The Distal Radioulnar Joint

Anatomy and Biomechanics

The sigmoid notch of the radius is a shallow concavity that articulates with the ulnar head. Computed tomographic data from 100 cadaver forearms demonstrated that the radius of curvature of the sigmoid notch averaged 18.2 ± 8.5 mm compared with only 8.2 ± 1.3 mm for the ulnar head. The dorsal and palmar rims of the sigmoid notch contribute substantially to DRUJ stability. Typically, the dorsal bony rim is angled acutely, whereas the palmar rim is more rounded. The palmar rim is augmented by a fibrocartilaginous lip, which is prominent in 80% and subtle in 18% ( Fig. 14.2 ). The importance of these variations in sigmoid notch morphology has been shown clinically and in biomechanical investigations, in which posttraumatic rim deficiencies substantially reduce joint stability.

The articular contour of the DRUJ varies considerably among individuals in both the coronal and transverse (axial) planes. In the coronal plane, the slopes of the opposing articular surfaces of the notch and ulnar head may be parallel (55%), oblique (33%), or reverse oblique (33%) relative to the long axis of the radius and ulna ( Fig. 14.3 ). A recent study of 1000 radiographs indicated a slightly lower prevalence of reverse oblique morphology at 6%, noting its negative correlation with ulnar positive variance. An evaluation of both magnetic resonance imaging (MRI) and radiographs in 100 wrists from 98 asymptomatic patients revealed a mean difference of 12 degrees when comparing the inclination of the subchondral bone with the articular cartilage, leading to a change in Tolat inclination type in 66% of the wrists. Of interest, no reverse-types were identified when using the cartilage inclination to classify sigmoid notch morphology. Although the slope has no proven impact on joint function in its natural state, acquired changes in lengths of the radius or ulna may alter peak DRUJ articular pressures. A shortening osteotomy through the ulnar shaft for the treatment of ulnar impaction syndrome in a patient with a reverse oblique slope of the DRUJ may have the potential to increase articular pressures at the proximal edge of the notch and the opposing surface of the ulnar head.

In the axial plane, the average sigmoid notch subtends an arc of approximately 50 degrees (see Fig. 14.2 ). Based on an anatomic study of 50 cadavers, four different sigmoid notch shapes were described: flat face (42%), ski slope (14%), “C” type (30%), and “S” type (14%) ( Fig. 14.4 ). The shape has potential implications for risk of traumatic instability and its treatment alternatives. A flat sigmoid notch may be more prone to instability and less responsive to treatment by soft tissue repair alone. In a study of 58 patients and 118 control subjects, investigators identified a negative association between the depth and version angle of the sigmoid notch with triangular fibrocartilage complex (TFCC) foveal injury, implying that increasing articular constraints will enhance the inherent stability of the DRUJ, reducing strain on the soft tissue stabilizers during mechanical loading.

The ulna is the stable unit of the forearm and supports loads transmitted from the radius and carpus. The ulnar head serves as the articular seat around which the radius rotates via the sigmoid notch. The surface of the ulnar head that faces the sigmoid notch forms a slightly asymmetric, partial cylinder of about a 130-degree arc. The articular cartilage coverage of this arc ranges from 50 to 130 degrees and is located on the dorsal, lateral, palmar, and distal surfaces. Due to a slight asymmetry in its curvature, there is a small cam effect at the DRUJ during forearm rotation. Generally, the ulnar head articular surface is inclined and shaped to match the slope of the sigmoid notch, but radiographic appearance of a mismatch is common. In a radiographic study, the mean inclination of the sigmoid notch was found to be 8 degrees, ranging from −24 to 27 degrees, whereas the inclination of the opposing ulnar head surface averaged 21 degrees, ranging from −14 to 41 degrees. These morphologic differences may contribute to the development of adverse symptoms after ulnar shortening osteotomy or changes in radial length following distal radius fracture.

The distal articular surface of the ulna (also called the dome or pole of the ulna ) that articulates with the articular disc of the TFCC varies in shape from a partial sphere to nearly flat. A semilunar distribution of cartilage covers much of the dome, which articulates with the articular disc of the TFCC. At the base of the styloid and encompassing the geometric center of the ulnar head is a shallow concavity called the fovea that is devoid of cartilage and replete with vascular foramina that supply vessels to the TFCC ( Fig. 14.5 ). The fovea is the primary attachment site for the radioulnar and ulnocarpal ligaments. The ulnar styloid is a continuation of the subcutaneous ridge of the ulna, projecting 2 to 6 mm distal to the dome of the distal ulna. It provides an increased area for soft tissue attachments, including the extensor carpi ulnaris (ECU) tendon sheath and the secondary attachments of the radioulnar ligaments. The dorsal (nonarticular) aspect of the head has a groove for the ECU tendon.

Ulnar variance is the term used to relate the difference in lengths of the radius and ulna. Ulna plus (or positive) and ulna minus (or negative) describe the ulna as longer or shorter than the radius, respectively. In a radiographic study of 120 normal Caucasian subjects, ulnar variance averaged −0.9 mm (range, −4.2 to 2.3 mm) with no differences between the sexes.

The TFCC, named by Palmer and Werner, is the term used most commonly to describe the interconnected soft tissues that span and support the DRUJ and ulnocarpal articulations. The TFCC is inclusive of other terms that have been used to emphasize either its fibrocartilage components (e.g., triangular cartilage, articular disc) or its ligament components (e.g., triangular ligament, ulnocarpal ligaments). The TFCC is formed by the (1) palmar and dorsal radioulnar ligaments; (2) triangular fibrocartilage proper, or articular disc; (3) floor of the ECU sheath; (4) ulnocarpal meniscal homologue; and (5) palmar ulnocarpal ligaments. The primary functions of the TFCC are to (1) extend the smooth articular surface of the distal radius to cover the ulnar head; (2) transmit axial force across the ulnocarpal joint, while partially absorbing the load; (3) provide a strong but flexible connection between the distal radius and ulna that allows forearm rotation; and (4) support the ulnar portion of the carpus through connections to the ulna and the radius. Its anatomic complexity and multiple functions place the TFCC at substantial risk for injury and degeneration.

The radioulnar ligaments are the primary stabilizers of the DRUJ. The palmar and dorsal radioulnar ligaments are located at the common juncture of the articular disc, DRUJ capsule, and ulnocarpal capsule. These ligaments are composed of longitudinally oriented lamellar collagen to resist tensile loads and have a rich vascular supply to allow healing. The palmar and dorsal radioulnar ligaments extend from the palmar and dorsal distal margins of the sigmoid notch, respectively, and converge in a triangular configuration to attach to the ulna. As each radioulnar ligament courses in an ulnar direction, it divides in the coronal plane into two limbs. The deep or proximal limbs attach to the fovea, just medial to the pole of the distal ulna, and are referred to as the ligamentum subcruetum. The superficial or distal limbs attach to the base and midportion of the ulnar styloid ( Fig. 14.6 ). Stability of the DRUJ and treatment considerations, therefore, may be influenced by the location of an ulnar styloid fracture. A basilar styloid fracture imparts mechanical discontinuity to the superficial limbs and signifies potential disruption of the deep limbs because of the fracture proximity to their foveal attachments.

The articular disc extends from the ulnar edge of the lunate fossa at the distal rim of the sigmoid notch and blends peripherally with the radioulnar ligaments. There is an inverse relationship between central disc thickness and ulnar variance. The disc is composed of fibrocartilage, and its interweaving and obliquely oriented fibers are arranged to bear compressive loads through its central portion. In biomechanical cadaveric studies, approximately 20% of the load transmitted through the wrist passed through the ulna. The transmitted force varied with wrist position and increased with ulnar deviation and pronation by up to 150%. Alterations in ulnar variance and the presence of the articular disc also affect load transmission. Shortening the ulna by 2.5 mm decreased ulnar load to 4%, whereas increasing ulnar length by 2.5 mm increased the load to 42%. Removal of two-thirds or more of the disc reduced ulnar load to 3%.

Although the articular disc transmits and absorbs compressive forces, it provides minimal constraint to DRUJ translation. The compression borne by the disc is converted partially to tensile forces that splay the TFCC ; these tensile forces are resisted by the radioulnar ligaments. The disc undergoes substantial deformation during forearm rotation. Increased strains are concentrated in its radial portion during axial loading of the wrist, especially in pronation. This region corresponds to the junction of the radially oriented collagen fibers and the obliquely arranged fibers in the central region. These mechanical and histologic findings explain the frequency of traumatic tears near the radial attachment of the disc.

The ECU sheath is a stout structure that extends from the dorsal groove in the ulnar head and the dorsal radioulnar ligament to the carpus. It augments the dorsal capsule and provides its own stabilizing effect on both the DRUJ and ulnocarpal joint, distinct from the ECU tendon. There are three palmar ulnocarpal ligaments that are part of the TFCC: the ulnotriquetral and ulnolunate ligaments, which originate from the palmar radioulnar ligament and insert on their respective carpal bones, and the ulnocapitate ligament, lying immediately palmar to the other ulnocarpal ligaments. The lunocapitate ligament originates from the volar margin of the ulnar head and inserts on the capitate. ^, The contribution of the ulnocarpal ligaments to DRUJ stability is controversial. Because these ligaments have a common origin with the radioulnar ligaments, injuries or disease affecting soft tissue attachments at the fovea may affect DRUJ and ulnocarpal stability. For example, the chronic inflammatory synovitis of rheumatoid arthritis may cause insufficiency of these foveal soft tissue restraints and lead to progressive subluxation of the radioulnar joint and a supination deformity of the ulnocarpal joint.

The irregularly shaped, soft tissue structure between the ulnocarpal capsule, articular disc, and the proximal aspect of the triquetrum has been referred to as the meniscus homologue ( Fig. 14.7 ). This synovial fold, described as the medial wall of the hammock-like structure of the TFCC, stretches with radial deviation of the wrist and crimps into a meniscus-like shape in the coronal plane with progressive ulnar deviation. The size, shape, and distal insertion of the meniscus homologue varies. There is a consistent insertion of the meniscal homologue into the triquetrum, but there is variability of a broader insertion into the fifth metacarpal, and occasionally into the articular surface of the triquetrum and/or into the lunotriquetral ligament, which may obscure visualization of the lunotriquetral interosseous ligament during wrist arthroscopy.

Several soft tissue structures are considered to be secondary stabilizers of the DRUJ including the pronator quadratus, ECU, interosseous membrane (IOM), and the DRUJ capsule. The relative contributions of these structures to joint stability are not well defined, but there is common agreement that gross DRUJ instability requires disruption of multiple structures. The pronator quadratus and ECU musculotendinous units provide dynamic stability. The pronator quadratus compresses the radioulnar joint during active pronation and passive supination. In pronation, ECU contraction elevates the ulnar carpus dorsally, thereby appearing to depress the ulnar head palmarly. ^,

The IOM contributes substantially to the mechanical integrity of the forearm. Complete radioulnar dissociation at the DRUJ does not occur unless the IOM is incompetent. The central band of the IOM that is part of the middle ligamentous complex runs proximally from the radius to its distal attachment on the ulna. The central band provides 71% of the soft tissue contribution to longitudinal forearm stiffness and is the primary structure resisting proximal migration of the radius when the radial head is damaged or removed. The distal oblique bundle (DOB) was identified in all of a series of cadaver dissections, although its thickness varied widely among specimens. The DOB originates from the ulna near the proximal border of the pronator quadratus muscle, and courses distally toward the DRUJ to blend into the capsular tissue of the DRUJ and to insert into the inferior rim of the sigmoid notch of the radius. Some DOB fibers continue distally to insert on the anterior and posterior ridges of the sigmoid notch and to become continuous with the dorsal and palmar radioulnar ligaments. The presence of the DOB confers increased dorsal-palmar translational stability on the DRUJ based on a cadaver model. This stabilizing effect of the distal IOM appears to influence DRUJ stability following ulnar shortening osteotomy; an osteotomy performed proximal to the distal IOM improves DRUJ stability more than does an osteotomy performed distal to the distal IOM. Using the same testing apparatus, alterations in the coronal plane relationship of the distal radius and ulna, such as might occur following a displaced distal radius fracture, were identified to compromise the stabilizing effect of the DOB on the DRUJ. A third cadaveric study demonstrated no differences in DRUJ stability based on the proximal-distal location of a simulated fracture relative to the distal IOM radial insertion.

Traditionally, the DRUJ capsule has been considered too redundant and weak to provide effective joint stabilization, even though histologic studies show a well-defined fiber orientation that suggests a potential stabilizing role of the capsule. The palmar capsule has a prominent redundant fold extending from the inferior radial aspect to the distal ulna border that forms a pocket for the ulnar head in supination and helps to limit DRUJ translation. The dorsal capsule is thinner and homogeneous with a transverse orientation, indicating less potential to provide stability.

The precise roles of the radioulnar ligaments have been debated. There are two clinically relevant themes concerning their stabilizing functions. First, the ligaments act together with the morphologic boundaries of the sigmoid notch to constrain the joint. Second, both ligaments are necessary for normal joint stability in both palmar and dorsal directions. ^, Ligament tension peaks at the extremes of translation and rotation as the ulnar head simultaneously compresses against a rim of the notch creating both a tether and a buttress to resist dislocation. In one view of the functions of these ligaments, the dorsal ligament restrains the ulna from dorsal displacement during pronation and the palmar ligament prevents palmar displacement during supination. Supporters of this theory tested the joint with a passive rotation force applied to the joint and measured strain within the ligaments. The major restraining ligament was deemed the one with the greatest strain. ^{, ,}

In the opposing view, the palmar ligament prevents dorsal displacement in pronation, and the dorsal ligament restrains palmar displacement in supination. These results were found by testing the joint with a passive translation force and observing bone displacements. ^, Both theories have merit in the clinical management of instability, and the discrepancy can be considered by appreciating the dual insertions of each ligament on the fovea and ulnar styloid. Despite one ligament possibly providing the dominant restraint under a specific condition, the other ligament provides a secondary restraint, and both must be injured to allow complete dislocation. In patients with bidirectional or severe unidirectional instability, injury of both ligaments should be suspected. From a clinical perspective, the foveal attachments of the radioulnar ligaments are the critical stabilizers of the DRUJ.

Improved understanding of the neurovascular supply to the TFCC has been developed using modern imaging and immunohistochemical staining studies. The vascular supply to the articular disc is variable and plays a central role in its healing potential and the treatment options. The TFCC vascular supply is primarily via the anterior interosseous and ulnar arteries. The anterior interosseous artery provides palmar and dorsal branches to the DRUJ. The dorsal branch supplies most of the dorsal periphery, and the palmar branch supplies the volar periphery near the radius. Dorsal and palmar branches of the ulnar artery supply the styloid area and ulnar part of the volar periphery. Vascular penetration into the disc extends only to its outer 15%, leaving the central portion hypovascular, or essentially avascular ^, ( Fig. 14.8 ). The vascular supply of the peripheral articular disc decreases with age. Based on these findings, a central disc injury has little or no possibility to heal, whereas injuries at the periphery have reasonable healing potential. The neural supply of the TFCC is concentrated in the dense and loose connective tissues deep in the prestyloid recess and has been traced from the dorsal sensory branch of the ulnar nerve and inconsistently from the medial antebrachial cutaneous nerve, posterior interosseous nerve, anterior interosseous nerve, superficial branch of the ulnar nerve, and the palmar cutaneous branch of the median nerve. ^, Selective denervation of the TFCC has been suggested based on an algorithm associated with sequential nerve blocks. Innervation of the TFCC has been confirmed with immunohistological assessment, and cadaveric studies have indicated potential clinical application of denervation procedures using electrothermal treatment at the time of wrist arthroscopy.

The normal arc of pronation and supination ranges among individuals from 150 to 180 degrees. Additional rotation of up to 30 degrees occurs through the radiocarpal joint. The axis of forearm rotation varies during motion, especially under load, but generally passes through a point near the cross-sectional centers of the radial head proximally and ulnar head distally. At the level of the DRUJ, the axis of rotation shifts slightly dorsally with pronation and slightly palmarly with supination. During forearm rotation, translation occurs between the ulnar head and sigmoid notch, resulting in a combination of rolling and sliding movements at the articular surface. The radius slides palmarly during forearm pronation and dorsally with supination. Total dorsal-palmar translation with the forearm in neutral rotation was measured at 8 to 9 mm in normal cadaveric joints subjected to externally applied forces, although in vivo studies suggest that the actual amount of translation may be considerably less. Nonetheless, when the unloaded forearm is in the neutral position, articular contact is maximal, reaching 60% of the available surface area. At the extremes of pronation and supination, there may be only 2 mm of articular contact at the margins of the sigmoid notch (<10% of the articular surface area). Translation can occur because the sigmoid notch is shallow, and its radius of curvature is 50% to 100% greater than that of the ulnar head.

Physical Examination

A comprehensive examination of the involved upper extremity is warranted to evaluate for local and remote causes of wrist symptoms, and comparison with the contralateral DRUJ is important. The influence of elbow and forearm pathologic conditions on DRUJ function (particularly disorders of the PRUJ) must be recognized to avoid pitfalls and to optimize treatment. Vascular or neurogenic causes of wrist symptoms, including cervical radiculopathy or ulnar neuropathy, should be considered.

The evaluation progresses from a general inspection (previous incisions or wounds, swelling, atrophy, dysvascular or dystrophic changes), to active and passive range of motion, strength, tenderness, and provocative maneuvers. Diagnostic injection(s) may be useful to localize symptoms.

The examiner begins by evaluating active and passive motion of the wrist and forearm, with comparison to the opposite side. Next, point tenderness is identified by using a single palpating fingertip at the distal radius and ulna, DRUJ, radiocarpal and ulnocarpal joints, ulnar styloid, proximal triquetrum, pisotriquetral joint, hook of the hamate, the scapholunate interval, and the lunotriquetral interval. Tenderness in the soft depression between the flexor carpi ulnaris (FCU) tendon, ulnar styloid, and triquetrum (the so-called ulnar snuffbox) is suggestive of TFCC pathology. Tenderness and or crepitus of the ECU and FCU tendons indicates possible tenosynovial hypertrophy or tendinopathy. A benign mass such as lipoma or ganglion cyst is not uncommon in this location. An effusion at the ulnocarpal joint or radioulnar joint may indicate degenerative or inflammatory arthritis, especially when associated with dorsal prominence of the ulnar head.

Symptoms elicited during provocation tests of the DRUJ may indicate instability, TFCC injury, or arthritic conditions of the DRUJ. Decreased motion and/or crepitus during pronation-supination are signs of DRUJ arthritis; pain may be accentuated by manually compressing the joint. ECU tendinitis and lunotriquetral ligament tears can mimic DRUJ symptoms. ECU instability and subluxation are most apparent with forearm supination, flexion, and ulnar deviation of the wrist. The synergy test is a useful and discriminating test for ECU tendinopathy, and helps to discriminate between articular and nonarticular etiologies of pain. In this test, the patient places the affected elbow on the examining table with the forearm in full supination, and the fingers in full extension and abduction. The examiner squeezes the thumb and middle finger together against the patient’s active resistance, and a positive test is reproduction of ulnar-sided pain along the ECU. ^, The lunotriquetral joint is assessed with the shear or ballottement test. In this test, the examiner stabilizes the lunate between the thumb and index finger of one hand, while manually shearing the triquetrum against the lunate articular surface in a dorsal-palmar direction with the thumb and index finger of the other hand. One may distinguish between DRUJ conditions and pain associated with pisotriquetral arthritis by palpating the pisotriquetral interval and by pressing and manipulating the pisiform against the triquetrum.

Several variations of ulnocarpal stress testing are useful for attempting to reproduce symptoms of ulnocarpal instability caused by disc tears or ulnocarpal degeneration. The patient’s forearm is positioned vertically on the examination table and the examiner grasps the hand and applies an axial load through the wrist. The wrist is moved passively through radial and ulnar deviation while moved through an arc of pronation and supination. ^, Alternatively, the wrist is moved passively through a flexion and extension arc in different forearm positions, while maintaining an ulnar deviation posture under axial load. Another maneuver involves placing the wrist in passive ulnar deviation while creating increased central loading of the disc and ulnar dome by simultaneously depressing the ulnar head volarly with the index and long fingers and pushing the pisiform dorsally (pisiform boost) with the examiner’s thumb on its palmar surface. This maneuver is performed most effectively with the forearm in neutral rotation where the DRUJ is most lax ( Fig. 14.9 ).

Increased anteroposterior translation of the radius on the ulna during passive manipulation is evidence of DRUJ instability. In the DRUJ ballottement test, the examiner grasps the radius and the carpus firmly, while translating the distal ulna in the dorsal and palmar directions within the sigmoid notch using the thumb and index finger of the other hand. The degree of translation, the firmness of the endpoint, and any symptoms of pain are important to record in this test. Because joint translation varies with forearm position and among individuals, the test should be done in full supination, pronation, and neutral and should be compared with the opposite side. A piano key sign describes the relative hypermobility of the ulnar head with the forearm in full pronation, and a positive test is defined by pain elicited following release of the ulnar head after transient palmar depression. The ulnocarpal stress test is performed by placing the patient’s elbow on the examining table with the forearm-hand axis toward the ceiling. Comparison to the contralateral side should be done. The examiner supports the elbow with one hand and uses the other to bring the wrist into ulnar deviation; this maneuver will create compression across the ulnocarpal joint. Maintaining this wrist position, the examiner rotates the patient’s forearm. Ulnar wrist pain during forearm rotation is considered a positive ulnocarpal stress test. Clinical evaluation for DRUJ instability is challenging due to the subjective nature of the examination and the variability in “normal” DRUJ translation. In a cadaveric model, one biomechanical study used motion analysis to assess DRUJ instability by comparing the accuracy of the ulnocarpal stress test, the piano key test, and the ballottement test. This analysis suggested that the ballottement test was the most accurate test of the three in detecting DRUJ instability following TFCC release at the fovea and base of the ulnar styloid. Omokawa and colleagues have described the effects of sequential ligamentous sectioning on DRUJ stability in the setting of a ballottement test, highlighting the stabilizing influences of the ulnocarpal and radioulnar ligament complexes, the ECU subsheath, and the distal IOM. The authors confirmed that wrist position influences DRUJ stability. The authors also found that isolated sectioning of the ulnocarpal ligament complex did not affect adversely DRUJ stability compared with the intact wrist in neutral wrist position, but sequential sectioning of the radioulnar ligaments and the ECU subsheath significantly increased joint displacement with mechanical loading. Dynamic loading of the ulnocarpal joint by the patient can be done using the press test. In this test, the patient grasps the arm of his chair and pushes up toward a standing position. A positive press test involves provocation of focal ulnar wrist pain during loading and is considered to be sensitive for detecting a TFCC tear.

Imaging

Radiography

Radiographic evaluation of the DRUJ should begin with standard posteroanterior, oblique, and lateral views. A standard posteroanterior radiograph (neutral forearm rotation) is taken with the shoulder abducted 90 degrees, the elbow flexed 90 degrees, the forearm and palm flat on the cassette, and the wrist in neutral flexion-extension and neutral radioulnar deviation. The position of the ECU groove can be used to determine whether the posteroanterior view is acceptable. When the cortical outline of the concavity of the groove is radial to the long axis of the ulnar styloid, the posteroanterior view is acceptable for measuring ulnar variance. A neutral rotation position is recommended to standardize ulnar variance measurement. Although changes in variance may be subtle, a posteroanterior view with the forearm pronated, with the patient making a power grip, or with combined pronation and grip is helpful to identify dynamic positive ulnar variance.

Several techniques have been described to measure ulnar variance on the posteroanterior view. In a study comparing three commonly used methods, differences were very small and not likely to be of clinical importance. The method of perpendiculars is the most popular. In this method, a line is drawn through the volar sclerotic line of the distal radius perpendicular to its longitudinal axis. The distance between this line and the distal cortical rim of the ulnar dome is measured ( Fig. 14.10 ).

A standard lateral radiograph is taken with the shoulder at the patient’s side (0 degrees abduction), the elbow flexed 90 degrees, and the wrist in a neutral position. An accurate lateral view is confirmed by the palmar surface of the pisiform visualized midway between the palmar surfaces of the distal pole of the scaphoid and the capitate (the so-called SPC lateral). Other evidence of correct alignment includes superimpositions of the lesser four metacarpals, the proximal pole of the scaphoid on the lunate, and the radial styloid on the center of the lunate. Semisupinated and semipronated radiographic views improve visualization of the palmar and dorsal rims of the sigmoid notch and the ulnar head and are useful to evaluate for fractures and arthritis. Osteophyte formation at the proximal margin of the ulnar head is an early sign of arthritis.

Despite attention to detail of positioning, standard radiographs are imprecise for the diagnosis of DRUJ subluxation. Mino and associates showed that with 10 degrees of supination or pronation, subluxation appeared reduced and dislocation appeared subluxated. DRUJ instability secondary to soft tissue deficiency may be identified with radiographic stress views. Iida et al. demonstrated a significant increase in radioulnar gap compared with the uninjured side in 30 patients with chronic radioulnar ligament insufficiency using a clenched-fist posteroanterior view with the forearm in pronation. The authors defined the DRUJ gap as being the sum of the shortest distance measured between the ulnar head and the volar and dorsal margins of the sigmoid notch. The average DRUJ gap for the control (noninjured) wrists was 3.0 mm (range, 0.4 to 6.5 mm), while the average gap for the injured wrists was significantly greater, measuring 3.6 mm (range, 0.6 to 10 mm). The large variance of DRUJ gap measurements in the uninjured wrists, however, creates a challenge for assigning an absolute value to DRUJ gap, and determination of pathologic DRUJ instability.

In the context of distal radius fractures, several radiographic findings may support a diagnosis of DRUJ instability. Ulnar styloid fracture displacement greater than 2 mm may be consistent with DRUJ instability. Nakamura and colleagues demonstrated increased radial translation, radial shortening, decreased radial inclination, or 4 mm or greater ulnar styloid fracture displacement in a group of 29 patients with displaced distal radius fractures and arthroscopically confirmed foveal avulsions of the distal radioulnar ligaments.

Computed Tomography

Computed tomography (CT) is the most accurate and reliable imaging technique for the demonstration of DRUJ instability. To optimize its diagnostic utility, the forearms should be aligned with the axis of the gantry and imaged simultaneously. It is important to image both wrists in the three positions of neutral, maximum supination, and maximum pronation. Several measurement methods have been used, including use of dorsal and palmar radioulnar lines described by Mino and associates, epicenter and congruency methods proposed by Wechsler and colleagues, and radioulnar ratio described by Lo and coworkers ( Fig. 14.11 ). Wechsler and colleagues found the congruency and epicenter methods to be more sensitive and accurate than the radioulnar lines method. Lo and coworkers claimed that all three methods either overestimated or underestimated the extent of subluxation. They found the congruency method to be simple and easy, but highly subjective, with 90% of cases deemed subluxated whether in a normal or abnormal wrist. The radioulnar ratio method was more reliable, but it was thought to be too cumbersome in the clinical setting. Its use was recommended when subluxation was not clearly evident on side-to-side visual comparison with the unaffected wrist. Pirela-Cruz and colleagues found applied stress to the DRUJ during CT aided in the identification of subtle signs of instability. A combination of methods should be used when instability is subtle, but conclusions must correlate with physical findings, and overdiagnosis should be avoided.

CT is also a valuable tool for evaluating fractures, developmental deformities of the sigmoid notch and ulnar head, and degenerative arthritis. Rozental and associates evaluated a series of distal radius fractures with CT and identified displacement of sigmoid notch fractures that were not recognized on standard radiographs.

Magnetic Resonance Imaging

Using state-of-the-art technology, improved scanning algorithms, and dedicated wrist coils, MRI’s exceptional soft tissue contrast and direct multiplanar acquisition enables accurate evaluation of the articular cartilage, radioulnar ligaments, and the TFCC without ionizing radiation ( Fig. 14.12 ; see also Chapter 13 , Figs. 13.21 and 13.26 ). Whether or not contrast improves the accuracy of MRI is controversial. A prospective study comparing MRI with magnetic resonance arthrography (MRA) in 60 consecutive patients with clinical and arthroscopic confirmation of TFCC injury demonstrated sensitivity and specificity for a TFCC tear of 68% and 60% (MRI) versus 95% and 100% (MRA). In a similar study by Daunt and colleagues, noncontrast MRI was 98% accurate in identifying arthroscopically confirmed tears and perforations of the articular disc. Similar to CT, MRI can be used to assess DRUJ instability through anatomic measurements. Dynamic “4D” imaging may become an important tool to identify lesions and instability of the ulnocarpal joint and DRUJ.

Ultrasonography

The reliability of ultrasound in the evaluation of DRUJ instability has not been demonstrated, although recent work indicates its potential to assess DRUJ instability in a study comparing patients with and without TFCC injuries. Ultrasound may also be helpful in the dynamic assessment of ECU instability; however, an understanding as to the influences of forearm and wrist position on ECU tendon displacement relative to the ulnar groove is important ^, ( Case Study 14.1 and Video 14.1 ).

Case Study 14.1

Tendinopathy

A 17-year-old female high school hockey star presents with painful dominant right wrist, ulnar side. She describes feeling a “snap” while making a slapshot 6 months previously. She attempted rest with splinting for several months and a 3-month course of therapy. She has been unable to return to playing, although she experiences minimal discomfort with daily, school, or other recreational activities. The patient declined cortisone injection and was referred for definitive treatment.

eFig. 14.1 displays the presenting radiographs. Physical examination revealed:

• Tenderness to ECU without snapping

• Lax, no gross instability of DRUJ

• Pain with resisted supination and ulnar deviation

• Ulnar impaction positive in full supination; otherwise negative

What is your working diagnosis?

• • a.

    Ulnar impaction syndrome

  • b.

    Kienböck disease

  • c.

    TFCC tear

  • d.

    ECU instability

  • e.

    Radioulnar instability

ANS: (d) ECU instability

What additional workup should be ordered?

• • a.

    Bone scan

  • b.

    CT in three positions of rotation

  • c.

    MRI study

  • e.

    Bilateral pronated grip films

  • f.

    Dynamic ultrasound

ANS: (f) Dynamic ultrasound

See Video 14.1 , then review the following questions.

What is your diagnosis?

• • a.

    Ulnar impaction syndrome

  • b.

    Kienböck disease

  • c.

    TFCC tear

  • d.

    ECU instability

  • e.

    Radioulnar instability

ANS: (d) ECU instability

What are your treatment recommendations?

• • a.

    Ulnar-shortening osteotomy

  • b.

    Radial-shortening osteotomy

  • c.

    Arthroscopic TFCC repair

  • d.

    ECU stabilization

  • e.

    Tendon graft ligament reconstruction of DRUJ

ANS: (d) ECU stabilization

See eFigs. 14.2 through 14.5 for a description of the surgical technique. The follow-up is shown in eFig. 14.6 .

Triangular Fibrocartilage Complex Lesions

Palmer’s classification divides TFCC lesions into two broad categories: traumatic and degenerative ( Table 14.1 and Fig. 14.13 ). Traumatic TFCC injuries are classified further according to the location of the tear. Most traumatic tears result from an acute rotational injury to the forearm, a combined axial load and distraction injury to the ulnar border of the forearm, or a fall on the pronated outstretched hand. Although Palmer’s classification provides an accurate anatomic description of traumatic tears, it does not guide treatment or indicate prognosis. Additionally, the scheme implies that each type occurs in isolation, whereas clinical studies have found that multiple components of the TFCC may tear in the same injury.

Most acute, isolated TFCC tears do not require early treatment. Although the incidence of TFCC injuries associated with distal radius fractures is estimated to be 13% to 60% using imaging methods or surgical inspection, the incidence of persistent problems related to these injuries is much less. The necessity of treatment for TFCC tears depends on the presence of persistent joint pain from mechanical irritation or synovitis caused by the tear, associated fractures or malunions, or posttraumatic instability of the DRUJ. Diagnosis and treatment of isolated traumatic TFCC injuries are presented separately from associated injuries or DRUJ instability (see also Chapter 15, Chapter 17 ).

A degenerative TFCC tear can result from chronic, excessive loading through the ulnocarpal joint and is a component of ulnar impaction syndrome. It is important to recognize, however, that natural degeneration of the ulnocarpal joint occurs also. In cadaveric examinations, TFCC perforations and chondromalacia of the ulnar head, lunate, and triquetrum were found in 30% to 70% of specimens. ^, Specimens with ulnar-negative variance had less severe degenerative changes. Palmer classified degenerative lesions by the location and severity of degeneration involving the TFCC, ulnar head, and carpus. Although Palmer’s classification implies a specific progression of degeneration among the structures, involvement and severity of degenerative changes in the articular disc, lunate, triquetrum, lunotriquetral interosseous ligament, and ulnar head vary widely in this condition, with any one structure or combination of structures having various stages of degenerative changes.

Treatment of degenerative TFCC lesions should consider (1) debridement of the joint, (2) reduction of load across the ulnocarpal joint, (3) DRUJ stability, (4) DRUJ articular congruity, and (5) presence of developmental or acquired skeletal deformities.

Palmer’s Classification of TTFC Lesions

Class 1A Tear

A class 1A tear typically manifests as ulnar-sided wrist pain that is aggravated by power grip, especially with ulnar deviation or forearm rotation. It is a relatively common injury that may cause pain and mechanical symptoms such as clicking, but it does not cause DRUJ instability. Typically, this tear is confined to the disc, located 2 to 3 mm ulnar to its radial attachment, and oriented volar to dorsal. Initially, these injuries should be managed conservatively using rest, immobilization, antiinflammatory medications, and, occasionally, a corticosteroid injection. Patients with ulnar-positive wrists may be less likely to respond to conservative management.

When symptoms persist despite conservative management of traumatic TFCC tears, arthroscopic debridement is the preferred treatment and is discussed in Chapter 17 . If a disc tear is identified during an open wrist procedure for another indication, the tear should be debrided to a clean and stable margin. It is important that the peripheral 1 to 2 mm of the articular disc be preserved to avoid injury to the radioulnar ligaments. Outcomes following debridement of the radial remnant of the disc and concomitant repair to the radius are controversial, particularly in light of the relatively good outcomes following arthroscopic debridement alone; this more complex technique is discussed later for the class 1D tear.

Class 1B Tear

A class 1B injury is a partial or complete avulsion of the TFCC from its ulnar attachments, with or without an ulnar styloid fracture. DRUJ instability may or may not be present. A fracture through the base of the styloid that may disrupt both the deep and superficial limbs of the TFCC is more predictive of DRUJ instability than the more common fracture through the shaft or tip. However, most ulnar styloid fractures do not cause DRUJ instability, which is partly related to the dual ulnar attachments of the TFCC. ^{, ,} The ulnar styloid provides attachments for portions of the ulnocarpal ligaments, ^, ECU tendon sheath, and superficial limbs of the radioulnar ligaments, whereas the deep limbs insert into the fovea of the ulnar head. The styloid tip is devoid of soft tissue attachments. Also, a complete avulsion of the radioulnar ligaments and gross instability can occur without a styloid fracture. Occasionally, a small fleck of bone is avulsed from the fovea indicating disruption of the deep limbs of the radioulnar ligaments. Recognition of these injury variations may lead to earlier diagnosis and treatment.

Symptoms and physical findings associated with a class 1B tear are similar to those of a class 1A tear, although a click is usually absent and point tenderness is characteristically volar to the ulnar styloid. This localized tenderness coincides anatomically with the fovea and, appropriately, tenderness located here has been termed the fovea sign. Evaluation of DRUJ stability, as described above, is likely to produce pain even if the DRUJ is stable.

Because these tears may progress to a destabilizing injury of the TFCC and DRUJ, initial treatment should restrict forces acting at the TFCC by protective above-elbow immobilization for 4 to 6 weeks with the forearm in neutral rotation. Subsequent treatment is directed toward gradual recovery of motion and strength. Most of these injuries respond to conservative measures, with surgery indicated for persistent symptoms or evidence of DRUJ instability. Arthroscopic treatment of peripheral TFCC tears has evolved rapidly over the past few years. Symptomatic, complete tears can be repaired by arthroscopic-assisted techniques including transosseous or direct capsular suture repair ^, (see Chapter 17 ). An open repair is considered in grossly unstable or chronic injuries, provided there is reasonable ligamentous tissue remaining for repair. Chronic basistyloid nonunions associated with DRUJ instability can be addressed with surgical repair and bone grafting of the nonunion fragment (see section on acute DRUJ instability).

Class 1C Tear

A class 1C injury is a partial or complete tear of the ulnocarpal ligaments, either as an intrasubstance rupture or as an avulsion from their carpal insertion. These injuries can occur in combination with class 1B tears or lunotriquetral ligament tears, or both. They are reported much less frequently than other TFCC injuries, probably because they are more difficult to diagnose. Contributions of the ulnocarpal ligaments to DRUJ stability are unclear. The most obvious sign of injury is a volar “sag” of the carpus relative to the ulnar head, analogous to the “caput ulnae” syndrome in rheumatoid arthritis ( Fig. 14.14 ). Generally, these injuries are managed conservatively, unless mechanical instability is present. Open repair has been reported in a few cases and arthroscopic-assisted techniques for suture repair or thermal capsular shrinkage have been described, but experience is limited (see Chapter 17 ).

Class 1D Tear

A class 1D tear is a partial or complete avulsion of the TFCC from the radius, with or without a bone fragment, and may involve one or both radioulnar ligaments. Some reports have confused class 1A and 1D repairs; it is important to reserve the class 1D designation for true radial detachments. Frequently, class 1D injuries are associated with a distal radius fracture and usually respond to accurate fracture reduction of the radius. In the absence of DRUJ instability, symptoms and physical findings are similar to other traumatic TFCC injury types.

Repair of the torn disc to the rim of the radius has been described using open and arthroscopic techniques ( Fig. 14.15 ). A crucial concept underlying a successful repair is to provide a biologic environment conducive to healing by promoting vascular invasion from the bony rim. Various arthroscopic techniques have been described, including the use of specialized jigs. ^{, ,}

Open reduction and repair are indicated for large, displaced avulsion fractures of the radius involving the rim of the sigmoid notch because the bony and ligament restraints are incompetent. Loss of the buttressing effect of the volar rim such as with a displaced palmar lunate facet fracture can be particularly destabilizing to the DRUJ. In most cases, these injuries are components of a more extensive distal radius fracture and are stabilized by fracture reduction and fixation (see Chapter 15 ). Special attention is warranted if DRUJ widening or substantial instability persists after the reduction and stabilization of the radius.

Author’s Preferred Method of Treatment: Open Triangular Fibrocartilage Complex Repair ± Ulnar-Shortening ww for Class 1B Tear

A 5-cm skin incision, centered over the ulnar head, is made between the fifth and sixth extensor compartments ( Fig. 14.16 ). The extensor digiti minimi (EDM) sheath is opened, and the tendon is retracted. The DRUJ is exposed through an “L”-shaped capsulotomy. The longitudinal limb begins at the ulnar neck and extends to the distal edge of the sigmoid notch. Care is taken to preserve the origin of the dorsal radioulnar ligament at the sigmoid notch. The transverse limb is made along the proximal edge of the dorsal radioulnar ligament and extends to the radial margin of the ECU sheath. The capsule is elevated and retracted proximally to expose the ulnar head and neck.

The proximal surface of the TFCC is inspected for injury, especially at its foveal attachment. If the dorsal and palmar radioulnar ligaments are suitable for repair, the distal surface of the articular disc is exposed through a transverse ulnocarpal capsulotomy made along the distal edge of the dorsal radioulnar ligament. A 0.045-inch Kirschner wire is used to create two to three holes in the distal ulna extending from the dorsal aspect of the ulnar neck to the fovea. This site for the holes reduces the irritation from the suture knots compared with the subcutaneous ulnar border. Two horizontal mattress sutures (2-0 absorbable monofilament) are passed from distal to proximal through the ulnar periphery of the TFCC, which lies near the fovea, by entering through the ulnocarpal capsulotomy and exiting through the DRUJ capsulotomy. Using a straight needle or a small suture passer, the sutures are passed through the bone holes. The sutures are tied over the ulnar neck with the joint reduced and the forearm in neutral rotation. The dorsal DRUJ capsule and extensor retinaculum are either closed as separate layers or as a single layer together; the capsule should not be imbricated in order to avoid a potential loss of pronation. The EDM is left superficial to the retinaculum to reduce the risk of peritendinous adhesions. A long-arm splint is applied with the forearm rotated 45 degrees toward the most stable joint position (e.g., supination for dorsal instability). At 2 weeks, the splint is converted to a long-arm cast for 4 weeks, followed by a well-molded short-arm cast for an additional 2 to 3 weeks. A removable splint is used for 4 weeks while motion is regained. Strengthening and resumption of activities are delayed until near-painless motion is recovered. The surgical technique for ulnar shortening osteotomy is described later in this chapter (see pages 585–586).

Acute Distal Radioulnar Joint Instability

Although the radius and the carpus together make up the mobile unit of the DRUJ, dislocation or instability is often (though incorrectly) described by the position of the ulnar head relative to the distal radius. A general classification of acute DRUJ instability can be considered based on anatomic sites of injury or deformity and is useful in guiding treatment.

“Dorsal” DRUJ dislocations (ulna head dorsal) are most common and are caused by hyperpronation and wrist extension, as occurs in a fall on the outstretched hand. Conversely, volar dislocations occur with axial loading through a supinated forearm or from a direct blow to the ulnar aspect of the forearm ( Fig. 14.17 ). Although the most common cause for DRUJ instability is a distal radius fracture, instability after anatomic realignment and fixation of the distal radius is uncommon. Initial radiographic findings of wide displacement of the DRUJ and severe radial shortening are the most important risk factors for persistent DRUJ instability. The radioulnar ligaments can tolerate no more than 5 to 7 mm of radial shortening before one or both ligaments rupture. In the absence of a displaced sigmoid notch fracture, the TFCC typically tears at its ulnar attachments. In most cases, the integrity of the secondary stabilizers of the DRUJ, including the IOM, the DOB, the ECU subsheath, ulnocarpal ligaments, and lunotriquetral interosseous ligament, are preserved, thereby maintaining joint stability. However, as injury severity increases with progressive disruption of the secondary stabilizers, there is progressive instability of the DRUJ. Anatomic reduction of the radius is essential to facilitate DRUJ stability. In a series of articles evaluating young patients with distal radius fractures, unrepaired peripheral tears of the TFCC were a common cause of persistent symptomatic instability. ^,

It is important to evaluate DRUJ stability critically after treatment of a distal radius fracture (see Chapter 15 ). If instability persists after fracture repair, there are several options to promote a stable joint. One option is temporary immobilization of the forearm in the period of maximum stability using a sugar tong splint or long-arm cast. Percutaneous pinning of the ulna to the radius is another option. Typically, this is done with one or two large pins (at minimum of 0.062 inches to resist breakage) driven proximal to the DRUJ from the palpable subcutaneous border of the ulna into the radius. When choosing this treatment, it is important to engage all four cortices of the radius and ulna so that the pins are accessible should one or both break. When treating open radius fractures with concomitant DRUJ instability, external fixation of the wrist with an outrigger attached to the ulna in the position of maximum joint stability may be considered. When severe or bidirectional instability exists, this must be addressed at the time of surgery, either with ulnar styloid fixation for large basilar styloid fractures, correction of residual coronal translation of the radius (see page 577), or open distal radioulnar ligament repair with or without radioulnar pinning.

Ulnar head fractures and sigmoid notch fractures with or without a complex distal radius fracture pose additional challenges for restoring a congruous and stable DRUJ. Although distal radius fractures frequently involve the sigmoid notch, especially the dorsal rim, the extent of involvement is probably underestimated on standard radiographs and characterized more accurately by CT. ^, The clinical implication of residual incongruity of the sigmoid notch has not been studied well, however anatomic and biomechanical studies and case reports suggest that restoration of the sigmoid notch is essential for joint stability. ^,

In Galeazzi fracture-dislocations of the forearm, a class 1B TFCC injury is present almost inevitably, although there may be a spectrum of DRUJ instability ( Fig. 14.18 ). Several studies have demonstrated that the risk of DRUJ instability associated with a Galeazzi-type injury increases with a more distal fracture of the radial diaphysis; fractures in the distal one-third or within 7.5 cm of the distal radius articular surface have a higher risk of injury to the key soft tissue constraints of the DRUJ. ^,

Ulnar Styloid Fractures

In his classic article, Frykman reported that ulnar styloid fractures occurred in approximately 61% of distal radius fractures. Most of these fractures are not associated with DRUJ instability or long-term symptoms. Fractures through the tip of the styloid do not require intervention because they do not cause DRUJ instability and are associated with a good prognosis. Fractures through the styloid base, especially when displaced, are associated with a higher risk of DRUJ instability due to the increased potential for disruption of the inserting fibers of the deep limbs of the radioulnar ligaments.

When the DRUJ remains unstable following anatomic fixation of the radius, fixation of an unstable basilar styloid fracture may restore DRUJ stability through the restoration of radioulnar ligament integrity, provided that the TFCC is not otherwise damaged and that there is no residual radial (coronal) displacement of the radial articular fragment on the shaft. Various methods have been described to fix fractures of the ulnar styloid, including the use of Kirschner wires, tension band wiring, compression screw, variable-pitch headless screws, minifragment plates, and suture anchors ( Fig. 14.19 ). The size of the ulnar styloid fragment influences the selection of fixation options. Soft tissue irritation and or tendinopathy of the ECU is commonly associated with hardware about the distal ulna, and implant-related complications have been reported in up to 48% of cases.

Surgical exposure of the ulnar styloid can be accomplished by a dorsal approach if other procedures are being performed; however, the preferred approach is along the subcutaneous border just volar to the ECU tendon. The dorsal sensory branch of the ulnar nerve (DSBUN) is protected as it courses from volar to dorsal, typically crossing the midline in the “ulnar snuffbox” just distal to the ulnar styloid. The ECU sheath is preserved. The ulnar styloid fracture is identified and interposed soft tissue is cleared from the fracture site to facilitate reduction. When using a tension band technique, one or two oblique Kirschner wires are passed through the tip of the ulnar styloid. A 24-gauge stainless-steel wire or heavy suture is passed around the tip of the wire and through a hole in the ulnar neck in a figure-of-eight fashion. Multiple Kirschner wires or a screw can be used for larger fragments. Suture anchor fixation of the ulnar styloid may minimize the potential to fragment the styloid and to reduce hardware irritation (see Fig. 14.19A ). In this technique, a bone anchor is inserted into the fracture site and is seated well below the fracture line into the ulnar neck. The attached sutures are passed through drill holes in the styloid fragment if it is very large or passed around the fragment if smaller. The sutures are crossed over the subcutaneous surface of the ulna and one end is passed through a transverse drill hole made near the ulnar neck to create a figure-of-eight configuration. When the suture ends are tied, it creates combined interosseous compression and a tension band (see Fig. 14.19A to C ).