Brian D. Adams and Christina M. Ward
DEFINITION
Distal radioulnar joint (DRUJ) instability may be classified as acute or chronic, unidirectional (volar or dorsal) or bidirectional, and isolated or in association with other injuries.
There is no consensus regarding the definition of clinically significant instability, though various radiographic criteria have been used. In general, the key physical finding is the presence of increased anteroposterior translation of the DRUJ with passive manipulation when compared with the normal side.
Although the radius actually rotates around the stable ulna, by convention DRUJ dislocation or instability is described by the position of the ulnar head relative to the distal radius.
ANATOMY
The DRUJ consists of the articulation between the ulnar head and the sigmoid notch of the distal radius and the associated supporting soft tissues.
The DRUJ is not a congruent joint. The shallow sigmoid notch has a radius of curvature that is on average 50% greater than the ulnar head. Joint surface contact area is maximized at neutral rotation.3Though the sigmoid notch is relatively flat, the dorsal and volar rims, which are typically augmented by fibrocartilaginous extensions, do provide an important contribution to joint stability (FIG 1A).13
The soft tissue structures that contribute to DRUJ stability are the pronator quadratus, extensor carpi ulnaris (ECU) and its sheath, interosseous membrane, DRUJ capsule, and several components of the triangular fibrocartilage complex (TFCC). Multiple structures must be injured to result in joint instability.5
The palmar and dorsal radioulnar ligaments are the prime components of the TFCC that stabilize the DRUJ.11 They are thickenings at the combined junctures of the triangular fibrocartilage articular disc, DRUJ capsule, and ulnocarpal capsule.
As each radioulnar ligament passes ulnarly, it divides in the coronal plane into two limbs. The deep or proximal limbs of the radioulnar ligaments attach at the fovea and the superficial or distal limbs attach to the base and midportion of the ulnar styloid (FIG 1B).
The total pronation–supination arc in a normal individual varies between 150 and 180 degrees. Normal pronation and supination involves a combination of rotation and dorsalpalmar translation of the distal radius on the stable ulna.
PATHOGENESIS
The most common cause of DRUJ disruption is a fracture of the distal radius.
Distal radius angulation greater than 20 or 30 degrees creates DRUJ incongruity, distorts the TFCC, and alters joint kinematics.1,4 More than 5 to 7 mm of radial shortening results in rupture of at least one of the radioulnar ligaments.1
Fractures of the tip of the ulnar styloid are not typically associated with DRUJ instability. Fractures of the base of the ulnar styloid can result in disruption of the radioulnar ligaments, causing DRUJ instability.8
Most isolated DRUJ dislocations (not associated with a fracture) are dorsal and caused by forceful hyperpronation and wrist extension, such as with a fall on an outstretched hand or the sudden torque of a rotating power tool.
FIG 1 • A. Distal radioulnar joint (DRUJ) cross-section. The radius of curvature of the sigmoid notch is much greater than the radius of curvature of the ulnar head. B. DRUJ ligaments. (The disk component of the triangular fibrocartilage complex has been removed to show the deep limbs of the radioulnar ligaments.) The volar and dorsal radiopalmar ligaments, the major soft tissue stabilizers of the DRUJ, insert at the fovea and onto the base of the ulnar styloid.
Isolated volar DRUJ dislocations occur with an injury to the supinated forearm or a direct blow to the ulnar aspect of the forearm.
NATURAL HISTORY
Delayed diagnosis and treatment of DRUJ injuries associated with distal radius fractures results in worse outcomes.7
Chronic instability rarely improves spontaneously.
Although there is no proven association between DRUJ instability and the development of symptomatic arthritis, some degeneration should be expected in recurrent dislocators.
PATIENT HISTORY AND PHYSICAL FINDINGS
Patients may report falling on an outstretched hand or a forced rotation of the hand followed by ulnar-sided wrist pain and swelling.
Patients with chronic instability may report a clunk at the wrist with forearm rotation.
Pain and weakness is exacerbated by activities requiring forceful rotation while gripping, such as turning a screwdriver.
Increased passive volar-dorsal translation of the ulna relative to the radius is evidence of DRUJ instability.
When treating an acute distal radius fracture with evidence of DRUJ disruption, the fracture should be reduced and stabilized first, followed by assessment of the DRUJ, as the fracture management alone usually provides adequate treatment for the DRUJ.
In the absence of DRUJ arthritis, patients with DRUJ instability typically have full or nearly full wrist range of motion, including flexion, extension, pronation, and supination.
A thorough patient examination should include the following tests:
Passive translation (“piano key” sign). Perform the test and compare results to the unaffected side. A positive test result indicates DRUJ instability, which is seen in 14 of 14 patients treated by ligament reconstruction.2
Modified press test. Increased depression of ulnar head on affected side (“dimple” sign) indicates instability.2 Pain without increased depression may indicate a TFCC tear.6
Passive forearm rotation. A painful clunk indicates gross DRUJ instability. This should not be confused with more subtle ECU subluxation.
IMAGING AND OTHER DIAGNOSTIC STUDIES
A zero-rotation posteroanterior view is obtained by abducting the humerus 90 degrees, flexing the elbow 90 degrees, and placing the forearm on a flat surface. Signs of DRUJ instability on this view include:
Displaced fracture at the base of the ulnar styloid
Fleck fracture from the fovea of the ulnar head
Widening of the DRUJ
Greater than 5 mm of acquired ulnar or positive variance compared to the opposite wrist
A true lateral radiograph is performed with the arm at the patient’s side and the elbow flexed 90 degrees. Obtaining a true lateral radiograph is important to avoid inaccurate assessment of DRUJ alignment. Mino et al9 showed that only 10 degrees of rotation from neutral resulted in an inability to correctly diagnose DRUJ dislocation on the lateral radiograph.
On a true lateral wrist radiograph, the lunate, proximal pole of the scaphoid, and triquetrum should overlap completely and there should be no space between the triquetrum and pisiform.
CT must be performed on both wrists, with each image obtained with the forearm in identical rotation to allow comparison between the normal and symptomatic joints (FIG 2).
The addition of applied stress to the joint during imaging may aid in detection of subtle instability.10
MRI (with or without intra-articular dye) may be used to detect TFCC tears, although the reported sensitivity and specificity for such injuries is variable. MRI can also be used instead of CT to assess the shape of the sigmoid notch and joint stability.
DIFFERENTIAL DIAGNOSIS
ECU tendinitis or subluxation
Ulnar impaction syndrome
DRUJ arthritis
Pisotriquetral arthritis
Lunotriquetral ligament injuries
TFCC disc tears
NONOPERATIVE MANAGEMENT
Patients with mild chronic instability may benefit from a course of nonsteroidal anti-inflammatories, a splint that limits forearm rotation, and a forearm strengthening program.
Patients with generalized ligamentous laxity and bilateral DRUJ instability have less predictable results with operative reconstruction. In such patients, all attempts at conservative management should be exhausted before considering surgery.
FIG 2 • CT of distal radioulnar joint (DRUJ). A. Well-reduced asymptomatic DRUJ. B. Subluxated DRUJ on the symptomatic side. (A, B: dorsal is left and volar is right.)
SURGICAL MANAGEMENT
Distal radioulnar ligament reconstruction is indicated in cases of chronic DRUJ instability where tissues are inadequate for primary repair of the TFCC.
The goal of ligament reconstruction is to restore DRUJ stability and provide a full, painless arc of forearm motion.
The technique described creates stability by nearanatomic reconstruction of the dorsal and volar radioulnar ligaments.
If present, osseous malalignment must be addressed at the time of ligament reconstruction to obtain a good result.
Preoperative Planning
The surgeon should review imaging studies for evidence of osseous deformity or degeneration of the DRUJ articular surfaces. Soft tissue reconstruction in the presence of substantial residual bony deformity or arthritis will yield poor results.
Intra-articular radioulnar ligament reconstruction requires a competent sigmoid notch for success. A notch that is developmentally flat or that has posttraumatic deficiency of either rim should be treated with a sigmoid notch osteoplasty at the time of ligament reconstruction.
The surgeon should determine the presence of suitable tendon graft. The palmaris longus (PL) tendon is typically used. Alternative graft sources include plantaris, extensor digitorum longus, or most commonly a strip of the flexor carpi ulnaris tendon.
The PL tendon can be identified by having the patient flex the wrist while holding the tips of the thumb and small finger together.
Positioning
The patient is positioned supine with the affected limb resting on a hand table. Additional positioning may be necessary to allow access to graft harvest sites.
A well-padded tourniquet is placed on the upper arm.
TECHNIQUES
PALMARIS TENDON GRAFT HARVEST
The PL tendon is identified by palpation. It is one of the most superficial structures at the distal wrist crease and lies just ulnar to the flexor carpi radialis tendon (TECH FIG 1A).
A single 1-cm transverse incision is made at the proximal volar wrist crease overlying the PL tendon (TECH FIG 1B).
A shepherd’s hook is used to pull tension on the tendon and absolutely confirm its identity.
The tendon is clamped with a hemostat and transected just distal to the hemostat.
A small tendon stripper is passed distal to proximal along the PL tendon in the forearm to complete the harvest.
Alternatively, a strip of the flexor carpi ulnaris tendon can be harvested using a tendon stripper through the same volar incision for graft passage.
TECH FIG 1 • Graft harvest. A. The palmaris tendon can be brought into relief by having the patient touch the thumb and small fingers while flexing the wrist slightly. B. A small transverse incision is made at the proximal wrist crease.
DORSAL APPROACH
A 5-cm skin incision is made between the fifth and sixth extensor compartments overlying the DRUJ (TECH FIG 2A).
The fifth compartment is opened and the extensor digiti minimi is retracted.
An L-shaped capsulotomy is made in the DRUJ capsule with one limb in line with the sigmoid notch and the other just proximal and parallel to the TFCC (TECH FIG 2B). The ECU tendon sheath marks the ulnar limit of the capsulotomy.
The ECU tendon sheath is not disrupted during this approach.
TECH FIG 2 • Dorsal approach to distal radioulnar joint (DRUJ). A. Dorsal skin incision. B. Capsulotomy over the DRUJ.
BONE TUNNEL PLACEMENT
Careful subperiosteal dissection is used to elevate the soft tissue from the dorsal edge of the sigmoid notch for several millimeters.
A guidewire for a 3.5-mm cannulated drill bit is driven from dorsal to volar through the radius.
The tunnel should begin several millimeters proximal to the lunate fossa and about 5 mm radial to the articular surface of the sigmoid notch (TECH FIG 3A).
The tunnel should be parallel to the articular surfaces of both the sigmoid notch and lunate fossa.
Fluoroscopy is used to confirm guidewire placement, and the tunnel is made with a 3.5-mm cannulated drill bit (TECH FIG 3B).
If a corrective osteotomy of the radius is planned, it is easier to make the bone tunnels before performing an osteotomy, but the tendon graft should not be placed or tensioned until the osteotomy is completed.
The ulnar flap of the DRUJ capsulotomy is elevated to expose the ulnar head and neck, being careful not to interrupt the ECU tendon sheath.
The ulnar bone hole travels from the ulnar fovea to exit on the lateral ulnar neck just volar to the ECU tendon (see Tech Fig 3A). Flex the wrist pronate the forearm, and retract the TFCC remnant to reveal the ulnar fovea. Pass a guidewire retrograde from the ulnar fovea to exit on the lateral ulnar neck just volar to the ECU tendon. Confirm the guidewire position with fluoroscopy. If flexing the wrist does not provide adequate exposure, the tunnel may be created antegrade from ulnar neck to fovea, while carefully protecting any TFCC remnant and the ulnar carpus (TECH FIG 3C).
Standard drill bits may be used to enlarge the bone tunnels to accommodate the previously harvested graft. The ulnar bone tunnel must accommodate both limbs of the tendon graft.
TECH FIG 3 • Tunnel placement. A. Bone tunnels are placed to mimic the normal anatomic attachments of the dorsal and volar radioulnar ligaments. B. Fluoroscopy is used to confirm bone tunnel placement. C. The probe indicates the location of the fovea on the ulnar head where the drill should exit. The arrowhead indicates the extensor carpi ulnaris tendon being retracted.
GRAFT PASSAGE
A second exposure is made to visualize the volar aspect of the radius bone tunnel.
A 3-cm longitudinal incision is made extending proximally from the proximal wrist crease (TECH FIG 4A).
Dissection is carried down between the ulnar neurovascular bundle and finger flexor tendons to reach the volar surface of the radius.
A suture passer is passed through the radius bone tunnel from dorsal to volar and used to pull one end of the tendon graft back through the distal radius (TECH FIG 4B).
A straight hemostat is passed over the ulnar head, dorsal to volar, to bluntly pierce the volar DRUJ capsule just distal to the ulnar head. The other end of the graft is grasped and pulled back through the capsule.
At this point, both tendon ends should be visible through the dorsal wound. The suture retriever is used to pass both tendon ends through the ulna bone tunnel from the fovea to exit at the ulnar neck (TECH FIG 4C).
A curved hemostat is used to guide the tendon ends around a portion of the ulnar neck in opposite directions, with one limb of the graft passing deep to the ECU sheath and the other around the volar neck (TECH FIG 4D).
Avoid entrapping any nearby neurovascular structures.
TECH FIG 4 • Graft passage. A. A small volar approach is necessary to allow graft passage. B. A suture passer travels through the radial bone tunnel (dorsal to volar) to retrieve one limb of the graft (indicated by a red vessel loop). C. In this dorsal view, the graft is brought through the volar capsule into the ulnocarpal joint then the two ends are fed into the ulna tunnel. D. In this axial drawing the course of the free graft is visualized. The graft provides a near-anatomic reconstruction of the volar and dorsal radioulnar ligaments. E. The graft (red vessel loop) exits the radial bone hole (short arrow) into the dorsal wound and then enters the ulnar bone hole through the fovea (long arrow). The ends of the graft are then wrapped around the ulna neck.
GRAFT TENSIONING AND FIXATION
The forearm is held in neutral rotation and the DRUJ is manually compressed.
The two graft limbs are pulled taut and a half-hitch knot is made against the dorsal aspect of the ulnar neck.
While maintaining firm tension in the graft, the half-hitch is secured with 3-0 nonabsorbable sutures (TECH FIG 5).
TECH FIG 5 • Graft tensioning. Tension is held on the graft while the knot is secured with a suture.
POSTOPERATIVE CARE
The patient is placed in a long-arm splint with the forearm in neutral to slight pronation or supination, depending on the most stable DRUJ position. At the first postoperative visit, the patient is transitioned to a long-arm cast for 3 weeks.
At 4 weeks postoperatively, the patient is placed in a wellmolded short-arm cast for an additional 2 weeks.
At 6 weeks after surgery, the cast is changed to a removable splint, which is worn for an additional 4 weeks.
The patient should be able to return to most activities by 4 months after surgery, but heavy lifting and impact loading are avoided until 6 months postoperatively.
OUTCOMES
Patients with a deficient sigmoid notch are more likely to experience recurrent instability if the deficits are not corrected.
Most patients experience decreased pain and improved strength and stability while maintaining near-normal range of motion. However, full recovery may require 6 to 9 months.
The described technique effectively restored stability in 12 of 14 patients while providing about 85% of the strength and range of motion of the contralateral unaffected side.2 The two failures resulted from deficiencies of the sigmoid notch that were not recognized preoperatively.
Teoh and Yam12 reported similar results, with restoration of stability in seven of nine patients using a similar reconstructive method.
COMPLICATIONS
Joint stiffness
Recurrent instability
Persistent pain
Weakness of grasp
Infection
Complex regional pain syndrome
REFERENCES
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2. Adams BD, Berger RA. An anatomic reconstruction of the distal radioulnar ligaments for posttraumatic distal radioulnar joint instability. J Hand Surg Am 2002;27A:243–251.
3. Ekenstam F. Anatomy of the distal radioulnar joint. Clin Orthop Relat Res 1992;275:14–18.
4. Kihara H, Palmer AK, Werner FW, et al. The effect of dorsally angulated distal radius fractures on distal radioulnar joint congruency and forearm rotation. J Hand Surg Am 1996;21A:40–47.
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9. Mino DE, Palmer AK, Levinsohn EM. Radiography and computerized tomography in the diagnosis of incongruity of the distal radio-ulnar joint: a prospective study. J Bone Joint Surg Am 1985;67A:247–252.
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11. Stuart PR, Berger RA, Linscheid RL, et al. The dorsopalmar stability of the distal radioulnar joint. J Hand Surg Am 2000;25A: 689–699.
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13. Tolat AR, Stanley JK, Trail IA. A cadaveric study of the anatomy and stability of the distal radioulnar joint in the coronal and transverse planes. J Hand Surg Br 1996;21B:587–594.