Elbow olecranon

An estimation of the distribution of fracture patterns about the elbow is supracondylar (70%), lateral condyle (15%), medial epicondyle (10%), olecranon (5%), radial neck (1%), medial condyle (1%), capitel-lum (1%), T condylar (<1 %). 

Fig. 18.1a-g. Serial radiographs of the elbow showing the typical sequence of the appearance of the ossification centres, a No ossified centres b capitellum c radial head d internal (medial) humeral apophysis e trochlea f olecranon and g external (lateral) humeral apophysis... 

The articular surfaces of the elbow are contained within the joint capsule, which also encloses non-articular surfaces, including the coronoid, radial fossa and olecranon fossae. It attaches just distal to the coronoid and olecranon processes. The whole of the radial head is within the capsule. 

A number of equivalent lesions have also been described. Commonest of these is the Type 1 variant Where the radial head is dislocated anteriorly but the ulna has plastic deformation rather than a fracture. Other variants include dislocations with associated radial neck fractures, olecranon fractures and dislocations of the ulnar-humeral joint. In some respects, the pulled elbow , commonly seen in infants, can also be considered a Bado I equivalent. The injury occurs when the elbow has traction applied, usually resulting in hyperextension and pronation. The radial head subluxes through the annular ligament but does not truly dislocate and radiographs are either normal or will show an effusion with elevation of the fat pads. 

Fractures of the radial neck maybe isolated injuries but can occur in association with medial epicondyle avulsions, fractures of the olecranon and dislocations of the elbow joint. 

Olecranon fractures are occasionally seen in children and account for about 5% of fractures about the elbow. Fortunately, the majority of injuries are minimally displaced, and are managed non-operatively. A significant number of fractures have associated injury either to the elbow or to the wrist. 

Metaphyseal fractures can be classified according to mechanism of injury. The majority of injuries occur with the elbow in extension, the olecranon locked in the olecranon fossa and the maximum stress developed in the proximal metaphyseal region leading to fracture. When a valgus stress is applied, there may be asso ciated compression fractures of the radial neck and avulsion of the medial epicondyle. Varus stress is associated with radial head subluxation. 

Injuries with the elbow flexed during a fall occur as the olecranon is stressed over the fulcrum of the trochlea as the triceps attempt to resist the force acting on the distal ulna (Fig. 18.20). The line of fracture is oblique and intra-articular. This mechanism may also produce an extensor avulsion of the apophysis. 

In a flexed elbow, a direct blow to the posterior aspect of the ulna, just anterior to the distal humerus, can cause a shear stress on the olecranon metaphysis, breaching the anterior cortex and with the radius and distal ulnar fragment displaced anteriorly by the pull of the brachialis and biceps. This may occur with the elbow either flexed or extended, leading to either a transverse or oblique fracture pattern (Table 18.2). 

Childress HM (1975) Recurrent ulna nerve dislocation at the elbow. Clin Orthop 108 168-173 Evans MC, Graham HK (1999a) Olecranon fractures in children. J Pediatr Orthop 19 559-569 Evans MC, Graham HK (1999b) Radial neck fractures in children a management algorithm J Pediatr Orthop Part B 8 93-99... 

Extension of the elbow from the anatomic position is limited (5 to 10 degrees) by contact of the olecranon process with the fossa, tension in the anterior ligament, and resistance of anterior muscles. The triceps brachii is the only significant elbow muscle that functions in extension. There is some minor contribution by the anconeus. Because most elbow extension is accomplished by gravity, the triceps functions primarily against resistance. 

Somatic dysfunctions can involve contraction of the related muscles, compression of the neural elements, strain of the ligamentous aspects, and restriction primarily of the secondary motions of the joint components. The radial head typically entails posterior or anterior dysfunctions and may involve the muscles, the annular ligament, and the lateral collateral ligament. The humero-olecranon dysfunctions can involve the muscles, the medial collateral ligament, and can be related to symptoms involving the ulnar nerve. Restriction of elbow... 

The elbow should be examined first by observation. The carrying angle of the elbow should be noted, as should any swelling, which may be diffuse or localized to the olecranon bursa posteriorly. Signs of old or new trauma should be noted, such as scars, abrasions, bruises, and the like. 

The soft tissues and bony structures are then palpated to evaluate the integrity of the bones and the presence of any tenderness, masses, asymmetries, or crepitus. Any temperature changes should be noted, especially over the bursa and around the joints. Bony landmarks should be identified and compared between elbows. Swelling, especially over the olecranon bursa, should be noted. The olecranon bursa should not be palpable unless it is filled with fluid or thickened. 

Dynamic US of the elbow can be used to help demonstrate abnormal dislocation of the ulnar nerve, with or without snapping triceps syndrome. This finding typically occurs in the cubital tunnel, an osteofibrous tunnel formed by a groove between the olecranon and the medial epicondyle and bridged by the Osborn retinaculum. As described in Chapter 8, dynamic scanning during full elbow flexion can allow continual depiction of the intermittent dislo-... 

The elbow is one of the most stable joints of the body. In normal states, elbow joint motion ranges approximately from 0° to 150° of flexion and from 75° in pronation to 85° in supination. Elbow extension is limited by contact of the olecranon in the posterior humeral fossa, and tightening of the anterior band of the medial collateral ligament, of the joint capsule and of flexor muscles. On the other hand, the bulk of anterior muscles of the arm, the tension of the triceps and the contact of the coronoid process in the anterior humeral fossa limit elbow flexion. Pronation and supination movements are primarily limited by passive muscle constraints rather than ligaments. 

The posterior compartment includes the triceps and the anconeus muscles. The triceps is a large muscle made up of three heads-medial, lateral and long-from which it derives its name. The muscle bellies converge into a single thick tendon which attaches on the posterior aspect of the olecranon process. To increase the strength of extension of the elbow joint, the triceps tendon does not insert on the tip of the olecranon, but approximately 1 cm distal... 

The anconeus epitrochlearis is a small accessory muscle (prevalence ranging from 1% to 34%) that forms the roof of the cubital tunnel, replacing the Osborne retinaculum and joins the posterior aspect of the medial epicondyle with the medial aspect of the olecranon.. This muscle is often bilateral and can cause ulnar neuropathy by occupying space within the cubital tunnel and decreasing its free volume during full elbow flexion. Somewhat equivalent to the anconeus epitrochlearis, an anomalous myotendinous junction of the triceps may also be prominent over the posteromedial side of the cubital tunnel (see Sect. 8.5.4.S). 

Several synovial bursae around the elbow joint lessen friction between bones and the overlying skin and soft-tissue structures. The most important are the olecranon bursa and the bidpitoradial bursa. The olecranon bursa is a large subcutaneous bursa which intervenes between the skin and the olecranon process over the posterior aspect of the elbow. The bidpitoradial bursa (cubital bursa) lies deep in the anterior compartment of the elbow, between the distal biceps tendon and the radial tuberosity, to reduce friction between, especially during pronation of the forearm (Skaf et al. 1999). In fact, the radial tuberosity rotates posteriorly during pronation and wraps the tendon around the radial cortex. During this movement, the bursa is tracked between the tendon and the bone (Fig. 8.8). When distended by fluid, the bicipitoradial bursa may surround the biceps tendon completely and may cause a mass effect on the adjacent branches of the radial nerve. 

Cranial to the olecranon, US reveals the hypo-echoic bellies of the triceps muscle and its tendon that is located eccentrically and slightly medial with respect to the midline (Fig. 8.21). The distal triceps tendon appears hyperechoic and typically exhibits striations as it fans out toward its insertion on the olecranon, a pattern somewhat similar to the quadriceps. These striations, with alternating hypo- and hyperechoic bands, are more likely due to interposition of fat between the tendon fibers and should not be misinterpreted as tendinosis or tear (Fig. 8.22). If examined in full elbow extension, the distal triceps tendon may also appear wavy, possibly mimicking a rupture. Tendon laxity is particularly evident in the elderly and represents a normal finding (Rosenbe rg... 

The olecranon fossa appears as a wide and deep concavity of the posterior aspect of the humeral shaft filled with the hyperechoic posterior fat pad (Fig. 8.21a) (Miles and Lamont 1989). At both sides of this fossa, the posterior aspect of the medial and lateral epicondyles can be seen on transverse images. While examining the joint at 45 flexion, intra-articular fluid tends to move from the anterior synovial space to the olecranon recess, thus making the identification of small intra-articular effusions easier. Gentle rocking motion of the patient s elbow during scanning maybe helpful to shift elbow joint fluid into the olecranon recess. More distally, the... 

For evaluation of the posteromedial aspect of the joint, including the cubital tunnel and the ulnar nerve, the patient s elbow should be placed in forceful external rotation to enable visualization and palpation of the medial epicondyle and olecranon (Fig. 8.7a). This can be obtained either with the patient seated and the elbow extended and hyper-pronated with its dorsal aspect facing the exam-ineror, at least for the right side, with the patient... 

Distal triceps tendon tear is an uncommon condition that mostly occurs at or close to the olecranon process of the ulna, often associated with a fleck of bone attached to the retracted tendon as a result of avulsion fracture (Fig. 8.47). The mechanism involves either forced flexion of the elbow against a contracting triceps, as occurs during a fall on an outstretched arm, or relates to a direct blow onto the olecranon process. Local steroid injection into the olecranon bursa, anabolic steroid abuse and pre-existing tendinosis may also have a role in the tendon rupture. As a rule, complete tears occur more... 

Fig. 8.50a-c. Chronic traumatic olecranon bursitis in a manual laborer who had recently injured several times his posterior right elbow, a Midsagittal and b transverse 12-5 MHz US images over the olecranon process (O) show a markedly distended olecranon bursa (arrowheads) containing thick septa (curved arrows) and anechoic effusion (asterisks). Straight arrows, distal triceps tendon, c Photograph showing the bursal lump (arrows) on the posterior elbow... 

Fig. 8.62a-f. Dynamic study of the cubital tunnel in ulnar nerve dislocation. a-c Schematic drawings and d-f respective series of transverse 12-5 MHz US images obtained a,d with extended elbow and during progressive degrees of elbow flexion (b,e and c,f). When the elbow is extended, the ulnar nerve (arrow) is contained within the tunnel. Elbow flexion gradually pushes the nerve over the medial epicondyle (ME) until it snaps completely out of the cubital tunnel to lie superficial to the common flexor tendon origin (ft). 0, olecranon... 

Fig. 8.68a,b. Synovitis of the elbow joint posterior joint recess, a Longitudinal 12-5 MHz US image over the posterior olecranon recess with b T2w SE MR imaging correlation in a patient with rheumatoid arthritis presenting with painful elbow and loss of extension. US shows a bulk of hypoechoic synovial pannus fiUing the recess (arrows). Deep to the triceps muscle (tm), the posterior fat pad (asterisks) is elevated by the pannus. Note the prominence of the tip of the olecranon (O) and the humeral trochlea (TR) bulging within the recess... 

Fig. 8.71a,b. Synovitis of the elbow joint pitfall. a,b Transverse 12-5 MHz US images over the posterior olecranon recess a in a normal subject and b in a patient with rheumatoid arthritis and an olecranon recess (arrows) appears markedly distended by fluid. In a, the normal hypoechoic fat contained. In b the olecranon fossa, between the lateral (LE) and medial (ME) epicondyles, should not be confused with the synovitis process shown in b. In doubtful cases, careful dynamic examination with elbow flexion and extension movements may be helpful for the diagnosis. Note the erosion (arrowhead) on the posteromedial aspect of the lateral epicondyle. T, distal triceps tendon... 

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