Ulnar collateral ligament injury of the thumb

07/23/2015

by Steven D. Sun | MD

 

Ulnar collateral ligament is a fairly common injury. It was first coined “gamekeeper’s thumb” which referred to a chronic injury and slow attenuation of the ligament with repetitive strain. The repetitive strain occurred when gamekeepers wrung the necks of wounded rabbits.

More recently, the term “skiers thumb” has been used and more accurately describes what is seen more commonly now. That is an acute injury to the ligament occurring from a fall on an outstretched hand with the thumb abducted.

The treatment of ulnar collateral ligament injuries is different for partial vs. complete tears. To accurately assess the ligament, the joint is tested in 30 degrees of flexion and in full extension. The test in flexion, evaluates the proper collateral ligament, which lies dorsal and prevents volar subluxation and is the primary restraint to valgus stress with the joint in flexion. While testing in extension assesses both the proper and the accessory collateral ligament. Greater than 30 degrees of laxity in either position is consistent with probable rupture. 

Partial tears (stable in flexion and extension) are treated conservatively with immobilization for six weeks. If the joint is found to be unstable in testing or there is a displaced or rotated fracture fragment that is more than one third of the joint surface, surgery is often considered.

One reason that complete ruptures do not do well with conservative treatment is the Stener lesion. In a subset of patients, the ligament becomes displaced proximal and superficial to the adductor aponeurosis. The aponeurosis prevents the apposition of the ligament back to its insertion site. This complication of complete UCL tears, shows a frequency from 33% to 80% in the literature.

There are a few important points to remember. The first is that there is a finite time when a direct repair is feasible. Ideally, the operation takes place within two weeks. After this time, the ligament starts retracting and contracting and makes the repair difficult or impossible. The second is that often times a complete rupture of the ligament is subtle.

Over the summer, I had a slip and fall onto my thumb. I instantly knew that I tore my ulnar collateral ligament. However, I was surprised on how well I could function. Of course there was pain, but the instability was relatively subtle. I saw first hand (pun intended), how easily this diagnosis could be missed. I underwent surgery three days after injury and was back to full activities in three months. 

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