The femoral 3-in-1 block revisited.

STUDY OBJECTIVE

To estimate the frequency of successful conduction blockade of the femoral, lateral femoral cutaneous, and obturator nerves following a femoral 3-in-1 block.

DESIGN

Prospective observational study.

SETTING

Operating room at Royal University Hospital, Saskatoon, Saskatchewan.

PATIENTS

32 patients having lower extremity surgery.

INTERVENTIONS

Femoral 3-in-1 nerve blocks were performed on all patients.

MEASUREMENTS AND MAIN RESULTS

Sensation and motor power in all 3 nerve distributions (femoral, lateral femoral cutaneous, obturator) were assessed before and after each femoral 3-in-1 nerve block. By our criteria, the femoral nerve block was successful in 26 of 32 patients (81%). The lateral femoral cutaneous nerve was successfully blocked in 25 of 26 patients (96%). Incidentally, the saphenous nerve which is classically described as the terminal branch of the femoral nerve, was successfully blocked in 20 of 26 patients (77%). The obturator nerve block was successful in only 1 of 26 patients (4%).

CONCLUSIONS

The femoral 3-in-1 nerve block does not block the parent trunk of the obturator nerve.