Fractures of the Distal Humerus: Plating Techniques

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Chapter 17 Fractures of the Distal Humerus

Plating Techniques

Shawn W. O’Driscoll

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.

Step 2: plate placement and provisional fixation (Fig. 17.5)

The next step is to choose medial and lateral pre-contoured plates and apply them provisionally according to the following steps:

1. Two smooth Steinmann pins (2.0–2.5 mm) are introduced at the medial and lateral epicondyles through holes in the plates while they are held accurately against the bone. These pins are left in place until after step 4 (below). 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.

2. The appropriate reduction of the distal fragments to the humeral shaft at the supracondylar level is confirmed.

3. One cortical screw is loosely introduced into a slotted hole to secure each plate in place; the use of slotted holes facilitates later adjustments in plate position.

Figure 17.5 Step 2: plate application and provisional fixation. Medial and lateral pre-contoured plates are placed and held apposed to the distal humerus, while one smooth 2 or 2.5 mm Steinmann pin is inserted through hole 2 (numbered from distal to proximal) of each plate, through the epicondyles, and across the distal fragments, to maintain provisional fixation of the plates to the distal fragments. A screw is placed in the slotted hole (5) of each plate, but not fully tightened, leaving some freedom for the plate to move proximally later during compression. Because the undersurface of each plate is tubular in the metaphyseal and diaphyseal regions, the screw in the slotted hole only needs to be tightened slightly to provide excellent provisional fixation of the entire distal humerus.

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.

Step 3: articular fixation (Fig. 17.6)

Once the plates are provisionally applied, medial and lateral screws are introduced distally to provide stable fixation of the intra-articular fragments and rigid anchorage to the plates:

1. Two distal screws, one medial and one lateral, are inserted using a targeted drill guide. As stated above, the screws should be as long as possible, pass through as many fragments as possible and engage in the opposite column. Prior to screw insertion, a large bone clamp is used to compress the intra-articular fracture lines unless there is a gap in the articular surface. This ensures interfragmentary compression without the need for lag screws.

Figure 17.6 Step 3: distal fixation. Screws are inserted through hole 1 of the lateral plate and across the distal articular fragments from lateral to medial, and tightened. This step is repeated on the medial side, using hole 3. In young patients, 3.5 mm cortical screws are used (to prevent breakage), while long 2.7 mm screws are used in patients with osteoporotic bone. The distal screws should be as long as possible, passing through as many fragments as possible, and engaging the condyle or epicondyle of the opposite column.

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.

Step 4: supracondylar compression (Fig. 17.7)

The plates are then fixed proximally under maximum compression at the supracondylar level:

1. The slotted proximal screw on one side is backed out and a large bone clamp is applied distally on that side and proximally on the opposite cortex to eccentrically load the supracondylar region. A second proximal screw is inserted through the plate in compression mode and then the screw in the slotted is hole retightened. Care should be taken not to change the varus–valgus or rotational alignment of the articular surface when the bone clamps are applied.

2. The same steps are followed on the opposite side. Following this step the fixation should be quite stable.

3. The remaining diaphyseal screws are then introduced, providing additional compression as a result of the under-contoured plates being pulled down to the underlying bone. To avoid having the screws strip the bone, this last step is best performed by squeezing the plates against the bone with a large clamp rather than relying on the screws to deform the plates.

Figure 17.7 Step 4: supracondylar compression. (A) Using a large tenaculum to provide interfragmentary compression across the fracture at the supracondylar level, the lateral column is fixed first. A screw is placed in dynamic compression mode (inset) in hole 4 of the lateral plate. Tightening it further enhances interfragmentary compression at the supracondylar level (converging arrows) to the point of causing some distraction at the medial supracondylar ridge (diverging arrows). (B) The medial column is then compressed in a similar manner using the large tenaculum and a screw is inserted in the medial plate in dynamic compression mode. If the plates are slightly under-contoured, they can be compressed against the metaphysis with a large bone clamp, giving further supracondylar compression.

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.

Step 5: final fixation (Fig. 17.8)

The pins are removed and the remainder of the screws inserted. While different locking plates are available, the author prefer the use of variable angle locking screws for the distal segment to prevent the problem of incorrect screw positioning due to the fixed angles predetermined by plate design. With the use of locking screws, fewer screws are likely to be necessary and I routinely place four locking screws (two from each side) in the distal segment. The intraoperative elbow motion should be full unless significant swelling has already developed. One deep and one subcutaneous drain are placed during the closure. The skin should be closed with staples or interrupted sutures.

Figure 17.8 Step 5: final screw insertion. The smooth Steinmann pins are all removed and the remainder of the screws inserted. The distal screws interdigitate for maximum fixation in the distal articular fragments (as described in Fig. 3).

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.

Dealing with metaphyseal bone loss

Adequate bony contact with interfragmentary compression in the supracondylar region is necessary to ensure the stability of the construct and eventual fracture union. If metaphyseal bone loss or comminution precludes an anatomical reconstruction with satisfactory bony contact, the humerus can be shortened at the distal end of the shaft. Correct alignment and geometry of the distal humerus must be confirmed. The distal segment is translated anteriorly to create a pseudo-’fossa’ for the radial head and coronoid. The shaft is burred out posteriorly to recreate an olecranon fossa. I refer to this alternative reconstructive technique as supracondylar shortening (Fig. 17.9). This technique is especially useful in cases of combined soft tissue and bone loss. Shortening by 1 cm or less has only a slight effect on triceps strength in terminal extension,⁶ and in cases of severe soft tissue and bone loss up to 2 cm of shortening can be tolerated without serious disturbance of elbow biomechanics.⁶

Figure 17.9 In cases of supracondylar bone loss, and in some cases of severe comminution, anatomical placement of the distal humerus with respect to the shaft would leave a large structural defect in one or other column, and the only point contact in the other. In such cases when structural bone graft is not an option, a supracondylar shortening osteotomy can be performed. (A) This involves reshaping the distal end of the shaft (dark lines) (never the articular segments) to enhance contact between the distal articular segment and the shaft. Usually, only a small amount of bone is resected from the distal end of the shaft, and sometimes from one side of it as well (for side-to-side apposition and compression). (B, C) The limb is shortened through the fracture site to permit interfragmentary compression between the trochlea and the distal shaft, between the capitellum and the distal shaft, and side-to-side on one or both sides. Once these surfaces have been compressed and fixed with the plates, stability is strong enough to permit immediate motion and rehabilitation. It is acceptable to translate the distal segment medially or laterally, and also slightly anteriorly, provided that rotational and valgus alignment is maintained. (D–G) Preoperative and most recent radiographs of a severe distal humerus fracture with substantial bone loss that was treated with shortening. (H, I) Elbow range of motion at most recent follow-up was 0–150°.

A, B, C 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.

Rehabilitation

Immediately after wound closure the elbow is placed in a bulky non-compressive Jones dressing with an anterior plaster slab to maintain full extension. The upper extremity is kept elevated except for several minutes each hour, when it is let down to ensure adequate perfusion. The initial rehabilitation is planned according to the extent of soft tissue damage. Those fractures with severe soft tissue damage, which include most open fractures and high-energy closed fractures, are immobilized and elevated in elbow extension for 3–7 days postoperatively. Closed fractures without severe swelling or fracture blisters are removed from the Jones dressing after 3 days, and a non-constrictive elastic sleeve is applied over an absorbent dressing placed on the wound. A physical therapy programme including active and passive motion is then initiated. All patients are permitted active use of the hand and instructed not to lift (or push or pull) anything heavier than a glass of water or a telephone receiver for the first 6 weeks. No form of external protection, such as a cast or brace, is used.

If postoperative motion fails to progress as expected, a programme of patient-adjusted static splinting is instituted as soon as the soft tissues are healed. The torque across the elbow applied with such a patient-adjusted splint is low enough to cause discomfort but not pain, and therefore not of concern with regard to the security of the fracture fixation.

Outcome

Recent reports document our experience with this technique for complex distal humerus fractures.^7,⁸ Thirty-four consecutive complex distal humeral fractures were fixed with two parallel plates applied (medially and laterally) in approximately the sagittal plane. Twenty-six fractures were AO type C3 and 14 were open. Thirty-two fractures were followed for a mean of 2 years.

Neither hardware failure nor fracture displacement occurred in any patient. Union of 31 of the 32 fractures was achieved primarily. Five patients underwent additional surgery to treat elbow stiffness. There was one deep infection that resolved without hardware removal and did not impede union. At the time of the most recent follow-up, 28 elbows were either not painful or only mildly painful, and the mean flexion–extension arc was 99°. The mean Mayo Elbow Performance Score (MEPS) was 85 points. The result was graded as excellent for 11 elbows, good for 16, fair for 2, and poor for 3.