Background/Purpose: To study the standardized incidence ratio (SIR), time trend and risk factors of AVN in patients with SLE.

Methods:

The records of all patients who fulfilled >=4 ACR criteria for SLE between 1999 and 2014 were reviewed.  Patients who developed AVN at any sites ever since the diagnosis of SLE were identified.  SLE controls who did not have AVN were randomly selected from our cohort database in a 4:1 (control/case) ratio, matched for age, sex and SLE duration.  The SIR of AVN in SLE and its time trend was calculated by data retrieved from our hospital clinical information registry and the Census data from our Government.  Risk factors for AVN in SLE were studied by multivariate logistic regression.  A propensity score derived from a separate logistic regression model for the probability of use of high-dose prednisolone (>0.8mg/kg/day) therapy according to the prevalence of different SLE manifestations was used for adjustment.

Results:

55 patients with symptomatic AVN were identified (87% women; age 33.4±12.4 years; SLE duration 61.2±62.2 months) and were matched with 220 control SLE patients without AVN.  The point prevalence of AVN in our SLE cohort (N=743) was 7.4%.  All the patients with AVN had been treated with glucocorticoids (GCs).  Compared to controls, AVN patients had used a longer duration of steroid (51.4±61.2 vs 45.6±46.8 months; p=0.45) and a significantly higher cumulative doses of prednisolone (16.5±14.6 vs 10.7±11.3 grams; p=0.003).  The SDI damage score was also significantly higher in AVN patients than controls (3.5±1.8 vs 0.4±0.9; p<0.001).  A total of 104 sites of AVN were diagnosed in 55 patients (69% >=2 sites; 12.7% >=3 sites; 5.4% >=4 sites and 1.8% >=5 sites).  The hip was the most commonly affected region (82%), followed by the femoral condyle (9%) and the humeral head (5%).  Bilateral involvement was present in 67% cases. Surgical treatment (core decompression, vascularized bone graft or joint replacement) was performed in 41% of patients.  The age and sex stratified SIRs of AVN in our SLE patients was 131 (86.6-199; p<0.001) in the period 1995-2004 and 56.0 (34.3-91.4; p<0.001) in the period 2005-2014.  In both decades, the age stratified SIR was highest in the youngest age group (<19 years of age).  Logistic regression revealed the following factors independently associated with AVN, adjusted by the propensity score for high-dose prednisolone: preceding septic arthritis of the involved joint (odds ratio [OR] 15.4[1.3-181.2]; p=0.03), Cushingoid body habitus (OR 2.3[1.0-5.1]; p=0.043), LDL-cholesterol level (OR 1.4[1.0-2.0];p=0.041), maximum daily dose of prednisolone (mg/kg) (OR 6.0[1.2-30.7];p=0.031) and cumulative dose of prednisolone in the first 6 months of treatment of a SLE flare (OR 1.4[1.0-1.8];p=0.047).

Conclusion:

AVN is prevalent in SLE patients, particularly in younger patients.  The use of GCs remains the strongest independent factor associated with AVN.   Cushingoid body habitus, serum LDL-cholesterol level and preceding septic arthritis of the involved joints are independently associated with AVN.  There is a trend of reduction in the SIR of AVN in our SLE patients over the past 2 decades, which is probably attributed by the more judicious use of GCs and the early administration of GC-sparing agents.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/standardized-incidence-ratio-sir-time-trend-and-risk-factors-of-avascular-bone-necrosis-avn-in-patients-with-systemic-lupus-erythematosus-sle/