Thumb UCL Sprains – Understanding Mike Trout’s Injury

May 30th, 2017
baseball injuries: pitchers vs field players

Mike Trout, the Los Angeles Angels’ star outfielder, will undergo surgery tomorrow for a torn ulnar collateral ligament (UCL) in his left thumb. The injury occurred – as most of these do in baseball – when the 25 year-old slid into second on a stolen-base attempt on Sunday. Trout, who throws and bats right handed, had an MRI later that day that confirmed the tear. This will be Trout’s first stint on the DL and it will be for a significant period.

Some catchers wear a thumb splint on their glove hand to prevent thumb sprains, and a number of hitters wear a protective splint on their top hand when batting. However, it seems that most players wait until after an injury of this nature to wear the oven-mitt like support that is available to help prevent UCL sprains with base running. When worn, the player dons the mitt once he gets on base. That simple measure could spare so many of these injuries, saving the seasons of so many players and in turn, their teams. The Angels will really feel Mike Trout’s absence.

More on the UCL

A ligament is the connective tissue that connects one bone to another to provide stability at a joint. Each joint has at least one ligament on each side. In the hand or elbow, the inner (medial) side, or side of the ulna bone in the forearm, is called the ulnar side, and the outer (lateral) side is called the radial side because of its relationship to the radius (the outer bone in the forearm). Thus the medial ligament is called the ulnar collateral ligament.

We talk about the UCL at the elbow a great deal in baseball, as it is the ligament most often torn by pitchers and subsequently reconstructed with the Tommy John procedure. At the base of the thumb, just as at the elbow, the UCL stabilizes the innermost aspect of the joint. This joint, between the first long bone of the hand and the thumb is called the metacarophalangeal joint, or MCP.

When trauma forces the thumb away from the palm beyond the extensibility of the ligament and normal range of motion of the MCP joint, the ligament is stretched and can be torn. Sprains range from a Grade 1 – which is a mild tweak – to a Grade 3, which is a complete rupture. It is these that generally require surgical intervention.

Other names for the UCL tear of the thumb

Also sometimes referred to as “Skiers’ Thumb” because of its prevalence on the slopes, this injury used to be known as “Gamekeepers Thumb” because it was commonly found amongst Scottish Gamekeepers (wildlife managers) as a result of a repetitive stress and stretch to the ligament that they suffered when doing their work.

A skier who falls while holding the pole, or anyone who tries to break a fall by reaching out with his hand to absorb the impact may suffer a UCL sprain. If the thumb is bent backwards and a ligament tears, it is unlikely to be able to heal in the anatomical position because of the resultant instability of the joint. This is why surgery may be necessary.

Occasionally, the UCL ligament may not tear but instead might pull off a chip of bone at its point of attachment (at the base of the thumb). This injury is called an avulsion fracture and it too can result in instability at the joint if not corrected surgically.