| Elbow | |
|---|---|
| Latin | articulatio cubiti |
| Gray's | subject #84 321 |
| MeSH | Elbow+joint |
The human elbow is the region surrounding the elbow-joint[1]—the ginglymus or hinge joint in the middle of the arm. Three bones form the elbow joint: the humerus of the upper arm, and the paired radius and ulna of the forearm.[2]
The bony prominence at the very tip of the elbow is the olecranon process of the ulna, and the inner aspect of the elbow is called the antecubital fossa.
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The now obsolete length unit ell relates closely to the elbow. This becomes especially visible when considering the Germanic origins of both words, Elle (ell, defined as the length of a male forearm from elbow to fingertips) and Ellbogen (elbow). It is unknown when or why the second "l" was dropped from English usage of the word.
The elbow-joint comprises three different portions. All these articular surfaces are enveloped by a common synovial membrane, and the movements of the whole joint should be studied together.
| Joint | From | To | Description |
| humeroulnar joint | trochlear notch of the ulna | trochlea of humerus | Is a simple hinge-joint, and allows of movements of flexion and extension only. |
| humeroradial joint | head of the radius | capitulum of the humerus | Is a hinge-joint. |
| proximal radioulnar joint | head of the radius | radial notch of the ulna | In any position of flexion or extension, the radius, carrying the hand with it, can be rotated in it. This movement includes pronation and supination. |
The combination of the movements of flexion and extension of the forearm with those of pronation and supination of the hand, which is ensured by the two being performed at the same joint, is essential to the accuracy of the various minute movements of the hand.
The hand is only directly articulated to the distal surface of the radius, and the ulnar notch on the lower end of the radius travels around the lower end of the ulna. The ulna is excluded from the wrist-joint by the articular disk.
Thus, rotation of the head of the radius around an axis passing through the center of the radial head of the humerus imparts circular movement to the hand through a very considerable arc.
The trochlea of the humerus is received into the semilunar notch of the ulna, and the capitulum of the humerus articulates with the fovea on the head of the radius. The articular surfaces are connected together by a capsule, which is thickened medially and laterally, and, to a less extent, in front and behind. These thickened portions are usually described as distinct ligaments.
The major ligaments are the ulnar collateral ligament, radial collateral ligament, and annular ligament.
[3]
The lateral ligamentous complex originates from the lateral epicondyle. It proceeds through the virtual axis of flexion and extension. The complex is isometric during movements. Meaning that flexion and extension do not affect the lenghts of the structures. The lateral ligamentous complex mainly consists of the radial collateral ligament RCL. Compared with the medial collateral ligament MCL it is catchier to differentiate from the surrounding tissue. The LCL originates as just mentioned from the lateral epicondyle and inserts mainly into the ligamentum anulare radii in a widespread manner. The fibers are closely connected to the musculus supinator. Its superficial fibers fuse with the tendons of the hand extensor group. Although the differences concerning the tractive forces and tensions within the RCL complex during the flexion are inferior than within the medial complex, three parts can be differentiated. However, the lateral complex does not consist only of fibers which indirectly connect humerus and radius, but also of various capsule condensations which connect lateral epicondyle and olecranon. Another noticeable connection consists often between the lateral epicondyle and the posterior fibers of the ligamentum anulare radii and the crista musculi supinatoris ulnae. It is called ligamentum collaterale accessorium or ligamentum accessorium anterius. An external valgus or varus stress is irrelevant for the tonicity of the radial ligamentous complex, which can be argumentative for the abovementioned isometry at the origin of the RCL. Thus is the lateral ulnar collateral ligament LUCL at all elbow positions important for the varus stability.
Ruptures of the furthest posteriorly positioned part of the complex, namely the abovementioned LUCL, lead to various types of postero-lateral elbow instability.[4] LUCL tears appear cumulatively in patients which suffer from a tennis elbow with a contemporaneous tendon injury of the musculus extensor communis.
Thereby the radius head dislocates dorsally compared to the capitulum humeri. As contrasted with the radius head dislocation, the ligamentum anulare radii and the stability at the proximal radio-ulnar joint are not affected.[5] And thus this particular posterior rein and the complex in general gains center stage in clinical and consequently also radiological assessment.
[6]
A lesion of the LCL is less common than a lesion of the MCL. It is often combined with an epicondylitis lateralis respectively a tear of the musculus extensor carpi radialis brevis. Additionally can a fracture at the area of the epicondylus lateralis secondarily affect the ligament. The expansion of the image layer should be one third cranially and two third caudally of the elbow joint. A layer thickness of 3 or 4 mm is recommended. The layers should be angled, namely the coronal plane parallel to the line between the humeral epicondyle and the sagittal plane perpendicularly to it. The axial planes are often performed as gradient echo sequences. But these are disadvantageous if the injury is located at the collateral ligaments, because it is harder to mark out any potentially perifocal infiltrations. Therefore for a sufficient examination, a T2-weighted fat suppressed or a T1-weighted contrast agent sequence is additionally necessary. At the angulated coronal plane is the collateral ligament both medially and laterally in all ligament reins well detectable, namely at the area of the humeral epicondyle both medially the insertion of the flexor tendons and laterally the insertion of the extensor tendons. The axial plane allows a precise assessment of the biceps and brachial muscle in the front area, the triceps muscle with its insertion at the olecranon, the medial and lateral epicondyle, and the collateral ligaments and or the tendon complex. The MR arthrography which has become a standard for some specific issues concerning the shoulder or the knee, is also an alternative for examination of the elbow. It is especially advantageous for the assessment of ligament and capsule injuries.
In sum, the MRI is an important and valuable tool to assess both post-traumatically injuries of the medial and lateral collateral ligament and of the tendons of the flexor and extensor muscle group. Clinically it can be hard to distinguish between a strain and a partial tear, high resolution imaging is required. MRI is regarded as the current diagnostic gold standard.
Tears of the lateral collateral ligament LCL affect mainly the primary lateral stabilizer of the elbow joint, namely the lateral ulnar collateral ligament LUCL. They could both lead to a postero-lateral instability with postero-inferior subluxation of the radial head in relation to the capitulum and to a secondary ulno-humeral subluxation. In contrast to the radial head dislocation, which is induced by a radio-ulnar joint instability with rupture of the ligamentum anulare radii, the LUCL is not affected in the case of postero-lateral instability. LUCL tears in children are mainly caused by acute elbow dislocations and in adults by varus stress. Chronic pain symptomatic, a snapping joint and postero-lateral instability are often to find in the patients medical history. A positive Pivot-shift-test in 20 – 30° flexion is evidencing for a postero-lateral instability.[7]
Odonnel proclaimed a high sensitivity for demonstrating postero-lateral dislocation of the radial head and rotatory displacement of the semilunar notch of the ulna on fluoroscopy and plain radiography in the early nineties. It is important to mention that the group size for the examination was vanishingly small, namely only five patients. Potter et al. on the other hand was not able to reproduce the diagnostic results with help of the same radiological methods, which only showed a normal alignment, and foregrounded quite rightly the MR in order to achieve an accurate LUCL assessment.
Most LUCL tears are complete and located at the lateral epicondyle. Chronic tears lead to images depicting a thickened, discontinuous and inhomogenous ligament. Medial ulno-humeral cartilage damages, bone marrow edema at the posterior part of the capitulum and at the volar part of the radial head and tendinosis of the extensor group have been seen. Thin layers on paracoronar MR images are recommended to depict the LUCL. Proton-densed fast-spin-echo high resolution and fat-suppressed T1-weighted sequences show superiorly any lateral ligament tears.
Acute postero-lateral instabilities are treated conservatively through a rail for about 4 to 6 weeks. If the LUCL does not heal proper scarred which leads to a chronic instability, it should be reconstructed as a tendon-graft.[8]
[9]
The medial capsule ligament complex, also called ulnar complex, contains a superficial and a deep layer. Its origin and its insertion coincide with those of the medial joint capsule. The superficial layer consists of an anterior and a posterior bundle. The origins of the two bundles are not on the elbow flexion and extension axis. And due to the fact that the elbow possesses nearly a hinge axis, different elbow positions cause strain at different parts of the capsule ligament complex. The anterior bundle of the superficial layer presents itself as a strikingly strong band-like thickening, which is clearly distinct from the deeper, actual joint capsule. Due to different strain behavior during flexion, the anterior medial collateral ligament (AMCL) is divided into a medial and an anterior part. The superficial posterior bundle (PMCL) is less thick than the anterior one. It thickens the capsule with fan-shaped radiating fibers. Again, we can distinguish between three parts. The transverse band, namely the ligamentum transversum cooperi, has no stabilizing effect, but may have supported the cohesion during the bone growth between the two growth cores, the proximal ulna, the coronoid process and the olecranon. It might be possible that the ligaments function comes into effect, not until a dynamic examination of the stability. Where it probably has the function as a transmitter of the dynamization between the two other bundles through the medial muscle group. Matthijs' et al. idea of dynamization is a muscle induced alteration of the tension in an idly soft tissue structure. The deep layer does not contain any bundling, but fibres that originate conjoint with the superficial layer and insert fan-shaped at the edge of the incisura trochlearis. The structure gets tensed during valgus stress.
Injury or degeneration of the medial collateral ligament with or without a concurrent injury of the flexor tendons is typically seen at throwing athletes. The violations are mainly caused by chronic micro traumata due to repetitive valgus stress during the acceleration phase, especially at handball, baseball and tennis. These injuries of the medial collateral ligament can excellently be depicted. Prior is the exact extent measurement of the damage. The status of the functionally important anterior bundle of the collateral ligament complex can be displayed at best on axial and coronal planes. A complete rupture of the anterior bundle usually is an acute event. T2-weighted and fat suppressed images are most helpful in such cases. A partial tear of the medial collateral ligament, particularly of the anterior bundle with a still intact surface, cannot be detected even via surgical procedures unless the ligament is torn. Therefore the magnetic resonance is essential for demonstrating partial tears. This is best achieved with a direct MR arthrography. In so using the MRA, even the under the surface positioned intra ligamentar tear is detectable. The contrast agent causes a circumscribed signal increase. Ruptures of the medial collateral ligament are with 87% mostly located at the medial area. 10% occur at the distal area, and only 3% at the proximal region. A rupture of the medial collateral ligament also occurs frequently with a posterior dislocation of the elbow. A common traumatic mechanism which leads to a posterior dislocation is the fall onto the extended arm. Depending on the impact and the constellation this may lead to a rupture of both the medial and the lateral collateral ligament, as well as to a lesion of the anterior and the posterior capsule. The patient complains about pain around the medial epicondyle. Clinically it may be difficult to distinguish between a lesion of the medial collateral ligament, a lesion of the tendinous insertion or a even an impingement of the ulnar nerve. Generally, the acute injuries are more probably located at the collateral ligament, and the chronic injuries more at the area of the tendinous insertion. The MRI is capable to differentiate between various pain sources and to estimate the gravity of the injury.
In sum, the MRI is an important and valuable tool to assess both post-traumatically injuries of the medial and lateral collateral ligament and of the tendons of the flexor and extensor muscle group. Clinically it can be hard to distinguish between a strain and a partial tear, high resolution imaging is then required. MRI is regarded as the current diagnostic gold standard.
The synovial membrane is very extensive. It extends from the margin of the articular surface of the humerus, and lines the coronoid, radial and olecranon fossæ on that bone; it is reflected over the deep surface of the capsule and forms a pouch between the radial notch, the deep surface of the annular ligament, and the circumference of the head of the radius. Projecting between the radius and ulna into the cavity is a crescentic fold of synovial membrane, suggesting the division of the joint into two; one the humeroradial, the other the humeroulnar.
Between the capsule and the synovial membrane are three masses of fat:
The muscles in relation with the joint are:
Two main movements are possible at the elbow:
In the anatomical position (with the forearm supine), the radius and ulna lie parallel to each other. During pronation, the ulna remains fixed, and the radius rolls around it at both the wrist and the elbow joints. In the prone position, the radius and ulna appear crossed.
Most of the force through the elbow joint is transferred between the humerus and the ulna. Very little force is transmitted between the humerus and the radius. (By contrast, at the wrist joint, most of the force is transferred between the radius and the carpus, with the ulna taking very little part in the wrist joint).
When the arm is extended, with the palm facing forward or up, the bones of the humerus and forearm are not perfectly aligned. The deviation from a straight line occurs in the direction of the thumb, and is referred to as the “carrying angle” (visible in the right half of the picture, right).
The carrying angle permits the arm to be swung without contacting the hips. Women on average have smaller shoulders and wider hips than men, which may necessitate a more acute carrying angle (i.e., less angle than that in male when measured from outside). There is, however, extensive overlap in the carrying angle between individual men and women, and a sex-bias has not been consistently observed in scientific studies.[10][11][12]
The angle is greater in the dominant limb than the non-dominant limb of both sexes,[13][14] suggesting that natural forces acting on the elbow modify the carrying angle. Developmental,[15] ageing and possibly racial influences add further to the variability of this parameter.
The carrying angle can influence how objects are held by individuals — those with a more extreme carrying angle may be more likely to pronate the forearm when holding objects in the hand to keep the elbow closer to the body.
The lateral elbow radiograph positioned to the right is a poor example of a lateral elbow joint. although, the radius and ulna are at true lateral position at the distal radio ulnar joint the humerus is not parallel to the image receptor resulting in a closing of the joint at the trochlear olecranon articulation, thus making the image non diagnostic.
The arteries supplying the joint are derived from the anastomosis between the profunda and the superior and inferior ulnar collateral branches of the brachial, with the anterior, posterior, and interosseous recurrent branches of the ulnar, and the recurrent branch of the radial. These vessels form a complete anastomotic network around the joint.
The nerves of the joint are a twig from the ulnar, as it passes between the medial condyle and the olecranon; a filament from the musculocutaneous, and two from the median.
The types of disease most commonly seen at the elbow are due to injury.
Two of the most common injuries at the elbow are overuse injuries: tennis elbow and golfer's elbow. Golfer's elbow involves the tendon of the common flexor origin which originates at the medial epicondyle of the humerus (the "inside" of the elbow). Tennis elbow is the equivalent injury, but at the common extensor origin (the lateral epicondyle of the humerus).
There are three bones at the elbow joint, and any combination of these bones may be involved in a fracture of the elbow. Patients who are able to fully extend their arm at the elbow are unlikely to have a fracture (98% certainty) and an X-ray is not required as long as an olecranon fracture is ruled out.[16] Acute fractures may not be easily visible on X-ray.
Elbow dislocations constitute 10% to 25% of all injuries to the elbow. The elbow is one of the most commonly dislocated joints in the body, with an average annual incidence of acute dislocation of 6 per 100,000 persons.[17] Among injuries to the upper extremity, dislocation of the elbow is second only to a dislocated shoulder. A full dislocation of the elbow will require expert medical attention to re-align, and recovery can take approximately 8-14weeks. A small amount of people (10% or less) report near full recovery and very minimal permanent restriction, but most often a permanent restriction of 5-15% movement is common.
Infection of the elbow joint (septic arthritis) is uncommon. It may occur spontaneously, but may also occur in relation to surgery or infection elsewhere in the body (for example, endocarditis).
Elbow arthritis is usually seen in individuals with rheumatoid arthritis or after fractures that involve the joint itself. When the damage to the joint is severe, fascial arthroplasty or elbow joint replacement may be considered.[18]
[19]
The elbow joint is a complex joint, which consists of three individual joints: humero-radial joint, humero-ulnar joint, and radio-ulnar joint. Numerous ligaments, tendons and muscles are surrounding the joint. The main indications for imaging are acute trauma and chronic overuse injuries. Not only for these indications are CT and MRI used, but also for peripheral nerve compression syndromes and other joint diseases.
The conventional radiography is still a very useful and therefore basic diagnostic tool for the elbow joint. But “cave”: The default settings of the X-ray do not match the physiological central joint position. The standard projection in an a.p. beam requires full extension and supination of the arm. Many diseases and injuries can restrict the range of motion, so that the patient’s position could be suboptimal. Consequently could the applicability be lowered. If the joint extension range is restricted due to a traumatic event, a parallel positioning of the forearm to the board can improve the assessment of the humero-radial joint and the radius head at an a.p. projection. The lateral projection is not affected by an extension deficit because it does not require any extension of the arm. But the full supination of the forearm is still necessary. On the basis of an x-Ray it is difficult to quantify any supination deficit.
Especially in this joint, the assessment of soft tissue can point to joint effusions. For example the so-called anterior and posterior fat pad sign. A special projection targeted towards the radius head can improve the judging concerning a fracture. First and foremost common after an inconspicuous standard general view but traumatic joint effusion. Other special projections like the sulcus-ulnaris projection get more and more displaced by the cross sectional imaging.
Important diagnostic reference lines:
The CT scans gained of considerable importance in the diagnosis of articular fractures and their therapeutic control. The patient lies in a supine position and the joint should be positioned in moderate flexion over the head. If the arm would be mounted next to the body or on the abdomen, the radiation exposure is higher and the picture is more vulnerable for artifacts. The investigation should be performed on a multidetector CT with minimum thickness, supplemented by adapted sagittal and coronal reformations.
Beyond solely the fracture diagnosis, MRI is the cross-section imaging device of choice. This applies to suspected soft tissue changes as well as for chronic overuse injuries and joint blocks. The positioning of the elbow joint is more difficult compared to CT. Surface coils are obligatory required. Ideal storage is possible with elevation of the arm at the isocenter of the magnet. It can occur that a prolonged storage of the arm towards cranial triggers shoulder impingement symptoms. Depending on the available equipment and technology examination with the arm positioned alongside of the body is possible. But that occasionally involves limitations in spectral fat saturation. A storage of the elbow joint on the belly is inappropriate.
Protocol:
As a parameter, a layer of 2mm thickness and a FOV of 80-120mm is recommended. Basically, an investigation of musculo-skeletal problems in an extended matrix (320, 384, 448, 512) should be sought. The goal should be a pixel size of 0.4 mm.
It has to be added that the sagittal plane is at an eventual “postero-lateral rotary instability”, for example after dislocation, a good choice to illustrate the centering of the radius head or changes at the olecranon. An injection of contrast agent can be helpful in epicondylitis or rare overuse syndromes.
[20] Husarik et al. examined 60 non-sympomatic volunteers on a 1.5 Tesla MR system. Sequences of choice were T1-weighted spin echo, sagittal T2-weighted fast spin echo, coronar fast spin echo inversion recovery with short time of inversion, transversal intermediate weighted with fat-saturation and coronar three-dimensional fast imaging with steady state precession (FISP) with water stimulus.
The anterior ulnar collateral ligament and the radial collateral ligament were entirely visible in all of the volunteers. The posterior UCL, the lateral UCL and the ligamentum anulare AL were entirely visible on 97%, 85%, respectively, 98%. An increased signal intensity in liquid sensitive sequences has been found at the anterior UCL, posterior UCL, RCL, lateral UCL and AL on 15%, 7%, 2%, 10%, respectively, 2%. 98% showed a plica postero-lateralis but only 33% a posterior plica. 85% showed a pseudo defect of the capitulum.
They concluded that the elbow ligaments and the plica postero-lateralis are throughout visible at non-symptomatic individuals on conventional MR images. Most of the physiological ligaments are thinner than 4mm and most of the physiological plicae are thinner than 3mm.
The arthrosonography allows a dynamic study of the soft tissue and bone surfaces. The clinical use is well established , particularly in the pediatrics and rheumatology. In order to verify an intraarticular fluid accumulation the ultrasound is the method of first choice. The evaluation of cartilage is limited. Through power Doppler neovascularizations can be detected sensitively at synovitis or epicondylitis. The examination is carried out by a linear transducer with a frequency from 7.5 up to 13 MHz. The extensioned elbow joint should be depicted ventrally and dorsally, both longitudinally and transversely.
Typical indications for an ultrasonographic examination of the elbow joint: Bony destruction[21], usure, osteophytes, non-attached joint fragment, chondromatose, osteochondrosis dissecans, avascular bone-cartilage-necrosis, intraarticular volume gain: joint effusion or synovialitis, bursitis, lesion of the distal biceps tendon, dislocation of the caput radii, elbow joint instability, changes of the humeral neck retro torsion angle, gout tophus, rheumatic node, inflammative rheumatic diseases, fractures, foreign bodies, tumor.
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This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained within it may be outdated.
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