Pain Patterns in Anterior Cruciate Ligament Reconstruction, and the Utility of Sciatic Nerve Blockade for Postoperative Analgesia
Published on: 2015-02-02
Pain Patterns in Anterior Cruciate Ligament Reconstruction and the Utility of Sciatic Nerve Block for Postoperative Analgesia Introduction: In anterior cruciate ligament reconstruction (ACLR) with hamstring autograft, a significant degree of posterior knee pain is expected from the tendon harvesting procedure. However, pain patterns are not as predictable for non-hamstring ACLR. Methods: In this observational study, patients underwent general anesthesia and preoperative femoral nerve block for non-hamstring ACLR. As the primary outcome measure, we identified patients with postoperative pain scores persistently at five or above (out of 10), despite treatment with opioids, as having probable sciatic-related pain. These patients then received sciatic nerve block. Results: 10 patients (20%) out of 50 reported pain scores consistently at or above five despite at least two doses of opioids and 20 minutes in recovery. In this group, pain scores were significantly higher at 10, 20 and 30 minutes, (p<0.024) compared to those without persistent pain, but rapidly fell after rescue sciatic block, to a similar level. Pain scores at discharge and 24 hours did not significantly differ between the two groups. Conclusion: Most patients had appreciable pain on arrival in recovery; however, a subset maintained moderate level pain scores despite administration of multiple doses of opioids. These patients rapidly improved with sciatic nerve block, suggesting that a major portion of the pain was related to sciatic nerve innervation. A population-based clinical decision algorithm is proposed which would treat 50% of likely qualifiers with sciatic block within 10 minutes of admission to recovery, based on a pain score threshold of 7/10. Such an algorithm would reduce immediate postoperative opioid consumption and the duration of discomfort, while likely reducing length of stay.