Carpal Ligament Injuries, Pathomechanics, and Classification

Abstract

Carpal instability is a complex array of maladaptive and posttraumatic conditions that lead to the inability of the wrist to maintain anatomic relationships under normal loads. Many different classification schemes have evolved to explain the mechanistic evolution and pathophysiology of carpal instability, including 2 of the most common malalignment patterns: volar intercalated segment instability and the more common dorsal intercalated segment instability. Recent classifications emphasize the relationships within and between the rows of carpal bones. Future research is likely to unify the disparate paradigms used to describe wrist instability.

Keywords: Carpal instability; Carpal ligament injuries; Classification; Pathomechanics; Perilunate instability.

Figure 1

Stages of progressive perilunar instability. Stage I involves disruption of the scapholunate ligamentous complex (arrow). In stage II, the force propagates through the space of Poirier and interrupts the lunocapitate connection (arrow). In stage III, the lunotriquetral connection is violated, and the entire carpus separates from the lunate. In stage IV, the lunate dislocates from its fossa into the carpal tunnel, the lunate rotates into the carpal tunnel, and the capitate becomes aligned with the radius (arrow). (From Kozin SH: Perilunate injuries: diagnosis and treatment. J Am Acad Orthop Surg 1998;6:114–20; with permission.)

Figure 2

Perilunar instability. Stage I (top) refers to perilunate dislocations with dorsal dislocation on the left and the rarer volar perilunate dislocation on the right. Stage II (bottom) refers to lunate dislocations with volar lunate dislocation on the left and the rarer dorsal lunate dislocation on the right. Stage II can be broken down into stage IIA with <90°dof lunate rotation and stage IIB with >90°fof lunate rotation, or enucleation. (From Herzberg G: Acute dorsal trans-scaphoid perilunate dislocations: open reduction and internal fixation. Tech Hand Up Extrem Surg 2000;4:2–13; with permission.)

Figure 3

The lesser and greater carpal arcs of perilunate instability. (From Kozin SH: Perilunate injuries: Diagnosis and treatment. J Am Acad Orthop Surg 1998;6:114–20; with permission)

Figure 4

DISI and VISI deformities of the wrist. (From Garcia-Elias M: Carpal instability. In: Wolfe SW, Hotchkiss RN, Pederson WC, Kozin SH, eds. Green’s Operative Hand Surgery. 6th ed. Philadelphia, PA: Churchill Livingstone Elsevier; 2011:470; with permission.)

Figure 5

Example of a SLAC wrist. Osteophyte formation is noted at the radial styloid-scaphoid articulation (arrow). (From Garcia-Elias M: Carpal instability. In: Wolfe SW, Hotchkiss RN, Pederson WC, Kozin SH, eds. Green’s Operative Hand Surgery. 6th ed. Philadelphia, PA: Churchill Livingstone Elsevier; 2011:493; with permission)

Figure 6

Scaphoid shift test. Pressure is applied to the scaphoid tuberosity as the wrist is moved from ulnar to radial deviation (curved arrow). Disruption to the SLIL will cause the proximal pole of the scaphoid to subluxate dorsally relative to the radius (straight arrow). As pressure is released, a dramatic clunk is noted as the scaphoid falls back into normal position. (From Garcia-Elias M: Carpal instability. In: Wolfe SW, Hotchkiss RN, Pederson WC, Kozin SH, eds. Green’s Operative Hand Surgery. 6th ed. Philadelphia, PA: Churchill Livingstone Elsevier; 2011:483; with permission.)

Figure 7

Posteroanterior (top) and lateral (bottom) radiographs showing the cortical ring sign (arrow) produced by the foreshortened distal pole of the flexed scaphoid and increased scapholunate angle (arrowhead). (From Walsh JJ: Current status of scapholunate interosseus ligament injuries. J Am Acad Orthop Surg 2002;10:32–42; with permission)

Figure 8

Pathomechanics of CIND-VISI. (A) As the wrist reaches the extreme of ulnar deviation (large arrow), the proximal row abruptly rotates into an extended position, producing a palpable “catch-up clunk”ain the process (small arrow). (B) The lunate assumes an extended posture (dashed outline). (From Wolfe SW: Carpal instability nondissociative. J Am Acad Orthop Surg 2012;20:575–85; with permission.)

Figure 9

Dorsal capitate-displacement test. Longitudinal traction with flexion and ulnar deviation is applied to the wrist as dorsal pressure is applied (arrow) to the scaphoid tuberosity. The clunk occurs from dorsal subluxation of the capitate as the proximal row extends during ulnar deviation. C = capitate, L = lunate, R = radius, S = scaphoid. (From Wolfe SW: Carpal instability nondissociative. J Am Acad Orthop Surg 2012;20:575–85; with permission)

Figure 10

(A) Preoperative posteroanterior and (B) lateral radiographs demonstrating transscaphoid perilunate fracture-dislocation. (From Hildebrand KA, Ross DC, Patterson SD, et al: Dorsal perilunate dislocations and fracture dislocations: questionnaire, clinical, and radiographic evaluation. J Hand Surg Am 2000;25:1069–79; with permission.)

Figure 11

Axial dislocations. (A–C) In axial radial dislocations, the ulnar column remains reduced relative to the radius while the radial column is displaced. (D–F) In axial ulnar dislocations, the radial column remains reduced relative to the radius while the ulnar column is displaced. (From Garcia-Elias M, Dobyns JH, Cooney WP III, et al: Traumatic axial dislocations of the carpus. J Hand Surg Am 1989;14:446–57; with permission.)