Background/Purpose: Outcomes of total knee replacements (TKR) in psoriatic arthritis (PsA) are poorly studied. Previous studies are conflicting, often not separating inflammatory PsA from osteoarthritis (OA) with cutaneous psoriasis (PsC). This study evaluates TKR outcomes in PsA compared to both PsC+OA and OA alone.

Methods: This study utilized cases from a high volume single institution TKR registry enrolled between 5/2007 and 12/2011. Potential PsA cases were identified by ICD-9 code (696.0-.1) and matched 4:1 (on age (+/- 2.5 years), primary vs. revision and date of surgery) with OA TKR.  TKR with other rheumatic diseases or fractures were excluded. Patient reported outcomes were collected at baseline and 2 years; non-responders received an additional questionnaire at 3-5 years.  Differences between groups were compared using ANOVA, and multivariate logistic regressions were performed to identify independent predictors of poor post-operative pain and function, (WOMAC < 60).

Results: 253 potential PsA were identified; 76 PsA and 155 PsC+OA were validated by chart review. Post-op. self-report data were available in 76% PsA, 74% PsC+OA and 65% OA. 2% of self-reported outcomes were elicited 3-5 years post-op.  PsA were younger than PsC+OA or OA, (p-value=0.009). PsA and PsC+OA had more co-morbidities and worse ASA class. More PsA and PsC+OA were previous smokers, more PsC+OA were current smokers. 71% of PsA were on biologics or non-biologic DMARDs compared to 5% of PsC+OA. There was no statistically significant difference in pre-or post-op WOMAC pain, WOMAC function or SF-12 physical component scores (PCS) scores between groups. Post-op. SF-12 mental component scores (MCS) scores were worse in PsA and PsC+OA (p-values=0.04). EQ-5D scores were worse both pre- and post-op. in PsA. Overall satisfaction with TKA was equally high for all groups, with > 70% being very satisfied (p-value=0.66). In a multivariate regression controlling for multiple potential cofounders, a diagnosis of PsA or PsC+OA did not statistically significantly increase the odds of either poor post-op. pain or function.  Primary TKR had much lower odds of poor post-op pain or function, and worse pre-op. function was statistically significantly associated with poor post-op. function. No other variables were significant.

Conclusion: Despite having worse pre-op. health status, patients with PsA and PsC+OA have equally good post-op. pain and function compared with OA, and are equally satisfied.  PsA have clinically significantly worse post-op. MCS.  This information should be communicated to PsA and PsC+OA patients contemplating TKR.

 

Table 1: Demographic Data		PsA (N=76)	PsC+OA (N=155)		OA (N=547)*	P-Value
Age, years (SD)		63.5 (10.5)	67.5 (9.7)		67.0 (9.7)	0.009
BMI (SD)		29.5 (5.2)	30.5 (6.1)		29.8 (7.5)	0.48
Male, n (%)		35 (46%)	68 (44%)		199 (36%)	0.09
Caucasian, n (%)		72 (95%)	150 (97%)		488 (89%)	0.007
≥College Education, n (%)		30 (71%)	60 (67%)		308 (64%)	0.59
Pre-operative WOMAC Pain (SD)		54.3 (18.6)	54.7 (16.0)		55.4 (17.2)	0.89
Post-operative WOMAC Pain (SD)		86.8 (16.1)	88.0 (16.2)		87.6 (15.8)	0.91
Pre-operative WOMAC Function (SD)		50.9 (14.4)	55.4 (15.0)		55.7 (17.5)	0.31
Post-operative WOMAC Function (SD)		84.0 (17.2)	85.7 (19.3)		86.2 (15.8)	0.68
Pre-operative SF-12 PCS (SD)		43.7 (10.3)	45.4 (9.4)		45.7 (9.8)	0.69
Post-operative SF-12 PCS (SD)		43.0 (10.6)	46.3 (9.9)		46.4 (9.9)	0.07
Pre-operative SF-12 MCS (SD)		52.0 (9.2)	48.2 (11.1)		53.1 (9.1)	0.09
Post-operative SF-12 MCS (SD)		51.8 (9.5)	51.9 (9.5)		54.1 (8.7)	0.04
Pre-operative EQ-5D Score (SD)		0.6 (0.2)	0.6 (0.2)		0.7 (0.2)	0.008
Post-operative EQ-5D Score (SD)		0.7 (0.2)	0.8 (0.2)		0.8 (0.2)	<0.001
ASA Class, n (%)						0.02
Class 1		0 (0%)	1 (1%)		16 (3%)
Class 2		52 (68%)	126 (81%)		426 (78%)
Class 3/4		24 (32%)	28 (18%)		105 (19%)
Deyo comorbidities, n (%)						<0.001
0 comorbidities		38 (50%)	109 (71%)		401 (74%)
1-2 comorbidities		36 (47%)	40 (26%)		134 (25%)
3+ comorbidities		2 (3%)	5 (3%)		10 (2%)
Do you currently smoke?, n (%)						<0.001
Yes		0 (0%)	6 (8%)		9 (2%)
No, but I smoked previously		25 (57%)	50 (66%)		268 (50%)
Never		19 (43%)	20 (26%)		257 (48%)
5 (best)		18 (45%)	32 (48%)
* 547/843 cases were available for analysis
Table 2: Predictors of Having Poor Post-Operative Pain or Function (WOMAC <60) After THR*
	Poor Post-Operative Pain WOMAC (<60) Odds Ratio (95% CI)			Poor Post-Operative Function WOMAC (<60) Odds Ratio (95% CI)
PsC+OA vs. OA	0.64 (0.08, 5.24)			1.11 (0.23, 5.54)
PsA vs. OA	0.88 (0.18, 4.26)			0.37 (0.05, 3.07)
Primary vs. Revision	0.32 (0.11, 0.99)			0.20 (0.07, 0.56)
Pre-operative WOMAC Pain	0.997 (0.96, 1.03)			1.01 (0.98, 1.05)
Pre-operative WOMAC Function	0.98 (0.94, 1.01)			0.96 (0.93, 0.998)
*Multivariate regression controlling for gender, diagnosis, BMI, number of comorbidities, primary vs. revision surgery, smoker status, pre-operative WOMAC pain and function, pre-operative MCS,

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/total-knee-replacement-outcomes-in-patients-with-psoriatic-arthritis-osteoarthritis-with-cutaneous-psoriasis-and-osteoarthritis/