Elsevier

The Knee

Volume 16, Issue 2, March 2009, Pages 98-100
The Knee

Femoral nerve block for total knee replacement — A word of caution

https://doi.org/10.1016/j.knee.2008.10.007Get rights and content

Abstract

Femoral nerve block (FNB) is a well documented option for post-operative analgesia following major knee surgery. However, motor blockade may be prolonged preventing early mobilisation thereby increasing the length of stay. In addition, as a consequence of persistent quadriceps weakness, patients have an increased risk of falling. We present a series of five patients who underwent total knee replacement with spinal anaesthesia and FNB who fell, sustaining complete wound disruption — including a patient with peri-prosthetic fracture requiring further surgery and prolonged hospital stay.

The literature, which is largely in anaesthetic journals, reflects the high quality of analgesia of FNB but makes little or no mention of the delays or dangers in early mobilization. We believe that the potential risks to orthopaedic patients are underestimated.

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.

Section snippets

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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