gms | German Medical Science

Objective: Recurrence rates after lumbar discectomy are reported to be up to 5 and 15%. The mechanical stability and the level of degeneration of the remaining discs play a major role in the recurrent disease. Increasing evidence suggests that genetic factors are important determinants of symptomatic intervertebral disc disease. Recent studies focused on mutations in the collagen genes COL9A2 and COL9A3.

Methods: Two groups of patients were investigated: 144 patients experienced recurrence after lumbar discectomy within two years, 144 patients were free of recurrence with a minimal disease-free interval of 10 years. Genomic DNA was extracted from formalin-fixed, paraffin-embedded biopsy samples using standard protocols. DNA fragments generated by PCR amplification using Col9A2 specific primer pairs were digested with restriction enzymes. For the detection of the Trp allele a BsmFI digest was performed, and the Gln and the Arg allele of the Col9A2 gene were discriminated by a BceAI digest.

Results: A 128bp PCR fragment was amplified from all samples included in the present study. All samples showed a complete digestion resulting in a 79bp and a 49bp fragment after treatment with the BsmFI restriction enzyme. These data indicate the absence of the Trp allele in the biopsy samples of the present study. The BceAI digest gave different results: In the group of patients with recurrent LDD 9 PCR fragments were completely digested resulting in a 54bp and a 74bp fragment (Arg), 112 samples showed an undigested 128bp fragment (Gln) and 23 probes showed both an undigested 128bp fragment and the two fragments of 74bp and 54bp resulting from cutting with BceAI (heterozygous Arg/Gln). In contrast, in the group without recurrent disease only 2 samples were completely digested, 117 PCR fragments were undigested and 25 samples showed three restriction fragments indicating a heterozygous situation. The results were confirmed by sequencing of 4 representative PCR fragments which exhibited a homozygous Arg/Arg, a homozygous Gln/Gln and heterozygous Arg/Gln genotype.

Conclusions: The demonstration of a higher percentage of homozygosity for the Arg allele in the recurrence group of the present study might indicate that the polymorphic Col9A2 codon could be a marker for an increased risk for early recurrence after lumbar disc surgery.