DISCUSSION
Our results showed a continuous yearly increase from 2006 to 2011 in THA and TKA procedures at a rate of 36% and 34%, respectively; this result was consistent with existing literature.11 Despite a substantial increase in the amount of total THA and TKA procedures, the ratio of patients with RA undergoing these operations has decreased or remained nearly the same. Similar effects were found in Japan and the US when examining patients with RA undergoing TJA procedures between 2001 and 2007 and between 1992 and 2005, respectively.12-14 This observation may be explained by the advances and early initiation of pharmacologic treatment and the widespread use of DMARDs such as methotrexate (MTX), azathioprine, leflunomide, hydroxychloroquine, and biological response modifiers TNF-α and interleukin-1.15 These medications have drastically improved survival rates of patients with RA with impressive capabilities in symptom relief.15 With the increasing use of DMARDs and aggressive treatment early on in the disease process, patients with RA are showing markedly slow progression of joint deterioration, leading to a decreased need for orthopedic intervention compared with the general population.13,15
When analyzing the complication rates for patients undergoing TKA and THA, we observed that patients with RA exhibited a significant increase in the rates of infections, wound dehiscence, and systemic complications prior to discharge from the hospital compared with the OA population. The increased risk of infections was reported in previous studies assessing postoperative complication rates in TJA.16,17 A study utilizing the Norwegian Arthroplasty Registry noted an increased risk of late infection in patients with RA, leading to increased rates of revision TJA in comparison with patients with OA.16 Another study, which was based on the Canadian Institute for Health Information Discharge Abstract Database, showed that patients with RA are at an increased risk of infection only after THA and interestingly not after TKA.17 Although our study did not identify the causes of the increased infection rate, the inherent nature of the disease and the immunomodulatory drugs used to treat it may contribute to this increased infectious risk in patients with RA.6,18 Immunosuppressive DMARDs are some of the widely used medications employed to treat RA and are prime suspects of causing increased infection rates.15 The perioperative use of MTX has not been shown to cause short-term increases in infection for patients undergoing orthopedic intervention, but leflunomide and TNF-α inhibitors have been shown to cause a significant several-fold increase in risk for surgical wound infections.19,20
All patients with RA presented with significant increases for infection, wound dehiscence, and systemic complications, whereas only patients with RA undergoing THA showed increased risk of pulmonary and cardiovascular complications when compared with patients with OA. Surprisingly, in TKA, patients with RA were at a significantly decreased risk of cardiovascular complications. This observation was interesting due to cardiovascular disease being one of RA's most notable extra-articular features.4,21
Patients with RA undergoing TJA also showed significantly lower cerebrovascular complications than patients with OA. The significant reduction in risk for these complications has not been previously reported in the current literature, and it was an unexpected finding as past studies have found an increased risk in cerebrovascular disease in patients with RA. RA is an inflammatory disease exhibiting the upregulation of procoagulation factors,22 so we expected patients with RA to be at an increased risk for cerebrovascular and cardiovascular complications over patients with OA. Although we are unsure why these results were observed, we postulate that pharmaceutical interventions may confer some protection to patients with RA. For example, aspirin is commonly utilized in RA for its protective anti-platelet effect23 and may be a contributing factor to why we found low postoperative complication rates in cerebrovascular disease. However, the reason why aspirin may be protective against cerebrovascular and not cardiovascular complications remains unclear. Moreover, most guidelines suggest that aspirin be stopped prior to surgery.24 Although patients with RA were younger than those with OA, age was accounted for when analyzing the data.
A major strength of the study was the large sample size and the adjustment of potential confounding variables when examining the difference in complications between RA and OA. It is also a national US study that utilizes a validated database. Given that the patient samples in the NIS are reported in a uniform and de-identified manner, the database is considered ideal and has been extensively used for retrospective large observational cohort studies.25 However, the study also had some limitations due to the retrospective and administrative nature of the NIS database. Only data concerning patient complications during their inpatient stay at the hospital were available. Patients who may develop complications following discharge were not included in the data, providing a very small window of time for analysis. Another limitation with the database was its lack of ability to identify the severity of each patient's disease process or the medical treatment they received perioperatively. Finally, no patient-reported outcomes were determined, which would provide information on whether these complications affect the patients’ postoperational satisfaction in regard to their pain and disability.
CONCLUSION
As RA patients continue to utilize joint arthroplasty to repair deteriorated joints, understanding of how the disease process and its medical management may impact patient outcomes is important. This article reports significantly higher postoperational infection rates in RA than in patients with OA, which may be due to the medical management of the disease. Although new medications have been introduced and are being used to treat patients with RA, they have not altered the complication rate following TJA in this patient population. Thus, surgeons and other members of the management team should be familiar with the common medical conditions, co-morbidities, and medical treatments/side effects that are encountered in patients with RA. Future studies should delve into possible differences in long-term outcomes of patients with RA undergoing TKA and THA, as well as whether certain perioperative strategies and therapies (medical or physical) may decrease complications and improve outcomes.
This paper will be judged for the Resident Writer’s Award.