The extensor tendons located on the dorsal surface of the hand, and attached to muscles in the forearm, allow us to stretch our fingers. As they extend to the distal part of the fingers they become thinner and receive at the hand level small tendons of the intrinsic musculature of the hand.

Cause of extensor tendon injuries

Their superficial location on the back of the hand and fingers makes them particularly susceptible to injury from injury or other direct trauma. Bruising, crushing, or simple finger flexion can lead to injury to the distal insertion of the tendon into the bone leading to flexion of the 3rd phalanx with the so-called “hammer toe” that will lead to long immobilization with or without surgery.

Common injuries of the extensor tendons

Cuts on the back of the hand or fingers that affect the extensor tendons usually cause extension deficit of the affected finger in the joints distally to the cut. They are usually treated with tendon suture and splint immobilization for long periods (4 to 7 weeks). Often the use of dynamic splints and physical therapy are necessary after withdrawal from immobilization.

Hammer finger refers to the fall of the last phalanx in the distal joint of the finger associated with a wound, bone tearing or tendon stretching, but the result is always the same: fingertip that cannot be stretched. Closed rupture, associated or not with phalanx fracture, leads to prolonged splint immobilization, tendon cutting requires surgical repair followed by the same immobilization period (7 to 8 weeks).

Button deformation refers to flexural deformation at the level of the proximal interphalangeal joint (in severe and prolonged cases associated with hyperextension at the distal interphalangeal level) associated with cut or rupture of the extensor tendon insertion at the base of the 2nd phalanx. Tendon suture, phalanx reinsertion and immobilization for 5 or 6 weeks are the recommended treatments. Failure to treat this type of injury often leads to fixed flexion stiffness.

What can be expected from treatment

Tendon healing can lead to adhesions to surrounding tissues (skin and bone), the scar tissue that forms can prevent the tendon from stretching or flexing completely even under the best treatment conditions. The use of dynamic splints and physical therapy may be necessary under these conditions.