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Hinged Elbow External Fixators: Indications and Uses Abstract Hinged external fixation of the elbow joint can play an important role in managing complicated fracture-dislocations, joint instability after extensive contracture release, and distraction interposition arthroplasty. Application of these devices requires accurate alignment of the fixator axis with the anatomic axis of the elbow. The primary therapeutic goal is to allow joint motion while protecting the healing ligaments. Common complications include pin loosening, injury to adjacent neurovascular structures, cellulitis, and loss of reduction. Although reported data are limited, this technique is a useful adjunct in patients with complex elbow instability. S ince Malgaigne first described external fixation for patellar fractures in 1843, external fixators have evolved from simple devices used exclusively in lower extremity trauma to articulating hinged frames with applications in the upper extremity. Although originally described in the Russian literature in the early 1970s, the first English- language report of a hinged distraction apparatus for the elbow did not appear until 1975. 1 This hinged device was designed to eliminate “excessive friction between the surfaces,” prevent abnormal joint kinematics, and allow the “newly formed joint surfaces to develop correctly.” 1 Volkov and Oganesian 1 treated 28 elbows with the hinged fixator for various indications and reported encouraging results. In the 13 elbows managed with arthroplasty, 7 had final arc of motion of 80° to 120°, 5 had 50° to 70° of motion, and 1 had 40° of motion. In the 11 elbows treated for flexion contracture, 6 had final arc of motion of 70° to 120°, 4 had 50° to 60° of motion, and 1 had 40° of motion. The remaining four patients had a final average arc of motion of 102°. The concept of an articulating fixator about the elbow is based on the normal ulnohumeral kinematics, which approximate a simple hinged joint. 2-4 Recreating the anatomic axis of rotation with a hinged fixator allows concentric ulnohumeral motion while protecting the joint surfaces and periarticular soft tissues from loads that would injure or dis- rupt the healing tissue. The several commercial devices now available that seek to satisfy this requirement differ in design, method of mobiliza- tion, and technique of application. Common Design and Application Features Elbow fixators are categorized as unilateral ormultiplanar. These two types share common design features and are affixed using essentially similar surgical techniques. Advan- Virak Tan, MD, Aaron Daluiski, MD, John Capo, MD, and Robert Hotchkiss, MD Dr. Tan is Associate Professor, Division of Hand and Microsurgery, Department of Orthopaedic Surgery, University of Medicine and Dentistry of New Jersey– The New Jersey Medical School, Newark, NJ. Dr. Daluiski is Assistant Professor, Division of Hand Surgery, Department of Orthopaedic Surgery, The Hospital for Special Surgery, New York, NY. Dr. Capo is Assistant Professor, Division of Hand and Microsurgery, Department of Orthopaedic Surgery, University of Medicine and Dentistry of New Jersey– The New Jersey Medical School. Dr. Hotchkiss is Associate Professor, Division of Hand Surgery, Department of Orthopaedic Surgery, The Hospital for Special Surgery. None of the following authors or the departments with which they are affiliated has received anything of value from or owns stock in a commercial company or institution related directly or indirectly to the subject of this article: Dr. Tan, Dr. Daluiski, and Dr. Capo. Dr. Hotchkiss or the department with which he is affiliated has received royalties from Smith & Nephew. Reprint requests: Dr. Tan, University of Medicine and Dentistry of New Jersey, 90 Bergen Street, DOC 1200, Newark, NJ 07101-1709. J Am Acad Orthop Surg 2005;13:503- 514 Copyright 2005 by the American Academy of Orthopaedic Surgeons. Volume 13, Number 8, December 2005 503 tages of the unilateral frames include (presumably) less ulnar nerve irritation; a lower profile, which is more tolerable to the patient; and ease of application. Advantages of the multiplanar fixators include more rigid skeletal fixation as well as better control of varus/valgus alignment and joint distraction. Application of a hinged elbow external fixator can be demanding. The most critical step is correct placement of the axis pin. To minimize resistance to motion and half- pin loosening, this pin must be colinear with the center of rotation of the elbow joint. Madey et al 5 reported that misalignment of 5° caused a 3.7-fold increase in motion energy; a 10° mismatch yielded a 7.1-fold increase. The anatomic axis of rotation lies at the center of the capitellum and trochlear spool and is usually determined from anatomic landmarks. Medially, this point lies just distal and anterior to the medial epicondyle; laterally, it lies just slightly distal to the lateral epicondyle. The axis pin starting point should be verified with fluoroscopy before advancing into bone. The pin should be slowly advanced and the position confirmed on lateral and anteroposterior radiographic views. The true lateral view should show the pin as a dot within the center of the trochlear spool, while the anteroposterior view should show it traversing paral- lel to the joint, along the normal valgus angulation of the distal humerus (Figure 1). With a unilateral frame, the axis pin is inserted only far enough to ensure proper orientation and stable bone purchase. With a multiplanar frame, a single axis pin is advanced across the distal humerus, or two pins may be placed from both the medial and lateral sides. Care must be taken on the medial side to protect the ulnar nerve during advancement of the axis pin. The external fixator frame is assembled around the axis pin and attached to the skeleton with half pins. These half pins should be placed without impaling any major muscle-tendon units or jeopardizing neurovascular structures. The humeral pins are usually placed first. Lateral pins are more easily placed because of patient positioning. The most proximal lateral pin may lie near the course of the radial nerve, which should be avoided by careful pin placement. Pins placed medially should be inserted through an open incision to protect the ulnar nerve. All half pins should have bicortical purchase. With the elbow concentrically reduced, the fixator frame is attached to the ulna. It is useful to hold the elbow in flexion with the arm in the overhead position to take advantage of gravity to assist in concentric reduction and placement of the ulnar half pins. Depending on the fixator used, the ulnar pins are inserted either in a dorsal-to-volar or in a lateral-to-medial direction. After the pins are inserted into the ulna, the frame is secured to the ulnar pins. With a highly unstable reduction, the joint can be temporarily pinned with a stout Kirschner wire before ulnar pin insertion. After ensuring that all the connec- tions are secure, the axis pin is removed and the elbow is taken through a range of motion (ROM) under fluoroscopy to evaluate for concentric reduction and stability. The half pins should be checked for proper skin clearance, and the ulnar nerve should be sensitive during flexion and extension of the elbow. Fine- tuning of the frame to achieve the de- sired amount of distraction and varus/valgus angulation is done at the conclusion of frame application. Figure 1 Intraoperative fluoroscopic anteroposterior (A) and lateral (B) views of the axis pin position. Hinged Elbow External Fixators 504 Journal of the American Academy of Orthopaedic Surgeons Specific Hinged Fixators Currently, there are four commercially available hinged external fixators for the elbow: Compass Uni- versal Hinge (Smith & Nephew, Memphis, TN), OptiROM Elbow Fixator (EBI, Parsippany, NJ), Ortho- fix Elbow Fixator (Intavent Orthofix Ltd, Berkshire, United Kingdom), and Dynamic Joint Distractor II (Stryker Howmedica Osteonics, Mahwah, NJ) (Table 1). Each specific fixator has unique features, and the choice of fixator is usually based on the surgeon’s familiarity and comfort with the system. The Compass Universal Hinge (Figure 2, A) is a multiplanar fixator that allows incremental passive joint ROM. The frame, which is composed of radiolucent 1/2-in and 5/8-in rings, is assembled before application. The humeral half pins are placed in both medial and lateral multiplanar positions. The ulnohumeral articulation must be concentrically reduced before placing the ulnar pins and attaching the frame. The ulnar pins are inserted from the dorsal surface of the ulna in a dorsal-to-volar direction. The frame has a self-telescoping mechanism to allow a 20° arc of varus/ valgus adjustment. Distraction screws allow joint displacement/ distraction that is independent of the varus/valgus alignment. Addi- tionally, a precision worm gear permits motion within a specified range and can be “ungeared” for active and passive motion or kept locked for incremental gear-driven passive motion. The patient or occupational therapist can easily operate the gear. One disadvantage of the Compass Universal Hinge is that its application can be technically demanding. Additionally, there is less room for adjustment when the frame is placed with the elbow subluxated. Because the frame impinges against the chest wall, patient comfort may be an is- sue. The OptiROM Elbow Fixator (Figure 2, B) is a unilateral frame based on multiple stout adjustable linkages that allow many degrees of freedom. The axis pin is placed from lateral to medial, after which the humeral por tion of the frame may be applied with appropriate half pins. Alternatively , the humeral pins may be placed and secured to the frame before the axis pin is inserted. The Table 1 Commercially Available Hinged Elbow External Fixators Fixator Type Features Advantages Disadvantages Compass Universal Hinge Multiplanar Ilizarov concept Radiolucent arcs with bilateral hinges Varus/valgus control Distraction control Worm gear Frame stability Independent angulation and distraction control Passive gear-driven motion allows for soft-tissue stress/relaxation Steep learning curve Concentric reduction required before fixation to ulna Less patient comfort More exposure needed for medial half pins OptiROM Elbow Fixator Unilateral Multiple adjustable linkages More patient comfort due to unilateral design Flexibility to allow adjustment of frame to elbow axis of rotation Noninvasive technique for axis placement Less frame stability No independent angulation and distraction control Conical half-pin design limits depth adjustment Orthofix Elbow Fixator Unilateral Linked components with central connecting units Low profile Compression-distraction unit can be applied for static progressive ROM Concentric reduction required before fixation to ulna Frame allows less flexibility Extensor mass may be impaled with pin placement Dynamic Joint Distractor II Unilateral/ bilateral Simplified frame construction with integrated hinge Compatible with Hoffman II Compact couplings Ease of application Lowest profile for increased patient comfort Independent half-pin placement Frame stability increased with bilateral application Varus/valgus controlled at pin-to-rod coupling No passive-motion mechanism in the frame Concentric reduction required before fixation to ulna Ulnar pin placement impales the common extensor muscles Virak Tan, MD, et al Volume 13, Number 8, December 2005 505 axis guide ring can be adjusted to lie over the axis pin. The axis ring should slide easily over the guide pin for several centimeters to ensure proper alignment of the frame with the elbow axis of rotation. An addi- tional benefit is that the ulnar half pins can be inserted either from dorsal to volar (preferred by the authors) or lateral to medial and locked to the frame with the elbow in an unreduced position. Ulnohumeral joint reduction can be done with the frame in place and the universal joints tightened to maintain reduction, thus avoiding the sometimes difficult task of placing the ulnar pins while maintaining perfect reduction of the elbow. A new addition to this frame allows static progressive ROM with application of torque through an adjustment screw. The Orthofix Elbow Fixator (Fig- ure 2, C) is similar to the OptiROM. This unilateral frame consists of two linked components (ulnar and humeral) with a central connecting unit. The frame is placed over the axis pin, the humeral pins are placed unicortically from lateral to medial, and the ulnar pins are placed from lateral to medial. A distraction unit can be applied to either the ulnar or humeral link. Additionally, a compression-distraction bar can be attached to the cams of the fixator for static progressive ROM, which can be done by either the patient or the therapist. One disadvantage of this device is less flexibility of the frame; there are only two adjustable linkages, which limits the degrees of freedom. Another disadvantage is impalement of the common extensor muscles resulting from the lateral-to-medial placement of the ulnar pins. The Dynamic Joint Distractor II (Figure 2, D) is based on the same concept as its predecessor, the Mayo Dynamic Joint Distractor. The Figure 2 A, Compass Universal Hinge. (Courtesy of Smith & Nephew, Memphis, TN.) B, OptiROM Elbow Fixator. (Courtesy of EBI, Parisippany, NJ.) C, Orthofix Elbow Fixator. (Courtesy of Intavent Orthofix, Berkshire, UK.) D, Dynamic Joint Distractor II. (Courtesy of Stryker Howmedica Osteonics, Mahwah, NJ.) Hinged Elbow External Fixators 506 Journal of the American Academy of Orthopaedic Surgeons frame can be applied in a unilateral or bilateral configuration. Using a humeral axis guide, the axis pin is placed via open technique on the medial side and percutaneously on the lateral side. The guide clamps, the center points on the medial and lateral sides, and the axis pin are placed through the cannulated guide. The frame is applied over the axis pin, and pin guides are used to place the humeral pins. The half pins are connected to the frame with standard Hoffman II Compact clamps (Stryker Howmed- ica Osteonics). The ulnar pins are placed percutaneously from lateral to medial, which has the disadvantage of impaling the common extensor muscles. The built-in distraction-compression device can be progressively adjusted. Dual medial and lateral frames can be applied for more stability. The advantages of this frame are its low profile and rel- ative ease of application. Complications Although the true incidence of complications is difficult to determine, they are relatively common and should be anticipated. Infection can range from cellulitis around the pin tract to deep-seated sepsis. 1,5-7 In the early phase, when there is only erythema and tenderness around the pin site and the pin is not loose, cellulitis may be treated with oral antibiotics for 10 to 14 days. When there is drainage around the pin despite antibiotic treatment or when the pin is loose, removal with insertion of a new pin or pins in healthy tissue may be necessary. Rarely, osteomy- elitis can develop, in which case the entire fixator must be removed 1,8 and intravenous antibiotics given for 6 weeks. Vigilance and local pin care are the keys to minimizing this complication. Loss of reduction can occur from improper placement of the fixator axis or from hardware failure. 8-11 Pe- riodic radiographic evaluation is mandatory to confirm that the joint remains reduced and the frame is secure. With more vigorous rehabilitation and motion, more stress is placed on the components, which can lead to pin loosening or break- age. Pin replacement may be necessary to maintain alignment between the fixator axis and that of the elbow. Despite awareness that the ulnar nerve is at risk during surgical procedures around the elbow, injury still may occur. 7,9,12 Causes include inju- dicious placement of the axis or medial humeral half pins, over- penetration of lateral humeral half pins, and increased elbow flexion after a contracture release. Ulnar nerve injury can be avoided with precise pin insertion and protection and/or transposition of the ner ve. For laterally based unilateral frames, care must be taken to protect the radial nerve during application of the most proximal pin. 13 With the Com- pass Universal Hinge, the low lateral humeral pin should be placed from posterolateral to anteromedial, staying posterior to the course of the radial nerve. Injury to the posterior interosseous nerve also has been reported. 7,14 In addition to avoiding neurovascular structures, the half pins should be placed without impaling any major muscle-tendon units. Such injury may impede motion or cause pain. 15 Fracture of the ulna during vigorous therapy or as a result of a fall are less commonly reported complications. 11 Using smaller diameter pins for the ulna can help reduce the stress riser effect. When fracture does occur, internal fixation with plating may be necessary. Reflex sympathetic dystrophy also has been reported after hinged fixation 10 and should be treated expeditiously. Indications Instability The elbow is a relatively stable joint because of its bony anatomy and capsuloligamentous complex. However, disruption of these structures can render the joint unstable. Causes of instability include dislocation with medial collateral and ligament tear, coronoid and radial head fractures (the so-called terrible triad), medial collateral ligament injury with concomitant radial head fracture, comminuted olecranon and/or distal humerus fractures, and post- contracture release of a stiff joint. Ulnohumeral instability can be categorized as acute, recurrent, or chronic. Acute instability is present at the time of the initial surgical treatment; recurrent instability is re- ducible, but with persistent instability (after the initial stabilization) in the postoperative period; and chronic instability is late, unreduced dislocation that has become irreducible by closed manipulation. In the setting of unstable elbows, hinged fixators are indicated for persistent acute or recurrent instability despite attempted fracture stabilization and ligament repair; for protecting nonrigid fracture fixation and/or non-secure ligamentous repair during postoperative rehabilitation; and for chronically unreduced dislocation; and acute gross instability that cannot be splinted in concentric reduction in a patient who is unable to tolerate a prolonged surgical procedure (Figure 3). Acute and Recurrent Instability Acute elbow instability encom- passes a spectrum of conditions, ranging from subtle ulnohumeral subluxation to simple dislocation to the terrible triad. Acute subluxation and simple dislocation respond well to cloned reduction followed by non- surgical management with super- vised rehabilitation. At the other end of the spectrum, complex elbow dislocation with associated radial head and coronoid fractures and/or collateral ligament disruption may render the joint very unstable. Under these circumstances, the radial head and Virak Tan, MD, et al Volume 13, Number 8, December 2005 507 coronoid should be repaired, reconstructed, or replaced, and the collateral ligament or ligaments repaired or reconstructed. In some patients, even with osteosynthesis and repair of the ligaments, the elbow may still be unstable because of severe bony and soft-tissue defects. With such injury patterns, ulnohumeral instability may not be immediately evident because the surgeon does not want to test or stress the repair; thus, an im- perfect or unstable reduction may not be detected until the postoperative period. Regardless of the timing, persistent instability that is present either acutely or in the early postoperative period is an indication for a hinged external fixator. The function of the fixator is to maintain concentric reduction of the ulnohumeral joint, protect the bony and/or ligament repair or reconstruction, and allow early postoperative motion. 11,15 For a complex fracture-dislocation of the elbow, a hinged device should be available in the operating room at the time of initial surgery. Careful assessment of the quality of fracture fixation and ligament repair must be done intraoperatively to determine whether the ulnohumeral joint is stable enough to tolerate early postoperative motion. In some settings, the position of maximal instability Figure 3 Closed reduction Acute instability Recurrent instability Acute gross instability; medically unstable* Chronic unreduced dislocation Repair or reconstruct ligament(s) Total elbow arthroplasty Open reduction and/or interposition and/or ligament repair(s) Hinged external fixator Rehabilitation program Associated fractures Salvageable No Yes No Yes YesYes Stable range of motion No No (ie, nonrigid fracture fixation) Stable fixation/ reconstruction achieved Stable range of motion Yes No (ie, nonsecure ligamentous repair) No Yes Stable range of motion Treatment algorithm for complex elbow instability and the potential use of a hinged fixator. * A static external fixator across the elbow also may be appropriate in this situation. Hinged Elbow External Fixators 508 Journal of the American Academy of Orthopaedic Surgeons can be avoided, and the elbow rehabilitation program may proceed with a hinged brace or splinting. When persistent instability through ROM precludes rehabilitation, the hinged fixator should be applied. For recurrent subluxation in the postoperative period, the device can be applied by percutaneous techniques provid- ed that the ulnar nerve is protected. Although no large studies have been done, several authors have reported cautious optimism with use of a hinge for acute and/or recurrent complex instability. McKee et al 10 used hinged fixation to treat complex elbow instability in 16 patients. In two patients, the fixator was applied at the time of the original treatment because the elbow remained unstable after open reduction and internal fixation and soft-tissue reconstruction. The other 14 patients failed conventional treatment; 11 had recurrent dislocation and 3 had recurrent subluxation. 10 In these 14 patients, hinge application was done at a mean of 4.8 weeks (range, 2 to 9 weeks) after the primary treatment. The fixators remained in place for a mean of 8.5 weeks (range, 6 to 11 weeks). On final follow-up 23 months after surgery (range, 14 to 40 months), 15 of 16 elbows had achieved concentric reduction. The mean arc of flexion-extension was 105° (range, 65° to 150°) with pronation of 76° (range, 20° to 90°) and supination of 75° (range, 15° to 90°). Six patients experienced complications, including recurrent subluxation, reflex sympathetic dystrophy, pin tract infection, wound infection, and tran- sient radial nerve palsy. The one recurrent instability occurred in a non- compliant patient who had incorrect placement of the center axis of rotation and early loosening of the humeral pins. Cobb and Morrey 11 reviewed seven patients who had unstable elbow dislocations associated with coronoid fractures. Hinged external fixation was applied acutely in one patient and postoperatively in three patients. (The other three patients underwent “resurfacing” distraction arthroplasty.) At final follow-up (44 months), three of the four patients had a stable elbow, with a flexion- extension arc of 95° and a pronation- supination arc of 115°. One patient had persistent instability and went on to have a total elbow arthroplasty. Ruch and Triepel 12 evaluated a unilateral hinged elbow frame for recurrent instability following fracture-dislocation. Three of eight patients had acute instability and were treated with hinge stabilization for a mean of 43 days (range, 40 to 47 days) because of inability to achieve complete osseous and ligamentous repair. The average postoperative arc of motion was 120° (range, 105° to 130°), with average pronation of 90° and average supination of 67°. The other five patients were treated with an articulated fixator as an “al- ternative to complete osseous and ligamentous reconstruction” for recurrent instability at 6 weeks to 9 months after the initial injury. Mean duration of external fixation was 62 days (range, 54 to 80 days). Their average postoperative arc of motion was 84° (range, 75° to 95°), with average pronation of 68° and average supination of 43°. In another study of a unilateral articulating fixator, von Knoch et al 6 reported on 13 patients, 9 with acute elbow trauma. The average duration of external fixation was 7.6 weeks (range, 3 to 18 weeks). These authors did not stratify the results of the acute traumatic injury from the posttraumatic reconstruction (eg, joint stiffness/contracture, heterotopic ossification, distal humerus nonunion). The 11 patients who were followed had an average arc of motion of 81° (range, 50° to 125°). Complications were confined to five patients who developed pin tract infection, which resolved with oral antibiotics. The hinged fixator is not a pana- cea for complex elbow instability. These injuries are difficult to manage, and patients usually have a less than satisfactory result. Initially , the principles of osteosynthesis with or without collateral ligament repair should be followed. The hinged elbow devices should be used as an adjunct to, not in lieu of, conventional stabilization. The only exception is in the patient with gross elbow instability who cannot medically tolerate a prolonged surgical interven- tion. 15 Because of the instability, closed reduction cannot be obtained and maintained by external splinting. In such patients, an external fixator (either static or hinged) can be used as a primary temporizing device until definitive stabilization can be performed. Chronic Dislocation Morrey 16 described two major types of chronic elbow instability, based on the degree of displacement: subluxation and dislocation. Chron- ic subluxation (ie, posterolateral ro- tatory instability) is more common; of these, the chronic dislocation can be best treated with a hinged fixator. Patients with chronic complete dislocation of the elbow often have had a neglected or irreducible elbow dislocation. 17-19 Neglected dislocation is more commonly seen in patients in underdeveloped countries. However, such instances occur in North America when the dislocation is unrecognized in an unrespon- sive multiply traumatized patient. They also occur when the elbow re- dislocates in a patient who fails to follow up, or in a patient who did not initially seek medical attention. Marked deformity of the elbow can result, with severely limited function caused by pain and restricted motion. 18 Often, there are associated fractures along with the chronic dislocation. 19 Various treatment strategies have been reported for chronic elbow dislocations; however, only open reduction (with or without hinged external fixation) and total elbow replacement are reasonable options. Virak Tan, MD, et al Volume 13, Number 8, December 2005 509 Several investigators have reported satisfactory results with open reduction without distraction of the joint. Billett 18 reported on six unreduced posterior dislocations in which reduction was achieved by open excision of all fibrous tissue and by division of the medial and lateral collateral ligaments before joint reduction. Because of the induced instability required for the reduction, a Kirschner wire was used to temporarily transfix the joint for 2 weeks. Range of motion (flexion and extension) improved postoperatively. One patient who did not have the joint pinned redislocated. Naidoo 19 reported on 23 unreduced posterior dislocations treated with release of the anterior capsule and collateral ligaments as well as temporary trans- fixion of the ulnohumeral joint. Although follow-up was limited because of socioeconomic factors, useful ROM was obtainable even in dislocations older than 3 months and in patients older than age 40 years. Ara- files 17 described open reduction and an intra-articular “cruciate” ligament reconstruction with a free tendon graft in 11 patients with neglected elbow dislocation. This procedure was devised to allow early elbow motion in the flexion-extension plane after the open reduction. At 32-month follow-up, the flexion- extension arc of motion averaged 105°, with a mean valgus-varus lax- ity of 13°. Because open reduction of a chronically unreduced elbow requires ex- tensile release of the contracted soft tissues, including the capsule, collateral ligaments, and possibly the triceps, Morrey 16 advocated reconstruction of the collateral ligaments through bone tunnels and application of a hinged fixator, both to allow immediate motion and to protect the repaired collateral ligaments. In three of four patients, a stable arc of elbow motion >90° was achieved; these patients had mild or no pain. 16 Jupiter and Ring 20 treated unreduced elbow dislocations with hinged external fixation in five patients. Surgery was performed at an average of 11 weeks (range, 6 to 30 weeks) after the original dislocation. The elbow joint was exposed both medially and laterally, but the origin of the flexor-pronator mass was left attached to the medial epicondyle. Adhesions and the entire lateral capsule were resected, after which the ulnohumeral joint was reduced and the hinged fixator applied. At an average of 38 months (range, 12 to 98 months), all patients had stable concentric reduction and a satisfactory Mayo Elbow Performance Index (average score, 89 points). The average arc of flexion was 123°, and all patients had full forearm rotation. In cases of chronic unreduced elbow dislocation, a hinge-distraction device can be useful to maintain ulnohumeral joint reduction without transfixing the joint and to start immediate concentric motion. A hinge- distraction device also allows the joint to unload by distraction and the soft-tissue sleeves to heal in the optimal position for motion. Distraction Interposition Arthroplasty Distraction interposition arthroplasty has been developed from two procedures—distraction and biologic resurfacing of the joint—used to treat incapacitating elbow pain and loss of motion. Volkov and Ogane- sian 1 advocated joint separation while gradually restoring motion through a hinged-distraction device. In their arthroplasty group of patients, in whom preoperative motion was severely limited (arc of motion ranged from 0° to 50°), postoperative motion increased by 70° to 120° in six patients, by 50° to 60° in four patients, and by only 40° in one patient. Nine patients returned to their previous occupations, although three of these remained in pain. Sim- ilarly, Morrey 8 reported on 14 patients who underwent distraction without joint resurfacing for elbow contracture. The average arc of motion increased from 32° (range, 0° to 75°) preoperatively to 99° (range, 70° to 125°) postoperatively. Interposition arthroplasty, in which a biologic material is used to resurface the joint, has had mixed success in the elbow. 21-24 This procedure has been used for posttraumatic or postinfectious ankylosis, hemo- philic arthropathy, and rheumatoid arthritis. 21-24 In 1952, Knight and Van Zandt 24 reported the results of fascia lata interposition arthroplasty in 45 patients with partial or complete elbow ankylosis. At an average follow-up of 14 years, there were 25 good, 10 fair, and 10 poor or failed elbows. In 1976, Froimson et al 23 reported satisfactory results using deep dermal skin interposition arthroplasty in five patients. However, two patients had varus-valgus instability of 20° and 30°, respectively. Ljung et al 22 found that the results of interposition arthroplasty in 35 rheumatoid elbows were good in terms of pain relief but only fair in terms of joint mo- bility and stability. The inconsistent outcome of interposition arthroplasty alone raised questions about the effectiveness of this procedure in patients with arthritic elbows. 22 The addition of joint distraction to interposition arthroplasty (ie, distraction interposition arthroplasty) was done to address concerns of postoperative instability and de- gradation of the interposed tissue when early motion is started. 4,25 Us- ing a hinged external fixator allows for distraction across the joint to minimize shear forces across the interposed tissue. A hinged external fixator also permits immediate postoperative motion. The medial and lateral ligaments remain protected through the postoperative healing period. The surgical procedure, which has been well described, 4,8,25 begins with contracture release using the lateral column and/or medial over- the-top approach. 26 After the release, if visual inspection of the joint surface reveals loss of articular cartilage Hinged Elbow External Fixators 510 Journal of the American Academy of Orthopaedic Surgeons ≥50%, significant intra-ar ticular adhesions causing avulsion of cartilage during motion, or an intra-articular malunion requiring recontouring, then interposition arthroplasty should be performed. 8 The lateral ligament complex is sharply divided from the humerus. If necessary for exposure, the triceps is mobilized as a continuous sleeve from the ulna. Manual distraction applied across the ulnohumeral articulation often provides sufficient exposure to per- form the operation without remov- ing the triceps insertion. The ulnohumeral joint surfaces are then prepared by contouring them into matching surfaces. Bone resection should be sufficient to allow a gap of at least 3 mm. The radial head is re- tained when there is painless forearm rotation. In some cases, the ulnar articular margin for the radial head is removed (ie, “radialization” procedure) to increase forearm motion. 25 Although a variety of interposition materials has been used, autol- ogous fascia lata is usually the graft of choice. A sheet of fascia 5 cm × 12 cm is harvested from the thigh. The fascia is then sutured to the distal end of the humerus with suture an- chors or drill holes through the humerus. Once the interposition graft is in place, the ulnohumeral joint is located, and fluoroscopic views of the joint are taken to verify reduction. Care must be taken not to translate the ulna too far radially. Proper repair or reconstruction with tendon grafts of the lateral ligament complex is then performed. A hinged fixator is applied, and distraction of at least 3 mm is maintained through a full arc of motion. Few reports of the outcome of distraction interposition arthroplasty have been published (Table 2). Many of these results are embedded within larger study cohorts. Although the results are not as reproducible as for patients undergoing total elbow arthroplasty, most patients have im- provement in ROM and moderate to significant pain relief. Distraction interposition arthroplasty likely will become more common as the number of patients with posttraumatic elbow arthropathy in- creases. This procedure is indicated for patients with intra-articular pa- thology who are too young for a total elbow prosthesis. It also is indicated in certain patients with inflammatory arthropathy , and in patients who have experienced trauma or infection. Postoperative Control of Motion Elbow contracture releases, espe- cially revision cases, often require extensive excision of soft tissues and bone structures to regain motion. These structures include the collateral ligaments, heterotopic bone, os- teophytes, and the hypertrophic capsule. Because the goal of surgery is to improve elbow motion, the surgeon should not abandon this goal until full or nearly full motion is obtained on the operating table. In the course of these excisions, the joint may be rendered unstable, 4 requiring the application of hinged fixation to allow controlled motion until the soft tissues heal adequately to provide stability. Posttraumatic contracture, which involves an intrinsic cause, may benefit from distraction interposition arthroplasty. Within the spectrum of contracture is complete ankylosis of the joint (Figures 4 and 5). In a report of 20 elbows (15 patients) that underwent surgical release for this condi- tion, Ring and Jupiter 27 used a hinged device in three patients to treat elbow subluxation or dislocation. The true outcome of these three patients is unknown because the results were not stratified ac- Table 2 Results of Distraction Interposition Arthroplasty Study No. of Patients Mean Follow-up (months) Mean Preoperative Flexion-Extension Arc (range) Mean Postoperative Flexion-Extension Arc (range) Results Morrey 8 6 33 27° (0°-60°) 107° (70°-150°) — Morrey 4 20 — — — 80% satisfactory Cobb and Morrey 11 2 30 38° (35°-40°) 84° (57°-110°) Both satisfactory Cheng and Morrey 25 13* 63 60° (24°-100°) 84° (40°-135°) 69% satisfactory pain relief, 62% excellent or good result Pignatti et al 9 12 Range, 8-33 35° (0°-90°) 91° (—) 92% satisfied with outcome *Does not include four patients converted to total elbow arthroplasty — = data could not be determined from the published material Virak Tan, MD, et al Volume 13, Number 8, December 2005 511 cording to hinge use. However, 7 of the 20 elbows had recurrence of contracture, and 6 underwent a subse- quent contracture release. One other elbow had ulnar plate fracture fixation. Even so, using a hinged device to manage complete ankylosis may be beneficial because of the distraction component and greater abil- ity to control postoperative motion. Another uncommon use of hinged fixation is protecting elbow motion and/or repair in the obese patient. Because of large body habi- tus, it may difficult or impossible to adequately control elbow motion with postoperative splinting or brac- ing. In such patients, skeletal fixation with a hinged fixator allows protected and controlled motion. Summary Hinged external fixation about the elbow is generally viewed as chal- lenging. Similar to other surgical devices, success is dependent on when and how to apply the fixator. An un- derstanding of the anatomy, specific technique, and indications for each problem is crucial for restoring elbow function. Current indications include acute and recurrent instability after osteosynthesis and ligament repair, chronic dislocation, distraction interposition arthroplasty, and postoperative control of motion. Hinged external fixation is also indicated in the uncommon case of acute elbow instability when concentric reduction cannot be achieved by splinting or in a patient who cannot tolerate a prolonged intraoperative surgical procedure. The two main types of hinged elbow fixators are unilateral and multiplanar. Uni- lateral frames inflict less ulnar nerve irritation, have a lower profile, and Figure 4 A 15-year-old girl sustained a fracture-dislocation of the elbow in a fall from a horse. A, Lateral radiograph demonstrating complete ankylosis of the ulnohumeral joint, fixed at 75°. B, Intraoperative photograph demonstrating takedown of the bony ankylosis and distraction interposition arthroplasty 4 years after injury. Postoperative anteroposterior (C) and lateral (D) radiographs demonstrating the new elbow articulations. Hinged Elbow External Fixators 512 Journal of the American Academy of Orthopaedic Surgeons . Universal Hinge, the low lateral humeral pin should be placed from posterolateral to anteromedial, staying posterior to the course of the radial nerve. Injury to the posterior interosseous nerve also

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