Abstract
Tumour necrosis factor-alpha is a proinflammatory cytokine that has been implicated in the propagation of inflammatory responses to bacterial infection and wear debris particles around loosened total hip replacements (THR). Individual TNF responses to such stimuli may be dictated by genetic variation. Single nucleotide polymorphisms (SNPs) at several loci within the TNF gene are associated with disease severity and susceptibility in a number of inflammatory conditions, but only a few SNPs have been screened in any one study.
14 SNPs have been identified within the TNF gene. Our unit has previously demonstrated that 5 SNPs are monomorphic in a sample group of UK Caucasians. We performed a case control study of the remaining 9 polymorphic positions (−1031, −863, −857, −376, −308, −238, +489, +851 and +1304) for possible association with deep sepsis or aseptic loosening.
All patients included in the study were Caucasian and had had a cemented Charnley THR and polyethylene cup. Cases consisted of 44 patients with early aseptic loosening (defined as that occurring within 6 years of implantation and findings at revision surgery or by the criteria of Hodgkinson et al for the acetabulum and Harris for the femoral stem) and 30 patients with microbiological evidence at surgery of deep infection. Controls consisted of 85 THRs that had remained clinically asymptomatic for over 10 years and demonstrated no radiographic features of aseptic loosening or ‘at risk’ signs as described by Wroblewski et al. DNA was extracted from venous blood and genotyped by Snapshot assay.
Genotype and allele frequencies for all SNPs were in Hardy-Weinberg equilibrium between THR controls and a random sample of UK Caucasians. The most significant associations were between the −238A (p< 0.05) and −863T (p< 0.05) alleles and aseptic loosening. A trend towards association was found between the −863A SNP and deep infection (p=0.80). The −238 A/G and −863 G/T genotypes were associated with deep infection (p< 0.05). No other significant associations were found.
Genetic polymorphism of TNF appears to play a significant role in THR aseptic loosening and possibly in deep infection. SNP markers may serve as predictors of implant survival and response to therapy such as anti-TNF treatment.
Theses abstracts were prepared by Mr Peter Kay. Correspondence should be address to him at The Hip Centre, Wrightington Hospital, Appley Bridge, Wigan, Lancashire WN6 9EP.
