Introduction

Severe comminution, bone loss and osteopenia predispose distal humerus fractures to unsatisfactory results due to inadequate fixation. Poor outcomes include contracture, secondary to prolonged immobilization thought necessary to protect the fixation, and non-union. In an effort to reproducibly obtain stable fixation in the presence of osteoporosis or comminution, we have developed an improved fixation technique for fractures of the distal humerus based on principles that enhance fixation in the distal fragments and provide compression at the supracondylar level.¹^–⁴ The key to the stability achieved with this fixation construct is that it combines the features and stability of an arch while locking the two columns of the distal humerus together.

Background

The critical concept being presented here is the idea that stability of the distal humerus is achieved by the creation of an architectural structure. The bone fragments rely for stability on their integration with the structure, rather than on fixation by screw threads. The concept is borrowed from modern architecture and the application of civil engineering principles to surgery. The interdigitation of screws within the distal segment rigidly attaches the articular fragments to the shaft by linking the two columns together. This permits stability to be achieved in such cases as low transcondylar (Fig. 17.1) or severely comminuted (Fig. 17.2) fractures.

Figure 17.1 Low supraintercondylar fractures through osteopenic bone (A, B) require placement of the plates distal enough to allow secure fixation. Excellent stability can still be obtained with the technique of parallel plating, employing a medial plate that is contoured around the epicondyle onto the medial side of the trochlea along with a lateral plate (C, D).

Figure 17.2 A severely comminuted fracture (A, B) that healed uneventfully after open reduction and internal fixation. (C, D) Fine threaded K-wires, fully embedded in the bone, were used to assemble the articular fragments, just as dowels are used when pieces of wood are glued together to make furniture.

The construct has features of an arch, in which two columns are anchored at their base (on the shaft of the humerus). Two modern architecture columns are linked together at the top (long screws from the plates on each side interdigitating within the articular segment). The interdigitation is best achieved by contact between the screws. However, multiple screws separated by small gaps within the bone will function as a ‘rebar’ construct (steel rods inside concrete). Fixation of the bone fragments is thus reliant not on screw purchase in the bone but on the stability of the hardware framework, in just the same way that a modern building derives its stability from the gridwork of steel assembled and bolted or welded together inside its walls and columns.

Presentation, investigation and treatment options

Patients with fractures of the distal humerus typically present after a fall or high-energy polytrauma. Comminution is related to the energy involved in the trauma or the degree of osteopenia. In addition to plain X-rays, a CT scan with 3-D reconstruction is invaluable in understanding the fracture patterns and planning the fixation.

Surgical techniques

Exposure

I prefer to perform this operation with the patient in the supine position. If assistance is limited, the lateral decubitus position with the arm over a bolster or arm holder may be easier. A sterile tourniquet is inflated only for dissection of the ulnar nerve, which is transposed anteriorly. An olecranon osteotomy provides the greatest exposure and is recommended in the setting of intra-articular comminution. The TRAP (triceps-reflecting anconeus pedicle) approach provides adequate exposure for a surgeon experienced with the technique.⁵ This involves combining the Bryan–Morrey and modified Kocher approaches to reflect the triceps in continuity with the anconeus.

Principle-based fixation technique

Stability is optimized by achieving eight technical objectives derived from the principles of (1) maximizing fixation in the distal fragments and (2) ensuring that all fixation in the distal segment contributes to stability at the supracondylar level. Six of these objectives concern the screws in the distal fragments and two concern the plates (Fig. 17.3).

Figure 17.3 The technical objectives described in this paper are illustrated. The screws in the distal fragments interlock, providing additional stability to the construct by ‘closing the arch’. Interlocking is best achieved by contact between the screws. The combination of multiple screws criss-crossing in close proximity with bone between them gives a ‘rebar’ (reinforced concrete) type structure.

From Sanchez-Sotelo J, Torchia ME, O’Driscoll SW. Complex distal humeral fractures: internal fixation with a principle-based parallel-plate technique. Surgical technique by investigation performed at the Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN. The original scientific article in which the surgical technique was presented was published in J Bone Joint Surg 2007; 89-A:961–969. Used with permission of Mayo Foundation for Medical Education and Research. All rights reserved.

Summary Box 17.1 Technical objective checklist

Concerning screws in the distal fragments (articular segment):

1. Each screw should pass through a plate.

2. Each screw should engage a fragment on the opposite side that is also fixed by a plate.

3. An adequate number of screws should be placed in the distal fragments.

4. Each screw should be as long as possible.

5. Each screw should engage as many articular fragments as possible.

6. The screws should lock together by interdigitation, thereby creating a fixed-angle structure and linking the columns together.

Concerning the plates used for fixation:

7. Plates should be applied such that compression is achieved at the supracondylar level for both columns.

8. Plates used must be strong enough and stiff enough to resist breaking or bending before union occurs at the supracondylar level.

All eight of these objectives are achieved with the technique of ‘parallel plating’. Each plate is actually rotated posteriorly slightly out of the sagittal plane such that the angle between them is often in the range of 150–160°. This orientation permits insertion of at least four long screws completely through the distal fragments from one side to the other. These screws interdigitate, thereby creating a fixed-angle structure and greatly increasing stability of the construct. Contact between screws enhances the locking together of the two columns. Pre-contoured plates that fit the geometry of the distal humerus are available. The specific steps of the surgical technique are detailed below.

Step 1: articular surface reduction (Fig. 17.4)

The first step is articular surface reduction. The proximal ulna and radial head can be used as a template for the reconstruction of the distal humerus. Large articular fragments are provisionally fixed with smooth K-wires (Fig. 17.4). In cases with extensive comminution, fine threaded wires (1 mm) are used, then cut off and left in and used as ‘dowels’. It is necessary that these wires be placed close to the subchondral level, so as not to interfere with the passage of screws from the plates into the distal fragments. No screws are placed in the distal fragments until the plates are applied.

Figure 17.4 Step 1: articular reduction. The articular fragments, which tend to be rotated towards each other in the axial plane, are reduced anatomically and provisionally held with 0.035-inch or 0.045-inch smooth K-wires. It is essential that the wires be placed close to the subchondral level, to avoid interference with later screw placement, and away from where the plates will be placed on the lateral and medial columns. One or two strategically placed pins can be used to provisionally hold the distal fragments aligned with the shaft.

From Sanchez-Sotelo J, Torchia ME, O’Driscoll SW. Complex distal humeral fractures: internal fixation with a principle-based parallel-plate technique. Surgical technique by investigation performed at the Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN. The original scientific article in which the surgical technique was presented was published in JBJS 2007; 89-A:961–969. Used with permission of Mayo Foundation for Medical Education and Research. All rights reserved.

The articular surface of the distal humerus should be reconstructed anatomically unless bone is missing. In the event of absent bone, two important principles should be taken into consideration. First, the anterior aspect of the distal humerus is the critical region that needs to be restored in order to have a functional joint; reconstruction of the posterior articular surface of the distal humerus is less critical. Secondly, stability of the articulation requires the presence of the medial trochlea in combination with either the lateral half of the trochlea or the capitellum.

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