Rheumatoid arthritis (RA) and other closely associated inflammatory arthropathies are well established as independent risk factors for failure following reimplantation.¹,² Compared to osteoarthritis (OA) patients, RA patients have a much higher risk of PJI following reimplantation with a hazard ratio of 5.5.³ Disease-modifying antirheumatic drugs (DMARDs) are likely to play a prominent role in this increased PJI risk and are an established risk factor for PJI in primary total knee arthroplasty (TKA) patients.⁴ Current American College of Rheumatology (ACR) and American Association of Hip and Knee Surgeons (AAHKS) recommendations state that some DMARDs should be continued during the perioperative timeframe for elective total joint arthroplasty (TJA), while biologics should be held for one dosing cycle prior to surgery and 2 weeks postoperatively.⁵ In patients undergoing reimplantation who were on DMARDs prior to explantation, it may be beneficial to withhold reimplantation until the dosing cycle of biologics is completed to minimize the risk of reinfection. It is not recommended to administer DMARDs between stages, if possible.

Diabetes is another well-established risk factor that contributes to increased reinfection after reimplantation, as Hoell et al found that diabetes was associated with an odds ratio of 6.65 for reinfection.²,⁶ Thus, we advocate that reimplantation patients establish proper glycemic control prior to reimplantation, including a hemoglobin A1C of <7.7% and a blood glucose of <200 mg/dL, which is similar to values for patients undergoing elective primary TJA.⁷

Body mass index (BMI) currently has mixed literature with regard to its role in the success of two-stage exchange arthroplasty. Some studies have demonstrated it as an independent risk, with 1 kg/m² increase in BMI leading to a 22% increase in risk of reinfection.⁶ Conversely, other studies have shown no difference in two-stage exchange arthroplasty success between high and low BMI patients.⁸ If clinically possible, it is recommended that reimplantation follow primary TJA guidelines, with a recommendation of BMI < 40 kg/m², but reimplantation should not be withheld waiting for weight loss.

Malnutrition is often overlooked and inadequately worked up, despite being an established risk factor for PJI. Although sometimes visibly evident in elderly and frail patients, many patients do not show physical signs of malnutrition. In fact, obese patients often demonstrate paradoxical malnutrition, accounting for 42.9% of malnourished patients in one study of TJA patients.⁹ Several
serum markers are well established as useful proxies for malnutrition. They include serum albumin less than 3.5 g/dL, prealbumin less than 18 mg/dL, total protein less than 6 g/dL, total lymphocyte count less than 1500 cells/mm³, and transferrin less than 200 mg/dL.¹⁰ Yi et al found that serum markers below the above-threshold values were independent risk factors for PJI in the revision setting.¹¹ As such, patients found to be preoperatively malnourished should work with a dietitian to improve their nutritional status prior to reimplantation.

There are many studies linking tobacco product use to an increased risk of PJI in primary TJA. Similarly, smoking has been shown to be a risk factor for recurrent PJI after two-stage exchange arthroplasty. One study demonstrated a 71% risk of infection with a 21.5 odds ratio of infection in patients who smoke.⁶ Smoking has been shown not only to increase the risk of reoperation for infection within 90 days of performing TJA, but also does so in a dose-dependent manner.¹² It is important to note that both current and former smokers have been shown to have increased postoperative complication risks, including PJI.¹³ Smoking cessation at least 4 to 6 weeks prior to reimplantation is necessary to restore immune function to decrease the likelihood of postoperative complications.¹⁴,¹⁵

Individual studies have found associations with a wide variety of additional patient risk factors that can broadly be grouped as either patient health factors (cardiac disease, anemia, chronic Staphylococcus carrier, culture negative PJI, and methicillin-resistant Staphylococcus aureus [MRSA] PJI) or surgical factors (postoperative hematoma, wound dehiscence, and number of previous surgeries).¹,²,⁶,⁸ Optimizing patients prior to surgery by collaborating with consulting specialists, including cardiologists, hematologists, endocrinologists, and infectious disease specialists, can be beneficial to patients prior to undergoing reimplantation surgery. Additional screening and decolonization of MRSA and methicillin-sensitive Staphylococcus aureus (MSSA) may decrease the likelihood of a subsequent S. aureus PJI.¹⁶ Modifiable surgical risk factors, such as reducing blood loss, ensuring blood salvage, and reducing transfusions, may also reduce the risk of reinfection.

Once a careful history and physical exam has been completed, serologic testing should be pursued. In contrast to
the workup for primary PJI, erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) have not been shown to be predictive of infection recurrence prior to reimplantation in a two-stage exchange arthroplasty.⁸,¹⁹,²⁰ Fu et al demonstrated a high specificity of ESR and CRP for diagnosing infection, but these same laboratory values show poor sensitivity and have limited utility for ruling out infection, which is necessary prior to reimplantation.²¹ These labs are often persistently elevated prior to reimplantation, even if the infection has been controlled.²² Stambaugh et al evaluated whether the percent change of ESR and CRP between resection and reimplantation would be more useful than an absolute threshold value, but unfortunately, no percentage of ESR/CRP reduction was predictive of recurrent PJI after reimplantation.²³ However, a combination of elevated preoperative serum ESR (>99 mm/h), synovial fluid WBC (>60,000 cells/µL), and synovial fluid polymorphonucleocytes (>92%) are predictors of failure of two-stage exchange arthroplasty, and reimplantation is not recommended if these laboratory values are present.¹⁸