Why are we doing this study? People who have knee replacement surgery often feel pain afterward. Doctors use different methods to control this pain. One method is an injection of numbing medicine directly into the knee during surgery, called local infiltration analgesia (LIA). Another method uses a thin tube (catheter) placed near nerves in the leg to continuously deliver numbing medicine, called a nerve block. This study compares these two pain control methods after knee replacement surgery, to find out whether the injection method (LIA) works at least as well as the nerve block method for controlling pain. Who can take part in this study? Adults aged 18 to 90 years who need a first-time (primary) knee replacement because of knee arthritis can take part. Participants must be able to walk before surgery, be in generally stable health, and be able to give informed consent. People with a knee injury (rather than arthritis), people who use a wheelchair, and people unable to give consent were not included. What happens during this study? 78 participants were randomly assigned, like a coin flip, to receive either the injection into the knee (LIA) or the nerve block through a catheter for pain relief after surgery. Both groups also received the same standard pain medicines by mouth or vein as needed. Researchers measured pain levels using a 0-10 pain scale before surgery and at 24, 48, 72, and 96 hours afterward. They also measured knee movement (range of motion), how much extra pain medicine was needed, and how satisfied participants were with their pain control. The study took place at one hospital, the Elisabethinen Hospital in Klagenfurt, Austria, between June 2025 and January 2026.
This is a prospective, randomized, open-label, controlled non-inferiority trial conducted at a single center (Department of Orthopedics and Traumatology, Elisabethinen Krankenhaus Klagenfurt). The trial compares two established postoperative analgesic techniques for primary total knee arthroplasty (TKA): local infiltration analgesia (LIA) versus continuous peripheral regional anesthesia via femoral and sciatic nerve block. Both techniques are already in routine clinical use; this trial was designed to determine which approach provides superior or at least non-inferior pain control at this institution. Hypothesis: The investigators hypothesized that LIA is not inferior to peripheral regional anesthesia with regard to postoperative pain control, measured on a 100 mm Visual Analogue Scale (VAS) 48 hours after surgery (VAS48). A non-inferiority margin of 10 mm was pre-specified, based on published minimal clinically important difference (MCID) estimates for postoperative pain on the VAS (approximately 8-40 mm across systematic reviews, with common MCID estimates near 10 mm). Non-inferiority is concluded if the upper limit of the one-sided 97.5% confidence interval of the mean difference (LIA minus nerve block) is below this margin. Sample size: Assuming a between-group mean difference of 0 mm and a combined standard deviation of 15 mm (derived from comparable published TKA analgesia trials), a sample of 37 patients per group provides 80% power (one-sided alpha = 0.025) to demonstrate non-inferiority. Accounting for an anticipated 5% drop-out rate, 78 patients were enrolled in total. Randomization and blinding: Patients were allocated 1:1 to the LIA or nerve block group using the institutional randomization tool of the Medical University of Graz. The trial is open-label; blinding of the anesthetic technique was not feasible given the distinct procedural nature of the two interventions. In addition to the primary pain endpoint, the trial captures postoperative opioid consumption, range of motion (knee flexion, measured by goniometer) during early mobilization, and overall patient satisfaction with perioperative care and pain management, assessed using a standardized questionnaire (Anästhesiologischer Nachbefragungsbogen, ANP) at 24 and 96 hours postoperatively. Data were collected between June 2025 and January 2026. No external funding or commercial sponsorship was involved; statistical analysis was performed by the investigator.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
SUPPORTIVE_CARE
Masking
NONE
Enrollment
78
Continuous peripheral regional anesthesia via ultrasound-guided femoral and sciatic nerve catheters, placed intraoperatively. Under general anesthesia, each catheter received an initial bolus of 15 mL mepivacaine 1.5% plus 10 mL ropivacaine 0.375%; under spinal anesthesia, an initial 15 mL normal saline (0.9%) test bolus confirmed catheter position, followed by 10 mL ropivacaine 0.375% once sensory block began to wear off. A continuous perineural infusion of ropivacaine 0.2% was then maintained via infusion pump for 48 hours postoperatively: 5 mL/h for the first 24 hours, reduced to 3 mL/h thereafter. Patients could additionally self-administer a 5 mL bolus every 30 minutes as needed. Catheters and the infusion pump were removed at 48 hours postoperatively.
Periarticular local infiltration analgesia administered intraoperatively during total knee arthroplasty, comprising 150 mL ropivacaine 2 mg/mL (from a 200 mL preparation, first 50 mL discarded), 30 mg ketorolac (1 mL of 30 mg/mL solution), and 0.5 mg epinephrine hydrochloride (0.5 mL of 1 mg/mL solution). The combined solution was injected periarticularly by the operating surgeon as a single intraoperative dose during wound closure. Total ropivacaine dose did not exceed the maximum recommended dose of 300 mg. No repeat dosing was administered postoperatively for this arm.
Elisabethinen Krankenhaus Klagenfurt
Klagenfurt, Carinthia, Austria
Postoperative Pain Intensity at 48 Hours (VAS Score)
Pain intensity measured with the Visual Analogue Scale (VAS), a 0-10 point scale where 0 indicates no pain and 10 indicates the worst pain imaginable (higher scores indicate worse pain), assessed at rest, at night, and during mobilization 48 hours after total knee arthroplasty. This measure was used to test non-inferiority of LIA versus peripheral regional (femoral/sciatic nerve block) anesthesia against a pre-specified non-inferiority margin.
Time frame: 48 hours postoperatively
This platform is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional.