SNOWMASS, COLO. – Total knee replacement surgery rates in patients with systemic lupus erythematosus jumped sixfold nationally during a recent 15-year span – and buried within this statistic is some very good news.
The sharp rise in total knee replacement (TKR) among systemic lupus erythematosus (SLE) patients has been driven by a hefty increase in operations performed for osteoarthritis, while TKR for active SLE in the knee has declined. These trends reflect the increased longevity of patients with SLE resulting from improved medical management. For the first time, large numbers of SLE patients are surviving to an age when they, like other Americans, are more vulnerable to osteoarthritis, Dr. Susan M. Goodman explained at the Winter Rheumatology Symposium sponsored by the American College of Rheumatology.
Dr. Susan M. Goodman
"Lupus is no longer the highly mortal disease that it was," she observed. "Clearly, patients are surviving and – I don’t know how else to put it – they’ve become middle-aged women who are having knee replacements, which is kind of a success."
She presented highlights of a soon-to-be-published study involving analysis of 10 state databases including nearly 2.8 million arthroplasties performed during 1991-2005. The rate of TKR in SLE patients climbed sixfold from 0.03 per 100,000 population in 1991 to 0.18 per 100,000 in 2005. Meanwhile, total hip replacement (THR) in SLE patients showed a modest but statistically significant increase from 0.11 to 0.18 cases per 100,000.
The proportion of lupus patients undergoing arthroplasty for avascular necrosis fell from 53% in 1991 to 24% in 2005, while the proportion undergoing arthroplasty because they developed osteoarthritis went from 23% to 61%.
Virtually all of the increase in total arthroplasties among SLE patients occurred in women aged 45 years and older. Their rate more than tripled during the study years, going from 0.076 to 0.271 cases per 100,000. Rates in female SLE patients aged 44 years and younger actually took a significant drop from 0.073 to 0.067 per 100,000. Rates in males aged 44 and younger remained flat over time, while men aged 45 and up showed a modest increase from a low baseline rate of 0.009 cases per 100,000 in 1991 to 0.034 per 100,000 in 2005, according to Dr. Goodman, a rheumatologist at the Hospital for Special Surgery and Cornell University, New York.
The proportion of TKRs among all arthroplasties performed in SLE patients increased from 16% in 1991 to 48% in 2005. Meanwhile, THRs decreased from 66% of all arthroplasties to 40%. Other joint replacements didn’t change much over time.
A particularly striking finding in the study was that the mean age at the time of arthroplasty in SLE patients increased by nearly a decade – 47.3 years in 1991 to 56.8 years in 2005. In contrast, the mean age at arthroplasty for osteoarthritis patients without SLE decreased from 71.5 to 69.0 years.
Dr. Goodman turned to additional studies by her research group and other investigators to provide a picture of arthroplasty outcomes in SLE patients.
In-hospital postoperative mortality was found to be increased in SLE patients, compared with rheumatoid arthritis patients or controls undergoing TKR or THR in a study of more than 1.5 million TKRs and THRs included in the Nationwide Inpatient Sample for 1993-2006. The Nationwide Inpatient Sample is the largest all-payer inpatient health care database in the United States.
In a multivariate logistic regression analysis adjusted for comorbidities, hospital type, and other potential confounders, investigators at Stanford (Calif.) University found that SLE patients undergoing THR had a 3.5-fold increased risk of death, compared with controls. This was driven by a 4.9-fold increased death risk in SLE patients undergoing nonelective THR or TKR, typically because of a fracture. In contrast, the rate of in-hospital death following TKR or THR in rheumatoid arthritis patients wasn’t significantly different from controls. The one comorbidity present on admission that was associated with markedly increased postoperative mortality was renal disease in SLE patients (J. Rheumatol. 2010;37:1467-72).
"Baseline renal dysfunction really seems to be a marker in lupus patients for bad perioperative outcome," Dr. Goodman observed, adding that there is a need for "increased vigilance" regarding this comorbidity.
A study of 57 SLE patients and 107 age-matched osteoarthritis patients who underwent THR at the Hospital for Special Surgery demonstrated that the lupus patients had more baseline comorbidities as reflected in their mean Charlson Comorbidity Index of 1.9, compared with 0.3 in the osteoarthritis group. Seventy-nine percent of the SLE patients, but none of the osteoarthritis patients, were on immunosuppressant therapy. The lupus patients had a 19% incidence of postoperative major adverse events, including deep vein thrombosis, arrhythmia, acute renal insufficiency, or additional surgery, compared with a 6% rate in the osteoarthritis group. The 6-day mean length of stay in the SLE group was a full day longer than that of the osteoarthritis patients, according to Dr. Goodman.