Anat Cell Biol.  2024 Jun;57(2):229-237. 10.5115/acb.23.274.

A cadaveric study investigating the spread of injectate following an interspace between the popliteal artery and the capsule of the posterior knee block in a neonatal sample: a pilot study

• Govender-Davies S
• Davies L
• Pillay-Addinall S

• KMID: 2556567
• DOI: http://doi.org/10.5115/acb.23.274

Abstract

The infiltration of the interspace between the popliteal artery and the capsule of the posterior knee (IPACK) block, is a novel ultrasound-guided technique used for postoperative pain management of the knee. The success of the block is attributed to the spread of injectate between the capsule of the knee and the popliteal artery. This novel technique is believed to target the articular branches of the tibial, common fibular (peroneal) and obturator nerves. However, the extent of the spread in a paediatric population is unknown. Therefore, this study aims to evaluate the spread of the IPACK block. Using ultrasound guidance, the IPACK block was replicated bilaterally in neonatal cadavers. Methylene blue dye (0.3 ml/kg) was injected proximally and distally. Subsequently, cadavers were dissected to determine the injectate spread. Proximal injections resulted in staining of some of the articular branches, while the distal injections resulted in staining of all four articular branches. Additional staining of the superior lateral and medial genicular nerves was noted irrespective of the technique. Overall, both injections resulted in posterior, anterolateral spread with limited medial spread. Results from this study reveal preservation of the main nerve trunks following the proximal technique, while the distal technique displayed greater staining of the articular branches. We believe that the block can be seen as a more holistic and viable alternative to lower limb blocks for the paediatric population, as it allows for a wider spread in the posterior and medial-lateral compartments of the knee.

Keyword

Interspace between the popliteal artery and the capsule of the posterior knee; Injectate spread; Neonatal sample; Cadaveric

Figure

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  Fig. 1 (A) Schematic drawing of the lateral view of the knee joint displaying the level of the proximal technique (black dotted line). (B) Posteromedial view of the knee displaying the needle insertion for the proximal technique. (C) Schematic drawing of the lateral view of the knee joint displaying the level of the distal technique (black dotted line). (D) Posteromedial view of the knee displaying the needle insertion for the distal technique.

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  Fig. 2 Dissection following a proximal interspace between the popliteal artery and the capsule of the posterior knee injection. Purple line, branch of the sural nerve from the common fibular (peroneal) nerve (cut and reflected); green line, branch of the sural nerve from the tibial nerve; blue line, sural nerve; red arrow, tibial nerve; yellow arrow, common fibular (peroneal) nerve; LG, lateral head of gastrocnemius muscle; MG, medial head of gastrocnemius muscle; SM, semimembranous muscle; ST, semitendinosus muscle.

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  Fig. 3 Dissection following a distal interspace between the popliteal artery and the capsule of the posterior knee injection. Purple line, branch of the sural nerve from the common fibular (peroneal) nerve (cut); green line, branch of the sural nerve from the tibial nerve; red arrow, tibial nerve; yellow arrow, common fibular (peroneal); LG, lateral head of gastrocnemius muscle; MG, medial head of gastrocnemius muscle; BF, biceps femoris muscle; SM, semimembranous muscle; ST, semitendinosus muscle.

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  Fig. 4 Staining of methylene blue dye following a distal interspace between the popliteal artery and the capsule of the posterior knee injection. Green arrow, posterior branch of the common fibular (peroneal) nerve; orange arrow, articular branch of the superior branch of the tibial nerve; yellow arrow, articular branch of the inferior branch of the tibial nerve; blue dot, sciatic nerve; LG, lateral head of gastrocnemius muscle; MG, medial head of gastrocnemius muscle; BF, biceps femoris muscle (cut); SM, semimembranous muscle (cut); TN, tibial nerve; CFN, common fibular (peroneal) nerve.

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  Fig. 5 Staining of methylene blue dye following a distal interspace between the popliteal artery and the capsule of the posterior knee injection. Green arrow, superior medial genicular nerve; yellow arrow, superior medial genicular artery; yellow dots, articular branches from the superior medial genicular artery; white dots, muscular branches from the tibial nerve; TN, tibial nerve; LG, lateral head of gastrocnemius muscle; MG, medial head of gastrocnemius muscle.

Reference

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