Abstract
Purpose
Femoral nerve block (FNB) following total knee arthroplasty (TKA) has had mixed results with some studies reporting improvement in pain and reduced narcotic exposure while others have not shown substantial differences. The effect of a FNB on rehabilitation indices (quadriceps strength, knee flexion) is also unclear.
The study purpose was to compare the effect of FNB+ a multimodal analgesic protocol (MMA) to MMA only on the 1) development of a complete quadriceps motor block and 2) knee flexion during the first two postoperative days and 3) knee flexion out to 12 weeks after primary TKA. Secondarily, we compared hospital length of stay (LOS), postoperative pain, analgesic use and the incidence of nausea/vomiting.
Method
This was a controlled clinical trial undertaken at two tertiary hospitals that do high annual TJA volumes (>200 cases). Both hospitals followed the same regional clinical pathway for preoperative, perioperative and postoperative care. The pathway started mobilization on the day of surgery with a goal for discharge home on the third postoperative day.
At one site, FNB was used for the first two postoperative days in addition to MMA as needed (FNB group [n=19]) while the other site used standardized MMA (MMA group [n=20]) only.
The presence of a complete quadriceps block, knee flexion, pain, analgesic use, incidence of nausea and vomiting were recorded daily in hospital. Hospital LOS was also recorded and knee flexion and pain were assessed at two, six and 12 weeks post discharge.
Results
The groups were similar preoperatively in terms of age (p=0.27), gender (p=0.34), preoperative function (p=0.63) and knee flexion (p=0.83).
In the FNB group, 10 (52%) had a complete quadriceps motor block on the day of surgery and 13 (68%) on the first postoperative day compared with no complete motor blocks in the MMA group (p<0.001).
Pain and analgesic use was similar between groups (p>0.21) as was the incidence of nausea/vomiting (p>0.66). Knee flexion was similar at discharge(p=0.87) and at all post-discharge visits (p>0.14). Median LOS was 4(Interquartile range [IQR] 4,5) days and 3.5(3,4) days in the FNB and MMA groups respectively (p=0.04).
Conclusion
The addition of a FNB to a MMA regimen did not confer advantages in pain control, analgesic use, nausea/vomiting or knee flexion. FNB significantly increased the likelihood of a complete quadriceps motor block in the initial postoperative period. Hospital LOS was also increased in the FNB group. These results are inconsistent with previous reports of FNB benefits, but may reflect the heterogeneous nature of clinical practice among centres, evolution of pain management into MMA techniques (+/− FNB) and the trend to shorter LOS and more aggressive postoperative rehabilitation. Further, multiple practitioners with varying experience performed the FNB. A randomized trial is needed to compare current MMA protocols to controlled FNB technique when an accelerated postoperative rehabilitation program is utilized.
