Single nucleotide polymorphisms in the interleukin-6 gene promoter, tumor necrosis factor-alpha gene promoter, and transforming growth factor-beta1 gene signal sequence as predictors of time to onset of aseptic loosening after total hip arthroplasty: preliminary study.

BACKGROUND

Aseptic loosening resulting from inflammatory response to the implant wear debris is the major cause of late total hip arthroplasty (THA) failure. We examined single nucleotide polymorphisms in genes encoding for three involved cytokines--interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha), and transforming growth factor-beta1 (TGF-beta1)--as potential predictors of time to onset of aseptic instability.

METHODS

A total of 41 patients/45 total hip endoprostheses (same type, same surgeon) were followed up for as long as 18 years. They were genotyped for the IL-6 promoter (-597G-->A) and (-572G-->C), TNF-alpha promoter (-308G-->A), and TGF-beta1 signal sequence (29T-->C) transitions. Cox regression was performed on the prosthesis survival.

RESULTS

Overall, 22 of 45 prostheses developed aseptic instability. Cumulative survivals at 10 and 15 years after THA were 95.6% and 66.6%, respectively. The effect of a particular polymorphic site was estimated with adjustment for sex, age at THA, reason for THA, and the effects of other analyzed sites. The hazard ratio (HR) for genotype T/T versus "C-allele carriage" at the TGF-beta1 site was 8.23 [95% confidence interval (CI) 1.45-46.8] (P=0.017) or 5.70 (1.39-23.4) (P=0.016) when the IL-6 promoter sites were considered as a "combination of genotypes (-597)|(-572)." The most prevalent combination of genotypes at IL-6 sites was G/A (-597)|C/C (-572). HR for this combination (versus other combinations) was 5.43 (1.73-17.0) (P=0.004) when "TGF-beta1 (29T-->C)" was considered as a three-level factor (three possible genotypes), and 4.92 (1.71-14.1) (P=0.003) when TGF-beta1 site was considered as a two-level factor (T/T and "C-allele carriage"). The HR for the "A-allele carriage" at TNF-alpha (-308G-->A) could not be determined (only two patients had the G/G genotype).

CONCLUSIONS

This preliminary study is the first to suggest that the TGF-beta1 signal sequence (29T-->C) and IL-6 promoter (-597G-->A)|(-572G-->C) transitions are predictive for the time to onset of aseptic instability after THA.