Hip replacement surgery is one of the most common elective surgeries in Canada and with this surgery, there is considerable pain after the operation. By decreasing the amount of pain after surgery, the patients may be able to move and walk quicker, resulting in easier physiotherapy sessions, shorter hospital stays and may help to avoid adverse outcomes like nausea and vomiting and being overly sedated. By using ultrasound guided femoral nerve block, it may be an alternative for pain management with minimal side effects for patients having hip replacement surgery.

Ultrasound guided femoral blocks have been studied since the late 90's. A study published in 1997 by Marhofer et al. pointed that ultrasound guidance in a 3-in-1 block (femoral, obturator, lateral cutaneous nerves), improved the quality of the sensory block and reduced the onset time when compared with a nerve-stimulation technique in patients undergoing hip surgery after trauma.(13) In a meta-analysis comparing ultrasound guidance versus electrical nerve-stimulation for peripheral nerve blocks, the authors reported a decreased risk of block failure, shorter procedure time and faster onset time when ultrasound is used.(14)

A systematic review studying the outcomes after Total Hip Arthroplasty concluded that when compared with systemic analgesia the use of femoral nerve block was on unclear benefit.(15) Separate analysis of the two studies included showed that in the Biboulet study, ultrasound was not used to perform the blocks, and pain with activity was not evaluated in the first 24 hours after surgery, time in which the maximum benefit of blocks is observed.(16) In the second study by Singelyn et al. with continuous femoral nerve block, the authors found similar pain relief than with IV Patient Controlled Analgesia morphine with fewer side effects.(17)

While recent publications have demonstrated the analgesia effectiveness of femoral nerve block and fascia iliaca block for hip fractures,(18) there are not references in the literature analyzing the effectiveness of a single shot, ultrasound-guided, femoral nerve block in primary hip arthroplasty. This fact opens up the possibility to continue researching the analgesic effectiveness of this block in a population where the options for handling postoperative pain are limited widely for its side effects together with the use of anticoagulant and anti-thrombotic therapy.

This technique is considered a simple procedure, easy to teach and to learn. If our study shows improvement of the outcomes, it will feasible to incorporate this block as an alternative for pain management after primary hip arthroplasty.

Given the complexity of this proposed randomized-controlled trial, a pilot study was deemed necessary to find out the feasibility and safety of the intervention, rate of patient recruitment and needs for additional personnel.

Inclusion Criteria:

1. Patients 18 years or older undergoing unilateral hip arthroplasty.
2. Patient capable to complete informed consent.

Exclusion Criteria:

1. Pediatric population.
2. Inability to complete informed consent.
3. Patient refusal.
4. Contraindication for regional anesthesia: coagulopathy, anticoagulant use, bleeding disorders, local or systemic infection, local anesthesia allergy.
5. Presence of neuromuscular deficit including diabetic peripheral neuropathy.