Chapter 13 Dislocations of the Elbow in Children
Introduction
Falls on the outstretched hand are common in childhood and occur in some toddlers on a daily basis. Approximately 65% of all fractures in children are to the upper limb, with the vast majority the result of indirect forces, following a fall on the outstretched hand (Fig. 13.1).2 The most common site of injury is the wrist and hand, with the elbow region accounting for approximately 10% of the total. Although elbow dislocations are much less common than fractures,3 it is important to make a prompt diagnosis since in the majority of patients this will enable closed reduction and result in a rapid return of normal function and appearance of the elbow. Delayed diagnosis or inappropriate management may require open surgical management and result in permanent functional loss.
Prevalence and associated injuries
A study of 1579 elbow injuries in skeletally immature individuals from Gothenberg, Sweden, found only 45 dislocations, giving a prevalence of only 3%.4 Subluxation of the radial head (pulled elbow) usually occurs in children aged between 2 and 4 years, while dislocations tend to occur around the time of physeal closure (12–14 years). The most common dislocation is posterior and may be accompanied by almost any fracture or combination of fractures, the most frequent being fracture separation of the medial epicondyle, fracture of the lateral condyle and fracture of the radial neck. Less common fractures occur to the coronoid and medial condyle. The Monteggia fracture dislocation is the most common fracture–dislocation combination in childhood (Fig. 13.2). Isolated dislocation of the radial head is uncommon.
Summary Box 13.1
Pulled elbow
Background/aetiology
Pulled elbow occurs in toddlers and children aged 1–6 years, with a peak incidence at age 2–4 years.5 The diagnosis is not tenable outside these narrow age limits. The injury is caused by longitudinal traction on the extended elbow, in a child young enough to have sufficient intrinsic elbow laxity to allow the radial head to slide partially out of the annular ligament. The toddler tries to go in one direction, while the parent pulls in another. As Mercer Rang wryly observed, the wonder is not that some children get a pulled elbow but that ‘it is remarkable that not all children experience a pulled elbow’.1
Originally it was thought that the injury occurred with the elbow extended and the forearm supinated. However, it is now widely believed that subluxation results when the pronated, extended forearm of an infant has forcible traction applied through the longitudinal axis. The typical scenario is a parent suddenly pulling their child by the arm. The annular ligament may simply be stretched or partially torn, and occasionally subluxates into the radiocapitellar joint (Fig. 13.3). The head of the radius subluxates distally but not beyond the equator, or maximal circumference, of the head. If it goes beyond this point, studies show that reduction becomes difficult, and these may go on to Monteggia type fracture–dislocations of the forearm with dislocation of the radial head.6
Outcome and literature review
The success rate of manipulation is very high and all pulled elbows appear eventually to self-relocate, without any long-term sequelae.7 Delayed presentation may result in failed manipulation. Failed manipulation or delayed return in using the arm should prompt a search for other injuries and include repeat examination and radiographs. Ultrasonography can provide inconsistent results8 and is very rarely used in our emergency department. Treatment of failed manipulation in a collar and cuff in flexion for a few days will result in successful relocation in all late-presenting cases and open reduction is very rarely necessary.9 A technique of forced pronation at the wrist, with or without flexion at the elbow, has been advocated by some authors. In a randomized control trial, parents perceived this technique to be less painful for their child.7
Recurrent episodes occur in 5–39% of children until the annular ligament becomes stronger and stiffer.10,11 Age at initial presentation of less than 24 months is a risk factor for recurrent subluxation,12 and some advocate immobilizing all manipulated elbows in a flexed and supinated position for 2 days to ensure a successful outcome.13
Summary Box 13.2
Elbow dislocations
Background/aetiology
Posterolateral dislocation of the elbow is typically the result of indirect trauma and most frequently occurs as the result of a fall on the outstretched hand. The mechanism is thought to begin with the elbow in either the semi-flexed or hyperextended position. The medial structures of the elbow joint are integral to joint stability, and axial force from a fall is transmitted to the medial elbow by the medial crista of the trochlear, exaggerating the natural valgus carrying angle of the elbow. When this valgus force is applied to either the hyperextended or semi-flexed elbow, the medial collateral ligament is torn or the medial epicondyle and common flexor origin are avulsed. In addition, the coronoid process is also at risk of fracturing. The anterior capsule is commonly disrupted, exposing the articular surface and increasing the danger of soft tissue or neurovascular structures being interposed during reduction. Disruption of the posterior capsule may also occur and contribute to the risk of recurrent dislocation.14 The brachialis muscle, in its position between the anterior capsule and the more superficial neurovascular structures, is at risk during dislocation of the elbow but is particularly liable to be torn if hyperextension forces are applied in order to achieve reduction of the joint (Fig. 13.4). Tearing of the brachialis may expose the median nerve and brachial artery, which are then stretched directly over the trochlea. Median nerve entrapment may occur during reduction, as originally described by Hallet.15
Arterial damage to the main brachial trunk is rare.16,17 However, complete rupture, an intimal tear or simple kinking into the elbow joint can occur because of the tethering effect of the collaterals and surrounding soft tissue restraints. Complete arterial rupture is more likely in open injuries. The most common vascular injury is a compartment syndrome resulting from swelling and secondary compromise to the brachial artery and collateral circulation. The risk factors are severe closed trauma, delay in treatment, closed reduction and immobilization in flexion in a complete cast. Severe ulnar nerve injury is less common now than previously described owing to the increasing recognition that entrapment of the medial epicondyle within the joint may also trap the ulnar nerve.18 Ulnar nerve injuries are usually transient.
Presentation, investigation and treatment options
Anteroposterior (AP) radiographs show the distal humerus superimposed distally over the proximal forearm, with the proximal radius and ulna usually displaced in a posterior and lateral direction. Lateral radiographs confirm a posterior dislocation of the elbow (Fig. 13.6A, B).
Given that more than 50% of elbow dislocations in children have associated fractures, the radiographs must be carefully examined for bony injuries (medial epicondyle, radial neck and coronoid).19 Less common fractures include lateral condyle, lateral epicondyle, medial condyle and olecranon.
Management and rehabilitation
The majority of elbow dislocations are managed by closed reduction. The principle of reduction is to counteract the muscle forces that are maintaining the dislocation. These are the brachialis and biceps anteriorly and the triceps posteriorly. These forces must be overcome so as to allow the coronoid process of the ulna and the radial head to pass unimpeded from posterior to anterior. Indeed, if not free to do so, these osseous landmarks are at risk of fracture. To unlock the radial head and coronoid process from behind the distal humerus, some authors have previously advocated initial hyperextension.20 This, however, has been shown to produce excessive force on an already stretched brachialis, which can cause rupturing of the muscle and the anterior capsule. Hypersupination is more useful and is often the critical step to unlock the radial head from behind the distal humerus.18
The two major techniques to reduce the elbow can be classified as ‘push’ and ‘pull’. First, traction longitudinally down the arm and supination of the forearm aids unlocking of the proximal radius and ulna. The now free radial and ulnar articular surfaces are then either pushed (from pressure on the olecranon) or pulled (via longitudinal traction on the forearm), enabling relocation of the joint. This is done while the elbow is being flexed, which helps maintain the reduction (Fig. 13.5).
Reduction is first assessed clinically by the correction of the fixed deformity, restoration of range of motion and reformation of the normal posterior bony landmarks. The stability of reduction should also be confirmed and the position maintained by a posterior plaster slab, extending from below the shoulder to the metacarpophalangeal joints. This is maintained for a period of 3 weeks in the majority of first time dislocators. A collar and cuff are applied to support the plaster slab. Repeat radiographs must be undertaken to confirm the reduction and a repeat neurovascular examination performed after the child has fully recovered from sedation or anaesthesia (Fig. 13.6).
Closed reduction is successful in more than 90% of isolated posterior dislocations.19
Indications for open reduction include failed closed reduction. This may occur due to interposed tissue, of which incarceration of the medial epicondyle within the joint is by far the most common. Additional indications are the treatment of associated fractures, existing open injury or the investigation of neurovascular compromise. Primary ligament repair is not an appropriate indication as studies have shown that the outcome is inferior to closed treatment.21,22