Degenerate-disc Infection Study with Contaminant Control: Discussion on the Research Methods

OBJECTIVE: The role of bacterial infection in the causation of disc degeneration and its consequences is controversial. The current evidence is limited to underpowered studies, with the majority of such studies having only an internal contaminant arm, and only one study having a control arm with a non‐degenerate disc population. The Degenerate‐disc Infection Study with Contaminant Control (DISC) study includes a control arm and an internal contaminant control to resolve these shortcomings. METHODS: The study is designed as a case‐control study: cases are patients undergoing surgery for degenerated disc pathology and controls are patients undergoing surgery for non‐degenerate pathology, such as trauma, scoliosis or tumor cases. RESULTS: This study is part of a multi‐centric trial involving six spine centers with 15 spine surgeons contributing. The DISC study methodology, rationale and controversies are presented here. The predominant issue is how to interpret contamination. We present our algorithm for the DISC study to address this. For disc samples that are positive concurrently with positive paraspinal tissue sample, the result will be interpreted as contamination. For positive disc samples with a negative paraspinal tissue culture result, the interpretation of this result will be infection. If cultures for both disc sample and paraspinal tissue sample are negative, then the result is interpreted as non‐infected. If the disc culture is negative but paraspinal tissue culture is positive, then it is treated as a contaminant. CONCLUSIONS: Future large‐scale studies are required with a good control arm, a contamination arm, and histopathological correlations.