Comparison of post operative analgesia with two concentrations of ropivacaine (0.1% and 0.2%) for suprainguinal fascia iliaca block in patients undergoing primary hip arthroplasties: a randomised controlled study

**Title:**Comparison of Postoperative Analgesia with two concentrations of Ropivacaine for Suprainguinal Fascia Iliaca Block (SIFIB) in patients undergoing Primary Hip Arthroplasties: A Randomised Controlled Study

Rationale: Hip arthroplasties are one of the most common surgeries performed worldwide for improved functioning of the diseased hip. Patients should be provided proper pain relief post surgery to facilitate early mobilization to enhance recovery. Multimodal analgesic regime using analgesic medications along with fascial plane blocks have become popular. However, higher concentrations of local anaesthetic used for fascial blocks may result in motor blockade and may hamper early rehabilitation. Lower concentration of local anaesthetics which provide effective analgesia which limits the use of opioids is still under research.

AIM: To compare postoperative analgesia with 0.1% and 0.2% ropivacaine for SIFIB in patients undergoing primary hip arthroplasties.

 OBJECTIVES:

To compare postoperative analgesia with 0.1% and 0.2% ropivacaine for SIFIB in patients undergoing primary hip arthroplasties in terms of:

·       **Primary Objective:**NRS Score at 24 hours after surgery

·       Secondary Objectives:

1. Analgesia quality

2. Motor strength

3. Ambulation

Methods: This prospective, randomised controlled study will be done after approval from the Institutional Ethics Committee – Human Research (IEC-HR) between July 2025 to December 2026. Consenting adults of ASA I/II with age > 18 years scheduled for hip replacement (hemi/total) under subarachnoid block (SAB) will be included. Participants will be randomly allocated to Group R1 (0.1% ropivacaine) or Group R2 (0.2% ropivacaine). After standard pre and peri operative measures, a Sub Arachnoid Block (SAB) will be given for the surgery to take place. After closure of incision, a USG guided Suprainguinal Fascia Iliaca Block (SIFIB) with 40 ml ropivacaine – 0.1% or 0.2% (depending on the allotted group) will be given. Quality of analgesia, motor strength and ambulation will be observed uptil 72 hours after surgery.

Sample size: Sample size was estimated based on the study conducted by Albertz et al34 where the NRS score at 24 h postoperatively was 3.91 +/-1.64 with 0.2% ropivacaine via SIFIB. In the absence of a study on comparison of post operative pain scores with 0.1% and 0.2% ropivacaine, and presuming that the pain score would be 2 points higher with 0.1% ropivacaine, to estimate the outcome of interest at two tail alternative hypothesis, level of significance 5% and margin of error 10%, a minimum sample of 50 is required in each group. However, because of time constraints, we propose to include 20 patients in each group, i.e. 40 patients.

Statistical Analysis: All the data collected will be managed using MS Excel. The normality of the continuous data will be assessed using Kolmogorov Smirnov Test. The quantitative data will be represented as mean (standard deviation) or median (interquartile range), depending upon normality and categorical data will be represented as frequency (percentage). The comparison between the two independent groups will be done using the Independent T Test / Mann Whitney Test, based on the results of normality. Chi square test will be used for comparison of categorical variables. The threshold of statistical significance is p<0.05. All the analysis will be performed using SPSS.