The classification of skier's thumb is based on:

1.    Whether a Fracture is present or not -
              a.    Displaced
              b.    Undisplaced

2.    Whether the thumb is Stable / Unstable– Instability is defined as laxity 10* greater than opposite side with the thumb assessed in approximately 20* flexion.

Fractures
1.    Undisplaced & thumb stable – treat with splint.

             

2.    Rotated fracture but thumb stable – treat with surgery to prevent irritability in the MCP joint . The degree of articular incongruity is greater than the Xray reveals due to the cartilage which does not show up on Xray. These injuries will end up stable with splint treatment but the problem is that the joint surface is irregular and may be associated with longterm pain. Early resection of the fragment and ligament reattachment to bone using an anchor  or fixation of the fragment if it is large is much easier performed early than dealing with the pain later.

  
                                    
3.    Widely displaced fracture with instability ( eg Stener lesion – Needs surgery

   

          
No fracture:

4.    Stable – treat in a splint. Often more painful than complete tears. Pain on stressing the ligament but stable.

5.    Unstable- With or without Stener lesion -  Needs surgery to repair ligament assuming the potential for a Stener lesion .