Hand Surgery
1st Edition

26
Lunotriquetral Joint
Richard A. Berger
Lunotriquetral (LT) disorders fall under the broad and often vexing category of ulnar-sided wrist pain. Included in this symptom group are LT sprains, tears, and dissociation; triangular fibrocartilage complex disorders; extensor carpi ulnaris tendonitis or subluxation; pisotriquetral joint arthrosis; midcarpal instability; ulnar impaction syndrome; ulnar styloid impingement syndrome; inflammatory or crystalline arthropathy; ulnar neurovascular disorders; and even hamate hook or dorsal triquetral shear fractures. One of the problems with LT disorders is that the vast majority of patients who present with some stage of LT dissociation have normal imaging studies. Although LT dissociation does not have the predisposition for development of degenerative changes in the carpus, it can have a devastating effect on carpal mechanics, particularly if it advances to a stage of volarflexed intercalated segment instability (VISI), which is described in the following discussion, that can be difficult to correct. Even without this progression, the patient with chronic ulnar-sided wrist pain experiences significant ongoing disability with the potential for adverse effects on all upper extremity functions. Therefore, it is incumbent on the treating physician to effectively work through the differential diagnosis to develop the most effective treatment plan. As is discussed in the following sections, this demands a careful history acquisition and physical examination. This, combined with knowledge of normal joint mechanics, offers the patient the best outcome possible.
ANATOMY
Joint Anatomy
The LT joint is part of the proximal carpal row, forming the articulation between the medial surface of the lunate and the lateral surface of the triquetrum (1). The mutually articulating surfaces of the lunate and triquetrum are nearly planar. In the neutral wrist position, the orientation of the plane of the joint is approximately 20 degrees oblique to the sagittal plane of the forearm but is nearly orthogonal to the frontal plane.
The LT joint is also under the influence of the radiocarpal and midcarpal joints. The radiocarpal joint is a hybrid articulation between the proximal surfaces of the lunate and the triquetrum, articulating with the lunate fossa of the distal radius and the triangular disc. Under normal circumstances, no more than 50% of the lunate articulates with the triangular disc. The proximal surfaces of the triquetrum and the lunate are convex. Distally, the relevant midcarpal articulation is between the distal articular surfaces of the lunate and triquetrum and the proximal surfaces of the capitate and hamate. In 49% of adults, the proximal surface of the hamate articulates with the lunate. In these individuals, a sagittal ridge divides the distal surface of the lunate into radial and ulnar fossae (2). The geometry of the distal surface of the lunate is otherwise concave in the sagittal and coronal planes. The geometry of the distal surface of the triquetrum is best described as helicoid.
Ligament Anatomy
The most critical aspect of the LT ligament complex is the lunotriquetral interosseous ligament (LTIL) (3,4). The LTIL is C shaped with continuous dorsal, proximal, and palmar regions (Fig. 1). The distal aspect of the LT joint is free from ligamentous connection. Microdissection and histologic analyses have demonstrated that the palmar region of the LTIL is the thickest and possesses the architecture of a true capsular ligament. The dorsal region, also a true capsular ligament, is thinner than the palmar region. The proximal region is composed of fibrocartilage, with a wedge-shaped cross-section geometry, which is reminiscent of a meniscus.
Extrinsic capsular ligaments are also significantly involved in the LT mechanism. On the dorsal surface, the dorsal radiocarpal (DRC) ligament has a proximal attachment to the dorsal rim of the distal radius, essentially from the level of Lister’s tubercle to the ulnar extreme of the distal radius. It passes obliquely distally and ulnarly, narrowing into a trapezoidal shape. It has a deep layer that attaches to the lunate and then proceeds to cover the dorsal LTIL before terminating into the dorsal tubercle of the triquetrum. At this same point, the dorsal intercarpal ligament attaches and passes
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radially, essentially as a two-band ligament. The most proximal band shares fibers with the dorsal regions of the LTIL and scapholunate interosseous ligaments and attaches along the dorsal ridge of the scaphoid. The distal band passes over the midcarpal joint to attach primarily into the dorsal cortex of the trapezoid (5,6 and 7).
FIGURE 1. Drawing of the lunotriquetral ligament complex from a dorsal and ulnar perspective, after excision of the triquetrum. The dotted line represents the proximal and dorsal regions of the lunotriquetral ligament. C, capitate; H, hamate; L, lunate; LTIp, palmar lunotriquetral ligament; TFCC, triangular fibrocartilage complex; UC, ulnocapitate ligament.
Palmarly, the entire LT joint complex is supported by a substantial ligament construct. The lunate is supported by a thick, longitudinally oriented ligament from the palmar cortex of the lunate fossa, the short radiolunate ligament. This is continuous with a similar ligament that is called the ulnolunate ligament, which arises from the palmar radioulnar ligament to attach to the ulnar one-half of the palmar cortex of the lunate. The ulnotriquetral ligament arises proximally from the palmar radioulnar ligament and the ulnar styloid process. It passes distally to attach to the proximal edge of the palmar surface of the triquetrum and the entire medial tubercle of the triquetrum. In approximately 90% of normal adults, the ulnotriquetral ligament is split distally to form an orifice that connects the radiocarpal and pisotriquetral joints (8). Palmar (superficial) to the ulnolunate and ulnotriquetral ligaments is the ulnocapitate ligament. It arises from the ulna at the fovea, where the dorsal and palmar radioulnar ligaments also attach. It reinforces the ulnolunate and ulnotriquetral ligaments before passing anterior to the LT joint, where it interdigitates with the fibers of the palmar region of the LTIL.
Distally, there are two strong midcarpal capsular ligaments that arise from the distal edge of the triquetrum: the triquetrocapitate and triquetrohamate ligaments. The distal edge of the palmar horn of the lunate serves as an attachment of the arcuate ligament that is formed by the radio-scaphocapitate and ulnolunate ligaments.
MECHANICS
Kinematics
The LT joint is a critical component of the proximal carpal row kinematic chain (1). Overall, the kinematics of each of the proximal row bones is similar; however, notable motion is present between each proximal carpal row bone (9,10 and 11). This is in distinction to the distal carpal row bones, which essentially form a singe fixed bone, with less than 5 degrees of mutual motion between the bones. Overall, the distal row bones move with the hand, such that, as the hand rotates into dorsiflexion, so does the distal row.
There are several axes of motion that are defined in the wrist, including flexion-extension motion, radial-ulnar deviation, and the so-called dart-throw axis, which moves the wrist from radial deviation-extension to ulnar deviation-flexion (12,13). In reality, there are an infinite number of positions of the wrist and, hence, axes of motion, but most studies identify the location of the centers of rotation of the wrist in the head of the capitate.
The proximal row bones behave in a different fashion from the distal row bones. First, there is significant intercarpal motion between the proximal row bones, in spite of the fact that, in general, they move in the same direction. Second, during wrist radial-ulnar deviation, the proximal row bones demonstrate conjunct rotation. This means that the principal direction of motion of the proximal row bones during radial deviation is palmar flexion and the principal motion during wrist ulnar deviation is dorsiflexion. This does not imply that other planes of motion do not exist; it simply defines the principal direction of motion. During wrist palmar flexion and dorsiflexion, the direction of motion of the proximal row bones is similar to that of the distal row bones. The conjunct rotation phenomenon is believed to be due, in large part, to the helicoid nature of the triquetrohamate articulation. As the hamate pole contacts the distal surface of the triquetrum during ulnar deviation, the hamate rides “high” on the triquetrum, forcing it into dorsiflexion. This, coupled with the distraction effect of the scaphotrapeziotrapezoid ligaments on the scaphoid, forces the entire proximal row into dorsiflexion. The opposite is seen during wrist radial deviation, in which the triquetrohamate, triquetrocapitate, and dorsal intercarpal ligaments “pull” the triquetrum out of dorsiflexion.
Material and Constraint Properties
The material properties of the subregions of the LT ligament have been studied in the laboratory (3). It is most interesting to note that the morphology and material and
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constraint properties are the mirror image of the scapholunate ligament. The dorsal region of the LT ligament failed at approximately 120 N, and the thicker palmar region failed at 300 N. The fibrocartilaginous proximal region fails at approximately 65 N. The palmar region was found to constrain primarily translation, whereas the dorsal region provides the majority of rotational constraint.
MECHANISM OF INJURY
Degeneration
Injuries of the LT ligament should first be divided into stable and unstable conditions. Those conditions that are stable are largely degenerative and involve disruption of only the proximal region of the LT ligament. This region is composed of fibrocartilage. As such, it is prone to age-related degeneration, as discussed by Micik (14). It is also vulnerable to changes that are associated with degeneration of the proximal articular surfaces of the triquetrum and lunate, such as ulnar abutment syndrome (15,16,17 and 18). In either case, the LT joint is not dissociated and does not undergo the progressive derotational changes that are associated with true LT dissociation. This does not mean, however, that the degenerative changes are not associated with pain and perhaps even subtle mechanical alterations in the LT mechanism. Loss of the meniscal-like support of the fibrocartilaginous proximal region may create long-term problems, just as they do in the knee. The solution for these conditions, however, is not a stabilization procedure, as it would be for a true LT dissociation.
Traumatic
There is a general consensus that a true LT dissociation is part of a spectrum of progressive ligament disruption that is associated with a lunate or perilunate dislocation (19,20). There are two directions in which the perilunate dislocation occurs: classic and reverse. In both scenarios, LT dissociation occurs as a stage of the overall dislocation. Although laboratory studies have helped surgeons understand the direction of forces that are likely to be responsible for the injury, each case should be viewed differently, as the spectrum of actual injury may be different.
Progressive Perilunate Instability
Mayfield et al. (20) significantly added to surgeons’ understanding of the progressive and integrated nature of the classic perilunate dissociation. In the laboratory, they determined that axial loading of a cadaver specimen that was positioned in extreme ulnar deviation, wrist dorsiflexion, and intercarpal supination had the highest correlation with progressive perilunate dislocations. They also determined that there are two general patterns of damage: greater arc and lesser arc.
Greater arc perilunate dislocations involve fracture-dislocation patterns. Included would be fractures that involve the radial styloid process, scaphoid, capitate, hamate, triquetrum, and ulnar styloid process. There are variable degrees of associated soft tissue damage as well, depending on the fracture pattern. Lesser arc injuries are confined to those that involve only ligaments, with no associated fractures.
The classic pattern of progressive perilunate instability begins with palmar-to-dorsal disruption of the scapholunate interosseous ligament. The disruption continues distally and ulnarly, around the palmar horn of the lunate, separating the interligamentous sulcus between the radio-scaphocapitate and long radiolunate ligaments. The pathologic extension of this sulcus around the distal margin of the palmar lunate is called the space of Poirier. Owing to the strength of the long and short radiolunate ligaments, the lunate typically remains associated with the distal radius, but the radial one-half of the carpus begins to dislocate dorsally, away from the radius and the lunate. The soft tissue disruption propagates proximally, disrupting the LTIL, and often extending proximally into the palmar radio-ulnar ligament of the triangular fibrocartilage complex. This dissociates the triquetrum from the lunate, but a true dorsal dislocation of the triquetrum from the lunate does not occur until the DRC ligament is dissociated from the lunate. At this point, the entire carpus, except for the lunate, is dorsally dislocated from the forearm, creating the classic perilunate dislocation. Often, the carpus relocates relative to the radius but pushes the lunate into flexion through the rent in the interligamentous sulcus and the space of Poirier, thus creating a lunate dislocation. Thus, LT dissociation is an integral part of a progressive perilunate dislocation, but it is difficult to imagine how this happens in the classic radial-to-ulnar progression pattern. More than likely, a finding of an isolated LT instability represents a residual problem from a previous perilunar injury in which the scapholunate aspect has healed sufficiently or is the product of a reverse perilunate injury pattern.
Reverse Perilunate Injury
An interesting hypothesis has been recently advanced (21,22) in which the pattern of a classic perilunate injury is reversed, thus initiating the pattern of ligament disruption through the LT joint (Fig. 2). This has been confirmed in a cadaver series, with the position of injury flexion and radial deviation (22).
Other Etiologies
There are several nontraumatic etiologies that may contribute in one form or another to the creation of an LT dissociation–like condition. Included would be inflammatory and crystalline arthropathies, developmental extreme ulnar-plus variance of the ulna, and generalized joint laxity.
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FIGURE 2. Schematic of the mechanism of injury that leads to a reverse perilunate dissociation with axial loading on the ulnar aspect of the wrist in radial deviation and pronation.
Pathomechanics of Intercalated Segment Instability
In their classic treatise on carpal instability, Linscheid et al. (19) applied the concept of intercalated segment instability, as defined by Landsmeer, to intercarpal dissociation of the carpus. Two well-recognized patterns of intercalated segment instability were introduced: dorsiflexed intercalated segment instability and volarflexion intercalated segment instability. There are several key points about these terms that must be understood before the terms can be applied with meaning. First, the term intercalated refers to a bone with no active motor controlling it. It is a bone whose position is determined solely by the forces that are transmitted across its articular surfaces, the shape of those articular surfaces, and its connection to contiguous bones via ligaments. Second, the intercalated segment in carpal instability refers to the lunate. Third, the orientation of the lunate can be used to designate intercalated segment instability only when the wrist is in neutral extension and deviation relative to the forearm, and a true lateral radiograph, which is centered over the wrist, is obtained. Finally, the angle of the lunate relative to the capitate or the radius is determined by defining the bisection axis of the capitate or the radius and by defining a perpendicular to a cord between the tips of the palmar and dorsal horns of the lunate. The intersection angle between the lunate perpendicular and the bisection axis of the capitate or the radius defines the lunocapitate and radiolunate angles, respectively. Under these constraints, dorsiflexion of the lunate of greater than 10 degrees is termed dorsiflexed intercalated segment instability, and palmar flexion of the lunate of greater than 10 degrees is termed VISI. VISI is typically associated with LT dissociation, although generalized joint laxity, distal radius malunion, and positive variance of the ulnar can contribute to a VISI posture of the lunate, even in the face of an intact LT ligament. However, two laboratory studies have demonstrated that, in addition to complete LT ligament disruption, particularly the palmar region, the DRC ligament must be disrupted from the lunate to generate the VISI posture of the lunate (23,24).
PATIENT PRESENTATION AND PHYSICAL EXAMINATION
Patients with LT dissociation typically present with a complaint of ulnar-sided wrist pain, which is usually worsened with activity (16,18). The spectrum of presentation, however, is quite variable. Patients may complain of intermittent or constant pain, may believe that they have sprained their wrist, may experience a loss of motion and a feeling of weakness, and may even experience ulnar nerve dysesthesias. In true LT dissociation, many patients state that they sense a “clunk” in their wrist with radial-ulnar deviation (21). A history of some specific injury is usually present, in distinction to a gradual onset of symptoms that are associated with a degenerative process. If the injury reported seems trivial, one should be suspicious of an acute-on-chronic scenario, possibly suggesting a more degenerative process than acute disruption. One should be most concerned about those injuries with body-weight loading, such as a fall on the outstretched extremity, especially loading on the ulnar side of the wrist (25).
Much can be gained by simply observing the posture of the extremity in the examination room, as well as how the patient is using his or her affected extremity. A silver fork deformity is suggestive of complete collapse. Standard measures should be obtained for both upper extremities, including ranges of motion of all upper extremity joints, starting proximally with the shoulder and progressing distally to the interphalangeal joints. Grip strengths and pinch strengths should be recorded, as well as a careful neurologic and circulatory examination of both upper extremities. Any symptoms, such as crepitus, clicks, and clinks, with range of motion should be noted, looking specifically for asymmetry and association with symptom provocation.
Site-specific tenderness should be elicited. Each carpal bone can be located by palpation, and specific features on each carpal bone can typically be found by palpation. With LT dissociation, one should search for tenderness in the LT interval. The dorsal tubercle of the triquetrum is easily identified as the prominence that is just distal to the ulnar head. The LT interval is found immediately deep to the tendon of the extensor digiti minimi. Tenderness in either of these areas is suspicious for an LT ligament injury. At the same time, specific palpation examinations of the surrounding structures, including the ulnar styloid process, the hook of the hamate, the distal radioulnar joint, the
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scapholunate joint, the pisotriquetral joint, the extrinsic extensor tendons, and the ulnar neurovascular bundle, which can mimic LT dissociation pain, should be carried out (18,26).
FIGURE 3. Drawing of the ballottement test.
Several provocative maneuvers have been developed to increase the specificity of diagnosis for LT dissociation. Ballottement of the triquetrum, which is described by Reagan et al. (21), is performed by grasping the pisotriquetral unit between the thumb and index finger of one hand and the lunate between the thumb and index of the other (Fig. 3). If positive, increased anteroposterior laxity is noted along with pain. The shear test, which is described by Kleinman (27), is performed with the forearm in neutral rotation and the elbow on the examination table (Fig. 4). The examiner’s contralateral thumb is placed over the dorsum of the lunate, deep to the extensor digitorum communis tendons and just distal to the distal edge of the dorsal radius. With the lunate supported, the examiner’s ipsilateral thumb pushes dorsally on the pisiform, creating a shear force at the LT joint. Compression of the LT joint can be accomplished by pressing laterally on the medial tubercle of the triquetrum (Fig. 5). Pain that is elicited with this maneuver may be of LT origin but may also arise from the triquetrohamate joint (12). These maneuvers are considered positive when pain that is similar to the patient’s presenting complaints, crepitus, and abnormal mobility of the LT joint is demonstrable. It is critical, however, to be certain that such findings are noted only in the symptomatic wrist. Bilateralism of findings reduces one’s confidence that the problem has been identified.
Differential injections with a short-acting local anesthetic, such as lidocaine, can be extremely useful in sorting out the source of a patient’s pain. Resolution of pain with increased grip strength after injection in patients with LT injuries has been a reliable predictor of intraarticular causes of pain, hence increasing the likelihood of identifying such sources arthroscopically. A poor response to injection implies an extraarticular cause of the patient’s symptoms
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and, hence, a smaller likelihood of arthroscopic identification of meaningful pathology.
FIGURE 4. Drawing of Kleinman’s shear test.
FIGURE 5. Drawing of lateral compression test.
IMAGING
As in all conditions of the wrist, imaging studies should be considered largely as confirmatory tools rather than diagnostic tools. One should already be suspicious of LT dissociation as the diagnosis before ordering any imaging studies. In this manner, the cost of the evaluation and the redundancy of testing are minimized. Virtually the entire spectrum of imaging, however, has been used for the diagnosis of LT dissociation, including routine wrist radiographs, motion studies, tomography, arthrography, videofluoroscopy, scintigraphy, and magnetic resonance imaging.
Plain radiographs of stable LT tears typically demonstrate normal intercarpal relationships (28). However, they may demonstrate associated findings of ulnar positive variance and cystic degeneration of the ulnar one-half of the proximal surface of the lunate. It is important that such films be obtained in the standard position fashion, as is described in Chapter 6. True LT dissociation may result in a disruption of Gilula’s arc I and II, with proximal translation of the triquetrum or LT overlap, or both (Fig. 6) (21,28); however, such disruptions may be seen only in motion series views. Again, comparisons with the contralateral extremity should be made. Unlike scapholunate injuries, no LT gap occurs. A static VISI deformity not only implies injury to the LT ligament but also additional dorsal or palmar ligament attenuation (Fig. 7) (18,23,24). Increased palmar flexion of the scaphoid and lunate in radial deviation, without change of the triquetrum, is a manifestation of the loss of proximal row integrity that is present in normal wrists. If a VISI deformity is present with LT dissociation, the radiolunate and capitolunate angles are altered. The scapholunate angle may be diminished from its normal 47 to 40 degrees or less but is often normal. As noted previously, the lunate and capitate, which are normally colinear, collapse in a zigzag fashion, thus resulting in an angle that is greater than 10 degrees.
FIGURE 6. Posteroanterior radiograph of a wrist with lunotriquetral dissociation. The triquetrum is translated proximal to the lunate, disrupting Gilula’s arcs I and II.
FIGURE 7. Lateral radiograph of a wrist with lunotriquetral dissociation. The lunate (and scaphoid) are abnormally palmar flexed relative to the orientation of the hand to the forearm. This indicates a volarflexed intercalated segment instability posture.
Arthrography has historically been believed to be valuable, demonstrating direct communication between the radiocarpal and midcarpal joints through the LT interval (Fig. 8) (29,30,31,32 and 33).
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However, because of the age-related degenerative tendencies of the fibrocartilaginous proximal region of the LT ligament, such communication of radiocarpal and midcarpal joints and asymptotic LT tears on arthrography of normal wrists has been reported. Therefore, the results of arthrography must be correlated with clinical examination findings. A videotaped arthrogram with motion sequences in flexion-extension and radial-ulnar deviation can further confirm the presence of an LT injury by demonstrating abnormal pooling of the contrast material column and abnormal proximal row kinematics, as previously described. Videofluoroscopy is useful in demonstrating the site of a “clunk” that occurs with deviation. If the entire proximal row suddenly shifts as a unit into dorsiflexion or palmar flexion, it is probably not associated with LT dissociation.
FIGURE 8. Posteroanterior arthrogram of a wrist with a defect in the lunotriquetral interosseous ligament, which allows contrast material to flow between the radiocarpal and midcarpal joints.
Other imaging studies may be useful at times. Technetium 99m bone scans can help identify the site of acute injury but are less specific than arthrography (34). They may prove helpful in cases in which standard films and motion studies are negative. Magnetic resonance imaging technology is not yet reliable for LT ligament imaging and is limited to the same constraints as arthrography. However, scintigraphy and magnetic resonance imaging are useful for identifying problem sources other than the LT ligament in those patients in whom LT dissociation is not the likely source of the patient’s problem (35,36).
Over the past decade, arthroscopy has become the most definitive diagnostic tool for confirming the presence and defining the stage of LT dissociation (37,38). Geissler et al. (39) have defined a staging system based on midcarpal arthroscopy. The reason that midcarpal arthroscopy is used is that the radiocarpal perspectives of the lunate and triquetrum present as convex surfaces, thus demonstrating difficulty in detecting rotational displacement. Because the midcarpal surfaces of the LT joint are concave and present as a free edge of the joint space, rotational displacements are relatively easy to detect. This is not to say that the radiocarpal perspective is useless. One can still identify gross tears in the proximal region of the interosseous ligaments, as well as detect associated degenerative changes in the articular surfaces.
The arthroscopic staging is applicable to scapholunate and LT injuries. The simple presence of an arthroscope may be sufficient to create displacement of the lunate or the triquetrum, so it is important to observe the LT joint from radial midcarpal and ulnar midcarpal perspectives (Table 1).
TREATMENT
Treatment options for conditions that affect the LT ligament cover almost the entire spectrum, from conservative care to arthrodesis. The final choice of treatments is based on the pathology that is present, patient factors, and the experience of the surgeon. Above all, the treating surgeon wants to be certain that matters are not worse after treatment, so more conservative steps are probably indicated more often than not, particularly early on in the care of a patient.
TABLE 1. ARTHROSCOPIC CLASSIFICATION FOR INTERCARPAL DISSOCIATION OF SCAPHOLUNATE AND LUNOTRIQUETRAL JOINTS BY GRADE, BASED ON RADIOCARPAL, MIDCARPAL, AND INTERCARPAL CRITERIA
Dissociation grade Radiocarpal appearance Midcarpal step-off Intercarpal diastasis
I Torn, hemorrhagic LT ligament None No probe admittance.
II Torn, hemorrhagic LT ligament Mild Standard probe is inserted between bones; no twist.
III Torn, hemorrhagic LT ligament Moderate Standard probe can twist 360 degrees within the joint cleft.
IV Torn, hemorrhagic LT ligament Unstable Arthroscope can easily pass between radiocarpal and midcarpal joints.
LT, lunotriquetral.
Conservative Management
Conservative management is indicated primarily for stable, degenerative conditions of the LT ligament (18,21,25). This includes degenerative processes that are related to age of the fibrocartilage and even secondary degeneration that is related to ulnar abutment syndrome. If conservative measures fail, surgical intervention can be considered without loss of outcome potential. The other condition in which conservative management may be considered is the patient who presents with an end-stage VISI deformity that is secondary to a long-standing LT dissociation. In this circumstance, a salvage procedure is the likely operative option, and the patient should contemplate the implications of a salvage procedure and should be certain that conservative measures will fail to improve his or her condition before proceeding. Commonly used conservative measures include the use of a supportive splint or brace, particularly when sleeping, antiinflammatory medications (systemic or injected), and activity modifications.
If an acute LT injury is suspected, but no radiographic changes are present, thus indicating static deformities, conservative treatment with a well-molded cast should be considered. There is no evidence to suggest that conservative management is detrimental in these patients (21). The author would recommend initial long arm immobilization with a supportive pad placed under the pisiform for 4 weeks, followed by a short arm cast, again with the pisiform
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support for an additional 4 weeks. The author uses a long arm support initially because of concerns about the effect of torsion that is applied across the ulnar carpus during forearm rotation.
Surgical Management
The goals of surgical management are essentially twofold: (a) to improve current symptoms and (b) to stabilize the unstable joint to prevent recurrence of symptoms. The application of individual surgical techniques is dependent on the skill and experience of the surgeon and the diagnosis.
Arthroscopy
Arthroscopic débridement is an adjunct to diagnostic arthroscopy. Typically, the viewing portal for the arthroscope is the 3-4 portal, and a 3-mm aggressive shave is introduced into the 4-5 portal. Synovial hyperplasia can be resected around the triangular fibrocartilage complex, and any degenerative regions in the LT ligament can be resected with the shaver. Care must be exercised, however, to avoid débriding the ulnocarpal ligaments and the dorsal region of the LT ligament. Resection of these structures may result in iatrogenic instability.
If there is no static VISI deformity, and if a grade I to III LT instability is found on midcarpal arthroscopy, as noted previously, arthroscopically guided percutaneous pinning of the LT joint may be beneficial, much in the same way that Whipple has demonstrated success with similar procedures that were applied to the scapholunate joint. The author prefers to have the arthroscope in the radial midcarpal portal for this procedure, because the alignment of the LT joint is much easier to evaluate from this perspective. A longitudinal incision is made in the skin over the medial tubercle of the triquetrum. Care is taken to be certain that branches of the dorsal sensory ulnar nerve are not at risk. A single 0.045- or 0.062-in. Kirschner wire (K-wire) is advanced just into the triquetrum. It is subsequently used as a joystick to compress the LT joint while maintaining anatomic rotational alignment. Under fluoroscopic and arthroscopic guidance, three to four 0.045-in. K-wires are advanced across the LT joint. Care is taken to insure that the skin margins are without tension, and a sterile dressing is applied. The same cast immobilization protocol is applied as is used for conservative care, which was noted previously. The author prefers to keep the pins in place for 8 to 12 weeks, if possible. Postoperatively, splint support is gradually tapered at the patient’s tolerance, proportionate to increases in the patient’s activity level.
Direct Repair
An open repair is attempted only when there are sufficiently strong ligament remnants present, when the ligament remnants have a reasonable healing potential, and when the LT relationship is easily reduced (21,40). These criteria limit the application of open repair techniques to acute injuries, most typically those that are associated with perilunate dislocations. Significant controversy remains about the most ideal approach, which ranges from percutaneous pin fixation to dorsal-only repair, volar-only repair, and combined dorsal-volar repairs, for such injuries. There are insufficient data to draw an objective decision regarding isolated LT dissociation, so the author describes dorsal and volar approaches and lets the surgeon decide for himself or herself which avenue to follow. The perioperative goals of an open repair are to (a) coapt the injured ends of the ligament to a healable structure and (b) stabilize the LT joint in a manner that allows the soft tissue repair to heal sufficiently.
Dorsal Approach
The dorsal approach that is described in this section is applicable to all open procedures on the carpus and is amenable to individual modifications. These procedures are carried out under regional or general anesthesia and typically under pneumatic tourniquet control for hemostasis. The author typically administers parenteral antibiotics before exsanguination of the extremity and inflation of the tourniquet.
A dorsal skin incision is made and can be curvilinear or straight, transverse or longitudinal, or in a T shape, according the surgeon’s determination (Fig. 9A). Care should be taken to avoid injury to the dorsal sensory ulnar nerve branches or the superficial radial nerve branches, which are found just deep to the basilic and cephalic veins, respectively, as they cross the region of the wrist. The tendon of the extensor pollicis longus is exposed by opening the third extensor compartment. An ulnar-based retinacular flap is elevated at least through the fourth compartment and is possibly extended to include the fifth extensor compartment. Fascial extensions of the retinacular elevations are created proximally and distally to allow retraction of the enclosed extensor compartments. A ligament-splitting capsulotomy is carried out in the standard fashion by splitting the DRC and dorsal intercarpal ligaments (Fig. 9B) (41). Care is taken to insure that the proximal one-half of the DRC ligament is preserved to the attachment to the lunate and triquetrum.
The dorsal aspect of the LT joint is visible at this point (Fig. 9C). A single 0.062-in. K-wire is advanced into each dorsal cortex of the lunate and triquetrum to be used as joysticks. Two or three 0.045-in. K-wires are passed across the LT joint, once it is anatomically reduced, as described previously, to stabilize the LT joint. Typically, the dorsal LT ligament is avulsed off of the triquetrum, although this can vary. Several drill channels through the dorsal tubercle of the triquetrum (Fig. 9D) and two lengths of 2-0 monofilament resorbable suture are passed in a horizontal mattress pattern through the ligament stump on the lunate and through the triquetral drill channels (Fig. 9E,F). An alternative would be to place a bone anchor in the dorsal subcortical bone of the
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triquetrum (or the lunate, if the ligament remnant is primarily attached to the triquetrum). The DRC ligament is repaired in a side-to-side fashion over the LT joint, as the capsulotomy flap is replaced into its original position (Fig. 9G). Postoperative support, K-wire removal, and rehabilitation are carried out.
FIGURE 9. Series of drawings that demonstrate the direct repair technique. A: A skin incision is made to expose the extensor retinaculum. B: The dorsal wrist joint capsule is exposed after elevation of the extensor retinaculum and retraction of the digital extensor tendons. The dorsal radiocarpal and dorsal intercarpal ligaments are split longitudinally to begin the capsulotomy. C: The capsulotomy is completed by an incision of the radiocarpal capsule along the dorsal rim of the distal radius, exposing the underlying proximal row. The lunotriquetral dissociation is confirmed at this point. D: Three to four channels are drilled obliquely through the dorsal tubercle of the triquetrum with Kirschner wires. E: Multiple suture strands are drawn through the triquetral drill channels and through the stump of the lunotriquetral ligament in a mattress suture fashion. F: With the lunotriquetral joint stabilized with Kirschner wires, the sutures in the lunotriquetral ligament stump are drawn tight and secured to the triquetrum. G: The capsulotomy is closed with side-to-side sutures. DRT, dorsal radiotriquetral (radiocarpal) ligament; DST, dorsal triquetroscaphoid (intercarpal) ligament. (Reprinted with permission of Mayo Foundation.)
Volar Approach
In the volar approach, a longitudinal incision is creased, extending distally to the wrist flexion crease, just radial to the flexor carpi ulnaris tendon. Typically, an incision of 4 to 5 cm is all that is required. The deep antebrachial fascia is carefully and bluntly dissected to identify the ulnar nerve and artery, which are then retracted ulnarly with the flexor carpi ulnaris tendon. The digital flexor tendons are retracted radially. This exposes the volar joint capsule of the distal radioulnar joint and the palmar surface of the LT joint. The level of the LT joint is easily found by locating the pisiform, which is directly anterior to the triquetrum (Fig. 10). There almost universally is sufficient tissue to carry out a direct repair through the palmar region of the LT ligament, particularly because it is reinforced with fibers from the ulnocapitate ligament.
Ligament Reconstruction
Ligament reconstruction is indicated more often than direct repair, owing to the typical chronicity of the injury and status of the ligament remnants. There are several options for this, including extrinsic tenodesis, ligamentoplasty, and autogenous bone-ligament transfer (21,40).
Extrinsic Tenodesis
The surgical approach for extrinsic tenodesis is the same as that described previously for direct repair. However, the LT joint is not stabilized by K-wires until the last step. Drill channels are established through the dorsal cortices of the triquetrum and lunate by using hand awls or a cannulated drill set into the lunate and triquetrum in such a manner that the channels converge toward each other near the palmar margin of the LT joint (Fig. 11A,B). A distally based strip of extensor carpi ulnaris is elevated, beginning several centimeters proximal to the extensor retinaculum of the sixth compartment (Fig. 11C). By translating the tendon proximally and distally, it is not necessary to disturb the sixth compartment or the important extensor carpi ulnaris tendon subsheath when elevating the tendon strip. Using a pull-through wire, the tendon is then passed palmarly through the triquetral channel, across the LT joint, dorsally through the lunate channel, and ulnarly across the dorsal margin of the LT joint (Fig. 11D). At this point, the LT joint is stabilized with K-wires, and the tendon strip is pulled taut and sutured back to itself in a Pulvertaft weave fashion with braided, nonresorbable suture (Fig. 11E). Capsular repairs are carried out as described previously. Postoperative support, K-wire removal, and rehabilitation are carried out as described previously.
FIGURE 10. Photograph of a volar approach to the lunotriquetral joint for repair of the lunotriquetral ligament in a perilunate dislocation. C, capitate; H, hamate; L, lunate; LT, lunotriquetral ligament; sP, space of Poirier; T, triquetrum; UC, ulnocapitate ligament.
Ligamentoplasty
The ligamentoplasty technique establishes only a dorsal connection between the lunate and triquetrum, as opposed to the ligament reconstruction that was described previously. If the palmar region of the joint seems stable at the time of arthroscopy, this is a reasonable option. The ligamentoplasty takes advantage of the fact that there is normally an attachment of the DRC ligament to the lunate and the triquetrum. Typically, the attachment of the DRC ligament to the triquetrum is preserved at the dorsal tubercle. Therefore, advancing the DRC ligament more tightly into the dorsal cortex of the lunate may simulate the function of the dorsal region of the LT ligament. This can be accomplished by minimally undermining the DRC at the lunate, corrupting the dorsal cortex of the lunate, and placing a bone anchor. The suture is then drawn through the DRC after the LT joint is stabilized with K-wires, as described previously. Postoperative support, K-wire removal, and rehabilitation are carried out as described previously.
Osteoligamentous Autograft
The indications for an osteoligamentous autograft are no different than those for ligament reconstruction, although the use of such a technique is not as compelling in LT dissociation as it is in scapholunate dissociation, largely owing to the number of workable alternatives. The author prefers to use a local donor site, such as the capitohamate ligament complex, for this reason, although other donor ligament sources have been identified (42,43 and 44). Through the ligament-splitting capsulotomy, the dorsal capitohamate joint is easily exposed with the dorsal capitohamate ligament (Fig. 12A). After securing the LT joint with K-wires in a reduced state, as described previously, a transverse channel
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is developed in the dorsal cortices of the lunate and triquetrum, with cubes excavated in each bone with side dimensions of approximately 3 to 4 mm. The excavations are carried out in an aligned fashion to create a continuous channel across both bones. Using sharp osteotomes, a bone–ligament–bone autograft is harvested centered over the dorsal capitohamate ligament (Fig. 12B). Care is taken to avoid compromise of the carpometacarpal joints. The
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deep and palmar capitohamate ligaments maintain sufficient support for the capitohamate joint, even in the face of loss of the dorsal ligament complex. The osteoligamentous autograft is then press fitted into the dorsal LT channel and secured with singe 1.3-mm screws (Fig. 12C). Postoperative support, K-wire removal, and rehabilitation are carried out.
FIGURE 11. Series of drawings that demonstrate ligament reconstruction with extrinsic tendon technique. A: Drill channels are initiated in the lunate and triquetrum with Kirschner wires, which obliquely converge toward the volar aspect of the joint. B: The drill channels are expanded by using manual awls or drill bits. C: A distally based strip of extensor carpi ulnaris (ECU) is created proximal to the extensor retinaculum and is continued distally, without disturbing the ECU tendon subsheath. D: The strip of ECU tendon is passed through the drill channels in the triquetrum and lunate via a pull-through wire. E: The ECU tendon is sutured back to itself, and the lunotriquetral joint is stabilized with multiple transosseous Kirschner wires. (Reprinted with permission of Mayo Foundation.)
FIGURE 12. Osteoligamentous ligament reconstruction technique. A: Drawing of the dorsal wrist with the dorsal capitohamate ligament highlighted. B: A cortical channel is made across the dorsal aspect of the lunotriquetral joint, and a similarly sized bone–ligament–bone autograft is harvested, based on the dorsal capitohamate ligament. C: The graft is secured to the lunate and triquetrum with 1.3-mm screws, and the joint is held in reduction with multiple Kirschner wires. D: Postoperative posteroanterior radiograph of an osteoligamentous lunotriquetral ligament reconstruction. C, capitate; H, hamate.
Arthrodesis
Arthrodesis has been a highly used technique for treating LT dissociation, particularly chronic (irreparable) LT dissociation (21,40). A considerable factor that supports the use of arthrodesis is the functional state of individuals with a congenital LT coalition (45). Additional weight is gained by carpal kinematic studies that have shown that mutual displacement between the lunate and triquetrum is relatively small (46). There is no doubt, however, that some loss of range of motion is going to occur as the result of surgical arthrodesis, from the arthrodesis itself or from the soft tissue aspects of the procedure. There are several caveats, however, to consider before performing an LT arthrodesis. First, all efforts should be made to ensure that the patient is not a current tobacco abuser. One unpublished study has shown that active tobacco abuse is associated with delayed or nonunion rates in the carpus at least fivefold over those of nonabusers (47).
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Second, care must be taken to ensure that the arthrodesis does not result in a change in the geometry of the midcarpal articular surface. This has adverse effects on the pole of the hamate. Finally, an LT arthrodesis is not likely to correct an existing VISI deformity.
FIGURE 13. Drawing of the principles that are used in lunotriquetral arthrodesis. The normal spatial relationships between the lunate, the triquetrum, and the contiguous bones are maintained by partial decortication of the lunotriquetral joint space (A) and implantation of appropriate graft material (arrow). Fixation choices are at the surgeon’s discretion (B). (Reprinted with permission of Mayo Foundation.)
The arthrodesis is carried out through the same dorsal approach that was described previously. The LT joint is reduced and secured with a temporary K-wire, as described previously. Several arthrodesis techniques can now be used, including, but not limited to, excavation of a dorsal channel across the lunate and triquetrum, excision of a core of the LT joint cleft, and simple decortication of the mutual articulating surfaces of the lunate and triquetrum (21,40,48). The arthrodesis is completed with implantation of autograft from the distal radius or a more remote site, allograft, or a bone substitute, depending on the surgeon’s experience and patient factors (Fig. 13). The arthrodesis can then be secured with multiple K-wires, staples, headless screws, dorsal plate and screw constructs, or any other technique that is acceptable to the surgeon. If headless screws are used, care must be taken to ensure that the LT joint is not overcompressed, as this changes the geometry of the midcarpal joint surface. Postoperative support is continued until the arthrodesis is mature, radiographically and clinically.
Salvage Procedures
A salvage condition is one in which the treatment options that were discussed previously are applicable. The most common salvage situation with LT dissociation is a static VISI deformity. It is known from laboratory studies that, to develop a static VISI deformity in the face of LT dissociation, not only does the LRT ligament need to be compromised, but compromise of the DRC ligament from the lunate is also required. There may be other adaptive changes that occur in other contiguous ligament systems, but this remains theoretical at best. Regardless, simply correcting the LT dissociation does not correct the VISI posture of the lunate. This typically results in a progressive recurrence of a VISI stance, but instead of just the lunate and scaphoid volarflexing inappropriately, the entire proximal row volarflexes.
Treatment for the painful wrist may begin with consideration of a denervation procedure. Soft tissue–based procedures to correct the VISI stance of the lunate have anecdotally not been effective. Therefore, a bone-based procedure should be considered. The literature is devoid of clear guidelines to determine which procedure should be considered, so it remains a personal choice of the surgeon, based on experience and patient factors. Included in the list of options would be a radiolunate arthrodesis, midcarpal arthrodesis, proximal row carpectomy, and total wrist arthro-desis. All result in a noticeable reduction in range of motion; however, many believe that the radiolunate arthrodesis affects motion the least. With this procedure, however, one must be careful to avoid “insetting” the lunate into the radius, thus potentially creating an ulnar impaction syndrome. The author does not advocate total wrist arthrodesis for this condition except as an option for failed partial arthrodesis or carpectomy (26,49,50,51,52 and 53).
OUTCOMES
There is surprisingly little literature available to critically evaluate outcomes of treatment. First, it is important that, as discussed previously, a differentiation between a true LT dissociation and an LT tear be made. In the former situation, one must consider the inciting cause, such as ulnar abutment syndrome or inflammatory arthropathy, and must evaluate the efficacy of the treatment options for the underlying etiology (54).
Conservative treatment for true acute LT dissociation has been reported in which careful application of cast
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immobilization has been believed to result in primary ligament healing (55). Not all patients with radiographically evident LT malalignment are clinically symptomatic. Only those with impairment that is secondary to symptoms that are related to the LT instability are typically considered candidates for surgical intervention (56).
A recent report of a series of 57 patients with LT dissociation who were treated with surgical intervention was published (40). The injuries were felt to be subacute or chronic in all but one case. Eight patients had ligament reconstruction by using a distally based strip of extensor carpi ulnaris tendon, 27 had a direct repair, and 22 underwent LT arthrodesis. The reconstruction group remained less symptomatic than the other two groups, with 68% free from complications at 5 years postsurgery, compared to 13% and 1% for the direct repair and arthrodesis groups, respectively. The probability of not requiring further surgery at 5 years was 68%, 23%, and 22% for the reconstruction, repair, and arthrodesis groups, respectively. The arthrodesis group experienced the worst success rate, due, in large part, to a high nonunion rate (41%) and ulnocarpal impaction syndrome (23%). Outcome measurement using the Disabilities of the Arm, Shoulder, and Hand questionnaire, however, did not demonstrate a significant difference. Others’ experiences with arthrodesis have been more favorable, but it is clearly a treatment option that requires substantial preoperative counseling and fastidious technique (48,50).
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