title: An anatomic study of local infiltration analgesia in total knee arthroplasty.
abstract: BACKGROUND
  Local infiltration analgesia (LIA) is a relatively novel technique developed for effective pain control following total knee arthroplasty (TKA), reducing requirements for epidural or parenteral postoperative analgesia. This study investigated the anatomical spread of an LIA used in TKA to identify the nerve structures reached by the injected fluid.
  
  
  METHODS
  Six fresh-frozen cadaveric lower limbs were injected according to a standardised LIA technique with a solution of latex and India ink to enable visualisation. Wounds were closed and limbs placed flat in a freezer at -20°C for two weeks. Limbs were then either sliced or dissected to identify solution locations.
  
  
  RESULTS
  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 nerves, with good infiltration of nerves supplying the knee.
  
  
  CONCLUSIONS
  These results support the positive clinical outcomes with this LIA technique. However, the lack of infiltration into the lower popliteal fossa suggests more fluid or a different injection point could be used. The solution reaching the extensor muscles of the lower leg is likely to have no beneficial analgesic effect for a TKA patient. The LIA technique is already used in clinical practice following total knee arthroplasty. Results from this study show there may be scope to optimise the injection sites in LIA technique.
authors.affiliation: Laboratory of Human Anatomy, University of Glasgow, Glasgow, G12 8QQ, United Kingdom.
authors.forename: M
authors.initials: M
authors.lastname: Quinn
authors.forename: A H
authors.initials: AH
authors.lastname: Deakin
authors.forename: D A
authors.initials: DA
authors.lastname: McDonald
authors.forename: I K T
authors.initials: IK
authors.lastname: Cunningham
authors.forename: A P
authors.initials: AP
authors.lastname: Payne
authors.forename: F
authors.initials: F
authors.lastname: Picard
mesh_terms: D000701:Analgesics, Opioid / Q000008:administration & dosage; D000772:Anesthesia, Local / Q000379:methods*; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects* / Q000379:methods; D002102:Cadaver; D002244:Carbon; D004396:Coloring Agents; D006801:Humans; D007270:Injections, Intra-Articular; D015552:Injections, Intralesional; D007719:Knee Joint / Q000033:anatomy & histology* / Q000187:drug effects; D007840:Latex; D010149:Postoperative Pain / Q000188:drug therapy; D012680:Sensitivity and Specificity
chemical_list: D000701:Analgesics, Opioid; D004396:Coloring Agents; D007840:Latex; C028433:chinese ink; D002244:Carbon
keywords: Cadaveric; Enhanced recover programmes; Local infiltration analgesia; Total knee arthroplasty