Vimala Ramachandran and Thomas F. Varecka
DEFINITION
Malunion of the radial or ulnar shaft can lead to pain, loss of motion, loss of strength, and instability at the level of the wrist or elbow.
Malrotation, angulation (with narrowing of the interosseous space between the radius and ulna), shortening, and loss of the radial bow have been shown in various studies to lead to decreased functional outcomes.4,5,9,10,12
Arthritis has been reported at the level of the proximal radioulnar joint (PRUJ) with longstanding malunions, although the distal radioulnar joint (DRUJ) is most commonly affected by forearm malunions.11
ANATOMY
The forearm can be thought of as a ring, connected at the PRUJ, the interosseous membrane, and the DRUJ (FIG 1).
Force transmission occurs through the interosseous membrane from the radius distally to the ulna proximally.
Radius
The radius lies parallel to the ulna in supination. With pronation, it rotates around the ulna while the ulna maintains its position throughout forearm rotation.
The radius shaft is triangular in cross section, with the apex toward the attachment of the interosseous membrane.
It contains three surfaces: anterior, lateral, and posterior.
The shaft possesses a gentle bow, with the volar surface concave and the dorsal and lateral surfaces convex.1
Schemitsch and Richards9 devised a formula that locates the apex and defines the magnitude of the radial bow for each individual (FIG 2).
Ulna1
The ulna is a long bone that has a triangular cross section in the proximal two thirds and a circular cross section distally.
It possesses three surfaces: anterior, posterior, and medial.
The proximal half of the shaft is slightly concave volarly. The distal half is relatively straight.
The PRUJ consists of the radial head, the radial notch, the annular ligament, and the quadrate ligament.
The DRUJ consists of the sigmoid notch, the ulnar head, the dorsal and volar radioulnar ligaments, the extensor carpi ulnaris (ECU) subsheath, and the triangular fibrocartilage complex (TFCC).
FIG 1 • Lateral projection of the radius and ulna. Relationship of the interosseous membrane to the radius and ulna during forearm rotation. The fibers of the interosseous membrane are longest with the forearm in neutral position and shorten in both pronation and supination.
PATHOGENESIS
Both-bone forearm fractures occur through a variety of mechanisms, including indirect trauma (such as falls on an outstretched arm or motor vehicle accidents) and direct trauma (such as blows to the forearm).
FIG 2 • Measurement of the location and magnitude of the radial bow. The distance y represents the length of the radius as measured from the bicipital tuberosity to the ulnar aspect of the radius. Line a, drawn perpendicular to yfrom the point of greatest curvature of the radius, represents the magnitude of the radial bow (expressed in millimeters). The distance x represents the length of the radius from the bicipital tuberosity to the point where a intersects y. The location of the radial bow is calculated by x/y × 100. (Adapted from Schemitsch EH, Richards RR. The effect of malunion on functional outcome after plate fixation of fractures of both bones of the forearm in adults. J Bone Joint Surg Am 1992;74A:1068–1078.)
Acute fractures treated closed or with intramedullary nailing techniques are more likely to heal malunited.7,8
Radius malunions have a greater effect on forearm rotation than ulna malunions.10,12
A torsional deformity of greater than 30 degrees in the radius leads to significant loss of forearm motion.4
Changes in the length–tension curve of the interosseous membrane may also account for loss of rotation.12
NATURAL HISTORY
Fifty degrees of supination and 50 degrees of pronation are needed for activities of daily living.6
Patients with untreated forearm malunions may experience loss of forearm rotation, PRUJ or DRUJ instability, wrist pain, loss of strength, and arthritis at the PRUJ.11 The severity of the symptoms depends on the degree of malunion and the corresponding alteration in degree and location of the bow of the radius.
Malunions of 10 degrees or less lead to less than a 20degree loss of forearm rotation and hence are clinically insignificant.7
Angular malalignment of more than 20 degrees in the radius or ulna results in clinically significant loss of motion. Greater than 15 degrees of malalignment leads to inability to perform activities of daily living.5,7,10
Patients with greater than 15 degrees of malalignment or loss of the radial bow will have clinically significant loss of motion and strength if left untreated.
PATIENT HISTORY AND PHYSICAL FINDINGS
The preoperative evaluation for patients with forearm malunions includes a detailed assessment of the patient's functional limitations as well as documentation of elbow and wrist range of motion, the supination–pronation arc of the forearm, and the stability of the PRUJ and DRUJ.
Physical examination
The skin is inspected for scarring or previous incision sites.
Muscle bulk and tone are examined.
The wrist, elbow, and malunion site are palpated for tenderness.
Range of motion
The flexion–extension arc of the elbow is measured with the shoulder at 30 degrees of forward flexion.
Rotation of the forearm is ascertained with the humerus stabilized against the chest wall and the elbow at 90 degrees of flexion.
Wrist flexion and extension are determined with the forearm in neutral rotation.
Joint loss of motion may indicate location of pathology.
A high degree of motion loss will lead to functional deficits.
PRUJ and DRUJ
Stability of the PRUJ is assessed by palpation during passive pronation and supination.
The DRUJ is evaluated by stressing the ulna volarly and dorsally while stabilizing the radius.
Subluxation of the ulnar head or the ECU is evaluated during passive range of motion (ECU subluxation test).
The piano key test can also be used to assess for an unstable DRUJ. Patients with a positive piano key sign will have an ulnar head that shifts volarly with a minimal volarly directed force and then rebounds dorsally once that force is removed, much like a key in a piano.
Pain with compression of the radius and ulna at the level of the DRUJ may also be indicative of DRUJ instability or arthritis (DRUJ compression test).
Neurovascular examination
The examiner should check for anterior interosseous nerve (OK sign), posterior interosseous nerve (thumb extension), and ulnar nerve (abduction–adduction of fingers) function.
Inability to perform tasks identifies nerve injury.
IMAGING AND OTHER DIAGNOSTIC STUDIES
AP and lateral radiographs of both forearms should be obtained (FIG 3A,B).
Both the bicipital tuberosity and the radial styloid should be visualized for the film to be adequate.
The degree of angulation and comminution can be calculated from these films.
Contralateral forearm films provide a comparison for the amount of shortening as well as for the location and angle of the radial bow.9
FIG 3 • A,B. AP and lateral radiographs demonstrate a segmental radius shaft fracture resulting in a malunion both proximally and distally despite open reduction and internal fixation. Note the loss of radial bow in both direction and magnitude, narrowing of the interosseous space between the radius and ulna, dorsal positioning of the distal ulna, and nonunion of the basilar ulnar styloid fracture. The patient was unable to supinate to neutral and demonstrated instability at the distal radioulnar joint. C. CT scan demonstrates narrowing of the interosseous space with heterotopic bone formation.
A CT (FIG 3C) scan or MRI can also be obtained to assess for malrotation.2
DIFFERENTIAL DIAGNOSIS
DRUJ injury or instability
PRUJ injury or instability
Injury to the interosseous membrane
Synostosis
Nonunion
NONOPERATIVE MANAGEMENT
Nonoperative treatment of malunions depends on the patient's symptoms and includes occupational therapy for strengthening and range of motion, removable off-the-shelf braces, nonnarcotic medications, and custom molded DRUJ orthoses.
SURGICAL MANAGEMENT
Operative intervention for forearm malunions depends on the functional limitations of the patient, not the degree of deformity apparent on radiographs.
Indications for surgery include loss of forearm rotation that leads to a functional deficit (rotational arc less than 100 degrees), DRUJ instability, unacceptable cosmesis, and painful nonunion.
Risks to the patient include vascular injury, nerve injury or paresthesias (specifically the superficial radial nerve), infection, nonunion, delayed union, need for iliac crest bone graft, synostosis, loss of motion, and DRUJ instability.
Patients treated within 1 year of the initial injury may be more likely to improve functionally and have a lower surgical complication rate.11
Malunions of the radius and ulna are generally treated with an open approach, corrective osteotomy of one or both bones, compression plating, and bone grafting as necessary.
Generally, the more deformed bone is corrected first. If after correction of the first bone forearm rotation is still lacking, an osteotomy is performed on the second bone.
If both bones are equally deformed, the ulna is osteotomized and provisionally plated first to provide a working length for the radius.
Restoration of the radial bow in large part determines functional outcome.
Patients whose radial bow is restored within 1.5 mm of magnitude and located within 4.3% of the contralateral forearm regain 80% of normal motion.
Eighty percent of grip strength is regained if the radial bow is located within 5% of the contralateral side.9
Anatomic realignment of the radius and ulna will not improve functional deficits if a synostosis or significant scarring and contracture involving the soft tissues has occurred.
Occult injury to or contracture of the DRUJ and PRUJ must be identified and treated at the time of surgery.
Preoperative Planning
Radiographs of the affected and contralateral extremity should be reviewed.
A CT scan is helpful to assess for rotational deformity.
A corrective three-dimensional osteotomy is planned using standard AO technique (FIG 4).
The need for corticocancellous iliac crest bone graft should be determined by the degree of shortening.
The surgeon should be familiar with techniques for reconstruction or stabilization of the DRUJ should it remain unstable after correction of the malunion.
Positioning
The patient is positioned supine on the operating table. A radiolucent hand board is attached to the table, centered on the patient's axilla. The affected extremity is then extended and can be positioned for either a volar or dorsal approach to the radius by rotating through the shoulder.
The subcutaneous border of the ulna can be visualized by flexing the arm at the elbow or by placing the arm across the chest.
A nonsterile tourniquet may be used on the arm.
Approach
Radius shaft malunions may be approached either volarly or dorsally.
The volar (Henry) approach is best suited for midshaft and distal radius shaft malunions.
The proximal radius shaft can be approached volarly in this manner; however, injury to the posterior interosseous nerve (PIN) can occur when dissecting the supinator muscle off the radius.
The approach is extensile and can be used to expose not only the entire length of the radius but also the wrist joint.3
The dorsal (Thompson) approach to the radius is used most commonly for proximal malunions.
It provides access to the PIN, allowing the surgeon to isolate the nerve and retract it out of harm's way for the remainder of the procedure.
This approach may be of value for midshaft exposure of the radius, especially in the case of a midshaft segmental malunion (see Fig 3A,B).
The entire dorsal surface of the radius can be exposed through this approach.3
The ulna is approached along its subcutaneous border.
The entire length of the ulna can easily be exposed through this approach.
FIG 4 • Preoperative planning using AO technique for correction of the malunion of the case in Figure 3. A. The malunion is first sketched out from the preoperative radiographs. B. Each fragment is then drawn out separately. C.The osteotomy sites are noted on both the AP and lateral views. The radius is then realigned through the planned osteotomy sites and bone graft (yellow) is inserted to restore the normal magnitude and location of the radial bow.
TECHNIQUES
VOLAR APPROACH TO THE RADIUS
Landmarks: biceps tendon, brachioradialis (BR), radial styloid
Center the skin incision over the malunion site and follow a line that begins lateral to the biceps tendon, continues over the medial edge of the BR, and ends distally at the level of the radial styloid.
The length of the incision depends on the amount of exposure needed to take down the malunion and plate the osteotomy.
To expose the midshaft, dissect between the BR and the pronator teres (PT) proximally (TECH FIG 1).
The superficial radial nerve lies on the undersurface of the BR and must be protected.
Ligate the recurrent radial artery to retract the BR laterally.
Pronate the forearm and release the PT insertion.
Dissect the PT muscle subperiosteally from a lateral to medial direction to expose the volar surface of the radius.
To expose the distal radius, the surgical interval lies between the flexor carpi radialis (FCR) and the radial artery.
Retract the FCR medially and the radial artery laterally to expose the flexor pollicis longus (FPL) and the pronator quadratus (PQ).
Retract the FPL medially.
Release the PQ from its radial insertion and dissect the muscle belly from the volar distal radius.
TECH FIG 1 • Exposure of the radial shaft through the volar approach. This approach is best for midshaft and distal shaft malunions.
DORSAL APPROACH TO THE RADIUS
Landmarks: lateral epicondyle, tubercle of Lister
The skin incision is centered over the malunion and follows a gently curved line starting just anterior to the lateral epicondyle and ending just distal and ulnar to the tubercle of Lister at the wrist (TECH FIG 2A).
Incise the fascia in line with the skin incision.
Dissect between the extensor digitorum communis (EDC) and the extensor carpi radialis brevis (ECRB) proximally.
Pronate the forearm.
Identify the PIN as it emerges from the supinator 1 cm proximal to the distal edge of the muscle (TECH FIG 2B).
Follow the nerve in a distal to proximal direction through the supinator, carefully preserving its motor branches.
Once the nerve is fully mobilized and protected, supinate the arm and release the supinator from the anterior surface of the radius in a medial to lateral direction.
To expose the midshaft of the radius dorsally, the abductor pollicis longus (APL) and the extensor pollicis brevis (EPB) must be mobilized as they cross radially over the dorsal shaft of the radius.
Incise the fascia along the inferior and superior borders of the two muscles and lift them off the radius.
Retract them distally or proximally as needed for exposure of the malunion.
TECH FIG 2 • Exposure of the radius through the dorsal approach. This approach is best for proximal shaft malunions. A. Skin incision on dorsal surface, running from tip of lateral epicondyle toward radial styloid. B. The posterior interosseous nerve is followed through the supinator, with its branches preserved.
APPROACH TO THE ULNA
Landmark: subcutaneous border of the ulna
Make a longitudinal incision along the subcutaneous border of the ulna (TECH FIG 3A).
Incise the fascia in line with the skin incision.
Dissect between the extensor carpi ulnaris (ECU) dorsally and the flexor carpi radialis (FCU) volarly (TECH FIG 3B).
Take care to avoid disrupting the ECU subsheath distally over the ulna head.
TECH FIG 3 • Exposure of the ulna. A. Skin incision along subcutaneous border of ulna. B. Dissection is performed between the extensor carpi ulnaris dorsally and the flexor carpi radialis volarly.
REDUCTION, PLATING, AND BONE GRAFTING
Based on the preoperative scheme, perform the planned osteotomy at the site of malunion using a combination of a water-cooled saw and osteotomies.
Bring the radius out to length and insert bone graft as necessary (TECH FIG 4A).
Make a template for plate contouring so as to match the radial bow (TECH FIG 4B,C).
Plate the malunion using a 3.5-mm compression plate and AO compression plating techniques (TECH FIG 4D–G).
Obtain a minimum of six cortices of fixation proximal and distal to the malunion.
In smaller patients, a 2.7 DC plate may be used instead.
TECH FIG 4 • A. Reduction after osteotomy of the midshaft segmental radius malunion through a volar exposure in the patient in Figures 3 and 4. Because of the segmental nature of this malunion, fixation was accomplished by plating both volarly and dorsally. B. A metal template is placed on the volar surface of the corrected radius. C. The template is used to precisely contour the plate so that when applied, the normal curvature of the radius is restored. (continued)
TECH FIG 4 • (continued) D. Plate fixation. E. Schematic depiction of plate and bone graft placement. F,G. Postoperative radiographs after dual plating of the segmental radial shaft malunion seen in Figure 3. Bone graft was inserted at both the proximal and distal osteotomy sites for realignment of the radial bow and near restoration of radial length. Distal radioulnar joint instability was treated by fixation of the ulnar styloid fracture (using a 0.0620-inch K-wire) and postoperative immobilization in supination.
After fixation, take the forearm through a full supination–pronation arc.
Blocks to motion result from an uncorrected ulnar malunion, DRUJ incongruency or instability, failure to restore the radial bow, synostosis, and soft tissue or interosseous membrane scarring and contracture.
If an ulna osteotomy is required, the plate can be placed on the volar surface of the ulna or on its subcutaneous border in the manner detailed above.
If the DRUJ is unstable, consider palmar capsular reefing, reconstruction with tendon graft, fixation of an ulnar styloid base nonunion, or pinning of the joint in full supination.
If the joint is incongruent or arthritic, consider ulna shortening, matched resection arthroplasty, Darrach resection, or the Sauve-Kapandji procedure.
Reapproximate tendon insertions. For example, in the case of a volar exposure to the distal radius, repair the PQ to its radial insertion using absorbable suture.
Close the subcutaneous tissues and skin.
To minimize the risk of compartment syndrome, do not close the fascia.
Apply a volar splint.
In patients with concomitant DRUJ instability, a sugar-tong splint with the forearm in full supination is placed.
POSTOPERATIVE CARE
In a compliant patient with secure fixation, the splint may be removed 5 to 7 days after surgery and range-of-motion exercises initiated.
A removable orthosis is worn for the next 4 to 5 weeks.
Strengthening exercises are begun 6 weeks after surgery.
Resistive strength training is delayed until radiographic evidence of healing is present (usually 8 to 12 weeks postoperatively).
Normal activities are resumed when a solid union is present.
Plates are generally not removed in adults.
If concomitant DRUJ instability is present:
A Munster cast is applied at the first postoperative visit. The forearm is held in full supination for 6 weeks.
Finger range-of-motion and elbow flexion–extension exercises are begun at the first postoperative visit.
At 6 weeks, any pins in the DRUJ are removed, and supination–pronation exercises are initiated.
OUTCOMES
Trousdale and Linscheid retrospectively reviewed 27 patients with corrective osteotomies for forearm malunions. Indications for surgery included loss of rotation (20 patients), unstable DRUJ (6 patients), and cosmesis (1 patient).11
Of the six patients with DRUJ instability, five had stable wrist joints at follow-up. Three patients were stabilized with correction of the deformity alone, and three required reefing of the palmar capsule and temporary pinning of the DRUJ with Kirschner wires (K-wires).
The patient who underwent the procedure for cosmesis lost 10 degrees of rotation but was happy with the overall appearance and function.
The age of the patient at the time of injury, location of the malunion, and involvement of one or both bones were not associated with the final outcome.
Shorter time from injury to corrective surgery (less than 12 months) was associated with improved forearm rotation and a lower complication rate.
COMPLICATIONS
A 48% complication rate was noted in Trousdale and Linscheid's study.11
Infection
Wrist pain
Loss of motion
Heterotopic ossification
DRUJ instability
Delayed union or nonunion
Superficial radial nerve paresthesias
REFERENCES
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