Preoperative body mass index and physical function are associated with length of stay and facility discharge after total knee arthroplasty.
BACKGROUND
Hospital length of stay (LOS) and facility discharge are primary drivers of the cost of total knee arthroplasty (TKA). We sought to identify modifiable patient factors that were associated with increased LOS and facility discharge after TKA.


METHODS
Prospective data were reviewed from 716 consecutive, primary TKA procedures performed by two arthroplasty surgeons between 2006 and 2012 at a single institution. Preoperative body mass index (BMI), Veterans RAND-12 (VR-12) physical component score (PCS), and hemoglobin level were collected in addition to other adjusters. Multivariate linear and logistic models were constructed to predict LOS and facility discharge, respectively.


RESULTS
After adjustment, higher BMI was associated with increased LOS in a dose-response effect: Compared to normal weight (BMI <25) overweight (25-29.9) was associated with longer LOS by 0.32days (P=0.038), class-I obesity (30-34.9) by 0.33days (P=0.024), class-II obesity (35-39.9) by 0.67days (P=0.012) and class-III obesity (>40) by 1.15days (P<0.001). Class-III obesity was associated with facility discharge (odds ratio=2.08, P=0.008). Poor PCS was associated with increasing LOS: compared to PCS≥50, PCS 20-29 was associated with a LOS increase of 0.40days (P=0.014) and PCS<20 with a LOS increase of 0.64days (P=0.031).


CONCLUSIONS
Patient BMI has a dose-response effect in increasing LOS. Poor PCS was associated similarly with increased LOS. These associations for of BMI and PCS suggest that improvement preoperatively, by any amount, may potentially translate to decreased LOS and perhaps lower the cost associated with TKA.
Department of Orthopaedics, Dartmouth-Hitchcock Medical Center, 1 Medical Center Drive, Lebanon, NH 03756, USA. Electronic address: MProhaska@Gmail.com.
Matthew G
MG
Prohaska
Department of Orthopaedics, Dartmouth-Hitchcock Medical Center, 1 Medical Center Drive, Lebanon, NH 03756, USA; Geisel School of Medicine, Dartmouth College, 1 Rope Ferry Road, Hanover, NH 03755, USA. Electronic address: Benjamin.J.Keeney@Hitchcock.org.
Benjamin J
BJ
Keeney
Geisel School of Medicine, Dartmouth College, 1 Rope Ferry Road, Hanover, NH 03755, USA. Electronic address: Haaris.Beg@NYUMC.org.
Haaris A
HA
Beg
Department of Orthopaedic Surgery, Hospital for Special Surgery, 535 E. 70th Street, New York, NY 10021, USA. Electronic address: SwarupI@HSS.edu.
Ishaan
I
Swarup
Department of Orthopaedics, Dartmouth-Hitchcock Medical Center, 1 Medical Center Drive, Lebanon, NH 03756, USA; Geisel School of Medicine, Dartmouth College, 1 Rope Ferry Road, Hanover, NH 03755, USA. Electronic address: Wayne.E.Moschetti@Hitchcock.org.
Wayne E
WE
Moschetti
Department of Orthopaedics, Dartmouth-Hitchcock Medical Center, 1 Medical Center Drive, Lebanon, NH 03756, USA; Geisel School of Medicine, Dartmouth College, 1 Rope Ferry Road, Hanover, NH 03755, USA. Electronic address: Stephen.Kantor@NewLondonHospital.org.
Stephen R
SR
Kantor
Department of Orthopaedics, Dartmouth-Hitchcock Medical Center, 1 Medical Center Drive, Lebanon, NH 03756, USA; Geisel School of Medicine, Dartmouth College, 1 Rope Ferry Road, Hanover, NH 03755, USA. Electronic address: TomekI@APDMH.org.
Ivan M
IM
Tomek
D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee; D015992:Body Mass Index; D015897:Comorbidity; D005260:Female; D006454:Hemoglobins; D006801:Humans; D007902:Length of Stay / Q000706:statistics & numerical data*; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000453:epidemiology*; D010351:Patient Discharge; D011446:Prospective Studies; D012047:Rehabilitation Centers / Q000706:statistics & numerical data; D012866:Skilled Nursing Facilities / Q000706:statistics & numerical data; D000069341:Transitional Care / Q000706:statistics & numerical data; D014481:United States / Q000453:epidemiology
D006454:Hemoglobins
Body mass index; Facility discharge; Length of stay; Physical function; Total knee arthroplasty