![]() ![]() The location of the tibial nerve (superficial to popliteal artery) and the common peroneal nerve (lateral edge of sonogram) can be seen by changing the tilt of the transducer. The popliteal vein may be compressed from pressure of the transducer and not be visible on the image.įrom this point, the probe is moved cephalad, keeping the popliteal artery in view, till the discontinuous, interrupted hyperechoic line of the condyles changes to a continuous, hyper-echoic silhouette of the femoral shaft just cranial to the condyles. The popliteal artery is seen as a pulsating anechoic structure in the center of the scan. At this level, the femoral condyles appear as discontinuous, curved hyper-echoic lines. The probe is placed transversely at or just above the popliteal crease to visualize the femoral condyles and the popliteal artery in cross-section (Figure 3). Another advantage of the curvilinear probe is the wide scanning view. With the patient in a prone position, a high frequency linear probe or the low frequency curvilinear transducer can be used depending on body habitus. Even though we have since transitioned to performing the iPACK in a supine position, it is still worthwhile to review the original injection technique to get a better understanding of the sonoanatomy and procedure. When we conceived the concept of iPACK, our injections were performed with the patient in a prone position. We introduced the iPACK technique at the American Society of Regional Anesthesia (ASRA), Spring meeting in 2012. ![]() The goal of iPACK is to selectively block only the innervation of the posterior knee joint while sparing the main trunks of tibial and common peroneal nerves, thereby, maintaining the sensorimotor function of the leg/foot. These articular branches can be blocked by infiltrating this tissue plane between the popliteal artery and the capsule of the knee (iPACK) with local anesthetic solution under ultrasound guidance. The articular branches, after arising from the main trunks of the tibial and obturator nerves, travel through a tissue space between the popliteal artery and the femur to innervate the posterior capsule of the knee (Figure 2). The goal of iPACK is to selectively block only the innervation of the posterior knee joint while sparing the main trunks of tibial and common peroneal nerves, thereby maintaining the sensorimotor function of the leg and foot. A selective tibial nerve block in the popliteal fossa is an alternative to sciatic nerve block and can provide analgesia without causing a foot drop, but it decreases sensory perception in the sole of the foot and causes weakness of plantar flexion. Posterior knee pain can be controlled by sciatic nerve block, but leads to undesirable foot drop and may delay diagnosis and treatment of surgically induced common peroneal nerve injury. This pain is mediated by articular branches that originate primarily from the tibial component of the sciatic nerve with contributions from the obturator nerve (Figure 1). These particulars can be discussed with your anesthesiologist before surgery.Controlling posterior knee pain after total knee arthroplasty is an important component of the comprehensive strategy for providing postoperative analgesia. The numbness caused by an IPACK block may last as long as 24 hours.Īs with any anesthetic, there are risks and benefits to nerve blocks. Since there are nerves in the posterior thigh that not only go to your knee but also to your foot, your foot may feel numb as well. After the spinal wears off, behind your knee will feel number. ![]() Immediately after surgery, both your legs may be numb and immobile because of your spinal anesthesia. A long thin needle will be inserted on the side of your thigh to inject behind your knee. They will inject this area with a long-acting local anesthetic like novocaine used by your dentist. The IPACK block is performed using the latest ultrasound equipment to pinpoint the exact location to infiltrate nerves going to your knee joint. Once you have arrived in the operating room, your anesthesiologist will provide sedation intravenously to make you comfortable and relaxed for the nerve blocks. Because it does not cover the entire knee, the IPACK block is often used in combination with an anterior knee block and a spinal or epidural for surgical anesthesia. This will help minimize the opioids you need to take in the immediate recovery phase. Patients who have an IPACK block will have the posterior part of their knee numbed. Interspace between the popliteal artery and capsule of the posterior knee (IPACK) blocks are used at HSS to reduce pain after knee surgery. ![]()
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