Paediatric Proximal Ulnar Fractures

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Chapter 12 Paediatric Proximal Ulnar Fractures

Thomas Wirth

Introduction

Fractures of the proximal ulna comprise several types of olecranon fractures together with fractures involving the coronoid process. The reported incidence is between 4% and 7% of paediatric elbow fractures ¹^–³ and they are often seen as part of combined more complex elbow injuries. Their incidence may vary greatly, however, even between different regions of the same country. For example in the Malmö area of Sweden they represent only 1.7% of paediatric elbow fractures, which is equivalent to an annual incidence of 0.8 olecranon fractures per 10 000 children.²

The ossification process of the proximal ulna has a characteristic pattern and needs to be understood in detail when evaluating bony lesions of the olecranon. There is a continuous ongoing ossification of the proximal ulnar metaphysis that results in a change to the bony contour of the olecranon. From the age of 6 onwards the epiphyseal ossification centre appears. In some children this may occur as more than one ossification centre and in this situation the radiographic appearances may lead to the inappropriate diagnosis of a fracture.

There are no widely accepted classification systems for olecranon fractures (Table 12.1). Bracq¹ described a five-type classification system which was modified by Gicquel et al⁴ and which is based on the direction and localization of the fracture line. Another five-type classification system was introduced by Caterini et al.⁵ Their five categories differentiated between the direction of the fracture line, the degree of fracture displacement and the presence of associated injuries. A much more complex classification is described by Evans and Graham.⁶ They put emphasis on the anatomical site, the fracture configuration, the degree of intra-articular displacement and the type of associated injuries. The principal classification concentrates on four anatomically defined types: epiphyseal, physeal, metaphyseal and combined olecranon–coronoid process injuries. A simple two-group classification was advised by Papavasiliou et al.³ They separated intra-articular from extra-articular fractures, dividing the intra-articular fractures into four subgroups according to the degree of fracture displacement.

Table 12.1 Survey of different classifications of olecranon and coronoid process fractures

The mechanism of injury that produces different reproducible fracture patterns has also been used as a functional classification.⁷ In flexion type injuries the rare avulsion fracture and the much more frequent metaphyseal fractures of the olecranon occur. Fractures that result from injuries with an extended elbow usually result in greenstick type fractures of the olecranon with longitudinal fracture lines. They have associated injuries in 40–70% of cases. I am a firm believer in the functional classification and finds it very practical and useful.

Isolated fractures of the coronoid process are extremely rare. In total, they have an incidence of about 1–2% of all elbow fractures. Most frequently they are a result of a fracture dislocation of the elbow joint.

Summary Box 12.1

Proximal ulna fractures account for 4–7% of paediatric elbow fractures.

They comprise olecranon and coronoid process fractures.

Several classification systems exist (Table 1), of which the functional classification based on the mechanism of injury is practical and helpful in planning treatment.

Background/aetiology

Olecranon fractures can occur after a fall onto the flexed or extended elbow.

In fractures that result from a flexion type injury a tension force acutely pulls on the posterior part of the olecranon mainly through the power of the triceps brachialis muscle but with assistance from the biceps, which produces a flexion force. This leads to a separation of the olecranon by a fracture line perpendicular to the longitudinal axis of the ulna, either through the metaphyseal area of the proximal ulna or through the proximal ulnar growth plate. The fracture line usually extends into the joint, making the injury an articular fracture. A rare flexion type injury that results from a direct blow to the olecranon creates shear forces at the area of impact, leading to a vertical fracture line with an intact proximal radio-ulnar joint. In these fractures the posterior periosteum does not disrupt and has the effect of an internal tension band.⁷

The extension type injury usually needs an additional valgus or varus stress to cause an olecranon fracture. In a fall on the outstretched hand the elbow joint is overextended with the olecranon locked in the olecranon fossa.¹ Without additional valgus or varus stresses this injury mechanism most likely results in a supracondylar fracture. With additional valgus or varus stresses the olecranon may fracture in a greenstick type manner, producing longitudinal fracture lines that may extend well into the proximal ulnar shaft region. This fracture pattern is triggered by the specific anatomical properties of the growing proximal ulna. The olecranon represents a metaphyseal bony region with a strong periosteal sleeve. The periosteum may prevent true fracture displacement, allowing only for some bending in either a valgus or varus direction. This type of injury pattern makes associated lesions very likely.

Fractures of the coronoid process almost never occur as isolated injuries. They are in general part of an elbow dislocation that normally reduces spontaneously. When the ulna dislocates posteriorly, the coronoid process is fractured. In these injuries the attached capsule additionally applies a substantial pulling force to the coronoid process.

Summary Box 12.2

Olecranon fractures result from a fall on the flexed or extended elbow.

Flexion injuries result from either an indirect force from contraction of the triceps and biceps or, more rarely, from a direct blow to the olecranon.

Extension injuries are associated with overextension of the elbow together with a valgus or varus stress.

Coronoid process fractures occur as part of an elbow dislocation.

Presentation, investigation, treatment options

Flexion type injury

Extension type injury

Clinical presentation

In addition to local swelling, tenderness and painful restriction of elbow motion, minor or major angulation deformity of the proximal forearm may also be present. Both valgus and varus deformities can occur, depending on the deforming force during the fall. Additional deformities may be seen clinically at the elbow and forearm.

Radiography

Conventional radiographs of the elbow in two planes are obtained and usually clearly visualize the fracture. However, in undisplaced or minimally displaced greenstick type fractures it may be difficult to see the longitudinal fracture lines. Moreover, one has to search for additional fractures or dislocations in the region of the proximal radius (radial head and neck) and the elbow (lateral condyle and medial epicondyle). Sometimes oblique views may be helpful.

The incidence of associated fractures is estimated to be around 40–50%,^1,^5,⁶ with 20–31% being radial neck fractures (Fig. 12.2) and 3.5–12% lateral condyle fractures.^1,⁴^–⁶ Other accompanying lesions such as an elbow dislocation or medial epicondyle fractures are very rare. A proximal ulnar fracture may also be combined with a fracture dislocation of the radial head, leading to a Monteggia equivalent fracture pattern (Fig. 12.3),¹⁰ which account for 5–7.5% of associated lesions.^5,⁶

Figure 12.2 (A, B) Fall on the outstretched arm with some valgus stress, leading to an extension type olecranon fracture associated with a mildly displaced radial neck fracture. (C, D) The result after conservative treatment with an above-elbow plaster in 80° of flexion for 4 weeks.

Figure 12.3 (A, B) Displaced proximal olecranon fracture with associated radial head dislocation (Monteggia fracture) after a fall on the extended arm. (C,D) The result prior to removal of metal after managing the fracture by closed reduction and intramedullary stabilization of the ulna in the Morote technique.

Treatment options

The treatment has to address the olecranon fracture itself and the associated injuries. In most cases closed reduction without internal fixation is sufficient to treat the olecranon injury (Fig. 12.2). In severely displaced fractures or those that involve the joint line, closed reduction and K-wire pinning or even open reduction and pinning in an anatomically reduced position may be necessary. Special fracture configurations may require fixation by K-wires and tension band techniques or, in oblique fractures, screws or very rarely plate fixation. If the fracture extends into the proximal ulna, intramedullary rodding, i.e. in the Morote technique, is a good method of fixation (Fig. 12.3).

There is a risk that the initial reduction may be lost and, if the fracture is not stable following reduction, internal fixation should be considered.

All associated injuries must be addressed according to their individual needs and these may dictate the whole treatment plan.

Coronoid process fractures

Clinical presentation

Clinically there are no specific signs that differentiate coronoid fractures from other elbow injuries. However, one should be suspicious of a coronoid fracture if the patient reports typical symptoms of an elbow dislocation. There is usually significant swelling of the elbow with marked local tenderness and an inability to move the joint. In addition, clinical examination may reveal evidence of joint instability.

Radiography

Fractures of the coronoid process are easily missed on conventional elbow radiographs because of the overlap of part of the radial head on the lateral view. In the AP view the coronoid process is often obscured by the bony olecranon. Although AP and lateral radiographs of the elbow should be obtained, if there is doubt regarding the integrity of the coronoid process, oblique views of the elbow are very strongly recommended.

A classification system based on the size of the fractured coronoid process has been proposed and is useful as it guides treatment options.¹¹ In type one there is an avulsion of the tip of the coronoid process, in type two less than 50% of the coronoid process is involved and in type three more than 50% is involved (Table 12.1).

Treatment options

After reduction of the elbow dislocation the size and displacement of the coronoid process fracture should be assessed. An undisplaced or minimally displaced fracture can be treated by plaster cast immobilization in neutral rotation of the forearm. Larger and more displaced fragments are an indication for open reduction and internal fixation (Fig. 12.4).

Figure 12.4 (A, B) Displaced type 2 coronoid process fracture. On the lateral radiograph of the elbow (A) the fragment is projected intra-articularly. (C, D) The reduction was done by an anterior approach and fixation was made with two K-wires being bent on the posterior ulnar cortex, thus pulling the coronoid fragment down into place.

Clinical Pearl 12.1

The diagnosis of olecranon and coronoid process fractures can be very difficult, particularly in young children where the olecranon is unossified and the coronoid process is barely visible on conventional radiographs. In these situations oblique radiographic views or ultrasonography may help to identify the fracture.

Clinical Pearl 12.2

It is helpful to identify the mechanism of injury in order to fully evaluate the fracture pattern. This will facilitate the detection of associated injuries such as radial neck, lateral condyle or Monteggia equivalent lesions. To miss an associated fracture potentially risks a poor outcome.

Summary Box 12.3

Undisplaced or minimally displaced flexion injuries can be treated in plaster with the arm at 80° to 90° of flexion.

Moderately displaced flexion injuries require closed reduction and percutaneous pinning.

Severely displaced flexion injuries should be treated by open reduction and tension band wiring.

Extension type fractures can be treated with a similar protocol but it is also important to treat any associated injuries.

Coronoid process fractures require open reduction and internal fixation if the fragment is large and displaced. Small undisplaced or minimally displaced fragments can be treated conservatively in a plaster cast.

Surgical techniques, rehabilitation

Olecranon fractures

Closed reduction

Undisplaced, minimally or mildly displaced flexion fractures in a cooperative child can be managed under sedation and pain relief. After reduction of the fracture has been confirmed by image intensifier control, a split above-elbow plaster in 80–90° of elbow flexion is applied for 3–6 weeks, depending on the age of the child. Follow-up radiographs should be obtained after 7 and 14 days and at the end of plaster treatment. If the follow-up radiographs reveal any loss of position, open reduction and internal fixation should be performed.

Undisplaced and mildly displaced extension type fractures without associated injuries can be treated similarly. The plaster is then applied in a neutral elbow position.

Moderately and severely displaced flexion fractures and all extension fractures with associated injuries should be managed under general anaesthesia. An attempt at closed reduction is undertaken and, if an anatomical position is achieved, percutaneous K-wire pinning is recommended to maintain the reduction. This is also the treatment of choice for all fractures that can be perfectly reduced by closed means but then immediately lose position. A split above-elbow plaster is applied for 4 weeks.

Open reduction

All severely displaced fractures and those that cannot be reduced anatomically are treated by open reduction and internal fixation through a direct posterolateral approach. Fragment fixation is achieved using K-wires only, K-wires plus a tension band with absorbable sutures or figure-of-eight wiring (Fig. 12.1). Even screws alone and tension bands attached to screws have been successfully used.

A different fixation concept which also facilitates metal removal uses two threaded pins and an adjustable lock for fracture compression. Preliminary results in a small group of patients are reported to be good.¹² After open reduction an above-elbow split plaster is used for immobilization for 2 weeks. Functional treatment is established as early as possible, provided the fixation is stable.

Of all of these fixation methods, the tension band techniques have been shown to have higher biomechanical stability than K-wires and screws alone. The tension band wires in combination with screw fixation have proven to be the strongest.¹³ There is a tendency to use strong absorbable sutures such as PDS instead of wires as the tension band since these do not require removal.¹⁴ However, a biomechanical study that tested the strength of fixation of both constructs found lower failure loads and fewer compression forces at the fracture site when absorbable sutures were being used.¹⁵ For this reason, in older children ordinary tension band wiring should be used to allow for early functional treatment.

For all extension type injuries it is mandatory to address the associated injuries at the time of the primary treatment. Frequently, the realignment of the proximal ulna leads to reduction of the associated fracture or dislocation. Fixation of these associated fractures may require intramedullary wiring of a radial neck fracture or open reduction of a lateral condyle or medial epicondyle fracture. The postoperative treatment is determined by the most severe part of the injury.

Coronoid process fractures

Undisplaced, minimally and moderately displaced fractures of the coronoid process with small and medium-sized fragments are managed conservatively, if the elbow is stable enough to allow early functional treatment. A split above-elbow cast is applied for 2–3 weeks, followed by early motion and intensive physiotherapy. For cases with persistent elbow instability and larger fragments we advise open reduction and K-wire or screw fixation through an anterior approach (Fig. 12.4). We also aim for early functional treatment after a 2- to 3-week period of plaster immobilization.

Clinical Pearl 12.3

The fixation technique used must be adequate. In young children tension band wires may cause growth disturbances and deformities of the olecranon and should therefore be used with great caution. If used, they need to be taken out soon after complete fracture healing. Growth plate damage must be avoided.

Outcome

The published results of olecranon fracture treatment are very good.¹⁶ In Braq’s series of 83 cases¹ there were 86.5% favourable outcomes. In a medium-term study of 35 patients, all 23 patients with a fracture displacement of less than 3 mm and who were treated conservatively had a satisfactory outcome. Of the 12 patients who underwent open reduction and internal fixation, 10 could be reviewed and all demonstrated a satisfactory result.¹⁷

In a long-term case series follow-up of 39 patients who had sustained their fracture at an average age of 7.4 years and were reviewed at an average age of 32 years, only 7.6% had poor results. Thirty-four patients had a good result and in 85% of the cases an intra-articular fracture was noted. The long-term prognosis was related to the anatomical site of the fracture line and to the presence of associated lesions, which were noted to be a negative predictor.⁵

Other authors have reported very good clinical results in 85–90% of cases.^1,^4,^16,¹⁸ The radiological outcome, however, was less favourable in some series. In Gicquel et al’s study⁴ 35% of patients had unsatisfactory reduction of their fractures on the postoperative radiographs. The disappointing radiological follow-up, however, did not have any impact on the longer-term clinical outcome.

All series have stated that associated lesions contribute clearly to worse clinical results ^1,^4,⁶ and radiological appearances.^1,⁶

The general outcome of coronoid process fractures is very closely linked to the outcome of the primary injury, which is the elbow dislocation. The problems that may occur include persistent restricted range of motion or persistent joint instability. In addition, there may also be angular deformity due to growth disturbances around the elbow joint.