**6. Pain's pathways**

Pain is a complex complication that involves multiple pathways and systems in the human body. Knowledge of the different pathways of pain is fundamental for the development of effective therapeutic strategies to control it in different clinical conditions.

Somatic pathway of pain activates by painful stimuli that affect somatic tissue, like skin muscle, bone, and joints. This pathway transmits over nervous myelinated A-Delta fibers and nervous non-myelinated C fibers. The information of this pathway is processed on the bone marrow and gets transmitted through the spinothalamic tract up to the thalamus and somatosensorial cortex of the brain [20].

Visceral pathway of pain activates by painful stimuli that affect internal organs, like the GI tract, heart, and lungs. This pathway transmits through the nervous nonmyelinated C fibers. This pathway's information processes in autonomous nervous ganglia and the bone marrow, and it transmits through spinothalamic tract and the spinoreticular tract up to the thalamus and somatosensorial cortex of the brain [21].

Neuropathic pathway of pain activates by lesions in the peripheral or central nervous system. This pathway transmits through nervous myelinated A-Delta fibers and nervous non-myelinated C fibers, The information in this pathway gets processed in the bone marrow and transmits through the spinothalamic tract and spinoreticular tract up to the thalamus and somatosensorial cortex of the brain. This pathway is particularly difficult to treat because of the chronic nature of the pain and the lack of response to conventional analgesic medication [22].

#### **7. Analgesic scale**

World Health Organization (WHO) analgesic scale is a tool used for the evaluation and treatment of pain. This scale is based on pain classification according to intensity and the selection of an adequate analgesic for the treatment. In this section, it will be discussed the importance of the WHO analgesic scale for the evaluation and pain treatment, along with different levels and recommendations for its use.

The WHO Analgesic Scale is divided into four levels, according to the intensity of pain and the type of analgesic recommended for its treatment. The first level corresponds to a mild pain, and the recommendation is to use non-opioid analgesic, like acetaminophen or Ibuprofen. The second level corresponds to a moderate pain, and the recommendation is to use weak opioids, like codeine or tramadol. The third level corresponds to an intense pain, and the recommendation is to use strong opioids, like morphine or fentanyl. The fourth level corresponds to a refractory pain, and the recommendation is to use additional treatment, such as local anesthesia or nerve blocks [23].

The WHO analgesic scale is an important and useful tool used for the evaluation and treatment of pain, because it gives us a clear guidance for the selection of the analgesic according to the intensity of pain. Also, this scale helps professional healthcare workers to evaluate the efficacy of treatment of pain and make dose adjustments according to the patient's needs [24]. It is fundamental that this scale be used like a guidance and the treatment for pain must be individualized according to the needs of each patient. Professional healthcare workers must consider factors like age, comorbidities, individual sensibility and possible interaction with other medication [25].

#### **8. Preventive analgesia**

Focuses on postoperative pain control and the prevention of central sensitization and chronic neuropathic pain by providing analgesia administered preoperatively but not after surgical incision to reduce the intensity of postoperative pain [26]. Several studies have proven that preventive analgesia can aid postoperative analgesia and reduce the need of opioids after an orthopedic surgery. Preventive analgesia can also

#### *Postoperative Pain in Orthopedics DOI: http://dx.doi.org/10.5772/intechopen.111880*

reduce inflammation and immune response, which can diminish the incidence of postoperative complications and shorten the patient's treatment [27].

The options for treatment of preventive analgesia in orthopedic surgery include the preoperative administration of pain medication, like NSAIDs, corticosteroids, and lidocaine, the use of regional anesthesia like nerve blocks, intraoperative administration of analgesics like opioids and local anesthetics [28]. In spite of all the benefits that preventive analgesia can provide in an orthopedic surgery, there are some challenges associated with its implementation. Dose selection and the moment of the administration can be hard to determine and can vary according to the type of orthopedic surgery. Also, preventive analgesia can be expensive and require a more complex monitoring during the surgery [29].

#### **9. Pain evaluation**

Pain evaluation is an important part of the treatment during an orthopedic surgery. Acute postoperative pain can be difficult to control and can have fatal consequences if not treated in time. The pain scale is a simple tool commonly used to evaluate postoperative pain. It asks the patient to rate their pain on a scale of 0–10, where 0 represents the absence of pain and 10 represents the worst imaginable pain. The pain scale is easy to evaluate and has been validated for its use in postsurgical patients [30].

Another tool commonly used to evaluate the pain is the Visual Analog Scale (VSA), which consists of a horizontal line of 10 cm, with the words "No Pain" on one end and "Worst Possible Pain" on the other end. Patients mark over the line to show the level of pain they are experiencing. This scale has demonstrated its valid and easy reproduction for the evaluation of postoperative pain [31].

Besides the pain scales, patients can describe pain using descriptive terms, such as "oppressive," "burn," "throbbing," or "colicky." The use of these words can help doctors to determine the pain's origin and choose the right treatment. In addition, the intensity of pain, a pain evaluation must include its location, duration, and effects on the physical function and quality of the patient's life. A pain evaluation must include the psychological and social factors that can relate to the perception of pain and its response to the treatment [32].

It is important to take into consideration that the pain evaluation is subjective, and it can be affected by cultural, social, or emotional factors, and that is why it is important to consider the experience and perspective of the patient in order to determine the postoperative pain in an orthopedic surgery.

#### **10. Regional anesthesia**

The control of postoperative pain is a crucial issue because its effectiveness will or may hamper early rehabilitation [33]. Richman and coworkers performed a metaanalysis, which included 19 articles enrolling 603 patients, related to postoperative analgesia with continuous peripheral nerve blocks and opioids. All articles showed that perineural analgesia provided significantly better postoperative analgesia compared with opioids [34]. Regional anesthesia is the most appropriate way to control postoperative pain. However, improvement in pain control after single-shot administration is limited to the first 24 postoperative hours. Therefore, it is not likely to significantly change outcome because early rehabilitation during the first 2–3

postoperative days is necessary to minimize the accumulation of small amounts of periarticular blood and edema, the first stages of joint stiffness [35].

Regional anesthesia can be broadly divided into two categories: neuraxial anesthesia [spinal, epidural, combined spinal epidural (CSE)], and peripheral nerve blocks (upper and lower extremity blocks).

#### **10.1 Neuraxial anesthesia**

Spinal anesthetic is a great choice for lower limb orthopedic surgery. Delay in ambulation due to lower limb muscular weakness, the risk of urine retention of up to 17%, and pain following block regression are all factors that limit the use of spinal anesthetic in the ambulatory context. It is critical to choose the right agent for ambulatory spinal anesthesia [36].

The technique of inserting a needle or a catheter between the vertebrae and administering drugs into the epidural (epidural anesthesia) or subarachnoid space (spinal anesthesia) is known as neuraxial anesthesia (NA). The spinal nerve root is the target of NA. LA with adjuncts such as preservative-free opioids are the most common medications injected neuraxially. NA is frequently utilized in abdominal and lower extremity surgery. The length of surgical incision and surgical manipulation determine the sensory level required for a certain surgery. T10 is required for total hip arthroplasty (THA), open reduction and internal fixation of the femur, and hip fractures, whereas L1 is required for knee surgeries [37]. Spinal anesthesia is normally given as a single injection, whereas epidural anesthesia is given through an indwelling catheter for continuous infusion.

The level of spinal blockade is determined by the overall dose of LA combination, the baricity of the injected solution, and the patient's position following the block. An epidural catheter allows for continuous drug infusion, extending the length of anesthesia. To avoid trauma to the termination of the conus medullaris, the spinal anesthetic needle is often inserted at the level of the L2–L3 interspace or below. The needle entry site for epidural anesthesia is determined by the extent of the dermatomes necessary for the treatment. It is frequently put in the mid to lower lumbar region for orthopedic surgeries. The volume of local anesthetic injected determines the degree of epidural blockade, whereas the concentration of the local anesthetic determines the density of the block. When compared to epidural anesthesia, spinal anesthesia results in a denser and more reliable block with a lower rate of block failure [38, 39].

## **10.2 Peripheral nerve blocks**

PNB include injecting a LA solution to a single nerve or nerve bundle to create sensory and motor blocking of a specific body location. The LA prevents painful impulses from reaching the central nervous system. PNB can be used for anesthesia or analgesia after surgery. It is usually given as a single shot, although a continuous infusion catheter can be used to prolong the analgesic impact after surgery. PNB is usually performed under ultrasound guidance to limit the hazards of intraneural and intravascular LA injection, avoid peripheral nerve damage, and assure proper LA distribution for a successful block.

#### *10.2.1 Blocks for upper extremity orthopedic procedures*

Understanding upper extremity peripheral nerve blocking requires a thorough understanding of brachial plexus anatomy. The brachial plexus provides the majority

#### *Postoperative Pain in Orthopedics DOI: http://dx.doi.org/10.5772/intechopen.111880*

of the upper extremity's muscular and cutaneous nerve supply. The brachial plexus is made up of five ventral nerve roots (rami) that give rise to trunks, divisions, cords, and terminal branches. The nerve roots join together to produce the upper, middle, and lower trunks. The three trunks divide into six divisions, which join to produce three cords: lateral, posterior, and medial cords. The terminal branches of the three cords feed the majority of the upper extremity nerves. Nerves that are not part of the brachial plexus augment the cutaneous area of the shoulder and upper arm. The superficial cervical plexus (C3–C4) innervates the superior portion of the shoulder via the supraclavicular nerve. Seventy percent of the sensory innervation to the shoulder comes from the superior trunk via the suprascapular nerve, with the C5 and C6 nerve roots contributing the most. The second thoracic nerve root innervates the axilla. The brachial plexus is restricted at four points: The interscalene block is used to connect roots and trunks, the supraclavicular block is used to connect trunks and divisions, the infraclavicular block is used to connect cords, and the axillary block is used to connect terminal branches [40]. The most frequently performed upper limb blocks are shown in **Table 3**.

## *10.2.1.1 Interscalene block*

The interscalene block is conducted at the brachial plexus roots-trunks level. The interscalene block anesthetizes C5–C8, as well as the supraclavicular branches of the cervical plexus C3–C4, which supply the skin over the acromion and the clavicle. The inferior trunk (C8–T1) is frequently spared; this is known as ulnar sparing. As


**Table 3.** *Upper extremity blocks.* a result, if this block is used for procedures at or near the elbow, an additional ulnar nerve block is required. This nerve block's coverage makes it useful for treatments involving the shoulder, proximal aspect of the humerus, and distal aspect of the clavicle [41].

The brachial plexus is targeted by the interscalene block, which is located lateral to the carotid artery and internal jugular vein, directly above the collarbone. Complications of the interscalene block include near-complete phrenic nerve blockade, sympathetic chain blockade resulting in Horner's syndrome, inadvertent injection in the vertebral artery, recurrent laryngeal nerve blockade resulting in hoarseness, and peripheral neuropathy. Pneumothorax, epidural injection, intrathecal injection resulting in total spinal anesthesia, spinal cord damage, and dorsal scapular or long thoracic nerve injury are also rare complications [42].

### *10.2.1.2 Supraclavicular block*

The supraclavicular block targets the brachial plexus above the collarbone at the trunks and divisions. The C5–C7 distribution includes the more superficial and lateral branches that supply the shoulder, lateral aspect of the arm, and forearm, as well as the deeper and more medial dependent branches of C8 and T1 that supply the hand and medial aspect of the forearm. Adequate local anesthetic distribution in both locations is required for successful nerve block of the arm and hand. A local anesthetic is injected between the anterior and middle scalene muscles at the level of the first rib, where the subclavian artery passes posterior to the midpoint of the clavicle. Because all of the trunks and divisions of the brachial plexus are closely packed and may be anesthetized at this location, the supraclavicular block causes anesthesia of the upper limb, including the shoulder [41].

#### *10.2.1.3 Infraclavicular block*

The infraclavicular block impacts the brachial plexus at the level of the cords before the axillary and musculocutaneous nerves branch. It causes numbness in the upper limb below the shoulder, including the arm, elbow, forearm, and hand, while leaving the medial proximal upper arm, which is supplied by the intercostobrachial nerve (T2), unaffected [42].

The infraclavicular block is injecting local anesthetic around the axillary artery beneath the clavicle. Under ultrasound guidance, the local anesthetic is administered in a U-shaped pattern around the axillary artery, encompassing all three brachial plexus cords. The infraclavicular block has a low pneumothorax rate of 0.7% [43].

### *10.2.1.4 Axillary block*

The axillary block is performed at the level of the brachial plexus branches. It anesthetizes the median nerve, the ulnar nerve, the radial nerve, and the musculocutaneous nerve, resulting in upper limb numbness from the mid-arm to the elbow, forearm, and hand. It should be noted that this block does not obstruct the axillary nerve; rather, the term of this regional treatment comes from the approach. The patient is positioned supine with the arm abducted to 90° in order to conduct this block. The median, ulnar, and radial nerves are identified as they surround the axillary artery using ultrasound guidance [44].

## *10.2.2 Lower extremity peripheral nerve blocks*

Peripheral nerve blocks can be used as a primary anesthetic modality or as a supplement to general or neuraxial anesthesia. Lower extremity nerve blocks are commonly used as an adjuvant to general or neuraxial anesthesia due to anatomical restrictions in attaining appropriate surgical anesthesia by peripheral nerve blockade [45]. The most frequently performed lower limb blocks are shown in **Table 4**.

#### *10.2.2.1 Femoral nerve block*

The femoral nerve block is used for lower extremity procedures that involve the anterior thigh and the medial side of the leg below the knee. The femoral nerve block is commonly used to provide analgesia for TKA, anterior cruciate ligament restoration, quadriceps tendon repair, foot surgery, and ankle surgery. The femoral nerve block can be coupled with other regional anesthetic methods, such as the sciatic nerve block, to broaden the anesthetic block's distribution, especially below the knee [46].

The femoral nerve provides sensory innervation to the anterior thigh and medial aspects of the calf, foot, and ankle. The femoral nerve additionally provides motor


**Table 4.** *Lower extremity blocks.* innervation to muscles of the lower extremity, including the quadriceps, sartorius, and pectineus muscles. As such, the femoral nerve block will cause weakness of the quadriceps muscles [46, 47]. This may result in decreased patient mobility and may potentially increase the risk of falls. Thus, patients should not be ambulating without assistance after a femoral nerve block [47].

#### *10.2.2.2 Iliac fascia block*

The femoral nerve and lateral femoral cutaneous nerve are both anesthetized using the fascia iliac block, a regional anesthetic technique. It is used for analgesia following hip surgery or in people who have had catastrophic hip fractures. This block has been found to provide fast analgesic benefit and may be administered pre-operatively while the patient is waiting for their procedure. Additionally, patients reported gains from passive hip flexion, which enabled them to sit up in bed before surgery [48]. A shorter hospital stays, less discomfort, and a shorter time to fascia iliac block have all been linked to patients with hip fractures. When presented to the emergency room, a fascia iliac block can be performed, and research has shown that this block provides better pain relief than systemic intravenous opioid therapy. The fascia iliac block may also help these patients be positioned in the best way possible for the implantation of spinal anesthesia during surgical femur fracture repair [48, 49].

A rather significant volume of local anesthetic (20–30 cc) is injected under the fascia iliac, just above the level of the inguinal crease, to conduct the fascia iliac block. The purpose of this block, which is normally carried out under ultrasound guidance, is to disseminate local anesthetic medially to the femoral nerve and laterally to the iliac spine [50].

#### *10.2.2.3 Adductor canal block*

The adductor canal block effectively relieves pain during knee and medial lower limb surgery. For patients receiving TKA, it may be administered as a component of a multimodal analgesic pathway to promote early ambulation, enhance patient comfort, and boost patient satisfaction [51]. A majority of TKA patients will probably feel moderate-to-severe post-operative pain, which can lengthen recovery times, cause problems from immobility, and reduce patient satisfaction [52]. Therefore, for these patients, safe and efficient localized anesthetic procedures are crucial.

While the femoral nerve block can effectively reduce pain for patients having a complete knee replacement, it can also cause quadriceps muscle weakness, which may make a patient more likely to fall. Because of this, patients having TKR frequently find the adductor canal block to be a good choice for post-operative analgesia. The adductor canal block produces comparable levels of postoperative pain alleviation as the femoral nerve block while greatly sparing the quadriceps and preserving balance. This enables efficient pain management and the ability to encourage early mobilization and ambulation following surgery [53, 54]. The adductor canal block has widely become the standard of care for analgesia for total knee arthroplasty.

#### *10.2.2.4 iPACK block*

The iPACK block has been used more frequently in TKA to relieve pain without sacrificing the strength of the lower extremities in the posterior compartment of the

#### *Postoperative Pain in Orthopedics DOI: http://dx.doi.org/10.5772/intechopen.111880*

knee. To effectively relieve pain in the posterior knee capsule, it targets the medial and lateral superior genicular nerves [55]. By guaranteeing coverage of both the anteromedial and posterior joints, the iPACK block and ACB together give a wider distribution of anesthetic coverage [55, 56].

According to recent research, the iPACK block, when combined with the adductor canal block and periarticular injection for TKA, significantly reduced postoperative pain during rest and ambulation [56, 57]. Early hospital discharge, a reduction in the need for opioids, and quicker ambulation were the outcomes.

Under ultrasound guidance, a needle is injected into the medial thigh to perform an iPACK block. This block typically uses a total volume of 15–20 cc of a local anesthetic solution. It is crucial to prevent accidental local anesthetic diffusion to the tibial or common peroneal nerve during the execution of this block, which could cause unfavorable motor weakness [58].

#### *10.2.2.5 Sciatic nerve block*

For lower extremity orthopedic procedures involving the foot, ankle, and posterior knee, a sciatic nerve block is indicated. The sciatic nerve block can be used alone, as in an Achilles tendon repair, or in conjunction with the femoral or saphenous nerve blocks to provide anesthetic coverage for knee surgery or foot/ankle surgery, respectively [59]. The sciatic nerve is the biggest nerve in the body, running from the anterior rami of L4 to S3. The tibial nerve and common peroneal nerve are the sciatic nerve's terminal branches. With the exception of the medial lower leg and foot, which is supplied by the saphenous nerve, the sciatic nerve block delivers analgesia to the posterior portion of the knee, hamstrings, and the entire limb below the knee (motor and sensory innervation).

Depending on the region of the limb requiring anesthetic blockade, the sciatic nerve may be blocked in numerous locations. The sciatic nerve block is administered on the proximal medial thigh via the anterior route. The transgluteal approach is used on the back of the buttock, between the ischial tuberosity and the greater trochanter. The subgluteal approach is conducted on the gluteal crease from the back. The sciatic nerve block is commonly administered at the level of the popliteal fossa, sometimes known as the "popliteal block" [59].

#### *10.2.2.6 Popliteal block*

For foot and ankle surgery, the popliteal nerve block is used in conjunction with the saphenous nerve block. The popliteal fossa is where the sciatic nerve splits into two major terminal branches, the tibial nerve and the common peroneal nerve [45]. A popliteal block is commonly performed proximal to the bifurcation of the tibial and common peroneal nerves; however, a recent study suggests that a popliteal block performed distal to the sciatic nerve bifurcation may result in a 30% faster onset of blockade while still achieving terminal branch blockade [59]. Furthermore, injection of local anesthetic distal to the sciatic nerve bifurcation offers better sensory block of the lower extremity.

Nerve damage, hemorrhage, and intravascular injection are all possible consequences of a sciatic nerve block. Nerve damage can cause a chronic foot drop with possible pressure necrosis [45, 60].

### **11. Regional anesthesia in patients at risk of bleeding**

There have been no prospective studies on peripheral nerve blocks in the presence of anticoagulants. The ASRA recommends the same guidelines for peripheral nerve blocks as for neuraxial procedures. Cases of psoas and retroperitoneal hematomas have been reported after lumbar plexus nerve blocks and psoas compartment nerve blocks. These patients were either on enoxaparin, ticlopidine, or clopidogrel. In some cases, the hematoma occurred in spite of adherence to the ASRA guidelines.

It is probably too restrictive to adapt the ASRA guidelines on neuraxial nerve blocks to patients undergoing peripheral nerve blocks. The European Society of Anesthesiology has noted that the guidelines for neuraxial nerve block do not routinely apply to peripheral nerve blocks. The Austrian Society of Anesthesiology, Resuscitation and Intensive Care, on the other hand, has suggested that superficial nerve blocks can be safely performed in the presence of anticoagulants. Because of the possibility of retroperitoneal hematoma, lumbar plexus and paravertebral nerve blocks merit the same recommendations as for neuraxial injections. The same guidelines should also apply to visceral sympathetic nerve blocks. The ASRA guidelines may, therefore, be applicable to nerve blocks in vascular and noncompressible areas, such as a celiac plexus nerve blocks, superior hypogastric plexus nerve blocks, and lumbar plexus nerve blocks [61].

#### **12. Nonsteroidal anti-inflammatory drugs**

The mechanism of NSAIDs (nonsteroidal anti-inflammatory drugs) not only has been described by the peripheral inhibition of prostaglandin synthesis but also through a variety of other peripheral and central mechanism. The central role that augments its known peripheral action, by which it promotes the production of endogenous opioid peptides [62].

The healing process of fractures is a complex process which includes a combination of sequential set of events that depends on the stability of the fracture. There are many factors that influence this process, including the use of NSAIDs. The use of NSAIDs has been studied for many years with debatable effects on bone healing. Humaid Al Farii et al conclude from his meta-analysis that NSAIDs that do not include indomethacin can be used for pain management without having a significant effect on bone healing and additionally, the use of NSAIDs for short duration, less tan2 weeks, does not show a statistical in nonunion [63].

NSAIDS are proven to be effective for musculoskeletal pain, with head-to-head clinical studies noting equivalent pain control with NSAIDs compared with opioids with a reduced risk profile. Contraindications with NSAIDs include peptic ulcer disease, chronic or end-stage renal disease, bronchial asthma, and breastfeeding women [64].

#### **12.1 Acetaminophen**

Like NDSAIDS acetaminophen may be used after surgery to reduce the amount of stronger, opioid medications you need to control pain. Acetaminophen does not interfere with the COX-1 or COX-2 enzyme to reduce pain, so does not have antiinflammatory properties. Used alone, Works well for headaches, fever, and minor aches and pains, but does not reduce the inflammation and swelling that might accompany a muscle sprain.
