Toronto, Jul 9 (IANS): Female athletes who are younger than 25 are at an increased risk for a repeat tear of the knee's anterior cruciate ligament (ACL) after surgery to repair it, a study has found.

The findings showed that the graft size, sex and age can also have a significant effect on the odds of an ACL re-tear post a surgery for a hamstring graft.

"Our research noted that female patients under the age of 25 with a graft size of less than 8 mm have an increased chance of re-tearing their ACL following reconstruction," said lead author, Duong Nguyen, Orthopedic Surgeon and Professor at McMaster University in Toronto.

Further, “factors, including oestrogen levels, anatomical differences, and decreased knee strength might also cause to repeat tears in some female patients,” Nguyen added.

For the study, the team included just over 500 athletes (235 females and 268 males) who underwent ACL reconstruction with a hamstring graft and were followed for two years.

Their average age was 27. They were allowed to return to sports six to 12 months after surgery if they were pain-free, had equal quadriceps/hamstring strength, and had finished a rehabilitation program.

"Given the results of our study, we feel that surgeons should counsel their younger, female patients accordingly and consider modifying their surgical techniques to utilise larger size grafts and/or rehabilitation strategies to lessen the chance of a re-tear," said Nguyen.

The results were presented at the American Orthopaedic Society of Sports Medicine's Annual Meeting 2016 in Colorado Springs in the US, recently.