Paper of the week: Patient-Related Risk Factors for Periprosthetic Ankle Joint Infection: An Analysis of 6977 Total Ankle Arthroplasties

Alyssa Althoff, BS; Jourdan M. Cancienne, MD; Minton T. Cooper, MD; Brian C. Werner, MD

J Foot Ankle Surg. 2018 Mar – Apr;57(2):269-272.
Doi: 10.1053/j.jfas.2017.09.006. Epub 2017 Dec 15.

Summary by Daniel O. Corr, BS

Total ankle arthroplasty (TAA) continues to be a procedure performed with increased frequency. As anatomic and biomechanical implant design has developed, the procedure offers an increasingly efficient means of preserving joint motion and functionality for patients diagnosed with end-stage arthritis of the ankle versus a joint fusion procedure.^1-5 While the prospects of this constantly developing procedure are enticing, it also brings with it the increased possibility of postoperative periprosthetic joint infection (PJI).⁶ As with any joint arthroplasty procedure, it is necessary to understand the patient factors associated with increased risk of PJI. Specifically for TAA it is imperative to gather more patient data from larger patient cohorts as the procedure becomes more common, as previous studies have often been limited by the size of their patient pools.⁷

Althoff et al. performed a large retrospective evaluation of TAAs from 2005 to 2012 using a national insurance claim-based database. The insurance database was used to identify patient demographic risk factors for PJI within 3 and 6 months of the index procedure. This database includes patient demographic and procedure volume data from several different insurers including Medicare and private insurers. Using CPT and ICD-9 procedure codes, the authors identified 6,977 patients undergoing primary TAA while excluding those undergoing revision procedures.

The study found a 6-month infection rate of 4.2% and several independent patient risk factors for PJI, which were largely similar for both the 3 month and 6 month endpoint. Risk factors for the primary endpoint of 6-month infection included BMI >30 (OR=1.47; 95% CI 1.15-1.87), BMI <19 (OR=2.67; 95% CI 1.07-6.67), tobacco use (OR=1.44; 95% CI 1.08-1.92), inflammatory arthritis (OR=1.67; 95% CI 1.28-2.18), peripheral vascular disease (OR=2.46; 95% CI 1.87-3.22), and hypothyroidism (OR=1.32; 95% CI 1.03-1.69).  

The authors conclude that it is imperative to evaluate patients and understand these risk factors for infection in the preoperative setting, especially since surgical site infection associated with TAA has been reported to result in implant failure 80.6% of the time.⁶ The study, while presenting a large cohort, is limited in its use of an administrative database. Operative time, surgical approach, and tourniquet time could not be assessed as the data was not available. In addition, the 6 month endpoint may have excluded additional viable patients, but was used because the authors felt less certain that longer-term infection diagnosis could be directly attributed to the primary TAA.

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