Published 9/21/2020
Kaitlyn D’Onofrio

What Are the Driving Factors of Hospital LOS in Knee Arthroplasty?

Editor’s note: The following content was originally scheduled for the AAOS Now Daily Edition, which publishes each year onsite at the AAOS Annual Meeting, but this year’s meeting in March was canceled due to COVID-19. Despite the cancellation, members can access virtual content from the Annual Meeting by visiting the Academy’s Annual Meeting Virtual Experience webpage at aaos.org/VirtualAAOS2020.

Hospital length of stay (LOS) following total knee arthroplasty (TKA) varies by patient and is dependent on factors pertaining to the patient, hospital, and surgeon. A study examined which of those three factors play the most significant role in determining a patient’s LOS postoperatively. The researchers concluded that patients’ chronic medical conditions and an academic teaching hospital are the most significant drivers of LOS following TKA. Peter Gold, MD, of the Department of Orthopedic Surgery at Long Island Jewish Medical Center in New Hyde Park, N.Y., presented the study as part of the Annual Meeting Virtual Experience.

“Hospital LOS is a driver for the overall cost of care in total joint arthroplasty,” Dr. Gold told AAOS Now. “There has been a major focus on improving preoperative medical optimization, patient selection, and intraoperative pain management in recent years, which we believe has helped to decrease LOS and therefore lower cost, while improving patient outcomes. One study by Burn et al., found that the average LOS from 1997 to 2014 dropped from 16 days to five days, respectively. Obviously, so much has changed, and we were interested in figuring out which part of the equation between the hospital, surgeon, and patient played the largest role here.”

Researchers collected data prospectively from an institutional database on TKAs performed between Jan. 1, 2017, and April 1, 2019, including individual hospital and surgeon case volume per year. Surgeons and hospitals were stratified into three volume-based groups: low (< 10 cases per physician and < 100 cases per hospital), intermediate (10–150 cases and 100–400 cases, respectively), and high (> 150 cases and > 400 cases, respectively). The following case factors were recorded: patient demographics, medical comorbidities, year of surgery, hospital academic status, and LOS.

Dr. Gold said the researchers were surprised to find that LOS was not significantly affected by hospital (P = 0.173) or surgeon (P = 0.413) volume when adjusting for patient-, surgeon-, and hospital-related factors. Medical factors that significantly increased LOS included diabetes (β = 0.052, P < 0.001), congestive heart failure (β = 0.086, P < 0.001), peripheral vascular disease (β = 0.040, P < 0.001), chronic kidney disease (β = 0.096, P < 0.001), chronic obstructive pulmonary disease (β = 0.036, P < 0.001), and anemia (β = 0.019, P < 0.033). Hospitals with academic teaching status also had longer LOS (β = 0.155, P < 0.001).

“Our study supports that patient characteristics are the main limiting factor in decreasing LOS after TKA,” said Dr. Gold. “We hope this can drive discussion on which preoperative interventions have the highest-yield outcomes in terms of preparing patients to be successful in their postoperative course.”

Dr. Gold said, “Future studies should focus on certain interventions during preoperative medical optimization to determine how the actual positive change for each comorbidity equates to a difference in their postoperative course. Another area of future study could look at how specific hospital pre- and postoperative optimization protocols affect LOS, rather than volume. This might be a quality instead of quantity issue.”

The study is limited by its retrospective design and the fact that definitions for low-, intermediate-, and high-volume vary in the literature.

Dr. Gold’s coauthors of “Who has the Greatest Effect on Hospital Lengths of Stay after Total Knee Arthroplasty: The hospital, the surgeon, or the patient?” are Luke Garbarino, MD; Hiba Anis; Max Willinger, MD; Nipun Sodhi, MD; Jonathan Danoff, MD; Sreevathsa Boraiah, MD; Vijay Rasquinha, MD; and Michael Mont, MD.

Kaitlyn D’Onofrio is the associate editor for AAOS Now. She can be reached at kdonofrio@aaos.org.


Burn E, Edwards CJ, Murray DW, et al: Trends and determinants of length of stay and hospital reimbursement following knee and hip replacement: evidence from linked primary care and NHS hospital records from 1997 to 2014. BMJ Open 2018;27:e019146.