Genicular Nerve Versus Adductor Canal Block for Postoperative Analgesia

Chronic knee osteoarthritis (OA), an epidemic among aging populations, is a leading source of chronic pain in the United States and other developed countries . The rise in prevalence of knee OA is a direct result of factors including longer life expectancy and increased body mass index (BMI). It has been reported that at least 19% of American adults aged 45 years and older are affected . Severe postoperative pain following total knee arthroplasty (TKA ) has been shown to negatively affect early mobilization, physical rehabilitation, time to discharge, and overall post-op recovery

.Therefore, reducing postoperative pain and early mobilization has become critical in reducing early mortality, preventing future chronic pain, and limiting the use of opioids . Balancing pain control with patient ambulation often proves to be a challenge due to both the motor blocking effects of many proximal nerve blocks and the often inadequate analgesia associated with more superficial periarticular injections . Therefore, numerous modalities of analgesic treatment combining different methods of nerve blockade for effective postoperative analgesia and faster functional recovery have been discussed . However, the superior technique is yet to be

determined. Successful postoperative analgesia for TKA requires careful consideration of knee innervation, with an emphasis placed on branches of the femoral nerve innervating the anterior and medical aspects of the knee and branches of the sciatic nerve innervating the posterior aspects of the knee capsule . In the context of nerve blockade, femoral nerve block (FNB) has traditionally been a critical component in the multimodal management of pain in TKA patients due to the high analgesic efficacy and the minimal risks associated. However, FNB is associated with decreased quadriceps motor strength leading to limited physical therapy (PT) participation, delayed ambulation, and discharge . The adductor canal block (ACB) has been found to be an excellent alternative to the FNB, providing adequate analgesia to the anterior knee compartment while enabling an improved postoperative range of motion by sparing motor branches to the quadriceps muscles . However, patients do not achieve adequate posterior knee analgesia as ACB pain relief is primarily limited to the anterior capsule of the knee.

Genicular nerve block (GNB) and radiofrequency ablation of genicular nerves (RFGN) were originally introduced by Choi et al. as a therapeutic alternative for chronic knee OA and were quickly adopted for use in patients undergoing TKA due to the significant pain reduction and functional improvement observed in these patients . GNBs target five main innervating branches of the knee, including the superomedial, inferomedial, superolateral, inferolateral genicular nerves, and the infrapatellar branch of the saphenous nerve. Several bony landmarks surrounding these nerves aid in proper needle placement under fluoroscopic guidance . The GNB has a motor-sparing effect that is desirable for early ambulation postoperatively, better PT, and earlier discharge .

Inclusion criteria

• Patient acceptance.
• Sex: both; male and female.
• Age: over 65 years old.
• American society of anesthesiologists (ASA): II .
• Body mass index (BMI) less than 35 kg/m2.
• Operation : elective unilateral TKA.
• Duration of surgery : 2-3 hours.

Exclusion criteria

• History of allergy to local anesthetics (lidocaine or bupivicaine).
• Coexisting hematologic disorders or malnourished patient.
• Pre-existing major organ dysfunction including hepatic or renal failure, and left ventricular ejection fraction <30%
• Peripheral neuropathy.
• Patients with a diagnosis of cognitive impairment or significant psychiatric illness.
• Skin infection at site of block.
• Contraindication to spinal anesthesia as coagulopathy and infection at site of injection.