Chronic bone infections and infected fractures are often treated with excision of the dead bone and implantation of biomaterials which elute antibiotics. Gentamicin has been a preferred drug for local delivery, but this could induce renal dysfunction due to systemic toxicity. This is a particular concern in patients with pre-existing chronic renal disease treated with new antibiotic carriers which achieve very high peak levels of gentamicin in the first few days after surgery.
163 patients (109 males; average age 51.6 years) with Cierny-Mader Type 3 or 4 chronic osteomyelitis had a single-stage operation with excision of the dead bone, filling of the osseous defect with a calcium sulphate-hydroxyapatite carrier, containing gentamicin and immediate soft tissue closure2. No patient was given systemic gentamicin or other renal toxic antibiotics.
Mean carrier volume was 10.9mls (range 1–30mls) and mean gentamicin dosing was 190.75mg (maximum 525mg). Seven patients had pre-existing renal disease (4 diabetic nephropathy, 1 nephrotic syndrome, 1 renal transplant and 1 previous acute kidney injury).
Serum creatinine levels were collected pre-operatively and during the first seven days post-operatively. Glomerular filtration rate (GFR) was calculated using the CKD-epi creatinine equation. Renal function was defined using the Chronic Kidney Disease (CKD) Staging system.
155 cases had adequate data to allow calculation of pre- and post-operative GFR. Pre-operative CKD staging demonstrated 118 Class I (normal renal function), 30 Class II, 3 Class IIIa, 3 Class IIIb, and 1 Class V disease. Mean pre-operative GFR (99.7ml/min/1.73m2, SD 21.0) was no different to post-operative GFR (103.2ml/min/1.73m2, SD 21.3), p= 0.0861.
Four cases had a >10% decline in GFR below normal, with only one case dropping a CKD stage, from I (normal) to II (mildly decreased).
Only 1/7 cases with pre-existing renal disease had a GFR drop of >10% (from 11ml/min/1.73m2 to 8ml/min/1.73m2).
70/155 (45.2%) had a temporary GFR drop post-operatively, with the biggest drop occurring a mean 3.06 days following surgery (SD 2.1).
No patient had clinical signs of new acute renal impairment post-operatively.
Renal function is not significantly affected by local implantation of gentamicin up to 525mg. The presence of pre-existing renal disease is not a contraindication to local gentamicin therapy.