Teenage rugby players are suffering bone fractures similar to those found in car crash victims, Irish doctors have claimed.
The report comes less than a week after more than 70 doctors and health experts wrote an open letter to British authorities calling for an end to tackling in school rugby matches.
Writing in the journal BMJ Case Reports, the doctors describe three cases of acetabular fractures in teenage rugby players, sustained while playing or training.
Each occurred "as a result of pressure exerted through a flexed hip with the knee on the ground", often encountered during a two-man tackle where one hits high, the other low. Acetabular fractures affect the socket of the hip bone, and dislocation of the hip often happens at the same time.
"We have not previously encountered these injuries in a juvenile sporting population," the doctors claim.
"In order to prevent the potentially devastating consequences of these injuries, it may be necessary to implement rule changes or size restrictions in the juvenile game."
One of those who signed the open letter, doctor and author Prof Allyson Pollock, told Story on Monday there should be no tackling in rugby until players are 18.
"The risks and rates of injuries are high, and these are serious injuries. They include fractures, dislocated shoulders, ligament tears, spinal injuries, concussion and head trauma."
In New Zealand, tackling is introduced at age seven.
More than 100,000 Kiwis under 18 play rugby. In 2014 there were more than 28,000 injuries in that age group, 1356 of them concussions.
The Irish doctors say since rugby went professional, players' "physical profile, training regimens and injury patterns" have changed significantly, which has trickled down to lower levels of the game.
"Increased ball-in-play has also increased the exposure time to potential injury," they write, also suggesting changes to the rules at the breakdown to prevent players standing over the ball being "susceptible to a significant axial load across the hip", the primary cause of acetabular fractures.