Continuous Femoral Nerve Block Versus Local-wound Infiltration Analgesia For Patients Receiving Total Knee Arthroplasty --- A Randomized Controlled Trial

Post-operative pain after total knee arthroplasty is usually severe and impair the functional recovery of operated joints.The purpose of this study is to determine whether post-operative continuous femoral nerve block analgesia is superior to local wound infiltration combined with intravenous patient controlled analgesia in improving joint function and reducing the incidence of chronic post-surgical pain (CPSP).

Major surgical types for knee included arthroscopy, total or partial knee arthroplastic surgery. These procedures are typically associated with severe pain. Function training, which is imperative after surgery for these patients, also aggravated pain.Post-operative pain after major knee surgery impaired post-operative knee recovery and prolonged inpatient length of stay.To maximize the efficacy and minimize the side effects of different options,a multi-modal analgesic regimen was recommended for patients underwent knee surgeries.Local wound infiltration and nerve block are given considerable attentions.Compared with systematic analgesia,nerve block with local anesthetics has been revealed to provide superior analgesia and better recovery of joint function compared with systemic analgesics. Currently,systematic evidence is sparse related to the comparative efficacy of pain control between local wound infiltration and nerve block,the investigators therefore conduct this randomized controlled trials.

This study was approved by the institutional review board of the First Affiliated Hospital of Chongqing Medical University. The protocol design is in accordance with Consolidated Standards of Reporting Trials (CONSORT) statement . This study is designed as a randomized controlled trial to compare the analgesic efficacy of continuous femoral nerve block (group CFNB) with local wound infiltration (group LWI).

Participants in group CFNB will receive a single injection for femoral nerve block intra-operatively combined with continuous femoral nerve block post-operatively guided by ultrasound and nerve stimulator.

Participants in group LWI will receive a peri-articular injection of suspension (48 ml of 0.8% ropivacaine with 2 ml of 40mg methylprednisolone) combined with intravenous non-opioid patient controlled analgesia.All participants will receive unified post-operative rehabilitation programme and the prophylaxis of infection and thrombo-embolism.

The primary outcome of this study is the incidence of chronic moderate-to-severe post-surgical pain.The secondary outcomes of this study are acute post-operative pain and rescue medication;knee function measured by WOMAC knee scores ;life ability measured by EQ-5D questionnaire;adverse events associated with the post-operative analgesia.

This study will be conducted under the supervision of an independent auditor. Every week, the auditor checked the data of the participants the day after the survey was conducted. Assessment of pain intensity and prognostic outcomes must be confirmed by the auditor in sampled population. When there is disagreement between surgeon and anesthesiologists in evaluating the prognosis of patients, the auditor must solve this disagreement by discussion with both evaluators. Data were double-entered by two statisticians with limitation of access and locked during statistical analysis.

Eligibility Criteria:
Inclusion Criteria:

* men and women over the 18 years and younger than 75 years old who had received selective unilateral knee replacement.

Exclusion Criteria:

* bilateral knee replacement
* the secondary knee revision and knee surgery not interfering with articular joint cavity (wound debridement and suture)
* American Society of Anesthesiology (ASA) classification of anesthesia risk IV and V grade; body mass index higher than 35
* coagulation dysfunction, which is assessed by activated partial thromboplastin time (APTT) higher than the upper limit by 10s
* prothrombin time (PT) higher than the upper limit by 5s
* International Normalized Ratio (INR) higher than 1.3, or any of criteria met above
* local infection of puncture sites
* neurological diseases
* uncontrolled general infection
* intra-operative cardiac arrest.