• Foot Ankle Surgery

Acute Achilles tendon rupture (ATR) is a frequent injury that results in persistent functional deficits for a large proportion of the patients. In order to improve treatment and reduce the incidence, it is essential to understand the underlying biological mechanisms that cause a tendon rupture. This knowledge is, however, still limited. The current PhD thesis aimed to investigate the etiology of ATR and prognostic factors for treatment outcome.

Study I was a registry twin study investigating the genetic contribution to the etiology by calculating concordance rates of monozygotic (MZ) and same-sex dizygotic (SSDZ) twins as well as by estimating the heritability. The concordance rate was higher in MZ twins than SSDZ twins (8.1% vs 4.3%). The heritability was 47% and thus demonstrates a genetic component in the etiology of ATR.

Study II was a prospective cross-sectional study analyzing samples from ATR with 16S ribosomal deoxyribonucleic acid (rDNA) polymerase chain reaction (PCR) to detect bacteria. Bacterial DNA was found in 2 out of 20 ruptured Achilles tendons. The identified bacteria were normal human skin bacteria. These findings underline that bacteria are infrequent in ATR and likely detected due
to contamination.

Study III investigated the tendon turnover prior to and in the first two weeks after ATR by measuring the level of carbon-14 (14C) as well as the incorporation of deuterium (2H) and 15N-proline in the tendon tissue, respectively. Consistently lower levels of 14C were found in samples from ATR than the expected 14C levels based on a model of healthy Achilles tendons, indicating an increased tendon turnover prior to rupture. No marked increase in the collagen formation was found in the initial healing phase.

Study IV investigated if female sex and high age negatively affected the Achilles tendon Total Rupture Score (ATRS) after ATR by using data from the Danish Achilles tendon Database (DADB). The results showed no difference between the sexes in ATRS from baseline to follow-up. Patients older than 65 years had a clinically relevant better change in ATRS compared with patients from 45 to 65 years.

In conclusion, genetics contributes substantially to the etiology of ATR, whereas bacteria are unlikely to play a pathogenic role in the etiology. Furthermore, ATR is preceded by increased tendon turnover indicating a diseased tendon prior to rupture. Finally, female sex and high age do not seem to negatively affect treatment outcomes after ATR.

Link til studie I: https://www.sciencedirect.com/science/article/pii/S1268773122000467?via%3Dihub
Link til studie 2: https://pubmed.ncbi.nlm.nih.gov/35982829/
Link til studie 4: https://link.springer.com/article/10.1007/s00167-020-06003-7