AUTHOR AND EDITOR INFORMATION

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• RELEVANT ANATOMY
• Workup
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• Future And Controversies
• Multimedia
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INTRODUCTION

Section 2 of 8  

• Authors and Editors
• Introduction
• RELEVANT ANATOMY
• Workup
• Treatment
• Future And Controversies
• Multimedia
• References

The human wrist joint is a complex arrangement of small bones and ligaments that form a mobile yet stable link from the powerful forearm to the hand. The normally functioning carpus can position the hand precisely relative to the forearm and provides remarkably stable transmission of forces. Motion and stability of the carpus provide the critical foundation for maximum hand function from precise fine motor control to power grip activities.

When the normal mechanics of the wrist are disrupted, the instability of the carpal bones results in weakness, stiffness, chronic pain, and often arthritis if not treated appropriately. Although the early clinical and radiographic findings may be subtle, an understanding of wrist kinematics and instability patterns can facilitate early diagnosis and management. Unfortunately, selecting the optimal treatment remains a difficult judgment in most cases.

Linscheid et al described traumatic carpal instability in 1972. Since the early reports, anatomic and biomechanical studies have provided a foundation for understanding carpal motion, stresses, and pathologic instability. Building on these studies, various models have been suggested to explain the remarkable strength and mobility of this complex joint and the predictable patterns of failure.

This article presents the current understanding of pathologic carpal instability, the common classification patterns, and early treatment options that may avoid protracted dysfunction. Appropriate hand therapy is essential to maximize recovery but requires an appreciation of the limitations of carpal instability dysfunction and the goals of various treatment options.

Problem

Carpal instability is defined as any malalignment of the carpus. This may be evident on plain radiography as a static deformity; alternatively, the situation may be a dynamic one, which becomes evident only when external forces are placed on the wrist.

The malalignment may appear after a single traumatic event or may be secondary to chronic attenuation of supporting ligaments after a traumatic event or secondary to an underlying disease process (eg, rheumatoid arthritis, pseudogout).

Frequency

In 1975, Dobyns et al reviewed their experience and found that 10% of all carpal injuries resulted in instability.

In 1988, Jones evaluated 100 consecutive patients with wrist sprains by using dynamic radiography (clenched-fist views) and found that 19 had an increased scapholunate gap.

The incidence of carpal instability that is associated with other specific fractures is relatively high. Reviewing 134 distal radius fractures, Tang in 1992 found radiographic evidence of carpal instability in 30% of the cases.

Geissler and Freedland prospectively reviewed 60 displaced intra-articular distal radius fractures that were being treated with arthroscopic assisted reduction and internal fixation (Geissler, 1996). They found 43% had concomitant tears in the fibrocartilage complex, while 32% also had tears in the scapholunate ligament.

Weber reviewed 36 patients with acute scaphoid waist fractures and found that 28% had a dorsal intercalated-segment instability (DISI) deformity (Weber, 1980).

Etiology

Carpal instability results from an injury to one or more ligamentous or bony constraints in the wrist. Depending on the force, rate, and point of impact and on the position of the wrist, a fall on an outstretched wrist can result in a range of injuries. This spectrum includes wrist sprains, distal radius fractures, and fractures to the scaphoid and other carpal bones. This type of trauma can also result in injury to one or more ligamentous structures in the wrist, causing carpal instability. Perilunate instability is described as progressing from the scapholunate and the capitolunate to the lunotriquetral joint.

Using a cadaveric trauma model, Mayfield et al observed progressive injury patterns when the wrist was loaded in extension, ulnar deviation, and carpal supination (Mayfield, 1980). This perilunar instability is divided in 4 stages (see Image 5). Stage I refers to injury to the scapholunate interosseous ligament (SLIL). Further trauma results in dorsal subluxation of the capitate relative to the lunate, or stage II. As the load increases, the lunotriquetral interosseous ligament (LTIL) is injured, causing a perilunate dislocation in stage III. Finally, stage IV is characterized by dislocation of the lunate from the radiolunate fossa.

However, if the carpus is pronated and the hypothenar area is struck first, an ulnar traumatic pattern may be observed. Specifically, disruption of the ulnotriquetral ligament complex and the LTIL occurs (Stanley, 1994). As the triquetrum no longer holds the lunate, it falls into a flexed position because of pressure from the capitate and its connection with the scaphoid. With attenuation or injury to the dorsal intercarpal ligament, a volar intercalated-segment instability (VISI) pattern ensues; this can be visualized on lateral radiography. An LTIL tear most commonly results in a VISI deformity.

In addition to a direct loading type of trauma, rotational force to the wrist can also result in ligamentous injuries, eg, the forces that occur when holding a power drill while the drill bit is jammed. This type of trauma can result in injuries to the LTIL and ulnar-triquetral ligament complex and result in the lunotriquetral instability (Ruby, 1996).

Some instability patterns arise after chronic attrition of supporting ligaments. One traumatic event may result in some subtle ligamentous injury but no clear instability initially. However, over time, continued normal daily loading of the wrist can result in symptomatic instability. An example is seen with scaphoid fractures, where a DISI deformity tends to appear late after the initial traumatic event.

Supporting ligaments can also be important in preventing carpal instability in the presence of other significant ligamentous injury. For example, many cadaveric studies have shown that isolated sectioning of the SLIL does not result in frank radiographic scapholunate gap or dissociation.

In 1986, Johnson and Carrera described a midcarpal instability in which the capitate dorsally subluxes out of the cup of the lunate during a fluoroscopic dorsal-displacement stress test. This is associated with a painful snap or click that reproduces the patient's symptoms. They attributed the cause of this instability to attenuation of the radioscaphocapitate ligament after prior trauma.

Pathophysiology

Column theory of carpal kinematics

Over the past several decades, many theoretical models have been described to explain the complexities of carpal motion.

The column theory, as Navarro first proposed in 1935, recognized some motion between the bones of the proximal row and divided the wrist into 3 columns: the radial column, which consists of the scaphoid, trapezium, and trapezoid; the central column, which includes the lunate and capitate; and the ulnar column, which consists of the triquetrum and hamate. Although this theory does not explain the coupled motions that occur within the proximal and distal rows, it does help explain the load patterns seen through the wrist.

Row theory of carpal kinematics

The row theory is based on the fact that the proximal and distal rows work as 2 separate functional units. Gilford et al expanded on this row theory by noting that flexion-extension motions of the wrist are accomplished by relatively equal contributions from the radiolunate and lunocapitate joints and proposed that each row rotates around a single center of rotation near its proximal articular surface (Gilford, 1943) (see Image 3). They also emphasized the instability of such a 2-link system under load and the tendency for the system to crumple without a stabilizing mechanism. They believed that the scaphoid should be considered part of both rows and underscored its importance as a bridge, or tie rod, to stabilize an otherwise unstable arrangement (see Image 4).

Because no tendons insert on the scaphoid, lunate, and triquetrum, in 1972 Linscheid et al considered the scaphoid, lunate, and capitate to be an intercalated segment interposed between the articular surfaces of the radius and ulna and the rigidly bound distal carpal row. Muscle contractions impart rotational moments to the proximal row through the distal row, and carpal motion is governed by a combination of ligamentous and articular constraints. The strong interosseous ligaments between the 3 proximal carpal bones enable them to move in a synchronized fashion during wrist motion. The scaphoid, lunate, and triquetrum rotate in the same primary direction, albeit to different magnitudes, during any motion of the hand.

A specific example of this interaction is during radial-ulnar deviation. As the wrist ulnarly deviates, the entire proximal row extends. Conversely, the entire proximal row flexes as the wrist radially deviates. Although the mechanism by which this occurs is not entirely clear, most authors believe that this motion is a result of a combination of ligamentous constraints and carpal articular geometry between the proximal intercalated row and the distal row.

A theory that Linscheid and Dobyns proposed in 1989 is that the distal pole of the scaphoid flexes because of pressure by the trapezium and trapezoid during radial deviation. The rest of the proximal row then flexes because of the strong interosseous ligaments connecting the lunate to the scaphoid and the triquetrum to the lunate.

In another theory, Weber proposed that the unique helicoidal shape of the triquetrohamate articulation forces the distal row to translate dorsally and the triquetrum to tilt into extension as the wrist ulnarly deviates (Weber, 1984). Dorsal translation of the distal row contributes to an extension moment on the proximal row. The opposite occurs during radial deviation with palmarly directed force on the proximal row, causing flexion.

Combined column and row theory of carpal kinematics

Some have theorized that an individual's carpal kinematic behavior can be explained by some combination of both the columnar and row theories.

Craigen and Stanley analyzed radiographs of 52 normal wrists and found that, from ulnar to radial deviation, the amount of scaphoid shortening and ulnar translation of the scaphoid varies in a normal distribution (Craigen, 1995). If the scaphoid shortens more, it translates less. By their interpretation, a column-type wrist shows greater shortening. They also found females were more likely to have greater scaphoid shortening and less translation.

This individual variation in kinematic behavior was also supported by Garcia-Elias et al who attributed it to the individual variation of laxity (Garcia-Elias, 1995). They examined 60 healthy volunteers and found that physiologic differences in wrist ligamentous laxity affected carpal kinematics. In radial-ulnar deviation, the scaphoid of very lax wrists moved preferentially in the sagittal plane (flexion-extension), whereas in the more rigid wrists, the scaphoid moved preferentially in the frontal plane (radio-ulnar deviation).

Oval-ring theory of carpal kinematics

The oval-ring theory functionally depicts the carpus as a transverse ring formed by proximal and distal rows and joined by 2 physiologic links (Lichtman, 1981). The radial link is the mobile scaphotrapezial joint, while the ulnar link is the rotatory triquetrohamate joint.

Clinical

Diagnosis

The diagnosis of carpal instability in patients with obvious fracture and carpal instability patterns on radiography is sometimes relatively easy. Making the diagnosis in patients with subtle carpal instability can be more difficult. These patients often present with a history of a traumatic event. Noting the position of the wrist at the time of injury and determining the resultant force vector is extremely valuable.

Patients may have pain; if so, its location can be important when making the diagnosis. They may also have weakness and feelings of giving away. They may have clicking or snapping sensations on certain motions or upon loading the wrist.

Physical examination

As in many situations, physical examination starts with palpation. Nearly every critical ligament on the wrist can be palpated. Point tenderness over specific carpal ligaments such as the SLIL or LTIL may represent injuries to those ligaments. Pain at the extremes of motions may be present. Many dynamic maneuvers have been described to diagnose specific carpal instabilities.

Scaphoid shift test

One of the most common tests is the scaphoid shift test, as Watson described in 1997 (see Image 6). In this test, the examiner's thumb is placed on the scaphoid tuberosity of the volar aspect of the wrist. Pressure is applied to the tuberosity as the wrist is passively brought from ulnar to radial deviation. This pressure attempts to block normal scaphoid flexion. In theory, if the SLIL is torn and scapholunate instability is present, the proximal scaphoid subluxates dorsally over the rim of the radius. A positive result is when a painful "clunk" is elicited as the scaphoid reduces back into the radial scaphoid fossa as the thumb pressure is released.

Easterling and Wolfe have shown that results of this test may be positive in a significant number of asymptomatic healthy wrists (Easterling, 1994). Therefore, examination of the contralateral uninjured wrist is critical. In addition to the classic definition of a positive result, some surgeons believe that just pain and no subluxation with this maneuver may define a lesser scapholunate instability, such as a partial tear of the SLIL.

Maneuvers to diagnose lunotriquetral instability

A few maneuvers have been described that can help diagnose lunotriquetral instability. Distinguish lunotriquetral instability from a tear in the triangular fibrocartilage.

The Kleinman shear test (see Image 7) is performed with the wrist in neutral position (Kleinman, 1990). The examiner's contralateral thumb is placed over the dorsal lunate while the ipsilateral thumb loads the pisotriquetral joint with a dorsally directed force. A shear force is created across the lunotriquetral joint. A positive result is when this maneuver produces pain.

The Reagan shuck test (see Image 8) is similar, except the examiner's thumb and index finger grasps the whole pisotriquetral unit (Reagan, 1984). The contralateral thumb and index finger hold the lunate. The lunotriquetral joint is stressed by applying dorsally directed force with one hand and volarly directed force with the other hand. This force is switched in the opposite directions in both hands. This creates a shear stress at the lunotriquetral joint, and if painful, the result is positive.

Linscheid described a compression test (see Image 9) in which the examiner uses his thumb to apply a load in the radial direction at the ulnar border of the triquetrum (Linscheid, 1984). This loading results in a compression force across the lunotriquetral joint. If this maneuver produces pain, the result is considered positive.

Lichtman et al described a pivot shift test for midcarpal instability (Lichtman, 1981). This maneuver is a combination ulnar deviation, axial compression, and pronation of the wrist. A positive result is when this maneuver results in a painful wrist click.

Another test for midcarpal instability (as described above) is a dorsal-displacement stress test (Johnson, 1986). Under fluoroscopic control, a positive result is when the capitate subluxates dorsally compared with the lunate and when the patient experiences a painful snap or click.

RELEVANT ANATOMY

Section 3 of 8  

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Carpal bones

The wrist contains 8 carpal bones. Anatomically and functionally, these 8 carpal bones are divided into proximal and distal rows. The proximal row is formed by the scaphoid, the lunate, and the triquetrum. Although the pisiform is anatomically located on the palmar surface of the proximal row, it is a sesamoid bone within the flexor carpi ulnaris tendon. The pisiform does not contribute to the kinematics of the proximal row. The trapezium, the trapezoid, the capitate, and the hamate form the distal row.

Carpal ligaments

Multiple ligaments help stabilize the wrist to the forearm and hand. Extrinsic ligaments span the radiocarpal joint, while intrinsic ligaments connect between individual carpal bones. An important extrinsic ligament on the dorsal aspect of the wrist is the dorsal radiocarpal ligament (see Image 1). This ligament originates on the radius and has minor attachments to the lunate while the bulk of the attachment is on the triquetrum. There are many more extrinsic ligaments on the volar aspect of the wrist. From radial to ulnar, they include the radioscaphocapitate, radioscapholunate, short radiolunate, long radiolunate, ulnolunate, and ulnotriquetrum ligaments (see Image 2).

The intrinsic ligaments consist of stout ligaments that originate and insert within the carpus. The 2 most important intrinsic ligaments include the SLIL and the LTIL. The SLIL, which joins the scaphoid and the lunate, is probably one of the most important ligaments in the wrist. Injury of the SLIL can result in one of most common causes of carpal instability: scapholunate dissociation.

The SLIL is a C-shaped ligament that is divided into 3 separate components (Berger, 1982):

• The proximal component is made up of fibrocartilage and has minimal mechanical strength.
• The dorsal SLIL (dSLIL) and palmar SLIL (pSLIL) components have true ligament characteristics; the dSLIL is stouter than the pSLIL.
• The LTIL connects the lunate and triquetrum.

Similar to the SLIL, the LTIL is C-shaped and has 3 separate components. In contrast to the SLIL, its palmar component is stouter than the volar component.

Two intrinsic ligaments that cross from the proximal to the distal carpal row are the scaphocapitate and the dorsal intercarpal ligaments. The scaphocapitate ligament crosses the volar midcarpal joint and attaches from the distal pole of the scaphoid to the body of the capitate. Across the dorsal midcarpal joint, the dorsal intercarpal ligament originates from the triquetrum, attaches to the scaphoid dorsal ridge, and then inserts into the dorsal distal third of the scaphoid and to the scaphoid-trapezium ligament.

WORKUP

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• RELEVANT ANATOMY
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• Future And Controversies
• Multimedia
• References

Imaging Studies

• Standard radiographic examination of the wrist should include a posteroanterior (PA) view in neutral rotation and also lateral views. The symptomatic and asymptomatic wrist should be evaluated
• • Static instability patterns can be seen with these radiographs.
  • Additional radiographs, such as a PA grip, PA maximum radial deviation, PA maximum ulnar deviation, lateral maximum flexion, and lateral maximum extension views, can also be obtained and can help diagnose dynamic instability.
• To determine scapholunate dissociation, the scapholunate gap can be measured on PA and PA grip radiographs. However, obtaining a PA view that clearly shows the scapholunate gap without some bony overlap can be difficult. Findings should always be compared side-to-side.
• • Kindynis et al suggested angling the x-ray tube to obtain a clearer view of the scapholunate joint and to measure the space at the level of the midportion of the flat ulnar facet of the scaphoid (Kindynis, 1990).
  • The amount of gap that is diagnostic of scapholunate dissociation is not agreed upon. Many authors define the gap to be pathologic if it is greater than 3 mm (Bednar, 1993; Linscheid, 1984). In 1991, Cautilli and Wehbe measured the gap on 100 normal radiographs and found a mean distance of 3.7 mm (range, 2.5-5 mm).
  • Given the wide range, comparing the injured wrist with the contralateral uninjured wrist is crucial before scapholunate dissociation is diagnosed.
• If the lunate is dorsiflexed more than 15º than the capitate on lateral radiography, a diagnosis of a DISI deformity is confirmed. Conversely, VISI is defined if the lunate if volarly flexed more than 15º.
• • A DISI deformity is associated with scapholunate instability, while a VISI deformity is associated with lunotriquetral instability.
  • In addition, the scapholunate angle can be measured on lateral radiography. In scapholunate instability, the scaphoid tends to assume a volarly flexed posture. As such, the scapholunate angle, which normally measures 30-60º (average, 46º), increases to more than 70º (Linscheid, 1972).
  • Conversely, in lunotriquetral instability, the lunate is usually palmarly flexed, and the scapholunate angle can be less than 30º (Bednar, 1993).
• McMurty et al defined a method to determine ulnar translocation on PA radiography (McMurty, 1978) (see Image 10).
• • The distance between the center of the capitate and a line extending from the intermedullary axis of the ulna is divided by the length of the third metacarpal.
  • McMurty et al found that this ratio is 0.30 ± 0.03 in normal wrists but smaller in patients with ulnar translocation.

Other Tests

• Other studies include fluoroscopy, wrist arthrography, CT scanning, MRI, and ultrasonography.
• • Because the false-positive rate is relatively high for arthrography (especially in those >40 y), some have suggested comparing images of the injured wrist with images in the contralateral uninjured wrist (Herbert, 1990).
  • Communication between the different compartments of the wrist may not necessarily be a result of trauma, but rather a result of age-related degenerative changes (Viegas, 1987).
• Arthroscopy remains the criterion standard in diagnosing specific ligament injuries in the wrist (Cooney, 1993; Kelly, 1990; Roth, 1986).
• • Both the radiocarpal and midcarpal joints should be evaluated.
  • More importantly, surgical management can take place in the same setting.

Staging

Many schemes have been described to classify the different degrees of carpal instability.

Linscheid et al described the easiest and one of the earliest classification schemes (Lichtman, 1981; Linscheid, 1972). They separated most instabilities into 2 groups depending on the orientation of the proximal row relative to the distal row. In their classification, the orientation of the proximal row is defined by the position of the lunate. The capitate is used to define the orientation of the distal row because it is most easily seen on lateral radiography. Thus, if the lunate is dorsally flexed relative to the distal row (capitate) on lateral radiography, the instability is considered a DISI. The proximal row is the intercalated segment because no tendons directly insert on it. Similarly, a palmarly flexed lunate relative to the distal row is defined as a VISI.

These 2 patterns have been further classified as dissociative and nondissociative types. The dissociative type occurs when the injury results in instability between adjacent carpal bones within a row. For example, scapholunate instability is most commonly associated with a dorsiflexed lunate; this pattern is called a DISI deformity, dissociative type. A nondissociative type occurs when the DISI or VISI pattern is secondary to an injury that results in instability between rows. This nondissociative pattern has also been called midcarpal instability.

Two patterns that do not fit this classification include ulnar translocation and dorsal subluxation of the carpus. Ulnar translocation is defined as an ulnar shift of the entire carpus relative to the radius. This type of instability is seen in wrists with rheumatoid arthritis after chronic attrition of radial-sided extrinsic ligaments and bony changes. Dorsal subluxation describes a dorsal shift of the entire carpus relative to the radius. This pattern, also called adaptive carpal instability, is often seen after malunion of distal radius fractures where the radius has lost its normal volar tilt.

Two other adjectives commonly used in classifying carpal instabilities are static and dynamic. A static instability is one that can be clearly recognized on routine radiography by a loss of the normal alignment (Taleisnik, 1980). A dynamic instability is any instability that requires external forces placed on the carpus to elicit an instability pattern. Therefore, the diagnosis of dynamic instability relies on other means, such as dynamic radiography, physical examination with provocative maneuvers, and/or arthroscopic evaluation.

TREATMENT

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Surgical therapy

Treatment of carpal instability is complex and usually specific to the type of instability and is certainly controversial. A full detailed review of all treatment options is beyond the scope of this article. To simplify this discussion, each treatment is summarized under specific types of instabilities: scapholunate, lunotriquetral, and midcarpal instability and also ulnar translocation.

Scapholunate instability

There is no consensus on the appropriate treatment of scapholunate instability. The treatment is usually specific to the different stages or degree of injury. Partial tears of the SLIL are thought to represent occult or predynamic instability (Watson, 1997; Wolfe, 2001). For these injuries, most recommend an initial trial of splinting and/or casting (Whipple, 1995; Wolfe, 2001). Arthroscopic debridement with or without pinning can be an option in these patients in whom initial conservative treatment is unsuccessful (Kozin, 1999; Ruch, 1996).

A complete tear of the SLIL may not by itself lead to an acute scapholunate gap or diastasis. Biomechanical studies support the concept that additional supporting ligaments must also be injured for this gap to be apparent. In addition, attenuation of these ligaments may lead to a diastasis that is observed late with respect to the initial injury date. In either case, a complete tear of the SLIL is suggested in the presence of the significant scapholunate diastasis on static or dynamic radiography.

With complete SLIL tears, cast immobilization does not reduce or prevent scapholunate diastasis (Wolfe, 2001). Significant force occurs at the scapholunate interval on wrist loading. Options for acute management of these tears include direct repair with or without dorsal capsulodesis or arthroscopic debridement, reduction, and pinning. Some recommend the latter treatment for acute ( <3 mo) tears that have evidence of instability on static radiography (gap <3 mm or DISI) (Kozin, 1999; Ruch, 1996).

A retrospective study by Weiss et al showed that 33% of patients who underwent arthroscopic debridement, reduction, and pinning of complete SLIL tears had persistent pain and required further surgery (Weiss, 1997). Most reconstructive wrist surgeons recommend direct repair for acute ( <6 wk) tears if a sufficient SLIL remnant is present (Linscheid, 1993; Wolfe, 2001). Lavernia et al reported on dorsal capsulodesis to augment a direct repair and demonstrated good results in 81% of their patients (Lavernia, 1992). Satisfactory results were seen in patients, even as long as 3 years after injury.

In patients with unrepairable SLIL but with a reducible scapholunate interval and without degenerative changes, an indirect or direct ligament reconstruction has been advocated. Typically, the presentation is chronic, and the SLIL is usually not repairable. Indirect ligament reconstruction is based on stabilizing the scaphoid to prevent the rotatory subluxation that often occurs in scapholunate instability.

Some indirect ligament reconstructions also attempt to close the scapholunate gap. The most widely used indirect ligament reconstruction is the Blatt dorsal capsulodesis (Blatt, 1987). This technique uses a flap of dorsal capsule to tether the scaphoid tuberosity to retard scaphoid flexion. Because the flap is attached to the distal radius, wrist flexion is significantly reduced by 20% on average.

More recent techniques attempt to avoid limitation of flexion by not tethering the scaphoid to the radius (Dagum, 1997; Slater, 1999). Several techniques have been described. As Berger et al initially proposed (Berger, 1995), a strip of dorsal intercarpal ligament detached from the triquetrum can be used to tether the distal scaphoid pole to the lunate or radius (see Image 11). Slater et al described the use of a portion of the dorsal intercarpal ligament that attaches to the distal scaphoid and trapezoid and reinserts it to the distal pole of scaphoid tuberosity (Slater, 1999). These authors believe that this technique not only serves to limit scaphoid flexion but also reduces the scapholunate gap more effectively than the Blatt capsulodesis.

Direct ligament reconstruction is indicated when the SLIL is not directly repairable, when the scapholunate dissociation is reducible, and when no evidence of degenerative arthritis is observed. Some also believe that evidence of carpal instability (DISI) should be absent (Wolfe, 2001). Techniques for this approach involve either a tendon to reconstruct the SLIL or a bone-ligament-bone construct (Almquist, 1991; Brunelli, 1995; Hofstede, 1999; Palmer, 1978; Wolfe, 2001). All of these techniques have had some degree of success, but they are not universally durable. They require a long period of wrist immobilization and result in some loss of final wrist motion.

Brunelli and Brunelli described one such technique that shows promise (Brunelli, 1995). Their technique uses a strip of the flexor carpi radialis (FCR) and weaves it through the scaphoid. The tendon is also sutured across the scapholunate interval. Limited intercarpal fusions are indicated when carpal instability (DISI) is present without gross evidence of degenerative changes at the radiocarpal joint (Wolfe, 2001).

Fusions that have been described involve the scaphocapitolunate (Rotman, 1993), the scaphotrapezial trapezoid (Echenrode, 1986; Kleinman, 1990; Kleinman, 1982; Peterson, 1967; Watson, 1980), the scaphocapitate (Pisano, 1991), and the scapholunate (Hom, 1991). Viegas et al found that the scaphocapitolunate and scapholunate fusions distributed the load more uniformly across both the scaphoid and lunate fossae than the scaphotrapezial trapezoid or scaphocapitate fusions (Viegas, 1990).

When arthritic change (advanced scapholunate collapse) or a wide, irreducible scapholunate gap is present, options include a proximal row carpectomy or scaphoid excision and fusion of the lunate, triquetrum, capitate, and hamate (4-corner fusion). Significant degenerative changes at the proximal hamate or of the lunate fossa are a contraindication to proximal row carpectomy. Once pancarpal arthritis involves the lunate fossa, the best surgical option may be total wrist fusion.

Lunotriquetral instability

There is no consensus on the appropriate treatment of lunotriquetral instability. Treatment algorithm can probably be based on the type and age of the injury. A partial tear of the LTIL may be clinically suspected and should not have the associated VISI deformity. Reagan et al recommend a period of immobilization for acute injuries (Reagan, 1984). Others have recommended arthroscopic evaluation and percutaneous pinning (Ruby, 1996).

For patients in whom conservative treatment fails, lunotriquetral dissociation direct repair with or without augmentation has been advocated. Repairing the LTIL by using an open technique to reattach it back to the site of its avulsion (usually from the triquetrum) has good results (Reagan, 1984). Augmentation is usually in the form of a capsulodesis. The goal of capsulodesis is to prevent excessive flexion of the proximal row by imbricating the dorsal radiotriquetral ligament (Ruby, 1996).

For patients who present late after their initial injury, surgical management includes techniques of capsulodesis, ligament reconstruction, arthrodesis, or ulnar shortening. Shin et al have described a ligament reconstruction by using a distally based strip of the extensor carpi ulnaris tendon (Shin, 2001). Because some patients with symptomatic lunotriquetral instability also have ulnar impaction syndrome, Ruby treats these patients with chronic lunotriquetral tears with ulnar shortening alone, especially if they have positive or neutral ulnar variance (Ruby, 1996). Ulnar shortening is believed to tighten the volar ulnotriquetral and ulnolunate ligaments, indirectly improving lunotriquetral stability. However, this treatment may be ill advised in the patient with a VISI deformity because tightening of these volar ligaments may exacerbate their deformity.

As a treatment for lunotriquetral instability, lunotriquetral fusion is controversial. Pin et al used a compression screw and achieved fusions in all 11 patients in their study (Pin, 1989). Three patients (27%) had persistent pain, and the 11 patients achieved a postoperative grip strength of only 59% compared with the uninjured side.

Kirschenbaum et al reported results after lunotriquetral fusion that were slightly better (Kirschenbaum, 1993). Among 14 patients, only 1 had persistent pain, and the average grip strength was 94% compared with the contralateral side. In 2 patients, fusion did not occur: One underwent repeat fusion, while the other was not symptomatic. Wrist motion was also well preserved in their series: about 80-85% compared with the uninjured wrist.

Despite the results of these 2 studies, others have shown nonunion rates as high as 57%, persistent pain in 52%, and decreased in wrist motion in 31% (Shin, 2000).

Instead of lunotriquetral fusion, others have recommended lunotriquetrohamate (Bednar, 1993) or triquetrohamate (Stanley, 1994) fusions. Further studies are needed to fully evaluate these fusions.

Midcarpal instability

Johnson and Carrera advocated tightening the radiocapitate ligament in patients who had a positive fluoroscopic dorsal-displacement stress test (Johnson, 1986). Their technique consists of tethering the middle portion of the radiocapitate ligament to the radiotriquetral ligament to close the space of Poirier. Slight extension of the wrist is lost after this procedure.

Lichtman et al reviewed 13 patients (15 procedures) who underwent surgery for midcarpal instability over an 8-year period. They found that all 6 of the limited midcarpal arthrodeses were successful, whereas 6 of 9 soft tissue reconstructions failed (Lichtman, 1993).

Carpal instability that results from distal radius malunion can be effectively treated by correcting the malalignment of the radius. Opening wedge osteotomy of the radius at the location of the deformity to correct radial malalignment usually also corrects the carpal instability.

Ulnar translocation

In the rheumatoid wrist, ulnotranslocation is usually effectively treated with radiolunate fusion (Chamay, 1983). Significant arthritis at the radioscaphoid joint may also require radioscaphoid fusion. Total wrist fusion is probably the best option significant midcarpal arthrosis is present as well.

FUTURE AND CONTROVERSIES

Section 6 of 8  

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• RELEVANT ANATOMY
• Workup
• Treatment
• Future And Controversies
• Multimedia
• References

Although the diagnosis of wrist instability has been present for nearly 4 decades, the treatment of wrist instability remains a hotly debated topic among hand surgeons. As a result, new and innovative methods of treatment are compared to time-tested procedures, resulting in improved understanding of wrist instability.

MULTIMEDIA

Section 7 of 8  

• Authors and Editors
• Introduction
• RELEVANT ANATOMY
• Workup
• Treatment
• Future And Controversies
• Multimedia
• References

Media file 1:  Dorsal carpal ligaments. Copyright Mayo Clinic, used with permission of Mayo Foundation.
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Media file 2:  Volar carpal ligaments. Copyright Mayo Clinic, used with permission of the Mayo Foundation.
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Media file 3:  The wrist is a simple link between the proximal and distal rows. The pivot point is at the center of rotation of the capitate and lunate. This joint, without other supporting structures, is stable only in tension. It is unstable in compression, as this figure depicts, and tends to collapse.
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Media file 4:  The scaphoid acts like a bridge between the proximal and distal row and protects the link from collapsing.
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Media file 5:  Mayfield perilunate instability pattern. Copyright Mayo Clinic, used with permission of the Mayo Foundation.
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Media file 6:  Watson scaphoid shift test.
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Media file 7:  Kleinman shear test.
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Media file 8:  Reagan shuck test.
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Media file 9:  Linscheid compression test.
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Media file 10:  McMurty ulnar translation measurement.
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Media file 11:  Mayo dorsal intercarpal (DIC) capsulodesis. Copyright Mayo Clinic, used with permission of Mayo Foundation.
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REFERENCES

Section 8 of 8

• Authors and Editors
• Introduction
• RELEVANT ANATOMY
• Workup
• Treatment
• Future And Controversies
• Multimedia
• References

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Article Last Updated: Nov 22, 2005