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3. 4. 5. 6.

7.

8.

a gross and histologic description. Anat Rec 1984;210: 393-405. Taleisnik J. The ligaments of the wrist. J HAND SURG 1976;IA(2):11O-18. Testut L. Traite d'anatornic humaine. Paris: Gaston Doin and Company, 1928:628-30. Mayfield JK. Mechanisms of carpal injuries. Clin Orthop 1980; 149:45-54. Mayfield JK, Johnson RP, Kilcoyne RK. Carpal dislocations: pathomechanics and progressive perilunar instability. J HAND SURG 1980;5(3):226-41. Williams WJ, Mayfield JK, Erdman AG, et al. Biornechanical properties of human carpal ligaments. Orthop Trans 1979;4:26. Hixson ML, .Stewart M. Microvascular anatomy of the radioscapholunate ligament of the wrist. J HAND SURG 1990; 15A(2):279-82.

Study oj radioscapliolunate ligament

9. Tinkelenberg J. Graphic reconstruction, microanatomy with a pencil. J Audiov Media Med 1979;2: 102-6. 10. Berger RA, Landsmeers JMF. The palmar radiocarpal ligaments: a study of adult and fetal human wrist joints. J HAND SURG (In press.) 11. Landsmeer JMF. Atlas of anatomy ofthe hand. New York: Churchi1l Livingstone, 1976:11-32. 12. Janevski BK. Angiography of the upper extremity. The Hague: Martinus Nuhoff, 1982:71-3. 13. Lewis OJ. The development of the human wrist joint during the fetal period. Anat Rec 1970;166(3):499-516. 14. Buck-Grarnko D. Denervation of the wrist joint. J HAND SURG 1977;2A(I):54-61. 15. Dellon AL, MacKinnon SE, Daneshvar A. Terminal branch of anterior interosseous nerve as source of wrist pain. J HAND SURG 1984;9B(3):316-22.

A kinematic study of luno-triquetral dissociations An analysis of carpal motion after sectioning the ligamentous support of the luno-trlquctral joints was done by use of stereoradiographic methods. The ligaments were sectioned in two stages. In stage I, a complete sectioning of both the dorsal and palmar luno-triquetral ligaments and the interosseous membrane was done. Stage II consisted of further sectioning of both the dorsal radlo-trlquetral and dorsal scapho-triquetral ligaments. After both stage I and stage II Iigment sectioning, all of the intercarpal joints exhibited altered kinematics. The changes were especially marked at the luno-triquetral joint where motion was increased in all planes of wrist motion. The essential lesion in producing a static palmar flexed intercalated segment instability was division of the dorsal radio-triquetra! and dorsal scapho-trlquetral ligaments in association with the luno-triquetral ligaments and interosseous membrane sectioning. (J HAND SURG 1991; 16A:355·62.) .

E. Horii, MD, M. Garcia-Elias, MD, K. N. An, PhD, A. T. Bishop, MD, , W. P. Cooney, MD, R. L. Linscheid, MD, and E. Y. S. Chao, PhD, Rochester, Minn.

From the Biomechanics Laboratory, Department of Orthopedics, Mayo Clinic/Mayo Foundation, Rochester, Minn. Supported by a grant from the OREF No. 88471. Received for publication Aug. 17, 19898; acepted in revised form Dec. 7, 1989. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to ihe subject of this article. Reprint requests: Kai-Nan An, PhD, Biomechanics Laboratory, Department of Orhtopedics, Mayo Clinic/Foundation, Rochester. MN 55905. 3/1120959

Since Linscheid and Dobyns'? introduced the concept of traumatic carpal instabilities, much has been written about their clinical features, treatment, and long-term consequences. Two types of carpal instability have been recognized; one resulting in an abnormal volar flexion of the lunate (VIS I) and another producing abnormal dorsi-flexion of the lunate (DISI). Ligamentous injuries between proximal carpal bones cause specific types of carpal instability. Scapholunate dissociations are a frequently acknowledged cause of DIS!. This type of instability has received considerable

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356

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Palmar

Dorsal

B

Dorsal

Fig. 1. A-B, Schematic drawing of the luno-triquetral joint supporting ligaments. A, In stage I . the dorsal and palmar luno-triquetral Iigaments and interosseous membrane (1,2) were completely sectioned. B, In stage II the dorsal scapho-triquetral (3) and dorsal radio-triquetral (4) ligaments were sectioned close to the insertion: (1), Palmar luno-triquetral; (2), dorsal luno-triquetral; (3), dorsal scapho-triquetral; (4), dorsal radio-triquetral; (5), palmar triquetral-hamate; (6), palmar triquetrum-capitate; (7), ulno-triquetrum; (8), ulno-lunate ligament.

y

z x

common. Reagan and associates? showed that there was substantial abnormal motion of the carpus in patients with severe LTq sprains. Such kinematic changes, however, have not been quantified. Determination of carpal motion using carpal angles from orthogonal radiographs taken in different wrist positions does not seem to be a feasible approach. The triquetrum can not be easily recognized on lateral projections of the wrist because of superimposition of the other carpal bones. The question remains whether isolated LTq ligament injuries produce VISI or not, and, what are the specific pathokinematic changes that occur after LTq ligaments rupture. This study did a quantitative analysis of carpal kinematicsafter different grade division of the LTq joint supporting ligaments.

Materials and methods STAGE II Fig. 2. Schematic representation from a dorsal view of the abnormal rotation in neutral position experienced by the proximal carpal row bones after stage II. The lunate expressed a palmar rotation, while the triquetrum rotated in a supinatory motion. A dorsal widening between the lunate and the triquetrum was consistently seen.

attention both from a clinical and experimental perspective." By contrast, the dissociative pattern of carpal instability resulting from Iuno-triquetral (LTq) dissociations is less well understood. Although a few clinical series have been reported.i" such an injury is not un-

Five freshly frozen cadaver upper extremities without any detectable pathology were used in this investigation. The carpal bones were approached through a longitudinal mid-dorsal incision. Care was taken to protect radiocarpal and intercarpal ligaments. Small metal markers were embedded into the radius, scaphoid, capitate, lunate, triquetrum, and hamate. A minimum of three markers in each carpal bone are required for rigid body motion analysis. In this study, however, four markers were used to optimize accuracy of bone motion measurements. Different sized markers were selected to facilitate recognition of the different bones on the radiographs. The specimens .were firmly mounted in a specially designed testing frame with two Steinmann pins through

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the radius and ulna with the forearm in neutral rotation. The five wrist motor tendons (extensor carpi radialis brevis and longus, extensor carpi ulnaris , and flexor carpi radialis and ulnaris) were connected to calibrated springs by strong suture material. Different loads were applied to the tendons to simulate five different wrist positions (neutral, maximum radial deviation, maximum ulnar deviation, extension, and flexion). The magnitude of the loads applied were determined according to the physiologic cross-sectional areas and the electromyographic activity of each of the muscles associated with wrist motion." A total of 9 kg of compressive load was applied. Biplanar radiographs with calibration metal markers were obtained for all five positions. Skin incisions were then reopened, and sequential divisions of the LTq joint supporting structures were done. In stage I, the dorsal and palmar LTq ligaments and interosseous membrane were completely sectioned (Fig. I, A). 'Biplanar radiographs were obtained again in each wrist position under the same loading conditions. In stage II, the dorsal radio-triquetral and scaphotriquetralligments were sectioned, and the radiographic study was repeated (Fig. 1, B). The radiographs were then digitized with use of an electrostatic magnetic digitizer (Hipad Co., Houston Instruments, Austin, Texas) and the data were analyzed with use of a specially developed software program , which calculates spatial rigid body motion using the method of Spoor and Veldpaus.'? Relative carpal bone motions were described as rotations around the translations along a unique screw axis following the "screw displacement axis" concept. II The orientation and position of the screw axis for defining the kinematics were designed based on the global coordinate system (X. Y, Z) attached on the distal radius (Fig. 2). The X axis is defined along the shaft of the radius positive sense points proximally. The rotation about the X axis represents supination/pronation: .The Y axis is the transverse axis in the frontal plane with positive sense toward the ulnar direction. The rotation about the Y axis represents flexion/extension. Finally, the Z axis is the transverse axis in the sagittal plane with positive toward a palmar direction. The rotation along the Z axis represents radial/ulnar deviation (Fig. 2). Further details about the methods used in this study can be found in previous publications. 12·14 Differences in kinematics between intact, stage I, and stage II were noted, and validated statistically by analysis of variance (ANOYA). Results Normal kinematics of the ulnar side of the carpus. The intact ulnar side of the carpus behaved similarly to the rest of the carpus in flexion/extension motion with synchronous motion of the proximal (trique-

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Table I. Intact proximal row intercarpal motion from the neutral position (n = 5) Rotation angle around a screw axis (mean ± SD. degree)

Radial deviation Ulnar deviation Extension Flexion

Luna-triquetrum

Scapha-lunate

± 8 7 ± 2 13 ± 4 8 ± 3

7 ::!: 3 8 ± 3

12

25 ::!: 4 14 ± 9

trum) and distal (hamate) rows . By contrast, during , radial/ulnar deviation the interaction between the triquetrum and the hamate caused asynchronous motion within each row. During ulnar deviation, as the hamate glided down the triquetrum, it rotated 20 ± 2 degrees (mean ± SD) around the axis (X = -0.44, Y = 0.77, Z = -0.45). The values of X. Y. and Z, represent the component of the XYZ direction of the unit vector along the screw axis of rotation. The larger value of Y, for example, indicates that the dominant component of rotation is flexion . The nearly identical negative values of X and Z mean that the same amounts of pronation and ulnar deviation are involved in this motion. This combined motion resulted in maximal coaptation of the respective articular surfaces between the triquetrum and hamate. In radial deviation, the relative motion of the hamate with respect to the triquetrum was 16 ± 3 degrees of rotation, which consisted of supination, extension, and radial deviation (X = 0.12, Y = -0.46, Z = 0.87) the two bones became disengaged from each other. 15. 16 Maximum intercarpal motion between the lunate and the triquetrum was almost equal in flexion/extension and radial/ulnar deviation. This was in contrast to scapho-Iunate joint motion, which had twice the amount of motion during wrist flexion/extension as it had during radial/ulnar deviation (Table I). Effects of sectioning the ligaments on the carpal alignment with wrist in neutral position. After both stages I and II of ligament sectioning, the spatial orientation of the proximal carpal bones with the wrist in the neutral position was found to have changed. After stage I, the proximal carpal row bones changed their positions and alignment an average of 5 degrees with respect to the distal radius. The direction of rotation, however, was not uniform in all the specimens. After stage II, the carpal malalignment increased in a consistent fashion (Table II). The scaphoid supinated and radial deviated, the lunate supinated and flexed. The triquetrum rotated 14 degrees around an axis

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Table II. Effects of ligament sectioning on carpal alignment in neutral wrist position. Rotation of proximal carpal row with respect to the radius, in comparison to intact Unit vector of screw axis'

X Scaphoid

Stage Stage Stage Stage Stage Stage

Lunate Triquetrum

I II I II I II

I

0.54 0.56 0.99 0.94 0.71 0.86

I

y

Rotation angle (mean ± SD, degree)

Z

-0.51 -0.23 -0.19 0.33 0.66 0.50

0.67 0.80 -0.01 0.06 0.24 0.09

± 2 ± 3 ± 2 ± 8 ± 0.5 ± 4t

6 8 5 10 3 14

+ ·X. Supination Y. Flexion

Pronation Extension

Z.RD

UD

tp < 0.05 compared to stage I (Ar-;OVA).

Table III. Kinematics of carpal bones with respect to the radius: From neutral wrist position to radial/ulnar deviation (11 = 5) Rotation angle (mean ± SD. degree) Radial deviation Scaphoid

Lunate

Triquetrum

Intact Stage Stage Intact Stage Stage Intact Stage Stage

I II I II I II

13 15 19 13 14 17 12 16 21

± ± ± ± ± ± ± ± ±

Ulnar deviation

7 8 II 7 8 14 7 8 13

23 27 31 25 29 35 23 24 27

± ± ± ± ± ± ± ± ±

6 7 7 7 9 II 7 4 3

Table IV. Relative motion of the triquetrum with reference to the lunate in each wrist position (mean ± SD, degree)

,\t"

motion

Stage

Intact Stage I Stage II

Radial deviation 12 ± 8" 12 ± 9' 17 ± II'

Ulnar deviation 7 ± 2b 12 ± 4b 24 ± 10'

'Within a column, rows with superscripts of differing letters are significantly different from each other (p

(X = 0.86, Y = 0.50, Z = 0.09), which involved mostly supinatory motion (Fig. 2). In the anteriorposterior radiograph, a step off between the lunate and the triquetrum was observed. On the lateral radiograph, the lunate rotated in a palmar-flexion (Fig. 3). Kinematic changes after ligament sectioning. Stage I. After stage I, rotation of the proximal carpal row bones with respect to the distal radius increased slightly in each wrist motion. The relative motion be-

Extension 13 ± 4b 15 ± 3'" 21 ± 4'

Flexion

8 ± 3b II ± 3b 26 ± 9'

< 0.05)

tween the lunate and the triquetrum also increased slightly (Tables III and IV). However, these changes were not statistically significant. In addition, no abnormal motion was detected on the AP and lateral radiographs. Stage ll. Although the global range of wrist motion did not change significantly, abnormal kinematics of the carpus were detected after stage II of ligament injury (Table III). Changes were observed at almost every

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Fig. 3. A·D, Films showing intact and stage II wrists. Symbols represent metal markers for: Scaphoid, A; lunate, 0; triquetrum, 0, respectively. A·B, Intact wrist. C·D, Stage II. The AP view shows the step off between the lunate and the triquetrum. The lateral view shows the palmar-flexed lunate.

carpal articulation, but they were especially significant at the LTq joint where hypennobility was consistently found (Table IV). During ulnar deviation of the wrist, loss of the lunotriquetral constraint allowed the scaphoid and the lunate

to rotate into an abnormally extended position. The triquetrum, being disengaged from the lunate, did not follow the extension motion. Despite the fact that the hamate still had an influence on the triquetrum and influenced the direction of motion, the direction of tri-

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y

x

x

A

y

INTACT

B

STAGE II

Fig. 4. A·B, Schematic drawing of a palmar view of kinematic changes of the carpal bones from neutral to ulnar deviation. Arrows rep..esent the direction of the axis and rotation of the carpal bone around the axis . A, Intact wrist. The proximal carpal bones rotate around the axis representin g extension and ulnar deviation with respect to the radius. B, After stage II. The scaphoid and the lunate rotated to a more extended position. While the rotation axis of the triquetrum changed the direction expressing more ulnar deviation and less extension .

quetrum rotation was changed resulting in more ulnar deviation and less extension. The relative motion between the lunate and the triquetrum increased from 7 to 24 degrees. On the AP view of the radiograph, the normal convex arch of the proximal row was disrupted and the triquetrum exhibited a modest amount of proximal migration (Fig. 4). All of these differences are a manifestation of carpal instability of the dissociative type. 3 During radial deviation there was a loss of the lunotriquetral constraint that resulted in excesive flexion of the scaphoid and lunate . The triquetrum, however, continued to follow hamate motion being induced by the intact triquetro-hamate ligament. Although rotation of each carpal bone increased, the relative motion between the lunate and the triquetrum was not significantly different from the intact wrist. During flexion and extension of the wrist, the relative motion between the lunate and the-triquetrum was twice as much after stage II as it was for the intact wrist (Table IV). The triquetrum experienced not only increased rotation in the direct ion of flexion/extension motion but also experienced a larger degree of supination during wrist flexion and more pronation in wrist extension than when the wrist ligaments were intact.

Discussion Considerable clinical interest is currently being focused on LTq dissociations . This type of injury may occur from a variety of mechanisms and Is a frequent cause of pain on the ulnar side of the wrist. 6-8 It must be differentiated from other ulnar-side wristsyndromes such as extensor carpi ulnaris tendinitis, injuries of the triangular fibrocartilage, distal radioulnar joint disturbances, pisotriquetral arthrosis, chondromalacia of the lunate and distal ulna, as well as nondissociative instability.": 19 Because there is a lack of obvious radiographic landmarks, and with a close proximity to other . carpal structures, the usual radiographic methods of diagnosing carpal instability are inadequate to investigate the pathokinematics of luno-triquetral dissociation: The stereoradiographic method presented in this study has been applied to analysis of other carpal kinematics and the advantages and limitations of this method have been stated in prevoius papers.":" To date it is the most reliable method available for providing quantitative data about the relative motion of individual carpal bones. In this study we would like to emphasize the role of the LTq joint in overall carpal stability. Reagan and colleagues" and Viegas et al." have observed that sectioning of the LTq ligament alone caused

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little tendency for carpal collapse. In our experiment, a definite static VISI deformity could not be reproduced after the first stage of ligament sectioning. Our interpretation of this finding is that the intact dorsal radiotriquetral and the dorsal scapho-triquetral Iigaments prevented such deformity. However, increased mobility at the LTq joint was present in all specimens. Subtle changes in the LTq kinematics could not easily be detected after stage I by any simple radiographic or motion study. We believe, however, that abnormal lunotriquetral motion, although small, may be sufficient to produce synovitis, wear ofjoint cartilage, and abnormal ligamentous tension, and results in clinically apparent wrist pain. Since the LTq ligaments not only transmit forces but also constrain motion between the lunate and the triquetrum allowing mutual control, they arc therefore important for normal kinematics . Further sectioning of the ligaments revealed carpal bone malalignment more clearly. The absence of the dorsal radio-triquetral and scapho-triquetral ligaments allowed the lunate to adopt a palmar-flexed position consistent with a VISI pattern of carpal instability. Integrity of these dorsal ligaments are, therefore, the essential constraint to maintain normal carpal stability in the absence of the LTq ligaments. In this stage, subtle disruption of the normal convex arc of the proximal row was also observed (Fig. 3). Malrotation of the triquetrum, however, was still not easy to detect on regular radiographs. The presence of clicking on the ulnar side of the wrist is a well-known physical finding in patients with a LTq dissociation.':" In our study, this was obvious after stage II. When the wrist was deviated from neutral to ulnar deviation under axial compression, the lunate abruptly rotated from a palmar-flexed to a dorsi-flexed position producing an audible clunk. The clunk and feeling of instability could be enhanced by pushing the capitate pal marly. Lichtmanet al." reported a similar phenomenon in an experimental. study of ulnar midcarpal instability. The maneuver of moving the wrist from neutral to ulnar deviation with axial compression may elicit dynamic LTq instability, as well as midcarpal instability. This study has demonstrated the importance of the dorsal scapho-triquetral and radio-triquetral ligaments in regulating lunate rotation. Time-dependent attenuation of supporting ligaments after initial injury might have the same effect as sectioning the additional ligaments in stage II. These findings might explain the endstage changes observed in chronic luno-triquetral ligamentous tears; that is, insidious ulnar-sided wrist pain, static VIS I collapse secondary to progressive stretch

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of surrounding ligaments, and eventual degenerative changes about the triquetrum and throughout the carpus . Incompetence of other carpal ligaments, such as the palmar luno-triquetral , triquetrum-capitate, and triquetrum-hamate, does not seem essential for preventing such abnormalities to occur. This specific point will be substantiated in a future study. Conclusions

A complete injury of the LTq ligaments results in increased mobility of the triquetrum but does not show a static VIS I deformity. If the dorsal radio-triquetral and scapho-triquetral ligaments are sectioned in addition, the lunate consistently adopts a palmar-flexed position, the triquetrum rotates into supination and eventually VISI pattern of carpal instability.

REFERENCES I. Linscheid RL, DobynsJH, BeaboutJW, Bryan RS. Traumatic instability of the wrist . J Bone Joint Surg 1972;54A: 1612-32. 2. Dobyns JH. Carpal instability non-dissociative . ASSH Instructional Course. September 16, 1988. 3. Cooney WP, Garcia-Elias M, Dobyns JH, Linscheid RL. Anatomy and mechanics of carpal instability. Surg Rounds Orthop 1989;3:15-24. 4. Ruby LK, Cooney III WP, An KN, Linscheid RL, Chao EYS. The effect of scapho-lunate ligament section on scapholunate motion . J HAND SURG 1987;12A:767-71. 5. Lichtman DM, Noble III WH, Alexander CEo Dynamic triquetrolunate instability: case report . J HAND SURG 1984;9A: 185-8. 6. Reagan DS, Linscheid RL, Dobyns JH. Lunotriquetral sprains. J HAND SURG 1984;9A:502-14. 7. Osterman AL, Bora FW, Maitin E. Lunato-triquetral instability treated by limited lunato-triquetral fusion. Orthopedic Trans 1988;12:11. 8. Paul G, Young VL, Gilula LA, Weeks PM. Management of chronic lunotriquetral ligament tears. J HAND SURG 1989;14A:77-83. 9. Gross RM, Chao EYS, An KN, Linscheid RL. Quantitative analysis of the forearm and wrist muscles. Transactions of the 23 annual meeting of DRS 1977:215. 10. Spoor CW, Veldpaus FE. Rigid body motion calculated from spatial co-ordinates of markers. J Biomechanics 1980;13:391-3. 11. An KN, Chao EYS. Kinematic analysis of human movement. Ann Biomed Eng 1984;12:585-97. 12. Ruby LK, Cooney III WP, An KN, Linscheid RL, Chao EYS . Relative motion of selected carpal bones: a kinematic analysis of the normal wrist. J HAND SURG 1988;13A:I-IO. 13. Garcia-Elias M, Cooney WP, An KN, Linscheid RL,

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Chao EYS. Wrist kinematic after limited intercarpal arthrodesis . J HAND SURG 1989;14A :791-9. 14. Smith OK, Cooney WP, An KN, Linscheid RL, Chao EYS. The effects of simul ated unstable scaphoid fractures on carpal motion. J HAND SURG 1989;14A:283-91. 15. Taleisnik J . Carpal kinematics. In: The wrist. New York: Churchill Livingstone, 1985:39-49. 16. Weber ERA . Wrist mechanics and its association with ligamentous instability. In: The wrist and its disorders. Philadelphia: WB Saunders, 1988;41-52.

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17. Gilula LA, Destout JM, Weeks PM, et al. Roentgenographic diagnosis of the painful wrist. Clin Orhtop 1984;187:52-64. 18. Viegas SF, Patterson RM, Peterson PO, Pogue OJ, Jenkins OK, Sweo TO, Hokanson JA. Ulnar sided perilunate instability: an anatomic and biomechanic study. J HAND SURG 1990;15A:268-78. 19. Lichtman OM, Schneider JR, Swafford AR, Mak GR. Ulnar midcarpal instability-clinical laboratory analysis. J HAND SURG 1981;6A:SIS-23.

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