Comparison of elution characteristics and mechanical properties of acrylic bone cements with and without superficial vancomycin coating (SVC) in the late phase of polymerization

Orthop Traumatol Surg Res. 2021 Mar 28:102908. doi: 10.1016/j.otsr.2021.102908. Online ahead of print.

ABSTRACT

INTRODUCTION: Antibiotic-loaded bone cements (ALBCs) are used as spacers in two-stage revision arthroplasty for periprosthetic joint infection. We previously described a new technique applying vancomycin powder coating to custom-made cements (superficial vancomycin coating (SVC)) but, to our knowledge, this method has not been assessed. We therefore performed an in-vitro study to determine: 1) whether manually applied SVC strengthened the cements' antibiotic effect; and 2) whether the mechanical requirements for the cements were fulfilled.

HYPOTHESIS: SVC increases the antibiotic effect of cement within the first 24 hours.

METHODS: Cuboid blocks were produced from two commercially available acrylic ALBCs (Palacos R+G and Copal G+V) with and without SVC. Each block was eluted in phosphate-buffered saline at 37°C. Eluates obtained at 1, 2, 3, 4, 5, 10, 15, 30 and 60 minutes and 3, 6 and 24 hours were evaluated against Staphylococcus aureus (Palacos, Copal) and Methicillin-resistant Staphylococcus aureus (MRSA) (Copal) using zone of inhibition tests. Mechanical test results (bending modulus, bending strength) were compared to ISO requirements (≥1,800 MPa, ≥50 MPa).

RESULTS: Palacos with SVC produced significantly greater zones of inhibition against Staphylococcus aureus than Palacos without SVC (p=0.002). Copal with SVC showed greater zones of inhibition against both Staphylococcus aureus and MRSA (p=0.002). The antibiotic effect was enhanced by SVC in both cements at every time point within 24 hours. The bending modulus and bending strength of Palacos with SVC (2,089± 166 MPa, 60.8±2.6 MPA) and Copal with SVC (2,283±195 MPa, 56.9±2.4 MPa) were significantly above ISO requirements.

CONCLUSION: SVC boosts the antibiotic effect of ALBCs in the first 24 hours, while maintaining sufficient stability. These findings endorse SVC as a promising additive in septic revision surgery.

LEVEL OF EVIDENCE: III; case control study.

PMID:33789200 | DOI:10.1016/j.otsr.2021.102908