Summary

Genetics contribute substantially to the etiology of ATR with an estimated heritability of the liability to ATR of approximately 50%.

Abstract

Objective

The etiology of Achilles tendon rupture (ATR) is complex and not fully understood. The aims of the study were 1) to calculate the concordance rate for monozygotic twins and same-sex dizygotic twins and 2) to estimate the heritability of ATR.

Methods

The study was performed as a registry study using the Danish Twin Registry and the Danish National Patient Registry. Twins registered with ATR were retrieved and the probandwise concordances for monozygotic and dizygotic twins were calculated. Additionally, using structural equation analyses the heritability of ATR was estimated.

Results

The study sample consisted of 85,534 twins born from 1870-1996. Of these, 572 (0.67 %) were registered with ATR in the period from 1994 to 2014. The concordance rate was 0.081 (95% CI 0.018-0.154) for MZ twins and 0.043 (95% CI 0.014-0.095) for SSDZ twins. The heritability of ATR was 47% (95% CI 31-62%).

Conclusion

This study found that genetics contribute substantially to the etiology of ATR with an estimated heritability of the liability to ATR of approximately 50%. The finding generates the hypothesis that genetics play a role in the pathological changes that occur in the Achilles tendon before a rupture. The risk of ATR for a twin within a 20 year period, if the co-twin has had an ATR, was 8% for MZ twins and 4% for SSDZ twins which may be clinically relevant.