Elbow and Forearm Anatomy PDF

Upper Extremities Functional B Lecturer: Beáta Seregély assistant lecturer; [email protected] Semmelweis University Faculty of Health Sciences Department of Physiotherapy The funtion The joints and muscles of the elbow complex are designed to serve the hand. They provide mobility...

Upper Extremities Functional B Lecturer: Beáta Seregély assistant lecturer; [email protected] Semmelweis University Faculty of Health Sciences Department of Physiotherapy The funtion The joints and muscles of the elbow complex are designed to serve the hand. They provide mobility for the hand in space by apparent shortening and lengthening of the upper extremity. This function allows the hand to be brought close to the face for eating and grooming or to be placed at a distance from the body equal to the length of the entire upper extremity. Rotation at the elbow complex provides additional mobility for the hand. In conjunction with providing mobility for the hand, the elbow complex structures also provide stability for skilled or forceful movements of the hand when performing activities with tools or implements. Many of the 15 muscles that cross the elbow complex1 also act at either the wrist or shoulder, and therefore the wrist and shoulder are linked with the elbow in enhancing function of the hand. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 15. The elbow and the forearm complex - structure It consists of 3 bones and 4 joints. The elbow complex itself includes 3 joints in one joint capsule (trochoginglimus joint): humeroulnar, the main joint of the elbow motion humeroradial joints and the proximal radioulnar joint. And the 4th is the distal radioulnar joint. The elbow joint is a compound joint that functions as a modified or loose hinge (ginglimus) joint. 1 degree of freedom is possible at the elbow, permitting the motions of flexion and extension. The proximal and distal radioulnar joints function as 1 joint. The 2 joints acting together in rotation of the forearm and have 1 degree of freedom. The radioulnar joints are diarthrodial uniaxial pivot joints (trochoid) and permit rotation (supination and pronation), around a longitudinal axis. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 15. The distal humerus anterior aspect The shaft of the humerus ends medially as the trochlea (thread like) and the medial epicondyle, and laterally as the capitulum (anterior half of a sphere) and lateral epicondyle. The medial lip is prominent and projects farther distally than the lateral lip (4-8°) parallel to the axis of flex-ext. Midway between the medial and lateral lips is the trochlear groove, anteriorly it runs vertically. Muscles origin from the anterior aspect (there is no muscles insert on it): on the shaft: brachialis, brachioradialis, extensor carpi radialis longus on the medial epicondyle: the pronator teres, the forearm flexors (flexor carpi radialis, palmaris longus, superficial flexor digitorum and flexor carpi ulnaris, on the lateral epicondyle: the supinator, the wrist extensors (ECRB, EDC, EDM, ECU), the anconeus. SU-FoHS Department of Physiotherapy Beáta Beáta Seregély assistant Seregély 2024.lecturer 09.01. 2024. 08. 15. The distal humerus posterior aspect On the posterior aspect of the humerus, just proximal to the trochlea, is the deep and broad olecranon fossa. Only a thin sheet membrane separates the olecranon fossa from the anterior coronoid fossa. The trochlear groove, when one looks from posterior to anterior, spirals slightly toward the medial direction upwardly. Muscles origin from the posterior aspect (there is no muscles insert on it): on the shaft: triceps brachii medial and lateral head, on the medial epicondyle: the pronator teres, the forearm flexors (flexor carpi radialis, palmaris longus, superficial flexor digitorum and flexor carpi ulnaris, on the lateral epicondyle: anconeus, the wrist extensors (extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, extensor carpi ulnaris), the supinator. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 15. The forearm anterior aspect The ulna has a thick proximal end the concave trochlear notch of the ulna is the large jawlike process located between the anterior tips of the olecranon and coronoid processes. The coronoid process projects sharply from the anterior proximal ulna. The radial notch of the ulna is an articular depression just lateral to the inferior aspect of the trochlear notch. In the fully supinated position, the radius lies parallel and lateral to the ulna. The radial head is a disclike structure. Articular cartilage covers about 280 degrees of the rim. The rim of the radial head contacts the radial notch of the ulna, forming the proximal radioulnar joint. The superior surface of the radial head consists of a shallow, cup-shaped, concave depression, the fovea. SU-FoHS Department of Physiotherapy Beáta Beáta Seregély assistant Seregély 2024.lecturer 09.01. 2024. 08. 15. The forearm anterior aspect Muscles origin from the anterior aspect: the flexor digitorum superficialis, the pronator teres, the flexor digitorum profundus, (also from the the flexor pollicis longus, interosseous membrane) the pronator quadratus Muscles insert on the anterior aspect: the brachialis (on tuberosity of the ulna), the biceps brachii (on radial tuberosity), the supinator (on proximal shaft of the radius), pronator teres (on midshaft of the radius), pronator quadratus (on distal shaft of the radius), brachioradialis (on distal shaft of the radius). SU-FoHS Department of Physiotherapy Beáta Beáta Seregély assistant Seregély 2024.lecturer 09.01. 2024. 08. 15. The forearm posterior aspect The olecranon process forms the large, blunt, proximal tip of the ulna, making up the “point” of the elbow. Muscles origin from the posterior aspect: the flexor digitorum superficialis, the flexor digitorum profundus, the supinator (on proximal ulna), from the aponeurosis: extensor carpi ulnaris, flexor carpi ulnaris, flexor digitorum profundus, the abductor pollicis longus the extensor pollicis longus (also from the the extensor pollicis brevis interosseous membrane) the extensor indicis SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 15. The forearm posterior aspect Muscles insert on the anterior aspect: the triceps brachii (on olecranon process), the anconeus (on proximal ulna), the supinator (on proximal shaft of the radius), pronator teres (on midshaft of the radius). SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 15. The structure and a range of motion The reference position, used for measuring the RoM, is delined as the position when the axes of the arm and of the forearm are collinear. Flexion is the movement anteriody (the anterior surface of the forearm moves towards the anterior surface of the arm). Active flexion has a range of 140-145°. Passive flexion has a range of 160° when the examiner pushes the wrist towards the shoulder. Extension is the movement of the forearm posteriorly. Since the reference position is the full extension, the range of extension of the elbow is 0° by definition, except in people, in whom the laxity of the ligaments allows hyperextension of 5-10°. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 15. The structure and anatomical landmarks 3 visible and palpable markings are these the olecranon, a prominent midline projection (the 'bump‘ of the elbow) the medial epicondyle, the lateral epicondyle. In extension these 3 landmarks lie in a horizontal plane. Between the olecranon and the medial epicondyle lies the groove that contains the ulnar nerve. In flexion these 3 landmarks now form an equilateral triangle lying in the coronal plane tangential to the posterior aspect of the arm. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 15. The joint capsule and the ligaments The capsule is large, loose, and weak anteriorly and posteriorly, and it contains folds that are able to unfold to allow for a full RoM and blends with the proximal border of the annular ligament except posteriorly. Anteriorly reinforced by oblique and vertical bands of fibrous tissue, and posteriorly by the posterior ligament, which run transversely across the humerus and obliquely from humerus to olecranon. Laterally and medially, the capsule is reinforced by the collateral ligaments to provide an important source of multiplanar stability to the elbow, most notably however within the frontal plane. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 15. The joint capsule and the ligaments The fan-shaped medial collateral ligament arises from medial epicondyle consists of 3 sets of fibers: (only by Kapandji, the anterior (1), with its most anterior fibers strengthening the annular ligament (2)) by other authors: the anterior (intermediate set (3) by Kapandji), being the strongest, the posterior set, the ligament of Bardinet (4), reinforced by the transverse flbres of Cooper's ligament (5). SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 15. The joint capsule and the ligaments The lateral collateral ligament is more variable and also consists 2 (3) sets of fibers arising from the lateral epicondyle (13): the anterior or radial set (10) strengthens the annular ligament anteriorly, the thicker intermediate or lateral (ulnar) set (11) strengthens the annular ligament posteriorly, the posterior set (12) (only by Kapandji). SU-FoHS Department of Physiotherapy Beáta Beáta Seregély assistant Seregély 2024.lecturer 09.01. 2024. 08. 15. Normal “Valgus Angle” of the Elbow The elbow’s axis of rotation (blue line) extends slightly obliquely in a mediallateral direction through the capitulum and the trochlea. Normal cubitus valgus (A) – “carrying angle” with extended elbow is an angle of about 15° from the longitudinal axis of the humerus. Excessive cubitus valgus (B) deformity is shown with the forearm deviated laterally 30°. Cubitus varus (C) or gun-stock deformity is when the forearm deviated medially 5° or more. During flexion the anterior part of the trochlear groove which lies in the vertical plane is responsible for the direction of the forearm so the forearm comes to rest exactly in front of the arm. SU-FoHS Department of Physiotherapy Beáta Beáta Seregély assistant Seregély 2024.lecturer 09.01. 2024. 08. 15. Structures provide stability – the elbow In extension the healthy humero-ulnar joint is stabilized primarily by articular congruency and also by the increased tension in the stretched connective tissues: the impact of the olecranon process in the olecranon fossa, the tension developed in the anterior ligaments of the joint, the resistance offered by the flexor muscles (biceps, brachialis and supinator). If extension proceeds further rupture of one of these limiting structures must occur: the olecranon is fractured and the capsule is torn, the olecranon is not fractured but the capsule and the ligaments are torn, with posterior dislocation of the elbow. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 15. Structures provide stability – the elbow It is depends on whether flexion is active or passive. If flexion is active: The first limiting factors are the anterior muscles of the arm and the forearm, which contract. The other factors, impact of the corresponding bony surfaces and tension developed in the capsular ligament, are insignificant. In passive flexion the muscles relaxed and other limiting factors have role: impact of the radial head against the radial fossa and of the coronoid process against the coronoid fossa, tension in the posterior part of the capsule, tension developed passively in the triceps. flexion can then reach 160°. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 23. Structure is the base of mobility – the elbow The humero-ulnar joint: The distal humerus resembles the fork of a bicycle, with the axis of the articular surfaces running through. Its middle portion contains 2 fossae: anteriorly, the coronoid fossa, receives the coronoid process of the ulna during flexion, posteriorly, the olecranon fossa, receives the olecranon during extension. They play a vital role in increasing the range of flexion and extension by delaying the impact of the coronoid and olecranon processes on the shaft of the humerus. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 23. Structure is the base of mobility – the elbow The humeral end angulate anteriorly at 45° with the shaft, so the trochlea lies entirely in front of the axis of the shaft. The articular surface of the ulna is rotated 45° posteriorly to its long axis. This matches the anterior angulation of the distal humerus, which helps provide stability to the elbow joint in full extension but promotes flexion only partially because of the obstruction by the coronoid process. It is the coronoid fossa that allows flexion to be completed. The 2 bones are almost parallel but are separated by a space that lodges the muscles. In the absence of these two mechanical factors it is obvious that: flexion would be limited to 90° by the obstructing coronoid process, during flexion there would be no space left to accommodate the muscles even if a sizeable hole in the distal end of the humerus allowed the 2 bones to come into direct contact. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 23. Structure is the base of mobility – the elbow The humero-radial joint: The shape of the radial head is entirely determined by its function: the axial rotation in pronation-supination regardless of the degree of flexion or extension of the elbow, and flexion-extension around the intercondylar axis: the radial head correspond to the spheroidal capitulum humeri. Hence its upper surface is concave and cup-shaped. the capitulum has a medial border in the shape of a truncated cone, the condylo-trochlear groove, so a wedge needs to be removed from the medial aspect of the radial head. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 23. Structure is the base of mobility – the elbow the radial head need to not only glides on the capitulum and the capitulo-trochlear groove while turning on its axis, but it also simultaneously around its vertical axis during pronation-supination. Thus the smooth crescent cut along the edge of the radial head extends for some distance along its circumference, as if a shaving had been removed by a razor during rotation of the head. In full extension only the anterior half of the articular surface of the radial head is in contact with the capitulum because the articular cartilage of the capitulum stretches as far as the inferior end of the humerus without extending posteriorly. In full flexion the rim of the radial head reaches beyond the capitulum and enters the radial fossa. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 23. Flexion Arthrokinematics during flexion and extention: at the humero-ulnar joint, the concave surface of the trochlear notch rolls and slides on the convex trochlea in the same direction. at the humero-radial joint the concave fovea of the radius rolling and sliding across the convexity of the capitulum also in the same direction. Muscles that attach distally on the ulna flex or extend the elbow but no ability to pronate or supinate the forearm. In contrast, muscles that attach distally on the radius may, in theory, flex or extend the elbow, but also have a potential to pronate or supinate the forearm. Muscles acting primarily on the wrist also cross the elbow joint, so many of the wrist muscles have a potential to flex or extend the elbow. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 16. Flexor muscles The primary elbow flexors most effective at the midrange (80-90°): brachialis – sole function is to flex the elbow. It has the largest cross-sectional area of any muscle crossing the elbow to generate the greatest force so it is the “workhouse” of the flexors, biceps brachii - produces its maximal activity when performing flexion and supination simultaneously, two primary actions of the muscle and low levels of activity when flexion is performed with the forearm held in pronation, brachioradialis – regardless of the position of the forearm its contraction causes full flexion and rotates the forearm towards the neutral, thumb-up position. From a pronated position it supinates and from a supinated position pronates. The secondary assisting synergists are pronator teres and ECRL. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 16. Extensor muscles The primary elbow extensors are the triceps brachii works as a first class lever and between 20°-30° the efficiency is maximal because the tangential component (T) coincides with the muscular pull. It stabilizes the flexed elbow through isometric contraction or eccentric activation. A strong isometric coactivation of the elbow flexor and extensor muscles in a position near 90° produces a very stable posture at the elbow. anconeus ideal for producing “background” joint stability. The anconeus likely provides useful, low level forces that sustain extension-based posturing across the elbow, as well as forces that stabilize the ulna during active pronation and supination. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 16. Functional considerations Optimal stretch of the muscles results more powerful contraction. The biceps and the triceps are polyarticular muscles produce force across multiple joints because their long heads also pass through the shoulder joint. Combining active elbow flexion from extension with shoulder extension is an effective way for producing biceps-generated elbow flexor torque. For the same reason the triceps is more powerful when the elbow and the shoulder is flexed, since its fibers are already pretensioned. That is the base of the push-pull movements. In an open kinematic chain, in the standing position with the arm unloaded, the extension of the elbow is performed by the gravity force, but when weight is held, the biceps control the extension by isotonic eccentric action. In a closed kinematic chain the triceps is eccentrically to control elbow flexion as the body is lowered to the ground in a push-up and concentrically to extend the elbow. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 16. Functional considerations A clinical examples for useful reverse concentric isotonic contraction: A person has complete paralysis of the trunk and lower extremity but near-normal strength of the shoulder, elbow flexor, and wrist extensor muscles. With the distal aspect of the upper limb well fixed, the elbow flexor muscles can generate sufficient force to moving up to a sitting position from supine. A person with C6 tetraplegia assumed to have total paralysis of the triceps can use the innervated clavicular portion of the pectoralis major and anterior deltoid (red arrow) to pull the humerus toward the midline. With the wrist and hand fixed to the bed, the muscles rotate the elbow into extension. Once locked into extension, the stable elbow allows the entire limb to accept weight without buckling at its middle link. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 18. Summarizing of the flexion-extension Flexors brachialis: a one-joint muscle, it is not affected by the position of the shoulder, works in flexion of the elbow in all positions of the forearm, with and without resistance, it also is active in all types of contractions (isometric, concentric, and eccentric (strait or reverse), during slow and fast motions. biceps brachii: a two-joint muscle, the functioning is affected by the position of the shoulder. In full flexion of the elbow and the shoulder, with forearm supination, the muscle’s ability to generate torque is diminished. mobility muscle because of its insertion close to the elbow joint axis. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 22. Summarizing of the flexion-extension its MA is largest between 80 and 100° of elbow flexion so it is producing its greatest torque in this range, its MA is small when the elbow is in full extension, and most of the force is translator, toward joint compression. So, the biceps is less effective in the beginning of the RoM as an elbow flexor rather then stabilizator, when the elbow is flexed beyond 100°, the translatory component of the muscle force is directed away from the elbow joint and distracting it, it is active during unresisted elbow flexion with the forearm supinated and when the forearm is midway between supination and pronation in both concentric and eccentric contractions, but it tends not to be active when the forearm is pronated, when the magnitude of the resistance increases beyond limb weight, the biceps is active in all positions of the forearm, it is active during rapid extension. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 22. Summarizing of the flexion-extension brachioradilis: it is inserted at a distance from the joint axis, so the largest component of muscle force goes toward compression of the joint surfaces and stability, the peak MA for the brachioradialis occurs between 100 and 120 of elbow flexion, it is unaffected by the position of the shoulder, elbow joint angle had no effect on concentric, isometric, or isokinetic contractions, it shows no activity during eccentric flexor activity when the motion is slow with the forearm supinated, it shows no activity during slow, unresisted, concentric elbow flexion, SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 23. Summarizing of the flexion-extension when the speed is increased, it shows moderate activity if a load is applied and the forearm is either in a position midway between supination and pronation or in full pronation. it shows high levels of activity during rapid alternating supination/pronation motions. pronator teres, as well as the palmaris longus, flexor digitorum superficialis, flexor carpi radialis, and flexor carpi ulnaris, is a weak elbow flexor with primary actions at the radioulnar and wrist joints. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 23. Summarizing of the flexion-extension Extensors triceps brachii as a whole is affected by changes in the position of the elbow but not the forearm, activity of the long head of the triceps is affected by changing shoulder joint. Its ability to produce torque diminish (insufficient) when elbow is in full extension with the shoulder in hyperextension. Its medial and lateral heads, being one-joint muscles, are not affected by the position of the shoulder. the medial head is active in unresisted elbow extension, all 3 heads are active when heavy resistance is given to extension or when quick extension of the elbow is attempted in the gravity-assisted position, maximum isometric torque generation is at a position of 90 of elbow flexion, but varies with the position of the shoulder and the body, SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 23. Summarizing of the flexion-extension it is active eccentrically to control elbow flexion as the body is lowered to the ground and concentrically to extend the elbow in a closed kinematic chain, such as in a push-up. it is active as a stabilizing synergist for example to prevent flexion of the elbow when the biceps is acting as a supinator. the anconeus, assists in elbow extension and a stabilizer during supination and pronation. Some flexor or extensor muscle pairs, such as the brachialis and brachioradialis, and the anconeus and medial head of the triceps brachii are coactivated in a similar manner for all stresses. But the synergistic patterns of other muscles are complex and vary with the joint angle, direction of the stress, and the type of muscle contraction (isometric, concentric, eccentric). For example, the brachialis and the long head of the biceps work synergistically during isometric contractions only 0-45 of flexion. The CNS may selectively recruits uniarticular rather than two-joint muscles to complete a task. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 23. Forearm – the movement pronation-supination around the long axis that extends from near the radial head through the ulnar head, involves 2 mechanically linked joints: superior radio-ulnar joint, anatomically belongs to the elbow joint, inferior radio-ulnar joint, anatomically separate from the wrist joint. Pronation-supination measured when the elbow is flexed at 90° and resting against the body in reference or neutral position with the thumb points up, the palm faces medially. in supination the palm faces up in the horizontal plane, the RoM is 90°. in pronation the palm faces down, the RoM is 70-80°. with the extended elbow, the shoulder rotation is included and the total RoM: 360°, when the upper limb hangs down vertically alongside the body, 270°, when the upper limb is abductedor flexed to 90°, 180°, when the arm is abducted at 180°, because shoulder axial rotation is 0° SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 23. Forearm – the structure – the interosseous membrane In supination the ulna and the radius are parallel position and bound together by the interosseous membrane – taut in supination. Most of the fibers are referred to as the central or anterior band, directed distal-medially from the radius, connecting to with the ulna at about 20°. In addition 2 subsets are noteworthy, both flowing generally perpendicular to the main central band. At the distal aspect of the forearm are a set of distal oblique or posterior fibers, generally directed distal-laterally from the ulna, to the radius and add to the stability of the distal radio-ulnar joint. At the proximal forearm is an oblique cord, which runs from the lateral side of the tuberosity of the ulna to just distal to the radial tuberosity, help limit distal migration of the radius relative to the ulna. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 23. Forearm – the structure – the interosseous membrane The primary functions of the central band are to: firmly bind the radius to the ulna, serve as an attachment site for extrinsic muscles of the hand, provide a mechanism for transmitting force proximally through the upper limb. Because of the fiber direction of the central band, part of the proximal directed force through the radius is transferred across the membrane to the ulna. In this way, both the humero- ulnar and the humero-radial joints more equally “share” the compression forces. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 23. Forearm – the structure – the interosseous membrane fiber direction of the central band is not aligned to resist distally applied forces on the radius. Holding a heavy suitcase with the elbow extended causes a distracting force. This pull on the radius slackens the central band, consequently placing larger demands on other tissues, such as the oblique cord and the annular ligament, to accept the load. Contraction of the brachioradialis or other muscles involved with grasp can assist with holding the radius and load firmly against the capitulum of the humerus. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 23. Forearm – the structure – the radio-ulnar joints During pronation the distal segment of the forearm complex (the radius and hand) rotates and crosses over the ulna, which remains nearly stationary during an isolated pronation and supination movement. A stable humero-ulnar joint provides an essential rigid link on which the radius, wrist, and hand can pivot. The proximal joint can be compared mechanically to a system of ball-bearings reinforced by 2 ligaments: the anular ligament which internal circumference is lined with cartilage and the external surface reinforced by the capsule, the radial and ulnar collateral ligament, and the supinator muscle, and the quadrate ligament. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 24. Forearm – the structure – the radio-ulnar joints During pronation the distal segment of the forearm complex (the radius and hand) rotates and crosses over the ulna, which remains nearly stationary during an isolated pronation and supination movement. A stable humero-ulnar joint provides an essential rigid link on which the radius, wrist, and hand can pivot. The proximal joint can be compared mechanically to a system of ball-bearings reinforced by 2 ligaments: the anular ligament which internal circumference is lined with cartilage and the external surface reinforced by the capsule, the radial and ulnar collateral ligament, and the supinator muscle, and the quadrate ligament. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 24. Forearm – the structure – the radio-ulnar joints The inner compartment of the ball-bearing system the radial head – the circumference radii is the convex part of the joint, the outer compartment of the ball-bearing system: the radial notch of the ulna is coated by cartilage, concave antero-posteriorly, the annular ligament is made up of a strong fibrous band attached by its ends to the anterior and posterior margins of the radial notch of the ulna and is lined internally by cartilage continuous with that lining the radial notch. It serves as a ligament by surrounding the radial head and pressing it against the radial notch of the ulna, and as an articular surface in contact with the radial head allow the spin. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 24. Forearm – the structure – the radio-ulnar joints The quadrate ligament is thin and fibrous, arising just below the radial notch of the ulna and attaching distally to the medial surface of the neck of the radius. The ligament stabilizes the proximal radio-ulnar joint, and is stretched throughout movement, most notably supination. Cut of the annular ligament with intact quadrate ligament cause the radial head dislocated to laterally and inferiorly into quasi pronation. The distal radio-ulnar joint consists of the convex head of the ulna and the shallow concavity of the ulnar notch on the radius and the proximal surface of an articular disc. The stability of this joint is furnished through a set of connective tissues associated with the disc, plus activation of muscles. The disc acting as a 'suspended meniscus‘ and reduce a variety of stresses: traction, compression and shearing forces. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 24. Forearm – the structure – the TFCC The articular disc is part of a larger set of connective tissue known as the triangular fibrocartilage complex (TFCC). It occupies most of the “ulnocarpal space” between the head of the ulna and the ulnar side of the wrist. It binds together the radius and the ulna, help the stability of the joint, provides a dual articular surface proximally for the ulnar head and distally for the carpal bones, and cause that the ulnar head is not in directly contact with the carpal bones. The stability is helped by the anterior (taut in supination) and posterior (taut in pronation) ligaments of the joint and also by other structures. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 24. Forearm – the mobility It is important that the two bones of the forearm in the position of supination are concave anteriorly. The importance of this arrangement lies in the fact that during pronation the radius crosses over the ulna , and thus its distal head can extend farther posteriorly with respect to the ulna because the concavities of the two bones face each other. The proximal radio-ulnar joint: The main movement is rotation (spin) of the radial head about its axis within the fibro-osseous ring, formed by the annular ligament and the radial notch of the ulna. This movement is limited by the tension of the quadrate ligament in supination and pronation. The radial head is slightly oval. This explains why the annular cuff of the radial head cannot be bony and rigid. The annular ligament, which makes up 3/4 of the cuff, is flexible and allows some distortion, while holding the radial head in perfect fit. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 25. Forearm – the mobility There are four accessory movements: The cup-shaped surface of the radial head spins with respect to the capitulum humeri, The beveled ridge of the radial head glides in contact with the capitulo-trochlear groove of the humerus. During pronation, the radial head comes to lie transversely with a lateral shift and it allows the radius to move out of the way of the ulna just in time for the radial tuberosity between the radius and the ulna. the axis of the radius becomes oblique inferiorly and medially so that the plane of the proximal surface of the radial head is tilted distally and laterally during pronation. the axis of the forearm, which was slightly oblique laterally because of the cubitus valgus, becomes collinear with the axis of the arm and the hand. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 25. Forearm – the mobility The distal radio-ulnar joint: Let us assume at first that the ulna remains stationary and only the radius moves. In this case the axis of pronation-supination extends into the hand along the medial edge of the ulna and the fifth finger. This is the case when the forearm is rotated while maintaining contact with the table it is resting on. The radius glide and roll on the ulna. In the usual movement of pronation-supination, centered on the dynamic tripod of prehension, the axis is intermediate in location and passes through the lower end of the radius near the ulnar notch, which collinear the axis of the hand (the 3rd finger). In this case not only the position of the radius, but the ulna is changing. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 25. Forearm – the mobility The radius rotates on itself for nearly 180°, and the ulna is displaced along an arc of a circle with the same center, a displacement made up of a component of extension of the humero-ulnar joint and an accessory lateral movement. Theoretically when the elbow is fully extended, the ulna is held fixed by the olecranon fitting snugly into its fossa and the elbow is tightly immobilized and no pronation occur. This loss of pronation is offset by medial rotation of the humerus. During everyday movements, forearm supination is associated with shoulder joint (humerus) lateral rotation, while pronation is associated with medial rotation. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 25. Arthrokinematics of supination-pronation The movement of the radius as a whole is well demonstrated by comparing the radius to a crank (depicted in the former slide). SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 25. Forearm – muscle of the supination The primary supinator muscles are the supinator which active regardless of the elbow angle or the speed or power of the action, the nervous system recruits it for low-power tasks that require a supination motion only like unresisted slow supination in all positions of the elbow or forearm or unresisted fast supination when the elbow is extended. biceps brachii a powerful supinator muscle, its effectiveness as a supinator is greatest when the elbow is flexed 90°, active against resistance and during fast supination, max. supination torque occur from the forearm in the pronated position. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 25. Forearm – muscle of the supination Secondary muscles with a more limited potential are the radial wrist extensors (ECRL, ECRB, EDM from pronated position), attach near the lateral epicondyle of the humerus the extensor pollicis longus (and brevis), the abductor pollicis longus, the extensor indicis (from pronated position) and general consensus is that the brachioradialis is a secondary supinator (from pronated position) and a secondary pronator (from supinated position). Stabilizing synergist the anconeus and the extensor carpi ulnaris (ECU) muscle both supination and pronation. The supinators get innervation from 2 nerve (musculocutaneus and radial) are stronger than the pronators which get innervation from the median nerve. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 26. The function At a 90° elbow angle, the tendon of the biceps approaches a 90° angle-of-insertion into the radius. This biomechanical situation allows essentially the entire magnitude of a maximal-effort biceps force to intersect nearly perpendicular to the axis of rotation of the forearm. When the elbow is flexed to only 30°, for example, the tendon of the biceps loses its right-angle intersection with the axis of rotation. In high-power supination the biceps is recruited by the nervous system to assist the smaller supinator muscles. As described, this requires that the elbow be held flexed ~90°. Maintaining this position requires that the triceps co-contract synchronously with the biceps. By attaching to the ulna, the triceps is able to neutralize the elbow flexion tendency of the biceps without interfering with the supination task. This muscular cooperation is an example of how 2 muscles can function as synergists while at the same time remaining antagonists. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 26. Forearm – muscle of the pronation The primary muscles for pronation are the pronator teres produce the greatest EMG activity during higher-power pronation actions, beside pronation it also stabilize the radial-ulnar joint, stabilize the humero-radial joint with its translation component, also an elbow flexor, its neutralizing synergist the triceps. the pronator quadratus the most active and consistently used pronator muscle, involved during all pronation movements, regardless of the power, speed or the amount of elbow flexion. a stabilizer of the distal radio-ulnar joint throughout the range of pronation. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 26. Forearm – muscle of the pronation The secondary pronators are the flexor carpi radialis and the palmaris longus, both attaching to the medial epicondyle of the humerus, the brachioradialis (from supinated position) Stabilizing synergist the extensor carpi radialis longus (ECRL) and brevis (ECRB) muscle both supination and pronation. The Law of Parsimony At the forearm, low-power supination and pronation activities are controlled by the small supinator or the pronator quadratus; high-power actions require assistance from the biceps and pronator teres. When the polyarticular muscles are recruited, additional muscles are needed to stabilize their undesired actions. Increasing the power of any action at the elbow and forearm creates a sharp disproportionate rise in overall muscle activity the polyarticular “reserve” muscles and the other neutralizer muscles. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 26. Pronation-supination in closed kinematic chain Pronation and supination are next described when the upper limb is in a weight-bearing position. In this case the humerus and ulna rotate relative to a stationary, or fixed, radius and hand. The glenohumeral joint is held partially internally rotated. The ulna and radius are parallel in full supination. The radius and hand held firmly fixed with the ground, pronation of the forearm occurs by an external rotation of the humerus and ulna. Moving back to the fully supinated position involves internal rotation of the humerus and ulna. A muscle “force-couple” used to pronate the forearm in the weight-bearing position. The infraspinatus rotates the humerus relative to a fixed scapula, whereas the pronator quadratus rotates the ulna relative to a fixed radius. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 26. The function Most of the activities of daily living require a combination of motion at both the elbow and radioulnar joints. A total arc of ˇ~100° of elbow flexion (between 30° and 130°) and ~100° of forearm rotation (~50° supination and ~50° pronation) is sufficient to accomplish simple tasks. For example, about 110° flexion, 23° of pronation and 59° of supination are necessary to eat with spoon. Mobility of the complex is necessary for normal functioning. Compensations of the limited RoM of the elbow complex happen at the shoulder. The mobility afforded the hand by pronation and supination of the forearm is achieved at the expense of stability because the movable forearm is unable to provide a stable base for attachment of the wrist and hand muscles. So, many of the muscles that act on the wrist and hand are attached on the distal end of the humerus. The fact that the wrist and most the extrinsic hand muscles cross the elbow create close structural and functional relationships between the elbow and wrist/hand complexes. Anatomically, the hand and wrist muscles help reinforce the elbow joint capsule and contribute to stability of the elbow. SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 26. Muscles innervation and dermatomes Musculocutaneus nerve (C5-7) Coracobrachialis muscle Biceps brachii Braclialis muscle Axillary nerve (C5-6) Deltoid muscle Teres minor muscle SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 25. Muscles innervation and dermatomes Radial nerve (C5-T1) Triceps brachii muscle Extensor Brachioradialis muscle pollicis brevis Extensor carpi radialis longus muscle Anconeus muscle Extensor pollicis longus Extensor carpi radialis brevis muscle Extensor digitorum Extensor (communis) indicis muscle Extensor digiti minimi muscle Extensor carpi ulnaris muscle Supinator muscle Abductor pollicis longus SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 25. Muscles innervation and dermatomes Median nerve (C6-T1) Pronator teres muscle Flexor Flexor carpi radialis muscle pollicis Palmaris longus muscle brevis muscle Flexor digitorum profundus (lateral half) Lumbricals (lateral half) Flexor digitorum superficialis Flexor pollicis longus muscle Pronator quadratus muscle Abductor pollicis brevis m. Opponens pollicis muscle SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 25. Muscles innervation and dermatomes Ulnar nerve (C8-T1) Flexor carpi ulnaris muscle Flexor digitorum profundus (medial half) Palmaris brevis muscle Abductor digiti minimi m. Flexor digiti minimi muscle Opponens digiti minimi m. Adductor pollicis muscle Dorsal interossei (4) Palmar interossei (4 (3)) Lumbricals (medial half) SU-FoHS Department of Physiotherapy Beáta Seregély assistant lecturer 2024. 08. 25.