Patients with Rheumatoid Arthritis Are More Likely to Have Pain and Poor Function After Total Hip Replacements than Patients with Osteoarthritis

Susan M. Goodman; Danielle N. Ramsden-Stein; Wei-Ti Huang; Rebecca Zhu; Mark P. Figgie; Michael M. Alexiades; Lisa A. Mandl

doi:10.3899/jrheum.140011

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Table 1.

Patient characteristics.

Characteristics	OA, n = 5473	RA, n = 193	p
Age, mean (SD)	62.8 (11.6)	63.3 (13.6)	0.51
Female, n (%)	2613 (48)	147 (77)	< 0.001
BMI, mean (SD)	28.2 (5.4)	27.7 (6.6)	0.33
Length of stay, days, mean (SD)	4.6 (1.3)	5.1 (2.1)	< 0.001
Expectation score, mean (SD)	83.6 (16.2)	80.0 (18.3)	< 0.001
College degree or higher, n (%)	3834 (70)	71 (37)	< 0.001
Race, n (%)			< 0.001
White	5031 (92)	147 (76)
Asian	37 (1)	3 (2)
African American	194 (4)	20 (10)
Other/Mixed	39 (1)	8 (4)
Deyo-Charlson comorbidities, n(%)			< 0.001
0	4296 (79)	60 (31)
1+	1131 (21)	131 (68)
ASA class, n (%)			< 0.001
Class 1 or 2	4575 (83)	124 (64)
Class 3 or 4	895 (17)	69 (36)
Previous hip replacement, n (%)	953 (20)	31 (27)	0.06
Back pain at baseline, n (%)	2294 (45)	41 (35)	0.04
DMARD		41.5%
TNFi		28.5%
Non-TNF biologics		5.2%
Corticosteroid		8.3%
None		16.6%

Values in bold face are statistically significant. OA: osteoarthritis; RA: rheumatoid arthritis; BMI: body mass index; ASA: American Society of Anesthesia; DMARD: disease-modifying antirheumatic drugs; TNFi: tumor necrosis-α inhibitors.

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Table 2.

RA responders versus nonresponders.

	Responders, n = 134	Nonresponders, n = 59	p
Age, yrs, mean (SD)	62.9 (13.5)	64.3 (13.8)	0.52
BMI, kg/m², mean (SD)	27.5 (6.4)	28.4 (7.0)	0.42
Length of stay, days, mean (SD)	4.9 (1.7)	5.7 (2.7)	0.01
Female, n (%)	100 (76)	47 (80)	0.55
ASA class 1 and class 2, n (%)	91 (67)	33 (56)	0.20
White, n (%)	106 (79)	41 (69)	0.44
Baseline WOMAC pain	44.7 (20.4)	55.0 (63.6)	0.49
Baseline WOMAC function	38.4 (19.4)	55.9 (62.4)	0.23

BMI: body mass index; ASA: American Society of Anesthesia; WOMAC: Western Ontario and McMaster Universities Osteoarthritis Index.

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Table 3.

Baseline and 2-year outcomes. Data are mean (SD) unless otherwise indicated.

	OA, n = 5473	RA, n = 193	p
WOMAC baseline pain (SD)	53.2 (17.9)	44.8 (21.1)	< 0.001
WOMAC 2-yr pain (SD)	94.0 (11.2)	88.4 (17.1)	< 0.001
WOMAC > 10, pain, n (%)	3549 (96)	72 (94)	0.35
WOMAC baseline function (SD)	49.9 (18.6)	38.7 (20.3)	< 0.001
WOMAC 2-yr function (SD)	91.8 (12.5)	82.9 (19.6)	< 0.001
WOMAC > 10, function, n (%)	3071 (94)	63 (95)	0.69
Poor pain at 2 yrs, WOMAC pain ≤ 60, n (%)	122 (3)	10 (12)	< 0.001
Poor function at 2 yrs, WOMAC function ≤ 60, n (%)	152 (4)	16 (19)	< 0.001
SF-12 PCS baseline (SD)	33.9 (8.4)	29.3 (7.9)	< 0.001
SF-12 PCS at 2 yrs (SD)	50.1 (9.3)	40.8 (13.0)	< 0.001
SF-12 MCS baseline (SD)	50.1 (12.5)	46.4 (13.6)	< 0.001
SF-12 MCS at 2 yrs (SD)	54.1 (8.8)	52.1 (10.9)	0.05

OA: osteoarthritis; RA: rheumatoid arthritis; WOMAC: Western Ontario and McMaster Universities Osteoarthritis Index; SF-12: SF-12 Short Form Health Survey; PCS: physical component scale; MCS: mental component scale.

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Table 4.

Predictors of having poor pain or function (WOMAC < 60) 2 years after hip replacement^* (logistic regression results).

	Poor WOMAC Pain at 2 Yrs, OR (95% CI)	p	Poor WOMAC Function at 2 Yrs, OR (95% CI)	p
Age	0.99 (0.97, 1.01)	0.14	1.01 (0.99, 1.00)	0.34
Female vs male	1.06 (0.61, 1.83)	0.36	1.25 (0.69, 2.26)	0.46
RA vs OA	3.22 (1.29, 8.07)	0.01	4.32 (1.57, 11.89)	0.005
Back pain vs no back pain	1.25 (0.75, 2.08)	0.30	1.62 (0.93, 2.82)	0.08
25 ≤ BMI < 30 vs 18.5 < BMI < 25	0.91 (0.48, 1.73)	0.78	1.36 (0.65, 2.84)	0.42
30 ≤ BMI < 35 vs 18.5 < BMI < 25	0.94 (0.46, 1.93)	0.87	1.64 (0.75, 3.56)	0.22
35 ≤ BMI < 40 vs 18.5 < BMI < 25	0.42 (0.13, 1.31)	0.13	0.78 (0.23, 2.66)	0.70
BMI > 40 vs 18.5 < BMI < 25	1.30 (0.44, 3.85)	0.63	2.93 (0.95, 8.99)	0.06
Preoperative WOMAC pain	0.99 (0.97, 1.01)	0.17	1.01 (0.98, 1.03)	0.71
Preoperative PCS	0.95 (0.91, 0.99)	0.01	^**	^**
Preoperative WOMAC function	^**	^**	0.96 (0.94, 0.99)	0.03
Preoperative MCS	0.96 (0.94, 0.98)	0.0002	0.98 (0.96, 0.999)	0.04
Education: college vs no college	0.83 (0.49, 1.41)	0.56	0.74, (0.43, 1.30)	0.30
White vs other	0.46 (0.23, 0.92)	0.02	0.66 (0.30, 1.47)	0.31
Expectation score	^**	^**	0.97 (0.96, 0.99)	0.0005
Deyo: 0 comorbidities vs 1–3+	^**	^**	0.80 (0.44, 1.47)	0.47
ASA class 2 vs ASA class 1	1.01 (0.37, 2.74)	0.99	^**	^**
ASA class 3+ vs ASA class 1	2.11 (0.67, 6.59)	0.20	^**	^**
Previous hip replacement vs no
previous replacement	1.37 (0.75, 2.50)	0.30	1.35 (0.72, 2.53)	0.35

↵* Multivariate regression controlling for age, sex, diagnosis, BMI, education, race, back pain, previous hip replacement, preoperative WOMAC pain and function, preoperative MCS and PCS, expectations score, ASA class, and number of Deyo comorbidities.
↵** Variable excluded because of nonconvergence of logistic model. WOMAC: Western Ontario and McMaster Universities Osteoarthritis Index; RA: rheumatoid arthritis; OA: osteoarthritis; BMI: body mass index; PCS: physical component scale; MCS: mental component scale; ASA: American Society of Anesthesia.

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Table 5.

Satisfaction at 2 years.

	OA, n = 5473	RA, n = 193	p
Very/Somewhat satisfied with pain relief, n (%)	3710 (97)	72 (94)	0.43
Very/Somewhat satisfied with improved ability to do recreational activities, n (%)	3470 (92)	60 (79)	0.002
Very/Somewhat satisfied overall, n (%)	3676 (96)	69 (90)	< 0.001
Great/moderate improvement in quality of life, n (%)	3436 (89)	63 (79)	< 0.001

OA: osteoarthritis; RA: rheumatoid arthritis.

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Table 6.

Predictors of having poor pain (WOMAC < 60) 2 ys after hip replacement^* for patients with and without previous hip replacement (logistic regression results).

	Poor WOMAC Pain at 2 Yrs Without Previous Hip Replacement, OR (95% CI)	p	Poor WOMAC Pain at 2 Yrs With Previous Hip Replacement, OR (95% CI)	p
Age	0.99 (0.96, 1.02)	0.46	0.98 (0.93, 1.04)	0.54
Female vs male	1.02 (0.54, 1.91)	0.96	1.06 (0.33, 3.37)	0.93
RA vs OA	3.17 (1.06, 9.53)	0.04	4.00 (0.72, 22.33)	0.11
Back pain vs no back pain	1.17 (0.65, 2.11)	0.59	1.63 (0.54, 4.89)	0.38
25 ≤ BMI < 30 vs 18.5 < BMI < 25	0.87 (0.42, 1.78)	0.70	1.23 (0.27, 5.54)	0.79
30 ≤ BMI < 35 vs 18.5 < BMI < 25	0.93 (0.42, 2.07)	0.85	1.07 (0.19, 6.16)	0.94
35 ≤ BMI < 40 vs 18.5 < BMI < 25	0.35 (0.09, 1.32)	0.12	0.74 (0.07, 8.00)	0.81
BMI > 40 vs 18.5 < BMI < 25	0.65 (0.16, 2.72)	0.55	5.61 (0.78, 40.27)	0.09
Preoperative WOMAC pain	0.98 (0.97, 1.00)	0.19	1.00 (0.96, 1.04)	0.86
Preoperative PCS	0.94 (0.89, 0.99)	0.01	0.96 (0.88, 1.05)	0.39
Preoperative MCS	0.96 (0.94, 0.98)	0.0009	0.96 (0.92, 1.01)	0.10
Education: college vs no college	0.83 (0.46, 1.51)	0.55	0.74 (0.24, 2.30)	0.61
White vs other	0.59 (0.26, 1.32)	0.20	0.20 (0.05, 0.85)	0.03
ASA class 2 vs ASA class 1	0.84 (0.30, 2.36)	0.74	^**	0.96
ASA class 3+ vs ASA class 1	1.89 (0.56, 6.34)	0.30	^**	0.95

↵* Multivariate regression controlling for age, sex, diagnosis, back pain, BMI, preoperative WOMAC pain and function, preoperative MCS and PCS, education, race, expectations score, ASA class, number of Deyo comorbidities, and previous hip replacement.
↵** Variable excluded because of nonconvergence of logistic model. WOMAC: Western Ontario and McMaster Universities Osteoarthritis Index; RA: rheumatoid arthritis; OA: osteoarthritis; BMI: body mass index; PCS: physical component scale; MCS: mental component scale; ASA: American Society of Anesthesia.