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The popliteal fossa is a shallow depression located posterior to the knee joint. This area is often referred to as the knee "pit" and may develop vascular, nervous, lymphatic, and adipose issues as well as swelling and masses. The fossa houses several important structures that are essential for lower extremity function. Anatomic boundaries of the popliteal fossa include the following: Superomedially, the semimembranosus, and semitendinosus muscles. Superolaterally, the biceps femoris muscle (short and long heads) . Inferomedial and inferolateral, the medial and lateral heads of the gastrocnemius muscle contribute to the lower border, respectively. The plantaris muscle also runs deep to the gastrocnemius to form the inferolateral border. The roof of the fossa, proceeding from most superficial to deep, consists of the skin, superficial fascia, and deep (popliteal) fascia. The floor of the fossa includes the popliteal surface of the femur, the capsule of the knee joint, popliteal ligament, and fascia encasing the popliteus muscle. It is important to understand the involved anatomy of the popliteal fossa because patients could present with posterior knee pain due to multiple etiologies. One of the more common issues involving the posterior knee is a Baker cyst; it has a fluid-filled bursa, which is usually secondary to friction or irritation. Other causes of posterior knee pain could be a popliteal artery aneurysm, lymphadenopathy, thrombophlebitis, and very rarely, sarcomas. Proper diagnosis is essential for effective treatment and management., (Copyright © 2022, StatPearls Publishing LLC.)

A chordoma is a low-grade, slow-growing, but locally invasive and locally aggressive tumor. Chordomas belong to the sarcoma family of tumors. They arise from the remnants of the notochord and occur in the midline along the spinal axis from the clivus to the sacrum, anterior to the spinal cord. The location distribution of chordomas is 50% sacral, 35% skull base, and 15% occur in the vertebral bodies of the mobile spine (most commonly the C2 vertebrae followed by the lumbar then thoracic spine). Overall 5-year survival is approximately 50%, and treatment is en bloc surgical resection followed by high-dose conformal radiation therapy such as proton beam radiation., (Copyright © 2022, StatPearls Publishing LLC.)

The nervous system is a complex network that enables an organism to interact with its surroundings. Sensory components that detect environmental stimuli, and motor components that provide skeletal, cardiac, and smooth muscle control, as well as control of glandular secretions, are coordinated in a system to compel appropriate motor responses to the stimuli or sensory inputs that have been received, stored, and processed. The nervous system is made up of vast neural networks; signaling within these circuits enables thinking, language, feeling, learning, memory, and all function and sensation.  It is well-established that through the plasticity of existing cells our nervous systems can adapt to situations not previously encountered, but it also has been shown that neural stem cells (NSCs) are plastic and involved in creating new connections in adaptation and response to injury. NSCs play a fundamental role in development, and in the ability to respond to stimuli in the environment and injury., (Copyright © 2022, StatPearls Publishing LLC.)

Healthcare in the United States is primarily based on diagnosing disease and subsequently treating the disease. Consider several of the most prominent medical advances of the past century: , (Copyright © 2022, StatPearls Publishing LLC.)

The temporal bone is the thickest bone in the body and requires great force to fracture (1875 pounds or 850 kg of lateral force in one study). The temporal bone houses portions of the internal carotid artery and internal jugular vein, cranial nerves (CN) VII-XI, the middle and inner ear structures, and forms a portion of the middle cranial fossa. Such high-velocity injury to these crucial structures carries the risk of significant morbidity and mortality. The temporal bone is a paired component of the skull base, articulating posteriorly with the occipital bone, superiorly with the parietal bones, and anteriorly with the sphenoid bone creating the occipitomastoid, squamous, and sphenosquamosal sutures, respectively. The temporal bone has complex anatomy including four geographic parts (squamous, mastoid, petrous, tympanic) and numerous named foramen/canals (foramen lacerum, carotid canal, internal acoustic meatus, jugular foramen). : Foramen lacerum: greater petrosal nerve. Carotid canal: internal carotid artery. Internal acoustic meatus: CN VII, CN VIII. Jugular foramen: internal jugular vein, posterior meningeal artery, CN IX, CN X, CN XI. Additionally, there are 3 bony processes (zygomatic, mastoid, styloid). The otic capsule, or bony labyrinth, is the dense portion of the petrous temporal bone that surrounds the membranous labyrinth of the inner ear. This is, in turn, surrounded by the less dense and variably pneumatized petrous apex and the mastoid segment of the temporal bone. From anterior to posterior the otic capsule contains the cochlea, vestibule, and three semicircular canals. , (Copyright © 2022, StatPearls Publishing LLC.)

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease with multisystemic involvement. The condition has several phenotypes, with varying clinical presentations from mild mucocutaneous manifestations to multiorgan and severe central nervous system involvement. Several immunopathogenic pathways play a role in the development of SLE. Hargraves described the lupus erythematosus (LE cell) in 1948. Several pathogenic autoantibodies have since been identified. Despite recent advances in technology and understanding of the pathological basis and risk factors for SLE, the exact pathogenesis is still not well known. Diagnosis of SLE can be challenging, and while several classification criteria have been posed, their utility in the clinical setting is still a matter of debate. Management of SLE is dictated by organ system involvement. Despite several agents shown to be efficacious in treating SLE, the disease still poses significant morbidity and mortality risk in patients., (Copyright © 2022, StatPearls Publishing LLC.)

Shoulder dystocia is, by definition, a mechanical problem occurring during a vaginal delivery characterized by one of the following parameters: failure to deliver the fetal shoulders using solely gentle downward traction ; requirement of additional delivery maneuvers are needed to successfully deliver the baby; a documented head-to-body interval of greater than 1 minute. Unpredictable and often unavoidable obstetric emergencies complicate 0.6 to 1.4% of all vaginal deliveries. All obstetric providers are required to be knowledgeable regarding the risk factors and management of shoulder dystocia. Furthermore, shoulder dystocia can lead to obstetric brachial plexopathies such as Erb's or Klumpke's palsies. Injuries to the brachial plexus during birth can be categorized as upper lesions involving C5-6, lower lesions involving C8-T1, or total plexopathies involving C5-T1. , (Copyright © 2022, StatPearls Publishing LLC.)

The interossei muscles are intrinsic muscles of the hand located between the metacarpals. They consist of four (or three) palmar and four dorsal muscles that, respectively. These muscles are responsible for finger adduction and abduction. Synchronously, the palmar and dorsal interossei assist in flexion of the metacarpophalangeal joints and extension of the interphalangeal joints. All interossei muscles receive innervation from the deep ulnar branch of the ulnar nerve. Therefore, any injury to the ulnar nerve may have debilitating implications on specific intrinsic hand muscle functions, including finger abduction and adduction, which is primarily controlled by the interossei muscles.  , (Copyright © 2022, StatPearls Publishing LLC.)

Between each vertebral body of the spine are pads of fibrocartilage-based structures that provide support, flexibility, and minor load-sharing known as the intervertebral discs. These are primarily composed of two layers: (1) a soft, pulpy nucleus pulposus on the inside of the disc and (2) a surrounding firm structure known as the annulus fibrosus. A disruption of the normal architecture of these round discs can lead to a disc herniation or a protrusion of the inner nucleus pulposus, possibly applying pressure to the spinal cord or nerve root and resulting in radiating pain and specific locations of weakness. Slightly more than 90% of herniated discs occur at the L4-L5 or the L5-S1 disc space, which will impinge on the L4, L5, or S1 nerve root. This compression produces radiculopathy into the posterior leg and dorsal foot. If the disc injury progresses to the point of neurologic compromise or limitations with activities of daily living, then surgical intervention may be required to decompress and stabilize the affected segments. In the absence of motor deficits, a nonoperative course of analgesia, activity modification, and injections should be tried for several months. The surgical results for the primarily sciatic pain that has failed conservative treatment are predictable and favorable., (Copyright © 2022, StatPearls Publishing LLC.)

The fascia in the foot is composed of fibrous connective tissue that serves to separate, support, and attach muscles. It can be divided into the superficial fascia and the deep fascia. The superficial fascia is located just beneath the skin and varies in strength depending on where it is in the foot. On the dorsal side of the foot, the superficial fascia is thin and mobile. In contrast, the superficial fascia of the plantar side is thick and has multiple septations that contain fat to provide a cushion for the foot. It also has thick connections with the underlying deep fascia.  The deep fascia is stronger than the superficial fascia. On the dorsal side of the foot, the deep fascia is thin and connected to the inferior extensor retinaculum. It continues laterally and posteriorly to connect with the plantar fascia, which is the name of the deep fascia on the plantar side. Similar to the superficial fascia, the deep fascia is much thicker on the plantar side. The central part of the plantar fascia forms the plantar aponeurosis, which starts proximally at the calcaneus and extends distally into five separate bands that become the digital sheaths. It is supported inferiorly by the superficial transverse metatarsal ligament.  The fascia acts as a border for the five anatomic compartments of the foot, which include the medial compartment, the central compartment, the lateral compartment, the dorsal compartment, and the interosseous compartment.  The medial compartment is bordered inferiorly by the medial plantar fascia, the central compartment is bordered inferiorly by the plantar aponeurosis, and the lateral compartment is bordered inferiorly by the lateral plantar fascia. The plantar aponeurosis also has intermuscular septa that extend superiorly through the foot to divide the medial, central, and lateral compartments. The interosseous compartment is bordered by the plantar and dorsal interosseous fascia. The dorsal compartment is bordered by the dorsal fascia superiorly and by the tarsal bones and dorsal interosseous fascia inferiorly. , (Copyright © 2022, StatPearls Publishing LLC.)

Professional ethics guide the health care staff in their interactions with patients, providers, co-staff and business associates in the workplace. However, there is a need for guidance on the best practices for the professional conduct of physicians and health care personnel in the digital environment. As new social networking platforms gain acceptance, professionalism must be applied in this new setting. In particular, ready access to online platforms leads to instantaneous feedbacks and comments from patients, health care workers, and health providers. In particular, issues of defamation have steadily risen., (Copyright © 2022, StatPearls Publishing LLC.)

The autonomic nervous system consists of the sympathetic and parasympathetic divisions. As the name implies, the lumbar sympathetic block can be utilized to disrupt the nerve supply from the sympathetic chain to the lower extremities. This is useful in treating sympathetic mediators of pain. Specifically, lumbar sympathetic blocks can be used for the treatment of painful conditions such as complex regional pain syndrome, phantom limb pain, hyperhidrosis, painful vascular insufficiencies, and pain from herpes zoster/shingles., (Copyright © 2022, StatPearls Publishing LLC.)

The major and minor psoas muscles and the iliacus muscle make up the iliopsoas musculotendinous unit (IPMU). Commonly called iliopsoas muscle. This complex muscle system can function as a unit or intervene as separate muscles. It is essential for correct standing or sitting lumbar posture, stabilizing the coxofemoral joint, and is crucial during walking and running. The fascia covering the iliopsoas muscle creates multiple fascial connections, relating the muscle to different viscera and muscle areas. Several disorders can affect IPMU at the level of its insertion (tendon) or involving the fleshy part. To solve these dysfunctions, the doctor will indicate which therapy will be most useful, conservative or surgical, as well as physiotherapy or an osteopathic approach. There are multiple anatomical variations of IPMU, and in case of pain and disturbances, it is important to perform instrumental examinations before making a precise diagnosis. With the current scientific knowledge, one can not imagine anatomy as segments but rather as a functional continuum., (Copyright © 2022, StatPearls Publishing LLC.)

The human brain is made up of approximately 86 billion neurons that “talk” to each other using a combination of electrical and chemical (electrochemical) signals. The places where neurons connect and communicate with each other are called synapses. Each neuron has anywhere between a few to hundreds of thousands of synaptic connections, and these connections can be with itself, neighboring neurons, or neurons in other regions of the brain. A synapse is made up of a presynaptic and postsynaptic terminal. The presynaptic terminal is at the end of an axon and is the place where the electrical signal (the action potential) is converted into a chemical signal (neurotransmitter release). The postsynaptic terminal membrane is less than 50 nanometers away and contains specialized receptors. The neurotransmitter rapidly (in microseconds) diffuses across the synaptic cleft and binds to specific receptors. The type of neurotransmitter released from the presynaptic terminal and the specific receptors present on the corresponding postsynaptic terminal is critical in determining the quality and intensity of information transmitted by neurons. The postsynaptic neuron integrates all the signals it receives to determine what it does next, for example, to fire an action potential of its own or not. , (Copyright © 2022, StatPearls Publishing LLC.)

The inferior gluteal nerve branches off the sacral plexus. Its short path is primarily for the innervation of the gluteus maximus muscle. The composition of this nerve is from the dorsal branches of the ventral rami of the fifth lumbar and the first two sacral nerves. It courses inferiorly and medially before exiting the pelvic cavity via the greater sciatic notch.  After exiting the notch, the inferior gluteal nerve passes inferior to the piriformis muscle belly before dividing into several muscular branches supplying the gluteus maximus., (Copyright © 2022, StatPearls Publishing LLC.)

The scapula or shoulder blade is the bone that connects the clavicle to the humerus. The scapula forms the posterior of the shoulder girdle. It is a sturdy, flat, triangular bone. The scapula provides attachment to several groups of muscles. The intrinsic muscles of the scapula include the rotator cuff muscles, teres major, subscapularis, teres minor, and infraspinatus. These muscles attach the scapular surface and assist with abduction and external and internal rotation of the glenohumeral joint. The extrinsic muscles include the triceps, biceps, and deltoid. The third group of muscles includes the levator scapulae, trapezius, rhomboids, and serratus anterior. These muscles are responsible for rotational movements and stabilization of the scapula., (Copyright © 2022, StatPearls Publishing LLC.)

A Baker Cyst, also known as a popliteal or parameniscal cyst, is a fluid-filled sac that forms in the posterior aspect of the knee, typically located between the semimembranosus and medial head of the gastrocnemius.  In adults, Baker's Cysts tend to form in association with degenerative conditions of the knee.  One of the most common associations seen is secondary to degenerative meniscal tears.  Inflammatory conditions and arthritides are also known causes of popliteal cyst formation.  When the cyst forms in association with a meniscal tear, the meniscus serves as a one-way valve and the extruded synovial fluid localizes and consolidates to form a viscous, gel-like material. In children, popliteal cysts more commonly arise as a primary condition.  Unlike adults, popliteal cysts in children arise from a herniated posterior knee joint synovium/capsule., (Copyright © 2022, StatPearls Publishing LLC.)

Osteoporosis is a condition describing a spectrum of overall compromised skeletal microarchitecture with clinical manifestations related to decreasing levels of bone mineral density (BMD)., Spinal cord injuries (SCIs) vary significantly in terms of the range of clinical impact and overall compromise to a patient’s functional outcomes and quality of life. SCIs have long been recognized as a clinical culprit that ultimately leads to osteoporosis. Clinicians are encouraged to recognize and appreciate the similarities and subtle nuances differentiating SCI-induced osteoporosis as a separate and distinct clinical sub-entity of the broader more generalized osteoporosis diagnosis., (Copyright © 2022, StatPearls Publishing LLC.)

The biceps brachii is a large, thick muscle on the ventral portion of the upper arm. The muscle is composed of a short head (caput breve) and a long head (caput longum). The short head originates from the tip of the coracoid process, and the long head originates from the supraglenoid tubercle (tuberculum supraglenoidale) of the glenoid/scapula. Both heads course distally and become a confluent muscle belly before tapering across the anterior aspect of the elbow, eventually inserting onto the radial tuberosity and the fascia of the forearm via the bicipital aponeurosis. The antagonist of the biceps muscle is the triceps brachii muscle., (Copyright © 2022, StatPearls Publishing LLC.)

The wrist joint also referred to as the radiocarpal joint is a condyloid synovial joint of the distal upper limb that connects and serves as a transition point between the forearm and hand. A condyloid joint is a modified ball and socket joint that allows for flexion, extension, abduction, and adduction movements., (Copyright © 2022, StatPearls Publishing LLC.)

Low back pain is one of the most common musculoskeletal complaints encountered in clinical practice. It is the leading cause of disability in the developed world and accounts for billions of dollars in healthcare costs annually. Although epidemiological studies vary, the incidence of low back pain is estimated to be 5% to 10%, with a lifetime prevalence of 60% to 90%. Most occurrences of low back pain are self-limited and will resolve without intervention beyond brief periods of rest, activity modification, and physical therapy. Approximately 50% of cases will resolve within 1 to 2 weeks. Ninety percent of cases will resolve in 6 to 12 weeks. Lumbosacral facet syndrome refers to a clinical condition consisting of various patient-reported symptoms, including unilateral or bilateral back pain radiating to either one or both buttocks, sides of the groin, and thighs, stopping above the knee. It should, however, be noted that in some cases, the symptoms of facetogenic pain may mimic radicular symptoms occurring from herniated discs or compressed roots. The facet joint degenerates secondary to repetitive overuse and everyday activities, eventually leading to microinstability and synovial facet cysts that generate and compress the surrounding nerve roots.  The lumbar facet joint constitutes approximately 15 to 45% of low back pain, with degenerative osteoarthritis as the most common form of facet joint pain. History and physical exam may serve useful in the diagnosis of facet joint syndrome, while imaging with radiographs, CT, and MRI are commonly used yet do not show an effective correlation between clinical symptoms and degenerative spine changes. Diagnostic blocks may indicate facet joints as the source of a patient's back pain, with interventions such as intraarticular steroid injection or neurolysis by radiofrequency or cryoablation to treat facetogenic pain.  , (Copyright © 2022, StatPearls Publishing LLC.)

Researchers do not agree on one comprehensive "fascia" definition. Despite the scientific uncertainty, there is an agreement with medical text that the fascia covers every structure of the body, creating a structural continuity that gives form and function to every tissue and organ.  The fascial tissue has a ubiquitous distribution in the body system; it is able to wrap, interpenetrate, support, and form the bloodstream, bone tissue, meningeal tissue, organs, and skeletal muscles. The fascia creates different interdependent layers with several depths, from the skin to the periosteum, forming a three-dimensional mechano-metabolic structure .  The Fascia and Its Effect on Individual Health  Three large groups of scholars have attempted to define fascia. The Federative Committee on Anatomical Terminology (FCAT), founded in 1989 from the General Assembly of the International Federation of Associations of Anatomists (IFAA), introduced the term "fascia superficialis" and "fascia profunda." The superficial fascia is a “whole loose layer of subcutaneous tissue lying superficial to the denser layer of fascia profunda.” The deep fascia, according to this definition, lies below the superficial fascia, highlighting two fasciae. In 2011, the Federative International Programme on Anatomical Terminologies (FIPAT), in agreement with FCAT, defined the fascia as “a sheath, a sheet, or any other dissectible aggregations of connective tissue that forms beneath the skin to attach, enclose, and separates muscles and other internal organs.” The FIPAT builds on the text of international anatomical terminology. The second definition specifies the term connective tissue, which functions to divide, separate, and support different structures. The connective tissue or fascia begins under the skin, excluding the epidermis from the fascia set. The third group of scholars is the Fascia Nomenclature Committee (2014), born from the Fascia Research Society founded in 2007. The board gave the following description of fascia: “The fascial system consists of the three-dimensional continuum of soft, collagen-containing, loose and dense fibrous connective tissues that permeate the body. It incorporates elements such as adipose tissue, adventitia, and neurovascular sheaths, aponeuroses, deep and superficial fasciae, epineurium, joint capsules, ligaments, membranes, meninges, myofascial expansions, periosteum, retinacula, septa, tendons, visceral fasciae, and all the intramuscular and intermuscular connective tissues including endo-/peri-/epimysium. The fascial system interpenetrates and surrounds all organs, muscles, bones and nerve fibers, endowing the body with a functional structure, and providing an environment that enables all body systems to operate in an integrated manner.” This is the broadest definition of fascia. The concept of a continuum of the collagen and connective structure, the cellular diversity that makes up the fascia, is emphasized. It is this continuum itself that assures the health of the body. These scientific definitions allow healthcare practitioners to make some deductions about fascia. The fascia includes everything that presumes the presence of collagen/connective tissue or from which it is derived. All the tissue considered as "specialized connective tissue" of mesodermal derivation is inserted into the fascial system. These include blood, bone, cartilage, adipose tissue, hematopoietic tissue, and lymphatic tissue. The fascial system has no discontinuity in its path, with layers of different characteristics and properties overlapping. A further research group for the nomenclature of the fascia founded in 2013: FORCE - Foundation of Osteopathic Research and Clinical Endorsement. The FORCE group has recently written several articles, highlighting new concepts to understand the concept of the fascia better: " The fascia is any tissue that contains features capable of responding to mechanical stimuli. The fascial continuum is the result of the evolution of the perfect synergy among different tissues, liquids, and solids, capable of supporting, dividing, penetrating, feeding, and connecting all the districts of the body: epidermis, dermis, fat, blood, lymph, blood and lymphatic vessels, tissue covering the nervous filaments (endoneurium, perineurium, epineurium), voluntary striated muscle fibers and the tissue covering and permeating it (epimysium, perimysium, endomysium), ligaments, tendons, aponeurosis, cartilage, bones, meninges, involuntary striated musculature and involuntary smooth muscle (all viscera derived from the mesoderm), visceral ligaments, epiploon (small and large), peritoneum, and tongue. The continuum constantly transmits and receives mechano-metabolic information that can influence the shape and function of the entire body.", (Copyright © 2022, StatPearls Publishing LLC.)

The genitofemoral nerve arises from the lumbar plexus. It supplies sensation to the skin of the anterior scrotal area in males, mons pubis in females, and the upper segment of the anterior thigh in both males and females. While distinct from the femoral nerve, the genitofemoral nerve originates from the upper lumbar segments L1-L2. It then descends inferiorly, piercing the psoas major muscle before emerging on its anterior surface. The nerve then traverses the retroperitoneum, descending over the anterior surface of the psoas muscle. The nerve continues inferiorly, ultimately separating into two divisions- the femoral and the genital branches. When the genitofemoral nerve reaches the groin area, it enters the deep inguinal ring coursing through the inguinal canal. In males, the nerve continues inferiorly and supplies the skin of the scrotum. In females, the genitofemoral nerve runs alongside the round ligament of the uterus and terminates just superior to the mons pubis and labia majora. Further, after crossing the inguinal ligament, the genitofemoral nerve travels adjacent to the external iliac artery, supplying sensation to the anterior upper thigh., (Copyright © 2022, StatPearls Publishing LLC.)

An ultrasound-guided ulnar nerve block can be used to provide surgical anesthesia or analgesia to the ulnar portion of the hand including the little finger and the ulnar half of the ring finger.  It is primarily used for surgical procedures in the distribution of the ulnar nerve both as a standalone block, combined with ulnar or radial nerve blocks for a complete hand block, or as a rescue method for inadequate brachial plexus blocks. An ulnar nerve block can be used as an alternative to sedation for painful procedures such as fracture reduction, and as a powerful adjunct for acute pain caused by burns. In patients that have sustained multiple lacerations needing repair, regional methods can be used to limit the total amount of local anesthetic used while obtaining surgical anesthesia to the affected area., (Copyright © 2022, StatPearls Publishing LLC.)

Radial nerve entrapment is an uncommon diagnosis that is prone to under-recognition. Compression or entrapment can occur at any location within the course of the nerve distribution, but the most frequent location of entrapment occurs in the proximal forearm. This most common location is typically in proximity to the supinator and often will involve the posterior interosseous nerve branch. The radial nerve arises from C5 to C8 and provides a motor function to the extensors of the forearm, wrist, fingers, and thumb. The superficial radial nerve provides a sensory function to the posterior forearm. Depending on the location of entrapment, a patient may experience pain, numbness, weakness, and overall dysfunction, or any combination of these., (Copyright © 2022, StatPearls Publishing LLC.)

Vertebral compression fractures (VCFs) of the spinal column occur secondary to an axial/compressive (and to a lesser extent, flexion) load with resultant biomechanical failure of the bone resulting in a fracture.  VCFs by definition compromise the anterior column of the spine, thereby resulting in compromise to the anterior half of the vertebral body (VB) and the anterior longitudinal ligament (ALL). This leads to the characteristic wedge-shaped deformity.  VCFs do not involve the posterior half of the VB and do not involve the posterior osseous components or the posterior ligamentous complex (PLC).  The former distinguishes a compression fracture from a burst fracture.  The implications of these compression fractures are related to the stability of the resulting structure and potential for deformity progression. Compression fractures are usually considered stable and do not require surgical instrumentation., (Copyright © 2022, StatPearls Publishing LLC.)

The musculature of the hand is deeply intricate, with several superimposed layers of muscles, tendons, and fascial compartments throughout. Complex interactions between these groups modulate specific movements, thus understanding their role in hand biomechanics can greatly enhance clinical evaluation and diagnosis for medical professionals. The thumb is one of the most important entities of the hand. Its versatility in movement compared to the other digits makes the hand the ultimate tool of elite dexterity. Because the thumb is orientated perpendicular to the other digits, its movements are modulated by a diverse set of specific muscles within the hand. Many muscles contribute to its movements, and one of the most important is the adductor pollicis. The adductor pollicis muscle is an intrinsic muscle of the hand which lies in the deepest muscular plane of the palm, within the adductor compartment. It is a unique muscle, in that it is triangular shaped with a 2-headed structure. The oblique head originates at the capitate as well as at the bases of the 2nd and 3rd metacarpals, while the transverse head originates from the volar aspect of the 3rd metacarpal. These two heads then merge as the fibers travel laterally, forming the tendon of the adductor pollicis which often contains a sesamoid bone. The tendon then inserts on the medial aspect of the proximal phalanx of the thumb as well as the extensor hood., (Copyright © 2022, StatPearls Publishing LLC.)

Camper's fascia is the superficial fatty layer of the anterior abdominal wall. This fascia is composed of loose areolar tissue and is found deep in the skin and superficial to Scarpa's fascia. Magnetic resonance imaging shows a 3-dimensional architecture of fibrous septae that functions to provide support to the adipose tissue. Camper's fascia spans from the xiphoid process to the seventh and 10th costal margins laterally and to the inguinal ligaments inferiorly. It continues inferiorly past the inguinal ligament as the subcutaneous fat of the thigh. Medially, the fascia extends past the pubic symphysis, combining with Scarpa's fascia to form the dartos tunic of the scrotum in males and the fatty tissue of the mons pubis and labia majora in females. Camper's fascia is important to understand due to its function, its location in surgery, and the role it plays in healing to form a strong barrier over the abdomen., (Copyright © 2022, StatPearls Publishing LLC.)

The vastus lateralis (VL) is a unipennate muscle and a member of the anterior compartment of the thigh along with the sartorius, quadriceps femoris, rectus femoris (RF), vastus medialis (VM), and vastus intermedius (VI) muscles. The VL is 1 of the 4 component muscles of the quadriceps muscle group: rector femoris, vastus lateralis, vastus medialis, and vastus intermedius. The vastus lateralis is the largest component of the quadriceps muscle groups and is positioned laterally about the femur., (Copyright © 2022, StatPearls Publishing LLC.)

Preoperative antibiotic prophylaxis is administering antibiotics before performing surgery to help decrease the risk of postoperative infections. The evidence supporting routine preoperative use of prophylactic antibiotic administration continues to grow. The routine administration of prophylactic antibiotics is standard in cases in which a patient will have an artificial implant or foreign body implanted as part of the procedure, bone grafting procedures, and other surgeries with extensive dissections and expectations for higher amounts of anticipated blood loss. This activity will highlight the rationale, timing, agent selection, coverage, and monitoring pertinent for interprofessional team members involved in the administration of preoperative antibiotic prophylaxis to patients., (Copyright © 2022, StatPearls Publishing LLC.)

The scalene muscles are deep and positioned laterally to the cervical tract. Their innervation is complex, as both the brachial plexus and the cervical plexus are involved in their function. They are multi-articular muscles, and their actions are just as complex and vital. They play the role of accessory breathing muscles but are also important for the movement of the neck and the head and maintaining the posture between the neck and the head. Their dysfunction creates several pathological patterns, such as thoracic outlet syndrome, decreased ventilatory capacity, and cervical pain. They are often the subject of medical approaches to diminish their tone and rehabilitative work to improve their physiological length or contractile strength. In this review, we will see how to apply stretching to the scalene muscles correctly and how to apply a manual differential diagnosis between the latter and the sternocleidomastoid muscle., (Copyright © 2022, StatPearls Publishing LLC.)

Complex Regional Pain Syndrome (CRPS) is a neuropathic pain disorder characterized by ongoing pain disproportionate to the degree of tissue injury and persists beyond the usual expected time for tissue healing.  Pain is accompanied by sensory, motor, and autonomic abnormalities. Such abnormalities include allodynia, hyperalgesia, sudomotor and vasomotor abnormalities, and trophic changes. Pain does not follow a particular dermatome or myotome but is rather regional. This disabling condition often develops after a trauma, fracture, or surgery. But some spontaneous cases have also been reported. In the 16th century, Ambroise Paré reported cases with CRPS like symptoms for the first time which developed after phlebotomy. In 1864, Silas Mitchell noted this syndrome after gunshot wounds. He used the term ‘causalgia’ to describe this syndrome in 1872. James A. Evans coined the term ‘reflex sympathetic dystrophy’ to describe a similar condition where he suspected sympathetically mediated pain in 1946.  Finally, in 1994, the International Association for the Study of Pain (IASP) named this condition ‘Complex Regional Pain Syndrome’ and proposed a diagnostic criterion. Due to low specificity, a widely accepted revised criterion was proposed in 2010 and is commonly referred to as the "Budapest Criteria." CRPS has two subtypes: type I, formerly known as reflex sympathetic dystrophy, and type II, formerly known as causalgia. Type I occurs in the absence of nerve trauma, while type II occurs in the setting of known nerve trauma. Clinically they are indistinguishable and follow a regional rather than a dermatomal or peripheral nerve distribution and favor the distal extremities, though spread outside of the initially affected area commonly occurs to the proximal or contralateral limb. CRPS is further subdivided into "warm" versus "cold," and sympathetically-maintained (SMP) versus sympathetically-independent (SIP), which may affect prognosis and treatment options. CRPS not only impacts function, sleep, and activities of daily living but also takes a significant mental and psychosocial toll on the patient. Its diverse spectrum of clinical presentation and lack of any clearly defined pathophysiology poses a challenge for optimal management of this disorder., (Copyright © 2022, StatPearls Publishing LLC.)

The submandibular triangle is an important anatomic landmark located underneath the body of the mandible. The majority of the anatomic space bounded by the submandibular triangle consists of the submandibular gland. The submandibular gland is the second largest salivary gland in the body (the parotid gland is the largest). In addition to housing the submandibular gland, a vast array of nerves, arteries, veins, and lymphatics course within the boundaries of the submandibular triangle. The complexity of the anatomy within the submandibular triangle makes for important clinical implications when performing surgery in this region. This article will focus on the anatomy contained within the borders of the submandibular triangle as well as the clinical significance and implications of surgery in this area., (Copyright © 2022, StatPearls Publishing LLC.)

The gastrocnemius muscle is a complex muscle that is fundamentally involved in walking and posture. It affects the entire lower limb and the movement of the hip and the lumbar area. It is a muscular district called to work during daily and sports activities and maintain orthostatism. This article reviews the anatomical and functional information of the gastrocnemius muscle and its embryological derivation. This review will also illustrate the vascular and lymphatic network and the innervating nerve branch. The text describes the concept of fascial continuum, which explains the influence of a muscular district compared to those bordering and distant. It highlights the anatomical variants such as gastrocnemius tertius or quadriceps gastrocnemius. The text describes some pathological conditions and surgical approaches related to gastrocnemius and the muscle's instrumental and palpatory clinical evaluation. The paper concludes by describing conservative approaches in cases of calf dysfunction, such as physiotherapy and osteopathy. The important reflection from the text is that a contractile district relates to the body system, and it is limiting to consider a muscle only as an anatomical segment., (Copyright © 2022, StatPearls Publishing LLC.)

The humerus is the largest bone of the upper extremity and defines the human brachium (arm). It articulates proximally with the glenoid via the glenohumeral (GH) joint and distally with the radius and ulna at the elbow joint. The most proximal portion of the humerus is the head of the humerus, which forms a ball and socket joint with the glenoid cavity on the scapula. Just inferior to the head of the humerus is the anatomical neck of the humerus, which divides the head of the humerus from the greater and lesser tubercles. The anatomical neck of the humerus is the residual epiphyseal plate. An intertubercular groove appears proximally, which demarcates the two tubercles vertically. Following the tubercles is the surgical neck of the humerus, a site commonly susceptible to fractures. Continuing distally is the cylindrical-shaped shaft of the humerus, which contains a deltoid tubercle on its lateral aspect and a radial groove on its posterior aspect (also referred to as the spiral groove). At the distal portion of the humerus, there exists a widening of the bone that forms the medial and lateral epicondyles. The distal portion of the humerus ends with an area referred to as the condyle, which is composed of the trochlea, capitulum, olecranon, coronoid and radial fossae.  On the anterior lateral surface of the condyle is the lateral capitulum, which articulates with the head of the radius bone, and on the anterior medial surface of the condyle is the trochlea, which articulates the trochlear notch of the ulna bone. The coronoid fossa is located superior to the trochlea and accommodates the coronoid process of the ulna and superior to the capitulum on the anterior surface of the condyle, which is the radial fossa which receives with the head of the radius, both upon flexion of the elbow joint. On the posterior surface of the condyle is the olecranon fossa, which articulates with the olecranon of the ulnar bone upon flexion of the elbow joint., (Copyright © 2022, StatPearls Publishing LLC.)

The anterior interosseous nerve (AIN) is the terminal motor branch of the median nerve.  It branches from the median nerve in the proximal forearm between the two heads of the pronator teres muscle to run deep along the interosseous membrane. From proximal to distal, it innervates the flexor pollicus longus (FPL), the index and long fingers of the flexor digitorum profundus (FDP), and the pronator quadratus (PQ). AIN syndrome is an isolated palsy of these three muscles. It manifests mostly as pain in the forearm accompanied frequently by a characteristic weakness of the index and thumb finger pincer movement. Many cases of AIN syndrome arise secondary to transient neuritis, although nerve compression and trauma are known etiologies as well. Different explanations have been proposed as the etiology of the disease. Controversy still exists among upper extremity surgeons about it; nevertheless, the condition is considered a neuritis in most cases. Parsonage and Turner first described the syndrome in 1948. Leslie Gordon Kiloh and Samuel Nevin defined it as an isolated lesion of the anterior interosseous nerve in 1952. Its old name was Kiloh-Nevin syndrome. Different methods of treatment with reasonable outcomes have been reported. Both surgical and medical interventions have been addressed with different timing and variable results., (Copyright © 2022, StatPearls Publishing LLC.)

The musculocutaneous nerve is a terminal branch of the lateral cord of the brachial plexus that carries fibers of cervical spinal nerves five through seven (i.e., C5, C6, and C7). The musculocutaneous nerve leaves the axilla and rapidly descends into the coracobrachialis muscle fibers. The musculocutaneous nerve supplies the biceps brachii and brachialis muscles as it descends between them within the anterior compartment of the arm. The musculocutaneous nerve changes names as it passes lateral to the tendon of the biceps brachii, where it changes its name to the lateral cutaneous nerve of the forearm, also known as the lateral antebrachial cutaneous nerve. This nerve mainly provides motor innervation to the anterior compartment of the arm and returns cutaneous sensation from the lateral forearm., (Copyright © 2022, StatPearls Publishing LLC.)

Spondylolysis refers to a posterior defect of the vertebral body occurring at the pars interarticularis. Typically, this defect results from trauma or chronic repetitive loading and hyperextension. If this instability leads to translation of the vertebral body, this is spondylolisthesis. This process requires either a fracture or deformation of the posterior spinal elements resulting in elongation of the pars interarticularis. This condition can potentially occur in all age groups, with the underlying cause varying based on age. If the slip progresses to the point of neurologic compromise, then surgical intervention may be necessary to decompress and stabilize affected segments. Absent any motor deficits, a nonoperative course of analgesia, activity modification, and injections should be the initial therapeutic approach for several months., (Copyright © 2022, StatPearls Publishing LLC.)

Polymerase chain reaction (PCR) refers to a technique employed widely in the basic and biomedical sciences. PCR is a laboratory technique utilized to amplify specific segments of DNA for a wide range of laboratory and/or clinical applications. Building on the work of Panet and Khorana’s successful amplification of DNA in-vitro, Mullis and coworkers developed PCR in the early 1980s, having been met with a Nobel prize only a decade later. Allowing for more than the billion-fold amplification of specific target regions, it has become instrumental in many applications including the cloning of genes, the diagnosis of infectious diseases, and the screening of prenatal infants for deleterious genetic abnormalities., (Copyright © 2022, StatPearls Publishing LLC.)

The accessory spinal nerve or XI cranial nerve is essential for neck and shoulder movement, the intrinsic musculature of the larynx, and the sensitive afferences of the trapezius and sternocleidomastoid musculature. It can suffer an injury with daily movements or behaviors that exceed the elastic capacity of the nerve structure, such as excessive stretching or carrying heavyweights. These types of injuries are generally benign. The nerve may be seriously injured if the patient undergoes extensive tumor mass-removal surgery in the neck area, and there is a lack of blood nutrition or partial removal. When necessary, its removal becomes essential to compensate for a peripheral nerve lesion, transfer the cranial nerve where electrical activity is lacking, and efforts to restore limb function., (Copyright © 2022, StatPearls Publishing LLC.)

The foramen magnum is of interest for various scientific disciplines: forensic and physical anthropology; comparative anatomy; biology; surgery of the foramen structures and for the craniovertebral junction. There are morphological differences between men and women. The sagittal diameter is greater in the male, as is the transverse diameter. The foramen magnum is the largest foramen of the skull. It is located in the most inferior portion of the cranial fossa as a part of the occipital bone. Its contents include the medulla oblongata, meninges, spinal root of cranial nerve XI, vertebral arteries, anterior and posterior spinal arteries, the tectorial membrane, and alar ligaments. On the foramen magnum, there are two craniometric points: the basion, the median point of the front edge of the hole, and the opisthion, posterior correspondence., (Copyright © 2022, StatPearls Publishing LLC.)

The area between the lumbar vertebral bodies and sacral vertebral bodies is a transition zone at increased risk of injury due to the change in biomechanics that occurs between these regions. Separating each vertebral body of the spine are pads of fibrocartilage-based structures that provide support, flexibility, and minor load sharing known as the intervertebral discs. These are primarily composed of two layers, a soft, pulpy nucleus pulposus on the inside of the disc and a surrounding firm structure known as the annulus fibrosus . An injury to the normal architecture of the disc's annulus fibrosus can lead to degeneration or a protrusion of the inner nucleus pulposus, possibly applying pressure to the spinal cord or nerve root resulting in pain and weakness. Slightly more than 90% of herniated discs occur at the L4-L5 or the L5-S1 disc space. If the disc injury progresses to the point of neurologic compromise or limitations with activities of daily living, then surgical intervention may be required to decompress and stabilize the affected segments. A non-operative course of analgesia, activity modification and injections should be tried for several months in the absence of motor deficits., (Copyright © 2022, StatPearls Publishing LLC.)

Snapping hip syndrome, also known as coxa saltans ( or dancer’s hip),  is a clinical condition characterized by an audible or palpable snapping sensation that is heard during movement of the hip joint. Snapping hip has multiple etiologies and is classified based on the anatomic structure that is the cause/source of the snapping sensation. Historically, two main snapping hip categories were recognized: Extra-articular. Intra-articular. The term intra-articular snapping hip  has relatively fallen out of favor due to the increasing knowledge of intra-articular pathologies.  These etiologies include loose bodies (e.g. secondary to synovial chondromatosis) or labral tears of the hip. As the clinical terminology evolved, extra-articular snapping hip eventually became subclassified into: External snapping hip. Internal snapping hip. External snapping hip is most commonly attributed to the iliotibial band moving over the greater trochanter of the femoral head during hip movements in flexion, extension, and external or internal rotation.  Other causes include the proximal hamstring tendon rolling over the ischial tuberosity, either the fascia lata or the anterior aspect of the gluteus maximus rolling over the greater trochanter, and the psoas tendon rolling over the medial fibers of the iliacus muscle. A combination of defects is also possible; for example, thickening of both the posterior iliotibial band and anterior gluteus maximus, which snap over the greater trochanter at the same time.  Internal snapping hip most commonly occurs as the iliopsoas tendon snaps over underlying bony prominences, such as the iliopectinal eminence or the anterior aspect of the femoral head. Other causes include paralabral cysts and partial or complete bifurcation of the iliopsoas tendon. The snapping sensation can closely mimic intra-articular pathology since they both originate from the anterior hip area. Close physical exams and imaging can differentiate the two. It should be noted, however, that in approximately 50% of internal snapping hip cases, an additional intra-articular hip pathology is identified., (Copyright © 2022, StatPearls Publishing LLC.)

Basilar Invagination (BI) was first described by Ackermann in cretins. Schuller gave the first radioimaging diagnosis which Chamberlain and other radiologists later refined. BI is an abnormality at the craniovertebral junction, either congenital or degenerative, resulting in the odontoid prolapsing into the already limited space of the foramen magnum. It is commonly associated with conditions such as Chiari malformation, syringomyelia, and Klippel-Feil syndrome. Clinical presentations can range from chronic headaches, limited neck motion, and acute neurologic deterioration. CT and MRI are critical to diagnosing and managing this condition, including operative planning when needed. Determining the need for operative intervention is controversial in asymptomatic patients, but those at risk of neurologic compromise could require preoperative cervical traction and algorithmic surgical strategies., (Copyright © 2022, StatPearls Publishing LLC.)

The quadratus lumborum (QL) muscle resides in the deep and posterior, lateral, and inferior areas of the spine, involving the iliac crest, the transverse processes of the lumbar vertebrae, and the 12th rib. The muscular organization is complex, and it is difficult to identify precisely the actions that occur through the contraction of fibers. It is an integral part of the thoracolumbar fascia. There is still no certainty that an abnormality of QL is the primary source of back pain. The QL could potentially act as a crossroad of the forces exerted by the neighboring muscles, influencing the vectors of the different tensions produced. Thanks to its strategic position and the entropic scheme of its fibers, QL is a significant means of access for anesthesia during surgery on the back, lower limbs, or abdominal area. The article reviews the latest anatomical and clinical information on the quadratus lumborum., (Copyright © 2022, StatPearls Publishing LLC.)

Low-molecular-weight heparins (LMWHs), for example, dalteparin, enoxaparin, among others, are anticoagulants. These drugs are used in the prophylaxis of venous thromboembolic disease (VTE) on acute or elective admission to the hospital, and they are used in the treatment of deep vein thromboses (DVT) and pulmonary embolism (PE). This activity will highlight the mechanism of action, adverse event profile, pharmacology, monitoring, and relevant interactions of LMWH, pertinent for members of the interprofessional team in the treatment of patients with conditions where this agent is indicated., (Copyright © 2022, StatPearls Publishing LLC.)

The tendon is a "mechanical bridge." It allows the transmission of muscle strength to the bones and joints, on the other it allows the contraction of the muscle to make the final tangible movement. There are different types of tendons which reflect the morphology of the muscle and their specific function. Tendon tissue is not just about the terminal or initial area of each muscle but involves the entire muscular tissue. The connective layers (epimysium, perimysium, and endomysium) merge into a single organization to make contact with one or more fixed bone points. The same tendon near the muscle has contractile fibers. The muscle affects the tendon, and the tendon affects the functional expression of the muscle. In the context of manual therapy, rehabilitation, or surgery, it is a mistake not to consider these close relationships of anatomy and function. The tendon tissue can adapt its cellular structure under physiological (training) or pathological (trauma) stimuli, depending on the systemic hormonal environment and age., (Copyright © 2022, StatPearls Publishing LLC.)

Osteoporosis is defined as low bone mineral density caused by altered bone microstructure, ultimately predisposing patients to low-impact, fragility fractures. Osteoporotic fractures lead to a significant decrease in quality of life, increasing morbidity, mortality, and disability. Over 50% of postmenopausal white women will have an osteoporotic-related fracture. Only 33% of senior women who have a hip fracture will be able to return to independence. In white men, the risk of an osteoporotic fracture is 20%, but the one-year mortality in men who have a hip fracture is twice that of women. Black males and females have less osteoporosis than their white counterparts, but those diagnosed with osteoporosis have similar fracture risks. The aging of the American population is expected to triple the number of osteoporotic fractures., (Copyright © 2022, StatPearls Publishing LLC.)

Klumpke palsy, named after Augusta Dejerine-Klumpke, is a neuropathy involving the lower brachial plexus. In contrast, the more common Erb–Duchenne palsy involves the more cephalic portion of the brachial plexus C5 to C6. The brachial plexus is a bundle of individual nerves that exit between the anterior and middle scalene muscles in the anterior lateral and basal portion of the neck. Although the most common anatomical presentation of the brachial plexus is between the anterior and middle scalene, there are variations, with the most common being penetration of the anterior scalene. The main mechanism of injury to the lower brachial plexus is hyper-abduction traction, and depending on the intensity, it will lead to signs and symptoms consistent with a neurological insult., (Copyright © 2022, StatPearls Publishing LLC.)

Glycolysis is a metabolic pathway and an anaerobic energy source that has evolved in nearly all types of organisms. Another name for the process is the Embden-Meyerhof pathway, in honor of the major contributors towards its discovery and understanding. Although it doesn't require oxygen, hence its purpose in anaerobic respiration, it is also the first step in cellular respiration. The process entails the oxidation of glucose molecules, the single most crucial organic fuel in plants, microbes, and animals. Most cells prefer glucose (although there are exceptions, such as acetic acid bacteria that prefer ethanol). In glycolysis, 2 ATP molecules are consumed, producing 4 ATP, 2 NADH, and 2 pyruvates per glucose molecule. The pyruvate can be used in the citric acid cycle or serve as a precursor for other reactions., (Copyright © 2022, StatPearls Publishing LLC.)