Background/Purpose: The prevalence of total knee arthroplasty (TKA) and total hip arthroplasty (THA) has risen considerably in the U.S. There has been a relative lack of investigation into the incidence of post-implant CPDD (pseudogout) at prosthetic joint sites. We retrospectively reviewed cases of post-implant pseudgout treated at our tertiary care center. All patients met the ACR criteria for pseudogout. Our goal was to describe the demographics, clinical presentation, management, and outcomes of this cohort.

Methods: All patients >18 y.o with post-implant pseudogout at a prosthesis site, who were evaluated at our medical center between January 1, 2000 and June 30, 2016, were identified. Implant associated pseudogout was defined as CPPD crystals found in synovial fluid aspirates taken from periprosthetic fluid. Variables pertaining to patient demographics, presentation, management, and outcomes were abstracted and aggregated.

Results: There were 22 patients (15 male, 7 female) who met inclusion criteria. The average age for this cohort was 71 (Range: 51-84). Nine patients had concomitant negative joint fluid cultures, while 13 patients had concomitant positive joint fluid cultures. The most common implant was TKA, accounting for 13 (59.1%) of all cases of pseudogout. The most common indication for prosthetic placement was degenerative joint disease.

Clinical presentation for patients without concomitant infection included pain (100%), swelling at the joint (88.9%), redness (33.3%), fever (22.2%), and decreased joint range of motion (100%). Findings were mostly similar for patients with evidence of concomitant infection, however none of the patients without concomitant infection exhibited tachycardia or drainage from the prosthesis site. Various management steps and findings for the cohort are summarized in the table below.

Ten patients in the overall cohort (45.5%) had either relapse or continuation of symptoms after treatment. Of the 7 patients who received subsequent surgical intervention at the affected joint, 6 had evidence of concomitant infection.

Conclusion: Our study suggests strong resemblance in presentation between post-implant pseudogout and commonly encountered PJI, based on similar exam and lab findings (pain, swelling, redness, decreased ROM, elevated ESR/CRP/PMN%). Tachycardia and purulent drainage might hold some utility in distinguishing between the two conditions. Still, more conclusive tests including synovial fluid aspiration with crystal and culture analyses are needed for this. Unfortunately, many patients receive antibiotics prior to establishment of an etiologic diagnosis, as seen in more than half of our pseudogout patients with negative synovial fluid cultures. Future research should explore paired comparisons between post-implant patients with pure pseudogout & PJI, matched on the basis of variables such as age, gender, and implant site.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/clinical-presentation-management-and-prognosis-of-pseudogout-in-prosthetic-joint-implant-patients-a-retrospective-study/