Dr. Ebraheim’s educational animated video describes fractures of the scaphoid carpal bone.
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The scaphoid is the most common carpal bone to fracture. Fracture of the scaphoid usually occurs from a fall onto an outstretched hand. The patient usually experiences wrist pain and some swelling. The patient may not seek medical advice, thinking that this is a wrist sprain. The patient may get an x - ray and the x-ray intially may be negative (scaphoid fracture could be missed). The blood supply of the scaphoid bone is very unique. The fracture may have difficulty in healing. In fact, avascular necrosis of the proximal fragment may occur with fracture of the scaphoid bone. The scaphoid is a small bone, however if it fractured, there could be a bad result. Always look for tenderness at the anatomic "snuffbox" and pain on axial load. Even if the x-ray is negative, you should immobilize the wrist adequately with a thumb spica cast for a short period of time (10 days to 2 weeks).
When a fracture of the scaphoid occurs, it can be slow to heal due to the limited circulation of blood to the bone. The blood supply of the scaphoid is unique and tenuous. The primary blood supply enters the dorsal ridge and it runs retrograde to the proximal scaphoid. The dorsal blood supply comes from the dorsal carpal branch of the radial artery. The dorsal blood supply comes from the dorsal carpal branch of the radial artery and supplies the proximal 80% of the scaphoid through retrograde blood flow. The volar blood supply comes from the superficial palmar branch of the radial artery and enters the distal tubercle, supplying the distal 20% of the scaphoid. Scaphoid fractures can lead to nonunion and avascular necrosis due to interruption of the blood supply. The more proximal the fracture, the more likely that the fracture will develop nonunion and AVN.
The mechanism of injury for scaphoid fractures is axial load with hyperextension and radially deviation of the wrist. In general, if the fall onto the outstretched hand creates a force that leads to hyperextension, ulnar deviation, and intercarpal supination, then the fracture of the scaphoid may be associated with perilunate dislocation (it will be a transscaphoid perilunate dislocation).
Fractures Types:
Waist Fracture - About 65%. Transverse fracture is more stable. Most frequent fracture site and has moderate risk of AVN and nonunion.
Distal Third Fracture - Occurs in about 10%. Most common location in children (controversial).
Proximal Third Fracture - High incidence of nonunion and AVN. Fracture of the proximal pole has a nonunion rate of 40 - 50%.
Tuberosity Fracture - Rare.
RADIOLOGY
AP VIEW, LATERAL VIEW, SCAPHOID VIEW – Scaphoid view - 30° wrist extension and 20° ulnar deviation.
If the x-rays are negative and there is a high clinical suspicion of a scaphoid fracture, then immobilize the fracture and repeat the x-rays in 2-3 weeks. Bone scan will give fracture diagnosis in 72 hours. MRI can be used for early diagnosis of the fracture. MRI is very sensitive and will diagnose fracture in less than 24 hours. MRI can also show the AVN and vascularity of the proximal fragment of the proximal pole. CT scan may be helpful in diagnosing healing of the fracture. To check for nonunion, you get the CT scan along the scaphoid axis.
TREATMENT OF SCAPHOID FRACTURES
A thumb spica cast is used for stable, nondisplaced fracture or if the x-ray is negative, but there is a high index for suspicion of a scaphoid fracture. In this situation, you will put the thumb spica cast and reevaluate the patient in 2 - 3 weeks. Then remove the cast and get an x-ray. If the patient continues to have pain and the x-rays continue to be negative, then get an MRI and reapply the thumb spica cast and follow the patient closely. This is done because the patient has pain. If the patient does not have pain then get rid of the cast and do not get an MRI. The question is: Do you use a short or long arm thumb spica cast? What is the duration of time for the patient to wear the thumb spica cast? The period of immobilization and healing time of the fracture is decided by the location of the fracture. I think that the expected time for these fractures to heal in a thumb spica cast is: Distal pole - Healing occurs in about 8 weeks. Middle third (waist) - Healing occurs in about 8 - 12 weeks. Proximal third - Healing occurs in between 5 - 6 months. It takes a longer time for the proximal third of the scaphoid fracture to heal. Proximal fractures are very slow to heal in a cast.
