12.31 Injuries to the distal radioulnar joint

Once the acutely injured patient has been stabilized including a secondary survey, one must be vigilant regarding the potential for hand and wrist injury, which accounts for 17.6% of all missed fractures following blunt trauma. Injuries to the distal radioulnar joint (DRUJ) that are not detected or treated in the acute phase may present later with symptoms of ulna sided wrist pain or instability.

The ulna head articulates with the sigmoid notch of the distal radius (the DRUJ proper), and also with the ulnar side of the proximal carpal row (through the interposed triangular fibrocartilage—TFC). Injuries to the DRUJ can affect both articulations. The radius of curvature of the sigmoid notch is greater than that of the ulna head, reducing skeletal stability from bony congruence and allowing slide and glide motion in the DRUJ. The soft tissues around the ulna head are important for stability of the DRUJ and the proximal carpal row.

Load transfer from the hand is normally primarily radiocarpal (81.4%) but the proportion is dependent on the relative lengths of the ulna and radius (termed ulnar variance). When the ulna is lengthened by 2.5mm (positive ulnar variance), load transmission through the ulnocarpal articulation and TFC increases to 41.9% and reduces to 4.3% with 2.5mm ulnar shortening (Figure 12.31.1). The thickness of the TFC in a given individual varies depending on their ulnar variance. When assessing variance with post-traumatic ulnar wrist pain, comparison views of the uninjured side can be helpful. The TFC is also thinner in its central portion, where perforations are found with increasing prevalence with age.

Most people have a range of approximately 90 degrees of supination and approximately 80 degrees of pronation. Normal forearm rotation is important for many daily activities. The activities of daily living (ADL) require a 100-degree arc of forearm rotation. Supination is particularly important for ADLs and pronation very important for tasks such as use of a computer keyboard or mouse. While shoulder abduction can compensate for lost pronation, deltoid fatigues with prolonged abduction. Supination loses cannot be so easily overcome. With forearm rotation, the ulna remains essentially fixed and the radius rotates around the ulnar head. As the radius and ulna are joined proximally and distally, the relative lengths of the two bones (and so the ulnar variance) depends on the rotational position of the forearm; pronation is associated with relative shortening of the radius. This explains the ulnar-sided symptoms seen with forearm rotation in ulnocarpal impingement (see later).

The TFC is part of a complex soft tissue structure referred to as the triangular fibrocartilaginous complex (TFCC), the integrity of which is essential for DRUJ stability. The soft tissue can usefully be thought of as a complex of tissue whose form and function varies. The palmar and dorsal rims of the TFC form the palmar and dorsal radioulnar (RU) ligaments. The TFC and the deep portion of the ligaments insert into a fovea, the pre-styloid recess, which is found at the base of the ulnar styloid; this point marks the axis of rotation of the forearm. The superficial elements of the RU ligaments insert into the base of the ulna styloid. The insertion may be affected by basal ulnar styloid avulsion injuries, so explaining why DRUJ instability following trauma is much more common with basal styloid fractures than with tip fractures.

The blood supply to the TFC enters through its peripheral dorsal and palmar margins, giving these areas a rich blood supply and the best healing potential. The relatively avascular central portion has poor healing potential. Perforations of the TFC have been classified into acute and chronic lesions, and are described in Chapter 6.4.

During forearm rotation, the radius slides dorsally with supination (ulna head translates palmar) and palmar with pronation (ulna head translates dorsally). The tensions in the RU ligaments vary with forearm rotation, although studies have reached different conclusions regarding which become tense with pronation and which with supination. The apparently contradictory results were reconciled by an anatomical study that found that both the deep dorsal and superficial palmar ligaments tighten with supination (reciprocal changes seen with pronation).

The capsule of the DRUJ attaches to the proximal margin of the RU ligaments and the ulnocarpal ligaments (to the triquetrum and lunate) arise from the RU ligaments distally. On the dorsum, the capsule is thickened to form the floor of the fifth dorsal compartment and the floor of the sixth dorsal compartment explaining the crucial role of the extensor carpi ulnaris (ECU) and its subsheath in ulnar head stability.

Clinical examination of an acute wrist injury begins with examination of the forearm and elbow for fractures of the radius and ulna, elbow dislocation, fracture of the radial head, and dislocation of the proximal RU joint. Associated DRUJ and interosseous membrane injuries in this setting will have implications regarding treatment of the forearm and elbow injuries—the Essex-Lopresti injury (see Chapter 12.33).

Examination of the DRUJ itself begins by inspecting the location of the ulnar head. Dorsal prominence indicates dorsal DRUJ subluxation or dislocation, although swelling may partially obscure this. Palmar subluxation or dislocation may be less obvious clinically. The position, stability, and mobility of the distal ulna must be compared with that of the contralateral uninjured side.

By convention, DURJ instability causing a dorsal prominence of the ulna head is described as ‘dorsal subluxation/dislocation’ (usually accentuated in pronation). Palmar prominence of the ulna head is conventionally described as ‘palmar subluxation/dislocation’ (usually accentuated in supination). However, as stated earlier the ulna is actually the fixed bone in the forearm, around which the radius rotates. Thus, dorsal prominence of the ulna head actually represents palmar subluxation of the distal radius at the DURJ and vice versa.

Systematic palpation for deformity or tenderness in the region of the carpus, ulnar styloid, TFCC, and DRUJ must be performed. In the acute situation, it may not be possible to examine the full range of wrist motion, but it is important to establish that full forearm rotation is possible if a DRUJ injury is suspected.

DRUJ stability is assessed with the so-called ‘piano key’ test. The elbow is flexed and stabilized on the arm of the examining chair or couch. Attempts are made to translate the distal ulna out of the sigmoid notch of the radius in both palmar and dorsal directions, in positions of pronation, supination and neutral forearm rotation. Comparison is made with the contralateral uninjured side.

The neurovascular status of the hand must be evaluated, especially with palmar DRUJ dislocations, where the ulnar nerve and artery are at risk of injury.

In the subacute setting, a careful history and physical examination are vital to establish whether ulnar-sided wrist pain is due to pathology in the DRUJ, TFCC, ulnar carpus, or other structures. If forearm rotation is reduced, it is important to establish whether it is due to incongruity of the DRUJ, proximal RU pathology, or malunion of a forearm fracture.

The patient should be asked to explain in detail the exact mechanism of injury, the specific movements that now provoke their symptoms, and, if possible, to indicate the precise anatomical origin of their pain, by pointing with a static finger. As with an acute injury, systematic direct palpation helps determine which of the ulnar-sided structures are involved in the injury.

It is important to establish the range of forearm rotation, especially the characteristic loss of supination in dorsal dislocations/subluxations, and pronation in volar dislocations/subluxations, and to compare this with the uninjured side to help determine the best method of treatment.

Ulnar-sided wrist pain may be due to increased contact forces between the ulnar head, the triangular disc, and the triquetrum or lunate. This ulnocarpal impingement is more common in the presence of positive ulnar variance and may be diagnosed clinically by performing the following examination manoeuvre. The wrist is passively ulnar deviated, and a longitudinal axial load is applied to the wrist while it is then placed into supination and pronation. The test is positive if the patient’s pain is reproduced. Logically the pain should be worst in pronation as this is the position where the radius is relatively shortened, but pain may also be provoked in supination.

The ‘piano key’ test (see earlier) can be further refined if it is also performed in wrist ulnar and radial deviation. If radial deviation increases the tension in the ulnocarpal ligaments sufficiently to reduce the amount of dorsal and palmar translation of the ulna head, then this indicates that following an ulna shortening osteotomy there may be some potential improvement in DURJ stability.

Tendonitis of the flexor carpi ulnaris (FCU) or ECU tendons may be diagnosed by tenderness or swelling along the tendon sheaths, pain on resisted flexion and ulnar deviation (FCU) or extension and ulnar deviation (ECU), and pain on passive stretch of these tendons (forced extension and radial deviation for FCU and forced flexion and radial deviation for ECU).

A true posteroanterior (PA) radiograph of the wrist in neutral forearm rotation and a perfect lateral of the carpus and the distal radius are the key radiographs required to evaluate DRUJ congruity and reduction.

The true PA radiograph is taken with the shoulder in 90 degrees of abduction, the elbow in 90 degrees of flexion and an overhead x-ray beam. The hand and wrist are placed flat on the x-ray plate to achieve neutral forearm rotation. This view allows an accurate evaluation of the ulna variance. The styloid will appear directly in line with the ulnar cortex of the ulna in this view. If taken incorrectly in supination or pronation there will respectively be artificial lengthening or shortening of the radius apparent on the radiograph.

To determine if a true lateral projection of the wrist has been obtained, the alignment of the carpus should be assessed to ensure the scaphoid tubercle overlies the pisiform. With this projection, the true position of the ulna head relative to the radius will be shown.

To evaluate intra-articular fractures of the distal radius, ulna, and DRUJ, a computed tomography (CT) scan or two oblique views may be helpful.

Live fluoroscopy of the DURJ is useful to assess its stability intra-operatively, or if subluxation or dislocation is suspected but plain radiographs cannot be obtained with the forearm appropriately positioned. A perfect lateral of the distal radius is obtained by live imaging, and the position of the ulna head is assessed. Dynamic stress fluoroscopy and clenched-fist views may be obtained to assess dynamic DRUJ and carpal instability. The ability to obtain and maintain reduction of the DRUJ can also be evaluated directly.

CT scanning is the imaging modality of choice for suspected DRUJ subluxation or dislocation, distal radial fracture with DRUJ intra-articular extension, or DRUJ arthrosis (Figure 12.31.2).

Ulnar head stability within the sigmoid notch of the distal radius can be determined by CT evaluation of the position of the DRUJ in both pronation and supination, with simultaneous cuts of the opposite DRUJ with equivalent forearm rotation.

Arthrography or cine-arthrography may be performed if injury to the TFCC is suspected. Single or triple injection techniques may be employed. Magnetic resonance imaging (MRI) or CT scanning is now commonly performed as an adjunct to arthrography after obtaining plain arthrogram radiographs.

Flow of contrast from the DRUJ to the radiocarpal joint, or into the DRUJ after injection of contrast into the radiocarpal joint is diagnostic of a defect in the TFCC (Figure 12.31.3). Full-thickness central tears of the triangular disc are more commonly attritional and are seen in increasing frequency with increasing age. Peripheral tears that allow tracking of contrast around the triangular disc may result from trauma.

Studies have compared arthrographic findings to the ‘gold standard’ of arthroscopic findings. The rate of falsely identifying a TFCC lesion where none truly exists (a false-positive result) is low. The rate of falsely stating that there is no TFCC disruption when one truly exists (a false-negative result) is substantially higher. In one study, of 32 patients with normal cine-arthrographic findings for TFCC tear, a subsequent wrist arthroscopy showed that 12 patients had full-thickness lesions of the triangular disc (location not specified). Imaging and clinical findings should always be correlated.

High field strength magnets and dedicated wrist coils are now producing high-resolution MRI scans that offer increasing accuracy in the diagnosis of acute ligamentous injuries of the carpus and TFCC, particularly when a combination of conventional and magnetic resonance (MR) arthrography is used. These investigations are now commonly performed to obtain additional diagnostic information, which helps to direct and inform the patient and physician, prior to embarking on more invasive procedures such as wrist arthroscopy, TFC debridement or repair, and RU ligament repair or reconstruction.

Arthroscopic examination of the wrist remains the gold standard for assessing the TFCC. It facilitates diagnosis of perforations (central, peripheral, partial or full-thickness), and chondral injuries of the distal radius, ulnar head, or proximal carpal row. Under surface partial thickness lesions can only be seen with DRUJ MR arthrography or arthroscopy.

Wrist arthroscopy is a useful diagnostic and therapeutic adjunct in the acute treatment of distal radius fractures. TFCC tears are present in as many as 66% of distal radial fractures.

The treatment of DRUJ injuries is dependant of the time since injury, the type of injury, and any associated injuries.

Acute isolated dislocations with no associated fracture are uncommon. By convention the direction of dislocation is defined by the displacement of the ulnar head in relation to the radius. Dorsal dislocation is more common than volar dislocation. If the injury is acute, reduction is usually easy. The stability of the DRUJ should then be assessed following the reduction. Dorsal dislocations tend to be more stable in supination and volar dislocations are more stable in pronation.

If there is only a moderate degree of DURJ instability then this can be treated in an above-elbow cast for 3–4 weeks followed by a forearm cast or splint. If the DRUJ is grossly unstable or requires extreme pronation or supination to maintain stability, then the addition of a percutaneous K-wire fixation across the distal radius and ulna should be considered. In these cases, the TFCC is disrupted and surgery to reattach the TFFC will also restore stability.

Distal radius fractures have an associated ulnar styloid fracture in 61% of cases. However, few of these result in DRUJ instability. Fractures of the tip of the styloid rarely lead to instability. If the fracture involves the base of the ulnar styloid (the site of TFCC attachment), and the DURJ is unstable clinically, then TFCC continuity and joint stability can be restored by internal fixation of the styloid fragment with either with a cannulated screw or 2 fine K-wires and a ‘figure-of-eight’ suture to act as a tension band (Figure 12.31.4).

Intra-articular distal radial fractures frequently involve the sigmoid notch and hence the DRUJ. The aim of treatment is to restore anatomical reduction of both the radiocarpal joint and the DRUJ, with stable fixation, to allow early mobilization of the joints.

If DRUJ subluxation or dislocation is associated with an extra articular forearm fracture (Galeazzi injuries and variants) or an elbow injury, then DRUJ stability is frequently restored by the reduction and stabilization of the forearm injury—particularly where the radial fracture is in the distal third. Having completed treatment of the proximal injury, assessment of the DRUJ reduction and stability should be made clinically and radiographically, and treated accordingly.

When closed reduction of the DRUJ is not possible, interposed soft tissue or bone fragments may be blocking reduction. Exploration is performed via a dorsal approach, through the floor of the fifth dorsal compartment, elevating an ulna-based capsular flap and repairing or reattaching the TFCC with transosseous sutures or suture anchors. Care has to be taken to avoid injury to the sensory branch of the ulnar nerve (Figure 12.31.5).

Symptomatic DRUJ instability is often associated with a malunited distal radial fractures. A trial of non-operative treatment should be undertaken initially with splintage and physiotherapy. If symptoms fail to improve and there is a malunion, then a corrective osteotomy will usually restore stability. If there is no bony deformity or secondary degenerative change, then soft tissue reconstructions may be attempted. Where possible the TFCC should be reattached. If the TFCC cannot be repaired, techniques have been described to reconstruct the volar ulnocarpal ligaments using a strip of FCU or both the volar and dorsal ulnocarpal ligaments.

Degeneration of the DRUJ may arise due to intra-articular malunion or chronic instability. Symptoms may be controlled by intra-articular steroid injections. When injections fail to achieve adequate symptom relief, several salvage procedures have been described, but if they are performed in the presence of associated DURJ instability, this must also be addressed using appropriate soft tissue reconstructive procedures:

If a distal radial fracture heals in a shortened position, but with otherwise satisfactory alignment of the distal radial articular surface, then the sigmoid notch of the distal radial articular surface will lie proximal to the articular surface of the ulna head, which may cause DRUJ degeneration. The TFCC is tented over the ulna head, between the proximal ulnar aspect of the lunate and the ulna head, increasing load transmission in the ulnocarpal side of the wrist and progressive degenerative change between the ulna head, TFCC, and the ulnar carpus. Patients present with ulnar-sided wrist pain, especially during axial loading and ulnar deviation of the wrist and forearm rotation (Figure 12.31.6).

These distinctly different situations all require different surgical solutions:

Early reduction of a dislocated DRUJ will ensure the best outcome. In one study, 25% of patients with dislocation of the DRUJ associated with a radial shaft fracture (Galeazzi), went on to lose more than 25 degrees of forearm rotation. In another study of 19 patients with DRUJ dislocation following Galeazzi fractures, it was shown that in patients in whom anatomical reduction of the DRUJ was achieved, there was minimal loss of function.

The results of soft tissue reconstruction for chronic instability have been variable. However, in one series of 14 patients who had a soft tissue reconstruction proceedure, stability was completely restored in 12.

One study using a Bowers procedure following malunion of distal radial fractures, all patients reported an improvement in their symptoms.

Studies have reported that when using the Sauvé–Kapandji technique for post-traumatic instability, 11 of 17 patients were entirely pain-free with an additional five only complaining of minimal pain. Instability of the ulnar stump was a problem in two patients within the series.

The main complaint following a Darrach’s procedure is instability of the distal ulna stump. Several studies have shown that the results are generally worse in patients with higher demands.

Several studies have shown high levels of success with the use of ulnar shortening for ulnocarpal impingement.

In a study of ulna head replacement in 13 patients, initial results (mean of 2 years) showed a reduction in pain scores of 50%. In one series, total DRUJ replacement was performed in 31 patients. Pain was greatly improved. Grip strength increased along with improved pronation and supination at a mean of 5.9 years follow-up.

The key to appropriate treatment of the DRUJ is early recognition of the injury. By defining the injury pattern acutely by history, clinical examination, and appropriate imaging, treatment of the upper extremity injury can proceed in an integrated fashion (Figure 12.31.7). Thus the goal of achieving full restoration of function to the injured extremity in as short a time period as possible may be realized.