Carpal instability

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Carpal instability

  1. 1. 476 THE JOURNAL OF BONE AND JOINT SURGERY Carpal Instability* BY LEONARD K. RUBY, M.D.t. BOSTON. MASSACHUSETTS An Instructional Course Lecture, The American Academy ofOnthopaedic Surgeons Although the anatomy and function of the wrist have been studied since medieval times, the current em- phasis on this subject dates from the classic 1972 study by Linscheid et al.’9, which increased interest in trau- matic instability of the wrist and its pathomechanics. That study was based on the works of several authors, including Destot5, Navarro24, Gifford et al.9, and Fisk7. The present lecture describes the recent advances in the understanding of the structure and function of the wrist and summarizes the current thinking regarding the di- agnosis and treatment of the clinically important carpal instabilities. Bones Anatomy The carpus includes four sets of joints: the distal radio-ulnar joint, the radiocarpal joint. the mid-canpal joint, and the carpometacarpal joints. In this lecture, I will limit my discussion to the radiocarpal and mid- carpal joints. The bones of the carpus can be thought of as lying in two rows. The proximal row consists of the scaphoid, the lunate, and the tniquctrum. The pisiform is a sesamoid bone in the tendon of the flexor carpi ulnanis and, as such, is not a functional part of the proximal row. The distal row is composed of the trapezium, the trape- zoid, the capitate, and the hamate. The mid-carpal joint is the confluent articulation between the proximal and distal carpal rows. The scaphoid occupies a unique posi- tion, as it spans the mid-carpal joint and forms an osse- ous link between the proximal and distal rows’7. Ligaments Each bone is relatively tightly and securely bound to its neighbors by strong interosseous ligaments. The interosseous ligaments of the distal row seldom fail din- ically. The interosseous ligaments of the proximal row include the ligament between the scaphoid and the lu- nate (the scapholunate interosseous ligament) and the *printed with permission of The American Academy of Ortho- paedic Surgeons. This article will appear in Instructional Course Lectures, Volume 45, The American Academy of Orthopaedic Sur- geons, Rosemont. Illinois, March 1996. tNew England Medical Center, 750 Washington Street. Boston, Massachusetts 02111. ligament between the tniquetrum and the lunate (the tniquetrolunate interosseous ligament). These ligaments are c-shaped: they are attached to the dorsal, palmar, and proximal edges of each of the three bones of the proximal row. They are open distally into the mid-carpal joint, so that an anthrogram of a normal mid-canpal joint shows contrast medium between the three bones. The ligaments are thickened dorsally and palmarly and have a relatively thin membranous portion centrally (Figs. 1 and 2). Recent studies have shown that the central por- tions are not nearly as strong as the dorsal and palmar portions and, therefore, may not be as important me- chanically. Mayfield et al.2’ and Logan et al.’9 measured the failure strength’ and stress-strain behavionis f these ligaments in cadavenic specimens and reported that the scapholunate interosseous ligament failed at 232.6 ± 10.9 newtons (52.3 ± 2.5 pounds) and the tniquetro- lunate interosseous ligament, at 353.7 ± 69.2 newtons (79.5 ± 15.6 pounds). Furthermore, both of these liga- ments elongated by as much as 50 to 100 per cent of their original length before failure. In addition to the interosseous ligaments, the wrist contains the dorsal and palmar capsular ligaments, which are thickenings of the wrist capsule. These liga- ments also have been well described by several authors, including Taleisnik32, Mayfield et al.si, and Berger and Landsmeeni. The dorsal capsular ligaments include the dorsal radiocanpal ligament and the dorsal intercarpal ligament (Fig. 3); the former may be especially impor- tant as an accessory stabilizer of the tniquetrolunate and radiocarpaljoints37.Taleisnik32 described the palmar cap- sular ligaments as consisting of the nadioscaphocapitate, the radiolunate, the radioscapholunate, the ulnolunate, and the ulnotriquetral ligaments. In addition, he de- scnibed the radioscaphocapitate and tniquetrocapitate ligaments as crossing the mid-carpal joint and, together, forming the so-called V. deltoid, or arcuate ligaments. The palmar ligaments recently were described again by Bergen and Landsmeen’, who suggested that the nadioscaphocapitate ligament inserts strongly into the scaphoid and weakly into the capitate. They renamed the radiolunate ligament, calling it the long nadiolu- nate ligament in order to distinguish it from the short nadiolunate ligament, which originates from the palman
  2. 2. Fio. 1 CARI’AL INSTABILITY 477 VOL. 77-A. NO. 3. MAR(’ll 1995 Cross-section of the proximal carpal row of a cadaveric wrist. C = capitate. R = radius. P = pisiform. S = scaphoid. L = lunate. T = triquetrum. SLI = scapholunate interosseous ligament. LTI = triquetrolunate interosseous ligament. LRL = long radiolunate ligament. and is = interligamentous sulcus. (Reprinted. with permission. from: Berger. R. A.. and Landsmeer. J. M. E.: The palmar radiocarpal ligaments: a study ofadultand fetal human wristjoints.J. Hand Surg.. 1SA:851. 1990.) edge of the distal part of the radius at its lunate facet and inserts into the palmar pole of the lunate (Fig. 4). The short radiolunate ligament had not been described previously. and it should not be confused with the radioscapholunate ligament described by Talcisnik’-3. The space of Poirier, a mechanically weak area of the palmar wrist capsule between the proximal and distal carpal rows. is continuous with the ligamentous sul- cus between the radioscaphocapitate ligament and the long radiolunate ligament. Stress-strain testing of pal- mar radiocarpal ligaments in cadavera showed that the radioscaphocapitate ligament failed at 151 ± 30 new- tons (33.9 ± 6.7 pounds) and that the long radiolunate ligament failed at 107.2 ± 14.8 newtons (24.1 ± 3.3 pounds); the ligaments elongated approximately 30 per cent before failure”. Therefore. as indicated previously, the interosseous ligaments of the proximal row are stronger and more elastic than any of the capsular liga- mcnts that have been tested. Tetidons The musculotendinous units that move the hand and wrist originate at the elbow and insert on the metacar- pals. No muscles attach to the proximal carpal row. The primary tiexors are the flexor carpi radialis and the flexor carpi ulnanis. The primary cxtensons are the extensor carpi radialis longus and the extensor carpi radialis brevis. The primary radial deviator is the abduc- tor pollicis longus. and the primary ulnar deviator is the extensor carpi ulnanis. Because all of these tendons in- sent on the metacarpals and because the carpomctacan- pal joints and the articulations of the distal row are relatively immobile. as is the distal row, the entire prox- imal row functions as an intercalated segment. In addi- tion, the motors of the wrist arc located peripherally. as far from the center of motion of the wrist (that is, the Fi;. 2 Drawing showing the dorsal view of the carpal interosseous liga- ments. SL = scapholunate ligament. LT = triquetrolunate ligament. -F-F = trapeziotrapezoid ligament. CT = capitotrapezoid ligament. and CH = capitohamate ligament. ( Reprinted. with permission. from: An. K-N.: Berger. R. A.: and Cooney. W. P.. Ill: Biomechanics of the Wrist Joint. p. 13. New York. Springer. 1991.)
  3. 3. 47; I.. K. RUBY I’HE Jt)URNAL OF BONE NI) JOINT SURGERY Ft(. 3 I)rawitig (if the dorsal capsular liganients. 1) R(’ = dorsal radiocar- PZLl ligiiiient. E)l(’ = dorsal intercarpal liganient. C = capitate. S = scaphoid. 1 = triquetrum. R = radius. and 1.1 = ulna. (Reprinted. with pernlission. from: iii, K-N.: Berger, R. A.: and Cooney. W. P., III: Biomeehanies of the Wrist Joint, p. 10. New York. Springer. 1991.) head of the capitate) as possible. which maximizes their effect on wrist niotion. Conversely. the digital mo- tors are located more centrally (that is, closer to the head of the capitate). which diminishes their effect on wrist motion. Kinematics Over the last seventy years. two theories - the row theory and the column theory - have been used to explain the kinematics of the wrist. According to the row theory. as described earlier. the hones of the wrist can he thought of as lying in two rows. the proximal row and the distal row. According to the column theory. as originally stated by Navarro4, the wrist is composed of three columns: the radial column (including the scaph- oid. the trapezium. and the trapezoid), the central col- umn (including the lunate and the capitate). and the ulnar column (including the triquetrum and the ha- mate). Recent studies have shown that the row theory more clearly accounts for the function of the wrist. In a normal wrist, the total arc of motion averages l5() degrees: 70 degrees of extension and 80 degrees of flexion. Approximately one-half of this total arc of mo- tion occurs at the mid-carpal joint and the other half occurs at the radiocarpal joint. From neutral to full cx- tension. approximately 66 per cent of the motion occurs at the radiocarpal joint and 33 per cent occurs at the mid-carpal joint. From neutral to full tiexion. 60 per cent 01 the motion occurs at the mid-carpal joint and 40 per cent occurs at the radiocarpal joint. The total amount of nadio-ulnan deviation is 50 degrees. of which 20 de- grees is radial deviation and 30 degrees is ulnar devia- tion; 60 per cent of this motion occurs at the mid-carpal joint. and 40 per cent occurs at the radiocarpal joint29. Not only do the mid-carpal and radiocarpal joints contribute different amounts of motion to the total arc, but they also allow movement in different directions when the wrist is moving between radial and ulnar de- viation. As the wrist moves from radial to ulnar devia- tion, the entire proximal row rotates from a position of flexion to one of extension: as the wrist moves from ulnar to radial deviation, the entire proximal row rotates from extension back into flexion (Figs. 5-A and 5-B). Although the mechanism by which this occurs is not completely understood, most authors have agreed that it is a combination of the geometry of the carpal hones, their ligamentous restraints. and the wrist motors acting through the distal carpal row that causes this conjoined synchronous motion of the proximal carpal row. Lin- scheid and Dobyns’7 suggested that, in radial deviation, pressure on the distal pole of the scaphoid by the trape- zium and trapezoid causes the scaphoid to flex. This flexion force is transmitted through the scapholunate interosseous ligament to the lunate and through the tniquetrolunate interosseous ligament to the tniquetrum, thereby causing the entire proximal row to flex. The Fu;. 4 Drawing of the palmar capsular ligaiiients. RSC = radio- scaphocapitate ligament. LRL = long radiolunate ligament. SRL = short radiolunate ligament. UL = ulnolunate ligament. UT = ulno- triquetral ligament. C = capitate. L = lunate, and S = scaphoid. (Reprinted. with permission. from: An. K-N.: Berger. R. A.: and Cooney. W. P.. III: Biomechanics of the Wrist Joint, p. 6. New York. Springer. 1991.)
  4. 4. Fit;. 5-A FRi. 5-B CARI’AL INSTABILITY 479 ‘OI.. 77-A. NO. 3. NIARCII 1995 Figs. 5-A and 5-B: Lateral radiographs of the wrist of the author. C = capitate. L = lunate. and R = radius. Fig. 5-A: Radiograph made with the wrist in radial deviation. Note the flexion of the proximal row (the lunate and scaphoid). Fig. 5-B: Radiograph made with the wrist in ulnar deviation. Note the extension ofthe proximal row (the lunate and scaphoid) and the dorsal translation of the distal row (the capitate) (black arrow). The white arrows signify the direction of rotation-extension of the lunate. reverse occurs in ulnar deviation, with the scaphoid be- ing extended through tension on the scaphotrapezial ligament. Alternatively. Weher4 proposed that the heli- coidal shape of the triquetrohamate articulation causes the distal OW to translate dorsally during ulnar devia- tion. therehy putting pressure on the dorsal aspect of the proximal OW and causing it to extend. In radial devia- tion. the distal row translates palmarly, thereby putting pressure on the palmar aspect of the proximal row and causing it to flex. Whatever the exact mechanism. there normally is a predictable amount of smooth, synchronous motion be- tween and within the two carpal rows. There is less than 9 degrees of motion between the capitate. the trapezoid. and the hamate in all arcs of motion of the wrist. There is 10 ± 3 degrees of motion between the scaphoid and the lunate and 14 ± 6 degrees of motion between the tniquetrum and the lunate as the wrist moves from full radial deviation to full ulnar deviation. There is 25 ± 15 degrees of motion between the scaphoid and the lunate and l ± 2 degrees of motion between the triquetrum and the lunate as the wrist moves from full flexion to full extension. These data were derived from cadaveric studies, and it is possible that the actual values in vivo are greater (Figs. 6-A and 6-B). Partly on the basis of these cadavenic studies, we agree with Destot that the proximal carpal row functions as an intercalated seg- mcnt with variable geometry between the distal row and the radius-triangular fibrocartilage complex’. Force Transmission Several recent studies have dealt with the subject of quantitative assessment of force transmission through the carpus’4. For technical reasons, force transmis- sion has been and continues to be a difficult area to study. Nevertheless, with use of load-cells, pressure- sensitive film. and cadaveric specimens. data have been generated that describe the magnitude and location of forces at the radiocarpal joint in normal cadavera and in simulated abnormal conditions. Palmer and Werner29 showed that. in an intact cadaveric wrist in the neutral position, 82 per cent of the total load is carried by the radius and 18 per cent. by the ulna. If the ulnar head is resected or the triangular fibrocartilage complex is re- moved, the axial load that is borne by the ulna is re- duced to 0 or 5 per cent, respectively. These findings were confirmed by Trumble et aI.#{176}.who found that. in intact specimens, 83 per cent of the load was borne by the radius and 17 per cent, by the ulna. Viegas et al.9’. who studied the contact areas of the radius-triangular fibrocantilage complex in axial-loaded cadaveric wrists, found that with a light load of twenty-three pounds (ten kilograms). only 20 per cent of the available antic- ular surface of the radius was in contact with the bones of the proximal now. With a heavier load of forty-six pounds (twenty-one kilograms) or more. this area in- creased to a maximum of 40 per cent and did not increase further even if the load was doubled. They concluded that there normally is a great deal of incon- gruity at the radiocarpal joint. They also found that 60 per cent of the radial load normally is borne by the scaphoid facet and 40 per cent, by the lunate facet’. Honii et al.’ and Viegas et al.5 calculated the load distribution at the mid-carpal joint. Honii et al. reported that 31 per cent of the total axial load was transmit- ted through the scaphoid-trapezium-trapezoid joint; 19 per cent, through the scapholunate joint; 29 per cent. through the capitolunate joint: and 21 per cent. through the tniquetrohamate joint. Viegas Ct al. reported similar data. The areas that transmitted the higher loads come- lated well with the reported distribution of osteoarthro- sis at the radiocarpal and mid-carpal levels”. Carpal Instability Carpal instability is defined as carpal malalign- ment. Therefore, all wrist dislocations. such as a perilu-
  5. 5. Radial deviation #{247} Fi;. 6-A 4k”) I.. K. RUBY IHE JOURNAL OF BONE ANt) JOINT SURGERY nate dislocation, and all wrist subluxations, such as a scapholunate dissociation. are examples of carpal insta- hility. Carpal instability is not always synonymous with increased joint laxity, as a malaligned wrist may he very stiff. It also is important to realize that not all unstable wrists are painful. The present discussion will be limited to the diagnosis and treatment of some of the more common and suhtle intercarpal instabilities (that is. subluxations). Classification There is no universally accepted classification of wrist instability. In my opinion. the system that is based Ofl the row theory of wrist motion is the most logical and best fits the known clinically important instabilities. Ac- cording to Linscheid et al.’5, most instabilities can be thought of as mid-carpal malalignments. These mid- carpal malalignments can he classified either as dorsal intercalated-segment instability (commonly known as DISI) or as volar intercalated-segment instability (com- monly known as VlSI). In dorsal intercalated-segment instability. the proximal row (as defined by the long axis of the lunate) is extended with respect to the radius on lateral radiographs. In volar intercalated-segment insta- hility. the proximal row is flexed with respect to the radius on lateral radiographs. These patterns can be sub- divided further into non-dissociative and dissociative carpal instability4”. In non-dissociative canpal instability, the proximal row is intact: in dissociative carpal instabil- ity. as occurs in association with a fracture of the scaph- oid, the proximal row is not intact. Thus, there are four basic patterns of carpal instability that can he seen on posteroanterior and lateral radiographs of the wrist: non- dissociative and dissociative dorsal intercalated-segment instability. and non-dissociative and dissociative volar intercalated-segment instability. This system of classification can he expanded to in- elude radiocarpal and axial malalignment as well. hut these patterns are less common and are beyond the scope of the present discussion. Additional subdivision based on the time since the injury (that is. as acute or chronic) is possible. Dynamic instabilities that, by defi- nition, are produced only by evocative or stress maneu- vers4’ can he added to expand further the system of classification. The clinical importance of dynamic in- stabilities is controversial and will not be considered here. Clinical Diagnosis Symptoms of wrist instability include pain, weak- ness, giving-way, and a so-called clunk, snap, or click during use. Physical examination may reveal tenderness in an area in which synovitis has developed in response to the overloading of articular surfaces. In the acute situation. the torn ligaments may be discretely tender: however. wrist pain often is difficult for the patient and physician to localize. There are several provocative ma- Figs. 6-A and 6-B: Diagrams showing the relative motion of se- lected carpal hones with respect to one another and to the radius. The numbers indicate degrees of motion. Fig. 6-A: Relative motion as the wrist moves from radial to ulnar deviation. Note the minimum amount of motion between the bones of the proximal row. neuvers that can be helpful. Watson et al.5 described a maneuver for the detection of scapholunate dissociation in which the examiner moves the wrist of the patient from ulnar to radial deviation while maintaining don- sally directed pressure over the scaphoid tubercle to prevent flexion of the scaphoid and to cause the proxi- mal pole of the scaphoid to subluxate over the dorsal edge of the radius. A positive result was defined as a characteristic painful clunk on reduction of the proxi- mal pole of the scaphoid into its radial facet as the examiner moves the wrist of the patient back into ulnar deviation. Reagan et al.7 used a ballottement test for the detection of tniquetrolunate dissociation; a positive re- sult was defined as the ability to displace the tniquetrum in a dorsal-to-volar direction with respect to the lunate. Non-dissociative volar intercalated-segment instability’ is considered to be present if a characteristic clunk. sig- nifying sudden extension or flexion of the proximal row, occurs as the examiner moves the wrist of the patient from radial to ulnar deviation and hack while placing axial compression on the hand. Plain radiographs can be used to screen for carpal instability. Routine studies should include a true lateral radiograph as well as posteroantenior radiographs made with the wrist in neutral, in radial deviation, and in ulnar deviation. Radiographs of the contralateral wrist can be
  6. 6. FIG. 6-B Relative motion as the wrist moves from flexion to extension. FIG. 7-A Fo. 7-B CARPAL INSTABILITY 481 VOL. 77.A, NO. 3. MARCH 1995 made for comparison. In scapholunate dissociation (dis- sociative dorsal intercalated-segment instability), the lateral radiograph shows an increased scapholunate an- gle of more than 60 degrees, dorsal angulation of the lunate and the tniquetrum, and an increased capitolu- nate angle of more than 15 degrees. The postenoantenior radiognaphs made with the wrist in neutral and in ulnar deviation show an increase in the scapholunate interval of more than four millimeters compared with the non- mal side; a so-called ring sign; and an increased overlap of the lunate and the capitate, with the blunt volan pole of the lunate projecting through the head of the capitate (Figs. 7-A and 7-B). The ring sign is a radiographic phe- nomenon in which the distal half of the scaphoid is seen end-on because of the abnormally vertical position of the bone. In this condition, there also is decreased carpal height as determined by the fixed ratio between the length of the third metacarpal and the length of a line drawn from the base of the third metacarpal to the distal pant of the radius on the posteroantenion radiograph made with the wrist in the neutral position; the normal ratio2#{176}is 0.54 ± 0.02. When a patient has tniquetrolunate instability (dis- sociative volar intercalated-segment instability), the posteroantenion radiograph shows a flexed scaphoid (that is, a positive ring sign) and a flexed lunate, with the sharp dorsal pole of the lunate overlapping the capitate (Fig. 8-A). In addition, there is a step-off at the tniquetrolunate joint, with the triquetrum proxi- mal to the lunate in ulnan deviation and distal to it in radial deviation. The lateral radiograph shows a de- creased scapholunate angle of less than 30 degrees and volar flexion of the lunate and the scaphoid (Fig. 8-B). In non-dissociative volan intercalated-segment insta- bility, the postenoantenion radiograph shows flexion of the entire proximal row (as evidenced by the sharp dorsal pole of the lunate overlapping the capitate) but no scapholunate gap on triquetrolunate step-off (Fig. 9-A). The lateral radiograph shows a reduced or non- mal scapholunate angle, flexion of the lunate, and a decreased capitolunate angle of less than 15 degrees (Fig. 9-B). Anthrognaphy has been the traditional next step af- ten stress radiography in the diagnosis of carpal insta- bility because it is technically straightforward and only minimally invasive and because it can demonstrate de- Figs. 7-A and 7-B: Radiographs of a wrist in which there is a scapholunate dissociation. Fig. 7-A: Posteroanterior radiograph showing a scapholunate gap of more than four millimeters, a palmar flexed scaphoid (S) (the ring sign), and an extended lunate (L) and triquetrum (T). H = hamate and R = radius. Fig. 7-B: Lateral radiograph showing the palmar flexed scaphoid with dorsal subluxation of the proximal pole of the scaphoid and the extended lunate and triquetrum.
  7. 7. Ft.. 8-A Fia. 8-B 482 L. K. RUBY THE JOURNAL OF BONE ANI) JOINT SURGERY Figs. 8-A and 8-B: Radiographs of a wrist in which there is a triquetrolunate dissociation. (‘= capitate. II = hamate. 1. = lunate. R = radius, S = scaphoid. and T = triquetrurn. Fig. 8-A: Posteroanterior radiograph showing a flexed scaphoid (the ring sign) and a flexed lunate. with the sharp dorsal pole of the lunate overlapping the capitate. There is a step-off at the triquetrolunate joint. with the triquetrum proximal to the lunate. Fig. 8-B: Lateral radiograph showing a decreased scapholunate angle and volar flexion of the lunate and the scaphoid. fects of the scapholunate interosseous ligament. the tniquetrolunate interosseous ligament. and the tniangu- lam fibrocartilage complex reasonably welP’. Greater sensitivity (that is. a lower false-negative rate) can be achieved by injection of the contrast medium into the mid-carpal joint’. However, arthrography does not reli- ably demonstrate the degree or the exact location of interosseous-ligament damage. subtle ligamentous lax- ity, the condition of the articulan surfaces, or small de- grees of synovitis22. Other non-invasive modalities that I occasionally find useful include cineradiography. stress radiography. bone-scanning. and magnetic resonance imaging. Al- though magnetic resonance imaging is an excellent tech- nique for the detection of avascular necrosis, it currently is not cost-effective for the detection of partial tears of the ligaments of the wrist3. Because of the limitations of arthrography and other non-invasive diagnostic modalities, arthroscopy is becoming more popular for the evaluation of patients suspected of having carpal instability94. In my experi- ence, anthroscopy often has led to a definitive diagno- sis and arthroscopically guided treatment often has been successful. With arthroscopy, the extent and exact location of ligamentous injuries; the condition of the articulan surface: the presence and location of synovitis; and, in some instances, the degree of carpal displace- ment can be ascertained. The disadvantages of this tech- Figs. 9-A and 9-B: Radiographs of a wrist in whtch there is non-dissociative volar intercalated-segment instability. C = capitate. H = hamate. L = lunate. R = radius. S = scaphoid. and T = triquetrum. Fig. 9-A: Posteroanterior radiograph showing flexion of the entire proximal row. Note the lack of any triquetrolunate step-off or scapholunate gap. Fig. 9-B: Lateral radiograph showing the decreased scapholunate angle. The appearance is the same as that of dissociative volar intercalated-segment instability because the triquetrum is difficult to visualize.
  8. 8. FI1. 10 CARPAL INSTABILITY 483 VOL. 77.A, NO. 3. MARCH 1995 nique include a steep learning curve, an increased risk of nerve and tendon damage, and increased expense. Treatment of Selected Carpal Instabilities Dissociative Dorsal Intercalated-Segment Instability: Scapholunate Dissociation A patient who has an acute complete scapholunate dissociation often has a history of a donsiflexion injury after a fall with immediate pain and tenderness at the scapholunate interval. Plain radiographs show the char- actenistic changes noted previously: a scapholunate gap of more than four millimeters, palmam flexion of the scaphoid with dorsal subluxation of the proximal pole, and an extended lunate and tniquetrum (Figs. 7-A and 7-B). If there still is uncertainty as to the diagnosis, arthrography or arthroscopy, on both, can be performed. For an acute injury (one that occurred less than six weeks previously) with a partial tear of the scapholu- nate interosseous ligament, closed reduction and an- throscopically and radiographically guided pinning can be performed. Closed reduction is performed with the patient under axillary block or general anesthesia by first translating the capitate (and distal row) volanly with respect to the lunate and stabilizing the capitolu- nate joint with a smooth 0.062-inch (0.157-centimeter) Kirschner wire. The scapholunate gap then is closed by direct volarly directed thumb pressure on the proxi- mal pole of the scaphoid and stabilized either with multiple 0.045-inch (0.1 14-centimeter) Kirschner wires across the scapholunate interval or with one 0.062-inch (0.157-centimeter) wire placed across the scapholunate joint and another across the scaphocapitate joint (Fig. 10). The wires are cut off under the skin and left in place for eight to ten weeks while the hand and wrist are supported in a below-the-elbow cast that extends from the metacarpophalangeal joints to distal to the elbow. After removal of the wires, range-of-motion and wrist- strengthening exercises are begun, and the wrist is protected with a removable splint until three to four months after the operation. For complete injuries of the scapholunate intenos- seous ligament or more chronic conditions, open reduc- tion and formal ligamentous repair, reconstruction, or even anthrodesis usually is necessary because reduction and adequate fixation cannot be achieved with closed means9’5. A dorsal approach is used for visualization of the tear of the scapholunate interosseous ligament, the displaced proximal pole of the scaphoid, the extended lunate, and the dorsally displaced proximal head of the capitate (Fig. 11. A). Kirschner wires are placed in the scaphoid and lunate and used as joysticks to aid in me- duction. The lunate facet of the scaphoid is cleared of scar tissue, and a trough is created. Drill-holes are placed in this trough, and heavy non-absorbable sutures are placed in the ligamentous remnant that is attached to the lunate (Fig. 1 1 . B and C). The sutures are passed through the drill-holes in the scaphoid (Fig. 11, D).The Posteroanterior radiograph made after open reduction and in- ternal fixation of a scapholunate dissociation (dorsal intercalated- segment instability). The capitolunate wire was placed first. and then the scapholunate and scaphocapitate wires were placed. dissociation is reduced and stabilized with 0.062-inch (0.157-centimeter) Kirschner wires as described pre- viously, and the sutures are tied (Fig. 11, E and F). The adjacent dorsal capsule of the wrist can be imbnicated to reinforce the primary repair. The postoperative care is the same as that for the acute injury. If the dissociation is irreducible, osteoarthrosis al- ready has occurred, or soft-tissue repair has failed, I prefer to perform a total mid-carpal or a complete wrist arthrodesis. This is a controversial area, and many au- thors have recommended a more limited arthrodesis, such as a scaphoid-trapezium-trapezoid anthrodesis for chronic instability without osteoarthrosis or a capitate- hamate-tniquetnum-lunate (four-corner) arthnodesis and scaphoid excision if osteoarthrosis is present43. Scapholu- nate, capitolunate, and scaphocapitate anthrodeses and capitate-hamate-tniquetrum-lunate arthrodeses without excision of the scaphoid also have been used for the treatment of chronic instability”39. My experience and a careful review of the literature both have demonstrated high rates of complications and unpredictable results after all of these partial arthrodeses. Dissociative Volar Intercalated-Segment Instability: Triquetrolunate Dissociation A patient who has an acute tniquetnolunate dissocia- tion often has a history of a notational injury of the wrist, commonly as the result of holding a power drill when the drill bit has jammed. The patient has pain in the wrist on
  9. 9. A 5. ,/ I 1 C I 1 .. F N ,,,t.T ) E 1.’ F N. FIG. 11 THE JOURNAL OF BONE ANI) JOINT SURGERY 484 I.. K. RUBY B Drawings showing the repair of a scapholunate interosseous ligament with adjunct capsular repair. A, The tear in the scapholunate interosseous ligament (SLIL) is visualized through a dorsal approach (L = lunate. R = radius. and S = scaphoid). B. Horizontal mattress sutures of 0 non-absorbable material are placed in the ligament. C. A trough is created along the lunate facet of the scaphoid. and drill-holes are placed from the scaphoid waist to the trough. D. Keith needles are used to pass the sutures through the drill-holes. E and F,The scaphoid. lunate, and capitate are reduced and pinned. after which the sutures are tied. (Modified, with permission. from: Lavernia. C. J.; Cohen, M. S.; and liileisnik.J.:Treatment ofscapholunate dissociation by ligamentous repair and capsulodesis.J. Hand Surg.. 17A: 355. 1992.)
  10. 10. FIG. 12-A FIG. 12-B Figs. 12-A and 12-B: Radiographs of a malunited fracture of the distal part of the radius with secondary non-dissociative dorsal intercalated-segment instability. Fig. I 2-A: Posteroanterior radiograph. Note the dorsiflexed position of the entire proximal row. Fig. 12-B: Lateral radiograph. CARPAL INSTABILITY 485 ‘OI.. 77-A. NO. 3. MARCh 1995 the ulnar side. especially at the tniquetrolunate joint. The examiner must he careful to distinguish this injury from injuries of the triangular fibrocartilage com- plex. which usually cause tenderness in the interval be- tween the extensor carpi ulnanis and the flexor carpi ulnanis just distal to the ulnar head. The result of a hallottement test may be positive. as described pre- viously. The diagnosis is confirmed by the presence of a step-off at the tniquetrolunate interval on the postero- anterior radiograph. Arthroscopic confirmation of the tear may he necessary. If there is no volar instability (indicating only a partial tear), percutaneous pinning guided by arthroscopy or radiography, or both, is recom- mended. If volar instability has developed or the de- formity is chronic hut still reducible, open repair of the triquetrolunate ligament combined with dorsal capsulo- desis can he performed in a manner similar to that de- scnihed for dorsal instability. It is important to realize that. in this instance, the goal of capsulodesis is to pre- vent excessive flexion of the proximal row, particularly by imbnication of the dorsal radiotniquetral ligament. It also may he helpful to imbricate the space of Poinier on the palmar side to reinforce the dorsal repair’4. I reduce and pin the capitolunate joint before tying the capsular sutures: the use of suture anchors can facilitate this me- pair. I prefer to make the dorsal exposure first, place the sutures, and reduce and pin the wrist. I then perform the anterior approach and close the space of Poirier. If soft-tissue repair has failed or osteoanthrosis is present. mid-carpal anthrodesis is the treatment of choice. Although tniquetrolunate arthrodesis seems log- ical. high rates of failure and of complications have been reported’4. and I no longer recommend this procedure. It also has been noted4 that symptomatic tniquetrolu- nate instability often is accompanied by ulnar-head abutment. Therefore. ulnar recession osteotomy often is indicated. If there is no volar intercalated-segment instability. I prefer to treat chronic. complete. symptom- atic, irreducible tniquetrolunate teams with ulnar meces- sion osteotomy alone, especially if there is positive or neutral ulnar variance. Non-Dissociative Volar Intercalated-Segment Instability This condition is almost always a chronic problem that begins insidiously; usually. it is associated with gen- emalized ligamentous laxity. It is diagnosed on the basis of a characteristic clunk on axial compression of the wrist in radial and ulnam deviation and on the basis of the signs on plain radiogmaphs described previously. Anthrogmaphy and arthnoscopy typically reveal normal findings. As osteoarthrosis has not been shown to de- velop as a result of this instability, and because the con- dition may represent a systemic problem, non-operative treatment consisting of forearm-strengthening exercises and intermittent splinting should be tried first’. If this treatment fails, anterior and posterior capsular imbnica- tion and temporary mid-carpal pinning can be per- formed in a manner similar to the technique used for tniquetrolunate dissociation. If this procedure fails to relieve symptoms. mid-carpal anthrodesis is an option. Secondary Non-Dissociative Dorsal Intercalated-Segment Instability This pattern of instability has been recognized with increasing frequency since it was first described by Taleisnik and Watson in 1984. It is not a primary disor- den of the wrist; rather, it is an adaptive posture of proximal-now extension secondary to dorsal angulation of a malunited fracture of the distal pant of the radius (Figs. 12-A and 12-B). If the instability is symptomatic, dorsal opening-wedge connective osteotomy of the ma- dius should be curative. Summary A great deal of progress has been made in recent years with respect to understanding the normal and
  11. 11. 486 L. K. RUBY THE JOURNAL. OF BONE AND JOINT SURGERY pathological anatomy of the wrist. Nonetheless. our with a critical review of the standard radiographs. sup- knowledge is incomplete. so theme still is room for di- plemented by additional studies as indicated, allow the vemsity of opinion regarding the diagnosis and treatment astute clinician to identify specific patterns of instability of most of the presently recognized wrist instabilities. and to formulate an effective treatment program for the A careful history and physical examination combined patient. References I . Berger, R. A., and Landsmeer, J. M. E.: ihe palmar radiocarpal ligaments: a study of adult and fetal human wrist joints. ]. I/and Sung.. ISA: 847-854. 1990. 2. Botte, M. J.; Cooney, W. P.; and Linscheid. R. L.: Arthroscopy of the wrist: anatomy and technique.]. Hand Sung.. 14A: 313-316, 1989. 3. Coone W. P., III; Linscheid, R. L.; and Dobyns, J. 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  12. 12. CARPAL INSTABILITY 487 37. Viegas, S. F.; Patterson, R. M.; Peterson, P. D.; Pogue, D. J.; Jenkins, D. K.; Sweo, T. D.; and Hokanson, J. A.: Ulnar-sided perilunate instability: an anatomic and hiomechanic study.]. Hand Sung., iSA: 268-278, 1990. 38. Viegas, S. F.; Tencer, A. F.; Cantrell, J.; Chang, M.; Clegg, R.; Hicks, C.; O’Meara, C.; and Williamson, J. B.: Load transfer characteristics of the wrist. Part I. The normal joint.]. Hand Sung.. 12A: 971-978. 1987. 39. Watson. H. K., and Ballet, F. L.: The SLAC wrist: scapholunate advanced collapse pattern of degenerative arthritis. ]. bland Sung.. 9A: 358-365. 1984. 40. Watson, H. K.; Ashmead, D., IV; and Makhlouf, M. V.: Examination ofthe scaphoid.]. bland Sting., 13A: 657-660. 1988. 41. Watson, H. K.; Ottani, L.; Pitts, E. C.; and Handal, A. G.: Rotary subluxation of the scaphoid: a spectrum of instability. ]. hand Sting., 18-B: 62-64, 1993. 42. Weber, E. R.: Concepts governing the rotational shift of the intercalated segment of the carpus. Ontliop. C/in. North A,nenica. 15: 193-207. 1984. 43. Weil, C.. and Rub L. K.: The dorsal approach to the wrist revisited.]. Hand Sung., I IA: 91 1-912. 1986. 44. Zinberg. E. M.: Coren, A. B.; Levinsohn, E. M.; and Palmer, A. K.: The triple injection wrist arthrogram labstract]. ]. biwul Sung.. 13A: 308. 1988. Vol.. 77-A. NO. 3. MARCEl 995

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