Why Do Patients Stay Longer Than Three Nights Following Hip and Knee Arthroplasty?

Prolonged length of stay (PLOS) is frequently cited by secondary data studies as an adverse outcome following hip and knee arthroplasty. Although perhaps indisputable that PLOS increases the cost of hospitalization, it is unknown whether it is an appropriate measure of the quality of an arthroplasty procedure.

We searched our institution’s database for all hip and knee arthroplasty procedures over a 5-year period using MS-DRG (Medicare Severity-Diagnosis Related Group) 469 and 470. Cases with greater than 3 night stays were identified. Charts were manually reviewed by 2 independent reviewers to identify the primary reason for PLOS, and the need for 30-day readmission or reoperation.

Of a total 4347 hip and knee arthroplasty cases, 218 (5.0%) were identified with LOS greater than 3 nights. The majority of prolonged stays were due to exclusively medical reasons (81 cases: 37.2%; 95% confidence interval [CI] 31.0-43.7). The second most common cause was inpatient days prior to the arthroplasty procedure (45 cases: 20.6%; 95% CI 15.8-26.5). Orthopedic reasons for PLOS were significantly less common than medical reasons (36 cases: 16.5%; 95% CI 12.2-22.0, P < .0001), most often due to failure to meet therapy goals. Neither readmission (31 cases: 14.2%) nor reoperation (10 cases: 4.6%) was associated with an underlying reason for PLOS.

When evaluating LOS as a measure of quality of an arthroplasty procedure, readers of secondary “big data” studies should be aware that there are significant limitations to its utility. Even after controlling for potential confounders, we found that PLOS does not necessarily reflect an adverse outcome.