Locked Scapholunate Instability Presenting as a Progressive Injury

Abstract

Background

Locked scapholunate instability is described as scapholunate instability occurring with a dislocated proximal pole of the scaphoid. Scapholunate instability is an early stage of perilunate instability. While being rare, complete or proximal pole scaphoid dislocations usually occur as an acute injury and often missed.

Case Description

We present a case of locked scapholunate instability where the proximal pole dislocation developed over a period of 6 weeks following injury. In addition, the membranous part of the scapholunate interosseous ligament was avulsed and interposed between the scaphoid and the lunate, blocking the scaphoid reduction.

Literature Review

Multiple ligaments such as the scapholunate interosseous ligament, dorsal intercarpal ligament, and scaphocapitate ligament are likely to be injured in these cases for scaphoid proximal pole to dislocated dorsally, essentially creating a periscaphoid “instability.” Radial-sided “locked periscaphoid” instability, being an intermediate stage between scapholunate instability and perilunate instability, can either progress to perilunate instability or scaphoid dislocation.

Clinical Relevance

It is important to follow these patients up for progressive worsening of symptoms and identifying factors that would hinder reduction.

Keywords

scapholunate instability - locked scapholunate instability - carpal instability - scaphoid dislocation

Publication History

Received: 23 January 2025

Accepted: 16 June 2025

Article published online:
03 July 2025

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