This was a single-centre, doubleblinded, randomized comparative trial conducted at the Third Affiliated Hospital of Anhui Medical University, Hefei, Anhui, China. Before enrolment, approvals were given by the ethics committee and were registered at Clinical Trials prior to commencement (NTR; NL8043; principal investigator: Huangying; date of approval: 26 October. 2021; approved No. of ethic committee: 2021(52) ). After obtaining written informed consent, 90 patients undergoing primary total hip arthroscopy (THA) were enrolled. The inclusion criteria were as follows: (1) American Society of Anaesthesiologists (ASA) physical status I to III, (2) aged 18 years and older, and (3) patients with a hip fracture presenting for surgery.
The exclusion criteria were as follows: (1) contraindications to peripheral nerve block (e.g., allergy to lidocaine or ropivacaine, coagulopathy, infection in the injection site), (2) neurological diseases, (3) decline of cognitive state, (4) inability to communicate, (5) patients who did not cooperate with clinical follow-up, (6) opioid intake at home, (7) patients with multiple traumas, and (8) patients who had spinal anaesthesia. Eligible subjects were enrolled and allocated at random into three groups. Group A received a PENG block with 20mL ropivacaine 0.5%, Group B received 20mL ropivacaine 0.25% and Group C received 10ml ropivacaine 0.5%. Randomization was achieved using computer-generated lists in blocks of eight with a 1:1:1 ratio, and treatment allocation was concealed using consecutively numbered, sealed, opaque envelopes. The group designation data were sealed in sequentially numbered opaque envelopes, which were opened on the day of surgery by a study investigator who was then unblinded. The data collection was performed by blinded study investigators. Members of the surgical, anaesthetic, and nursing staff were blinded to the intervention, as well as the patient. To ensure blinding, the anaesthesiologist placing the block preoperatively was different from the anaesthesiologist managing the patient intraoperatively and postoperatively.
All patients were required to fast for 8 hours prior to the operation and were prohibited from taking any drugs. The patient’s various indicators were checked before surgery, and their blood pressure, heart rate and other vital signs were monitored in real time. After the patient entered the operating room, he was provided an oxygen mask, and a venous channel was established. Patients received mild sedation with administration of 1 µg/kg dexmedetomidine (Dexdor, EVER Pharma, France) in 250 mL of saline solution over 30 min. The first injection was performed at the arrival of the patient in the induction room, and the second was performed in the operating room, with an interval of 30 min between the two administrations. General anaesthesia was chosen as the main anaesthetic technique, and general anaesthesia was induced with propofol, rocuronium, and sufentanil. A supraglottic device (LMA Proseal TM) was uneventfully performed. General anaesthesia was maintained by the target-controlled infusion (TCI) of propofol in addition to remifentanil and fentanyl. After anaesthesia induction, nerve block was performed.
The PENG block, according to the technique described by Giron-Arango [7], was performed with the patient in the supine position after induction of general anaesthesia and before surgical incision. A curvilinear probe was used (80-mm Stimuplex Ultra 360, BBraun, Melsungen, Germany). Puncture was performed in a lateromedial direction until the needle tip reached the plane between the iliopsoas tendon and periosteum and between the anterior inferior iliac spine (AIIS) and iliopubic eminence (IPE). After a negative aspiration test, Group A (20 ml 0.5%), Group B (20 ml 0.25%) and Group C (10 ml 0.5%) were injected in the plane beneath the iliopsoas muscle (Fig. 1). A curvilinear low-frequency ultrasound probe (2–5 MHz) was initially placed in a transverse plane over the AIIS and then aligned with the pubic ramus by rotating the probe counterclockwise approximately 45 degrees. In this view, the IPE, the iliopsoas muscle and tendon, the femoral artery, and the pectineus muscle were observed. A 22-gauge, 80-mm needle was inserted from the lateral to medial in an in-plane approach to place the tip in the musculofascial plane between the psoas tendon anteriorly and the pubic ramus posteriorly. Following negative aspiration, the local anaesthetic solution was injected in 5-mL increments while observing for adequate fluid spread in this plane for a total volume of 20 mL. The block was always performed by the same two anaesthetists (DCS, WJ, LQ). Each had almost 5 years of postspecialization clinical experience focused on regional anaesthesia, and all had performed almost 20 PENG blocks before patient enrolment began.
All patients received 5 µg sufentanil 15 min before the end of the surgery. Postoperatively, all patients received the same multimodal analgesia, which included ketorolac 60 mg intravenous (i.v.) every 24 h and 1 g i.v. three times per day. Patient-controlled analgesia (PCA) was given using Zalvisoâ (AcelRx Pharmaceuticals, Inc., Hayward, CA, USA), a system that releases 15 mcg sublingual sufentanil tablets on demand (lockout period 20 min), the efficacy and safety profile of which has already been demonstrated [15]. All patients were trained in PCA use in the postanaesthetic care unit. All patients received paracetamol and ibuprofen at fixed doses and intervals, with morphine tablets on demand or at fixed intervals and i.v. morphine as a rescue medication.
The primary outcome was the postoperative quadriceps strength using the knee extension test [14] and Oxford muscle strength [13] grading 12, with grouped scores of intact (5/5), reduced (1–4/5) and absent (0/5) measured at 6 and 12 hours postoperatively. Knee extension was evaluated in a supine position with the patient’s hip and knee flexed at 45° and 90°, respectively. The patient was asked to extend the knee first against gravity and then against resistance. Knee extension was graded according to a 3-point scale: 0 = normal strength (extension against gravity and against resistance); 1 = paresis (extension against gravity but not against resistance); 2 = paralysis (no extension possible).
Secondary outcomes were NRS pain scores. At all postoperative time-points (0, 6, 12, 24, and 48 h after surgery), patients were asked to indicate perceived pain at rest and upon movement using a 0–10 NRS (0 no pain, 10 worst imaginable pain). In addition, recorded secondary outcomes included the first time to walk, blood pressure at T1 and T2, side effects such as nausea, vomiting and patient satisfaction on the third postoperative day. Outcome assessment was performed by the same group of three clinicians (AS, ED, CP) who were blinded to the group allocation.
The primary outcome was muscle strength. Our research hypothesis was that, compared with the high concentration/high volume group, the low concentration/low volume group would result in better postoperative movement. According to our preliminary test, the muscle strength for 10 mL of 0.5% ropivacaine was intact. We considered a time difference of 50% to be clinically relevant. To obtain a 2-tailed α error of 0.05 and a statistical power of 0.9, the calculated sample size was 30 patients per group. We recruited 33 patients per group in anticipation of 10% potential droupouts.
Data entry and statistical analyses were conducted in a blinded fashion. The analysis was performed on an intention-to-treat basis using SPSS V.27 (IBM) and GraphPad Prism V.8 (GraphPad Software, La Jolla, California, USA). The parametricity of continuous variables was determined using the Shapiro-Wilk test. Normally distributed continuous variables are expressed as the means with SD, and nonparametric variables are expressed as the medians with ranges. Univariate analysis was carried out using the χ2 test or Fisher’s exact test for categorical variables, the Mann-Whitney U test for nonparametric continuous variables and Student’s t test for parametric continuous variables. A p value of < 0.05 was considered statistically significant.