Mechanical strength of antibiotic‑loaded PMMA spacers in two‑stage revision surgery

BMC Musculoskeletal Disorders, 2022 · DOI: https://doi.org/10.1186/s12891-022-05895-5 · Published: October 14, 2022

Simple Explanation

Antibiotic-loaded PMMA bone cement spacers are used in two-stage revision surgeries for periprosthetic joint infections (PJI). They provide high local antibiotic concentrations and allow patients to move during the interim period. This study compares the mechanical characteristics of six different dual antibiotic-loaded bone cement preparations made from three different PMMA bone cements. The study aims to determine how time and antibiotic concentration affect the mechanical strength of these bone cements, which are commonly used to create spacers for two-stage revision surgeries for PJI.

Study Duration

Six weeks

Participants

84 dual antibiotic-loaded bone cement specimens

Evidence Level

Not specified

Key Findings

1
Copal G + V showed the highest bending strength after 24 hours, but after six weeks, the bending strength decreased in all preparations.
2
Low concentration preparations showed superior mechanical strength compared to high concentration counterparts.
3
Mechanical strength of antibiotic-loaded PMMA bone cement critically decreases even over the short time period of six weeks.

Research Summary

This study evaluates the mechanical strength of six different dual antibiotic-loaded bone cement (dALBC) preparations made from three commonly used PMMA bone cements (Copal spacem, Copal G + V, Palacos R + G) after 24 hours and six weeks of incubation. The results indicate that the bending strength of all tested preparations decreased after six weeks, and none of the preparations met the minimum requirement of 50 MPa according to ISO standards after this period. The study concludes that intraoperative addition of antibiotics decreases mechanical strength, and the choice of dALBC preparation should consider the balance between antibiotic concentration and mechanical stability to minimize the risk of spacer fractures.

Practical Implications

Spacer Fracture Risk

The decrease in mechanical strength over six weeks suggests an increased risk of PMMA spacer fracture, especially in patients with prolonged interim periods.

Antibiotic Concentration Impact

Higher antibiotic concentrations can reduce mechanical strength, highlighting the need to balance antibiotic efficacy with structural integrity.

Preparation Choice

Intraoperative addition of 4 g of vancomycin powder per 40 g of gentamicin-premixed Palacos R + G (Group D) may be the mechanically preferable preparation for a dual antibiotic-loaded bone cement spacer.

Study Limitations

1
The study examined rectangular PMMA specimens instead of real PMMA spacers.
2
Mechanical strength was measured by testing bending strength, which is not the only mechanical characteristic defining mechanical resilience.
3
The study was limited to three PMMA bone cements and the antibiotics gentamicin and vancomycin with only two different concentrations tested.

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