Current concepts in elbow fracture dislocation

Abstract

Background

Elbow fracture dislocations are complex injuries that can provide a challenge for experienced surgeons. Current classifications fail to provide a comprehensive system that encompasses all of the elements and patterns seen in elbow fracture dislocations.

Methods

The commonly used elbow fracture dislocation classifications are reviewed and the three-column concept of elbow fracture dislocation is described. This concept is applied to the currently recognised injury patterns and the literature on management algorithms.

Results

Current elbow fracture dislocation classification systems only describe one element of the injury, or only include one pattern of elbow fracture dislocation. A new comprehensive classification system based on the three-column concept of elbow fracture dislocation is presented with a suggested algorithm for managing each injury pattern.

Discussion

The three-column concept may improve understanding of injury patterns and treatment and leads to a comprehensive classification of elbow fracture dislocations with algorithms to guide treatment.

Introduction

Elbow fracture dislocations are complex injuries that can result in pain, instability or stiffness. Successful treatment requires recognition of injury patterns and application of an applicable management algorithm. Four patterns of fracture dislocation are recognised: posterolateral rotatory (terrible triad),^1,2 posteromedial rotatory instability (PMRI)^2,3 and Monteggia fracture dislocations or variants in which an axial and bending moment is applied to the proximal forearm.⁴ These can be divided into apex anterior injuries with an intact radial head or apex posterior injuries typically with an associated radial head fracture.⁵

Consideration of elbow fracture dislocation has focussed primarily on injury to the radial head, with sparse attention paid to the coronoid process. The coronoid process makes up approximately 60% of the buttress that holds the forearm on the humerus.⁶ Consideration of the coronoid process injury is central to our understanding of elbow instability and therefore to the management of fracture dislocations that disrupt the natural anatomy.⁷

Anatomy

Elbow stability is a function of osseous and ligamentous constraint and musculotendinous control. The contribution of each is not equal across the whole elbow. On the medial side, the olecranon and coronoid processes enclose the medial trochlea through an arc of approximately 170°, producing a high degree of concavity compression or constraint, which means that the ligaments and musculotendinous units on the medial side are of lesser importance. Laterally the radial head is relatively incongruent with a greater arc of curvature than the capitellum, and a shallower concave surface that only covers the capitellum over an arc of approximately 90°. As a result, the static and dynamic soft tissue restraints of ligaments and tendons are of much greater importance, and detachment of these soft tissue structures are more likely to result in symptomatic instability.^8–12

The coronoid process is an important primary stabiliser of the elbow. It is a fan-like structure that projects anterior and medial from the ulna to form the anterior wall of the greater sigmoid notch. The important elements of the coronoid process are the sublime tubercle, to which the strong anterior bundle of the medial collateral ligament is attached, the anteromedial and anterolateral facets, separated by a ridge that runs the length of the greater sigmoid notch.^13,14 The anteromedial facet has a mean surface area of 232 mm², compared to a mean radial head surface area of 247 mm², making the anteromedial facet a vital primary stabiliser.⁶ The anterolateral facet is a second degree stabiliser, with a mean surface area of 142 mm² that shares valgus stabilisation with the radial head. The anterior capsule inserts approximately 5 mm distal to the joint line, and the strong, broad insertion of brachialis lies just distal to this, reinforcing the coronoid and protecting to some degree against fracture. Fifty-eight per cent of the anteromedial facet of the ulna is unsupported and vulnerable to fracture in varus PMRI injury.¹⁵

The lateral ligament complex (LLC) is a condensation of the lateral capsule and is considered to be made up of the radial collateral, annular, lateral ulna collateral and accessary lateral ulna collateral ligaments. Recent laboratory evidence suggests that there is also a posterolateral ligament that is of significant importance to posterior stability of the radial head.¹⁶

Three column model of osseous elbow stability

To understand the impact of injury to these osseous elements for elbow instability, the elbow joint must be considered as three columns (Figures 1 and 2). The lateral column consists of the radial head and capitellum, middle column the anterolateral facet of the coronoid and the lateral trochlea, and the medial column the anteromedial facet and medial trochlea. The fulcrum for varus/valgus stability lies between the medial and middle columns; the primary restraint to valgus collapse is therefore the lateral column with a secondary contribution from the middle column. The sole restraint to varus collapse is the medial column. The middle column is unimportant when the lateral column is functional and is protected from injury by the columns either side, but removal of the lateral column makes the middle column essential for valgus stability (Figures 3 and 4(a) and (b)).

Figure 1.

Three-dimensional computed tomography reconstruction demonstrating the three columns of the proximal forearm: lateral (radial head), middle (anterolateral coronoid facet), and medial (anteromedial coronoid facet).

Figure 2.

Representative illustration of the three-column model demonstrating the natural fulcrum in between the middle and medial columns.

Figure 3.

Wrightington A fracture dislocation: loss of the medial column (anteromedial coronoid facet) with associated proximal avulsion of the lateral ligament complex and posterior band of medial collateral ligament results in varus instability. This pattern is commonly seen in posteromedial rotatory fracture dislocation.

Figure 4.

(a) Wrightington C fracture dislocation: combined loss of the middle (anterolateral coronoid facet) and lateral (radial head) columns with disruption of the lateral ligament complex results in valgus instability. This pattern is synonymous with the terrible triad fracture dislocation and will result in posterolateral rotatory instability if not surgically stabilised. (b) Restoration of the radial head and lateral collateral ligament complex will reliably restore stability in a Wrightington C fracture dislocation without the need to fix the anterolateral coronoid fracture.

It is important to recognise that these osseous injury patterns are associated with particular soft tissue injuries that further contribute to instability. The LLC is the most important soft tissue restraint as described above and, in most cases is avulsed from the humeral side.^2,12,17,18 Identification of the bony injury pattern from radiographs and CT grants pre-cognition of the likely associated soft tissue disruption.

Classification

Classification of elbow fracture dislocations can be confusing, with separate classifications for coronoid fractures, radial head fractures and Monteggia/Monteggia variant fracture dislocations.

The classification for coronoid fractures has evolved as the understanding of this important injury has developed. Early systems described the injury according to the proportion of height lost from the coronoid on the lateral radiograph.¹⁹ This fails to differentiate important injury patterns and can lead to underestimation of the degree of instability present. O'Driscoll et al. taught us that the classification required an appreciation of the injury in the coronal plane and in particular which of the three coronoid elements (sublime tubercle, anteromedial and anterolateral facet) were involved.¹²

Valgus external rotation injuries result initially in avulsion of the LLC, then fracture of the anterolateral portion of the radial head and lastly anterolateral facet coronoid fracture (terrible triad).²⁰ Varus internal rotation injuries result in fracture of the anteromedial facet of the coronoid and include avulsion of the LLC and posterior band of the medial ligament (PMRI).^2,3,12 Fracture extension into the sublime tubercle or to the anterolateral facet is possible but the important injury is to the anteromedial facet.³

For radial head fractures, the Mason classification with the Johnson modification is most commonly used.^21,22 This describes the spectrum of injury from type 1 and type 2 fractures that are partial articular fractures with or without displacement greater than 2 mm to type 3 (comminuted) fractures and type 4 (with associated dislocation). The Johnson modification may be misleading as for most type 3 and many type 2 fractures the elbow will have been dislocated at some point, even if the ulno-humeral joint is reduced at the time of presentation. The incidence of associated ligament injury is high with higher grade injuries.^23,24

Rineer et al. showed that for type 2 fractures loss of cortical contact of at least one fracture fragment is a predictor of elbow instability.²⁵ Hotchkiss proposed a more functional and treatment-based classification with type 1 defined as small marginal fractures with less than 2 mm displacement, no restriction to forearm rotation and no impact on stability. Type 2 fractures are larger with more than 2 mm displacement and amenable to internal fixation. Type 3 fractures are comminuted and not amenable to internal fixation.²⁶

Proximal ulna fracture dislocations, as described by Monteggia with proximal ulna fracture and dislocation of the radial head from the radiocapitellar and proximal radio-ulnar joints, were originally categorised by the Bado classification.⁴ Jupiter et al. highlighted the importance of the involvement of the coronoid process in understanding the treatment of proximal ulna fracture dislocations, particularly in relation to posterior dislocations.^5,27,28 Poor inter-observer reproducibility and confusion with Monteggia-like lesions has led to the development of other classifications. Ring divides adult injuries in to apex anterior and apex posterior proximal ulna fracture dislocations.^29,30 This simple and memorable classification is helpful. The radial head is likely to be intact in apex anterior injuries as it escapes the anterior humerus as it dislocates. In apex posterior injuries, the radial head is driven in to the capitellum often resulting in multifragmentary fracture. The prognosis is worse for these injuries and those involving the coronoid process.

In reality different fracture patterns exist that may involve any or all of coronoid anteromedial facet, coronoid anterolateral facet, radial head or proximal ulna. Therefore, it is useful to have a classification that describes the recognised injury patterns of elbow fracture dislocation and can guide treatment (Table 1):

Table 1.

Wrightington Classification of elbow fracture dislocation.

(A) Anteromedial facet fracture

(B) Bifacet fracture

(B+: Bifacet fracture with associated radial head fracture)

(C) Combined radial head and anterolateral facet or comminuted radial head fracture

(D) Diaphyseal proximal ulna fracture with dislocated intact radial head

(D+: Diaphyseal proximal ulna fracture with associated radial head fracture)

Application of the three-column model to injury patterns

If there is a fracture of the medial column, either as an isolated anteromedial facet fracture or in a bifacet fracture, there is no secondary restraint to varus collapse and the elbow is likely to be unstable.⁷

Type A (anteromedial facet)

In posteromedial fracture dislocation, the anteromedial facet is fractured (type A, medial column, Figures 3, 5(a) and (b)) and if the bone loss is sufficient to cause instability, restoration of the medial column is essential. This injury pattern is associated with lateral ligament sleeve avulsion from the humerus and avulsion of the posterior band of the medial collateral ligament from the medial epicondyle of the humerus.^3,12,31

Figure 5.

(a) and (b) Plain radiograph and 3D CT reconstruction demonstrating an isolated anteromedial coronoid facet fracture (Wrightington A). (c) Plain radiographs demonstrating fixation of Wrightington A fracture.

Type B (bifacet)

Bifacet fractures (type B, medial and middle column, Figure 6(a)) can occur as part of an extension type (apex anterior) Monteggia fracture dislocation/variant, or rarely in posteromedial rotatory fracture dislocation where the anteromedial facet fracture extends to involve the anterolateral facet. A bifacet fracture may also occur in association with a radial head fracture (type B+, medial middle and lateral column, Figure 7(a)) as part of a flexion type (apex posterior) Monteggia fracture dislocation or as a result of a direct posterior force on the supinated elbow. These are three column fracture dislocations with a poor prognosis if not managed appropriately. Monteggia fracture dislocation frequently occurs in patients with osteoporotic bone and may be associated with a high degree of fragmentation of the coronoid, often with extension to include the sublime tubercle.

Figure 6.

(a) Plain radiograph demonstrating an ulnar fracture extending proximal to and involving both coronoid facets with an intact radial head (Wrightington B). (b) Plain radiographs demonstrating fixation of Wrightington B fracture.

Figure 7.

(a) Plain radiograph demonstrating an ulnar fracture extending proximal to and involving both coronoid facets with an associated radial head fracture (Wrightington B+). (b) Plain radiographs demonstrating fixation of Wrightington B+ fracture.

Type C (combined anterolateral facet and radial head or comminuted radial head fracture)

The majority of terrible triad injuries do not involve the anteromedial facet of the coronoid but are unstable because both valgus osseous restraints have been fractured (type C, lateral and middle column, Figure 4(a) and (b)). Injury to the anterior band of the medial ligament may occur but the LLC avulsion is thought to be of greater importance. Restoration of the radial head (lateral column) will restore stability without fixation of the anterolateral facet coronoid fracture (middle column) as long as the lateral ligament injury is addressed.^26,32

Isolated radial head fractures are generally stable as only the lateral column is involved but where fragmentation of the radial head is present the associated injury to the lateral and medial soft tissue stabilisers may be sufficient to produce instability (type C, Figure 9) and may require lateral column reconstruction and soft tissue stabilisation. Posterolateral rotatory instability (PLRI) can occur in the presence of a minor radial head fracture if there is associated avulsion of the posterolateral ligament (Osborn Cotterill Ligament) or LLC due to low concavity compression. This can result in two grades of instability; grade 1 PLRI with isolated posterior ligament avulsion will typically result in a positive posterior draw sign but negative pivot shift test, and grade 2 PLRI with avulsion of the LLC with or without the posterior ligament in which the posterior draw and pivot shift tests will be positive.^2,16

Figure 9.

Management algorithm based on Wrightington Classification.

Type D (diaphyseal ulna fracture dislocation)

In some proximal ulna fracture dislocations, the ulna fracture is distal to the coronoid, that is intact and in continuity with the olecranon. The medial and middle columns of the elbow joint are intact (type D). The radial head (lateral column) is dislocated and intact (type D) or fractured (type D+, Figure 8(a) and (b)) and, as these are typically osteoporotic fractures, frequently multifragmentary. What differentiates a type D from type B is an intact coronoid and hence a stable ulnohumeral articulation.

Figure 8.

(a) and (b) Plain radiographs (pre and post fixation) demonstrating an ulnar fracture distal to and therefore not involving the coronoid with apex posterior angulation and an associated radial head fracture (Wrightington D+). What differentiates a type D from type B is an intact coronoid and hence a stable ulnohumeral articulation.

Surgical treatment

Surgical treatment is based on the anatomical principles outlined above and restoration of the essential osseous and soft tissue stabilisers (Figure 9).

Wrightington Type A

In anteromedial facet fractures with lateral ligament avulsion, stabilisation requires fixation of the LLC to anchor the lateral side and reduce the tendency for the forearm to drift into varus. Fixing the anteromedial coronoid facet may be required to restore the medial column. It has been suggested that fragments less than 5 mm in height can be ignored (Figure 5(c)). ^33–35 The posterior band of the medial ligament may need to be fixed if instability remains.

Wrightington Type B

Bifacet fractures require fixation of the coronoid process. Fixation of the LLC may be required. If the coronoid fracture is associated with a Monteggia fracture dislocation a plate should be applied to the ulna to restore the alignment of the olecranon and ulna diaphysis (Figure 6(b)).³⁶

Wrightington Type B+

Bifacet fractures associated with radial head fracture are the most unstable as all three columns are compromised. The priority is to address the coronoid fracture with a plate or screws. The radial head must be fixed or replaced to restore the lateral column. The lateral ligament is fixed once medial and lateral columns are restored (Figure 7(b)). The elbow should be stable but occasionally the medial ligament and common flexor may need to be addressed.

Wrightington Type C

The algorithm for managing type C (terrible triad injuries) is well described and the same principles are applied to the comminuted radial head fracture in isolation. As long as the radial head is fixed or replaced, and the lateral ligament is repaired it should not be necessary to fix the anterolateral facet coronoid fracture. If the coronoid fracture extends to include the anteromedial facet, then it becomes a Wrightington B+ fracture pattern and coronoid fixation is necessary. Residual instability can be addressed by repairing the medial soft tissue structures.^32,35,37 The use of a hinged external fixator should not be required but can be used if instability persists.

Wrightington Type D

In proximal ulna fracture dislocations distal to the coronoid process, where the coronoid is in continuity with the olecranon, the ulno-humeral osseous stability is preserved. In apex anterior fractures described by Ring, the radial head is dislocated but intact and must be reduced. The lateral ligament is frequently torn from the humeral origin and needs to be repaired. The ulna fracture is plated to restore the relationship between the radius and ulna and to stabilise the forearm joint.³⁰

Wrightington Type D+

In apex posterior proximal ulna fracture dislocations with an intact coronoid, the comminuted radial head fracture frequently requires replacement and the lateral ligament repaired back to the humerus. Restoration of anatomical ulna alignment is important to judge the length of the radial head reconstruction, ensure congruous articulation of the radial head with the capitellum and restore forearm biomechanics.

Conclusion

The goal of surgical intervention is to restore stability to permit immediate range of motion. Surgical success is dependent on a clear understanding of pathoanatomy. The three-column concept of elbow fracture dislocation gives a model of instability patterns and an appreciation of surgical steps required to restore stability to the injured elbow. A comprehensive classification system for all fracture dislocations of the elbow described here can facilitate pattern recognition and provide an algorithm for management for these complex injuries. CT imaging will aid accurate classification with the use of 3D reconstruction in more complex cases, some of which may require treatment in specialist centres experienced with the management of these challenging injuries to obtain the best outcome for the patient. In this manuscript, we have provided radiographic examples of how the classification can be applied in clinical practice. A reliability study is underway to scientifically validate the classification.