Can surgeons reproduce a sensory hip block? Rethinking analgesia in total hip arthroplasty

Early mobilization after total hip arthroplasty (THA) has become an important component of care. Faster recovery pathways, reduced length of stay, and improved patient outcomes all depend on effective postoperative analgesia that does not compromise motor function. Yet, many widely used regional anesthesia techniques still present a fundamental trade-off: good pain control at the expense of quadriceps strength.

The pericapsular nerve group (PENG) block has emerged as a promising alternative. Designed as a predominantly sensory block, it targets the articular branches of the femoral nerve and accessory obturator nerve while preserving motor function. But despite its advantages, its implementation depends heavily on ultrasound guidance and specialized anesthesia expertise.

This raises a practical and clinically relevant question: Can orthopedic surgeons reproduce a PENG-type block, without ultrasound, and achieve comparable anatomical coverage?

Our ongoing cadaveric study seeks to explore this possibility.

Developing a surgeon-performed PENG-type approach

The rationale for this project stems from a well-recognized limitation in perioperative care for THA. Traditional blocks such as the lumbar plexus block and suprainguinal fascia iliaca block provide reliable analgesia but frequently result in femoral nerve blockade and quadriceps weakness. This motor impairment can delay mobilization and increase fall risk.

The introduction of the PENG block represented a paradigm shift. By selectively targeting the sensory innervation of the anterior hip capsule, it allows effective analgesia while preserving quadriceps function. Clinical studies, including a randomized trial by Aliste et al., have shown that PENG provides comparable pain control to suprainguinal fascia iliaca block with improved motor preservation.
However, the standard PENG technique relies on ultrasound imaging to identify anatomical landmarks between the anterior inferior iliac spine and the iliopectineal eminence. This requirement may limit its widespread adoption, particularly in settings without advanced regional anesthesia resources.

From a surgical perspective, the anterior capsule and pericapsular structures are accessible through a posterior approach during THA. This anatomical access opens the possibility of performing a targeted infiltration that mimics the distribution of a PENG block.

Our study was designed to investigate whether such an approach is feasible, reproducible, and anatomically accurate.

What we’ve seen so far

The project is currently in an advanced experimental phase, with multiple cadaveric procedures completed.

Using cadaveric specimens, we developed a protocol in which orthopedic surgeons perform a PENG-type infiltration through a posterior approach. A dye solution is injected, and subsequent dissection is performed to assess the spread and determine whether key articular nerve branches are effectively stained.

This process allows us to evaluate whether surgeons, after appropriate training, can achieve a distribution similar to that obtained by anesthesiologists using ultrasound-guided PENG blocks.
Preliminary observations suggest that posterior approach infiltration performed by orthopedic surgeons can reach relevant pericapsular regions and achieve staining patterns consistent with the intended sensory targets.

Although the study is ongoing and final analysis is still pending, these early findings are encouraging. They support the hypothesis that a surgeon-performed, PENG-like technique may be feasible and equivalent to a traditional PENG block.

Future steps include refining the injection technique, increasing sample size, and performing comparative analysis against ultrasound-guided PENG blocks.