<p>Example: 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.</p><p>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.</p><p>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.</p>