Specific Aims or Research Questions

The specific aim of this cohort study is to compare change in pre- to post-operative physical
function in a group of patients undergoing ‘mini-incision’ THA versus a matched group of
controls who had standard open-procedure THA. A difference of 10 points or more on the SF-36
physical function domain between groups measured 1-week before and 6-months after THA will
be considered an important clinical difference.
The secondary aims are:
a. To compare rates of post-op wound infection between groups defined as the need for
antibiotic treatment extending after post-op day 2; a difference of 2% will be
considered clinically important
b. To compare hospital length of stay between groups with a mean difference of ½ day
considered clinically important.
Hypothesis 1: There will be no difference in pre- to post-op SF-36 physical function scores
between patients undergoing ‘mini-incision’ THA compared to patients who had the standard
open-procedure THA.
Hypothesis 2: There will be lower rates of post-op wound infection in the’ mini-incision’ group
compared to the standard open-procedure group.
Hypothesis 3: Length of stay will be shorter in the ‘mini-incision’ group compared to the
standard open-procedure group.