Total hip arthroplasty (THA) and total knee arthroplasty (TKA) are surgical procedures that have been shown to improve pain, function, and quality of life. However, these procedures are notoriously painful, and postoperative recovery can be challenging. Aside from patient discomfort, poorly controlled pain can prolong length of stay, limit participation in rehabilitation, and increase the cost of care. Severe acute postoperative pain is also a risk factor for developing chronic persistent postsurgical pain (PPSP), which is estimated to affect 7% to 20% of TKA and 2% to 8% of THA cases. In contrast, well-controlled pain allows for early mobilization, lowers complication rates, and may enhance overall recovery. For these reasons, a standardized, multimodal analgesic (MMA) regimen is a recommended component of clinical pathways. , In this chapter, we will review and summarize the clinical evidence for the various analgesic modalities available for THA and TKA.
The development of a perioperative analgesic pathway requires an understanding of the mechanisms involved in the generation, transmission, and perception of pain. Surgical incision causes a release of inflammatory mediators, such as substance P and prostaglandins (PGs), that bind to and activate nociceptors. Prostaglandin E2 (PGE2) is an important mediator of acute pain and has been implicated in peripheral and central sensitization. Nociceptors are specialized receptors found on the free nerve terminals of primary afferent neurons. These receptors detect noxious stimuli and convert them into an electrical signal that travels from the periphery to the spinal cord. Aδ and unmyelinated C-fibers are the sensory afferent neurons that convey pain throughout the body. Cutaneous and articular structures, such as the hip and knee, are densely innervated by these fibers. , Aδ and unmyelinated C-fibers enter the spinal cord via Lissauer’s tract and synapse on spinothalamic tract neurons, which are located on the dorsal horn of the spinal cord. Axons from STT neurons cross the midline and ascend the spinal cord until they synapse in the thalamus. Thalamic axons project to cortical structures that are involved in the sensory-discriminative, affective, and cognitive aspects of pain. The principal sites of pain modulation are the periphery, spinal cord, and supraspinal structures. Existing therapeutics target these areas of the pain pathway to produce analgesia. The sites of action for various analgesics are illustrated in Fig. 3.1 .
Both the hip and knee joints are densely innervated by branches of the lumbosacral plexus ( Fig. 3.2 ). Branches of the femoral nerve (FN), obturator nerve (ON), and sciatic nerve (SN) innervate the anterior, medial, and posterior knee, respectively. Innervation to the hip joint is more complex, but the nociceptor-rich region of the anterior capsule is believed to transmit the majority of painful stimuli via the FN and ON.
Historically, postoperative analgesia for total joint arthroplasty (TJA) was achieved with intravenous (IV) opioids delivered via patient-controlled analgesia (PCA) or continuous epidural infusions of local anesthetic with or without opioids. Although these techniques produced high-quality analgesia, their side effects conflicted with the goals of enhanced recovery. For example, opioids can cause respiratory depression, gastrointestinal dysfunction, and sedation. Compared with systemic opioids, epidural analgesia produces a denser level of analgesia. However, unintended hypotension, motor blockade, and impaired ambulation may also occur as the result of the nonselective blockade of sympathetic, sensory, and motor fibers.
Limitations of conventional analgesic techniques led to the development of MMA, which is an analgesic strategy that incorporates two or more nonopioid analgesics of different pharmacologic classes to target different receptors along the pain pathway. This strategy has been shown to improve the quality of analgesia and reduce opioid-related adverse effects. Multimodal analgesia has replaced opioid-based analgesia as the recommended analgesic strategy for many enhanced recovery after surgery (ERAS) pathways.
The preoperative phase is a critical period for perioperative optimization. Prior to surgery, patients are risk stratified and evaluated for the presence of modifiable risk factors. For example, obesity, diabetes mellitus, tobacco use, and malnutrition are modifiable risk factors. Preoperative optimization has been shown to reduce complications and improve postoperative outcomes.
Board-certified arthroplasty surgeons of the American Association of Hip and Knee Surgeons (AAHKS) were surveyed, and greater than 90% of respondents said that they routinely incorporate preemptive analgesia into their clinical practice. Preemptive analgesia is defined as the administration of analgesics prior to surgical incision. Studies suggest that early antinociceptive interventions aimed at attenuating the inflammatory response may reduce peripheral and central sensitization and the severity of postoperative pain. Preemptive analgesic strategies vary across orthopaedic practices but commonly include a combination of acetaminophen, nonsteroidal antiinflammatory drugs (NSAIDs) and/or gabapentinoids. Current literature is conflicting regarding effects of preemptive administration of ketamine on postoperative pain and opioid consumption in major orthopaedic surgeries, but it appears that the analgesic effect of ketamine is independent of time of administration. Preemptive opioid administration is not recommended because it may increase the risk of opioid-induced respiratory depression and sedation.
Special Considerations for Opioid-Tolerant Patients
Opioid-tolerant patients include those with a history of chronic opioid therapy, former and active opioid abusers, and former abusers enrolled in methadone or buprenorphine treatment programs. The perioperative management of these patients can be challenging because they are tolerant to the analgesic effects of opioids and, thus, require increasingly higher doses to achieve analgesia. Additionally, these patients exhibit a phenomenon called opioid-induced hyperalgesia, which is an increased sensitivity to pain as a result of opioid exposure.
Recent evidence suggests that chronic opioid use is associated with increased rates of postoperative complications. In a study by Zywiel et al., patients on chronic opioid therapy prior to TKA had higher rates of complications and were more likely to require reoperation for persistent pain and/or stiffness compared with opioid-naïve patients. Pivec et al. reported similar adverse outcomes in patients on chronic opioid therapy prior to THA. A 2016 study by Nguyen et al. sought to evaluate the impact of preoperative opioid weaning on clinical outcomes following TJA. In this retrospective matched-cohort study, patients who reduced intake of chronic opioids by more than 50% experienced greater improvements in functional outcomes than chronic opioid users who did not wean. Furthermore, the improvement in clinical outcomes was comparable to patients not on preoperative opioids, suggesting that preoperative opioid use may be a modifiable risk factor in TJA.
Despite evidence suggesting that preoperative opioid use can adversely affect outcomes, there is insufficient evidence to recommend preoperative opioid weaning, and the decision to wean should be made after close coordination with the patient’s prescribing physician. For chronic pain patients unable or unwilling to reduce their preoperative opioids, early referral to a pain specialist to optimize preoperative pain management and formulate a perioperative pain management regimen is recommended.
Methadone and buprenorphine are opioid medications used for treating opioid use disorder (OUD) and/or chronic pain. Methadone is a full mu opioid receptor agonist with a long half-life. It should be taken on the day of surgery and resumed as soon as possible after surgery.
Buprenorphine is a partial mu receptor agonist and kappa receptor antagonist. It binds strongly to and slowly dissociates from the mu opioid receptors. As the daily dose of buprenorphine increases, the number of unoccupied receptors decreases. For example, patients taking a daily dose of 2 mg of buprenorphine have 27% to 47% of their opioid receptors occupied, whereas those taking 16 mg have 80% to 92% of their opioid receptors occupied. As a result, patients taking buprenorphine doses of 16 mg or more per day are unlikely to receive significant benefit from additional opioid medications.
Managing the patient receiving buprenorphine medication-assisted treatment (MAT) for OUD is challenging. These patients are typically profoundly opioid tolerant, and opioids alone are unlikely to provide adequate analgesia. A multimodal approach with regional anesthesia is advisable. Discontinuation of buprenorphine exposes these patients to standard opioids, which may lead to relapse. Further, converting from buprenorphine to standard opioids does not improve analgesia. Recent recommendations support continuing buprenorphine MAT uninterrupted throughout the perioperative period. Clinical guidelines for the perioperative management of buprenorphine from the American Society of Regional Anesthesia and Pain Medicine (ASRA) and other societies is expected in the near future.
Many of these techniques are amenable to continuous blockade via a perineural catheter and should also be considered in this patient population as a means to extend the duration of analgesia.
Multimodal Analgesic Agents
Acetaminophen is a weak antiinflammatory but potent analgesic and antipyretic medication whose clinical efficacy is well established. It possesses minimal adverse effects, but fulminant hepatic failure can occur if daily consumption exceeds the recommended 4 g per day. Unlike NSAIDs, acetaminophen does not impair platelet or kidney function or cause gastric ulceration. Although its exact analgesic mechanism is unknown, central inhibition of PG synthesis via the cyclooxygenase (COX) pathway is believed to be involved.
When incorporated into a multimodal analgesic regimen, acetaminophen has been shown to reduce pain and opioid consumption after TJA. Prophylactic acetaminophen has also been shown to reduce the incidence of postoperative nausea and vomiting (PONV).
Oral and IV acetaminophen are the most common routes of perioperative administration, and both have been shown to reduce pain and opioid consumption when incorporated into a multimodal analgesic regimen. When IV acetaminophen (Ofirmev; Cadence Pharmaceuticals, San Diego, CA) was first approved by the US Food and Drug Administration (FDA) in 2010, it was hoped that it would augment the benefits of oral acetaminophen. However, studies comparing the two formulations did not demonstrate that IV acetaminophen was associated with superior outcomes. , , Therefore, without a clear clinical advantage, the routine use of the more expensive IV acetaminophen is not recommended. Instead, oral acetaminophen, which is comparable in safety and efficacy but also more cost-effective, is the recommended formulation. ,
Nonsteroidal Antiinflammatory Drugs
Perioperative oral NSAIDs have consistently demonstrated a reduction in opioid consumption and pain intensity. NSAIDs reduce pain and inflammation by inhibiting COX-1 and COX-2 enzymes, which catalyze the conversion of arachidonic acid into PGs and thromboxane A2 ( Fig. 3.3 ). The PGs produced by the constitutively active COX-1 enzyme are responsible for protecting the gastrointestinal mucosal lining, platelet aggregation, and other homeostatic functions. In contrast, COX-2 is an inducible isoform associated with the production of PGs that produce pain, inflammation, and fever.
NSAIDs are classified as either selective COX-2 inhibitors or nonselective (COX-1 and COX-2) inhibitors. Both classes of NSAIDs have been shown to consistently reduce pain and opioid consumption, but COX-2 inhibitors are believed to possess a superior adverse effect profile. This claim is controversial; all NSAIDs, regardless of class, carry a warning from the FDA due to their risk of gastrointestinal bleeding, stroke, myocardial infarction, and acute kidney injury.
Celecoxib is the only highly selective COX-2 NSAID available in the United States ( Fig. 3.4 ). Perioperative celecoxib has been shown to significantly improve resting pain at 48 and 72 hours, decrease opioid consumption, and improve active range of motion following TKA. In a study by Buvanendran et al., the perioperative administration of a COX-2 inhibitor reduced opioid consumption, pain, PONV, sleep disturbance, and improved knee range of motion after TKA.
The gabapentinoids (gabapentin and pregabalin) are FDA approved for the treatment of specific types of neuropathic pain. They are commonly used off-label as part of a perioperative MMA pathway for the purposes of reducing acute, subacute, and chronic pain. Yet, their efficacy in treating acute postoperative pain remains controversial. The gabapentinoids modulate nociception through their actions on the α-2δ subunit of calcium channels. Sedation, dizziness or headache, and visual disturbances are the most common adverse effects associated with gabapentinoids. When combined with opioids, there is an increased risk of respiratory depression and sedation.
Despite initial promising data about efficacy of gabapentinoids as part of a postoperative MMA regimen, a recent meta-analysis indicated that perioperative use of gabapentinoids is not effective for postoperative pain management, does not prevent against chronic postoperative pain, and may also increase the risk of adverse events. However, when it comes to TJA patients, data on efficacy of gabapentinoids on postoperative pain is mixed. In a recent systematic review and meta-analysis of 13 high-quality randomized controlled trials (RCTs) of TJA patients, gabapentin was found to be no more effective than placebo at reducing pain or opioid consumption after TJA. In contrast, perioperative pregabalin was shown to reduce opioid consumption and postoperative pain. In a study by Lee et al., the addition of a single dose of pregabalin to a COX-2 inhibitor led to an additive reduction in early postoperative pain and analgesic consumption. Pregabalin is effective in reducing the risk of nausea, but also increases the risk of sedation. The risk of sedation is increased in the elderly and should be used with caution in this patient population. Accordingly, AAHKS and American Association of Orthopaedic Surgeons (AAOS) recommend only pregabalin for perioperative analgesia after TJA. It should be taken into account that use of neuraxial and regional anesthetic techniques in TJA patients may reduce risk of adverse events secondary to concomitant use of opioids and gabapentinoids via reducing perioperative opioid requirement. Furthermore, a higher dose and a longer postoperative administration of pregabalin may be required to observe a reduction on the rate of PPSP following TJA.
Intraoperative and Postoperative Phases
Periarticular infiltration (PAI) involves the injection of a long-acting local anesthetic around joints to assist with postoperative analgesia. Several studies have suggested that decreased opioid consumption at 24 and 48 hours can be achieved when PAI is utilized for TKA and THA. The major benefits of PAI in addition to postoperative analgesia include simplicity of performance (typically by surgeon intraoperatively) and lack of motor impairment that may be seen with nerve blocks. However, there is significant variability among studies with respect to technique, concentration of local anesthetic, use of adjuvants (e.g., epinephrine, ketorolac, morphine), and utilization of postoperative “top-up” boluses via a catheter, making recommendation of a specific approach or solution difficult. Additionally, the use of PAI must be weighed against the benefits and risks of nerve blocks since the total dose of local anesthetic that can be used is limited by the risk of local anesthetic systemic toxicity (LAST).
Ropivacaine is a local anesthetic that is commonly used for PAI due to its long duration of action. Compared with bupivacaine, ropivacaine possesses a more favorable adverse effect profile, including reduced cardiac toxicity and chondrotoxicity. The dose of ropivacaine used for PAI in available studies ranges from 150 to 400 mg. Current evidence suggests that PAI may not offer additional benefit when compared with multimodal analgesic regimens (excluding nerve blocks) in patients undergoing THA, , while PAI may be equivalent or superior to femoral nerve block and multimodal analgesic regimens in patients undergoing TKA. , However, superior postoperative analgesia for patients undergoing TKA may be achieved with an adductor canal block (ACB) compared with PAI while also resulting in minimal motor impairment. Furthermore, use of extended-release liposomal bupivacaine (Exparel; Pacira Pharmaceuticals, Parsippany, NJ), which releases bupivacaine over a period of 72 to 96 hours, appears to provide no additional clinically significant pain relief over the traditional local anesthetics. Ultimately, there is insufficient evidence to systematically recommend for or against the use of PAI. Its use should form part of a multimodal and patient-specific approach to postoperative analgesia, which includes the application of established and emerging nerve blocks and a medication regimen targeting multiple pain pathways.
Dexamethasone is a corticosteroid commonly administered as a prophylactic agent to reduce the incidence of postoperative nausea and vomiting. It has been shown that IV administration of dexamethasone at doses more than 0.1 mg/kg can be used as an adjunct to MMA regimen. However, the opioid-sparing effect of dexamethasone is modest and might not be clinically significant. The mechanism of analgesia induced by dexamethasone has not been fully understood, although antiinflammatory and immunosuppressive properties of dexamethasone appear to play an important role.
Despite concerns about adverse effects of perioperative dexamethasone, there is no evidence that a single dose of dexamethasone delays wound healing or increases risk of wound infection. However, mild elevation in blood glucose level can be expected. , Systematic dexamethasone may prolong the duration effect of local anesthetics used for nerve blocks. However, mixing dexamethasone with local anesthetics to prolong duration of the nerve block is more frequently used.
The opioid epidemic has sparked renewed interest in ketamine. Ketamine is a nonopioid analgesic that is believed to exert its acute pain effects at subanesthetic doses via N-methyl-D-aspartate (NMDA) receptor antagonism. Subanesthetic doses are defined as <0.35 mg/kg and infusions of <1 mg/kg per hour.
In a large meta-analysis of 70 RCTs, the authors concluded that patients undergoing orthopaedic surgery would be among the cohort of patients most likely to benefit from the analgesic and opioid-sparing effects of ketamine. In a study by Remérand, the addition of ketamine to an MMA regimen reduced 24-hour opioid consumption, improved 30-day functional outcomes, and decreased postoperative chronic pain up to 6 months after THA. Similar improvements in pain and functional outcomes have also been reported after TKA.
Despite the analgesic benefits, the role of ketamine for TJA has yet to be defined. The psychomimetic effects of ketamine may hinder early discharge and may not be suitable for outpatient surgery. However, in select cases (opioid-tolerant patients, those undergoing revision surgeries, or patients who are at high risk for PPSP), ketamine administration may be beneficial.
Epidural analgesia is a catheter-based technique that allows for continuous drug delivery into the epidural space. An epidural infusion of local anesthetics produces analgesia by interrupting neuronal transmission along spinal nerves. Compared with an IV PCA, epidural analgesia has been shown to provide superior levels of pain relief in patients undergoing THA and TKA. , Despite the analgesic benefit, adverse effects such as bilateral lower extremity weakness, hypotension, and spinal epidural hematoma formation as well as introducing new regional techniques with an ability to produce comparable analgesia with a superior safety profile have led to its decreased utilization, particularly for unilateral TJAs. However, if an epidural is placed for intraoperative anesthesia, it may be continued for postoperative analgesia. At the author’s institution, epidural analgesia is reserved for a very select patient population with a high likelihood of experiencing severe postoperative pain, such as the opioid tolerant and those undergoing revision joint surgery. Efforts should be made to discontinue the epidural as soon as possible, as it may delay immediate postoperative rehabilitation due to lower extremity weakness.
Lastly, patients undergoing THA and TKA are at a high risk of developing thromboembolic complications; thus, prophylactic anticoagulation is recommended. In the anticoagulated patient, neuraxial anesthesia can lead to spinal and/or epidural hematoma formation. The ensuing neurologic complications can be devastating and have prompted the need for safer and alternative pain management therapies. In summary, in light of developing new regional anesthetic techniques, the routine use of epidural analgesia has waned in primary TJAs, although it may be used in specific circumstances.
Peripheral Nerve Blocks
Peripheral nerve blocks (PNB) produce unilateral analgesia in the distribution of the targeted nerve or nerves. They can be performed as either a single injection or as a continuous catheter-based technique. The literature has consistently demonstrated that compared with placebo, PNBs decrease postoperative pain and opioid consumption following both THA and TKA. Two separate Cochrane reviews examining the efficacy of PNBs in this population concluded that PNBs produce excellent analgesia that is superior to systemic analgesia and equivalent to neuraxial techniques. , PNBs are devoid of many of the adverse effects that plague neuraxial anesthesia, including hypotension, pruritis, PONV, and urinary retention. With the exception of deep peripheral techniques, most peripheral nerve blocks can be performed in the anticoagulated patient. Peripheral nerve injury (PNI) is a rare complication of PNBs, and the risk of permanent injury is estimated to be between 2 to 4 per 10,000. PNB has replaced neuraxial anesthesia as the preferred regional anesthetic technique for TJA.
The most common PNBs used in THA are the fascia iliac compartment block (FICB), and the femoral nerve block (FNB). The most common PNBs for TKA are the FNB and ACB ( Table 3.1 ). To date, there is no consensus regarding the optimal nerve block(s) for either THA or TKA. Each of the previously mentioned techniques possess their own unique advantages. Unfortunately, each technique has also been shown to produce unwanted motor weakness. Newer blocks—such as the quadratus lumborum (QL) block, pericapsular nerve group (PENG) block, the iliopsoas plane block (IPB), and interspace between the popliteal artery and the posterior capsule of the knee (iPACK) block—have motor-sparing potential, but additional studies are necessary for confirmation. In the following sections, we review the existing literature and discuss the advantages and disadvantages of each technique.
|Peripheral Nerve Block||Targeted Nerves||Advantages||Disadvantages|
|Psoas compartment block||Lumbar plexus||Provides surgical anesthesia to the hip and knee when combined with the sciatic nerve block.||Technically difficult to perform.|
|Fascia iliaca compartment block||Targets the distal branches of the lumbar plexus, including the femoral, LFCN, + obturator nerves||Easier to perform than the psoas compartment block. May reduce pain, opioid consumption, PONV, and pruritis after hip surgery.||Obturator nerve is not reliably anesthetized.|
|Lateral femoral cutaneous nerve block||Lateral femoral cutaneous nerve||Pure sensory nerve block||Unlikely to provide clinically meaningful relief for hip surgery.|
|Femoral nerve block||Femoral nerve||Efficacy is well supported by the literature for knee surgery. Anesthetizes the major nerve that transmits painful sensations of the hip.||Spares the posterior knee. Quadriceps weakness may increase the risk of falls.|
|Adductor canal block||Saphenous nerve||Comparable analgesia to the FNB, but with better preservation of motor function.||Spares the posterior knee.|
|Sciatic Nerve Block||Tibial and common peroneal nerve||Provides analgesia to the posterior knee.||Motor weakness of the posterior muscles of the leg.|
|IPACK||Genicular branches of the tibial, common peroneal, and obturator nerves||Motor-sparing nerve block that targets the posterior knee.||Newer technique that requires further investigation.|
|Quadratus lumborum||Branches of lumbar spinal nerves||Easier to perform than the psoas compartment block.||Newer technique that requires further investigation.|
|PENG block and IPB block||Articular branches of the femoral nerve, obturator nerve, and obturator accessory nerve||Motor-sparing potential||Newer techniques that require further investigation.|
Psoas Compartment Block
The psoas compartment block (PCB) is an older technique that anesthetizes the lumbar plexus within the psoas muscle. This technique targets the FN, lateral femoral cutaneous nerve (LFCN), and ON, which transmit the majority of the pain after hip surgery. When combined with a sciatic nerve block, unilateral analgesia of the entire lower extremity can be achieved. The PCB is considered a deep peripheral nerve block and adheres to the same anticoagulation guidelines for neuraxial techniques. It is considered a technically challenging block and is associated with a high rate of failure. The PCB is rarely performed today.
Fascia Iliaca Compartment Block
The fascia iliaca compartment block (FICB) is a high-volume block that was introduced as an anterior approach to the lumbar plexus capable of anesthetizing the FN, LFCN, and ON. However, clinical studies indicate that only the FN and LFCN are reliably anesthetized. A modification of the classical approach, called the suprainguinal FICB , has been described and may provide more reliable spread to the lumbar plexus.
Both the FNB and FICB produce comparable levels of high-quality analgesia but the FICB may be an inherently safer technique because the injection site is distal to the femoral neurovascular bundle. In a study by Desmet et al., a single-injection FICB reduced mean morphine consumption at 24 and 48 hours postoperatively in patients undergoing THA. Compared with a single injection, a continuous FICB is more likely to produce motor weakness and increase the risk of inpatient falls. A reduction in pain intensity and a lower incidence of PONV and pruritis have been demonstrated when comparing the continuous FICB technique with IV PCA.
Lateral Femoral Cutaneous Nerve Block
The lateral femoral cutaneous nerve is a sensory nerve that provides cutaneous innervation to the lateral and anterior portions of the thigh. The distribution of the LFCN is inadequate for most surgical incisions for THA, and the addition of an LFCN block to a multimodal analgesic regimen has not been shown to be beneficial.
Femoral Nerve Block
The femoral nerve is the largest terminal branch of the lumbar plexus and arises from the L2–L4 spinal nerves. It provides motor innervation to the hip flexors, sartorius, and quadriceps muscles. The femoral nerve provides sensation to the nociceptor-rich, anterior capsule of the hip, anterior thigh, and the medial aspect of the lower leg via the saphenous branch.
Both single-injection and continuous FNBs have been shown to be efficacious in controlling pain after THA. , In patients undergoing elective THA, the use of a single-injection FNB was found to decrease opioid consumption for up to 24 hours after surgery, improve pulmonary function, and decrease the time to meeting postanesthesia care unit discharge criteria. Compared with an IV PCA containing opioids, FNBs reduce the incidence of PONV, improve knee flexion, and improve patient satisfaction.
Continuous femoral nerve catheters have the advantage of extending the duration of analgesia and are equally as effective as the PCB. However, it is unclear if continuous femoral nerve blocks (CFNBs) offer added benefit when compared with a single injection. , In a 2010 meta-analysis comparing a single-injection FNB with a CFNB, the CFNB failed to provide an analgesic or recovery benefit. A more recent meta-analysis concluded that patients receiving a CFNB consumed less opioids, but there was no significant difference in pain scores.
Quadriceps weakness is a major limitation to the use of FNB because it may impair ambulation. However, whether it increases the risk of falls remains controversial. A large retrospective database study of more than 190,000 records from 400 hospitals found no association between PNBs and inpatient falls. In a separate study that analyzed 95 falls out of a total of 3735 patients over a 3-year period, the authors concluded that the frequency of falls was comparable between patients whose CFNB was discontinued for >12 hours and those whose CFNB remained in situ or <12 hours after its removal. These findings call into question the association of quadriceps weakness and the risk of inpatient falls. It also suggests that other factors (i.e., medication side effects, delirium, decreased strength in the operative limb, inadequate supervision during ambulation, and so forth) may contribute more prominently to the risk of falling following TKA. Nevertheless, in this high-risk population, the implementation of fall prevention strategies, such as the routine use of assistive devices and ensuring adequate supervision, are imperative to reduce this devastating and possibly preventable complication.
Adductor Canal Block
Originally described by Lund et al. in 2011, the adductor canal block was introduced as an alternative to the FNB, which was “ almost devoid of motor-blocking effects.” The saphenous nerve resides within the adductor canal and is the principle target of the ACB. The saphenous nerve is a pure sensory branch of the femoral nerve that provides cutaneous innervation from anteromedial knee to the ankle ( Fig. 3.5 ). Performed at the level of the mid-thigh at a distance halfway between the iliac spine and the patella, the ACB is considered a technically easy nerve block. At this level, most of the motor fibers to the quadriceps have branched off to innervate their respective muscles, thus, preserving/minimizing its effects on quadriceps function.