Introduction
Anterior cruciate ligament (ACL) reconstruction can cause considerable
postoperative discomfort. After ACL reconstruction, femoral nerve
blockade was reported to provide analgesia
effect[1-3]. However, many patients with femoral
nerve blockade still complained of knee pain after ACL reconstruction.
The articular branches of the tibial nerve provide sensory afferents to
the posterior knee, while the articular branches of the common peroneal
nerves contribute sensory afferents to the anterior knee. Therefore,
even in the case of a femoral nerve block (FNB), blockade of the tibial
and common peroneal nerves through a sciatic nerve block could reduce
the severity of pain in both anterior and posterior
knees[4, 5].
The analgesic benefits of adding sciatic nerve blockade to femoral nerve
blockade to knee surgeries is controversial [6-9].
Retrospective data showed that compared with FNB alone, combined
femoral-sciatic nerve blockade (CFSNB) performed before complex knee
surgery may improve analgesia and decreases opioid
consumption[10, 11]. Several recent randomized
controlled studies of total knee arthroplasty have shown that CFSNB
provides superior pain control[12, 13], and a
recent randomized controlled trial by Abdallah et
al.[4]demonstrated that CFSNB specifically reduces
posterior knee pain after total knee arthroplasty. Currently, limited
data, with only 1 randomized study, on the analgesic role of sciatic
blockade in ACL reconstruction can be found[14].
Ropivacaine, a long-acting local anesthetic, has also been used for
administering sciatic nerve blockade. Ropivacaine offers two advantages
over bupivacaine: in low doses it provides similar sensory blockade to
bupivacaine with less motor block, and its systemic toxicity will be
less[15], which can provide better conditions for
knee joint functional reconstruction after ACL surgery.
This study aims to evaluate the median effective analgesic concentration
(MEAC, EC50= effective concentration in 50% of patients) of ropivacaine
required for successful postoperatively analgesia with sciatic blockade.