Pre-operative Femoral Nerve Block in Hip Arthroscopy—A Retrospective Review of 108 Consecutive Cases

OBJECTIVES: To evaluate the safety and efficacy of pre-operative femoral nerve block for post-operative pain control in patients undergoing hip arthroscopy. METHODS: A retrospective chart review of 108 consecutive hip arthroscopy cases (in 103 patients) was carried out. All patients underwent hip arthroscopy at a single academic centre by two orthpaedic surgeons with advanced fellowship training in hip arthroscopy. All patients underwent arthroscopy under general anaesthetic with our without pre-operative femoral nerve block. Patients were separated into two groups based on the presence or absence of a pre-operative femoral nerve block prior to induction of general anesthesia. Groups were compared with respect to patient gender, age, body mass index (BMI), ASA Physical Status classification, procedure performed, operative time, total intra-operative morphine-equivalent dose, post-anesthesia care unit (PACU) pain scores (0 to 10) recorded at 0, 15, 30, 45, and 60 minutes post-operatively, total PACU morphine-equivalent dose, presence of nausea or vomiting in the PACU, time to discharge from PACU, oxycodone consumption in the surgical day care unit (SDCU), and highest pain score (0 to 10) in the SDCU prior to discharge. RESULTS: Twelve cases were excluded from analysis for a total of 96 cases (in 92 patients). Forty patients had general anesthesia alone (Group A) and 56 patients had a pre-operative femoral nerve block prior to the induction of general anesthesia (Group B). There was no significant difference between the groups with regard to gender, age, weight, height, BMI, ASA classification, or type of procedure performed. Patients who received a femoral nerve block had a significantly shorter operative time and received a significantly lower total intra-operative morphine-equivalent dose than those patients who did not receive a block. Post-operative pain scores were lower at all time points for the femoral nerve block group, however statistical significance was seen only at the 60 minute post-operative time point (p < 0.05). Patients who did not receive a block had significantly higher morphine-equivalent doses in the PACU. There was no difference in rates of nausea and vomiting and time to discharge from the PACU between the two groups. Oxycodone consumption in the surgical day care unit (SDCU) was similar between groups, but the femoral nerve block patients had significantly lower pain scores prior to discharge from the SDCU. Two patients in Group A group were admitted to hospital post-operatively due to inadequate post-operative pain control. No complications were noted in any patient with regard to the femoral nerve block. CONCLUSION: A pre-operative femoral nerve block is a safe procedure that may decrease the requirement for intra-operative morphine while providing effective post-operative pain control in patients undergoing hip arthroscopy.