The scaphoid bone (also called the navicular bone) is one of eight carpal (wrist) bones. These small bones allow complex, yet delicate movements of the hand. The carpal bones fit between the forearm and hand bones. The scaphoid sits below the thumb, and is shaped something like a kidney bean.
Blood flow to the scaphoid:
The interesting thing about the scaphoid bone is that is has a retrograde blood supply. This means that the blood flow comes from a small vessel that enters the most distant part of the bone and flows back through the bone to give nutrition to the bone cells.
The pattern of blood supply in the scaphoid presents a problem when you sustain a scaphoid fracture. Because of the tenuous blood supply, a scaphoid fracture can sever this blood flow and stop the delivery of necessary oxygen and nutrients to the bone cells. When this occurs, healing can be slow, and the scaphoid fracture may not heal at all.
Symptoms of a scaphoid fracture:
The symptoms of a scaphoid fracture are pain on the thumb side of the wrist, swelling in that area, and difficulty gripping objects. Many patients are diagnosed with a wrist sprain, when in actuality they have a broken scaphoid bone. The diagnosis is difficult because x-rays taken right after the injury may show no abnormality. A scaphoid fracture that is not displaced may only show up on x-ray after healing has begun, which can be one to two weeks after the injury. Because of this, it is not uncommon to treat a wrist injury with immobilization (as though it were a scaphoid fracture) for a week or two and then repeat x-rays to see if the bone is broken. An MRI or bone scan is also a possible means to diagnose this injury, but usually not needed.
Problems with scaphoid fracture healing:
When a scaphoid fracture heals slowly (delayed union), or does not heal at all (non-union), the injury may remain painful, and deformity and arthritis of the bone may result. The risk of developing a non-union of the scaphoid depends most importantly on the location of the fracture in the bone. Other factors that can contribute to non-union are smoking, certain medications, and infections.
Treatment of scaphoid fractures:
There are two general approaches for treatment of a scaphoid fracture. Often, orthopedists will initially treat the injury in a cast to see if the fracture heals in a timely manner. So long as the scaphoid fracture is not badly displaced (out of position), this is an excellent approach. By obtaining repeat x-rays over several weeks and months, your doctor can look for signs of healing. Healing of this fracture usually takes 10 to 12 weeks. If it does not heal, surgery can be considered.
If the scaphoid fracture is displaced, the risk of nonunion is higher, and your doctor may recommend initial surgery to reposition the bones, and fix them into place. Or if the fracture does not heal with cast treatment (immobilization), surgery will be recommended. The surgery involves using either a screw or small pins to hold the bone together in the proper position. A bone graft may also be used to promote healing at the scaphoid fracture site. The surgical incision will be between two and five centimeters, depending on the dissection necessary to properly position the fracture and place bone graft (if needed). After surgery, a cast is used to immobilize the scaphoid bone and allow for healing.