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LETTER TO THE EDITOR

Peripheral Nerve Blocks for Postoperative Pain Relief After Total Knee Replacement: More Questions Than Answers

Clinical Associate Professor, Anesthesia; University of Montreal; Montreal, Quebec, Canada; joanne.guay{at}umontreal.ca

To the Editor:

Singelyn et al. (1) reported that a continuous three-in-one femoral nerve block (CFNB) would facilitate rehabilitation after total knee replacement (TKR). While some authors argue that it would be essential to add an obturator nerve block to the CFNB, others have reported that over 80% of the patients had better postoperative analgesia when a continuous sciatic nerve block is added to a CFNB (2,3).

We have compared continuous posterior lumbar (psoas compartment) blocks (CPCB) and CFNB with a simple morphine IV PCA in a randomized prospective study that included 60 patients undergoing TKR (4). The obturator nerve was blocked in a significantly higher percentage of patients with the CPCB technique (90 vs 47%), but during the first 48 h, morphine consumption was the same for the two types of continuous nerve blocks (36.1 ± 25.8 vs 37.3 ± 34.7 mg, mean ± sd). Verbal analogical pain scores measured at rest (6, 24, and 48 h) and during physiotherapy were also comparable for these two groups (4). Although our study was not designed to compare the effects of these two regional anesthesia techniques on rehabilitation, from the data that can be retrospectively retrieved from the charts of these patients one can see that the difference in the amplitude of the knee flexion between the CFNB group and the PCA group was small and did not last beyond the first few days and that there was absolutely no trend toward a faster rehabilitation in the CPCB group compared with the CFNB group (Fig. 1). Furthermore, the number of patients who achieved a 90-degree flexion at 7 days (PCA: 58.3%, CFNB: 66.7%, and CPCB: 60%) and the length of hospitalization (PCA: 7 days [5–30 days], CFNB: 7 days [5–13 days], and CPCB: 7 days [5–15 days], median [range]) was not improved by any of the two regional anesthesia techniques.

View larger version (16K): [in this window] [in a new window]   Figure 1. Effects of postoperative analgesic technique on the recovery of knee flexion after total knee replacement. Retrospective data retrieved from patients’ charts. PCA: IV morphine patient controlled analgesia (PCA) alone; CFNB: IV morphine PCA plus continuous three-in-one femoral nerve block; CPCB: IV morphine PCA plus continuous posterior lumbar plexus (psoas compartment) block. Mean ± sd.

Since there is an inherent risk of complication with any technique and because the addition of any of them would, at least theoretically, increase the number of related complications, it would appear essential to evaluate the real benefits of these proposed combinations of peripheral nerve blocks (single shot or continuous) not only in term of reduced need for opioids administration, but also in their real ability to facilitate rehabilitation.

Drs. Singelyn and Bouziz do not wish to respond.

References

1. Singelyn FJ, Deyaert M, Joris D, et al. Effects of intravenous patient-controlled analgesia with morphine, continuous epidural analgesia, and continuous three-in-one block on postoperative pain and knee rehabilitation after unilateral total knee arthroplasty Anesth Analg 1998;87:88–92.[Abstract/Free Full Text]
2. Macalou D, Trueck S, Meuret P, et al. Postoperative analgesia after total knee replacement: the effect of an obturator nerve block added to the femoral 3-in-1 nerve block Anesth Analg 2004;99:251–4.[Abstract/Free Full Text]
3. Ben-David B, Schmalenberger K, Chelly JE. Analgesia after total knee arthroplasty: is continuous sciatic blockade needed in addition to continuous femoral blockade? Anesth Analg 2004;98:747–9.[Abstract/Free Full Text]
4. Kaloul I, Guay J, Côté C, Fallaha M. The posterior lumbar plexus (psoas compartment) and the three-in-one femoral nerve block provide similar postoperative analgesia after total knee replacement. Can J Anaesth 2004;51:45–51.[Web of Science][Medline]

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