AB0178 PERIARTICULAR OSTEOPHYTE FORMATION PROTECTS AGAINST TOTAL KNEE ARTHROPLASTY IN RHEUMATOID ARTHRITIS PATIENTS WITH ADVANCED JOINT DAMAGE

Abstract

Background:New medications including biologics and aggressive treatment strategies can halt the inflammatory and destructive disease processes in patients with rheumatoid arthritis (RA), and in some cases repair damaged joints. In the process of damaged joint repair, periarticular osteophyte formation might be detected radiographically (1). However, little is known about the clinical and functional role of osteophyte formation in RA joints. Total joint arthroplasty, a common procedure for treating damaged large joints, can serve as a surrogate for the long-term outcome of large joint destruction in patients with RA.Objectives:To determine the influence of periarticular osteophyte formation on the incidence of total knee arthroplasty (TKA) in patients with RA.Methods:This retrospective longitudinal study used data from a registry of patients with RA starting biologics. A flow chart summarizing the study design is shown in Figure 1. A total of 130 symptomatic (tender and/or swollen) knee joints in 80 patients were studied with a median follow-up of 12 years. All data were analyzed using the knee joint as the statistical unit of analysis. The cumulative incidences of TKA were estimated using Kaplan-Meier curves, and compared according to the presence or absence of osteophyte on plain anteroposterior radiograph [osteophyte (+/-)] and the extent of advanced joint damage as defined by Larsen’s grading system (0-II vs. III-V).Results:Baseline characteristics of all subjects included in this study are shown in Table 1. A total of 42 knees underwent TKA during the follow-up period. There was no significant difference in the cumulative incidence of TKA between the osteophyte (+) and osteophyte (-) groups (31% vs. 34% at 10 years, P=0.718) (Fig. 2A). The cumulative incidence of TKA was significantly higher for the Larsen grade III-V group compared to the Larsen grade 0-II group (56% vs. 10% at 10 years, P<0.001) (Fig. 2B). While no significant difference was observed in the cumulative incidence of TKA between the osteophyte (+) and osteophyte (-) groups in the Larsen grade 0-II group (9% vs. 10% at 10 years, P=0.774) (Fig. 2C), the cumulative incidence of TKA was significantly lower for the osteophyte (+) group compared to the osteophyte (-) group in the Larsen grade III-V group (38% vs. 74% at 10 years, P=0.010) (Fig. 2D). Multivariate analysis using Cox proportional hazards models revealed that older age [hazard ratio (HR): 1.04 per 1 year, 95% confidence interval (CI): 1.01-1.08] and osteophyte formation (HR: 0.39, 95% CI: 0.19-0.79) independently predicted TKA in the Larsen grade III-V group, whereas none of the assessed variables predicted TKA in the Larsen grade 0-II group.Table 1.Baseline characteristics by presence or absence of osteophyte formationTotalOsteophyte (+)Osteophyte (-)Characteristicsn = 130n = 44n = 86PvalueAge, years57(41-63)59(52-65)56(39-63)0.051Sex, female, n (%)108(83)40(91)68(80)0.137Body mass index21.3(19.0-23.8)21.3(18.9-24.4)21.2(19.0-23.7)0.744Disease duration, years8(3-12)9(5-18)7(3-11)0.007Larsen grade, n (%)<0.001Grade 0-II66(51)11(25)55(64)Grade III-V64(59)33(75)31(36)Osteophyte formation, n (%)44(34)---RF or ACPA positive, n (%)85(83)35(90)50(78)0.183CRP, mg/dl3.2(1.5-4.9)2.9(1.0-4.1)3.4(1.8-5.2)0.172First biologic agent, n (%)1.000Infliximab57(44)19(43)38(44)Etanercept73(56)25(57)48(56)Use of methotrexate, n (%)98(75)33(75)65(76)1.000Methotrexate dose, mg/week*8(6-10)8(6-9)8(6-10)0.104Use of glucocorticoids, n (%)79(61)22(50)57(66)0.088Glucocorticoid dose, mg/day*†5.0(5.0-7.5)5.0(5.0-5.0)5.0(5.0-7.8)0.204Data are presented as median (interquartile range) or number of subjects (percentages). *Median among subjects receiving the drug. †Prednisolone equivalent (mg/day).Conclusion:Osteophyte formation reduces the incidence of TKA in patients with RA who have advanced joint damage.