The role of TNXB single-nucleotide polymorphisms in recurrent shoulder dislocation

Tenascin-X (TNX) is an extra-cellular matrix glycoprotein associated with collagen fibril deposition. Recent reports have linked truncated TNX mutations (TNXB) to generalized joint hypermobility and most importantly recurrent joint dislocation. In the present study, we investigated whether there is an association between joint dislocation recurrence rate and the frequency of TNXB single-nucleotide polymorphisms (SNPs). Seventy-eight patients treated for post-traumatic shoulder instability and 82 healthy controls were genotyped for selected TNXB SNP using TaqMan® Genotyping Assays. At a mean follow-up of 24 months recurrence rate and clinical outcomes were evaluated using the Constant and Murley, Rowe, and DASH scores. The association between genotypes and joint dislocation was tested using the dominant, recessive and additive models, and the model-free approach. Genotype distribution of the examined SNPs did not significantly deviate from the Hardy-Weinberg equilibrium (HWE) neither in patients nor in the controls. Moreover, there was no significant difference in genotype and allele distribution between patients and controls. Finally, no difference in genotype frequency was detected between patients who experienced a re-dislocation after the initial surgery and patients who did not sustain a re-dislocation. The SNPs investigated in this study have no clinically relevant influence on TNXB gene expression and/or TNX function. Therefore, these SNPs could not be used for predicting individual risk of recurrent shoulder dislocation.