The Upper Limb Anatomy PDF

Anatomy Prof. Laura Mangiavini 10/11/2023 Sbobina (no. 4) THE UPPER LIMB - 1 Last time, we began by reviewing the glenohumeral joint. We mentioned that the...

Anatomy Prof. Laura Mangiavini 10/11/2023 Sbobina (no. 4) THE UPPER LIMB - 1 Last time, we began by reviewing the glenohumeral joint. We mentioned that the shoulder consists of five joints: three true joints and two false joints. In our previous session, we primarily focused on the bony aspects, particularly the glenohumeral joint. The last slide covered the head of the humerus, which is much larger than the glenoid cavity. The glenoid cavity is characterized by the glenoid labrum, which completely surrounds it. The labrum plays a crucial role—it widens the cavity and, of course, enhances the stability of the glenohumeral joint. It's important to note that the glenohumeral joint is inherently unstable. Its stability doesn't come from the bony components but rather from the glenoid labrum, the joint capsule, and the ligaments, which we will discuss further The second true joint is the acromioclavicular joint, formed by the distal end of the clavicle and the acromial process of the scapula. This is also a true joint, meaning there is a joint cavity with articular cartilage and synovial fluid. The acromioclavicular joint is not highly mobile but is very stable due to the presence of ligaments. Primarily, there are anterior and posterior ligaments that stabilize the joint. Additionally, there are the coracoclavicular ligaments—namely, the trapezoid and conoid ligaments—that extend from the coracoid process to the clavicle. The trapezoid ligament is more lateral, while the conoid ligament is more medial, running from the coracoid process to the distal end of the clavicle. This joint is characterized by its stability and limited mobility. In cases of acromioclavicular dislocation, the ligaments, including the acromioclavicular and coracoclavicular ligaments, can be torn, leading to a superior dislocation of the clavicle. This condition is often a result of direct trauma and may cause fractures in the ligaments, resulting in a superior dislocation of the clavicle. The third true joint is the sternoclavicular joint, involving the proximal end of the clavicle and the proximal part of the sternum. This is the sole joint that essentially connects the upper limb to the thorax and is also a true joint, featuring a joint cavity with synovial fluid and synovial cartilage. Between the two bone segments, there is an articular disk, serving as a sort of meniscus. This joint is characterized by stability and limited mobility. It is stabilized by the joint capsule and various ligaments, including the interclavicular ligament that stabilizes the two clavicles. The anterior and posterior sternoclavicular ligaments surround the joint capsule and sternal capsule. Federica Rizzo, Carolina Ubaldo Pag.1 Anatomy Prof. Laura Mangiavini 10/11/2023 Additionally, there is a connection between the clavicle and the first rib through the costo-clavicular ligaments. There are two interclavicular ligaments connecting the sternum with the clavicle, namely the costo-clavicular ligament linking the clavicle to the first rib. In the anterior part of the joint, there is the anterior sternoclavicular ligament, while posteriorly, there is the posterior sternoclavicular ligament. The articular disk between the clavicle and the sternum acts as a sort of pillow between the three bone segments, allowing the formation of biomechanical forces. Similar to the acromioclavicular joint, the sternoclavicular joint is highly stable, and its mobility is significantly reduced. We've covered the main bony parts of the three true joints and the two false joints, which essentially serve as sliding spaces for muscles. The first is the subdeltoid joint, also known as the subacromial joint. It's a space located between the acromion superiorly, the coracoacromial ligament, and the humerus, with the rotator cuff muscles positioned inferiorly. This space, situated between the acromion and the humeral head, facilitates the sliding of the rotator cuff tendons, especially the supraspinatus tendon. Superiorly, we find the acromion, the coracoacromial ligament, and the deltoid muscle. Inferiorly, the rotator cuff tendons, particularly the supraspinatus, and the head of the humerus are present. Within this space, there's also a bursa made of fibrous tissue, acting like a cushion between the acromion and the rotator cuff tendons. This space is defined superiorly by the inferior side of the acromion, the coracoid-acromial ligament, and the inner part of the deltoid muscle. The inferior surface is formed by the head of the humerus covered by the supraspinatus tendon, with the bursa in between. The subacromial bursa serves to protect the supraspinatus tendon from impingement with the acromial surface. This space is crucial, as a reduction in its size leads to what we term as subacromial impingement. In this condition, the supraspinatus tendon primarily impinges with the acromion and the coracoclavicular ligament. Over time, this impingement can result in inflammation and subsequent degeneration of the tendon, representing a primary cause of rotator cuff tears. Subacromial impingement is typically the initial stage in the development of rotator cuff tears. Various factors can contribute to subacromial impingement. For instance, the shape of the acromion plays a role; variations such as a more angular or thicker acromion can reduce the space available. Additionally, conditions like osteoarthritis of the acromioclavicular joint, involving ossification at the acromial level, can cause a reduction in the subacromial space. Any factor leading to a reduction in Federica Rizzo, Carolina Ubaldo Pag.2 Anatomy Prof. Laura Mangiavini 10/11/2023 this space triggers impingement, subsequently increasing the risk of rotator cuff tears, given the close proximity of the supraspinatus tendon just beneath the subacromial bursa. The subacromial bursa is inside the subacromial joint? “Yes, and it basically covers the supraspinatus tendon” In cases of impingement, the sequence of events typically begins with inflammation of the bursa, followed by inflammation of the tendon. Subsequently, the tendon undergoes progressive degeneration, ultimately leading to a complete tear. The scapulothoracic joint, a false joint, serves as a crucial sliding surface that significantly impacts shoulder kinematics and scapular movement. Positioned between the thoracic wall and the scapula, this joint can be conceptually divided into two spaces The first space lies posteriorly between the scapula and the subscapularis muscle, and anteriorly between the scapula and the serratus anterior muscle. The serratus anterior muscle effectively divides this joint into two spaces. The second space is defined medially and anteriorly by the thoracic wall and posteriorly by the serratus anterior muscle. This arrangement allows for the dynamic movements of the scapula, spanning from the second to the seventh rib. The scapula itself extends from the first thoracic rib to the seventh or eighth rib and thoracic vertebral bodies. Notably, the medial extremity of the spine of the scapula corresponds to the third thoracic vertebral body. The medial spinal border typically lies 5 to 6 cm away from the thoracic vertebra. Having covered the articular structures of the joints, let's transition to exploring the ligaments and tendons of the shoulder complex. In the scapulo-humeral or gleno-humeral joint, the coraco- humeral ligament plays a pivotal role. It connects the coracoid process to the head of the humerus, fortifying the joint capsule that envelops the head of the humerus and the glenoid cavity. Notably, this ligament forms a tunnel through which the tendon of the biceps—the long tendon of the biceps—passes. As we'll delve into later, it's important to note that this tendon is intra-articular, originating physically from the superior part of the glenoid cavity and exiting at the level of this joint. At the level of the glenohumeral joint, three primary ligaments significantly reinforce the joint capsule: the superior, middle, and inferior glenohumeral ligaments. These ligaments essentially encircle the joint capsule, providing crucial stability. The long head of the biceps originates from the superior part of the glenoid cavity and exits at the joint level, while the short head originates from the coracoid process. Functionally, ligaments serve to physically restrict movements, and in the case of the glenohumeral joint, they play a vital role in limiting movement and imparting stability. The Federica Rizzo, Carolina Ubaldo Pag.3 Anatomy Prof. Laura Mangiavini 10/11/2023 superior, inferior, and middle glenohumeral ligaments, combined with the coraco-humeral ligament, collectively limit extension and abduction. The inferior glenohumeral ligament acts as a sling, resembling a hammock, stabilizing the head of the humerus during abduction. This stabilization prevents the inferior dislocation of the humeral head during extreme abduction. In the absence of this ligament or if it is torn, there is a risk of inferior dislocation of the humeral head.. The long head tendon of the biceps plays a crucial role in stabilizing the head of the humerus. It works in concert with the rotator cuff tendons to exert downward pressure on the humeral head, ensuring its stability within the glenoid cavity, particularly during abduction. This mechanism helps prevent superior dislocation of the humeral head. On the other hand, the short head of the biceps, originating from the coracoid process, prevents the downward dislocation of the humeral head. Together, the long head of the biceps and the rotator cuff muscles press the humeral head into the glenoid cavity, effectively resisting superior dislocation. Degeneration of the long head tendon, coupled with rotator cuff degeneration, can lead to progressive superior dislocation of the humeral head, resulting in impingement against the acromion. Rupture of this tendon can lead to a significant 20% decrease in the strength of abduction. The biceps, composed of the long and short heads, originates from the coracoid process, sharing its origin with two other muscles: the coracobrachialis and the pectoralis minor. Further details on these muscles will be explored later. The two heads of the biceps merge to form the muscle, which features a spinal tendon at the elbow level, attaching to the tuberosity of the radius. When discussing shoulder muscles, we can categorize them into three main groups: muscles connecting the shoulder girdle to the trunk and to the neck and skull, muscles connecting the scapula to the humerus, and muscles connecting the trunk directly to the humerus without attachment to the scapula. The shoulder girdle which part of the shoulder comprises? All the shoulder, all the shoulder joints (true and false). Federica Rizzo, Carolina Ubaldo Pag.4 Anatomy Prof. Laura Mangiavini 10/11/2023 Now, let's explore the first group of muscles: those connecting the trunk to the shoulder girdle. The serratus anterior, previously discussed in the context of the scapulothoracic joint, originates from the anterolateral aspect of the thorax, spanning from the first to the ninth rib. Its insertion is along the medial border of the scapula. The serratus anterior primarily contributes to abduction, causing the scapula to move away from the body's midline, and it also plays a key role in the upward rotation of the scapula, particularly acting on the scapulothoracic joint. The trapezius is a substantial muscle with a broad origin, spanning from the occipital bone to the spinal processes of the cervical and thoracic vertebrae. Its attachments include the clavicle, acromion, and the spine of the scapula. Functionally, the trapezius can be divided into three parts: upper, middle, and lower trapezius. The upper trapezius, highlighted in orange, is responsible for elevating and upwardly rotating the scapula. Additionally, it plays a role in neck movements, contributing to cervical spine extension, lateral flexion, and contralateral rotation. The lower trapezius, depicted in purple, facilitates downward rotation, adduction (bringing the scapula towards the midline of the body), and depression of the scapula, pressing it against the thoracic wall. The middle trapezius supports these actions by assisting in upward rotation and adduction of the scapula. Primarily, the trapezius acts on the scapula and also influences movements of the cervical spine.. Another set of muscles connecting the trunk to the shoulder girdle are the rhomboid muscles— specifically, the major and minor rhomboids. These muscles originate from the ligamentum nuchae, connecting spinal processes, as well as from the spinal processes of the lower cervical vertebrae and the first four thoracic vertebral bodies. Their attachment point is on the medial border of the scapula. The rhomboid muscles collectively contribute to downward rotation, adduction, and elevation of the scapula. It's noteworthy that discomfort or pain in the shoulder and cervical spine region is often associated with contraction of the rhomboid muscles, particularly in the middle part of the scapula. Anteriorly, we have the pectoralis minor, as depicted on the right, which originates from the second to the fifth rib. Its insertion point is on the Federica Rizzo, Carolina Ubaldo Pag.5 Anatomy Prof. Laura Mangiavini 10/11/2023 coracoid process. The pectoralis minor contributes to the depression of the scapula, effectively pressing it against the thoracic wall. Additionally, it plays a role in the elevation of the ribs. The final muscle in this group is the levator scapulae, originating from the transverse processes of the cervical vertebrae and extending to the medial upper border of the scapula. It functions to elevate the scapula and contribute to its downward rotation. Additionally, it plays a role in cervical spine movements, performing lateral flexion and ipsilateral rotation. This muscle is often implicated in pain, especially in conditions such as spondyloarthritis of the cervical spine, after a car accident, or due to pathological contractions, leading to pain radiating from the cervical spine to the scapula. What is spondyloarthritis? Spondyloarthritis basically means arthritis of the spine, is a genetic term referred to this condition. The second group of muscles consists of those connecting the shoulder girdle to the humerus. The first in this group is the deltoid muscle, a major player in the glenohumeral joint. This substantial muscle originates from the distal part of the clavicle, the acromion, and the spine of the scapula. The anterior part primarily originates from the clavicle, the intermediate part from the acromion (depicted in green), and the posterior part from the spine of the scapula. The deltoid muscle attaches to the intermediate area of the humerus's diaphysis at the deltoid tuberosity. Its main action is the abduction of the glenohumeral joint. Additionally, the anterior part (highlighted in red) performs flexion and horizontal abduction of the glenohumeral joint, while the posterior part contributes to extension of the glenohumeral joint. Following the deltoid, we have the rotator cuff muscles, a group of four muscles connecting the shoulder girdle to the humerus. The first muscle in the rotator cuff group is the supraspinatus, originating from the supraspinal processes of the scapula, specifically the posterior part. It attaches to the greater tubercle of the head of the humerus, specifically the anterior part of the Federica Rizzo, Carolina Ubaldo Pag.6 Anatomy Prof. Laura Mangiavini 10/11/2023 greater tubercle. Being the most superficial muscle of the rotator cuffs, the supraspinatus and its tendon are particularly susceptible to degeneration in cases of subacromial impingement. The tendon passes underneath the acromion to reach the greater tubercle. The main action of the supraspinatus is the abduction of the glenohumeral joint, working in conjunction with the deltoid. Additionally, along with the other rotator cuff muscles and the long head of the biceps, the supraspinatus plays a crucial role in stabilizing the head of the humerus and the glenoid cavity. Together, these muscles exert downward pressure on the humeral head, preventing superior dislocation. The infraspinatus muscle originates from the infraspinous fossa of the posterior scapula and attaches to the greater tubercle of the humerus, positioned posteriorly to the supraspinatus muscle. Its primary action is the external rotation of the glenohumeral joint. Teres minor, the third muscle of the rotator cuff, originates in close proximity to the infraspinatus muscle, situated on the lateral inferior border of the scapula. It inserts onto the lower posterior facet of the greater tubercle. Teres minor plays a supportive role alongside the infraspinatus in the external rotation of the glenohumeral joint. The fourth and final muscle of the rotator cuff group is the subscapularis. It originates from the anterior part of the scapula in the subscapularis fossa and inserts onto the lesser tubercle, the anterior tubercle of the humerus. With a distinct origin, the subscapularis serves a unique function. As the primary internal rotator of the glenohumeral joint, it is responsible for internal rotation. Additionally, depending on the arm's rotation, the subscapularis can assist in flexion, extension, or adduction of the glenohumeral joint, but its principal role is internal rotation. Teres major, in contrast to teres minor, originates from the inferior angle of the scapula and inserts distally to the lesser tubercle of the humerus, specifically on the posterior, inferior part of the proximal humerus. Its primary actions include internal rotation, adduction, and extension of the glenohumeral joint. Now, turning our attention to muscles connecting the trunk to the humerus without attachment to the scapula, we have the pectoralis major. This muscle has a dual origin, partially from the clavicle (specifically the proximal Federica Rizzo, Carolina Ubaldo Pag.7 Anatomy Prof. Laura Mangiavini 10/11/2023 part) and partially from the sternum and costal cartilage of the ribs. It inserts on the anterior part of the humerus. The main actions of the pectoralis major include adduction and internal rotation of the glenohumeral joint. Additionally, the clavicular head is responsible for flexion of the glenohumeral join. Lastly, we have the latissimus dorsi, an extensive muscle with origins spanning from the sixth thoracic vertebra (T6) down to all the spinal processes of the lumbar spine. Additionally, it originates from the posterior iliac crest, sacrum, and the lower ribs. Its insertion is in close proximity to the teres major on the medial posterior part of the proximal humerus. The latissimus dorsi is involved in a variety of movements, including internal and external rotation, adduction of the glenohumeral joint, and it also contributes to scapular depression. Kinematics In the context of glenohumeral joint movements, we can execute various actions: Flexion and Extension: These movements occur on a sagittal plane. Flexion involves bringing the arm anteriorly, boasting a considerable range (from 0 to 180 degrees). In contrast, extension entails moving the arm posteriorly and has a more limited range, typically up to 50°. Adduction and Abduction: Adduction involves bringing the arm toward the body's midline, while abduction entails moving the arm away from the midline. Pure adduction movement, when starting from the reference position with arms close to the trunk, is not possible and must be combined with either extension or flexion. In this scenario, the combined movements are: Adduction and Flexion: Bringing the arm anteriorly and closer to the midline, with a range of up to 45 degrees Adduction and Extension: A limited movement where the arm is brought posteriorly and close to the midline. Abduction is the movement that takes the arm away from the middle line. At the shoulder joint, different phases of abduction can be distinguished: 0 to 60 degrees: In this initial phase, the movement primarily involves the glenohumeral joint. 50 to 120 degrees: During this phase, additional movement of the scapulothoracic joints is required. The scapula must rotate to facilitate this range of abduction. Federica Rizzo, Carolina Ubaldo Pag.8 Anatomy Prof. Laura Mangiavini 10/11/2023 120 to 180 degrees: This advanced phase involves movement at both the shoulder joint and the scapulothoracic joint, along with flexion of the trunk. Extreme flexion after 90 degrees brings the upper limb close to the sagittal plane In summary, abduction involves a complex interplay of movements at the shoulder joint, scapulothoracic joint, and trunk flexion.. Abduction is a crucial movement as it is the most frequently performed by the glenohumeral joint, enabling a wide range of actions in the upper limb. Muscles that perform abduction: The deltoid muscle serves as the primary abductor, capable of achieving the complete range of abduction from 0 to 180 degrees. However, its efficiency is notably pronounced around the 90-degree mark. In the initial phase of abduction, the supraspinatus acts as a synergistic abductor alongside the deltoid muscle, enhancing overall efficiency. This collaboration, along with other rotator cuff muscles, serves to prevent superior dislocation of the humeral head—a risk associated with the deltoid's action. The supraspinatus remains actively engaged in the abduction movement from 0 to 90 degrees. Between 90 to 150 degrees of abduction, the scapulothoracic joint comes into play, involving a swing and rotation of the scapula. This movement ensures that the glenoid cavity maintains its supine orientation, staying in contact with the humeral head to prevent dislocation. Beyond 150 degrees, the thoracic spine contributes, incorporating lateral flexion into the abduction process. Rotation In addition to flexion, extension, adduction, and abduction, the glenohumeral joint is capable of rotation along the long axes of the arm. This rotational movement can be categorized into external and internal rotation, commonly referred to as outer and inner rotation, respectively. From the reference position, where the elbow is flexed, and the arm is close to the trunk, external rotation involves moving the forearm, wrist, and hand laterally. Conversely, internal rotation brings Federica Rizzo, Carolina Ubaldo Pag.9 Anatomy Prof. Laura Mangiavini 10/11/2023 the forearm, hand, and wrist medially. Rotations can also be executed from various positions of abduction. For instance, abduction external rotation involves bringing the arm posteriorly. From the reference position, lateral rotation (also known as external or outer rotation) can achieve up to 80 degrees, whereas internal rotation has a wider range, reaching up to 110 degrees. To assess the function of the subscapularis, the primary internal rotator, the lift-off test is commonly performed. In this test, the patient is asked to push against the examiner's hand in the reference position The primary external rotators include the infraspinatus and the teres minor, while the internal rotators consist of the subscapularis, teres major, latissimus dorsi, and pectoralis major. In the rotational movement, the serratus anterior contributes to a slight adduction of the scapula, and during abduction, the trapezius and rhomboid muscles are involved abduction. The arm The only bone present in the upper arm is the humerus, of which we have already examined the proximal part. In the diaphysis, notable points include the deltoid tuberosity, serving as the insertion point for the deltoid muscle. Posteriorly, the radial groove houses the passage for the radial nerve, which is closely associated with the humerus. In cases of fracture, it is crucial to assess nerve function. Moving downward, we reach the distal part of the humerus, which is a component of the elbow joint In the arm, there is a muscular component, with a superficial layer of muscles primarily represented by the biceps. The long head, short head, and distal tendon insert on the radial tuberosity of the proximal part of the bone. Federica Rizzo, Carolina Ubaldo Pag.10 Anatomy Prof. Laura Mangiavini 10/11/2023 Another muscle on the anterior part of the arm is the coracobrachialis, which originates from the coracoid process and inserts on the inner side of the middle part of the humeral diaphysis. Lastly, we have the brachialis muscle, originating from the anterior part of the humerus, with its insertion on the proximal anterior face of the ulna. The biceps and the brachialis serve as the primary flexors of the elbow. Posteriorly in the arm, the main muscle is the triceps, which is composed of three parts: the long head, a bi-articular muscle originating from the inferior part of the glenoid cavity and affecting two joints, and the lateral and medial heads, both originating from the posterior proximal part of the humerus. The lateral head originates laterally, and the medial head, deeper compared to the other two, originates from the middle. Both lateral and medial heads act solely on the elbow joint. The three parts of the triceps—long head, lateral head, and medial head—converge to create a single tendon known as the triceps tendon. This tendon inserts on the olecranon process of the ulna Elbow The elbow serves as the intermediate joint between the upper arm and the forearm, forming a pivotal connection that enables the wrist to nearly reach the shoulder when the upper arm and forearm act like a pair of compasses. The bony components constituting this joint include the distal epiphysis of the humerus, along with the proximal epiphyses of the radius and ulna. Federica Rizzo, Carolina Ubaldo Pag.11 Anatomy Prof. Laura Mangiavini 10/11/2023 The elbow is characterized by a single joint cavity; however, functionally, there are three joints involving the distal humerus and the radius, the distal humerus and the ulna, and the ulna and the radius. The distal humerus can be further divided into two condyles The lateral condyle: The medial condyle Each condyle terminates with an epicondyle, resulting in two epicondyles, the lateral and the medial. The lateral condyle extends to a structure known as the capitellum, resembling a ball, and it articulates with the head of the radius. On the medial side, within the medial condyle, the trochlea is present, which articulates with the proximal epiphysis of the ulna. The proximal epiphysis of the radius comprises a head and a neck, with the head featuring a concave surface that articulates with the capitellum. The ulna is more intricate, featuring the semilunar surface, which articulates with the trochlea. The extremities of this surface have two processes: the anterior coronoid process and the posterior olecranon process In the interior part of the humerus, there are two fossae. The lateral fossa, also known as the radial fossa, facilitates the movements of the radius during flexion. Additionally, there is the coronoid fossa, which articulates with the coronoid process during extreme flexion. There is also a posterior fossa known as the olecranon fossa, which accommodates the olecranon process of the ulna. The joint cavity is a saddle-joint cavity; therefore, we have one joint capsule surrounding the distal end of the humerus, the head of the radius, and the proximal ulna. The joint capsule is strengthened by ligaments, in particular, by the medial collateral ligament, the lateral collateral ligament, which goes from the lateral side of the humerus to the radius, and the annular ligament, which stabilizes the head of the radius to the ulna in the radioulnar joint. The medial collateral ligament (or ulnar ligament) extends from the medial epicondyle to the proximal surface of the ulna. Federica Rizzo, Carolina Ubaldo Pag.12 Anatomy Prof. Laura Mangiavini 10/11/2023 The elbow joint can be functionally divided into two parts: True elbow joint: This division includes the humeral-radius part, situated between the capitellum and the head of the radius, and the humeral-ulna part, located between the trochlea of the humerus and the semilunar surface of the ulna. It facilitates flexion and extension movements. Radio-ulnar joint: This division includes the humeral-radius part, situated between the This joint is formed between the lateral proximal part of the ulna and the head of the radius, enabling the pronation-supination movement of the forearm (axial rotation, where the radius rotates over the ulna). Federica Rizzo, Carolina Ubaldo Pag.13