Mechanical Complications of Hip and Knee Spacers Are Common.

Introduction Two-stage revision is frequently used for the treatment of periprosthetic joint infection (PJI). Because antibiotic-loaded cement spacers are constructed and implanted as temporary devices, mechanical complications are possible. The purpose of our study was to define the incidence of such mechanical complications, determine associated risk factors, and establish if such complications influence the subsequent success of PJI treatment. Methods We identified patients who received an antibiotic spacer for the treatment of PJI at a single center over a six-year timeframe. Medical records and all radiographs were collected and reviewed. Radiographic changes over time were recorded, and mechanical complications were noted. We used multivariate logistic regression analysis to assess risk factors for mechanical spacer complications and assess whether such complications influence the likelihood of subsequent reimplantation and ultimate component retention. Results A total of 236 patients were included in the study. There were 82 hip spacers (28% dynamic and 72% static) with a mechanical complication rate of 8.5% and 154 knee spacers (44% dynamic and 56% static) with a mechanical complication rate of 18.2%. Knee spacers were significantly more likely to have mechanical complications than hip spacers. Other risk factors for mechanical complications included bone loss and elevated body mass index (BMI). Bone loss and advanced age were found to be independent risk factors for failure to undergo second-stage reimplantation. Mechanical spacer failure was not an independent risk factor for the likelihood of subsequent reimplantation or ultimate component retention. Conclusions Mechanical complications of antibiotic spacers are common but do not appear to negatively impact the likelihood of subsequent reimplantation or component retention. In knee spacers and in patients with bone loss or elevated BMI, appropriate patient counseling and strategies to prevent such complications are recommended.