Mallet vs Jersey Finger
Again a blog post inspired by a movie. I was watching “Mission Impossible: Fallout” on a flight to Perth for a conference; I’m sure this was how it was made to be viewed. Towards the end of the movie I was captivated by Tom Cruise. In this particular scene, as he is is heading towards the edge of a cliff, he throws out one hand and grabs a crack in the cliff face to stop his fall thus putting all the force of his momentum through his hand and arm. Mr Cruise is left dangling but safe on the edge of the rock. Now I was speculating with Dr Rando about how bad his dislocated shoulder would be in this situation. He pointed out to me that the forces affecting Tom in gripping a rock at speed would be far more likely to have torn the flexor tendon in each of his fingers leading to a full set of jersey fingers. I wonder if Tom is familiar with these injuries?
Anatomy of the Finger
Your hands are complex tools- the finger tips alone contain 2500 touch receptors per square centimeter and there are 17,000 touch receptors in total for each hand (I don’t know who counted these). Its only when our periphery is injured do we fully find out how complex and important our hands are.
As discussed in a previous article, if you look at your finger you will see three hinges, or joints, that move the finger and provide us with the grip we require. The joint closest to your fingernail is called the ‘distal interphalangeal joint’ (DIPJ), the middle joint is the ‘proximal interphalangeal joint’ and the one closest to the base of the finger is the ‘metacarpophalangeal joint’. The pathology we need to focus on for Tom is the DIPJ which is particularly prone to sporting injury due to its position.
The DIPJ will move from 0 degrees to 85 degrees. To achieve this movement a tendon runs up both he top and the bottom of the finger and joins to the base of the distal phalanx, the bone at the tip of your finger that sits underneath your fingernail. For a joint to function it needs to be moved by a muscle; the muscle is connected to the bone by a tendon.
Often the muscle can be some distance from the bone and joint that they move relying on the an long tendon to form a “pulley” to effectively move the joint. The best example of this is the hand where muscles in the forearm are responsible for the movement of the fingers in the hand. As the tendon travels from the muscle in the forearm to the bone at the tip of the finger if it is disrupted in any way movement of the finger will be affected as no matter how strong the muscle is the joint cannot move if the tendon is not attached. In the hand, if the tendon is disrupted on top the finger it is described as a Mallet Finger and if it is disrupted on the bottom of the finger it is called a Jersey Finger.
Why the crazy names?
Mallet fingers tend to occur with blunt force like when a mallet hits a nail. This is usually from a basketball or softball hitting your finger tip, moving it downwards with extreme force and rupturing the tendon. This injury can also occur through direct trauma to your finger such as in contact sports. In America it is known as Baseball Finger due to its association with their national sport. Mallet finger tends to affect your middle finger mainly as it is the furthermost finger when gripping.
Jersey finger on other hand is named after the injury that occurs when your finger gets caught in the jersey of another football player such as might happen during a tackle. This sees your finger tip forcefully bent backwards as the other player quickly pulls away. Due to anatomical weakness your ring finger is most often involved in these injuries (75% of injuries).
What does the injury look like?
Mallet Finger injury causes swelling of the joint, bruising and deformity. Your injured finger remains bent and is unable to be straightened or extended by the patient. An xray is needed to confirm if a fracture is present or if the joint is involved.
Jersey Finger is demonstrated when a patient is unable to make a full fist and there is a loss in the ability to flex the finger tip. Once again there will be swelling and bruising at the site of tendon rupture.
How is it treated?
Mallet Finger is treated by straight splinting of your finger for two months. It is very important to maintain splinting and to keep the finger straight throughout as any flexion of the hand can disrupt healing. Further to this splinting should continue during athletic activity for an extra month after the initial 2 months is completed. Sometimes surgery is required for repair. Specialised hand occupational therapy is highly recommended in both surgical and non-surgical management. Return to playing sport is usually after 2-3 months.
Jersey Finger is different. Due to retraction of the flexor tendon, surgical treatment is always required from the outset in order to reattach the flexor tendon to the distal phalanx. Once again hand occupational therapy and finger exercises are important for rehabilitation. Players can usually return to sport in 8-12 weeks.
So really when Tom flings out his hand to stop his fall down a cliff he would instantly rupture his flexor tendons. He would then be unable to grip the cliff and would have to be rescued, operated on and then rehabilitated for 2-3 months before continuing to chase the baddies. This may affect the pacing of the film but would improve the medical accuracy.
So in conclusion our fingers are important and seemingly simple injuries can often become chronic and cause irritation that is unnecessary. Mallet Fingers need a splint, Jersey Fingers need surgery. Both end up with a return to play in 2-3 months. It is important to see a hand specialist as soon as an injury is identified. And Mission Impossible:Fallout makes for a quick flight to Perth, scoring four out of five flexor tendon ruptures.
- GPearls on the GC
- finger injuries should be seen quickly even if they appear to be not so serious
- splint a mallet, repair a jersey
- direct blow on a finger by a jersey cow will confuse the issue