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. 2016 Jan 25;68(2):237–245. doi: 10.1002/acr.22656

Table 3.

SEM analysis of preoperative and acute pain and postoperative pain, using a single latent variable model of the WOMAC pain score in hip and knee patientsa

Model Exposure Adjusted β SE 95% CI P Likelihood Model DoF
THR
1 Preoperative WOMAC Confounders 0.195 0.084 0.030, 0.360 0.0206 −3951.0 64
2 VAS move Confounders 0.085 0.034 0.018, 0.153 0.0135 −7013.0 83
3 VAS rest Confounders 0.190 0.046 0.099, 0.281 0.0000 −6758.9 83
4 Preoperative WOMAC Confounders + VAS move 0.170 0.085 0.004, 0.336 0.0442 −8887.9 107
5 Preoperative WOMAC Confounders + VAS rest 0.142 0.083 −0.020, 0.305 0.0856 −8634.5 107
6 Preoperative WOMAC Confounders + VAS move + VAS rest 0.152 0.083 −0.011, 0.315 0.0675 −13482.4 151
TKR
1 Preoperative WOMAC Confounders 0.749 0.126 0.502, 0.996 0.0000 −3992.0 64
2 VAS move Confounders 0.140 0.044 0.054, 0.226 0.0014 −7114.8 83
3 VAS rest Confounders 0.222 0.058 0.109, 0.336 0.0001 −7091.3 83
4 Preoperative WOMAC Confounders + VAS rest 0.697 0.127 0.448, 0.946 0.0000 −8843.9 107
5 Preoperative WOMAC Confounders + VAS move 0.654 0.133 0.393, 0.915 0.0000 −8816.1 107
6 Preoperative WOMAC Confounders + VAS move + VAS rest 0.638 0.149 0.346, 0.930 0.0000 −13534.3 151
a

P values in structural equation modeling (SEM) models are based on z‐distributions. Confounding variables include trial randomization, education, cohabitation, employment, and sex. SEM analyses are based on one latent variable analyses of Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain items, which range from 1–5 (extreme pain to no pain); SEM models are estimated using maximum likelihood with missing values, which assumes missing data are missing at random, given other covariates. Acute pain‐on‐movement and pain‐on‐rest are modeled using a latent variable approach, where the 3 daily assessments (8:00 am, 12:00 pm, and 5:00 pm) on days 1, 2, and 3 are used to model the acute pain‐on‐movement/pain‐at‐rest latent variables. 95% CI = 95% confidence interval; THR = total hip replacement; VAS = visual analog scale; move = pain‐on‐movement; rest = pain‐at‐rest; TKR = total knee replacement.