Women who have undergone a mastectomy move their shoulders differently to those who have not had the operation, a study has found.

The findings may be linked to the fact that many women report shoulder problems after surgery for breast cancer. The study’s authors, however, say it is too soon to be sure.

Physiotherapist Dr Jack Crosbie from the University of Sydney and colleagues report their findings in the journal Physical Therapy.

“A lot of women who have had a mastectomy do have problems with their shoulder, but because they’re so relieved to survive their cancer it tends to be not a high priority,” Dr Crosbie said.

Previous studies have relied on self-reports from women, but Dr Crosbie and his colleagues have carried out the first biomechanical study of the problem.

They compared the arm and upper trunk movement of women who had had a mastectomy with those of the same age who had not.

None of the women in the study reported shoulder pain or restriction.

The women, aged between 45 and 80, carried out simple every-day movements such as reaching their arms out.

There were 29 women who had had a mastectomy on the same side as their dominant arm and 24 women who had had a mastectomy on the opposite side of their dominant arm.

“Whichever side the surgery had occurred on there was a change in the coordination pattern of the shoulder girdle and the shoulder joint on that side, compared to the control women,” Dr Crosbie said.

He says women who had had a mastectomy tended to move their shoulder girdle (scapula) more and their shoulder joint (and arm) less when reaching the same distance as women without a mastectomy.

“They were sort of hitching their shoulder, particularly on the side that had been operated on,” he said.

Dr Crosbie says this type of movement is also seen in problems such as frozen shoulder, where people try to minimise moving the shoulder joint itself.

But he emphasises it is too early to say whether the pattern of movement seen in the post-mastectomy group of women will lead to restriction and pain.

Cause unknown

Dr Crosbie says it is not known what causes the difference in movement.

He says it has been suggested that the asymmetry of having one breast removed may cause the difference in movement because one side of the body is lighter.

“We can’t exclude that,” Dr Crosbie said, adding that his team found women with small breasts were equally affected as women with large breasts. This was not reported in the paper.

Dr Crosbie speculates that the change in movement could be due to habituation.

He says it is possible that conditions after the operation lead women to constrain their movements because, for example, they do not want to stretch their scar or damage their wound.

Dr Crosbie says he would like to conduct a longitudinal study of women to see the impact of mastectomy.

He thinks it would be useful to include in the study one group of women who are encouraged to move their shoulder properly after surgery to see if this reduces the number of reports of shoulder problems later.