Scapholunate dissociation
Updates to Article Attributes
Scapholunate dissociation represents a significant ligamentous wrist injury that is important to identify on imaging. There is disruption of the scapholunate ligament with resultant instability. The condition may also be known as rotary subluxation of the scaphoid.
Epidemiology
Scapholunate dissociation most commonly results from trauma. It is the leading cause of SLAC wrist,which which is the most common pattern of degenerative arthritis in the wrist 4.
Clinical presentation
Scapholunate dissociation usually presents following a fall with minimal swelling and pain localised over the dorsal scapholunate region. Presentation is often delayed in the absence of an associated fracture. Pain is increased by dorsiflexion.
Pathology
The scapholunate ligament is a U-shape ligament which is arbitrarily divided into three anatomic compartments: dorsal, intermediate and volar. The dorsal compartment is 3 mm in thickness and composed of short, transversely oriented collagen fibres which plays a more important role by resisting volar-dorsal translation than other compartments. The volar compartment measures 1mm1 mm in thickness. The proximal or intermediate compartment is mainly made of fibrocartilage, like a meniscus.5
Injury of the scapholunate ligament (complete tear of the dorsal component) and radiolunate ligament will result in scapholunate dissociation. Mayfield et al. have proposed a 4 stagefour-stage process to describe perilunar wrist instability where scapholunate dissociation represents stage 1 2.
Radiographic features
Plain filmradiograph
The scapholunate interval should be measured at the midpoint of the adjacent parallel articular contours of the two bones (the proximal part is wider and the distal part is narrower). AP radiographs may demonstrate widened scapholunate space greater than 4 mm, known as the Terry Thomas sign. This is exacerbated in clenched fist views and PA views with the wrist in ulnar deviation. The scaphoid rotates to a more transverse position which will often increase the scapholunate angle to greater than 60 degrees. When this rotation causes the scaphoid to be viewed end-on it may produce an appearance termed the 'signet-ring sign'.
Treatment and prognosis
Surgical repair or reconstruction of the scapholunate interosseous ligament is normally required to prevent long-term complications 3, namely proximal migration of the capitate between the scaphoid and lunate with resultant degenerative disease known as SLAC wrist (scapholunate advanced collapse).
-<p><strong>Scapholunate dissociation</strong> represents a significant ligamentous wrist injury that is important to identify on imaging. There is disruption of the scapholunate ligament with resultant instability. The condition may also be known as <strong>rotary subluxation of the scaphoid</strong>.</p><h4>Epidemiology</h4><p>Scapholunate dissociation most commonly results from trauma. It is the leading cause of <a href="/articles/slac-wrist">SLAC wrist </a>which is the most common pattern of degenerative arthritis in the wrist <sup>4</sup>.</p><h4>Clinical presentation</h4><p>Scapholunate dissociation usually presents following a fall with minimal swelling and pain localised over the dorsal scapholunate region. Presentation is often delayed in the absence of an associated fracture. Pain is increased by dorsiflexion.</p><h4>Pathology</h4><p>The <a href="/articles/scapholunate-ligament-complex">scapholunate ligament</a> is a U-shape ligament which is arbitrarily divided into three anatomic compartments: dorsal, intermediate and volar. The dorsal compartment is 3 mm in thickness and composed of short, transversely oriented collagen fibres which plays more important role by resisting volar-dorsal translation than other compartments. The volar compartment measures 1mm in thickness. The proximal or intermediate compartment is mainly made of fibrocartilage, like a meniscus.<sup>5</sup> </p><p>Injury of the scapholunate ligament (complete tear of the dorsal component) and radiolunate ligament will result in scapholunate dissociation. Mayfield et al. have proposed a 4 stage process to describe <a href="/articles/mayfield-classification-of-carpal-instability-perilunate-instability-1">perilunar wrist instability</a> where scapholunate dissociation represents stage 1 <sup>2</sup>.</p><h4>Radiographic features</h4><h5>Plain film</h5><p>The scapholunate interval should be measured at the midpoint of the adjacent parallel articular contours of the two bones (the proximal part is wider and the distal part is narrower). AP radiographs may demonstrate widened scapholunate space greater than 4 mm, known as the <a href="/articles/terry-thomas-sign-1">Terry Thomas sign</a>. This is exacerbated in <a href="/articles/wrist-clenched-fist-view-1">clenched fist views</a> and <a href="/articles/scaphoid-pa-view-2">PA views</a> with the wrist in ulnar deviation. The scaphoid rotates to a more transverse position which will often increase the <a href="/articles/scapholunate-angle">scapholunate angle</a> to greater than 60 degrees. When this rotation causes the scaphoid to be viewed end-on it may produce an appearance termed the 'signet-ring sign'.</p><h4>Treatment and prognosis</h4><p>Surgical repair or reconstruction of the scapholunate interosseous ligament is normally required to prevent long-term complications<sup> 3</sup>, namely proximal migration of the capitate between the scaphoid and lunate with resultant degenerative disease known as <a href="/articles/slac-wrist">SLAC wrist </a>(scapholunate advanced collapse).</p>- +<p><strong>Scapholunate dissociation</strong> represents a significant ligamentous wrist injury that is important to identify on imaging. There is disruption of the scapholunate ligament with resultant instability. The condition may also be known as <strong>rotary subluxation of the scaphoid</strong>.</p><h4>Epidemiology</h4><p>Scapholunate dissociation most commonly results from trauma. It is the leading cause of <a href="/articles/slac-wrist">SLAC wrist,</a> which is the most common pattern of degenerative arthritis in the wrist <sup>4</sup>.</p><h4>Clinical presentation</h4><p>Scapholunate dissociation usually presents following a fall with minimal swelling and pain localised over the dorsal scapholunate region. Presentation is often delayed in the absence of an associated fracture. Pain is increased by dorsiflexion.</p><h4>Pathology</h4><p>The <a href="/articles/scapholunate-ligament-complex">scapholunate ligament</a> is a U-shape ligament which is arbitrarily divided into three anatomic compartments: dorsal, intermediate and volar. The dorsal compartment is 3 mm in thickness and composed of short, transversely oriented collagen fibres which plays a more important role by resisting volar-dorsal translation than other compartments. The volar compartment measures 1 mm in thickness. The proximal or intermediate compartment is mainly made of fibrocartilage, like a meniscus.<sup>5</sup> </p><p>Injury of the scapholunate ligament (complete tear of the dorsal component) and radiolunate ligament will result in scapholunate dissociation. Mayfield et al have proposed a four-stage process to describe <a href="/articles/mayfield-classification-of-carpal-instability-perilunate-instability-1">perilunar wrist instability</a> where scapholunate dissociation represents stage 1 <sup>2</sup>.</p><h4>Radiographic features</h4><h5>Plain radiograph</h5><p>The scapholunate interval should be measured at the midpoint of the adjacent parallel articular contours of the two bones (the proximal part is wider and the distal part is narrower). AP radiographs may demonstrate widened scapholunate space greater than 4 mm, known as the <a href="/articles/terry-thomas-sign-1">Terry Thomas sign</a>. This is exacerbated in <a href="/articles/wrist-clenched-fist-view-1">clenched fist views</a> and <a href="/articles/scaphoid-pa-view-2">PA views</a> with the wrist in ulnar deviation. The scaphoid rotates to a more transverse position which will often increase the <a href="/articles/scapholunate-angle">scapholunate angle</a> to greater than 60 degrees. When this rotation causes the scaphoid to be viewed end-on it may produce an appearance termed the 'signet-ring sign'.</p><h4>Treatment and prognosis</h4><p>Surgical repair or reconstruction of the scapholunate interosseous ligament is normally required to prevent long-term complications<sup> 3</sup>, namely proximal migration of the capitate between the scaphoid and lunate with resultant degenerative disease known as <a href="/articles/slac-wrist">SLAC wrist </a>(scapholunate advanced collapse).</p>
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