MALLET FINGER
("DROP FINGER")
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What is a Mallet Finger?
Related articles: broken fingertip, broken finger, broken hand, jersey finger (finger tendon injury), flexor tendon laceration
Mallet finger is an injury to the tendon that moves your finger. More specifically it is a tear of the extensor tendon, which is responsible for straightening out the tip of your finger, like when you point to something with your index finger.
The extensor muscle starts in your forearm and then turns into the tendon, which inserts onto the tip of the finger (just before the finger nail).
This injury occurs when your finger is forced to bend too fast. Our tendons are like rubber bands that can stretch out if pulled slowly, but will snap if pulled too quickly.
Usually the tendon tears, but sometimes the tendon itself rips off where its attached to the finger bone, and it pulls off a small piece of bone. Think of it like pulling a plant out of the ground by its roots. This is called an "avulsion" injury. It occurs about 20% of the time.
How is a Mallet Finger diagnosed?
The Mallet Finger injury is usually diagnosed based on examining the finger.
A person reports "jamming" their finger and now they cannot fully extend that finger. The injured finger can straighten out except for the finger tip, which hangs at a 45 degree angle.
Doctors will get an x-ray of the affected finger to see if its an "avulsion" type injury (you will see the chip of bone on x-ray). The avulsion type injury is important to identify because it can be more problematic than a torn tendon. The bone chip that got pulled off with the tendon is usually part of the finger joint, and when too much of the joint has been damaged with this injury (doctors typically draw the line at around 50% of the joint), then the joint becomes unstable, and the finger tip bone (the distal phalanx) will not stay in place (we call this a partial dislocation, or "subluxation"). This needs to be treated differently than the more common type of mallet finger.
How is a Mallet Finger treated?
This injury is usually treated by splinting the finger in full extension (completely straight) for 6-8 weeks. During this time, it is critical that the finger remains in extension at all times (there is no cheating, not even a little bit). If the fingertip flexes down just once...you have to restart the clock. But, if the finger is kept straight the whole time, the tendon has time to heal, and the outcome is very good.
Surgery is recommended if a large piece of bone gets pulled off with the tendon (this is called an "avulsion injury") and it causes the finger tip to become unstable (the joint will partially or fully dislocate).
Surgery is also recommended if the bone fragment gets pulled away (more than 2 mm) so that there is a better chance that the injury will heal. Surgery typically uses 2 pins (the technique is "extension block pinning") to holds the fragment of bone into place for about 4 weeks. Sometimes the fragment of bone is fixed into place with a tiny screw or a few stitches.
What is the long term outcome?
If the injury is straightforward and is placed into a finger splint, there are rarely complications with healing and patients do well.
If the injury is complicated by an unstable finger tip, and surgery is required, then there is a higher rate of complications. In fact this part of the finger has a fairly high complication rate because there is very little soft tissue surrounding the bone (the bone sits just underneath the skin). This makes its easy for infections and other healing problems to occur. Therefore these injuries do best when they dont need surgery. Sometimes surgery is unavoidable and you should then talk with your surgeon in greater detail about the risks of this injury.
Reference
1) Bendre AA et al. Mallet finger. JAAOS 2005; 13: 336-44. full article. review.
2) Katzman BM et al. Immobilization of the mallet finger: effects on the extensor tendon. J Hand Surg Br 1999; 24: 80-84. full article. cadaver study showed terminal extensor tendon not affected by PIP position, only need to immobilize the DIP joint to enable healing.
3) Okafor B et al. Mallet deformity of the finger: five-year follow-up of conservative treatment. JBJS Br 1997; 79: 544-47. full article. 32 pt, all nonop, 90% satisfaction, no pain, only 8 degree extensor deficit, no need for later surgical intervention.
4) Wehbe MA, Schneider LH. Mallet fractures. JBJS 1984; 66: 658-669. full article. bony mallet: 6 op, 15 nonop, all did well and no advantage to surgery, rec ignore joint sublux. biggest complication was dorsal bony prominence over dip.
5) Hofmeister EP et al. Extension block pinning for large mallet fractures. J Hand Surg 2003; 28: 453-59. full article. 23 pt, avg 40% joint involved, no major/5 minor complications, 92% good-excellent results at 1 yr, 5 degree lag, 75 degree motion.
6) Patel MR et a. Conservative management of chronic mallet finger. J Hand Surg 1986; 11: 570-3. full article. 9/10 cases good-excellent results with nonop (avg 4-18 wks old at start of rx); 2 pt recurrence after stopping rx, which improved after 8 wks more splint.
6) Stern PJ, Kastrup JJ. Complications and prognosis of treatment of mallet finger. J Hand Surg 1988; 13: 329-34. full article. minor complication rate nonop and op are about 40%. nail plate deformity or skin maceration. all nonop were transient whereas op were longer lasting.