INTRODUCTION

By definition, a dynamic hinged external fixation allows for an axis of rotation to provide elbow stability and motion following trauma or reconstruction.³⁰ With a properly constructed device, the ulna may be separated or distracted from the humerus and still allow physiologic flexion and extension. The mechanics and anatomic landmarks for the application of several fixator devices have been well defined.^6,20,28 The axis of rotation of the distal humerus passes through the tubercle of origin of the lateral collateral ligament and through the anteroinferior aspect of the medial epicondyle (Fig. 33-1). Replication of the axis of rotation is essential to avoid pin loosening, persistent stiffness, or instability. In cadaver models, 5 mm of translation or 5 degrees of angulation results in a fourfold increase in resistance to elbow flexion.¹⁵

FIGURE 33-1 On the medial side, placement of the axis pin is at the anteroinferior aspect of the medial epicondyle. On the lateral side, the center of rotation is at the tubercle of the lateral epicondyle, which is at the center of the projection of the curvature of the capitellum.

INDICATIONS

External fixation allows for flexion of the elbow to prevent contracture while still maintaining joint space and appropriate coronal alignment (Fig. 33-2).¹⁸ The hinged fixator, when properly applied, maintains a reduced and balanced ulnohumeral joint during motion, thereby protecting repaired or reconstructed collateral ligaments. In trauma, fixators may be used to protect operative fixation of unstable fractures and ligament repair in cases of persistent postoperative instability and for longstanding elbow dislocation or recurrent instability.⁹ In reconstruction of the elbow, hinged fixators can also be used in the treatment of instability, following ligamentous repair, or with interposition arthroplasty.^3,19

FIGURE 33-2 An articulated external fixator (1) allows flexion motion, (2) protects the ligaments from varus and valgus stress, and (3) separates the joint.

Although goals of treatment may be attained with relatively simple designs, greater flexibility and broader utility have been introduced by Hotchkiss with a more complex fixation. Although several designs are currently available (Fig. 33-3), only the Mayo dynamic joint distractor (DJD)¹⁹ and the Hotchkiss Compass Hinge¹² are discussed in this chapter because they represent the spectrum from simple to complex.

FIGURE 33-3 A variety of articulated external fixators are currently available. Note: All are based on identity of the axis of rotation with variable means of skeletal attachment and distraction. Illustrated here in increasing order of complexity: DJD II (Stryker, Kalamazoo, MI) (A), Orthofix Inc. (McKinney, Texas) (B), OptiROM (EBI, Parsipanny, New Jersey) (C); and Compass (Smith & Nephew, Mississauga, Ontario, Canada) (D).

TRAUMA

In many traumatic circumstances, the goal is to “neutralize” the forces across the joint while elbow motion is maintained. The fixator can be applied acutely as an adjunct to operative repair or as a secondary measure in case of reduction failure. The specific indications for dynamic external fixators of the elbow in acute trauma include the following: (1) instability, (2) articular injury, and (3) residual or recurrent subluxation.

Instability

Elbow dislocation with extensive soft tissue injury results in gross instability, even after reduction or repair of involved structures.⁵ Adjunctive management of late untreated elbow dislocations involve the use of an external fixator.⁹

Articular Injury (Fracture-Dislocation)

This category includes instability with fractures of the radial head,^17,21 some olecranon fractures (Mayo type III)¹⁶ as well as Regan-Morrey type II and III coronoid fractures.^13,23 Use of a hinged fixator for complex, unstable distal humerus fractures has also been described.⁷ Open fixation is the primary treatment modality. When gross instability persists or when fixation is deemed vulnerable, an external fixator can be added to allow for immediate postoperative motion and neutralization or unloading of the stresses placed on the fracture fixation (Fig. 33-4).

FIGURE 33-4 Fracture-dislocation in 38-year-old radiologist involving the comminution of the coronoid. Anteroposterior (A), lateral (B). After fixation with screws and a buttress plate the elbow was stabilized and neutralized with the DJD external fixator. Note position of the pins referable to the intercondylar distance. C, Lateral projection with external fixator. Note replication of axis of rotation by the fixator (D). At 8 weeks the patient has virtually extension (E) and full flexion (F) and has returned to work.

Residual or Recurrent Subluxation

Residual or recurrent subluxation after simple or complex fracture-dislocation is the third indication for use of a fixator.²⁴ In this setting, percutaneous fixator application can assist in reducing a subluxated joint without having to revert to an open procedure. Maintenance of the device allows for early motion with minimal risk of frank redislocation or continued subluxation. The added stability facilitates proper healing of the capsule and soft tissue restraints.

RECONSTRUCTION

The same basic goals obtain for the use of the fixator after reconstructive interventions.

Ankylosis

When arthrolysis for the post-traumatic joint stiffness is carried out, release of the collateral ligament is sometimes necessary, as well as excision of capsular and bone restraints.^8,19 These releases can result in instability. Application of the device protects the repaired collateral ligaments after the arthrolysis while allowing immediate motion of the stabilized concentric joint.

Interposition Arthroplasty

At least one collateral ligament must be released for exposure.³ Hence, the goals in this setting are as follows:

1. To separate the joint surfaces, protecting the interposed tissue from compression and shear forces while it heals to the humerus.

2. To provide motion during the healing phase and prevent contracture.

3. To allow the released or reconstructed ligament to heal without tension (Fig. 33-5).

FIGURE 33-5 A patient with post-traumatic ankylosis, subluxation, and arthrosis (A). This was treated with the distraction device and interposition using in this instance fascia lata (B). At 1 year, a satisfactory result was obtained (C).

CONTRAINDICATIONS

SELECTION OF FIXATOR CONFIGURATION

Over the last several years, a number of experiments have been conducted in our laboratory to better understand the function and indications for external fixator configuration. One such assessment demonstrated that compression across the joint with the half-pin lateral application of an external fixator doubles the stiffness of the system in varus load when in extension but had much less effect otherwise. Thus, distraction, one of the recommended applications of the articulated external fixator, does render this system less stable than when the articulation is compressed.²⁷ Of particular importance is the study of Kamineni et al.¹⁰ which released the medial and lateral collateral ligaments and assessed the kinematic pattern with a half-pin laterally applied external fixator. In this experiment, it was demonstrated that both varus and valgus stability was restored even with the half-pin lateral configuration and even with up to 7 N out of plane load applied to the forearm (Fig. 33-6). Rotational stability, however, was not as reliably restored (Fig. 33-7). An additional clinical relevant experiment sought to assess the sensitivity of pin placement approximating the axis of rotation. It has been shown that increased energy is needed to move the elbow if a nonoptimum application of the articulated external fixator occurs.¹⁵ A subsequent assessment in our laboratory demonstrated that the nonoptimum placement of an external fixator, however, did not alter the kinematics as much as had been anticipated (Fig. 33-8). Based on these data, it was concluded that a slight proximal placement of the axis of the external fixator actually enhances the rigidity of the elbow in a manner that would favor reconstruction of the lateral ulnar collateral ligament. Thus, there may be instances in which slight nonanatomic axis placement is clinically acceptable.²

FIGURE 33-6 Analysis of varus/valgus stability in a normal elbow and following medial and lateral collateral ligament disruption. Note that half-pin configuration applied laterally restores stability even when both medial and lateral collateral ligaments have been disrupted and with both varus and valgus loading conditions.

(After Kamineni, S., Hirahara, H., Neale, P., O’Driscoll, S. W., An, K-N., and Morrey, B. F.: Effectiveness of the lateral unilateral dynamic external fixator after elbow ligament injury. J. Bone Joint Surg. Am. 89:1802, 2007.) (With permission, Mayo Foundation.)

FIGURE 33-7 Unlike the varus/valgus stability, rotational stability is not perfectly restored with the half-pin configuration after both collateral ligaments have been disrupted.

(With permission, Mayo Foundation.)

FIGURE 33-8 If the center of rotation is not accurately defined, the kinematic pattern of the elbow changes (A). Note, however, that these changes are relatively slight for all variations: anterior (B), posterior (C), proximal (D), and distal (E). The baseline, 0, represents normal kinematics.

Hence, based on these experiments, our current practice is to employ the lateral half-pin application of the DJD II in virtually all clinical settings in which the fixator is believed to be necessary.

TECHNIQUE

MAYO DYNAMIC JOINT DISTRACTOR

Patient Positioning

The patient is placed in the position required for proper treatment of the primary pathologic condition. The distraction device itself may be applied with the patient in the prone, supine, or lateral decubitus position. In the practice of one of us (B.F.M.), the supine position is favored for most circumstances.

Author’s Surgical Technique

The patient is supine with a sandbag under the scapula, and a nonsterile tourniquet is applied. The arm is draped free and brought across the chest. In most cases of trauma or reconstruction, a posterior skin incision is used and the elbow joint is exposed either medially or laterally according to the pathologic condition being addressed.

If the joint is to be altered or the joint is badly distorted, an extensive exposure is required, and the lateral collateral ligament is typically released from its origin at the lateral condyle. In this instance the ligament must be carefully repaired or reconstructed. Furthermore, when the condition involves the joint surface that requires an extensive dissection, identification and protection of the ulnar nerve is necessary. This is usually accomplished through a posterior skin incision.

Applying the DJD II External Fixator

Once the elbow has been exposed and the pathologic condition addressed including collateral ligament repair/reconstruction, the external fixator is applied. Several possible configurations are available and are used depending on the lesion and surgeon preference (Fig. 33-9). As noted earlier, we employ the lateral half-pin configuration almost exclusively today.

FIGURE 33-9 Several configurations may be employed with the DJD II fixator, including half-pin or transfixing pin constructs.

AXIS IDENTIFICATION

The essential landmarks of the flexion axis are identified. On the lateral aspect of the capitellum, a tubercle is present at the site of origin of the lateral collateral ligament, which represents the geometric center of curvature of the capitellum (Fig. 33-10).

FIGURE 33-10 The axis of rotation is identified at the lateral tubercle which is the projected center of the curvature of the capitellum.

Note: If this anatomic feature has been altered by pathology, then the center of curvature of the ulnohumeral joint or reconstructed joint is identified as the axis of rotation. Although not commonly repaired, fluoroscopy may be employed if there is concern about axis stylus placement.

On the medial aspect of the distal humerus, the axis of rotation lies just anterior and inferior to the medial epicondyle. This corresponds to the center of curvature of the medial contour of the trochlea and is the locus of the humeral origin of the medial ulnar collateral ligament (Fig. 33-11).

FIGURE 33-11 Medially, the axis site is defined as the anterior/inferior aspect of the medial epicondyle, which is at the geometric center of the trochlea.

AXIS STYLUS

1. The pointed tip of the humeral axis target guide is placed on the medial side, with the cannulated stylus guide on the lateral side. The reference stylus is tapped in place with a mallet through to lateral cannula of the target device (Fig. 33-12).

2. The DJD II frame is placed on the reference pin and aligns with the anterior humeral cortex (Fig. 33-13).

FIGURE 33-12 The axis is identified by a target guide, which is then applied with the alignment guide at the anterior/inferior aspect of the medial epicondyle. The stylus is tapped into place to replicate the axis of rotation. Note the smooth pin avoids entry to any reconstruction that may have been performed.

FIGURE 33-13 The external fixator is placed over the stylus, which replicates the axis of rotation. Note the side bar is aligned with the anterior cortex of the humerus.

HUMERAL PIN INSERTION

3. The interepicondylar width defines a safe location for placement of the proximal humeral pin. The maximum distance from the reference stylus should not exceed the epicondylar dimension “D” (Fig. 33-14).

4. A cannulated trochar is inserted through the pin guide to engage the lateral humeral cortex (Fig. 33-15).

5. The proximal humeral smooth or self-drilling/self-tapping Apex 4-mm (or 3-mm for small bones) pin is advanced through the lateral cortex of the humerus and penetrates the medial cortex through a trochar, which is placed through a pin guide.

6. The proximal pin is fixed to the humeral rod with a Hoffmann II Compact pin-to-rod coupling (Fig. 33-16). Make a second stab incision and place the pin guide on the humeral rod; the cannulated trochar is placed through the pin guide.

7. The second 4-mm (or 3-mm) self-drilling/self-tapping Apex pin is now inserted more distally through the pin guide and fixed to the humeral rod. Note: The humeral pins need not be parallel. The distal pin is fixed to the humeral rod with a Hoffmann II Compact pin-to-rod coupling, which is then tightened using a Hoffmann II Compact wrench. The pin guide is then removed.

8. The axis of the fixator is now defined and rigidly fixed. The stylus pin is removed with a drill or pliers.

FIGURE 33-14 The proximal-most pin is defined by the so-called safe zone D. If D represents the dimensions from the medial and the lateral epicondyle, the radial nerve is 40% proximal to this distance. Hence, the distance “D” is a safe site for inserting the proximal pin.

FIGURE 33-15 A cannula is inserted through the pin guide and protects the soft tissue with the placement of the threaded pin.

FIGURE 33-16 The threaded half-pins have been inserted and are attached to the external fixation with the universal coupler. The stylus pin is removed.

Ulnar Pin Insertion

9. The 3-mm diameter pin is recommended for the ulna. Place the 3-mm pin guide over the ulnar rod, and insert the 3-mm cannulated trochar through the pin guide and identify the lateral ulnar cortex (Fig. 33-17).

10. The distal ulnar 3-mm self-drilling/self-tapping Apex pin is inserted into the lateral cortex through the trochar and through the pin guide and pierces the medial ulnar cortex. The distal pin is fixed to the ulnar rod with a Hoffmann II Compact pin-to-rod coupling.

11. The second ulnar pin is placed and secured in a similar fashion. Note: As with the humerus, the pins do not necessarily need to be parallel. If a different pin insertion angle is required to access a more adequate pin insertion area, slightly rotate the pin guide over the ulnar rod until such a pin insertion area can be reached. By providing proper pin-rod distance, the system allows an independent pin placement. The trochar and pin guide is then removed.

FIGURE 33-17 After the stylus pin has been removed the trochar is placed through the ulnar pin guide. The ulnar pin is then placed through the trochlea and pierces the medial cortex of the ulna.

DISTRACTION

12. If distraction is desired, the amount of separation is determined by the calibrations on the distraction unit (Fig. 33-18). Typically 2 to 3 mm of distraction is sufficient to accomplish the goals of the procedure.

13. Skin closure is usually deferred until the distraction is applied.

FIGURE 33-18 Once the ulnar pins have been attached the desired distraction may be simply introduced through the distracting mechanism.

Percutaneous Application

For some acute or subacute fractures in which the elbow is unstable due to coronoid deficiency, there is a tendency for the ulna to sublux posteriorly. In these cases, the dynamic joint distractor may sometimes be applied percutaneously under fluoroscopy to neutralize fracture displacement forces (Figs. 33-19 and 33-20). Full motion may be achieved by this slight asymmetric distraction, but a flexion arc of 60 to 90 degrees of motion is usually attainable and this is considered adequate given the specific goals of this application.

FIGURE 33-19 Percutaneous application may be carried out. This is done by the use of fluoroscopic control. The key is to identify the axis of rotation. The stylus pin is applied percutaneously to replicate the axis of rotation.

FIGURE 33-20 In a manner similar to the open condition (see Fig. 33-14), the key is to place the proximal pin at a distance “D” from the axis pin, which is a safe distance from the radial nerve. The use of the trochar further minimizes the likelihood of injury to the radial nerve. The pins are placed distally in the ulna to avoid the plate.

THE COMPASS HINGE

Frame Assembly

The frame should be prebuilt to confirm that proper ring size has been selected. In most adults, the 150-mm ring size is usually the best fit. It is important that the geared component is always medial, with the knob facing posterior.

When the frame has been assembled and appropriately adjusted, it should slide along the axis pin without significant impingement or resistance (Fig. 33-21). If there is resistance, the components are probably out of alignment. The clinician should make sure to allow for swelling in the postoperative period, allowing at least 2 cm of clearance from the skin to the hinge block at the time of surgery.

FIGURE 33-21 Preassemble the frame so that the alignment of the axis elements freely slide on a 4-mm pin.

(With permission, Smith & Nephew, Inc.)

Patient Positioning

For release of contracture and removal of heterotopic bone, the patient should be placed in the supine position, with the arm on a radiolucent hand table. If the patient first requires a more extensive exposure of the distal humerus for fracture or reconstructive work, it may be useful to begin the operation with the arm over the chest when using one of the more standard posterior approaches to the elbow, either olecranon ostectomy or a triceps sparing exposure (Bryan-Morrey). In cases of gross instability, the prone position can be used, with the added benefit that gravity in this position tends to reduce the joint during hinge placement and operative ligament repair or reconstruction. However, exposure of the coronoid is difficult in the prone position.

Axis Pin Placement

As with the dynamic joint distractor, a single temporary axis pin is placed across the joint, or two half-pins can be inserted, one from the medial and the other from the lateral aspect. The alignment of the axis is crucial. It is important to take the time necessary to achieve perfect placement of this pin for alignment of the Compass Hinge at the elbow. Both an anteroposterior and lateral radiograph should be viewed to ensure adequate placement. Once the two pins are coincident, entering at their respective centers of rotation, the frame should still be easy to slide from medial to lateral, back and forth, before securing the axis pin from the medial side (Fig. 33-22).

FIGURE 33-22 Once the axis pin has been inserted, the preconstructed frame should slide freely medial to lateral on the axis pin.

(With permission, Smith & Nephew, Inc.)

Humeral Pin Placement

The principle is to secure the humerus in two planes, without impaling any of the major muscle-tendon units or jeopardizing any neurovascular structures. If there is internal fixation present, the pin placement can be adjusted to avoid the plates by customizing the frame. In general, two 5-mm half-pins, medial and lateral, are required. In larger elbows, or in cases in which internal fixation precludes use of the described sites, a third humeral pin may be used, usually placed laterally, superior to the spiral groove.

The medial pin is usually placed first through a two-hole Rancho cube guide on the undersurface of the upper ring. Both cortices should be engaged.

The lateral pin is usually placed using a two-hole post and a single-hole Rancho cube. The lateral flare of the humerus is used for placement. The drill guide rests on the lateral supracondylar ridge, directed anterior and distally. The radial nerve, at this level, is anterior to the pin (Fig. 33-23). Humeral fixation and alignment of the axis of the hinge must be achieved before fixation of the ulna.

FIGURE 33-23 The correct rotatory orientation of the ring referable to the humerus is perpendicular to the long axis of the humerus. The half-pins are inserted using the Rancho system through the alignment blocks, securing first the humerus, followed by the ulnar components.

(With permission, Smith & Nephew, Inc.)

Placement of Ulnar Fixation

One 5-mm and one or two 4-mm pins are used in the ulna. The more proximal pin (5-mm) provides optimal control of the joint and is placed from the dorsal surface through the coronoid. The smaller (4-mm) pins are used more distally in the ulna, again from the dorsal surface. If the elbow is grossly unstable, it is quite important to reduce the elbow by placing it in approximately 90 degrees of flexion when applying the ulnar fixation. Once the joint is reduced and held in position, the first two proximal ulnar pins can be placed. After this, ranging through flexion and extension and ensuring reduction of the joint is important. If there is a tendency for the elbow to subluxate, then alignment has not been achieved and the bolts must be loosened and reduction achieved (see Fig. 33-23).

Application of Distraction

After the joint has been reduced and all pins applied, distraction can then be applied to the system through the distraction mechanism. Distraction is achieved by turning the bolts located on the ulnar ring fixation blocks (Fig. 33-24). Both sides of the hinge should be distracted an equal amount. Use and extent of distraction should be done at the discretion of the surgeon.

FIGURE 33-24 Distraction is achieved by rotating the bolts under the ulnar ring. Both sides should be distracted an equal amount.

(With permission, Smith & Nephew, Inc.)

Aftercare

For aftercare of the Compass Hinge, passive mobilization is initiated using the gear mechanism. In the early postoperative period, the elbow is incrementally extended to the maximally tolerated position. As swelling subsides over the following days, incremental flexion is initiated. The patient then begins a schedule of maximizing the position of flexion or extension using the gear mechanism on alternating days. The device is usually left on the patient for 4 to 6 weeks.

For the DJD II, the patient is placed in a continuous motion machine for 21/24 hours a day (see Chapter 10).

After reconstructive procedures, the patient returns approximately 3 weeks after dismissal from the hospital, the distraction device is removed, and the elbow is examined under general anesthesia. The arc of motion obtained at surgery is re-established under anesthesia. Care is taken not to forcefully manipulate the elbow, but some sense of the firmness of the end points of motion is determined, because this is believed to have prognostic value. Joint crepitus and stability are also assessed. We have encountered virtually no problems with this assessment.¹

Further evaluation is predicated on the severity of the injury, soft tissue integrity, and stability of the internal fixation. A common program is to see the patient at 1, 3, and 6 weeks.

Splints

For patients treated for arthrolysis, static adjustable splints are employed when the device is removed, usually at about 3 weeks for stiffness and 4 to 6 weeks after fracture (see Chapter 11). The goal is to attain a degree of soft tissue stretch with a constant force allowing the soft tissue to “relax” under the constant pressure. For the first 3 weeks of application, the patient wears one or the other for approximately 20 to 21 hours a day. After 3 weeks, the program is individualized, with the time in the splint decreasing to 10 to 16 hours, but the basic principles continue to be followed. For release of the stiff elbow, splint usage may be required at night and to maintain motion for up to 3 months or occasionally even up to 6 months.

Fixator Removal and Examination Under Anesthesia

If progress is not being achieved with the splints and there is no concern about fracture displacement, additional examination under anesthesia may be performed. If this is to be done, this is accomplished before 3 months. The most recent radiograph should be available to appreciate the specific pathologic lesion being addressed. We have evaluated the effectiveness of 56 “evaluations,” 30 of which occurred at the time of external fixator removal. A mean of 37 degrees improvement in the flexion arc was documented. There were no fractures or any other notable complications.¹

RESULTS

A summary of the literature organized by documented indications is shown in Table 33-1. For most surgeons, the value of these devices is in the management of trauma and its sequelae (Fig. 33-25) (also see Figs. 33-4, 33-19, and 33-20).^16,17 Surgical indications for hinged fixator use include ankylosis or elbow contracture, acute or chronic elbow instability, or arthritis.

FIGURE 33-25 Patient with instability from coronoid and radial head fracture (A). External fixation device applied with half-pins (B). This was well tolerated by the patient (C and D).

Elbows treated for ankylosis or contracture respond well to release, with mean flexion arc gains of 40 to 80 degrees.^19,25 In a series of 26 patients, Morrey initially reported greater patient satisfaction and elbow range of motion following arthrolysis with the use of a hinged external fixator compared with no fixator.¹⁸ A retrospective series of 42 patients reported by Ring et al.,²⁵ however, showed no significant advantage in postoperative range of motion with the use of external fixator and capsular release when compared with capsular release alone for the treatment of elbow contractures. Demographics and injury characteristics were similar between the two groups, but in the latter group, the plan was to specifically use the fixator (Compass) as an adjunct to improving motion.

External fixators have also been described in the treatment of complex instability with approximately 80% patient satisfaction or satisfactory Mayo Elbow Performance scores.^5,16,24,26 Jupiter and Ring report successful results in five out of five patients treated for long-standing unreduced elbow dislocations.⁹ In a complex patient population with joint subluxation and coronoid deficiency, Papandrea et al.²² were not able to demonstrate the value of the external fixator as an adjunct to the complex management in these complex injuries treated at the Mayo Clinic.

For post-traumatic or inflammatory elbow arthritis, the literature contains several reports of external fixators used in conjunction with débridement, capsular release, or interposition arthroplasty.^3,14 A series of 13 patients undergoing fascial interposition arthroplasty in conjunction with distraction by the Dynamic Joint Distractor documented in 54% good or excellent Mayo Elbow Performance (MEP) scores.³ Recently, we reported a series of 57 patients undergoing Achilles tendon interposition arthroplasty, 37 with placement of the Dynamic Joint Distractor II and 20 with no use of a fixator. Only 29% of patients in the external fixator group had good or excellent MEP score.¹⁴ From the 20 patients without the use of an external fixator, 46% had good/excellent results.¹⁴ However, there were strong selection bias to use the fixator in the more difficult cases. Of note, the more unstable elbows were more likely to be placed in an external fixator after operative reconstruction, and instability has independently been shown to be a predictor of poor outcomes following interposition arthroplasty.^3,14 Nonetheless, there was no statistical association between clinical outcomes and use of an external fixator.

The important point is when treating patients with complex problems and instability such as in the treatment of the above-mentioned indications, the outcome is not attributed to the fixator but to the complexity of the injury. This is particularly true for the management of the stiff or unstable joint. We do, however, believe that the hinged external fixator brings added value to interposition arthroplasty for management of intrinsic pathologic conditions and is essential for the effective management of selected cases of complex instability with articular injury.

COMPLICATIONS

This topic has recently been studied by Cheung et al.,⁴ who reviewed the Mayo experience with 100 consecutive applications of 80 DJD II and 20 Compass fixators. The complications documented to be associated with these respective devices are listed in Table 33-2. These include superficial or deep infection, skin irritation, nerve injury, pin loosening, fracture, and pin breakage. There are statistically significant differences in the complication rate, which is greater with the use of the more complicated Compass device.⁴ Difference in the frequency of these complications relate to a number of factors, including the indications for application and possibly from technical difficulties encountered. No reoperations were required in any patient for pain-related problems.

SUMMARY

The external fixator is an important tool in the elbow surgeon’s armamentarium, although its precise role in a variety of pathologic conditions is still being defined. The protective effect and ability to replicate elbow kinematics has been experimentally verified.^2,11 Clinically, the fixator is a useful augment to reconstruction in cases of complex instability and interposition arthroplasty. Several designs of hinged external fixators are currently available, each with strengths and deficits. Although a low rate of significant pin site complications have been reported, meticulous technique and appropriate monitoring of pin sites is essential to achieving safe, successful results from an external fixator.