Background: Prolonged wound drainage following total hip or total
knee arthroplasty has been associated with an increased risk of postoperative
morbidity. The purpose of this study was to determine the pharmacologic,
surgical, and patient-specific factors that are associated with prolonged
wound drainage and the relationship of this complication to the length of
hospital stay and the rate of wound infections.
Methods: We conducted a retrospective observational study of 1211
primary total hip arthroplasties and 1226 primary total knee arthroplasties.
Prospectively collected data included body mass index, intraoperative blood
loss, surgical time, type of prophylaxis against deep venous thrombosis, and
length of hospital stay. The association of these factors with the duration of
postoperative wound drainage was analyzed. An acute infection developed after
fifteen primary total hip arthroplasties and ten primary total knee
arthroplasties. The patients with an acute postoperative infection were
compared with their uninfected counterparts, and an odds ratio was determined
to estimate the risk of prolonged wound drainage resulting in a wound
Results: Morbid obesity was strongly associated with prolonged wound
drainage in the total hip arthroplasty group (p = 0.001) but not in the total
knee arthroplasty group (p = 0.590). An increased volume of drain output was
an independent risk factor for prolonged wound drainage in both groups.
Patients who received low-molecular-weight heparin for prophylaxis against
deep venous thrombosis had a longer time until the postoperative wound was dry
than did those treated with aspirin and mechanical foot compression or those
who received Coumadin (warfarin); this difference was significant on the fifth
postoperative day (p = 0.003) but not by the eighth postoperative day.
Prolonged wound drainage resulted in a significantly longer hospital stay in
both groups (p < 0.001). Each day of prolonged wound drainage increased the
risk of wound infection by 42% following a total hip arthroplasty and by 29%
following a total knee arthroplasty.
Conclusions: Morbid obesity, the use of low-molecular-weight
heparin, and a higher drain output were associated with a prolonged time until
the postoperative wound was dry following a primary total hip arthroplasty,
whereas a higher drain output was the only risk factor associated with
prolonged drainage following a primary total knee arthroplasty. Prolonged
drainage was associated with a higher rate of infection following a primary
total hip arthroplasty, whereas obesity was the only identified independent
risk factor for postoperative infection following a primary total knee
Level of Evidence: Prognostic Level II. See Instructions
to Authors for a complete description of levels of evidence.