Arch Hand Microsurg.  2021 Jun;26(2):82-92. 10.12790/ahm.21.0082.

Comprehension of Midcarpal Instability

• Kang H

• KMID: 2516152
• DOI: http://doi.org/10.12790/ahm.21.0082

Abstract

The midcarpal instability is the state with instability between the proximal and distal carpal rows, without dissociation between carpal bones. It can be divided into the intrinsic one that is caused by ligament hyperlaxity, and extrinsic one that is caused secondarily by the malunion of distal radius. The pathophysiology of the intrinsic one is still unknown, and the treatment is also controversial. On the other hand, the extrinsic one can be treated by corrective osteotomy of the radial malunion. This review investigated the comprehension, definition, classification, symptoms, diagnosis, and treatment of the midcarpal instability.

Keyword

Midcarpal instability; Ligament; Wrist joint

Figure

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  Fig. 1. Palmar extrinsic ligaments and dorsal extrinsic ligament. THC, triquetral-hamate-capitate ligament (triquetrocapitate [TC]+triquetrohamate [TH]); STT, scapho-trapeizum-trapezoid ligament (scaphocapitate [SC]+scaphotraphezium [ST]); RSC, radioscaphocapitate ligament; LRL, long radio-lunate ligament; SRL, short radio-lunate ligament; UL, ulnolunate ligament; UC, ulnocapitate ligament; DIC, dorsal intercarpal ligaments; DRC, dorsal radiocarpal ligament.

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  Fig. 2. Palmar midcarpal instability. (A) The proximal row is abnormally flexed (volar intercalated segmental instability pattern) with palmar translation of the distal row in the neutral position of the wrist. (B) The proximal row is suddenly extended with clunk during ulnar deviation, suddenly extended (rotated arrow). (C) The hyperlaxity of the ulnar arm of the arcuate ligament (triquetral-hamate-capitate ligament) and dorsal radiotriquetral ligament induced palmar midcarpal instability, ulnar deviation (left side arrow) and arcuate ligament direction (right side arrow).

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  Fig. 3. Dorsal midcarpal instability. (A, B) The proximal row is slightly extended in the neutral position of the wrist (dorsal intercalated segmental instability pattern). (C, D) The capitate and the distal row is suddenly subluxated posteriorly with clunk during ulnar deviation. (rotated arrow). Hyperlaxity of the scaphotriquetral ligament (a part of dorsal intercarpal ligament) in the posterior, and that of the radioscaphocapitate ligament and long radiolunate ligament in the anterior induced dorsal midcarpal instability.

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  Fig. 4. Combined midcarpal instability (A, B). Combined midcarpal instability is often caused by general ligamentous hyperlaxity with ulnar minus variance or with increased radioulnar slope.

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  Fig. 5. Extrinsic midcarpal instability or carpal instability adaptive after distal radius malunion (A, B). After corrective osteotomy, these malalignment and instability are corrected (C). Red lines present the midline of radius, lunate, and capitate.

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  Fig. 6. Volar sagging of the carpus in palmar midcarpal instability.

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  Fig. 7. The midcarpal shift test can be diagnostic for palmar midcarpal instability. This maneuver accentuates the existing palmar subluxation of the distal row and disengages the normal intercarpal contact points. (A) The examiner then moves the wrist into ulnar deviation. (B) As the wrist reaches near the complete ulnar deviation, a strong clunk is felt, and often can be heard, as the distal row snaps back to its physiologic position.

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  Fig. 8. Dynamic posterior shift test. When the wrist is distracted and pressure is applied from the front to the rear of the scaphoid tubercle with the other hand, the capitate is subluxated to the posterior of the lunate (A, B).

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  Fig. 9. Three point volar supporting brace to manage palmar midcarpal instability. volar direction for ulnar head (left arrow), dorsal direction for pisiform (right arrow).

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  Fig. 10. Soft tissue augmentation and reconstruction. (A) Dorsal capsule and dorsal radiotriquetral ligament augmentation. (B) Stabilization of triquetrohamate joint by rerouting of the extensor carpi radialis brevis tendon.

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  Fig. 11. Four corner fusion for palmar midcarpal instability. (A) Midcarpal instability with arthritis. (B) Postoperative state of four corner fusion.

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