Antiinflammatory effect of peripheral nerve blocks after knee surgery: clinical and biologic evaluation

Abstract

Background: Nerve blocks provide analgesia after surgery. The authors tested whether nerve blocks have antiinflammatory effects.

Methods: Patients had combined sciatic (single-shot) and continuous femoral block (48 h) (block group) or morphine patient-controlled analgesia after total knee arthroplasty. Pain at rest and upon movement was monitored at 1 (D1), 4 (D4), and 7 days (D7) and 1 (M1) and 3 months (M3) after surgery. Knee inflammation was evaluated (skin temperature, knee circumference) before surgery and at D1, D4, D7, M1, and M3. Plasma cytokine concentrations (interleukin [IL]-6, IL-1beta, tumor necrosis factor [TNF], IL-10, soluble receptor 1 of TNF [sTNF-R1]) were measured before surgery and at 4 h, D1, D4, and D7 after surgery. Capsule and synovial membrane cytokines were measured (IL-6, TNF, IL-1, IL-10). Knee flexion was evaluated before surgery and at D1, D4, D7, M1, and M3. Morphine use and recovery time to autonomy were monitored.

Results: Pain at rest and upon movement was lower in the block group than in patient-controlled analgesia patients between D1 and D7 (analysis of variance, P < 0.005). Knee flexion was improved in the block group for D1 to M1 (analysis of variance, P < 0.0001). Block group patients recovered nonassisted mobilization (t test, P = 0.04) and toilet use (t test, P = 0.03) more rapidly. Knee circumference and skin temperature were lower in the block group between D1 and D7 (analysis of variance, P < 0.05). Synovial membrane IL-1 (P < 0.05) and IL-10 (P < 0.01) increased, and plasma IL-6 and sTNF-R1 peaked at 24 h, with no difference between groups.

Conclusion: Nerve blocks inhibited clinical inflammation after total knee arthroplasty, with no change in tissue and plasma cytokine concentrations.

Figure 1. time course of visual analog pain score

Visual anolog pain scores at rest (A) and when moving (B) at one (D1), four (D4), seven days (D7), and one (M1) and three months (M3) after surgery. Values are expressed as mean ± SEM. Block group: patients treated by combined sciatic (single shot) and femoral (continuous for 48 hours after surgery) nerve blocks PCA group: patients treated by morphine patient-controlled analgesia Pain was reduced in patients from the block group between D1 and D7 at rest (Anova; group effect; p=0.005). Post hoc analysis showed significant differences at D4 (t test; p = 0.01) and D7 (t test; p = 0.002) between the two patient groups. Pain when moving was reduced in the block group between D1 and D7 (Anova; group effect; p = 0.0005) (Figure 1B). Post hoc analysis showed significant differences at D1 (t test; p = 0.003), D4 (t test; p = 0.002) and D7 (t test; p = 0.001) between patient groups. **: t test p < 0.01; ***: t test p < 0.001

Figure 2. time course of knee flexion and patient autonomy

Postoperative knee flexion (degree) at one (D1), four (D4), seven days (D7), and one (M1) and three months (M3) after surgery (A). Patient autonomy as assessed by time taken (days after surgery) to stand up with assistance, stand up without assistance, use the toilets with assistance and use the toilets without assistance (B). Block group: patients treated by combined sciatic (single shot) and femoral (continuous for 48 hours after surgery) nerve blocks PCA group: patients treated by morphine patient-controlled analgesia Block group patients had a more rapid recovery in terms of operative knee flexion between D1 and M1 (Anova; group effect; p = 0.0001) (Figure 2A). Post hoc analysis showed significant differences at D1 (t test; p = 0.0001), D4 (t test; p = 0.0004), D7 (t test; p = 0.009) and M1 (t test; p = 0.01). **: t test p < 0.01; ***: t test p < 0.001 Patients in the block group gained autonomy in terms of non assisted mobilization and use of the toilets more rapidly than patients from the PCA group. *: t test p < 0.05

Figure 3. time course of operative knee circumference

Knee circumference was measured by a thread, to the nearest half centimeter, at the middle of the patella, before surgery (D0), then at one (D1), four (D4), seven days (D7), and one (M1) and three months (M3) after surgery. The increase in circumference of the operated knee, for D1 to D7 was significantly smaller for the block group than for the PCA group (Anova; interaction between group × time; p = 0.01). Post hoc analysis showed significant differences at D1 (t test; p = 0.02) and D7 (t test; p = 0.02). There was no change in knee circumference for the contralateral knee. Values are expressed as mean ± SEM. Block group: patients treated by combined sciatic (single shot) and femoral (continuous for 48 hours after surgery) nerve blocks PCA group: patients treated by morphine patient-controlled analgesia *: t test p < 0.05

Figure 4. time course of operative knee skin temperature

Skin temperature of the operated knee was measured with a Thermopoint device (Protechnique, Quebec, Canada) (in degrees Celcius) at the middle of the patella before surgery (D0), then at one (D1), four (D4) and seven days (D7), and one month (M1) and three months (M3) after surgery The increase in temperature of the operated knee, for D1 to D7, was significantly smaller in the block group than in the PCA group (Anova; interaction between group and time p = 0.03). Post hoc analysis showed significant differences at D4 (t test; p = 0.01) and D7 (t test; p = 0.02). There was no significant change in skin temperature of the contralateral knee. Values are expressed as mean ± SEM Block group: patients treated by combined sciatic (single shot) and femoral (continuous for 48 hours after surgery) nerve blocks PCA group: patients treated by morphine patient-controlled analgesia *: t test p < 0.05; **: t test p < 0.01

Figure 5. time course of plasma IL6 and sTNF-R1 levels

IL6 (A) and sTNF-R1 (B) plasma levels before surgery (D0), then at four hours (H4) and one (D1), four (D4) and seven days (D7) after surgery. Values are expressed as mean ± SEM Block group: patients treated by combined sciatic (single shot) and femoral (continuous for 48 hours after surgery) nerve blocks. PCA group: patients treated by morphine patient-controlled analgesia. pg/ml: picogram of cytokine per milliliter of plasma We did not observe significant differences between the groups. IL6: interleukin 6 sTNF-R1: soluble receptor 1 of tumor necrosing factor