Intraosseous Administration of Prophylactic Cefazolin in Total Shoulder Arthoplasty

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Aim: To determine whether intraosseous (IO) administration of prophylactic cefazolin achieves higher tissue concentrations than IV administration in total shoulder arthroplasty. Relevance: Propionibacterium Acnes has been shown to be responsible for up to 56% of shoulder infections after orthopaedic implant. Recently papers came out revealing that higher cefazolin and vancomycin concentrations were found in tissue after IO administration rather than IV. This was associated with less colony forming units in a murine model and thus theoretically more effective at reducing infection rates. This was also the case in revision TKA where the tourniquet is down for significant periods. As such, we aim to determine whether this is the case in TSA where no tourniquet is used. Design: Randomised Control Trial Method: Patients undergoing TSA will be randomly allocated to either IV or IO prophylactic antibiotic administration groups using computer generated random allocations placed in numbered, opaque, sealed envelopes. Patients will be randomised in the pre-operative area to allow appropriate setup in the operative room. Upon signing consent, the patients will be asked to complete a demographics survey. The data collected from this survey will be filed electronically using numbers for patients, the number each patient is assigned will be filed safely. Both IV and IO groups will receive 600mg of Lincomycin as per usual TSA prophylaxis. The IV group will receive 1g Cefazolin at this time (60-30mins prior to incision). The IO group will receive 1g Cefazolin as a bolus in 50mL through in intraosseous cannula, placed in the greater tuberosity of the humerus, after draping and before skin incision. The cannula will be removed and skin incision will follow immediately (<1min). TSA will proceed as usual and cancellous bone and subcutaneous fat samples will be taken at the following four steps. First subcutaneous fat sample immediately after skin incision, then cancellous bone and subcutaneous fat samples at the time of humeral head removal and glenoid reaming, and the final subcutaneous fat sample immediately before closure. It should be noted that 0.5-1cm2 of each sample will be placed into sterile 15mL tubes kept in ice and water within a biochemical container. The bone samples will come from bone that is removed usually during TSA. A total of two bone samples and four fat samples will be taken from each patient. Patients will be monitored and followed up as per normal TSA protocol. The biochemical container will be kept in -80-90 degrees Celsius to ensure degradation of cefazolin does not occur prior to analysis. The biochemical container will be transported to Griffith University Gold Coast where analysis via high performance liquid chromatography will be used to determine the cefazolin concentrations of the samples. The laboratory staff will only know the number that the samples belong to and no patient information or the group they belong to will be known.

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