A fracture of the scaphoid, though a relatively frequent wrist injury, is often ignored, overlooked, or mistakenly attributed to a wrist sprain. This is due in large part to the subtlety of its symptoms. Unlike most other broken bones, the area around the scaphoid may not be noticeably swollen or intensely painful.
According to HSS Hand Specialist Scott Wolfe, MD, “because of the scaphoid fracture’s relatively innocuous symptoms, it may be mistaken for a sprain and remain undiagnosed for months or years, leading to long-term consequences of painful arthritis.”
A scaphoid fracture is usually caused by a fall on the outstretched hand, and it occurs most often in young, active patients. Frequently, the injury occurs in sporting events such as skiing or snowboarding, although it can also occur as a result of a motor vehicle accident or similar traumatic force on the hand and wrist.
Dr. Wolfe notes that extra vigilance should be paid to every wrist injury, since the fleeting symptoms of a scaphoid fracture - in addition to its complicated shape and precarious blood supply - can lead to a failure of the two fractured bone ends to unite (also called a nonunion).
The scaphoid (or carpal navicular) resides between the thumb and the bones of the forearm, and it resembles a large cashew nut. It is a crucial component of the wrist mechanism and coordinates the motion and position of all of the other wrist bones.
This color-coded diagram maps each of the 8 carpal bones, with the scaphoid in red.
(3D image provided by Dr. Crisco NIH grant #: AR44005)
Wrist bones are so small, complex, and intricately related that they will rotate out of position, conduct forces abnormally, and begin to cause degenerative arthritis (osteoarthritis) if the scaphoid does not heal in a timely fashion. Since the scaphoid provides cohesiveness and functional coordination to the two rows of carpal bones in the wrist, disruption of the scaphoid allows the two sets of bones to act in an uncoordinated manner. They begin to develop shear forces and high stresses, and that leads to cartilage loss and, eventually, arthritis.
Compounding the issue is the tenuous blood supply to the scaphoid, which is comprised of a dominant vessel which enters the bone at its waist (midsection) along the dorsal (back side) ridge. Since bones require a steady flow of blood to ensure proper healing, the scaphoid is uniquely vulnerable. A fracture through the waist or proximal third of the bone (closest to the forearm) can disrupt the dorsal blood vessel and isolate the proximal fragment (closest to the forearm), preventing its nutrition and, ultimately, its healing. For this reason, Dr. Wolfe stresses that it is imperative that a scaphoid fracture be detected and treated as soon as possible.
A physician can use several methods to determine a possible fracture of the scaphoid. While a comprehensive physical exam is always performed on an injured patient, the imaging of the potential fracture is dependent on the type and timing of injury and the particular physical exam findings.
Symptoms: Bruising or swelling of the wrist following a fall is suggestive of a serious wrist injury, particularly when associated with loss of motion of the thumb or wrist, or pain with hand gripping or lifting. Unlike the more common fracture of the radius, there is usually no visible deformity with a scaphoid fracture.
Physical examination: Tenderness in the anatomical snuffbox (the hollow between the tendons on the thumb side of the wrist) is the characteristic sign of a scaphoid fracture, though it is very non-specific. The doctor will examine several other bony prominences about the wrist and ask the patient to gently move the wrist and thumb through a range of motion. After reviewing symptoms and examining for physical signs, the physician will order a set of x-rays, and possibly additional imaging tests such as a bone scan, computed tomography (CT), or magnetic resonance imaging (MRI).
An acute scaphoid fracture.
Sagittal reformatted computed tomography (CT) scan shows a fracture through the mid waist of the scaphoid (arrow). Three dimensional (3D) reformatted images produced from high resolution CT scanners are often helpful in surgical planning.
(3D image provided by Dr. Crisco NIH grant #: AR44005)
MRI of a scaphoid fracture
In the last decade, there has been an increased awareness among primary care physicians, pediatricians, and general orthopedists in early diagnosis and treatment of scaphoid fractures in order to prevent non-union and generalized wrist arthritis. However, patients should also be vigilant and knowledgeable about scaphoid fractures if they have experienced - or are at risk of experiencing - trauma to the hand or wrist.
“The treatment of scaphoid fractures has seen especially dramatic changes over the last 10 years,” says Dr. Wolfe. “Hand specialists have made surgical treatment safe and reliable to a point where there has been a notable paradigm shift from treating scaphoid fractures in a cast to treating them operatively. In concert with that change in philosophy has been a series of improvements in surgical equipment and techniques. Casting, however, remains a safe and effective option for healing in many cases.”
One challenge of treating scaphoid fractures is their lengthy healing time. The peculiarity of its blood supply is the primary reason for this prolonged healing period. Whereas other fractures in the upper extremity require an average of 6 weeks, a scaphoid fracture requires an average of 12 weeks if treated immediately, and as long as 6 months if the diagnosis is delayed.
Each scaphoid fracture is different, however, and as a result of these differences, the treatment of each fracture and/or non-union may vary. Determining factors include the location of the fracture, the degree of displacement (misaligned bone ends), and failure of prior treatment. The two main treatments for scaphoid fractures are casting and surgery, and the indications and expected results are explained in greater detail as follows:
Dr Wolfe points out, “Despite the advances of surgical treatment of scaphoid fractures, casting remains a safe, effective, and viable option for nondisplaced fractures.”
Displaced fractures or highly complicated fracture patterns usually require an operative approach to realign the fracture fragments and hold them together until healing. Fractures that have been determined to have lost blood supply may require a specialized type of surgery that employs transfer of a bone graft with a new blood supply.
As Dr. Wolfe explains, “Recent revolutionary developments in operative techniques permit a percutaneous surgical approach, which is quicker, leads to faster recovery time, and provides good – if not better – healing rates than casting or open surgical treatment, with minimal to no incision.” Percutaneous surgery enables the same degree of fracture fixation without an appreciable incision or blood loss. Still, complicated or displaced fractures of the scaphoid may not be amenable to this new approach.
Successful internal fixation of a scaphoid fracture, which has essentially healed.
Because the incision is so small, a suture is usually not required. The hand is then held in a sterile cotton dressing and a plaster splint, which extends from the wrist to the midsection of the forearm. Rehabilitation begins almost immediately after surgery. Ten days later, the dressing and splint is exchanged for a removable plastic splint. New techniques also can include the manipulation of displaced fractured fragments arthroscopically or under fluoroscopic control prior to placing the fixation screw. This sometimes enables percutaneous fixation of fractures that would have otherwise required open surgical treatment.
Despite the effective diagnostic and treatment options available today, Dr. Wolfe notes that he continues to see a high number of untreated scaphoid fractures that have progressed to nonunion. However, he adds that this may not be the result of a missed diagnosis, but rather more related to the relatively innocuous injury that causes a low level of suspicion. Recognition and awareness of scaphoid fractures is higher today among primary care providers, emergency room physicians, pediatricians, and sports trainers, but fully 15% of patients with suggestive physical findings and normal initial x-rays will have an “occult”, or concealed, scaphoid fracture. Specialized imaging studies are critical at an early stage to reduce the chance of scaphoid nonunion.
This image shows a chronic scaphoid fracture nonunion with osteoarthritic changes apparent in the adjacent joint.
When faced with a scaphoid non-union, a physician is presented with many variables, including the tenuous blood supply to the scaphoid, the possibility of malposition of other bones, and degenerative arthritis. The most difficult problems are related to the time elapsed since the injury.
Although recent diagnostic and surgical advances have revolutionized treatment for scaphoid fractures, new innovations are currently being discovered and tested. Dr. Wolfe is encouraged by the potential for surgeons to use the injection of a biologic compound into a scaphoid fracture or non-union that would enhance the rate of bone healing and minimize the need for prolonged immobilization. Application of ultrasound or electric stimulation has also shown promise in the acceleration of healing in scaphoid fractures, and some studies have concluded that bone stimulation will expedite healing in non-unions as well.
The use of biologics to accelerate healing have not entered the mainstream thus far, but there are encouraging signs that we may observe new horizons in treatment options in the years to come.
A fracture or non-union of the scaphoid bone can be a complex and troubling injury, but the medical community has seen major advances in recognizing and treating these injuries in the last decade. The advent of the percutaneous screw technique is a major step in treating scaphoid fractures and non-unions. The recently developed minimally invasive techniques in treating these injuries have made a significant impact on those who suffer these injuries, but one thing is unchanged - the earlier the recognition and treatment of scaphoid fractures, the better the overall outcome.
Summary by Mike Elvin