New component spacer for knee infection may reduce infection, improve functional outcomes
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Results showed a new femoral component antibiotic spacer for knee periprosthetic joint infection had similar infection control rates, increased knee range of motion and improved ambulatory status compared with contemporary counterparts.
“The optimal antibiotic spacer type to treat a periprosthetic joint infection of the knee is still unknown. Our study retrospectively examined three types of contemporary antibiotic spacers used at a single institution and found no difference in infection control rates. However, the spacer consisting of a new femoral component mated to an all-polyethylene tibial component demonstrated some functional advantages,” Andrew M. Schneider, MD, a resident physician in the department of orthopedic surgery at Loyola University Medical Center, told Healio. “Additionally, the potential of this spacer type of be used in a single-stage exchange arthroplasty for infection makes it an appealing area for future investigation. Future randomized controlled trials are needed to help provide more clarity and evidence-based recommendations.”
Schneider and colleagues separated 96 patients who underwent removal of a total knee arthroplasty with insertion of an antibiotic spacer for knee periprosthetic joint infection into groups based on whether they received an articulating new femoral component spacer and a new all-polyethylene tibial component (n=30), an articulating cement-on-cement spacer (n=19) or a static spacer (n=47).
Results showed an overall infection control rate of 77%, with infection control rates of 80% for patients with a new femoral component spacer, 68% for patients with a cement-on-cement spacer and 79% for patients with a static spacer at a mean follow-up of 46.8 months. Before replantation, researchers found patients with a new femoral component spacer had higher total range of motion vs. patients with a cement-on-cement spacer. However, range of motion was not statistically significantly different between the three groups at 8 weeks after replantation, according to results.
Researchers noted 89% of patients with a new femoral component spacer ambulated independently or used a cane 8 weeks after replantation, while 67% of patients with a cement-on-cement spacer and 44% of patients with a static spacer used a walker or wheelchair. After controlling for sex and Charlson Comorbidity Index, results showed patients with a new femoral component spacer were 19.20 times more likely than patients with a cement-on-cement spacer and 6.23 times more likely than patients with a static spacer to have better ambulatory function 8 weeks after second-stage surgery. However, researchers found no differences between the three groups at final follow-up.
Perspective
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As we all know, periprosthetic joint infection is a devastating complication following TKA. Patients with an antibiotic spacer awaiting reimplantation often have prolonged periods of immobilization and protected weight-bearing, lengthy stays at rehabilitation facilities and high rates of medical complications. The authors present their results of a novel technique using new primary knee components implanted with high-dose antibiotic cement as an articulating spacer, finding improved range of motion and early ambulatory status. Another recent randomized trial also found improved range of motion and functional outcomes with articulating spacers over static spacers, however patients are still limited in weight-bearing with most conventional articulating knee spacers due to potential for fracture of the cement molds. New knee components allow for a low-friction bearing surface to facilitate range of motion and early weight-bearing. Although concerns exist regarding infection eradication with a metal prosthesis as a spacer, Nicholas M. Brown, MD, and colleagues found no difference in recurrent periprosthetic joint infection rates at 1 year postoperatively. While further prospective study is needed with a larger sample size, this method has shown promising results and has become my preferred spacer technique.
Reference:
Nahhas CR, et al. J Bone Joint Surg Am. 2020;doi:10.2106/JBJS.19.00915.
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