Local infiltration analgesia is a relatively novel technique developed for effective pain control following total knee replacement, reducing requirements of epidural or parenteral post-operative analgesia. The study aimed to investigate the anatomical spread of Local Infiltration Analgesia (LIA) used intra-operatively in total knee arthroplasty (TKA) and identify the nerve structures reached by the injected fluid.

Six fresh-frozen cadaveric lower limbs were injected with 180ml of a solution of latex and India ink to enable visualisation. Injections were done according to our standardised LIA technique. Wounds were closed and limbs were placed flat in a freezer at −20°C for two weeks. Limbs were then either sliced or dissected to identify solution locations.

Injected solution was found from the proximal thigh to the middle of the lower leg. The main areas of concentration were the popliteal fossa, the anterior aspect of the femur and the subcutaneous tissue of the anterior aspect of the knee. There was less solution in the lower popliteal fossa. The solution was found to reach the majority of the terminal branches of the tibial, fibular and obturator nerves.

Overall, there was good infiltration of nerves supplying the knee. The lack of infiltration into the lower popliteal fossa suggests more fluid or a different injection point could be used. The solution that travelled distally to the extensor muscles of the lower leg probably has no beneficial analgesic effect for a TKA patient. This LIA technique reached most nerves that innervate the knee joint which supports the positive clinical results from this LIA technique. However, there may be scope to optimise the injection sites.

In this study we aimed to identify which anatomical site was the most effective for methicillin resistant staphylococcus aureus (MRSA) detection within an elective orthopaedic setting. A retrospective review was performed of 13,373 elective orthopaedic patients from pre-assessment and admission screening swabs taken over a five year period (2005-2010). Swabs were taken from the nose, the axilla and either the groin or perineum. MRSA was identified in 136(1.02%) of patients. The nose was found to be positive for MRSA in 89.6% of cases identified. Therefore only 10.4% of the MRSA carriers (0.1% of all admissions) would not have been identified had a single nasal swab been taken. There was no additional benefit in swabbing the axilla. We believe that for the majority of orthopaedic elective admissions a single nasal swab should be sufficient. In hip arthroplasty patients it may be beneficial to additionally swab the groin given the close proximity of the surgical wound.