麻醉与临床研究
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An Anatomical and Clinical Proof of Concept of a Novel Gastrosoleus Interfascial Plane Block and Comparison with the iPACK Block for Posterior Knee Pain Following Knee Replacement Surgeries: A Cadaveric Demonstration and Pilot Study

Riya Sarah Abraham, Rahul Pillai, Sajan Philip, George Noble E Cherian, Anil Thomas Oommen, Aby S Charles

Introduction: Analgesia following knee replacements has been evolving, with peripheral nerve blocks gaining precedence over central neuraxial techniques. Good surgical outcomes rely on early rehabilitation, necessitating the need for good pain relief without motor blockade. Current evidence supports regional analgesia with an adductor canal catheter, in conjunction with an iPACK block (infiltration between popliteal artery and the capsule of knee joint).

Methodology: We describe a fascial plane block between the medial head of gastrocnemius and the soleus muscles in the leg. Anatomic continuity of this plane with the space surrounding the knee joint capsule (in keeping with existing literature regarding the deep fascia of the leg) was established following a cadaveric demonstration, wherein dye injection was done under ultrasound guidance approximately 7 cm-8 cm distal to the joint line. Subsequent dissection till the popliteal fossa revealed staining over the capsule, where the genicular nerves enter the knee joint. We hypothesized that the target site of drug spread with the iPACK (i.e., the posterior capsule of the knee joint) is similar to that obtained when drug is injected in the fascial plane between the medial gastrocnemius head and soleus muscles, thus conferring equivalent analgesia with negligible risk of motor involvement and vascular puncture.

Results: A pilot study, comparing the iPACK and the gastrosoleus interfascial plane blocks, was performed in 22 patients undergoing total knee replacement surgeries. These blocks were given along with an adductor canal catheter for all patients. Postoperative pain scores and motor power were assessed at fixed intervals.

Conclusion: We observed similar posterior knee analgesia postoperatively with use of the gastrosoleus interfascial block as compared to the iPACK. Consistent drug spread towards the knee joint was observed on ultrasound following each block. No motor involvement was observed with any of the patients who received the gastrosoleus block. Catheter placement for continuous analgesia can also be done safely in this fascial plane.