Avascular Necrosis of the Scaphoid
- Avascular necrosis of the scaphoid also known as scaphoid necrosis or Kienbock’s disease, is a condition where the blood supply to the scaphoid bone in the wrist is compromised, leading to bone death.
- Avascular necrosis of the scaphoid is a common sequela to scaphoid fracture. Second only to the hip in the incidence of avascular necrosis, the scaphoid is extremely susceptible to this disease because of the tenuous blood supply of the scaphoid, which enters the bone through its distal half.
- The dorsal blood supply and the volar blood supply are easily disrupted by fracture of the scaphoid, often leaving the proximal portion of the bone without nutrition, leading to osteonecrosis.
What causes Avascular Necrosis of the Scaphoid?
The exact cause of avascular necrosis of the scaphoid is not always clear, but several factors and conditions may contribute to its development:
- Injury: A wrist injury, such as a fracture or a dislocation, can disrupt the blood supply to the scaphoid, increasing the risk of avascular necrosis.
- Repetitive Stress: Chronic repetitive stress on the wrist, as seen in certain occupations or sports that involve repetitive use of the wrist, may lead to reduced blood flow and subsequent scaphoid necrosis.
- Vascular Insufficiency: Conditions that affect blood flow to the wrist, such as arterial disease or thrombosis (blood clot), can lead to avascular necrosis of the scaphoid.
- Idiopathic: In some cases, the cause of scaphoid necrosis remains unknown, and it is considered idiopathic.
- Anatomical Variations: Certain anatomical variations in the blood supply to the scaphoid can make it more susceptible to avascular necrosis.
- Bone Diseases: Certain bone-related conditions, such as osteoporosis or osteonecrosis, can increase the risk of avascular necrosis in various bones, including the scaphoid.
- Systemic Conditions: Certain systemic diseases, such as sickle cell disease or systemic lupus erythematosus, can predispose individuals to avascular necrosis in various bones, including the scaphoid.
- Steroid Use: Prolonged use of high-dose steroids can disrupt the blood supply to bones and increase the risk of avascular necrosis.
- Common causes of scaphoid fracture include trauma to the scaphoid from falls on a hyperextended wrist and from steering wheel injuries during motor vehicle accidents, although an idiopathic form of the disease, known as Preiser disease, can occur.
- A patient with avascular necrosis of the scaphoid reports unilateral wrist pain over the anatomical snuffbox that may radiate into the radial aspect of the forearm and decreasing range of motion of the wrist. Weakened grip strength also may be noticed. Movement of the thumb usually exacerbates the patient’s pain.
What are the Symptoms of Avascular Necrosis of the Scaphoid
Physical examination of patients reports avascular necrosis of the scaphoid reveals pain on palpation of the anatomical snuffbox.
The pain can be worsened by passively moving the wrist from ulnar to radial position or by moving the thumb of the affected side. A click or crepitus also may be appreciated by the examiner when putting the wrist through range of motion. Weakness of dorsiflexion is common, as is weakness of grip strength in contrast to the nonaffected side.
How is Avascular Necrosis of the Scaphoid diagnosed?
Plain radiographs are indicated in all patients who present with avascular necrosis of the scaphoid to rule out underlying occult bony pathological conditions and identify sclerosis and fragmentation of the scaphoid, although early in the course of the disease plain radiographs can be notoriously unreliable.
Based on the patient’s clinical presentation, additional tests, including complete blood cell count, uric acid level, erythrocyte sedimentation rate, and antinuclear antibody testing, also may be indicated.
Computed tomography (CT) and magnetic resonance imaging (MRI) of the wrist are indicated in all patients thought to have avascular necrosis of the scaphoid or if other causes of joint instability, infection, or tumor are suspected.
Administration of gadolinium followed by postcontrast imaging may help delineate the adequacy of blood supply, with contrast enhancement of the proximal scaphoid being a good prognostic sign. Ultrasound imaging of the scaphoid also may aid in the diagnosis. Electromyography is indicated if coexistent ulnar or carpal tunnel syndrome is suspected. A very gentle injection of the radial aspect of the distal radioulnar joint with small volumes of local anesthetic and steroid provides immediate improvement of the pain, but ultimately surgical repair is required.
Coexistent arthritis and gout of the radioulnar, carpometacarpal, and interphalangeal joints; dorsal wrist ganglion; and tendinitis may coexist with avascular necrosis of the scaphoid and exacerbate the patient’s pain and disability.
Distal fractures of the radius, de Quervain stenosis, tenosynovitis, scapholunate ligament tears, scaphoid cysts, contusions, and fractures also may mimic the pain of avascular necrosis of the scaphoid, as can tear of the triangular fibrocartilage complex.
Initial treatment of the pain and functional disability associated with avascular necrosis of the scaphoid should include a combination of nonsteroidal antiinflammatory drugs (NSAIDs) or cyclooxygenase-2 (COX-2) inhibitors and short-term immobilization of the wrist. Local application of heat and cold also may be beneficial.
For patients who do not respond to these treatment modalities, an injection of a local anesthetic and steroid into the radial aspect of the distal radioulnar joint may be a reasonable next step to provide palliation of acute pain. Vigorous exercises should be avoided because they would exacerbate the patient’s symptoms. Ultimately, surgical repair is the treatment of choice.
Failure to treat significant avascular necrosis of the scaphoid surgically usually results in continued pain and disability and in some patients leads to ongoing damage to the wrist. Injection of the joint with local anesthetic and steroid is a safe technique if the clinician is attentive to detail, specifically using small amounts of local anesthetic and steroid and avoiding high injection pressures, which may damage the joint further.
Another complication of this injection technique is infection. This complication should be exceedingly rare if strict aseptic technique is followed. Approximately 25% of patients report a transient increase in pain after this injection technique, and patients should be warned of this possibility.