Scapho Lunate Ligament
The Scapho-lunate ligament rupture is the commonest ligament injury in the wrist. It connects the scaphoid and lunate bones together and stops them from being prised apart. If left untreated the wrist can deteriorate and become arthritic over the following 5-10 years. This is the so-called SLAC wrist (Scapho-Lunate-Advanced-Collapse)
The mechanism of injury is often a fall onto an outstretched hand and wrist.
Pain is well localised to the back of the wrist centrally. Patients often lose wrist extension (cock wrist back). Occasionally they will notice clunking and a feeling of giving way of the wrist.
Plain x-rays may show a gap between the scaphoid and lunate on the AP (front on) view. On the lateral (side on) x-ray view sometimes the lunate bone may be falling backwards called a DISI deformity (Dorsal Intercalated Segment Instability). In the x-ray below right the red arrow shows an increased gap between the scaphoid and lunate.
Often however the x-rays can be normal, but on stress grip views, the bones can move apart and be shown on the images. In such situations the patient is asked to grip a wooden bar as hard as a possible. This puts stress on the wrist and allows the bones to be prised apart and shown up on X-ray. this is described as a dynamic X-ray.
MRI scans show the bones, ligaments and the bone angles in respect of each other. An MRI arthrogram involves an injection dye into the wrist under x-ray control. An MRI is then performed. The MRI can see where the dye has tracked and any abnormal areas of dye collection can help identify the injuries sustained.