unable to recruit patients due to COVID19

Currently there is no consensus on the optimal peripheral nerve block for Total Hip Arthroplasty (THA). Furthermore, there is a gap in the literature in regard to the efficacy of Quadratus Lumborum Block (QLB) for Total Hip Arthroplasty via posterior approach.

This Randomised Controlled Trial aims to examine the effectiveness of anterior QLB in patients undergoing Total Hip Arthroplasty via posterior approach. The investigators hypothesise that anterior QLB and spinal anaesthesia is superior to spinal anaesthesia alone with reference to analgesic efficacy and functional ability to engage with physiotherapy in the first 24 hours postoperatively.

Adequate analgesic strategies for Total Hip Arthroplasty (THA) are of paramount importance in early rehabilitation and enhanced recovery. Ultrasound guided peripheral nerve blocks emerge as the key element of multi-modal analgesia in modern orthopaedic surgery, but in this setting, given the complex sensory innervation of the hip joint, the optimal regional technique for THA is yet to be elucidated. Many centres incorporate Suprainguinal Fascia Iliaca Block in their THA regimen. Although it confers certain benefits, its analgesic efficacy may be suboptimal for posterior approach THA, especially with regards to dermatomal sensory distribution. The Quadratus Lumborum Block (QLB) is a relatively novel technique, yet its role is already established in providing somatic and visceral analgesia for abdominal and pelvic surgery. There are case reports indicating its utility in THA; Adhikary et al. report that QLB is non inferior to Lumbar Plexus Block in terms of its analgesic efficacy, while being easier to perform and carrying less risks.

There remains some debate regarding the QLB mechanism of action. Its clinical effect may be attributed to the spread to thoracic and lumbar paravertebral spaces, spread within the thoracolumbar fascia or even direct spread to the lumbar plexus branches; perhaps all three mechanisms are involved. Thus, QLB is biologically plausible to provide analgesia without significant motor block for posterior approach THA, but for that purpose, neither the optimal volume of local anaesthetic nor the site of injection (anterior vs posterior vs lateral QLB or the vertical height of injection endpoint) have been established in the literature. Based on the available evidence, as well as experience at our institution, the investigators hypothesise, that in patients undergoing THA via posterior approach, anterior QLB at L4 level using 30 ml 0,5% ropivacaine, 100mcg dexmedetomidine and 1:200,000 adrenaline will reduce movement pain scores within the first 24hours, without clinically significant motor block.

The participants will be randomised into one of two groups using an internet based randomisation tool (https://www.randomizer.org/), and subsequently allocated to either group, with the allocation concealed in a sealed opaque envelope.

Inclusion Criteria:

• Patients undergoing unilateral total hip arthroplasty
• Adults 18 - 90 years.
• ASA classification of I, II or III

Exclusion Criteria:

• Patients with allergies to local anaesthetic
• Patients with pre-existing neurologic or anatomic deficits in the lower extremity on the side of the operation
• BMI > 40
• Extremes of stature (145cm > Height >210cm)
• Patients with co-existing coagulopathy
• Patients refusing spinal anaesthetic or regional block
• Revision hip arthroplasty
• Contraindications to spinal anaesthetic
• Unsatisfactory confirmation of the local anaesthetic spread in the interfascial plane
• Patients requiring transfusion > 2 units of Red Packed Cells in the postoperative period