Current Concepts in Fractures of the Distal Humerus

CHAPTER 22 Current Concepts in Fractures of the Distal Humerus



Shawn W. O’Driscoll



INTRODUCTION


Dramatic changes have occurred in the treatment of elbow fractures in recent years. This is especially true for distal humerus fractures. Although improvements in fracture-specific fixation devices have occurred, the most important advances can be attributed to a principle-based approach to these fractures.


Recovery of painless and satisfactory elbow function after a fracture of the distal humerus requires anatomic reconstruction of the articular surface, restitution of the overall geometry of the distal humerus and stable fixation of the fracture fragments to allow early and full rehabilitation.2,4,5,7–9,14 Although these goals are obvious, the orthopedic community would agree that they may be technically difficult to achieve, especially in the presence of substantial osteoporosis or comminution.14


The techniques proposed by the AO/ASIF group had been standard for fixation of distal humerus fractures in the past.8,14 Their recommended technique included fixation of the articular fragments with screws and column stabilization with two plates at a 90-degree angle to one another.3,8,19 Fracture stability is only as secure as the fixation of the distal fragment to the shaft. Using standard AO/ASIF techniques, different authors have reported unsatisfactory results in 20% to 25% of patients.2,4,5,7–9


Improvements in the treatment of these fractures recently have been predicated on understanding and overcoming the limitations and reasons for failure of previous techniques. When treatment of severe distal humerus fractures fails, it typically is due to either nonunion at the supracondylar level or stiffness resulting from prolonged immobilization that has been used in an attempt to avoid failure of inadequate fixation.14 Either way, the limiting factor is fixation of the distal fragments to the shaft. In an effort to increase the yield of excellent and satisfactory results obtained after fixation of distal humerus fractures and to reproducibly obtain stable fixation in the presence of osteoporosis or comminution, I recommend (and have used for two decades) an alternative philosophy and technique based on principles that maximize fixation in the distal fragments and compression at the supracondylar level.11–13,15,17 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. The stability achieved allows routine commencement of an intensive rehabilitation program postoperatively, including full active motion with no external protection.


The following discussion expands on the general principles of our current approach to these fractures, the specific technical details, the postoperative program, and the potential complications.



PRINCIPLE-BASED FIXATION



PRINCIPLES AND TECHNICAL OBJECTIVES


Before discussing the details of surgical techniques, it is imperative that the treating surgeon understand the principles (Box 22-1) and technical objectives (Box 22-2) that, if followed and achieved respectively, will maximize the likelihood of a successful outcome from treatment of these fractures.



BOX 22-1 Principles of Fracture Fixation Surgery


The principles by which the earlier mentioned goals are achieved, and the technical objectives at the time of surgery for achieving them, are



1. Maximize fixation in the distal fragment.

2. All fixation in distal fragments should contribute to stability between the distal fragments and the shaft.


BOX 22-2 Technical Objective Checklist

































Concerning screws in the distal fragments (articular segment):
image
1. Each screw should pass through a plate.
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2. Each screw should engage a fragment on the opposite side that is also fixed to a plate.
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3. An adequate number of screws should be placed in the distal fragments.
image
4. Each screw should be as long as possible.
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5. Each screw should engage as many articular fragments as possible.
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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:
image
7. Plates should be applied such that compression is achieved at the supracondylar level for both columns.
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8. Plates used must be strong enough and stiff enough to resist breaking or bending before union occurs at the supracondylar level.


EXPOSURE


The operation is performed with the patient in the supine position. A sterile tourniquet is inflated only for dissection of the ulnar nerve, which is transposed anteriorly. The triceps-anconeus reflecting pedicle (TRAP) approach provides adequate exposure for a surgeon experienced with the technique.10 This technique involves combining the Bryan-Morrey and modified Kocher approaches to reflect the triceps in continuity with the anconeus. However, I believe that an olecranon osteotomy provides even greater exposure and is recommended in the setting of intra-articular comminution. The TRAP approach is indicated if total elbow replacement is necessary.



PRINCIPLE-BASED SURGICAL TECHNIQUE


The surgical technique is performed in five steps:


1. Articular reduction

2. Plate application and provisional fixation

3. Distal fixation

4. Supracondylar compression

5. Final fixation

Stability and function are restored by achieving eight technical objectives (see Box 22-2) 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 (see Box 22-1) (Fig. 22-1).


image

FIGURE 22-1 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.


All eight of these objectives are achieved with the technique of what we term parallel plating. The medial plate is placed on the medial aspect of the medial column, and the lateral plate is placed laterally, rather than posteriorly, on the lateral column. Although we refer to them as parallel, 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 to 160 degrees. 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 is intended to enhance the locking together of the two columns. The plates must be contoured to fit the geometry of the distal humerus if precontoured plates are not available, but the latter facilitate anatomic reconstruction.


Interfragmentary compression is obtained between articular fragments as well as at the metaphyseal level through the use of large bone clamps that provide compression during the insertion of the screws attaching the articular segment to the shaft. In the distal fragments, fully threaded screws inserted in this manner provide maximum thread purchase in the distal fragments. Additional compression at the metaphyseal level results from slight undercontouring of the plates and the use of dynamic compression holes in the plates. The specific steps of the surgical technique are detailed below.



STEP 1. ARTICULAR SURFACE REDUCTION


Once the fracture is exposed, the first step is reassembly of the articular surface. The proximal ulna and radial head can be used as a template for the reconstruction of the distal humerus. The articular fragments are provisionally fixed with smooth Kirschner wires (K wires) (Fig. 22-2). In cases with extensive comminution, fine threaded wires (1 to 1.5 mm) are used, then cut off and left in as definitive adjunctive fixation. K wires permit assembly of the joint surface fragments in a manner that is analogous to the use of dowels in furniture making. 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; specifically, no screws are placed in the distal fragments until the plates are applied. The articular fragments are fixed in the following order:


1.a. Anterior trochlea and capitellum

1.b. Medial trochlea

1.c. Posterior fragments

image

FIGURE 22-2 Step 1. Articular reduction. The articular fragments, which tend to be rotated toward each other in the axial plane, are reduced anatomically and provisionally held with 0.035 inches or 0.045 inches smooth Kirchner 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.


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. Second, stability of the articulation requires the presence of the medial trochlea in combination with either the lateral half of the trochlea or the capitellum; thus, the medial trochlea is essential to obtain a stable and well-aligned joint.



STEP 2. PLATE APPLICATION AND PROVISIONAL FIXATION


We routinely use precontoured medial and lateral plates from the Mayo Congruent Elbow Plate System (Acumed, Hillsboro, OR) (Fig. 22-3). The medial plate can be extended to the articular margin in very distal or comminuted fractures and is contoured to the shape of the medial epicondyle. The ulnar nerve must be transposed if this extended plate is used. The distal end placed more posteriorly to prevent impinging on, or cutting into, the common extensor tendon and lateral collateral ligament complex. Both plates should be slightly undercontoured to provide additional compression at the metaphyseal region when applied. The length of the plates is selected so that at least three screws are placed both medially and laterally proximal to the metaphyseal component of the fracture. These plates are designed so that in any combination they will end at different levels to avoid the creation of a stress riser proximally. The plates are then provisionally applied according to the following steps:


1. Two smooth Steinmann pins (2.0 to 2.5 mm) are introduced at the medial and lateral epicondyles through holes in the plates while they are held accurately against the bone; the most commonly used holes are the second one laterally and the third medially. These pins are left in place until after step 4 (see later). The pins create pilot holes for later replacement with screws, are easy to drill around, and do not interfere as much with placement of the two distal screws, as would be the case if they were replaced by screws earlier.

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Aug 28, 2016 | Posted by in ORTHOPEDIC | Comments Off on Current Concepts in Fractures of the Distal Humerus

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