Clinical Cases - Forearm & Wrist

M.P., a 28-year-old man, was horseback riding with his girlfriend when the horse he was riding stumbled, throwing him from the saddle. In order to break his fall, M.P. stretched out his right hand, injuring his wrist. M.P. remounted his horse and continued to ride, however, his wrist continued to hurt, with the greatest pain in the region of the anatomical snuffbox. When the ride was finished, he went to the local emergency room to have his wrist examined. The emergency room was crowded that afternoon and the staff was extremely busy. When the resident came in, he gave M.P. a quick examination, decided that the wrist was sprained, wrapped it in an ACE bandage and gave M.P. a prescription for a pain-killer. M.P. left the emergency room and for a couple of weeks, everything seemed to be healing fine. After the medication ran out, however, he began to experience more pain and a loss of movement in the injured wrist. M.P. then went to see his own doctor, who ordered x-rays of the wrist. The radiologist who examined the x-rays determined that M.P. had suffered a fracture of one of the bones of the wrist. The fracture did not appear to be healing, so M.P. was referred to an orthopedic surgeon.

Questions to consider:

1. What is the anatomical snuffbox?

   The anatomical snuffbox is the triangular depression observed on the dorsum of the hand when the thumb is fully extended. It is bounded by the tendons of the extensor pollicis longus on the medial side and the extensor pollicis brevis on the lateral side.

2. What bone did M.P. break? (Hint: It is palpable in the anatomical snuff box.)

   M.P. broke the scaphoid bone, which can be palpated in the floor of the anatomical snuff box. The scaphoid is the most frequently fractured of the carpal bones.

3. What are some of the possible anatomic reasons that this bone failed to heal?

   There are three basic reasons why M.P.'s fracture may have failed to heal:

   1. The blood supply to the scaphoid frequently enters the bone only from its distal end, therefore, a fracture may deprive the proximal fragment of blood, interfering with healing and possibly leading to necrosis of the proximal fragment.
   2. The fracture line may enter a joint with one of the other bones of the wrist, leading to leakage of synovial fluid into the space. The presence of synovial fluid may prevent healing of the fracture.
   3. The scaphoid is not easily immobilized to promote healing, due to its small size and its location.

4. Why might the resident have missed the diagnosis initially?

   Scaphoid fractures produce symptoms that are similar to strains and sprains (synovial effusion, joint pain, and limitation of movement), and thus can easily be confused with a strain or sprain if a careful examination is not performed.

5. What other injuries commonly result from falls on outstretched hands?

   Other injuries that can occur following a fall on outstretched hands include dislocation of the lunate bone, posterior displacement of the distal radial epiphysis (in children), fracture of the clavicle (in adolescents), and fracture of the distal radius (Colles' fracture--usually in older adults).

A 28-year-old volley ball player fell on her right outstretched arm during a game. She felt an immediate pain in her wrist, and the orthopedic surgeon at the emergency room described the deformity in her right wrist as similar to a "dinner fork". All wrist movements were painful. A plain radiograph revealed a transverse fracture of the distal end of the radius, which was tilted backwards and radially. The case was diagnosed as that of a typical Colles' fracture. The fractured forearm was put in a cast for 6-8 weeks.

Questions to consider:

1. What bones may fracture as a result of someone's fall on an outstretched hand?
   

   Most commonly fractured bones are the scaphoid, lower end of the radius, ulnar styloid, lower end and surgical neck of the humerus, and clavicle.

2. Which muscle tendon is more likely to be injured in Colles' fracture?
   

   Extensor pollicis longus tendon.

3. What would be the complication if such a fracture takes place in young children?
   

   Epiphysis will be separated and the growth plate may get crushed. In this case differential radial and ulnar growth may result.

4. What is the basic principle of treating a displaced fracture in this case?
   

   Under general anesthesia the fractured piece is disimpacted by traction. Then the palm is flexed and wrist firmly pronated. The lower radius should be pressed to maintain reduction, plaster of Paris is applied with the wrist flexed, pronated and in ulnar deviation. Check X-ray post-reduction at one week. Remove plaster at 6-8 weeks.