Radial head

The elbow and wrist differ from most other joints in that certain movements (pronation/supination) are inextricably linked. This is accomplished by the mobile radius rotating around the static ulna. Proxi-mally, the radial head articulates with the radial notch on the lateral aspect of the coronoid process of the ulna. Distally, the ulnar notch of the radius rotates around the head of the ulna. In addition, the shafts of the bones are linked by the interosseous membrane. Damage to any of these structures may restrict pronation or supination. In adults, angulation or malrotation of more than 10 can result in restricted rotation of the forearm. For this reason, adult fractures are usually managed by open reduction and internal fixation. In children, the potential for remodelling is good around the wrist and more deformity can be accepted. 

Fig. 9.13. Both the forearm bones are malunited following fracturing in a 3-year-old child initially treated by osteotomy of the ulna. Arthrogram shows that the radial head is still subluxed and radial osteotomy is required...

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... 

A line drawn along the centre of the proximal radius should intersect the capitellum (the radiocapitellar line). Failure to do so suggests dislocation of the radial head. This rule is always valid on a true lateral image, in all stages of flexion (Storen 1959). 

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. 

The Monteggia lesion is dislocation of the radial head associated with a forearm injury. This should not he confused with the Galeazzi injury which is fracture of the radius and dislocation of the distal radioulnar joint. 

The dislocated radial head is an easily missed lesion, not infrequently resulting in litigation. The forearm fracture is readily identified and attention is drawn away from the co-existing elbow injury. It is vital that for long bone fractures, the adjacent joints are both imaged and properly reviewed. 

Monteggia injuries occur most frequently between the ages of 5 and 7. Patients will generally complain of forearm and elbow pain. If the ulna is fractured, pain will be maximal in the arm and there may be swelling and deformity. The elbow will also be swollen. In 10%-20% of cases, a neuropraxia of the radial nerve will be present, particularly if the radial head is dislocated laterally or anteriorly. Most of these nerve injuries will recover within 6-9 weeks and intervention is not indicated unless there is no sign of clinical or electromyographic recovery at 6 months. 

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. 

When imaging any long bone injury, it is imperative to include both the joint above and the joint below. Whilst Galeazzi lesions are rare in children, Monteggia lesions are not uncommon. It should also be stressed that the joint must be imaged in two planes. The elbow may look normal on the AP view but dislocation of the radial head is readily appreciated on the lateral projection. A straight line drawn up the shaft of the radius should intersect the capitellum in both AP and lateral views, irrespective of the degree of flexion of the joint (Fig. 18.13). 

Monteggia lesions. The articular surface of the radius is normally concave where it articulates with the capitellum. When the radial head has been dislocated for some time, the head becomes convex. This makes relocation of the joint difficult. Similar appearances may also occur in congenital dislocations of the radial head. In this instance, the dislocation is always posterior and thus confused with type II injuries. 

In acute presentations, the dislocated radial head can generally be reduced by closed means. Under general anaesthesia, the elbow is flexed to enable... 

Pulled elbow does not require manipulation under anaesthesia. The forearm is flexed and supi-nated. Often this results in a gratifying pop and the child resumes normal activity. If this manoeuvre is unsuccessful, simply resting the arm in a sling will allow swelling in the annular ligament to subside and the radial head will reduce within 2-3 days. 

Fig. 18.13a,b. Type I Monteggia fracture with plastic deformation of the ulna, a AP radiograph shows minimal displacement and dislocation could easily he missed, b Lateral radiograph clearly demonstrates the dislocated radial head... 

Fracture which is complete, displaced and rotated with loss of relationship of the radial head against the capitellum. 

The radial head may also be displaced following dislocation of the elbow, either during dislocation or following subsequent reduction. 

Jeffery (1950) has classified the primary displacement of the radial head ... 

Open reduction is indicated if percutaneous reduction fails, but only if angulation is more than 45°. The results are generally less favourable because of the risks of damage to the delicate blood supply to the radial head and because the initial injury is likely to be worse (Evans 1999b). 

The most common complication, seen in up to 40% of children, is a loss of forearm pronation, and to a lesser extent, a loss of supination. This is probably due to the formation of an incongruous joint and the formation of flbrous scar tissue about the radial head. Radial head overgrowth, secondary to increased epiphyseal growth, may be seen on radiograph but does not seem to cause functional impairment. 

Rarely, the radial head is completely displaced, often lying adjacent to the capitellum. This fracture can occur during the reduction of a dislocated elbow if there is an undisplaced radial neck fracture (Fig. 18.18). The radial head may be reduced by closed manipulation aided by manipulation with percutaneous K-wire. One should be careful to make sure that the reduced radial head is not rotated 180° (Wood 1969). 

These include fractures of the radial neck, lateral condyle, distal radius and subluxation of the radial head (Evans 1999a). Physeal fractures are rare and the majority of injuries are metaphyseal fractures. As with any other intra-articular fracture, it is important to restore the articular surface if the fracture is displaced. 

Fig. 18.18. a,b AP and lateral radiographs of radial neck fracture displaced by reduction of the dislocated elbow. Radial head lies adjacent to the capitellum. c Intraoperative radiographs showing intramedullary nancy nail and percutaneous wire used to manipulate the femoral head, d Post reduction film... 

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. 

B Extension Varus Ulnar metaphysis fracture +/- radial head subluxation... 

Extension inj uries are reduced by placing the arm into full extension, correcting the varus or valgus, treating the associated injury such as radial head or medial condyle fracture, before immobilising in a cast for 3 weeks in slight flexion. 

Wilkins KE, Morrey BE, Jobe FW, Kvitne RS, Coonrad RW, Figgie HE, Jupiter JB, Inglis AE, Wright PE, Burns EB (1991) The elbow. Instr Course Lect 40 1-87 Wood SK (1969) Reversal of the radial head during reduction of fractures of the neck of the radius in children. J Bone Joint Surg Br 51 707-710... 

Somatic dysfunctions in other areas of the body, such as the extremities, are still named for their freedom of motion. For example, the radial head may move anteriorly or posteriorly. If it moves freely posteriorly and is restricted in anterior motion, it is named a "posterior radial head." Likewise, when it moves freely in an anterior direction and is restricted in posterior motion, it is named an "anterior radial head."... 

During pronation and supination, the cupped radial head rotates about the knob of the capi-... 

Humeroradial articulation consists of the concave head of the radius articulating with the convexshaped capitellum of the humerus. Motion of this articulation must accompany humeroulnar flexion-extension. This angular motion is accompanied by ventral and dorsal translatory slide of the radius on the humerus dorsal radial slide with extension and ventral radial slide with flexion (Fig. 81-2). Extension stress is the major cause of posterior radial head somatic dysfunction. 

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... 

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