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CLINICAL EXAMINATION OF THE ELBOW
ANATOMY AND PATHOPHYSIOLOGY
The joint capsule
Pronation and supination
Posterior interosseous nerve
Anterior interosseous nerve
Global muscle evaluation
Functional investigation of the elbow
Functional investigation of the upper limb
Global functional investigation: the lower limbs - walking aids
Institut de la Main, 6 square Jouvenet, F-75016 Paris
The elbow complex is made up of three separate articulations, the humero-ulnar joint, the humeroradial (radiocapitellar) joint, and the superior radio-ulnar joint. These joints are covered by the same capsule. The elbow allows flexion and extension, as well as pronation and supination, and thus enables the hand to be placed in a variety of positions in space. Elbow flexion brings the hand to the chest, the mouth, or the face, thereby allowing the performance of most of the activities associated with feeding, dressing, and body care; elbow extension, on the other hand, takes the hand away from the body, and enables it to grasp objects.
Elbow injuries are rare; however, they may be difficult to diagnose. This problem may be resolved to some extent or simplified by a full and systematic clinical examination. The joint is superficial, and hence readily accessible to clinical examination. As with other structures in the body, the examiner must be thoroughly familiar with the anatomy of the joint and with the abnormal conditions that may be encountered.
This article deals with the broad principles of clinical examination, and will highlight only some of the disorders of the elbow.
ANATOMY AND PATHOPHYSIOLOGY
The anatomy of the elbow joint and the surrounding structures has been the subject of much research. In this article, only the main points that have emerged from recent studies will be summarized.
The trochlea is shaped like a pulley; its medial lip is more prominent than the lateral one. The groove of the pulley runs obliquely downwards and outwards; it courses in a helical manner, forming an arch of about 330°. The distal joint surface of the humerus is in about 30° anterior rotation with respect to the long axis of the humerus, in the sagittal plane; the condyles have 3-8° of internal rotation with respect to a line joining the epicondyles, in the axial plane; while, in the frontal plane there is a 6-8° valgus tilt of the condyles with respect to the long axis of the humerus(32, 34, 42). Elbow rotation is virtually around a single centre, which coincides with the condylotrochlear axis(48). On a true lateral radiograph of the elbow, the flexion-extension axis is at the centre of three concentric circles formed, respectively, by the projection of the edges of the condyles, the ulnar groove at the back of the medial epicondyle, and the medial lip of the trochlea (Fig. 4b). This flexion-extension axis is on a vertical line drawn down from the anterior cortex of the humeral shaft. It is an essential landmark for the implantation of a total elbow joint replacement (TEJR).
There is a valgus angle of about 4° between the trochlear (greater sigmoid) notch of the ulna and the ulnar shaft (32, 34). The opening of the trochlear notch is angled ca. 30° posteriorly with respect to the long axis of the ulna; this allows better approximation in flexion to the 30° anterior rotation of the humeral articular condyles (34). The joint surface of the trochlear notch forms an arc of about 180°; however, it is not entirely covered with cartilage: in over 90% of individuals, a bare area covered by fibro-adipose tissue extends transversely across the mid-portion of the trochlear notch; this feature accounts for the frequency of fractures at this site, and permits a trans-olecranon approach to the joint (34).
The radial head is covered with cartilage over four fifths of its circumference. The 15° angulation between the neck and the shaft of the radius leaves an excursion of 180° for forearm rotation(34).
The capsule is attached around the articular surfaces, and blends with the annular ligament. It covers the tip of the olecranon, the coronoid process, and the radial fossa. The fibres are arranged in such a way as to provide stabilization in flexion and in full extension(23). When the elbow is stiff, the capsular capacity will be reduced by more than 50%; equally, the capsular compliance of the stiff elbow will be very poor, which shows that the capsule itself has been compromised(14). The position of minimum intracapsular pressure ("resting position") is around 60-70° of flexion, which means that prolonged immobilization of the elbow in this position - as practised since the days of Ambroise Paré - will increase the risk of capsular contraction(14).
The medial collateral ligament is a strong and well-demarcated structure that consists of three bundles (Fig. 5):
On the lateral side, there is no discrete collateral ligament in the strict sense of the term. Anatomical patterns vary widely, which is why the description of the structures involved has been difficult, and why disorders of the lateral collateral complex may be hard to understand(31, 32, 42, 43). There are five ligamentous structures involved in the lateral stabilization of the elbow joint (Figs. 6, 7):
About 60% of the axial loads imposed on the elbow will be transmitted through the humeroradial joint, as compared with only 40% through the humero-ulnar articulation(34). The stresses imposed on the elbow vary; they depend on the load applied, the resultant force vector, and the length of the lever arm. The loads may amount to 2-3 times the body weight, and to 8-10 times the lifted weight. This accounts for the compressive loads observed during simple activities such as dressing or feeding(48, 51). The use of crutches will transfer between 40% and 50% of the body weight onto the upper limb(51).
The elbow is a very congruous joint, and, hence, inherently very stable. In flexion, the coronoid process locks into the coronoid fossa, while the medial rim of the radial head engages in the trochleocapitellar groove(23). In extension, the apex of the olecranon is held in the olecranon fossa. Elbow stability is enhanced by the perfect congruency between the radial head and the radial notch of the ulna. Roughly speaking, the bony surfaces contribute 50% of the mediolateral stability of the elbow, while the other 50% comes from the ligaments(34). One important thing to bear in mind is that the role of each of these structures varies with the degree of flexion or extension of the elbow.
Seventy-eight per cent of the valgus stability of the elbow is contributed by the medial collateral ligament; the bony surfaces, including the humeroradial joint, have only an accessory function in the constraint to valgus stress of the elbow, although experimental studies have not as yet provided unequivocal evidence(19, 29, 33, 42, 48). In experiments, the insertion of a Silastic implant was seen to leave valgus stability unaltered(19). By and large, valgus stability comes from the bony structures below 20° and above 120° of flexion, and from the anterior bundle of the medial collateral ligament over the in-between range(11). The flexor-pronator group is bulky, but does not appear to provide dynamic support of the medial aspect of the elbow(16). The radial head has only a secondary role, providing about 30% of the stability on the lateral side(19, 23, 33). The minor importance of the radial head as a lateral stabilizer is illustrated by the fact that radial head excision will not adversely affect the joint, providing that the medial collateral ligament is intact. However, a distinction must be made between elbow valgus stress, which is checked by the medial collateral ligament, and external rotation (or supination) stress, which is checked by the lateral collateral ligament(43).
There is much less agreement concerning the roles of the different ligamentous structures in varus stability. Initially, it was thought that the annular ligament was chiefly responsible for resistance to varus stress between 40° and 60° of elbow flexion(49). According to this author, the lateral collateral ligament serves to stabilize the annular ligament. This idea was contested by several authors(48), which prompted Søjbjerg et al. to reinvestigate this subject. They showed that the isolated division of the lateral collateral ligament resulted in 15° of varus (at 110° of flexion), and that the division of the lateral ulnar collateral ligament had little influence on the instability observed(43). Thus, it is the lateral collateral ligament complex, and in particular the lateral collateral ligament, that stabilizes to varus and extension loads(34, 43, 49). The sole function of the annular ligament appears to be the stabilization of the radio-ulnar joint.
The anterior joint capsule resists distraction, and, under those conditions, provides 85% of the resistance observed(33).
In the sagittal plane, stability also depends on the medial collateral ligament(33). Loss of less than 50% of the olecranon will not interfere with function, providing that the collaterals are intact(4). Valgus stability is provided largely by the proximal portion of the trochlear notch of the ulna (85%), while varus stability is chiefly a function of the distal part of this notch (65%)(4, 23). In the sagittal plane, bony stability in extension comes from the coronoid process(23, 47). This bony and ligamentous stability is enhanced, in the sagittal plane, by the powerful action of the muscles around the elbow.
In addition to the standard orthopaedic history, the following items of information should be obtained from patients presenting with elbow dysfunction: age, duration of the complaint, or time since onset of the elbow-related symptoms. The dominant side needs to be ascertained; specifically, it must be established whether there has been a recent reversal of the natural dominance, which would show that function has been severely impaired.
The severity of the patient’s pain is assessed using a visual analogue scale. The site of the pain may provide valuable clues. Conditions involving the lateral compartment (radiocapitellar joint) provoke pain that extends over the lateral aspect of the elbow, with radiation proximally to the midhumerus and distally over the forearm; this pain may be deep. Diffuse pathological conditions, on the other hand, cause pain that is described as periarticular in distribution(55).
The patient should be questioned about locking, pain and/or instability during throwing movements, joint swelling, or fleeting inability to extend the elbow, which would suggest a joint effusion.
Paraesthesiae of the hand may, in some cases, be related to ulnar nerve compromise at the level of the elbow.
A note should also be made of any previous treatments of the elbow (synoviorthesis, intra-articular injections, surgery).
Since the elbow is a superficial joint, many of its disorders can be readily detected by simple inspection. The patient should be suitably undressed to the waist for examination. Since, at the front, the muscle masses obscure the joint, much of the examination will need to be conducted with the examiner sitting or standing behind the patient. The patient should be standing, with shoulders slightly braced back, to display the elbow.
When the forearm is in full extension and supination, there will be a physiological valgus ("carrying angle") of 9-14°; in women, the angle will be 2-3° greater (8, 18, 35, 55). This angle has been found to be 10-15° greater in the dominant arm of throwing athletes (5). This angle allows the elbow to be tucked into the waist depression above the iliac crest; it increases when a heavy object is being lifted (Fig. 8). Any increase in, or loss of, this physiological angle is indicative either of major elbow instability or of malunion. However, the angle varies from valgus in extension to varus in flexion, and its measurement is not of any practical importance(48).
Sometimes, on the side of the elbow, bulging in the para-olecranon groove will be seen; such a swelling is produced by an effusion or by synovial tissue proliferation (55). On the back, prominence of the olecranon is a sign of posterior subluxation of the elbow, a feature commonly found in RA (55).
Rheumatoid nodules are extremely common; they are usually found on the posterior aspect of the elbow, mainly on the medial aspect of the extensor surface. The nodules should be counted and their volume noted: large nodules may cause skin ulceration and harbour infection. A note should also be made of their site, since they may cause problems if they are over an intended surgical approach to the elbow.
Bursitis is also a frequently encountered pathology, especially in RA patients. As with nodules, the volume of the lesion and the quality of the overlying skin should be noted.
Inspection may also show skin atrophy at steroid injection sites, or scars from previous surgery. These features must be noted, since they may affect the surgical approach to be employed.
Palpation starts at the posterior aspect, with the patient standing with his or her shoulder braced backwards. The three palpation landmarks - the two epicondyles and the apex of the olecranon - form an equilateral triangle when the elbow is flexed 90°, and a straight line when the elbow is in extension (Figs. 9, 10).
Since the elbow is a very superficial joint, it can be readily palpated from behind and from the sides. The posterior aspect has the olecranon mid-way between the medial and the lateral condyle. Slight elbow flexion will bring the olecranon out of the olecranon fossa, in which it lodges in extension; in this position, the proximal portion of the fossa on either side of the triceps tendon may be palpated (Fig. 11).
The olecranon bursa is not in communication with the synovial cavity. This is why the elbow may be mobilized in bursitis, and why even massive bursitis will not be tender. In chronic bursitis, a boggy globular mass may be palpated; the overlying skin will be thickened. Flat, hard nodules may be felt under the palpating fingertips(12). In infected bursitis, the skin will be tight and shiny; streaks of lymphangitis will be commonly seen; while in 25% of the cases, the axillary lymph nodes will be enlarged(12).
On the lateral side, the main landmarks are the lateral epicondyle proximally and the radial head distally. The supracondylar ridge is also very accessible to palpation; its chief value is that of a landmark for surgical approaches (Fig. 12). Sometimes, palpation may be carried out all the way up to the deltoid tuberosity. The radial head is palpated with the examiner’s thumb, while the other hand is used to pronate and supinate the forearm (Fig. 13). The head is about 2 cm distal to the lateral epicondyle(5). Inside the triangle formed by the bony prominences of the lateral epicondyle, the radial head and the olecranon, the joint itself is palpated, to detect even very minor effusions or low-grade synovitis (Fig. 14).
The muscles on the lateral side may be palpated individually. For the palpation of brachioradialis, the patient is asked to clench his or her fist and flex the elbow with the forearm in neutral position (mid-way between pronation and supination) and with the fist blocked under a table (Fig. 15). The wrist extensors are palpated by asking the patient to extend the forearm at the elbow against resistance (Fig. 16). Extensor carpi radialis longus produces both flexion and abduction of the wrist. Anconeus may be palpated behind the radial head, on the side of the olecranon; it increases in bulk when the forearm is extended against resistance(35).
From the medial side, the joint is not very accessible to palpation, and the small amount of synovial tissue on the medial border of the olecranon makes joint palpation difficult(35). Palpation of the ridge that provides insertion for the intermuscular septum is useful mainly as a guide for surgical approaches. Also, the supracondylar lymph nodes may be palpated at this site (Fig. 17). Over, and slightly anterior to, the supracondylar ridge, a bony excrescence may be palpated; this outgrowth may irritate the median nerve(5). This supracondylar process is present in 1-3% of the population, and is seen at a distance of 5-7 cm above the joint line(32). Behind the septum, the ulnar nerve may be palpated; in patients with a very mobile nerve, it may be seen to roll on the medial condyle(10) (Fig. 18). Ulnar nerve instability is more easily tested with the arm in slight abduction and external rotation, with the elbow flexed between 20 and 70°.
Anteriorly, the bulk of the flexor-pronator group restricts the extent of joint palpation. The flexor-pronator muscles must be tested as a unit, by asking the patient to perform wrist adduction and flexion against resistance (Fig. 19). Next, each one of these muscles should be tested individually. The anterior aspect does not lend itself to palpation, since it is tucked away behind the muscles. Laterally, brachioradialis will be felt; and in the middle, the biceps tendon is readily accessible if the patient is made to flex the forearm against resistance. Lacertus fibrosus is palpated medial to the biceps tendon; the pulse of the brachial artery will be felt deep to this aponeurosis (Fig. 20). Sometimes anterior protrusion cysts produced by herniated synovial membrane may be felt(52).
The main function of the elbow is to bring the hand to the mouth; this is why the investigation of the elbow range of movement (ROM) is an important part of the examination process. Any difference between passive and active mobility is usually due to reflex inhibition from pain(55). The end-feel - the feeling transmitted to the examiner’s hands at the extreme range of passive motion - must also be assessed (Table 1). If the feel is abnormal, there is usually something wrong with the joint.
Table 1 Classification and description of end-feels (modified from TS Ellenbecker & AJ Mattalino)(12a)
The normal flexion-extension range is 0 to 140° (+ 10°). Mobility is measured with a goniometer placed on the side of the arm and forearm; the measurement thus obtained will be reliable to within 5° of accuracy(35) (Fig. 21). This ROM is well in excess of what is needed for the majority of activities of daily living (ADLs). The useful arc of motion is between 30° and 130° of elbow flexion; most ADLs require an arc of only 60-120°(30, 33, 55) (Fig. 22).
Loss of extension provides a very sensitive clue to intra-articular elbow pathology, since extension is the first sector of the ROM to be affected, and the last to recover(55). However, since the extension deficit shortens the lever arm, it is well tolerated up to a loss of 45°(55). At the end of flexion, there will be a soft-tissue approximation end-feel as the movement is blocked by the bulk of the arm and forearm muscles. At the end of the normal extension movement, there will be a bony end-feel, as the olecranon locks into the olecranon fossa(5).
Pronation and supination cannot be complete unless the proximal and distal radio-ulnar joints are in correct anatomical relationship, the two bones are of normal length relative to each other, and the interosseous membrane is intact(55). The arc of motion varies widely in different individuals; the mean values are 70° pronation, and 85° supination (Figs. 23, 24). However, with only 50° pronation as well as supination, most ADLs can be readily performed(30, 55). At the end of pronation and supination, there will be a capsular end-feel(5).
Stability testing is performed with the patient standing, shoulder braced backwards; the examiner is behind the patient. The elbow is slightly flexed, to bring the apex of the olecranon out of the fossa. Varus stability is checked with the humerus in full internal rotation, while valgus stability is tested in full external rotation (Figs. 25, 26). The physiological laxity of the elbow between 10 and 20° of flexion, in varus and in valgus, does not exceed 5°. In rotation (pronation and supination), it does not exceed 3°(49).
Patients may also be examined lying supine. In this case, the humerus is held with one hand, while the examiner’s other hand places the forearm in valgus (or in varus), with the elbow flexed 20-30° (to remove the olecranon from the fossa)(5, 39) (Fig. 27). With the patient’s abducted and externally rotated arm tucked under the examiner’s shoulder, the medial collateral ligament may be palpated at the same time(11) (Fig. 28). As we shall see in the section on instability, it is important for mediolateral stability to be tested in pronation and in supination.
Anteroposterior stability is controlled exclusively by the collaterals. Removal of the olecranon will not result in instability if the collaterals, and above all the medial collateral ligament, are intact. In RA patients, a search should be made for anteroposterior translation, which shows the extent of joint destruction. The forearm is flexed to 90° and held by the examiner with one hand, while the other hand holds the humerus, as anteroposterior stress is applied to the joint.
This examination forms part of the examination of the elbow; depending on the patient’s symptoms, a rough screen or a more detailed investigation will have to be performed.
At the elbow, the ulnar nerve may be damaged at several different levels: at the arcade of Struthers; in the ulnar groove behind the medial epicondyle; under the fascial band bridging the two heads of flexor carpi ulnaris (arcade of Osborne); and even under the deep aponeurosis of flexor carpi ulnaris(3) (Figs. 29, 30). Tinel’s sign, elicited at different levels, will give a clue as to the site of the compression (Fig. 31).
In the ulnar groove, the ulnar nerve may be affected by synovial proliferations herniating on the medial side of the joint; by bony lesions with spicules causing irritation along the course of the nerve behind the epicondyle; or by ischaemic events. Paraesthesiae of the ulnar border of the hand and the fingers are usually the first signs of ulnar neuropathy. Pain is a less frequent complaint; where it is encountered, it is usually localized to the elbow or along the medial edge of the forearm. These symptoms are commonly triggered or exacerbated by attempts to flex the elbow. Prolonged elbow flexion may produce the paraesthesiae reported by the patient. This test - known as the elbow flexion test, and analogous to Phalen’s test for carpal tunnel syndrome - can be made more discriminating by putting the wrist in extension, so as not to perform a Phalen test at the same time. In the more advanced stages, there will be ulnar nerve palsy as well.
The posterior interosseous nerve is the motor branch of the radial nerve. It can be found, at the back of the arm, using the three-finger method described by Henry: the index, middle, and ring fingers of the examiner’s hand opposite the examined side are placed on the posterior aspect of the radius, with the ring finger at the junction between the neck and the head of the radius. The nerve will then be under the tip of the index finger.
This motor branch of median nerve origin may be compressed where it courses between the two heads of pronator teres(17). Compression of this nerve will lead to weakness and even paralysis of the flexor digitorum profundus muscle of the index finger and the flexor pollicis longus muscle of the thumb. The patient will be unable to create an OK sign (pinching the tips of the index finger and the thumb together).
Testing the different muscles around the elbow forms part of the standard workup of patients with elbow complaints. Each muscle must be tested separately. Details of the technique to be employed will be found in the standard textbooks, such as Kendall’s(22). The global evaluation gives a picture of the extent of a nerve trunk or plexus lesion. Table 2 lists the actions, nerve supply, and nerve root derivations of the different muscles.
Table 2 Action and innervation of the muscles around the elbow
Testing the reflexes forms part of the neurological examination of the elbow. The biceps reflex is a C5 function (although the muscle is supplied by C5 and C6); the brachioradialis reflex is C6; and the triceps reflex, C7 (Figs. 32, 33, 34).
Pronator, supinator, and extensor strength is largely the same on the dominant and the non-dominant side; this is why a comparison with the unaffected side is the best test(13). However, flexor strength is always greater on the dominant side. A manual assessment of elbow strength, at 90° of flexion and with the forearm in neutral position, may appear somewhat crude. However, this isometric measurement is very reliable, yielding values close to the results of isotonic measurements, which are much more difficult to perform(6). Male subjects are about twice as strong as females, and the dominant limb is about 6% stronger than the non-dominant one(6). Extensor strength is about 60-70% of flexor strength(6, 35, 55). Supinator strength usually exceeds pronator strength by 15%(6, 35, 55). Strength must be assessed, especially in RA, because of the magnitude of mechanical stresses: a 1 kg weight at the hand produces a reactive force, at the 90° flexed elbow, of the order of 10 kg(55).
The elbow is situated between two highly mobile joints - the shoulder and the wrist. It can compensate only for flexion-extension deficits. As regards flexion, the overall capability for feeding (hand to mouth), body care (hand to face), and hair care (hand to back of head) should be examined. The activities looked at with regard to extension are opening doors, and reaching to grasp objects.
A search must be made for coexisting conditions affecting the lower limbs. The use of walking aids puts increased functional loads on the elbow, and may rule out elbow joint replacement. On the other hand, a hip or knee condition may have to be treated with surgery first, before doing elbow replacement, so as not to jeopardize the outcome of the elbow arthroplasty.
Maîtrise Orthopédique n° 77 - October 1998
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