PENG Block Optimization: Volume and Dexamethasone Effects

The pericapsular nerve group (PENG) block has become a widely used motor-sparing component of multimodal analgesia for total hip arthroplasty (THA). However, its optimal formulation-particularly the volume of local anesthetic and the role of adjuvants-remains undetermined. This prospective, double-blind, randomized controlled trial evaluates the influence of ropivacaine volume (10 mL vs. 20 mL of 0.2%) and the addition of perineural dexamethasone (4 mg) on analgesic efficacy, opioid consumption, systemic inflammation, and quadriceps strength preservation.

A total of 120 adult patients undergoing unilateral THA under spinal anesthesia were randomized to one of four PENG block groups:

Group 1: 20 mL of 0.2% ropivacaine (standard-volume PENG) Group 2: 20 mL of 0.2% ropivacaine + 4 mg perineural dexamethasone Group 3: 10 mL of 0.2% ropivacaine (low-volume PENG) Group 4: 10 mL of 0.2% ropivacaine + 4 mg perineural dexamethasone The primary outcome was the time to first rescue opioid analgesia. Secondary outcomes included total 48-hour opioid consumption (expressed in oral morphine equivalents), numeric rating scale (NRS) pain scores, quadriceps muscle strength, neutrophil-to-lymphocyte ratio (NLR), and platelet-to-lymphocyte ratio (PLR) at 12, 24, and 48 hours postoperatively.

Results demonstrated that the addition of dexamethasone, regardless of volume, significantly prolonged the duration of analgesia and reduced opioid consumption compared to non-adjuvanted PENG blocks. The low-volume + dexamethasone group achieved comparable analgesia to high-volume protocols with better inflammatory profiles. Quadriceps strength was preserved in all groups. These findings support the use of perineural dexamethasone as an effective enhancer of PENG block analgesia while enabling lower local anesthetic volume, potentially improving safety and recovery outcomes in THA patients.

Inclusion criteria

• Adults aged ≥18 years scheduled for primary unilateral total hip arthroplasty (THA).
• American Society of Anesthesiologists (ASA) physical status I-III.
• Ability to provide written informed consent.
• Spinal anesthesia planned as the primary anesthetic technique.
• Body mass index (BMI) between 18 and 35 kg/m².
• Fluent in the local language and able to understand the NRS pain scoring system.

Exclusion criteria

• Known allergy or hypersensitivity to ropivacaine, dexamethasone, or other amide local anesthetics.
• Pre-existing neurological deficits or neuropathies affecting lower limb motor or sensory function.
• Chronic opioid use (daily use >30 mg oral morphine equivalents for >1 month prior to surgery).
• History of coagulopathy, current anticoagulant therapy not eligible for regional anesthesia.
• Uncontrolled diabetes mellitus (HbA1c > 9%) or active systemic infection.
• Pregnancy or breastfeeding.
• Previous surgery or implantation on the ipsilateral hip.
• Inability to cooperate with postoperative assessments or participate in follow-up.