SYSTEMIC ABSORPTION OF GENTAMICIN IRRIGATION IN JOINT REPLACEMENT SURGERY: A CAUSE OF CONCERN

Abstract

Introduction: Gentamicin is one of the most commonly used antibiotics in orthopaedic practice. It is mostly used as prophylaxis either through intravenous route, incorporated into bone cement or as local irrigation intra-operatively. The former two have been well studied. However, the literature on the therapeutic efficacy and safety of gentamicin irrigation is sparse. The objective of this study is to assess the safety of gentamicin irrigation in joint replacement surgery and associated infection rate.

Methods: This is a non-randomized, prospective study whereby patients undergoing joint replacement surgery were treated with gentamicin irrigation intra-operatively. Patients with pre-existing renal impairment were excluded. Two ampoules of Gentamicin (160mg) were irrigated into the wound before implants insertion and wound closure respectively. Cefuroxime was given pro-phylactically for all patients but none of them had intravenous gentamicin. Gentamicin level in the blood was assayed at 4 hours and 24 hours post-operation.

Results: A total of 138 patients were divided into two groups in this study. Group A (98 patients) consisted of patients with Total Joint Replacement and group B (40 patients) consisted of patients with hemi- arthroplasty of the hips and shoulders. There were 16 patients in group A (16%) and 12 patients in group B (30%) found to have plasma gentamicin level above 2mcg/ml. All but 6 of them had their gentamicin level dropped to below 2mcg/ml after 24 hours. The incidence of superficial wound infection was 6.1% (6 patients) in group A. No infection was reported for group B.

Discussion: Although none of them developed systemic complications, the plasma gentamicin level is high enough to raise an alarm. In this study, there was no apparent reduction in infection rate as compared to literatures reported. However, there was significant systemic blood gentamicin absorption.