Introduction

Fractures of the distal humerus are complex and demanding injuries to treat. Understanding the anatomy of the distal humerus and the various fracture patterns is crucial for achieving a satisfactory outcome.

The humerus flattens and widens distally, with the maximum width between the epicondyles. The distal articular segment is held by the medial and lateral columns of thick cortical bone. A thin plate of bone between the columns constitutes the olecranon fossa posteriorly and the coronoid fossa anteriorly. This accommodates the olecranon and coronoid processes on extension and flexion respectively. The medial column diverges from the humerus at an angle of 45° and the proximal two-thirds are made of thick cortical bone, but the distal part is composed of soft cancellous bone. The triangular shape of the medial column enables screw placement for fracture fixation. The lateral column diverges from the humeral shaft at about 20° and has cortical bone similar to the medial column and also allows good fixation for screws. The distal part of this column is complex, with soft cancellous bone. The capitellum forms part of the lateral column.^1,2 It has a curved anterior articular surface that articulates with the radial head. Posteriorly the surface is non-articular and therefore can be used for screw placement, although care should be taken not to penetrate the articular surface (Fig. 16.1A, B). The common extensor origin from the lateral column and the flexor origin from the medial column are responsible for fracture fragment rotation following injury.

Figure 16.1 The anatomy of the distal humerus.

From Ross LM, Lamperti ED, consulting eds. Thieme atlas of anatomy. Georg Thieme: Stuttgart; 2006.

The articular portion projects anterior to the shaft of the humerus at about 40° in the sagittal plane; hence it is not well exposed through a posterior approach (Fig. 16.1C). It also has a valgus angulation of 4–8° to the shaft in the coronal plane.³ Restoring the articular anatomy and stabilizing the two columns without impingement of the fossae by metalwork is the key to successful surgical management of these complex injuries.⁴

Background/aetiology

Distal humeral fractures have a bimodal age distribution, affecting the young (high energy) or the elderly (low energy). Peaks of incidence have been noted in males aged 12–19 years and in females aged 80 and older. The most common mechanism of injury is axial loading of the distal humerus, by a simple fall. The next most common causes of fractures are road traffic accidents and sport.⁵

Fractures of the distal humerus account for approximately 2–6% of all fractures and about 30% of all elbow fractures.⁶ One epidemiological study from Finland showed that the age-adjusted incidence of osteoporotic fractures of the distal humerus increased, from 12/100 000 women in 1970 to 28/100 000 women in 1995 and it predicts a threefold increase by the year 2030.⁷

Classification

Various classification systems have been proposed for distal humeral fractures. In 1969 Riseborough and Radin developed a system of classifying T-shaped intercondylar fractures of the distal humerus based on the degree of fragment displacement, rotation and comminution.⁸ The AO group devised a classification system dividing the distal humerus into three types based on fracture lines lying extra-articularly, intra-articularly with or without involvement of a single column, and intra-articularly involving both columns. Stepwise progression into grouping and subgrouping of these fractures is dependent on the site of the fracture lines and the degree of fracture comminution. Fractures that do not fall into any of the three types or nine groups are labelled type D or .4, respectively.⁹ Later, Mehne and Jupiter developed a classification system based on three broad groups of fractures. Intra-articular fractures are subdivided into those with either single-columnar or bicolumnar involvement or those involving the capitellum or trochlea. Extra-articular, but intracapsular, fractures are also subdivided depending on the proximity of the fracture to the joint. Epicondyle fractures represent extra-articular fractures in this classification.¹ In an assessment of these classification systems, Wainwright et al concluded that they were neither reliable nor reproducible, and thus their usefulness in decision making and comparison of outcomes was questionable.¹⁰ More recently, a clinically useful classification for fractures of the distal humerus has been developed and validated.¹¹ This classification system has three main components – extra-articular, predominantly intra-articular and predominantly articular (Fig. 16.2) – based on plain AP and lateral radiographs. The classification system was found to be both substantially reliable (k, 0.664) and reproducible (k, 0.732). It achieved superior inter-observer and intra-observer agreement compared with the other three classification systems, with a low proportion of unclassifiable fractures. A management algorithm used with this classification aids the surgical decision-making process for these complex fractures (Fig. 16.3).

Figure 16.2 New classification for fractures of distal humerus.

Figure 16.3 Management algorithm for distal humerus fractures.

Presentation and investigations

Classically patients present with a swollen, deformed elbow. The skin over the elbow may be disrupted as a result of the direct injury to the elbow. Careful neurological and vascular assessment of the distal extremity should be undertaken and recorded before any form of treatment is commenced.

Once a clinical diagnosis has been established, plain anteroposterior and lateral radiographs should be performed to confirm the diagnosis (Fig. 16.4A). Further imaging with a CT scan may be helpful in assessing the type of fracture and the number and orientation of the fragments (Fig. 16.4B). More recently, three-dimensional reconstruction CT scanning has been used (Fig. 16.4C). Although these require more time and may increase the overall cost of imaging, they have been shown to be easier to interpret than two-dimensional scans and are helpful in identifying the components and special orientation of complex articular fragments. This can be particularly helpful for preoperative planning of complex fracture fixations.¹²

Figure 16.4 (A) Plain radiographs of a patient with an open distal humerus fracture. (B) 2-D CT scan of the fracture. (C) 3-D reconstruction of the fracture.

Surgical technique and rehabilitation

The treatment of distal humeral fractures depends on the general condition of the patient and the type of fracture. The patient should be fit to have a prolonged anaesthetic and should be fully informed of the likely outcome of the procedure. The surgery should ideally be undertaken by a surgeon experienced in treating these injuries. He or she should have adequate resources and sufficient time to perform the operation. Inadequate surgical stabilization (i.e. K-wire stabilization) will result in poor outcomes, and salvage of failed surgery can be extremely challenging.

The patient should be positioned laterally with the upper arm horizontal and the forearm hanging vertically. This position allows excellent exposure for both internal fixation and prosthetic replacement. A high tourniquet should be applied.

A posterior incision centred on the tip of the olecranon is utilized. Although many surgeons place the incision just lateral to the tip of the olecranon it is our preference to make the incision on the medial side of the olecranon. This reduces the size of the posteromedial skin flap and facilitates identification of the ulnar nerve. The nerve must always be found and decompressed but whether anterior transposition is undertaken is a matter of surgeon preference.

The next stage of the surgical approach is dependent on whether internal fixation or joint replacement is to be performed. If internal fixation is to be undertaken it is important to have adequate exposure of the fracture in order to permit rigid reconstruction. We utilize the treatment algorithm outlined above.

If the fracture does not involve the articular surface, a paratricepital approach to the fracture usually provides adequate exposure, whereas if the articular surface is involved a chevron osteotomy is preferred. If an olecranon osteotomy is performed this should be undertaken through the non-articular portion of the bone midway between the olecranon and coronoid processes.

Reconstruction initially involves debridement of the fracture fragments, after which the fragments must be anatomically repositioned. Traditional AO advice involves reconstructing the articular surface, after which the articular portion of the fracture is reattached to the humeral shaft. Although this approach may be entirely appropriate for some fractures, it has been our experience that it is preferable to start the reconstruction with any fragments that clearly belong together and then build the reconstruction on those fragments. Preliminary fixation can be achieved using bone clamps and K-wires. Definitive rigid fixation must then be obtained by plating the fracture. This can be achieved using either the AO 90/90 plating technique or the more recently advocated parallel plating method.

With the AO method a reconstruction plate is usually applied to the medial border of the distal humerus with a dynamic compression plate on the posterolateral surface. Both plates will require bending to conform to the shape of the distal humerus. For this reason it is important to be fully aware of the distal humeral anatomy as inappropriate contouring of the plates will result in either a malunion or non-union of the fracture.

Pre-contoured plates have the significant advantage that when they are placed against the humerus, if they do not line up against the bone it is the bone that is in the wrong place rather than the plate. Knowledge that this is the case can be extremely useful when dealing with complex fractures, particularly if there are any fragments of bone missing.

Following fixation of the fracture the olecranon osteotomy should be reconstructed by tension band wiring or plating.

With articular fractures an olecranon osteotomy is the preferred surgical approach as this gives the greatest exposure of the articular surface. Once the fracture has been reduced and preliminarily held, definitive fixation can sometimes be achieved using the plating techniques described above but, in addition, supplementary fixation using headless screws may also be required.

If a preoperative decision is made that the fracture is not reconstructable, then either a hemiarthroplasty or total joint replacement should be considered. These options are described in Chapters 18 and 19.