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Wrist Anatomy and Biomechanics
CURRENT CONCEPTS
Wrist Anatomy and Biomechanics Yasumu Kijima, MD, Steven F. Viegas, MD, PhD
O TREAT WRIST injuries or degenerative changes, it is essential to understand the anatomy, biomechanics, and function of the wrist, including the carpal ligaments. Successful diagnosis of injures, interpretation of images, and treatment depend on accurate information about the anatomic location of the normal ligamentous attachment. Although a number of articles have been published related to the anatomy and function of the carpal ligaments, recent detailed information has further elucidated the ligamentous anatomy of the wrist. This article provides a current description of the anatomy of the carpal ligaments and of the biomechanics of the wrist. Knowledge of the ligaments will further serve as a foundation for understanding the anatomy and biomechanics of the wrist and the function of individual ligaments and their roles in joint stability as well as the pathomechanics of carpal instabilities.
T
From the Department of Orthopaedic Surgery, Graduate School of Biomedical Sciences, Hiroshima University, Japan; and the Department of Orthopaedic Surgery and Rehabilitation, The University of Texas Medical Branch, Galveston, TX. Received for publication February 5, 2009; accepted in revised form July 28, 2009. The authors would like to acknowledge Mitsuhiko Nanno, MD, and Soya Nagao, MD, for their editorial assistance and contribution to this article. This article is based on Nanno M, Patterson RM, Viegas SF. Carpal ligament anatomy and biomechanics. In: Trumble T, ed. Wrist and elbow reconstruction & arthroscopy: a master skills publication. Rosemont, IL: American Society for Surgery of the Hand, 2006:3–18. No benefits in any form have been received or will be received related directly or indirectly to the subject of this article. Corresponding author: Steven F. Viegas, MD, PhD, 1521 Driftwood Lane, Galveston, TX 77551; e-mail: [email protected]. 0363-5023/09/34A08-0030$36.00/0 doi:10.1016/j.jhsa.2009.07.019
THE ANATOMY OF THE CARPAL LIGAMENTS The wrist consists of the distal ends of the radius and ulna, 8 carpal bones, and the proximal bases of the 5 metacarpal bones. The carpal bones are categorized as a proximal row and a distal row on the basis of their kinematic behavior during global wrist motion.1 The proximal carpal row consists of the scaphoid, lunate, triquetrum, and pisiform, and the distal row consists of the trapezium, trapezoid, capitate, and hamate.2 The proximal carpal row bones can be described as an intercalated segment because no tendons insert upon them, and their motion is entirely dependent on mechanical forces from their surrounding articulations.1 The distal row carpal bones are tightly bound to one another via stout intercarpal ligaments, and motion between them can be considered negligible. Similarly, the nearly rigid ligamentous connection of the trapezium and capitate to the index and middle metacarpal bones and lack of motion between these bones allows us to consider the distal row functionally as part of a fixed hand unit that moves in response to the musculotendinous forces of the forearm.1 The carpal ligaments described here have been divided by Taleisnik3 into extrinsic and intrinsic groups on the basis of their location. Extrinsic ligaments connect the distal radius and ulna to the carpal bones, and intrinsic ligaments have their origins and insertions within the carpal bones.2 Nagao et al.4 and Nanno et al.5,6 made computed tomography images of wrists, from which 3-dimensional images of the bones were modeled, and the ligament attachment areas thereupon are listed in Table 1. The presence or absence of each ligament is also noted. The attachment sites and area of the ligaments are identified by specific colors in figures in this article, and the ligament paths are displayed by semitransparent colors.
© Published by Elsevier, Inc. on behalf of the ASSH. 䉬 1555
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Anatomic and biomechanical research of the wrist has yielded a substantial amount of information that improves our basic knowledge of carpal morphology and function of the wrist and provides information to better assess and improve treatment(s) for various problems of the wrist joint. A precise knowledge of the anatomy and biomechanics of the wrist is useful not only for diagnosis of traumatic ligamentous injuries or degenerative change of the wrist joint but also for treatment for wrist dysfunction. (J Hand Surg 2009;34A:1555–1563. © 2009 Published by Elsevier Inc. on behalf of the American Society for Surgery of the Hand.) Key words Anatomy, biomechanics, ligament, wrist joint.
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TABLE 1. Individual Ligament Attachments of the Volar, Dorsal, and Interosseous Ligaments on the Lunate Volar Ligaments Location LRL SRL RSL
UL LT
DRC
DIC
SLIO
LTIO
Radius Lunate Radius Lunate Radius Scaphoid Lunate Lunate Lunate Triquetrum Radius Lunate Triquetrum Triquetrum Lunate Scaphoid Proximal Waist Trapezoid Trapezium
Area (mm2)
Specimens (n ⫽ 8)
⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾
2.9 2.5 3.8 5.6 1.7 1.9 3.2 2.7 2.2 0.8
8 8 8 8 8 8 8 4 7 7
Dorsal Ligaments 14.3 ⫾ 4.0 1.9 ⫾ 0.6 8.5 ⫾ 5.4 9.8 ⫾ 6.4 3.8 ⫾ 1.3
8 4 8 8 6
5.7 ⫾ 2.3 5.2 ⫾ 3.2 4.0 ⫾ 2.3 2.4
8 6 8 1
10.9 7.6 12.8 13.7 5.0 3.2 5.5 2.7 3.8 2.8
Interosseous Ligaments Volar Scaphoid 4.7 ⫾ 1.7 Lunate 4.9 ⫾ 1.8 Proximal Scaphoid 13.7 ⫾ 7.0 Lunate 16.3 ⫾ 5.6 Dorsal Scaphoid 4.9 ⫾ 0.8 Lunate 4.9 ⫾ 2.4 Volar Lunate 5.8 ⫾ 2.1 Triquetrum 5.2 ⫾ 2.2 Proximal Lunate 14.4 ⫾ 4.6 Triquetrum 11.7 ⫾ 3.7 Dorsal Lunate 3.9 ⫾ 2.8 Triquetrum 2.2 ⫾ 0.9
8 8 8 8 8 8 8 8 8 8 8 8
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LRL, long radiolunate ligament; SRL, short radiolunate ligament; RSL, radioscaphoid ligament; UL, ulnolunate ligament; LT, lunotriquetral ligament; DRC, dorsal radiocarpal ligament; DIC, dorsal intercarpal ligament; SLIO, scapholunate interosseous ligament; LTIO, lunotriquetral interosseous ligament. Source: Reprinted from The Journal of Hand Surgery, Volume 30, Nagao S, Patterson RM, Buford WL, Anderson CR, Shah MA, Viegas SF, Three-dimensional description of ligamentous attachments around the lunate, p. 687, Table 2. Copyright © 2005, with permission from The American Society for Surgery of the Hand.
Extrinsic ligaments Dorsal ligaments: The dorsal ligaments are important secondary stabilizers of the scapholunate joint.1
FIGURE 1: A dorsal view of a 3-dimensional model of a right wrist joint. Colored areas show the path of the ligaments. DRC, dorsal radiocarpal ligament; DIC, dorsal intercarpal ligament. Reprinted from Nagao S, Patterson RM, Buford WL Jr., Anderson CR, Shah MA, Viegas SF. Three-dimensional description of ligamentous attachments around the lunate, J Hand Surg 2005;30A:685– 692, Figure 7. Copyright © 2005, with permission from The American Society for Surgery of the Hand.
Dorsal radiocarpal ligament: The dorsal radiocarpal ligament originates proximally from the ulnar and dorsal portion of the distal end of the radius, from Lister’s tubercle to the level of the interfossal ridge between the scaphoid fossa and the lunate fossa (Fig. 1). This ligament attaches distally to the proximal and dorsal tubercle of the triquetrum and the lunate. Volar ligaments: Volar extrinsic ligaments play a major role in stabilizing the wrist.2 It is generally accepted that those on the palmar aspect provide greater restraint to instability.7 There are 3 strong palmar extrinsic radiocarpal ligaments: the radioscaphocapitate, the long radiolunate, and the short radiolunate ligaments (Fig. 2).8 Radioscaphocapitate ligament: The radioscaphocapitate ligament originates proximally from the radial styloid process to the volar edge of the distal radius at the level of the scaphoid fossa (Fig. 2). It passes distally to the radial side at the waist of the scaphoid and proximal to the distal pole of the scaphoid. Long radiolunate ligament: The long radiolunate ligament originates from the volar edge of the scaphoid fossa of the distal radius (Fig. 2). The proximal attachment of the long radiolunate ligament is overlapped partially by the radioscaphocapitate ligament. The long radiolunate ligament is attached distally to the radial and distal edge of the lunate, and volarly and slightly ulnarly to the attachment of the volar segment of the scapholunate interosseous ligament without attaching to the scaphoid. The long radiolunate ligament also overlaps the volar portion of the scapholunate interosseous ligament completely. This ligament may provide constraint against ulnar or distal trans-
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location of the lunate. Located between the long radiolunate ligament and radioscaphocapitate ligaments, at the level of the midcarpal joint, is an area of capsular weakness known as the space of Poirier.8 Short radiolunate ligament: The short radiolunate ligament originates proximally from the ulnar and volar edge of the lunate fossa of the distal radius (Fig. 2). This ligament is attached distally to the volar edge of the lunate. It is located proximal to the ulnolunate ligament and the volar fibrous and proximal membranous parts of the lunotriquetral interosseous ligament. Radioscapholunate ligament: The radioscapholunate ligament is found in the region between the long radiolunate and short radiolunate ligaments and is attached on the volar edge of the distal radius proximally (Fig. 2). This attachment is situated at the interfossal ridge between the scaphoid fossa and lunate fossa. The radioscapholunate ligament branches to the scaphoid and lunate segments and attaches between the volar and proximal portions of the scapholunate interosseous ligament at both the scaphoid and the lunate. While the radioscapholunate ligament is listed as a ligament, it is
FIGURE 3: An open-book volar of a left third metacarpal–fourth metacarpal and capitate-hamate joint. This model is the equivalent of opening the third metacarpal–fourth metacarpal joint and the capitate-hamate joint from the volar side and is developed by computer manipulation of the individual digitalized bone models. 1, third-fourth metacarpal– capitate-hamate intra-articular ligament; 2, third metacarpal ulnar base–fourth metacarpal radial base interosseous ligament; 3, capitate-hamate base interosseous ligament. *, the portion of the third-fourth metacarpal– capitate-hamate intra-articular ligament connected to the hamate. #, the portion of the third-fourth metacarpal– capitate-hamate intra-articular ligament connected to the capitate.
not considered a true ligament and it is not a substantial mechanical structure. Ulnolunate ligament: The ulnolunate ligament originates from the proximal radioulnar ligament (Fig. 2). It attaches on the ulnar side of the lunate, and distal to the attachment of the short radiolunate ligament on the volar edge of the lunate. Nagao et al. stated that the ulnolunate ligament originates radial to the attachment of the ulnocapitate ligament and ulnotriquetral ligament at the base of the ulnar styloid process and runs parallel to the ulnolunate and the ulnotriquetral ligaments.4 They also reported that the attachment of the long radiolunate, short radiolunate, radioscapholunate, ulnolunate, and lunotriquetral ligaments on the lunate occupy approximately 49% of all ligament attachments on the lunate. Ulnocapitate ligament: The ulnocapitate ligament originates from the fovea of the ulnar head and proximal
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FIGURE 2: A volar view of a 3-dimensional model of the right lunate and adjacent carpal bones with the areas of ligament attachments identified by the different colors. The semitransparent areas show the paths of the ligaments. LRL, long radiolunate ligament; SRL, short radiolunate ligament; RSL, radioscapholunate ligament; LT, lunotriquetral ligament; vSLIO, volar portion of the scapholunate interosseous ligament; pLTIO, proximal portion of the lunotriquetral interosseous ligament; vLTIO, volar portion of the lunotriquetral interosseous ligament; RSC, radioscaphocapitate ligament; UL, ulnolunate ligament). Reprinted from Nagao S, Patterson RM, Buford WL Jr., Anderson CR, Shah MA, Viegas SF, Three-dimensional description of ligamentous attachments around the lunate, J Hand Surg 2005;30A:685– 692, Figure 2. Copyright © 2005, with permission from The American Society for Surgery of the Hand.
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FIGURE 4: A distal view from the carpometacarpal joint of a 3dimensional model of the distal carpal row of a left wrist. The solid, colored areas show ligament attachments, and the semitransparent colored areas show the paths of the ligaments. 1, trapeziotrapezoid interosseous ligament; 2, capitotrapezoid interosseous ligament; 3, capitohamate interosseous ligament; 4, volar trapeziotrapezoid ligament; 5, capitotrapezium ligament; 6, volar capitotrapezoid ligament; 7, volar capitohamate ligament; 8, dorsal trapeziotrapezoid ligament; 9, dorsal capitotrapezoid ligament; 10, dorsal capitohamate distal ligament. *, the portion of ligament connected to the hamate. #, the portion of ligament connected to the capitate.
FIGURE 5: A dorsal view of a 3-dimensional model of a right wrist joint. Colored areas indicated attachment, and semitransparent colored areas show the paths of the ligament(s). DRC, dorsal radiocarpal ligament; DIC, dorsal intercarpal ligament; dSLIO, dorsal portion of the scapholunate interosseous ligament; pSLIO, proximal portion of the scapholunate interosseous ligament. Reprinted from Nagao S, Patterson RM, Buford WL Jr., Anderson CR, Shah MA, Viegas SF. Three-dimensional description of ligamentous attachments around the lunate, J Hand Surg 2005;30A:685– 692, Figure 9. Copyright © 2005, with permission from The American Society for Surgery of the Hand.
radioulnar ligament at its attachment to the ulnar styloid process. This ligament partially covers both the ulnotriquetral and the ulnolunate ligaments and attaches distally to the proximal and volar side of the capitate.
Dorsal ligaments Dorsal intercarpal ligament: The dorsal intercarpal ligament attaches proximally on the distal and radial aspect of the dorsal tubercle of the triquetrum (Fig. 5). Nagao et al.4 stated that this ligament overlaps the dorsal portion of the distal part of the dorsal portion of the scapholunate interosseous ligament. They also reported that the attachments of both the dorsal radiocarpal ligament and the dorsal intercarpal ligament on the lunate occupy approximately 15% of all ligament attachments on the lunate. More recently, Short et al. reported that the thickest portion of the dorsal intercarpal ligament inserts on the dorsal groove of the scaphoid, and a thinner arm of the ligament inserts onto the dorsal trapezium and proximal trapezoid.9 Viegas et al. described the lateral V configuration formed by the dorsal intercarpal and dorsal radiocarpal ligaments, which confers important indirect dorsal stability to the scapholunate complex during wrist motion.10 The dorsal intercarpal and dorsal radiocarpal ligaments are important in maintaining carpal stability and alignment and play an important role in preventing the development of dorsal intercalated segment instability (DISI) and volar intercalated segment instability deformities. Dorsal trapeziotrapezoid ligament: The dorsal trapeziotrapezoid ligament attaches to the ulnar edge of
Intra-articular ligament The third-fourth metacarpal– capitate-hamate intraarticular ligament: The third-fourth metacarpal– capitate-hamate intra-articular ligament is between, and connected to, the third metacarpal, the fourth metacarpal, the capitate, and the hamate (Figs. 3, 4). The main part of this ligament passes from the center of the ulnar side of the third metacarpal base into the center of the radial side of the hamate. The branch from the center of the radial side of the fourth metacarpal base joins the main part of this ligament at the third carpometacarpal joint. The branch from the center of the ulnar side of the capitate joins the main part of this ligament at the fourth carpometacarpal joint. Intrinsic ligaments The 2 most important intrinsic and interosseous ligaments—the scapholunate interosseous and lunotriquetral ligaments—are divided into dorsal, proximal, and palmar parts. The thickest and strongest part of the lunotriquetral ligament is located palmarly.8
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the trapezium. It passes ulnarly to the radial edge of the trapezoid. Dorsal capitotrapezoid ligament: The dorsal capitotrapezoid ligament attaches to the ulnar edge of the trapezoid (Figs. 4, 6). It passes ulnarly to the distal and radial edge of the capitate. Dorsal capitohamate ligaments: The dorsal capitohamate ligament is composed of the distal capitohamate ligament and the proximal capitohamate ligament. The distal capitohamate ligament originates from the distal side of the ulnar edge of the capitate and attaches to the distal side of the radial edge of the hamate (Figs. 4, 6). The proximal capitohamate ligament originates from the proximal side of the ulnar edge of the capitate and attaches to the proximal side of the radial edge of the hamate. Dorsal triquetrohamate ligament: The dorsal triquetrohamate ligament originates proximally from the distal and radial edge of the triquetrum. This ligament attaches distally to the proximal and volar edge of the hamate. Volar ligaments Lunotriquetral ligament: Nagao et al. recently described the lunotriquetral ligament as an independent structure, which was identified separately from the
FIGURE 7: A volar view of a 3-dimensional model of a left wrist. The solid, colored areas show ligament attachments, and the semitransparent colored areas show the paths of the ligaments. 1, volar trapeziotrapezoid ligament; 2, scaphotrapezial radial branch ligament; 3, scaphotrapezial ulnar branch ligament; 4, scaphotrapezoidal ligament; 5, scaphocapitate ligament; 6, capitotrapezium ligament; 9, trapeziotrapezoidal interosseous ligament; APL, abductor pollicis longus.
lunotriquetral interosseous ligament.4 This ligament originates from the distal and ulnar side of the lunate and attaches distal to the attachment of the ulnolunate ligament and radial of the volar lunotriquetral interosseous ligament. The lunotriquetral ligament partially overlaps the volar lunotriquetral interosseous ligament. Nagao et al. also stated the lunotriquetral ligament should be a part of the radiotriquetral ligament described by Mayfield et al.11 Volar trapeziotrapezoid ligament: The volar trapeziotrapezoid ligament attaches to the ulnar edge of the trapezium. It passes ulnarly to the radial edge of the trapezoid (Figs. 4, 7). Scaphotrapezial ligament: The scaphotrapezial ligament consists of 2 branches that originate from the radial and volar aspect of the scaphoid tuberosity. The radial branch and ulnar branch of this ligament extend and diverge distally, forming a V shape, and attach to the radial and proximal side of the trapezium, respectively (Figs. 7, 8). Scaphotrapezoidal ligament: The scaphotrapezoidal ligament supports the scaphotrapezio-trapezoidal joint along with the scaphotrapezial ligaments (Fig. 6). This ligament originates from the distal and volar
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FIGURE 6: A dorsal view of a 3-dimensional model of a left wrist. The solid, colored areas show ligament attachments, and the semitransparent colored areas show the paths of the ligaments. 1, dorsal trapeziotrapezoid ligament; 2, dorsal capitotrapezoid ligament; 3, dorsal capitohamate distal ligament; 4, dorsal capitohamate proximal ligament; 5, capitotrapezoid interosseous ligament.
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FIGURE 8: A volar view of a 3-dimensional model of a left wrist. The solid, colored areas show ligament attachments, and the semitransparent colored areas show the paths of the ligaments. 7, volar capitotrapezoid ligament; 8, volar capitohamate ligament; 10, capitohamate interosseous ligament; APL, abductor pollicis longus.
Current Concepts
aspect of the scaphoid tuberosity and attaches distally to the proximal edge of the trapezoid. Scaphocapitate ligament: The scaphocapitate ligament attaches radially to the ulnar and volar side of the distal pole of the scaphoid and ulnarly to the radial and volar side of the capitate (Figs. 4, 7, 8). A line connecting the origin of the scaphotrapezial ligament and the scaphocapitate ligament is almost perpendicular to the interfacet ridge of the distal scaphoid.12 Volar capitotrapezoid ligament: The volar capitotrapezoid ligament originates from the ulnar and volar side of the trapezium. This ligament attaches to the radial and volar side of the capitate without any attachment to the trapezoid (Figs. 4, 7, 8). Volar capitohamate ligament: The volar capitohamate ligament attaches to the ulnar edge of the capitate and passes ulnar to the radial edge of the lunate (Figs. 4, 7, 8). Triquetrocapitate ligament: The triquetrocapitate ligament attaches proximal to the volar and radial edge of the triquetrum and distal to the ulnar and volar side of the capitate. Volar triquetrohamate ligament: The volar triquetrohamate ligament attaches proximal to the distal and radial edge of the triquetrum and distal to the proximal and dorsal edge of the hamate. Nakamura et
al.13 described the anatomic relation of the triquetrocapitate and the volar triquetrohamate ligaments as dependent on the type of lunate, whereby in type I there is no medial hamate facet and in type II there is a medial hamate facet. The relation between the triquetrocapitate and the triquetrohamate ligaments was classified into 3 types. In type A, the triquetrocapitate ligament is completely separate from the triquetrohamate ligament; in type B, the triquetrocapitate ligament overlaps the triquetrohamate ligament; and in type C, the triquetrocapitate ligament has an additional ligament from the triquetrum to the proximal pole of the hamate. Eighty-two percent of type I lunates were associated with a type A relation between the triquetrocapitate and the triquetrohamate ligaments, and 96% of type II lunates were associated with a type C relation between the triquetrocapitate and the triquetrohamate ligaments. Interosseous ligaments Scapholunate interosseous ligament: The scapholunate interosseous ligament joins the scaphoid and lunate along the proximal edge of the joint surface and is described as a 3-part structure with a volar portion, a proximal portion, and a dorsal portion (Fig. 5). The proximal scapholunate interosseous ligament is a considerably thinner ligament that makes important contributions to the rotational stability of the scapholunate joint. It appears histologically as a fibrocartilaginous structure and, in isolation, contributes little to no restraint to abnormal motion of the scapholunate joint.1 The dorsal scapholunate interosseous ligament is now regarded as the thickest, strongest, and most critical of the scapholunate stabilizers.14 It is a true ligament, with transversely oriented collagen fibers, and is a primary restraint not only to distraction but also to torsional and translational moments as well.1 The scapholunate interosseous ligament is the primary stabilizer and the radioscaphocapitate and scaphotrapezial ligaments are secondary stabilizers of the scapholunate articulation.15 Lunotriquetral interosseous ligament: The lunotriquetral interosseous ligament joints the lunate and triquetrum along the proximal edge of the joint surface (Fig. 2). The lunotriquetral interosseous ligament is also described as a 3-part structure with a volar portion, a proximal portion, and a dorsal portion. Trapeziotrapezoid interosseous ligament: The trapeziotrapezoid interosseous ligament is located entirely within the trapeziotrapezoid joint (Figs, 4, 7). It attaches to the volar side of the ulnar edge of the
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trapezium and passes ulnar to the distal side of the radial edge of the trapezoid. Capitotrapezoid interosseous ligament: The capitotrapezoid interosseous ligament is located entirely within the capitotrapezoid joint (Figs. 4, 6). It passes from the center of the ulnar side of the trapezoid into the distal, radial side of the capitate. Capitohamate interosseous ligament: The capitohamate interosseous ligament is located entirely within the capitohamate joint (Figs. 3, 4, 8). It passes from the center of the ulnar side of the capitate into the distal radial side of the hamate. Others Ligaments around the first and second through fifth carpometacarpal joints: Nanno et al. identified 7 ligaments of the first carpometacarpal joint: the dorsoradial ligament, the posterior oblique ligament, the superficial anterior oblique ligament, the deep anterior oblique ligament, the ulnar collateral ligament, the dorsal first metacarpal ulnar base–second metacarpal radial base intermetacarpal ligament, and the volar first metacarpal ulnar base– second metacarpal radial base intermetacarpal ligament. They described the detailed locations and areas of the ligamentous attachments of the first carpometacarpal joint. The average locations of the centroid of the ligamentous attachments of the ulnar collateral and the dorsoradial ligaments were located ulnovolar and dorsoradial on the first metacarpal base, respectively.5 Furthermore, they described 9 dorsal and 11 palmar carpometacarpal ligaments and 1 carpometacarpal interosseous ligament in the second through fifth carpometacarpal joints. They also described an intra-articular ligament between the third metacarpal, the fourth metacarpal, the capitate, and the hamate. Five dorsal and 5 palmar intermetacarpal ligaments and 3 intermetacarpal interosseous ligaments were also identified in the second through fifth intermetacarpal joints.6 BIOMECHANICS Understanding the kinetics and kinematics of the wrist is important to diagnose and treat traumatic and/or degenerative changes of the wrist joint. Many researchers9,16,17 have evaluated the load transfer characteristics in the wrist with various types of carpal instability after ligament injuries. Consistently in these load studies, it was found that the location within the wrist where increased pressure developed correlated well with areas in which degenerative changes developed in patients with the same type of carpal instability or fractures. Previously, little attention was paid to the dorsal ligament5 of the wrist in considering the kinetics or
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kinematics of the wrist. Furthermore, the dorsal ligaments of the wrist were generally neither preserved nor repaired during or after a dorsal approach to the wrist joint. Recently, studies have suggested that the dorsal intercarpal ligament and dorsal radiocarpal ligaments play an important role in stabilization of the proximal carpal row. Viegas et al. described the “lateral V configuration” of the dorsal intercarpal and dorsal radiocarpal ligaments.10 They stated that the dorsal intercarpal and dorsal radiocarpal ligaments together act effectively as a dorsal radioscaphoid ligament that has the ability to vary its effective length 3-fold by changing the angle between the 2 arms of the V. They concluded that the dorsal radiocarpal– dorsal intercarpal ligaments’ lateral V configuration allows normal carpal kinematics while maintaining its indirect dorsal stabilizing effect on the scaphoid throughout the range of motion of the wrist. Viegas et al.18 also demonstrated that not only are the dorsal radiocarpal and dorsal intercarpal ligaments important in preventing a DISI, but also disruption of the dorsal radiocarpal ligament alone will result in a volar intercalated segment instability deformity. In the clinical setting, Slutsky reported that dorsal radiocarpal ligament tears are poorly seen through an open approach. Although 7 patients who had a dorsal capsulodesis for scapholunate instability were found to have a dorsal radiocarpal ligament tear during wrist arthroscopy through the standard dorsal portals, none of these tears could be identified through a dorsal capsulotomy. Slutsky recommends the 1–2 or 6U portals to identify the dorsal radiocarpal ligament tear.19 Mitsuyasu et al.20 in 2004 described the anatomic difference in a cadaver model between dynamic scapholunate instability and static scapholunate instability with a DISI deformity. They studied the role of the dorsal intercarpal ligament in the development of scapholunate instability and resulting DISI. Six stages of increasing instability were developed by progressively sectioning the following structures: stage 1, partial dorsal capsulectomy retaining both the dorsal intercarpal and dorsal radiocarpal ligaments; stage 2, sectioning of the palmar and proximal (membranous) portion of the scapholunate interosseous ligament; stage 3, detaching the dorsal intercarpal ligament from its insertion on the scaphoid and trapezium; stage 4, sectioning the dorsal portion of the scapholunate interosseous ligament; stage 5, detaching the dorsal intercarpal ligament from its attachment on the lunate; and stage 6, complete sectioning of the lunotriquetral interosseous ligament. The scaphoid position and the scapholunate gap changed significantly (p ⬍ .05) after Mitsuyasu et al.20
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sectioned all 3 components—volar, proximal (membranous), and dorsal— of the scapholunate interosseous (stage 4) and dorsal intercarpal ligaments from the scaphoid only when the wrist was loaded. However, the lunate position was unchanged in both the unloaded and loaded conditions. After the dorsal intercarpal ligament was detached from the lunate (stage 5), both the scaphoid and lunate moved, and the scapholunate gap increased significantly (p ⬍ .05) in both the unloaded and loaded conditions and caused a DISI deformity. Therefore, stage 4 resulted in scapholunate dissociation with a dynamic DISI deformity, and stage 5 resulted in a scapholunate dissociation with a static DISI deformity. Complete disruption of the scapholunate ligament did not result in the development of a static collapse of the lunate. This suggests that the dorsal intercarpal ligament has an important role in stabilizing the scaphoid and lunate and preventing DISI deformity. They demonstrated that the dorsal intercarpal ligament is important in maintaining the carpal alignment of both the scaphoid and lunate and demonstrated anatomic differences between dynamic and static DISI deformity as follows. When the dorsal intercarpal and the scapholunate interosseous ligaments were disrupted from the scaphoid and the wrist was loaded, a widened scapholunate gap developed. This was comparable with a clinical dynamic scapholunate instability and DISI deformity. When the dorsal intercarpal ligament was also disrupted from the lunate, the resulting instability showed a flexed posture of the scaphoid and a widened scapholunate gap in both the loaded and unloaded conditions. Furthermore, when the dorsal intercarpal ligament was detached from the lunate, the lunate changed position to an extended posture in both the loaded and unloaded conditions. This was comparable with a clinical static scapholunate instability and DISI deformity. Recent studies have focused attention on “coupled motion” of the wrist, such as the so-called dartthrowing motion. The scaphoid has 3 joints to the distal row, which consists of the scaphotrapezium, scaphotrapezoid, and scaphocapitate joints. Morimoto et al. investigated the scaphoid-trapezium-trapezoid motion using a 3-dimensional dynamic motion analysis system.21 The animations of the trapezium-trapezoid motion relative to the scaphoid revealed that the scaphoidtrapezoid motion was a rotational motion obliquely oriented relative to the sagittal plane of the wrist and described in an ulnoflexion/radial extension motion plane in both flexion/extension motion and radial/ ulnar deviation of the wrist. Furthermore, Morimoto et al.22 and Kaufmann et al.23 reported that radioulnar deviation of the wrist occurs mostly through the midcarpal
joint, with a lesser contribution from the radiocarpal joint. Morimoto et al.22 stated that this motion, the dart-throwing motion, is the most frequently used wrist motion in daily living activities. They demonstrated the dart-throwing motion biomechanics as radiodorsal/ ulnopalmar motion of the midcarpal joint. Between the lunate and capitate, there are no vertical ligaments or soft tissue other than the capsule. Therefore, this joint is highly mobile and unrestricted; it participates only passively in the dart-throwing motion. Additionally, they reported that because there are no ligaments connecting the anterolateral and dorsomedial corners of the triquetrum-hamate joint that could act as collateral ligaments stabilizing the midcarpal joint, this medial function is exclusively reserved to the extensor carpi ulnaris tendon, whose dynamic action is the key to avoid other rotations of the capitate out of the dart-throwing motion plane. The dart-throwing motion concerns only the scaphocapitate and the scaphoid-trapezium-trapezoid ligament. Kaufmann et al. showed that 86% of radial deviation and 66% of ulnar deviation occurs at the midcarpal joint. In radial deviation, the distal carpal row extends and supinates, whereas it flexes and pronates in ulnar deviation.23 In 2007, Patterson et al.24 reported on the carpal kinematics during simulated active and passive motion of the wrist in a cadaver study using an optical motion analysis system. They described that there were no significant differences (p ⬍ .05) in carpal motion (flexion– extension motion or radial– ulnar deviation) when the wrist was moved in simulated active motion through the extensor and flexor tendons or in passive motion, with a constant force applied to the tendons. They concluded that carpal bone kinematics in a healthy normal joint is similar in both simulated active and passive wrist motion. REFERENCES 1. Kuo CE, Wolfe SW. Scapholunate instability: current concepts in diagnosis and management. J Hand Surg 2008;33A:998 –1013. 2. Kawamura K, Chung KC. Management of wrist injuries. Plast Reconstr Surg 2007;120:73e– 89e. 3. Taleisnik J. The ligaments of the wrist. J Hand Surg 1976;1:110 –118. 4. Nagao S, Patterson RM, Buford WL Jr, Anderson CR, Shah MA, Viegas SF. Three-dimensional description of ligamentous attachments around the lunate. J Hand Surg 2005;30A:685– 692. 5. Nanno M, Buford WL Jr, Patterson RM, Andersen CR, Viegas SF. Three-dimensional analysis of the ligamentous attachments of the first carpometacarpal joint. J Hand Surg 2006;31A:1160 –1170. 6. Nanno M, Buford WL Jr, Patterson RM, Andersen CR, Viegas SF. Three-dimensional analysis of the ligamentous attachments of the second through fifth carpometacarpal joints. Clin Anat 2007;20:530 –544. 7. Katz DA, Green JK, Werner FW, Loftus JB. Capsuloligamentous restraints to dorsal and palmar carpal translation. J Hand Surg 2003;28A:610 – 613.
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18.
19. 20.
21.
22.
23.
24.
Dobyns JH, eds. The wrist: diagnosis and operative treatment. 1st ed. St. Louis: Mosby, 1998:73–105. Viegas SF, Patterson RM, Peterson PD, Pogue DJ, Jenkins DK, Sweo TD, et al. Ulnar-sided perilunate instability: an anatomic and biomechanic study. J Hand Surg 1990;15A:268 –278. Slutsky DJ. Arthroscopic dorsal radiocarpal ligament repair. Arthroscopy 2005;21:1486.e1–1486.e8. Mitsuyasu H, Patterson RM, Shah MA, Buford WL, Iwamoto Y, Viegas SF. The role of the dorsal intercarpal ligament in dynamic and static scapholunate instability. J Hand Surg 2004;29A:279 – 288. Morimoto H, Viegas SF, Elder K, Nakamura K, Dasilva MF, Patterson RM. The scaphotrapezio-trapezoidal joint. Part 2. A kinematic study. J Hand Surg 2000;25A:911–920. Morimoto H, Murase T, Goto A, Oka K, Sugamoto K, Yoshikawa H. Capitate-based kinematics of the midcarpal joint during wrist radioulnar deviation: an in vivo three-dimensional motion analysis. J Hand Surg 2004;29A:668 – 675. Kaufmann R, Pfaeffle J, Blankenhorn B, Stabile K, Robertson D, Goitz R. Kinematics of the midcarpal and radiocarpal joints in radioulnar deviation: an in vitro study. J Hand Surg 2005;30A:937– 942. Patterson RM, Williams L, Andersen CR, Koh S, Viegas SF. Carpal kinematics during simulated active and passive motion of the wrist. J Hand Surg 2007;32A:1013–1019.
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8. Trail AI, Stanley JK, Hayton MJ. Twenty questions on carpal instability. J Hand Surg 2007;32E:240 –255. 9. Short WH, Werner FW, Green JK, Sutton LG, Brutus JP. Biomechanical evaluation of the ligamentous stabilizers of the scaphoid and lunate: part III. J Hand Surg 2007;32A:297–309. 10. Viegas SF, Yamagichi S, Boyd NI, Patterson RM. The dorsal ligaments of the wrist: anatomy, mechanical properties, and function. J Hand Surg 1999;24A:456 – 468. 11. Mayfield JK, Johnson RP, Kilcoyne RF. The ligaments of the wrist and their functional significance. Anat Rec 1976;186:417– 428. 12. Morimoto H, Viegas SF, Nakamura K, DaSilva MF, Patterson RM. The scaphotrapezio-trapezoidal joint. Part 1: an anatomic and radiographic study. J Hand Surg 2000;25A:899 –910. 13. Nakamura K, Patterson RM, Moritomo H, Viegas SF. Type I versus type II lunates: ligament anatomy and presence of arthrosis. J Hand Surg 2001;26A:428 – 436. 14. Berger RA, Imeada T, Berglund L, An KN. Constraint and material properties of the subregions of the scapholunate interosseous ligament. J Hand Surg 1999;24A:953–962. 15. Short WH, Werner FW, Green JK, Masaoka S. Biomechanical evaluation of the ligamentous stabilizers of the scaphoid and lunate: part II. J Hand Surg 2005;30A:24 –34. 16. Viegas SF, Tencer AF, Cantrell J, Chang M, Clegg P, Hicks C, et al. Load transfer characteristics of the wrist. Part I. The normal joint. J Hand Surg 1987;12A:971–978. 17. Burger RA. Ligament anatomy. In: Cooney WP, Linscheid RI,
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Wrist Anatomy and Biomechanics Yasumu Kijima, MD, Steven F. Viegas, MD, PhD
O TREAT WRIST injuries or degenerative changes, it is essential to understand the anatomy, biomechanics, and function of the wrist, including the carpal ligaments. Successful diagnosis of injures, interpretation of images, and treatment depend on accurate information about the anatomic location of the normal ligamentous attachment. Although a number of articles have been published related to the anatomy and function of the carpal ligaments, recent detailed information has further elucidated the ligamentous anatomy of the wrist. This article provides a current description of the anatomy of the carpal ligaments and of the biomechanics of the wrist. Knowledge of the ligaments will further serve as a foundation for understanding the anatomy and biomechanics of the wrist and the function of individual ligaments and their roles in joint stability as well as the pathomechanics of carpal instabilities.
T
From the Department of Orthopaedic Surgery, Graduate School of Biomedical Sciences, Hiroshima University, Japan; and the Department of Orthopaedic Surgery and Rehabilitation, The University of Texas Medical Branch, Galveston, TX. Received for publication February 5, 2009; accepted in revised form July 28, 2009. The authors would like to acknowledge Mitsuhiko Nanno, MD, and Soya Nagao, MD, for their editorial assistance and contribution to this article. This article is based on Nanno M, Patterson RM, Viegas SF. Carpal ligament anatomy and biomechanics. In: Trumble T, ed. Wrist and elbow reconstruction & arthroscopy: a master skills publication. Rosemont, IL: American Society for Surgery of the Hand, 2006:3–18. No benefits in any form have been received or will be received related directly or indirectly to the subject of this article. Corresponding author: Steven F. Viegas, MD, PhD, 1521 Driftwood Lane, Galveston, TX 77551; e-mail: [email protected]. 0363-5023/09/34A08-0030$36.00/0 doi:10.1016/j.jhsa.2009.07.019
THE ANATOMY OF THE CARPAL LIGAMENTS The wrist consists of the distal ends of the radius and ulna, 8 carpal bones, and the proximal bases of the 5 metacarpal bones. The carpal bones are categorized as a proximal row and a distal row on the basis of their kinematic behavior during global wrist motion.1 The proximal carpal row consists of the scaphoid, lunate, triquetrum, and pisiform, and the distal row consists of the trapezium, trapezoid, capitate, and hamate.2 The proximal carpal row bones can be described as an intercalated segment because no tendons insert upon them, and their motion is entirely dependent on mechanical forces from their surrounding articulations.1 The distal row carpal bones are tightly bound to one another via stout intercarpal ligaments, and motion between them can be considered negligible. Similarly, the nearly rigid ligamentous connection of the trapezium and capitate to the index and middle metacarpal bones and lack of motion between these bones allows us to consider the distal row functionally as part of a fixed hand unit that moves in response to the musculotendinous forces of the forearm.1 The carpal ligaments described here have been divided by Taleisnik3 into extrinsic and intrinsic groups on the basis of their location. Extrinsic ligaments connect the distal radius and ulna to the carpal bones, and intrinsic ligaments have their origins and insertions within the carpal bones.2 Nagao et al.4 and Nanno et al.5,6 made computed tomography images of wrists, from which 3-dimensional images of the bones were modeled, and the ligament attachment areas thereupon are listed in Table 1. The presence or absence of each ligament is also noted. The attachment sites and area of the ligaments are identified by specific colors in figures in this article, and the ligament paths are displayed by semitransparent colors.
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Anatomic and biomechanical research of the wrist has yielded a substantial amount of information that improves our basic knowledge of carpal morphology and function of the wrist and provides information to better assess and improve treatment(s) for various problems of the wrist joint. A precise knowledge of the anatomy and biomechanics of the wrist is useful not only for diagnosis of traumatic ligamentous injuries or degenerative change of the wrist joint but also for treatment for wrist dysfunction. (J Hand Surg 2009;34A:1555–1563. © 2009 Published by Elsevier Inc. on behalf of the American Society for Surgery of the Hand.) Key words Anatomy, biomechanics, ligament, wrist joint.
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TABLE 1. Individual Ligament Attachments of the Volar, Dorsal, and Interosseous Ligaments on the Lunate Volar Ligaments Location LRL SRL RSL
UL LT
DRC
DIC
SLIO
LTIO
Radius Lunate Radius Lunate Radius Scaphoid Lunate Lunate Lunate Triquetrum Radius Lunate Triquetrum Triquetrum Lunate Scaphoid Proximal Waist Trapezoid Trapezium
Area (mm2)
Specimens (n ⫽ 8)
⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾
2.9 2.5 3.8 5.6 1.7 1.9 3.2 2.7 2.2 0.8
8 8 8 8 8 8 8 4 7 7
Dorsal Ligaments 14.3 ⫾ 4.0 1.9 ⫾ 0.6 8.5 ⫾ 5.4 9.8 ⫾ 6.4 3.8 ⫾ 1.3
8 4 8 8 6
5.7 ⫾ 2.3 5.2 ⫾ 3.2 4.0 ⫾ 2.3 2.4
8 6 8 1
10.9 7.6 12.8 13.7 5.0 3.2 5.5 2.7 3.8 2.8
Interosseous Ligaments Volar Scaphoid 4.7 ⫾ 1.7 Lunate 4.9 ⫾ 1.8 Proximal Scaphoid 13.7 ⫾ 7.0 Lunate 16.3 ⫾ 5.6 Dorsal Scaphoid 4.9 ⫾ 0.8 Lunate 4.9 ⫾ 2.4 Volar Lunate 5.8 ⫾ 2.1 Triquetrum 5.2 ⫾ 2.2 Proximal Lunate 14.4 ⫾ 4.6 Triquetrum 11.7 ⫾ 3.7 Dorsal Lunate 3.9 ⫾ 2.8 Triquetrum 2.2 ⫾ 0.9
8 8 8 8 8 8 8 8 8 8 8 8
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LRL, long radiolunate ligament; SRL, short radiolunate ligament; RSL, radioscaphoid ligament; UL, ulnolunate ligament; LT, lunotriquetral ligament; DRC, dorsal radiocarpal ligament; DIC, dorsal intercarpal ligament; SLIO, scapholunate interosseous ligament; LTIO, lunotriquetral interosseous ligament. Source: Reprinted from The Journal of Hand Surgery, Volume 30, Nagao S, Patterson RM, Buford WL, Anderson CR, Shah MA, Viegas SF, Three-dimensional description of ligamentous attachments around the lunate, p. 687, Table 2. Copyright © 2005, with permission from The American Society for Surgery of the Hand.
Extrinsic ligaments Dorsal ligaments: The dorsal ligaments are important secondary stabilizers of the scapholunate joint.1
FIGURE 1: A dorsal view of a 3-dimensional model of a right wrist joint. Colored areas show the path of the ligaments. DRC, dorsal radiocarpal ligament; DIC, dorsal intercarpal ligament. Reprinted from Nagao S, Patterson RM, Buford WL Jr., Anderson CR, Shah MA, Viegas SF. Three-dimensional description of ligamentous attachments around the lunate, J Hand Surg 2005;30A:685– 692, Figure 7. Copyright © 2005, with permission from The American Society for Surgery of the Hand.
Dorsal radiocarpal ligament: The dorsal radiocarpal ligament originates proximally from the ulnar and dorsal portion of the distal end of the radius, from Lister’s tubercle to the level of the interfossal ridge between the scaphoid fossa and the lunate fossa (Fig. 1). This ligament attaches distally to the proximal and dorsal tubercle of the triquetrum and the lunate. Volar ligaments: Volar extrinsic ligaments play a major role in stabilizing the wrist.2 It is generally accepted that those on the palmar aspect provide greater restraint to instability.7 There are 3 strong palmar extrinsic radiocarpal ligaments: the radioscaphocapitate, the long radiolunate, and the short radiolunate ligaments (Fig. 2).8 Radioscaphocapitate ligament: The radioscaphocapitate ligament originates proximally from the radial styloid process to the volar edge of the distal radius at the level of the scaphoid fossa (Fig. 2). It passes distally to the radial side at the waist of the scaphoid and proximal to the distal pole of the scaphoid. Long radiolunate ligament: The long radiolunate ligament originates from the volar edge of the scaphoid fossa of the distal radius (Fig. 2). The proximal attachment of the long radiolunate ligament is overlapped partially by the radioscaphocapitate ligament. The long radiolunate ligament is attached distally to the radial and distal edge of the lunate, and volarly and slightly ulnarly to the attachment of the volar segment of the scapholunate interosseous ligament without attaching to the scaphoid. The long radiolunate ligament also overlaps the volar portion of the scapholunate interosseous ligament completely. This ligament may provide constraint against ulnar or distal trans-
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location of the lunate. Located between the long radiolunate ligament and radioscaphocapitate ligaments, at the level of the midcarpal joint, is an area of capsular weakness known as the space of Poirier.8 Short radiolunate ligament: The short radiolunate ligament originates proximally from the ulnar and volar edge of the lunate fossa of the distal radius (Fig. 2). This ligament is attached distally to the volar edge of the lunate. It is located proximal to the ulnolunate ligament and the volar fibrous and proximal membranous parts of the lunotriquetral interosseous ligament. Radioscapholunate ligament: The radioscapholunate ligament is found in the region between the long radiolunate and short radiolunate ligaments and is attached on the volar edge of the distal radius proximally (Fig. 2). This attachment is situated at the interfossal ridge between the scaphoid fossa and lunate fossa. The radioscapholunate ligament branches to the scaphoid and lunate segments and attaches between the volar and proximal portions of the scapholunate interosseous ligament at both the scaphoid and the lunate. While the radioscapholunate ligament is listed as a ligament, it is
FIGURE 3: An open-book volar of a left third metacarpal–fourth metacarpal and capitate-hamate joint. This model is the equivalent of opening the third metacarpal–fourth metacarpal joint and the capitate-hamate joint from the volar side and is developed by computer manipulation of the individual digitalized bone models. 1, third-fourth metacarpal– capitate-hamate intra-articular ligament; 2, third metacarpal ulnar base–fourth metacarpal radial base interosseous ligament; 3, capitate-hamate base interosseous ligament. *, the portion of the third-fourth metacarpal– capitate-hamate intra-articular ligament connected to the hamate. #, the portion of the third-fourth metacarpal– capitate-hamate intra-articular ligament connected to the capitate.
not considered a true ligament and it is not a substantial mechanical structure. Ulnolunate ligament: The ulnolunate ligament originates from the proximal radioulnar ligament (Fig. 2). It attaches on the ulnar side of the lunate, and distal to the attachment of the short radiolunate ligament on the volar edge of the lunate. Nagao et al. stated that the ulnolunate ligament originates radial to the attachment of the ulnocapitate ligament and ulnotriquetral ligament at the base of the ulnar styloid process and runs parallel to the ulnolunate and the ulnotriquetral ligaments.4 They also reported that the attachment of the long radiolunate, short radiolunate, radioscapholunate, ulnolunate, and lunotriquetral ligaments on the lunate occupy approximately 49% of all ligament attachments on the lunate. Ulnocapitate ligament: The ulnocapitate ligament originates from the fovea of the ulnar head and proximal
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FIGURE 2: A volar view of a 3-dimensional model of the right lunate and adjacent carpal bones with the areas of ligament attachments identified by the different colors. The semitransparent areas show the paths of the ligaments. LRL, long radiolunate ligament; SRL, short radiolunate ligament; RSL, radioscapholunate ligament; LT, lunotriquetral ligament; vSLIO, volar portion of the scapholunate interosseous ligament; pLTIO, proximal portion of the lunotriquetral interosseous ligament; vLTIO, volar portion of the lunotriquetral interosseous ligament; RSC, radioscaphocapitate ligament; UL, ulnolunate ligament). Reprinted from Nagao S, Patterson RM, Buford WL Jr., Anderson CR, Shah MA, Viegas SF, Three-dimensional description of ligamentous attachments around the lunate, J Hand Surg 2005;30A:685– 692, Figure 2. Copyright © 2005, with permission from The American Society for Surgery of the Hand.
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FIGURE 4: A distal view from the carpometacarpal joint of a 3dimensional model of the distal carpal row of a left wrist. The solid, colored areas show ligament attachments, and the semitransparent colored areas show the paths of the ligaments. 1, trapeziotrapezoid interosseous ligament; 2, capitotrapezoid interosseous ligament; 3, capitohamate interosseous ligament; 4, volar trapeziotrapezoid ligament; 5, capitotrapezium ligament; 6, volar capitotrapezoid ligament; 7, volar capitohamate ligament; 8, dorsal trapeziotrapezoid ligament; 9, dorsal capitotrapezoid ligament; 10, dorsal capitohamate distal ligament. *, the portion of ligament connected to the hamate. #, the portion of ligament connected to the capitate.
FIGURE 5: A dorsal view of a 3-dimensional model of a right wrist joint. Colored areas indicated attachment, and semitransparent colored areas show the paths of the ligament(s). DRC, dorsal radiocarpal ligament; DIC, dorsal intercarpal ligament; dSLIO, dorsal portion of the scapholunate interosseous ligament; pSLIO, proximal portion of the scapholunate interosseous ligament. Reprinted from Nagao S, Patterson RM, Buford WL Jr., Anderson CR, Shah MA, Viegas SF. Three-dimensional description of ligamentous attachments around the lunate, J Hand Surg 2005;30A:685– 692, Figure 9. Copyright © 2005, with permission from The American Society for Surgery of the Hand.
radioulnar ligament at its attachment to the ulnar styloid process. This ligament partially covers both the ulnotriquetral and the ulnolunate ligaments and attaches distally to the proximal and volar side of the capitate.
Dorsal ligaments Dorsal intercarpal ligament: The dorsal intercarpal ligament attaches proximally on the distal and radial aspect of the dorsal tubercle of the triquetrum (Fig. 5). Nagao et al.4 stated that this ligament overlaps the dorsal portion of the distal part of the dorsal portion of the scapholunate interosseous ligament. They also reported that the attachments of both the dorsal radiocarpal ligament and the dorsal intercarpal ligament on the lunate occupy approximately 15% of all ligament attachments on the lunate. More recently, Short et al. reported that the thickest portion of the dorsal intercarpal ligament inserts on the dorsal groove of the scaphoid, and a thinner arm of the ligament inserts onto the dorsal trapezium and proximal trapezoid.9 Viegas et al. described the lateral V configuration formed by the dorsal intercarpal and dorsal radiocarpal ligaments, which confers important indirect dorsal stability to the scapholunate complex during wrist motion.10 The dorsal intercarpal and dorsal radiocarpal ligaments are important in maintaining carpal stability and alignment and play an important role in preventing the development of dorsal intercalated segment instability (DISI) and volar intercalated segment instability deformities. Dorsal trapeziotrapezoid ligament: The dorsal trapeziotrapezoid ligament attaches to the ulnar edge of
Intra-articular ligament The third-fourth metacarpal– capitate-hamate intraarticular ligament: The third-fourth metacarpal– capitate-hamate intra-articular ligament is between, and connected to, the third metacarpal, the fourth metacarpal, the capitate, and the hamate (Figs. 3, 4). The main part of this ligament passes from the center of the ulnar side of the third metacarpal base into the center of the radial side of the hamate. The branch from the center of the radial side of the fourth metacarpal base joins the main part of this ligament at the third carpometacarpal joint. The branch from the center of the ulnar side of the capitate joins the main part of this ligament at the fourth carpometacarpal joint. Intrinsic ligaments The 2 most important intrinsic and interosseous ligaments—the scapholunate interosseous and lunotriquetral ligaments—are divided into dorsal, proximal, and palmar parts. The thickest and strongest part of the lunotriquetral ligament is located palmarly.8
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the trapezium. It passes ulnarly to the radial edge of the trapezoid. Dorsal capitotrapezoid ligament: The dorsal capitotrapezoid ligament attaches to the ulnar edge of the trapezoid (Figs. 4, 6). It passes ulnarly to the distal and radial edge of the capitate. Dorsal capitohamate ligaments: The dorsal capitohamate ligament is composed of the distal capitohamate ligament and the proximal capitohamate ligament. The distal capitohamate ligament originates from the distal side of the ulnar edge of the capitate and attaches to the distal side of the radial edge of the hamate (Figs. 4, 6). The proximal capitohamate ligament originates from the proximal side of the ulnar edge of the capitate and attaches to the proximal side of the radial edge of the hamate. Dorsal triquetrohamate ligament: The dorsal triquetrohamate ligament originates proximally from the distal and radial edge of the triquetrum. This ligament attaches distally to the proximal and volar edge of the hamate. Volar ligaments Lunotriquetral ligament: Nagao et al. recently described the lunotriquetral ligament as an independent structure, which was identified separately from the
FIGURE 7: A volar view of a 3-dimensional model of a left wrist. The solid, colored areas show ligament attachments, and the semitransparent colored areas show the paths of the ligaments. 1, volar trapeziotrapezoid ligament; 2, scaphotrapezial radial branch ligament; 3, scaphotrapezial ulnar branch ligament; 4, scaphotrapezoidal ligament; 5, scaphocapitate ligament; 6, capitotrapezium ligament; 9, trapeziotrapezoidal interosseous ligament; APL, abductor pollicis longus.
lunotriquetral interosseous ligament.4 This ligament originates from the distal and ulnar side of the lunate and attaches distal to the attachment of the ulnolunate ligament and radial of the volar lunotriquetral interosseous ligament. The lunotriquetral ligament partially overlaps the volar lunotriquetral interosseous ligament. Nagao et al. also stated the lunotriquetral ligament should be a part of the radiotriquetral ligament described by Mayfield et al.11 Volar trapeziotrapezoid ligament: The volar trapeziotrapezoid ligament attaches to the ulnar edge of the trapezium. It passes ulnarly to the radial edge of the trapezoid (Figs. 4, 7). Scaphotrapezial ligament: The scaphotrapezial ligament consists of 2 branches that originate from the radial and volar aspect of the scaphoid tuberosity. The radial branch and ulnar branch of this ligament extend and diverge distally, forming a V shape, and attach to the radial and proximal side of the trapezium, respectively (Figs. 7, 8). Scaphotrapezoidal ligament: The scaphotrapezoidal ligament supports the scaphotrapezio-trapezoidal joint along with the scaphotrapezial ligaments (Fig. 6). This ligament originates from the distal and volar
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FIGURE 6: A dorsal view of a 3-dimensional model of a left wrist. The solid, colored areas show ligament attachments, and the semitransparent colored areas show the paths of the ligaments. 1, dorsal trapeziotrapezoid ligament; 2, dorsal capitotrapezoid ligament; 3, dorsal capitohamate distal ligament; 4, dorsal capitohamate proximal ligament; 5, capitotrapezoid interosseous ligament.
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FIGURE 8: A volar view of a 3-dimensional model of a left wrist. The solid, colored areas show ligament attachments, and the semitransparent colored areas show the paths of the ligaments. 7, volar capitotrapezoid ligament; 8, volar capitohamate ligament; 10, capitohamate interosseous ligament; APL, abductor pollicis longus.
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aspect of the scaphoid tuberosity and attaches distally to the proximal edge of the trapezoid. Scaphocapitate ligament: The scaphocapitate ligament attaches radially to the ulnar and volar side of the distal pole of the scaphoid and ulnarly to the radial and volar side of the capitate (Figs. 4, 7, 8). A line connecting the origin of the scaphotrapezial ligament and the scaphocapitate ligament is almost perpendicular to the interfacet ridge of the distal scaphoid.12 Volar capitotrapezoid ligament: The volar capitotrapezoid ligament originates from the ulnar and volar side of the trapezium. This ligament attaches to the radial and volar side of the capitate without any attachment to the trapezoid (Figs. 4, 7, 8). Volar capitohamate ligament: The volar capitohamate ligament attaches to the ulnar edge of the capitate and passes ulnar to the radial edge of the lunate (Figs. 4, 7, 8). Triquetrocapitate ligament: The triquetrocapitate ligament attaches proximal to the volar and radial edge of the triquetrum and distal to the ulnar and volar side of the capitate. Volar triquetrohamate ligament: The volar triquetrohamate ligament attaches proximal to the distal and radial edge of the triquetrum and distal to the proximal and dorsal edge of the hamate. Nakamura et
al.13 described the anatomic relation of the triquetrocapitate and the volar triquetrohamate ligaments as dependent on the type of lunate, whereby in type I there is no medial hamate facet and in type II there is a medial hamate facet. The relation between the triquetrocapitate and the triquetrohamate ligaments was classified into 3 types. In type A, the triquetrocapitate ligament is completely separate from the triquetrohamate ligament; in type B, the triquetrocapitate ligament overlaps the triquetrohamate ligament; and in type C, the triquetrocapitate ligament has an additional ligament from the triquetrum to the proximal pole of the hamate. Eighty-two percent of type I lunates were associated with a type A relation between the triquetrocapitate and the triquetrohamate ligaments, and 96% of type II lunates were associated with a type C relation between the triquetrocapitate and the triquetrohamate ligaments. Interosseous ligaments Scapholunate interosseous ligament: The scapholunate interosseous ligament joins the scaphoid and lunate along the proximal edge of the joint surface and is described as a 3-part structure with a volar portion, a proximal portion, and a dorsal portion (Fig. 5). The proximal scapholunate interosseous ligament is a considerably thinner ligament that makes important contributions to the rotational stability of the scapholunate joint. It appears histologically as a fibrocartilaginous structure and, in isolation, contributes little to no restraint to abnormal motion of the scapholunate joint.1 The dorsal scapholunate interosseous ligament is now regarded as the thickest, strongest, and most critical of the scapholunate stabilizers.14 It is a true ligament, with transversely oriented collagen fibers, and is a primary restraint not only to distraction but also to torsional and translational moments as well.1 The scapholunate interosseous ligament is the primary stabilizer and the radioscaphocapitate and scaphotrapezial ligaments are secondary stabilizers of the scapholunate articulation.15 Lunotriquetral interosseous ligament: The lunotriquetral interosseous ligament joints the lunate and triquetrum along the proximal edge of the joint surface (Fig. 2). The lunotriquetral interosseous ligament is also described as a 3-part structure with a volar portion, a proximal portion, and a dorsal portion. Trapeziotrapezoid interosseous ligament: The trapeziotrapezoid interosseous ligament is located entirely within the trapeziotrapezoid joint (Figs, 4, 7). It attaches to the volar side of the ulnar edge of the
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trapezium and passes ulnar to the distal side of the radial edge of the trapezoid. Capitotrapezoid interosseous ligament: The capitotrapezoid interosseous ligament is located entirely within the capitotrapezoid joint (Figs. 4, 6). It passes from the center of the ulnar side of the trapezoid into the distal, radial side of the capitate. Capitohamate interosseous ligament: The capitohamate interosseous ligament is located entirely within the capitohamate joint (Figs. 3, 4, 8). It passes from the center of the ulnar side of the capitate into the distal radial side of the hamate. Others Ligaments around the first and second through fifth carpometacarpal joints: Nanno et al. identified 7 ligaments of the first carpometacarpal joint: the dorsoradial ligament, the posterior oblique ligament, the superficial anterior oblique ligament, the deep anterior oblique ligament, the ulnar collateral ligament, the dorsal first metacarpal ulnar base–second metacarpal radial base intermetacarpal ligament, and the volar first metacarpal ulnar base– second metacarpal radial base intermetacarpal ligament. They described the detailed locations and areas of the ligamentous attachments of the first carpometacarpal joint. The average locations of the centroid of the ligamentous attachments of the ulnar collateral and the dorsoradial ligaments were located ulnovolar and dorsoradial on the first metacarpal base, respectively.5 Furthermore, they described 9 dorsal and 11 palmar carpometacarpal ligaments and 1 carpometacarpal interosseous ligament in the second through fifth carpometacarpal joints. They also described an intra-articular ligament between the third metacarpal, the fourth metacarpal, the capitate, and the hamate. Five dorsal and 5 palmar intermetacarpal ligaments and 3 intermetacarpal interosseous ligaments were also identified in the second through fifth intermetacarpal joints.6 BIOMECHANICS Understanding the kinetics and kinematics of the wrist is important to diagnose and treat traumatic and/or degenerative changes of the wrist joint. Many researchers9,16,17 have evaluated the load transfer characteristics in the wrist with various types of carpal instability after ligament injuries. Consistently in these load studies, it was found that the location within the wrist where increased pressure developed correlated well with areas in which degenerative changes developed in patients with the same type of carpal instability or fractures. Previously, little attention was paid to the dorsal ligament5 of the wrist in considering the kinetics or
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kinematics of the wrist. Furthermore, the dorsal ligaments of the wrist were generally neither preserved nor repaired during or after a dorsal approach to the wrist joint. Recently, studies have suggested that the dorsal intercarpal ligament and dorsal radiocarpal ligaments play an important role in stabilization of the proximal carpal row. Viegas et al. described the “lateral V configuration” of the dorsal intercarpal and dorsal radiocarpal ligaments.10 They stated that the dorsal intercarpal and dorsal radiocarpal ligaments together act effectively as a dorsal radioscaphoid ligament that has the ability to vary its effective length 3-fold by changing the angle between the 2 arms of the V. They concluded that the dorsal radiocarpal– dorsal intercarpal ligaments’ lateral V configuration allows normal carpal kinematics while maintaining its indirect dorsal stabilizing effect on the scaphoid throughout the range of motion of the wrist. Viegas et al.18 also demonstrated that not only are the dorsal radiocarpal and dorsal intercarpal ligaments important in preventing a DISI, but also disruption of the dorsal radiocarpal ligament alone will result in a volar intercalated segment instability deformity. In the clinical setting, Slutsky reported that dorsal radiocarpal ligament tears are poorly seen through an open approach. Although 7 patients who had a dorsal capsulodesis for scapholunate instability were found to have a dorsal radiocarpal ligament tear during wrist arthroscopy through the standard dorsal portals, none of these tears could be identified through a dorsal capsulotomy. Slutsky recommends the 1–2 or 6U portals to identify the dorsal radiocarpal ligament tear.19 Mitsuyasu et al.20 in 2004 described the anatomic difference in a cadaver model between dynamic scapholunate instability and static scapholunate instability with a DISI deformity. They studied the role of the dorsal intercarpal ligament in the development of scapholunate instability and resulting DISI. Six stages of increasing instability were developed by progressively sectioning the following structures: stage 1, partial dorsal capsulectomy retaining both the dorsal intercarpal and dorsal radiocarpal ligaments; stage 2, sectioning of the palmar and proximal (membranous) portion of the scapholunate interosseous ligament; stage 3, detaching the dorsal intercarpal ligament from its insertion on the scaphoid and trapezium; stage 4, sectioning the dorsal portion of the scapholunate interosseous ligament; stage 5, detaching the dorsal intercarpal ligament from its attachment on the lunate; and stage 6, complete sectioning of the lunotriquetral interosseous ligament. The scaphoid position and the scapholunate gap changed significantly (p ⬍ .05) after Mitsuyasu et al.20
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sectioned all 3 components—volar, proximal (membranous), and dorsal— of the scapholunate interosseous (stage 4) and dorsal intercarpal ligaments from the scaphoid only when the wrist was loaded. However, the lunate position was unchanged in both the unloaded and loaded conditions. After the dorsal intercarpal ligament was detached from the lunate (stage 5), both the scaphoid and lunate moved, and the scapholunate gap increased significantly (p ⬍ .05) in both the unloaded and loaded conditions and caused a DISI deformity. Therefore, stage 4 resulted in scapholunate dissociation with a dynamic DISI deformity, and stage 5 resulted in a scapholunate dissociation with a static DISI deformity. Complete disruption of the scapholunate ligament did not result in the development of a static collapse of the lunate. This suggests that the dorsal intercarpal ligament has an important role in stabilizing the scaphoid and lunate and preventing DISI deformity. They demonstrated that the dorsal intercarpal ligament is important in maintaining the carpal alignment of both the scaphoid and lunate and demonstrated anatomic differences between dynamic and static DISI deformity as follows. When the dorsal intercarpal and the scapholunate interosseous ligaments were disrupted from the scaphoid and the wrist was loaded, a widened scapholunate gap developed. This was comparable with a clinical dynamic scapholunate instability and DISI deformity. When the dorsal intercarpal ligament was also disrupted from the lunate, the resulting instability showed a flexed posture of the scaphoid and a widened scapholunate gap in both the loaded and unloaded conditions. Furthermore, when the dorsal intercarpal ligament was detached from the lunate, the lunate changed position to an extended posture in both the loaded and unloaded conditions. This was comparable with a clinical static scapholunate instability and DISI deformity. Recent studies have focused attention on “coupled motion” of the wrist, such as the so-called dartthrowing motion. The scaphoid has 3 joints to the distal row, which consists of the scaphotrapezium, scaphotrapezoid, and scaphocapitate joints. Morimoto et al. investigated the scaphoid-trapezium-trapezoid motion using a 3-dimensional dynamic motion analysis system.21 The animations of the trapezium-trapezoid motion relative to the scaphoid revealed that the scaphoidtrapezoid motion was a rotational motion obliquely oriented relative to the sagittal plane of the wrist and described in an ulnoflexion/radial extension motion plane in both flexion/extension motion and radial/ ulnar deviation of the wrist. Furthermore, Morimoto et al.22 and Kaufmann et al.23 reported that radioulnar deviation of the wrist occurs mostly through the midcarpal
joint, with a lesser contribution from the radiocarpal joint. Morimoto et al.22 stated that this motion, the dart-throwing motion, is the most frequently used wrist motion in daily living activities. They demonstrated the dart-throwing motion biomechanics as radiodorsal/ ulnopalmar motion of the midcarpal joint. Between the lunate and capitate, there are no vertical ligaments or soft tissue other than the capsule. Therefore, this joint is highly mobile and unrestricted; it participates only passively in the dart-throwing motion. Additionally, they reported that because there are no ligaments connecting the anterolateral and dorsomedial corners of the triquetrum-hamate joint that could act as collateral ligaments stabilizing the midcarpal joint, this medial function is exclusively reserved to the extensor carpi ulnaris tendon, whose dynamic action is the key to avoid other rotations of the capitate out of the dart-throwing motion plane. The dart-throwing motion concerns only the scaphocapitate and the scaphoid-trapezium-trapezoid ligament. Kaufmann et al. showed that 86% of radial deviation and 66% of ulnar deviation occurs at the midcarpal joint. In radial deviation, the distal carpal row extends and supinates, whereas it flexes and pronates in ulnar deviation.23 In 2007, Patterson et al.24 reported on the carpal kinematics during simulated active and passive motion of the wrist in a cadaver study using an optical motion analysis system. They described that there were no significant differences (p ⬍ .05) in carpal motion (flexion– extension motion or radial– ulnar deviation) when the wrist was moved in simulated active motion through the extensor and flexor tendons or in passive motion, with a constant force applied to the tendons. They concluded that carpal bone kinematics in a healthy normal joint is similar in both simulated active and passive wrist motion. REFERENCES 1. Kuo CE, Wolfe SW. Scapholunate instability: current concepts in diagnosis and management. J Hand Surg 2008;33A:998 –1013. 2. Kawamura K, Chung KC. Management of wrist injuries. Plast Reconstr Surg 2007;120:73e– 89e. 3. Taleisnik J. The ligaments of the wrist. J Hand Surg 1976;1:110 –118. 4. Nagao S, Patterson RM, Buford WL Jr, Anderson CR, Shah MA, Viegas SF. Three-dimensional description of ligamentous attachments around the lunate. J Hand Surg 2005;30A:685– 692. 5. Nanno M, Buford WL Jr, Patterson RM, Andersen CR, Viegas SF. Three-dimensional analysis of the ligamentous attachments of the first carpometacarpal joint. J Hand Surg 2006;31A:1160 –1170. 6. Nanno M, Buford WL Jr, Patterson RM, Andersen CR, Viegas SF. Three-dimensional analysis of the ligamentous attachments of the second through fifth carpometacarpal joints. Clin Anat 2007;20:530 –544. 7. Katz DA, Green JK, Werner FW, Loftus JB. Capsuloligamentous restraints to dorsal and palmar carpal translation. J Hand Surg 2003;28A:610 – 613.
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18.
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Dobyns JH, eds. The wrist: diagnosis and operative treatment. 1st ed. St. Louis: Mosby, 1998:73–105. Viegas SF, Patterson RM, Peterson PD, Pogue DJ, Jenkins DK, Sweo TD, et al. Ulnar-sided perilunate instability: an anatomic and biomechanic study. J Hand Surg 1990;15A:268 –278. Slutsky DJ. Arthroscopic dorsal radiocarpal ligament repair. Arthroscopy 2005;21:1486.e1–1486.e8. Mitsuyasu H, Patterson RM, Shah MA, Buford WL, Iwamoto Y, Viegas SF. The role of the dorsal intercarpal ligament in dynamic and static scapholunate instability. J Hand Surg 2004;29A:279 – 288. Morimoto H, Viegas SF, Elder K, Nakamura K, Dasilva MF, Patterson RM. The scaphotrapezio-trapezoidal joint. Part 2. A kinematic study. J Hand Surg 2000;25A:911–920. Morimoto H, Murase T, Goto A, Oka K, Sugamoto K, Yoshikawa H. Capitate-based kinematics of the midcarpal joint during wrist radioulnar deviation: an in vivo three-dimensional motion analysis. J Hand Surg 2004;29A:668 – 675. Kaufmann R, Pfaeffle J, Blankenhorn B, Stabile K, Robertson D, Goitz R. Kinematics of the midcarpal and radiocarpal joints in radioulnar deviation: an in vitro study. J Hand Surg 2005;30A:937– 942. Patterson RM, Williams L, Andersen CR, Koh S, Viegas SF. Carpal kinematics during simulated active and passive motion of the wrist. J Hand Surg 2007;32A:1013–1019.
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8. Trail AI, Stanley JK, Hayton MJ. Twenty questions on carpal instability. J Hand Surg 2007;32E:240 –255. 9. Short WH, Werner FW, Green JK, Sutton LG, Brutus JP. Biomechanical evaluation of the ligamentous stabilizers of the scaphoid and lunate: part III. J Hand Surg 2007;32A:297–309. 10. Viegas SF, Yamagichi S, Boyd NI, Patterson RM. The dorsal ligaments of the wrist: anatomy, mechanical properties, and function. J Hand Surg 1999;24A:456 – 468. 11. Mayfield JK, Johnson RP, Kilcoyne RF. The ligaments of the wrist and their functional significance. Anat Rec 1976;186:417– 428. 12. Morimoto H, Viegas SF, Nakamura K, DaSilva MF, Patterson RM. The scaphotrapezio-trapezoidal joint. Part 1: an anatomic and radiographic study. J Hand Surg 2000;25A:899 –910. 13. Nakamura K, Patterson RM, Moritomo H, Viegas SF. Type I versus type II lunates: ligament anatomy and presence of arthrosis. J Hand Surg 2001;26A:428 – 436. 14. Berger RA, Imeada T, Berglund L, An KN. Constraint and material properties of the subregions of the scapholunate interosseous ligament. J Hand Surg 1999;24A:953–962. 15. Short WH, Werner FW, Green JK, Masaoka S. Biomechanical evaluation of the ligamentous stabilizers of the scaphoid and lunate: part II. J Hand Surg 2005;30A:24 –34. 16. Viegas SF, Tencer AF, Cantrell J, Chang M, Clegg P, Hicks C, et al. Load transfer characteristics of the wrist. Part I. The normal joint. J Hand Surg 1987;12A:971–978. 17. Burger RA. Ligament anatomy. In: Cooney WP, Linscheid RI,
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