation and statistically analyzed using a chi-squared test. of findings: 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 fusion rate was 76% for DDDsp, 95% for DH, 87% for DDDsc, 91% for DDDs, 88% for DDDu, and 87% for DDDn. Fusion rates for DDDsp were significantly lower than those for DDDn (p=.01). The highest fusion rates were calculated for DH. Clinical outcome scores were good or excellent in 80% of DDDsp cases, 78% of DH, 87% of DDDsc, 71% of DDDs, 67% of DDDu, and 73% of DDDn. The worst clinical outcomes were for DDDu, while the best were documented for DDDsc. Though fusion rates were lower in the DDDsp group, clinical outcomes were significantly better than those for DDDn (p=.05). Considering all unstable diagnoses (DDDsc, DDDu, DDDsp) versus stable diagnoses (DDDn, DDDs, and DH), clinical outcomes were significantly better for the unstable group (p=.05). Complication rate was 11% for DDDsp, 1.4% for DH, 55% for DDDsc, 5% for DDDs, 11% for DDDu, and 7% for DDDn. Complication rate was significantly higher for the unstable versus stable group (p=.03). Instrumented fusion was not associated with better clinical outcome than non-instrumented fusion. Relationship between findings and existing knowledge: Diagnostic subgroups of lumbar DDD have individual pathologic, prognostic and treatment characteristics. The presented data indicate that clinical outcome and fusion rates statistically differ among the degenerative cascade subgroups. To the authors' knowledge, this has not been previously demonstrated in a critical analysis. In agreement with previous investigators, the data suggests that successful clinical outcome is not directly dependent on achieving solid bony fusion. Overall significance of findings: These findings highlight the importance of delineating specific clinical diagnoses when documenting results of lumbar fusion. With thoughtful and systematic differentiation between individual subgroups, published clinical results can be better compared and contrasted in order to determine optimal treatment methods. Clear criteria for each subgroup must be formulated to aid the practitioner in estimating expected clinical outcomes from surgical fusion for DDD. Disclosures: No disclosures. Conflict of interest: No conflicts.