There are a range of different extensor tendon injuries caused by different mechanisms.
A ‘mallet’ injury is caused by disruption of the extensor tendon as it inserts onto the dorsum (back) of the distal phalanx (the tip of the finger). This may result from a laceration over the dorsum of the joint (open) or a force applied to the tip of the finger, such as a ball (closed). A mallet injury is characterised by an inability to extend the distal interphalangeal joint (the joint at the tip of the finger). It can cause a small fracture of the bone. Depending on the severity of the injury, it may be treated with splinting or surgically. If not treated this injury may result in a ‘swan neck deformity’; hyperextension of the proximal interphalangeal joint (the middle joint of the finger) and an extensor lag (inability to extend) the distal interphalangeal joint (the joint at the top of the finger).
Another extensor tendon injury may be caused by disruption of the central slip at the proximal interphalangeal joint (the middle joint of the finger). If left untreated a central slip injury may result in a boutonnière deformity. This is characterised by an extensor lag (inability to extend) at the proximal interphalangeal joint (the middle joint of the finger) and hyperextension at the distal interphalangeal joint (the joint at the tip of the finger).
Open extensor tendon injuries are usually caused by a laceration or crush injury. These injuries have been associated with poor functional outcomes in the past according to scientific literature. Mr Ecker is in the process of publishing his results for surgery to treat open extensor tendon injuries in the Journal of Hand Surgery (European Volume), for which he achieved 86% good or excellent results.
