Relationships between post operative pain management and short term functional mobility in total knee arthroplasty patients with a femoral nerve catheter: A preliminary study

BACKGROUND Effective pain management following total knee arthroplasty (TKA) is fundamental in achieving positive rehabilitation outcomes. The purpose of our study was to investigate post operative pain management in relation to short term functional mobility in an intervention group receiving concomitant use of an IV narcotic PCA and a continuous infusion of local anaesthetic via a femoral nerve catheter (CFNC), compared to a group receiving narcotic PCA alone. This was a preliminary study conducted to establish an appropriate design for a larger investigative study. METHODS A prospective design was used to measure the effect of a CFNC on post operative pain management and functional mobility prior to hospital discharge. The amount of fentanyl used, pain and nausea scores, timed up and go (TUG) tests and active range of knee movement (AROM) were used to compare a CFNC and supplemental narcotic patient controlled analgesia (PCA) group (n = 27) with a PCA only group (n = 25). RESULTS The CFNC group used significantly less fentanyl than the PCA only group (p < .001) but there was no significant difference in TUG times between the two groups. There was however a significantly lower AROM reported for both extension (p < .04) and flexion (p < .006,) in the FNC group. Women had significantly slower TUG times (p < .005,) and there were moderate to strong positive correlations between post operative TUG times and the preoperative TUG time (r(s) = .505 p < .001), the time since oral analgesia (r(s) = .529 p < .014), and pain scores (r(s) = .328, p = .034) CONCLUSIONS In this small preliminary study improved TUG performance at Day 4 post op was not influenced by the use of a CFNC but was positively correlated with male gender, preoperative performance, time elapsed since last oral analgesia and pain score. However AROM was decreased in the CFNC group suggesting further research on the relationship between CFNCs, local anaesthetic concentration and quadriceps strength should be incorporated in the follow up study's design.