Single Shot Lumbar Erector Spinae Plane (ESP) Block in Total Hip Replacement (THR)

Total hip replacement is a common orthopaedic procedure that improves pain and mobility in a variety of pathologies like osteoarthritis, rheumatoid arthritis and avascular necrosis. Post-operative complications, for instance, venous thromboembolism and chest infection have long been documented in literature. These complications can have a bearing on long term survival, and may be prevented by early mobilisation. Therefore, pain control plays an important role in enhancing post-operative recovery, which may also shorten length of stay and reduce overall cost. Multimodal analgesia is applied to these patient, with combination of opioid, oral adjuvant and regional anaesthesia. Each of the components has its own limitation; for opioid, post-operative nausea and vomiting (PONV) and respiratory depression limits its use, and adjuvants like non-steroidal anti-inflammatory drugs (NSAID) are contraindicated in certain patient populations (renal impairment, ischaemic heart disease, coagulopathy). Various regional techniques like femoral nerve block, fascia iliaca block, lumbar plexus block, paravertebral block and epidural anaesthesia are proposed but may be limited by incomplete coverage (due to the innervation by femoral and obturator nerve for the anterior aspect of the joint and sciatic nerve for the posterior aspect, with contribution of lateral cutaneous nerve of thigh for the wound), the invasive nature of the regional technique (psoas haematoma for lumbar plexus block, epidural haematoma for epidural anaesthesia (EA)) or cardiovascular effects like hypotension from EA. Erector spinae block, first introduced by in 2016 as a chronic pain intervention, was also used in hip surgery from a case report in 2018. However, currently the evidence for lumbar ESP block is limited mainly to case reports, while randomised control trial is scarce. More concrete data are required to determine the efficacy of this novel technique. It is postulated that single shot lumbar ESP injected at L1 level can 1) reduced post-operative pain score 2) reduced post-operative 24 hour opioid (fentanyl) use. This study is conducted in Tuen Mun hospital (TMH) and Pok Oi hospital (POH) in Hong Kong. Patient are recruited for the study during pre-anaesthetic assessment, and they are counselled for risk of general anaesthesia and erector spinae plane block (i.e. local infection/bleeding, injury to neighbouring structure, local anaesthetic toxicity).