Femoral nerve block for total knee replacement — A word of caution
Introduction
Total knee arthroplasty demands excellent postoperative pain relief in order to maximise functional rehabilitation. It is standard policy in our department to mobilize patients as early as possible, usually on the 1st postoperative day. Our median length of stay is 4 days for total knee replacement (TKR). Many studies[1], [2], [3], [4], [5] have noted the superior analgesic efficacy and shortened hospital stay of patients with femoral nerve blocks (FNB) in comparison with epidural and patient controlled analgesia (PCA). Most studies also report a low incidence of complications with this technique, particularly with problems such as bladder catheterisation and nausea and vomiting. The risk of vertebral cord haematoma is also removed. However, there are also isolated reports in the literature highlighting local infection and vascular complications [6], [7] at the femoral injection site and prolonged quadriceps weakness [8], associated with an increased risk of postoperative falls [9], [10]. We report a series of five postoperative falls resulting in significant injuries to patients with femoral nerve blocks for postoperative analgesia following knee replacement surgery.
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Patients and methods
Our orthopaedic department has performed over 3000 lower limb arthroplasties in the last 3 years. The majority of these patients have been given a lumbar epidural (92%) for postoperative analgesia. However over the last few years, there has been a growing body of evidence in the literature [1], [2], [3], [4], [5] to support the use of peripheral nerve blocks instead of spinal epidural anaesthetic, thereby avoiding urinary catheterization and the rare but catastrophic risk of vertebral canal
Results
The demographic data for each patient are shown in Table 1. None of the five patients had significant co-morbidity. They all had spinal anaesthesia for their surgery and ropivacaine or levobupivacaine for their FNB. The first patient also received clonidine in the local anaesthetic infusion. They were assessed by the nursing and physiotherapy staff using a Visual Analogue Score (VAS) for pain and Bromage score[11] for mobility. All had some degree of motor blockade (able to flex the knee but
Discussion
The use of femoral nerve blocks (FNB) in our series of 250 patients has resulted in a 2% incidence (five cases) of serious postoperative falls that have not been associated with other types of regional anaesthesia in our hospital. Several other centres have published excellent results with regard to analgesia produced by FNB and, for many anaesthetists and surgeons, FNB is regarded as the analgesic of choice following knee surgery as it avoids the need for epidural analgesia [1], [2], [3], [4],
Conclusion
A review of the literature gives a positive message about FNB for post-operative analgesia. However, most studies do not mention the timing of mobilisation focussing on the quality of analgesia, rather than any other morbidity. It is our opinion that difficulties have been underestimated and if mobilisation within 24 h is proposed, then vigilance by all staff must be mandatory.
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Cited by (140)
Surgeon administered direct adductor canal block is as good as ultrasound guided adductor canal block in pain management in knee replacements- A retrospective case-control study
2022, Journal of OrthopaedicsCitation Excerpt :Epidural analgesia is associated with muscle weakness, occasional hypotension and urinary retention.6 Non-selective PNB like femoral nerve block previously used in TKR is associated with quadriceps weakness which delays mobilisation and also increases the risk of fall.7,8 Adductor canal block (ACB) has become popular due to its more selective sensory blockade and quadriceps sparing action which helps in better ambulation and early functional recovery of the patient.9,10
Editorial Commentary: Femoral Nerve Block: Don't Kill the Motor Branch
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