Table 2

Multivariable regressions for length of stay

Primary TKR (RE (95% CI))Primary THR (RE (95% CI))Revision TKR (RE (95% CI))Revision THR (RE (95% CI))
UnadjustedAdjustedUnadjustedAdjustedUnadjustedAdjustedUnadjustedAdjusted
Year of surgery0.93 (0.92 to 0.94)0.93 (0.93 to 0.94)0.95 (0.94 to 0.95)0.94 (0.94 to 0.95)0.94 (0.90 to 0.99)0.96 (0.92 to 1.00)1.02 (0.96 to 1.07)1.02 (0.96 to 1.07)
Year of surgery*1.01 (1.00 to 1.02)1.01 (1.00 to 1.02)0.93 (0.87 to 1.00)0.91 (0.85 to 0.98)
Age1.00 (1.00 to 1.00)1.00 (1.00 to 1.01)0.99 (0.96 to 1.02)1.03 (1.02 to 1.04)
Age*1.02 (1.01 to 1.02)1.02 (1.01 to 1.02)1.03 (0.99 to 1.07)
Gender: male0.98 (0.95 to 1.00)0.94 (0.91 to 0.96)1.03 (0.78 to 1.37)0.89 (0.72 to 1.09)
Diagnosis: RA1.17 (1.11 to 1.22)1.17 (1.10 to 1.25)2.35 (1.56 to 3.68)1.35 (1.02 to 1.81)
RCS Charlson score†
 0RefRefRefRef
 11.17 (1.13 to 1.21)1.13 (1.09 to 1.18)0.89 (0.64 to 1.25)1.27 (0.98 to 1.67)
 2+1.35 (1.26 to 1.44)1.43 (1.32 to 1.55)1.49 (0.79 to 3.19)1.95 (1.31 to 3.03)
IMD quintiles
 1RefRefRefRef
 21.04 (1.01 to 1.08)1.01 (0.97 to 1.05)1.45 (0.98 to 2.15)0.92 (0.70 to 1.20)
 31.07 (1.04 to 1.11)1.02 (0.97 to 1.06)1.19 (0.80 to 1.78)0.85 (0.64 to 1.12)
 41.07 (1.03 to 1.11)1.05 (1.00 to 1.10)1.34 (0.90 to 2.02)0.90 (0.65 to 1.25)
 51.11 (1.06 to 1.16)1.12 (1.06 to 1.18)0.94 (0.53 to 1.79)0.99 (0.70 to 1.45)
  • Explanatory factors’ relative effect (RE) on days of length of stay with 95% CI from univariable and multivariable regressions. 

  • *Indicates knots for restricted cubic spline. 

  • †Rheumatoid arthritis (RA) codes were omitted from the calculation of the Royal College of Surgeons (RCS) Charlson score and groups 2 and 3+ combined into 2+.

  • IMD, Index of Multiple Deprivation; THR, total hip replacement; TKR, total knee replacement.