Distal Radio ulnar joint
Acute dislocations and subluxation of the distal radio-ulnar joint (DRUJ) may be isolated or associated with:
Consider concept of simple and complex dislocations.
Distal ulna has convex articular surface; this articulates with the concave semicylindrical sigmoid notch of radius.
The important stabilizers of the distal radio-ulnar joint include all of the separate structures composing the triangular fibrocartilage complex. Of great clinical importance is the fact that these structures blend at the fovea, thus creating the potential for instability of the distal radio-ulnar joint when the ulnar styloid process is fractured.
The flat pronator quadratus muscle originates from a long, narrow strip of the volar aspect of the distal part of the ulna and has a broad insertion on the volar aspect of the radius. It acts as a secondary stabilizer of the DRUJ by providing compressive force across the joint during pronation and supination.
The radius rotates 150° around the fixed ulna . An additional 30° of lateral movement of the radius toward the direction of rotation allows the hand to rotate through a total arc of 180°.
With respect to the fixed ulna, the radius moves dorsally and distally during supination and proximally and volarly during pronation.
The ulna is the stable anatomical point of reference for rotation of the forearm ie. its the radius that dislocates.
Convention dictates however that the direction of dislocation at the distal radio-ulnar joint be described as either ulna dorsal or ulna volar with respect to the distal part of the radius.
Acute Dislocations of the Distal Radio-Ulnar Joint
Mechanism of injury
Essex-Lopresti Injuries (1951)
Comminuted radial head fracture with dislocation of DRUJ.
Longitudinal compression force results in disruption of the DRUJ, interosseous membrane and ends in radial head fracture.
Fracture of the shaft of the radius associated with a dislocation of the DRUJ usually ulna dorsal.
MOI - fall on the outstretched hand with the forearm in pronation.
Hyperpronation produces force across the fixed radiocarpal articulation fracturing the radial shaft. The radius shortens, disrupting the TFCC or fracturing the ulnar styloid.
High-energy trauma can produce, in addition, an
associated fracture of the ulnar shaft, a segmental fracture of the radius, a
dislocation or fracture of the radial head, or a dislocation of the elbow.
ORIF of the radius leads to less problems at the DRUJ.
Irreducible dislocations of the DRUJ are associated with a displaced fracture of the ulnar styloid and ECU interposition.
Fractures of Both Bones of the Forearm
20% of Galeazzi fractures have fractures of the shafts of both bones of the forearm
Up to 60% of forearm fractures have involvement of the DRUJ.
Fractures of the Distal Part of the Radius
Instability and tenderness of the DRUJ may result from incongruity in the sigmoid notch of the radius, caused by residual displacement of fracture fragments. Late instability of the DRUJ is common and typically occurs as a result of:
Clinical and radiographic assessment of the reduction and stability of the distal radio-ulnar joint at the time of the reduction or fixation of an intra-articular fracture of the distal part of the radius is essential for the effective treatment of these complex injuries.
Restricted forearm rotation
Joint above and the joint below.
It is important to obtain a true lateral wrist radiograph.
A PA wrist in neutral may help
Accurate assessment of the stability of the DRUJ is difficult.
CT may be useful when there is persistent pain, loss of range of motion, or deformity of the distal radio-ulnar joint.
If late instability is suspected after the associated fractures have healed, three sets of scans, made with the forearm in pronation, neutral, and supination, are indicated for comparison of the injured and uninjured joints. The scan made with the forearm in pronation is most sensitive for the detection of volar subluxation, while that made with the forearm in neutral is sensitive for the detection of dorsal subluxation and diastasis of the DRUJ. The scan made with the forearm in supination is best for confirmation of the degree of reduction of a subluxation or diastasis. Post operatively a single axial CT scan, through the distal radio-ulnar joint with the forearm in any position of rotation, can aid in the diagnosis of subluxation and dislocation. A line is drawn through the dorsal ulnar and radial borders of the radius and a second line is drawn through the volar ulnar and radial borders of the radius, as described by Mino et al. The adequately reduced ulna must lie between these lines.
Simple Compared with Complex Dislocations
A simple dislocation of the distal radio-ulnar joint can be reduced easily or spontaneously after internal fixation of the associated fracture, or it can be reduced with closed methods if it is an isolated injury.
A complex dislocation is characterized by obvious irreducibility, recurrent subluxations or dislocations, or a mushy sensation caused by soft-tissue interposition when reduction is attempted.
Complex dislocations of the DRUJ are associated with high-energy injuries accompanied by one or two fractures of the forearm. Frequently the ulnar styloid process is also fractured, and usually it is displaced volar to the distal part of the ulna. The extensor carpi ulnaris, because of its firm attachment to the triangular fibrocartilage complex by its fibro-osseous sheath, is usually the structure that prevents spontaneous or easy reduction of the joint in these situations. Typically, after the extensor carpi ulnaris has been detached from the distal part of the ulna together with the triangular fibrocartilage complex and the ulnar styloid process, it slips around either the radial or the ulnar border of the distal part of the ulna to lie volar to it. Consequently, the joint cannot be reduced until the tendon with the attached triangular fibrocartilage complex and styloid fragment has been returned to its anatomical position. To avoid an error in diagnosis in the intraoperative setting, undue force during reduction of the DRUJ must be avoided. When reduction occurs easily, accurate lateral radiographs should be made with the wrist and forearm held in a neutral position without force. Persistent incongruity of the distal radio-ulnar joint in this position suggests the presence of soft tissue interposition.
Soft tissue elements previously reported to cause a block to reduction:
Dorsal dislocations can usually be reduced by supinating the forearm with direct pressure over ulna.
Volar dislocations may be more difficult to reduce because of the deforming force of the pronator quadratus. In this circumstance, the ulna must be mobilized ulnarward and dorsally while the forearm is pronated.
Immobilize 6 weeks, above elbow with forearm in:
Late dislocation especially volar
after six weeks are difficult to reduce closed. Because of the contracture of the pronator quadratus
muscle in volar dislocations. If an open reduction of an irreducible (dorsal or volar)
dislocation of the distal radio-ulnar joint is performed, every attempt should
be made to repair the triangular fibrocartilage complex or to pin the ulnar
styloid process if it is fractured. The distal most fibres of the contracted
pronator quadratus often must be released to accomplish an open reduction of a
late volar dislocation.
If the joint is stable and not easily redislocated after the internal fixation of associated fractures, immobilization in an above-the-elbow cast with the forearm in the appropriate position is all that is required. If the joint redislocates easily, a 1.6mm Kirschner wire should be placed from the ulna to the radius, parallel to the radiocarpal joint and just proximal to the distal radio-ulnar joint. Before the joint is transfixed, the forearm should be placed in full supination for ulna dorsal dislocations and in full pronation for ulna volar dislocations. The limb should be immobilized to protect the wire. The Kirschner wire should be removed and range-of-motion exercises started six weeks after fixation.
Complex dislocations of the DRUJ are characterized by:
sensation/ subtle resistance or springiness is caused by interposition of soft
tissue or bone. In this circumstance, forcible
reduction of the joint and transfixion with a radio-ulnar pin is
contraindicated. Exploration of the joint with use of a
dorsal approach is recommended. A longitudinal skin incision should be made just radial to the
extensor carpi ulnaris tendon, with care being taken to protect the dorsal
sensory branch of the ulna nerve. The extensor digiti minimi should be released
from its sheath and retracted radially. At this point, a fracture of the base of
the ulnar styloid process can usually be found. This fracture displaces with the
attached triangular fibrocartilage complex and its associated structures, the
extensor carpi ulnaris tendon and sheath, and the ulnocarpal ligaments. If the
ulnar styloid process is fractured, it should be stabilized with a Kirschner
wire, a tension band, or intra-osseous wiring. Sometimes, the ulnar styloid process is intact and there is a massive tear of the triangular
fibrocartilage complex instead. The torn triangular fibrocartilage complex must
then be repaired carefully and reattached to the ulna with use of anchor sutures
or pull-out wires.
Injuries of the Distal Radio-Ulnar Joint in Children
Most of these injuries should be treated with closed reduction and above elbow cast immobilization.
If the distal radio-ulnar joint is irreducible or the ulnar epiphyseal fracture is completely displaced, the injury is equivalent to a complex dislocation in an adult. In this case closed reduction and percutaneous pinning of the radial fracture and open reduction and pinning of the ulnar epiphyseal fracture is recommended. Postoperatively, the limb should be immobilized in an above elbow cast, with the forearm in supination, for six weeks, at which time the pins can be removed. Immobilization is then continued for another two weeks, after which rehabilitation is begun.
Dislocations of DRUJ may be simple or complex, stable or unstable. Associated with many fracture patterns.
Treat the associated injury and ensure congruent stable reduction of the DRUJ. Dont forcibly reduce a complex dislocation. If unstable post reduction hold with a transfixing K wire for six weeks.
As a rule of the thumb the position of immobilisation is:
JBJS Vol77-A(6) Jun 1995 pp 958-968; Instructional Course Lectures, The American Academy of Orthopaedic Surgeons. Acute Dislocations of the Distal Radio-Ulnar Joint. Bruckner, James D.; Alexander, A. H.; Lichtman, David M.
Mino, D. E.; Palmer, A. K.; and Levinsohn, E. M.: The role of radiography and computerized tomography in the diagnosis of subluxation and dislocation of the distal radioulnar joint. J. Hand Surg., 8: 30, 1983
Last updated 16/09/2004