How I Used to Do It: Anesthesia and Analgesia for Total Knee Arthroplasty: Four Decades of Evolution
The first total knee arthroplasty (TKA) was performed in 1968, and current projections anticipate 1.5 million TKA procedures will be performed annually in the United States by 2050., Given the prevalence of this procedure, there has been great interest through the years in optimizing the perioperative surgical and anesthetic care for these patients. The evolution of anesthesia and analgesia choices for TKA over four decades creates an interesting historical narrative.
The Primary Anesthetic: General Versus Neuraxial
General anesthesia or neuraxial anesthesia (NA)—including spinal, lumbar epidural, or combined spinal epidural (CSE) have been employed for decades for TKA. Evidence for NA has been conflicting: some systematic reviews demonstrated reduced complications with NA, whereas others showed only modest or no improvement in various patient-centered outcomes.
The holy grail of analgesia for TKA would provide opioid-sparing, prolonged analgesia without motor block and be simple and cost-effective with minimal side effects or complications.
More recently, database reviews and outcome studies with large numbers of patients have provided more robust evidence. Although those retrospective studies cannot account for anesthesia selection differences or institution-specific practices, one review combining total hip and knee arthroplasty (including 544,000 TKA) showed reduced risk of major complications and intensive care unit use when NA was employed. Two studies using data from the American College of Surgeons National Surgical Quality Improvement Program database showed reduced infection, transfusion, and overall complications with NA but no difference in mortality when compared with general anesthesia.,
Despite this, general anesthesia remains a common choice for TKA, with database studies showing that NA is used in only 25.5–45% of cases. Over time, epidural use has decreased in favor of spinal anesthesia for NA.
Early Analgesic Considerations: Epidural Analgesia
Historically, the desire to continue epidural analgesia (EA) into the postoperative period influenced the choice of lumbar epidural as the primary anesthetic. Because TKA is expected to produce moderate to severe pain, EA was continued for 2 to 3 days in the 1980s and 1990s. A number of important developments led to an evolution away from EA, including the release of enoxaparin for venous thromboembolism prophylaxis in the United States in 1993, followed by multiple reports of spinal hematomas and paraplegia after NA in patients receiving enoxaparin. This resulted in the Food and Drug Administration (FDA) issuing a public health advisory and black box warning about the combination in 1997.
At the same time, there was enthusiasm to mobilize patients soon after surgery and reduce hospital length of stay. Two European studies, showed continuous femoral nerve block (cFNB) and EA significantly reduced pain scores when compared with systemic opioids (intravenous patient-controlled anesthesia), but cFNB had a better side-effect profile (less nausea, pruritus, urinary retention) than EA. Both studies also were the earliest to show that cFNB and EA resulted in improved knee flexion and earlier patient mobilization, demonstrating improvement with regional blockade in surgical outcomes and not just analgesia. This led to a shift from EA and epidural as the primary anesthetic for TKA, although some institutions have continued to use CSE with EA for 1 to 2 days postoperatively.
Parenthetically, the earliest CSE (1979) used separate needle insertions, because needle-through-needle was thought to risk catheter damage or metal shaving contamination in the epidural space. In addition, it was feared that threading an epidural catheter following the dural puncture for the spinal might increase the risk of an inadvertent intrathecal catheter. The latter concern was later disproven with cadaver epiduroscopy, and matched needle-through-needle kits for CSE became commercially available in the late 1980s. Fenestrated Tuohy needles and a unique double-barreled CSE needle (Eldor) were also available but did not garner widespread interest.
Physicians had a brief interest in postoperative analgesia produced by spinal microcatheters (32G) that could be inserted through a 22–26G spinal needle, but technical difficulties and breakage occurred, and cases of cauda equina syndrome likely because of local anesthesia (LA) maldistribution led to a 1992 FDA safety alert and withdrawal of microcatheters from the United States market after a few years.
The History of Anterior Analgesic Options
Analgesic approaches for TKA have evolved as well over the past several decades. With EA, both the lumbar plexus and the sciatic nerve distributions are well anesthetized. However, controversy continues as to which nerve distributions need to be blocked for analgesia following TKA and how best to accomplish blockade without causing side effects or interfering with mobilization. The TKA incision is primarily in the femoral nerve distribution, although tibial bone cuts involve the sciatic and likely the obturator distribution medially.
The Rise and Fall of the Three-in-One Block
Alon Winnie developed the concept of the three-in-one block whereby all three nerves of the lumbar plexus (femoral, obturator, and lateral femoral cutaneous nerve) theoretically should be blocked by a single inguinal injection after eliciting a femoral nerve paresthesia. Although his fascial compartment blocks were revolutionary in promoting simpler, single-injection upper- and lower-extremity block techniques, most experts believe that the obturator nerve is unlikely to be blocked by a single perifemoral nerve injection. In addition, the cutaneous sensory distribution of the obturator nerve is variable or absent, and the success of an obturator nerve block (ONB) could not, therefore, be proven by sensory testing. In fact, controversy remains over the relative contribution of the obturator nerve to pain after TKA, with a few studies showing improved analgesia with the addition of ONB., However, researchers in a more recent prospective study found that only 7% of TKA patients with cFNB experienced pain in the postanesthesia care unit, which was then successfully treated with ONB (Sanjay K. Sinha, personal communication).
Alternative inguinal approaches to the lumbar plexus included a more lateral needle entry or fascia iliaca block with tactile perception of needle passage through the fascia lata and then fascia iliaca. Catheter placement at this site in the inguinal crease was also presumed to produce a three-nerve block and was quicker and less costly than nerve stimulator–guided cFNB. At one point, inguinal approaches commonly advanced catheters proximal 10–15 cm but sometimes even 20 cm beyond the needle with the thought that they would follow the psoas muscle cephalad to the origin of the lumbar plexus. However, a key study showed radiographically that catheters generally curled and only 23% advanced cephalad toward the lumbar plexus; in addition, the catheters were at risk for knotting with high threading distances.
Although inguinal block approaches are unlikely to reliably produce ONB, direct blockade of the obturator nerve can be added to cFNB if desired, or a posterior lumbar plexus (PLP, or psoas) approach can be employed. Some institutions favored continuous psoas block over cFNB to ensure obturator coverage, but quadriceps as well as adductor weakness can occur. In addition, the 1997 concern for the potent and irreversible anticoagulant effect of enoxaparin
coupled with a few case reports of substantial retroperitoneal bleeding after PLP block and anticoagulation made PLP (like EA) less attractive. By ASRA’s third edition of the Regional Anesthesia in the Patient Receiving Antithrombotic or Thrombolytic Therapy guidelines in 2010, which expanded to include deep blocks, PLP began to fall out of favor relative to more distal approaches. Incidentally, although early continuous nerve block techniques often employed epidural catheters, equipment specific to continuous peripheral nerve block techniques became available in the late 1990s. This included an insulated, stimulating needle with injection port and diaphragm for inserting the catheter through the needle after LA injection.
The Last Straw: Patient Falls
Although a large study showed that older age and higher comorbidity but not peripheral nerve block, were associated with falls after TKA, most anesthesiologists continued to have concern for fall risk with PLP and cFNB approaches, as they result in unavoidable quadriceps weakness and delayed mobilization. Although various rates and concentrations of local anesthetics have been compared, a combination has not been found that provides analgesia without quadriceps weakness. Patient fall risk became, then, the third strike encouraging transition away from PLP and cFNB blocks.
At the end of the 20th century, portable ultrasound entered regional anesthesia practice, first at the University of Vienna (Drs Marhofer, Kapral, and others), University of Toronto (Dr. V. Chan), and University of Alberta (Dr. B. Tsui). cFNB was readily adapted; catheter placement with ultrasound guidance was shown to be faster, less painful, and with reduced risk of vascular puncture compared with nerve stimulator guidance. Most important to the evolution of regional analgesia for TKA, it also provided opportunities for more specific distal block approaches.
Distal Blocks Take Hold
In 2011, groups in Copenhagen reported the evaluation of blockade distal to the inguinal crease in the adductor canal, postulating that saphenous and obturator blockade could provide analgesia after TKA. Most investigators have shown analgesia from those blocks to be noninferior to FNB following TKA, with an important advantage of a reduced risk of quadriceps weakness. Although some studies have shown dynamic analgesia with cFNB to be superior to continuous adductor canal block (cACB), mobilization milestones were still reached earlier with cACB.
Controversy has raged as to whether the location in the mid or proximal thigh should be considered within or proximal to the adductor canal and which different nerves are targeted at the various sites. For simplicity, we will call it an ACB, although anatomic purists may argue. Certainly with ACB, the saphenous nerve and some medial and anterior cutaneous branches of the femoral nerve may be blocked. The nerve to the vastus medialis, within its own fascial compartment, may also be blocked by approaches that are mid or proximal thigh level. More distal blocks in the true adductor canal affect some of the posterior obturator fibers, and LA spread through the adductor hiatus to the popliteal plexus may also contribute to analgesia.
Regardless of which nerves are blocked, cACB has taken hold as the alternative to cFNB with adequate analgesia and reduced risk of quadriceps weakness. Catheters require placement or tunneling to avoid the surgical field, and hence, the exit site is commonly under the tourniquet. Dose-finding and rate studies for cACB continue to refine the technique. As with any newer technique, complications may occur with more widespread use. Quadriceps myotoxicity, for example, has been reported with cACB.
Posterior Analgesic Options: The Sciatic Nerve
Although most pain following TKA originates in the lumbar plexus distribution, the sciatic nerve and its innervation to the posterior capsule contribute to postsurgical pain as well. The incremental analgesic benefit of sciatic block offsetting motor weakness and interference with mobilization is controversial. Concern also surrounds the risk of obscuring surgical stretch or injury to the common peroneal nerve, which is reported to have an incidence as high as 0.3–10% following TKA.
Definitive but relatively short-lived (8 hours) analgesic benefit has been demonstrated from performing a single-shot sciatic nerve block, but the potential consequences previously mentioned have led to the introduction of other options for analgesia to the posterior knee. This includes selective tibial nerve blocks and posterior infiltration of the knee capsule by the surgeon or anesthesiologist.[36-39]
The debate continues regarding the addition of the sciatic nerve block versus posterior capsule infiltration by the surgical team.[40-42] Other innovations include infiltration between the popliteal artery and capsule of the knee (iPACK) block by the anesthesiologist. The iPACK with ACB and modified periarticular infiltration (PAI) showed improved analgesia compared with PAI alone.
Developed in Europe as an alternative to specific anterior and posterior nerve blocks, injection of large volumes of dilute long-acting local anesthetic solutions for PAI has also been used. PAI, which sometimes combines nonsteroidal anti-inflammatory drugs and opioid adjuvants, can be infiltrated in multiple fascial, muscular, subcutaneous, and cutaneous sites. Substantial literature on the PAI technique, both single shot and continuous, has shown a benefit when combined with a proximal (ACB) nerve block. More prolonged, single-injection local anesthetics for infiltration are theoretically advantageous because of cost, simplicity, and infection risk. Studies of PAI with liposomal bupivacaine, however, have not shown improved quality or duration of analgesia over standard PAI techniques. Anesthesiologists may also perform PAI techniques, although PAI outside the highly sterile operating room environment raises a theoretical concern for infection risk; the literature is silent at present on this issue.
Many patients continue to have significant pain for days or weeks after a TKA procedure. Most of the analgesic approaches under current investigation have limited duration of a few days, and systemic analgesic regimens with multimodal therapy remain the mainstay of recovery pathways. In addition, the opioid epidemic adds pressure to taper rapidly or avoid opioid analgesics as much as possible. Other competing analgesic considerations include rising health care costs, changes to reimbursement, and an interest in shorter lengths of stay. The holy grail of analgesia for TKA would provide opioid-sparing, prolonged analgesia without motor block and be simple and cost-effective with minimal side effects or complications.
Enthusiasm for shorter inpatient stays has led Medicare to add an outpatient procedural code for TKA, and, as a result, some groups now send some patients home on the day of surgery with cACB. Others are using single-shot adductor canal blocks with long-lasting adjuvants off label, which have recently been shown to be clinically noninferior or equivalent when compared with cACB for 24–48 hours postoperatively.,
Future directions include some promising developments. For example, some evidence for peripheral nerve stimulation techniques for TKA is encouraging, but it is still investigational with an accompanying high cost. Cryoanalgesia and radiofrequency genicular nerve ablation techniques are also under investigation.
The steady growth in TKA procedures worldwide will challenge anesthesiologists and acute pain medicine physicians to continue their creative development and scientific investigation of regional anesthesia techniques over the coming decades, with the goal of enhancing the quality of recovery for patients following this procedure.
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