Posteriorly, the olecranon fossa receives the tip of the olecranon. The medial supracondylar column is smaller than the lateral and explains the vulnerability of the medial column to fracture with trauma and some surgical procedures. The prominent lateral supracondylar ridge serves as attachment for the brachioradialis and extensor carpi radialis longus muscles anteriorly and for the triceps posteriorly.
FIGURE The prominent medial and lateral supracondylar bony columns as well as other landmarks of the posterior aspect of the distal humerus. A fibrous band termed the ligament of Strothers may originate from this process and attach to the medial epicondyle.
FIGURE Typical supracondylar process located approximately 5 cm proximal to the medial epicondyle with its characteristic configuration. The radial head defines the proximal radius and articulates with the capitellum.
It exhibits a cylindrical shape with a depression in the midportion to accommodate the capitellum. The disc-shaped head is secured to the ulna by the annular ligament Fig.
Distal to the radial head, the bone tapers to form the radial neck, which, along with the head, is vulnerable to fracture.
The anterior surface is covered by a bicipitoradial bursa protecting the biceps tendon during full pronation Fig. However, it is the rough posterior aspect that provides the site of attachment of the biceps tendon. During full pronation the tuberosity is in a dorsal position and allows repair of a ruptured biceps tendon through a posterior approach 12 see Chapter 34 and is helpful to determine axial alignment of proximal radial fractures. FIGURE Proximal aspect of the radius demonstrating the articular margin for articulation with the olecranon, the radial neck, and tuberosity.
FIGURE A deep view of the anterior aspect of the joint revealing the submuscular bursa present about the elbow joint. The proximal ulna provides the greater sigmoid notch incisura semilunaris , which serves as the major articulation of the elbow that is responsible for its inherent stability Fig. The cortical surface of the coronoid process serves as the site of insertion of the brachialis muscle and of the oblique cord. Medially the sublime tubercle serves as insertion site of the medial ulnar collateral ligament.
The triceps tendon attaches to the posterior aspect of the olecranon process. B, Lateral view with landmarks. On the lateral aspect of the coronoid process, the lesser semilunar or radial notch articulates with the radial head and is oriented roughly perpendicular to the long axis of the bone.
Distal to this the supinator crest serves as attachment to the supinator muscle, a tuberosity occurs on this crest, which is the site of insertion of the lateral ulnar collateral ligament. The elbow joint articulation is classified as a trochoginglymoid joint. The radiohumeral and proximal radioulnar joint allows axial rotation or a pivoting trochoid type of motion.
The trochlea is the hyperboloid, pulley-like surface that articulates with the semilunar notch of the ulna covered by articular cartilage through an arc of degrees 42, 73, 77 Fig. The medial contour is larger and projects more distally than does the lateral portion of the trochlea Fig.
The two surfaces are separated by a groove that courses in a helical manner from an anterolateral to a posteromedial direction. FIGURE Axial view of the distal humerus shows the isometric trochlea as well as the anterior position of the capitellum. The trochlear capitellar groove separates the trochlea from the capitellum.
The capitellum is almost spheroidal in shape and is covered with hyaline cartilage, which is about 2 mm thick anteriorly. A groove separates the capitellum from the trochlea, and the rim of the radial head articulates with this groove throughout the arc of flexion and during pronation and supination.
In the lateral plane, the orientation of the articular surface of the distal humerus is rotated anteriorly about 30 degrees with respect to the long axis of the humerus Fig.
The center of the concentric arc formed by the trochlea and capitellum is on a line that is coplanar to the anterior distal cortex of the humerus. FIGURE Lateral view of the humerus shows the degree anterior rotation of the articular condyles with respect to the long axis of the humerus. FIGURE Axial view of the distal humerus demonstrates the 5- to 7-degree internal rotation of the articulation in reference to the line connecting the midportions of the epicondyles.
FIGURE There is approximately a 6- to 8-degree valgus tilt of the distal humeral articulation with respect to the long axis of the humerus.
Hyaline cartilage covers the depression of the radial head, which has an angular arc of about 40 degrees, 77 as well as approximately degrees of articular cartilage that articulates with the ulna, hence approximately degrees of the radial circumference is not articular and amenable to open reduction internal fixation ORIF for fracture 16 Fig.
The lesser sigmoid fossa forms an arc of approximately 60 to 80 degrees, 42, 77 leaving an excursion of about degrees for pronation and supination.
The anterolateral third of the circumference of the radial head is void of cartilage. This part of the radial head lacks subchondral bone and thus is not as strong as the part that supports the articular cartilage; this part has been demonstrated to be the portion most often fractured. FIGURE Hyaline cartilage covers approximately degrees of the outside circumference of the radial head, allowing its articulation with the proximal ulna at the radial notch of the ulna.
Redrawn from Langman, J. FIGURE The neck of the radius makes an angle of approximately 15 degrees with the long axis of the proximal radius. In most individuals, a transverse portion of non-articular cartilage divides the greater sigmoid notch into an anterior portion comprising the coronoid and the posterior olecranon Fig. Redrawn from Tillmann, B. Translated by G. Stuttgart, George Thieme, Publishers; P. Publishing Co. In the lateral plane, the sigmoid notch forms an arc of about degrees.
This explains the articular void in the midportion. The orientation of the articulation is oriented approximately 30 degrees posterior to the long axis of the bone Fig.
This matches the 30 degrees anterior angulation of the distal humerus, providing stability in full extension see Chapter 3. In the frontal plane, the shaft is angulated from about 1 to 6 degrees 43, 47, 73 lateral to the articulation Fig.
This angle contributes, in part, to the variation of the carrying angle, which is discussed in Chapter 3. This matches the degree anterior rotation of the distal humerus, as shown in Figure FIGURE There is a slight approximately 4 degrees valgus angulation of the shaft of the ulna with respect to the greater sigmoid notch. The lesser sigmoid notch consists of a depression with an arc of about 70 degrees and is situated just distal to the lateral aspect of the coronoid and articulates with the radial head.
The so-called carrying angle is the angle formed by the long axes of the humerus and the ulna with the elbow fully extended Fig. In men, the mean carrying angle is 11 to 14 degrees, and in women, it is 13 to 16 degrees. FIGURE The carrying angle is formed by the variable relationship of the orientation of the humeral articulation referable to the long axis of the humerus and the valgus angular relationship of the greater sigmoid fossa referable to the long axis of the ulna.
Redrawn from Lanz, T. ARM, Berlin, Springer, The anterior capsule inserts proximally above the coronoid and radial fossae Fig. Distally, the capsule attaches to the anterior margin of the coronoid medially as well as to the annular ligament laterally. Posteriorly, the capsule attaches just above the olecranon fossa, distally along the supracondylar bony columns.
Distally, attachment is along the medial and lateral articular margin of the sigmoid notch. The greatest capacity of the elbow occurs at about 80 degrees of flexion 40, 70 and is 25 to 30 mL. FIGURE Distribution of the synovial membrane from the posterior aspect, demonstrating the presence of the synovial recess under the annular ligament and about the proximal ulna.
Redrawn from Beethman, W. The anterior capsule is normally a thin transparent structure but significant strength is provided by transverse and obliquely directed fibrous bands 23, 56 Fig.
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Folia Morphol. Pubmed citation Gilroy AM. Anatomy : an essential textbook. Read it at Google Books - Find it at Amazon. Related articles: Anatomy: Upper limb. Promoted articles advertising. Figure 1 Figure 1. Figure 2 Figure 2. Figure 4: elbow joint capsule Gray's illustration Figure 4: elbow joint capsule Gray's illustration. Figure 5: elbow joint capsule Gray's illustration Figure 5: elbow joint capsule Gray's illustration.
Figure 6: medial elbow ligaments Gray's illustration Figure 6: medial elbow ligaments Gray's illustration.
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