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EDITORIAL
Year : 2022 | Volume
: 23
| Issue : 2 | Page : 81-82
Sensory blocks for knee surgery: The dawn of a new era
Ghansham Biyani, Rajasekhar Metta
Department of Anesthesiology, All India Institute of Medical Sciences, Guntur, Andhra Pradesh, India
Correspondence Address:
Dr. Rajasekhar Metta
Department of Anesthesiology, All India Institute of Medical Sciences, 425, 4th Floor, OPD Building, Mangalagiri, Guntur - 522 503, Andhra Pradesh
India
Source of Support: None, Conflict of Interest: None
CheckDOI: 10.4103/TheIAForum.TheIAForum_95_22
How to cite this article:An ideal sensory block should provide complete analgesia with no motor weakness. However, in clinical practice, finding such blocks is a rarity, and hence we aim for an optimal balance between adequate analgesia and preserving motor function. Analgesia for knee surgeries can be provided by performing proximal blocks such as lumbar and sacral plexus, or combination of femoral, obturator, and sciatic nerves. Although they provide excellent analgesia, motor weakness is common.[1] Over the past two decades, selective sensory blocks for knee joint like adductor canal block (ACB) and infiltration between the popliteal artery and capsule of the knee joint (IPACK) have emerged. By preserving the motor function, they allow early mobilization of the patient and thereby the advantages of ambulation.
Selective blockade of articular branches of the femoral, obturator, and sciatic nerves supplying the knee joint is the target of interest for the abovementioned blocks. The anterior capsule of the knee joint is supplied by the articular branches from nerve to vastus lateralis and nerve to vastus intermedius, superomedial genicular branch from nerve to vastus medialis, infrapatellar branch from the saphenous nerve, inferolateral and recurrent branches from the common peroneal nerve.[2] The posterior capsule is entirely supplied by the branches of tibial nerve with a small contribution from the posterior division of the obturator nerve and common peroneal nerve in the superomedial and superolateral aspects, respectively.[3]
The ACB was first described by Manickam et al. in 2009.[4] The adductor canal (Hunter's canal or subsartorial canal), is a musculoaponeurotic tunnel extending from the femoral triangle proximally to the adductor hiatus distally. It is bound superiorly by sartorius, anterolaterally by vastus medialis, and anteromedially by adductor longus or magnus muscles.[5] Its contents are femoral vessels, saphenous nerve, nerve to vastus medialis, and occasionally branches of the obturator nerve. While performing ACB, we aim to target only the sensory (articular) branches of these nerves innervating the anterior capsule, thereby preserving the motor power. In a recent meta-analysis by Hasabo et al.,[6] the researchers have found that ACB largely preserves the strength of quadriceps muscle, and its analgesic efficacy is equal to femoral nerve block. However, case reports of quadriceps weakness have been reported,[7] questioning the ideal site of injection within the adductor canal. It has been postulated that motor-sparing effect is more obvious with an injection in the distal adductor canal compared to the proximal or mid adductor canal, but large-scale studies have failed to confirm the same.[8]
IPACK block was first described by Sinha et al. in 2012,[9] with the aim to block the articular branches of the sciatic nerve supplying the posterior capsule of knee joint. The injection is made between the popliteal vessels and capsule of the knee joint where these sensory branches run. In a study by Kandarian et al.,[10] the authors found that the addition of IPACK to the existing multimodal analgesic protocol significantly reduces the pain scores in the immediate postoperative period. Similarly, in a meta-analysis by Guo et al.,[11] the authors found that the addition of IPACK to the ACB is a good technique for pain management following total knee arthroplasties. However, in other studies, the block is found to have no effect on opioid consumption, length of stay, and adverse events within 30 days.[12],[13] Moreover, due to its close proximity to the surgical site, the block should be performed under strict aseptic precautions.
Selective sensory blocks are the need of the hour, but in reality, we are still in search of the one. In addition to ACB and IPACK blocks, other sensory blocks such as selective blockade of nerve to vastus lateralis, and nerve to vastus intermedius are described in the literature, but the evidence is lacking to recommend their routine use. Future research must be aimed at modifying the present techniques, finding newer sensory blocks, and throwing more light in determining the role of such motor-sparing sensory blocks in the present multimodal analgesic regimen.
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