Commentary Questions Prolonged Gentamicin Release From Ceramic Bone Grafts

A commentary in The Journal of Bone and Joint Surgery questions the assumption that antibiotic-loaded ceramic bone grafts maintain sustained local gentamicin delivery for 28–42 days. It discusses a murine mass-balance study by Berthelsen et al., supported by reanalysis of published rabbit data, examining antibiotic release kinetics rather than patient outcomes. Sample sizes are not provided in the supplied text.

The commentary reports that more than 98% of loaded gentamicin was released within 6 hours and more than 99% within 24 hours. Mathematical modeling showed that even instantaneous release could appear to maintain concentrations above the minimum inhibitory concentration for more than 30 days when assays replaced only 20% of the medium daily. Rabbit explant data reportedly showed approximately 1% residual antibiotic, while a separate porcine osteomyelitis model demonstrated biofilm on gentamicin-loaded ceramic beads within 10 days.

The author argues that an early burst may suit gentamicin’s concentration-dependent activity but should not be equated with weeks of protection for retained hardware or residual infected bone. The commentary also highlights reported acute kidney injury after antibiotic-loaded calcium sulfate implantation in patients with limited renal reserve. These findings support scrutiny of release assays and marketing claims, but animal kinetics do not establish the duration of clinical protection or justify changes to systemic antibiotic treatment. The proposed 24-hour adjunctive role remains an interpretation requiring clinical validation.