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Evaluation of a suspected peri-prosthetic infection by joint aspiration using a novel technique

Background: Investigation of a suspected peri-prosthetic infection post joint arthroplasty typically involves an index of clinical suspicion and the use of inflammatory markers, radiological assessment and joint aspiration. Joint aspiration remains the gold standard, but the risk of false positives limits its accuracy. We describe a novel technique of joint aspiration that addresses its inherent shortcomings by limiting the exposure to contamination by skin commensals. Methods: In a laminar airflow theatre, a spinal needle is introduced into the joint space via a truncated 5 ml syringe, (with the plunger removed). The trajectory and position of the advancing spinal needle is confirmed using intermittent anteroposterior (AP) fluoroscopy.Results: The technique described here isolates the aspirating needle and the subsequent sample(s) obtained from the skin flora, thus it also has the advantage of isolating the joint in the same manner. This technique has the added advantages of being simple, cost effective, easy to employ and easy to teach. As it is based on a simple principle it can also be modified for use in prosthetic knee aspirations or in cases where septic arthritis is suspected.Conclusions: Joint aspiration is a useful technique in providing a diagnostic sample to assist in the diagnosis of suspected joint infections. Its sensitivity is affected owing to the risk of sample contamination when obtaining the sample. This technique aims to address the shortcomings of traditional joint aspiration by isolating the aspirating needle and the subsequently obtained sample from the surrounding skin.