Kienböck’s disease is a condition that causes the breakdown of the lunate, a small, crescent-shaped bone in the wrist. The lunate is one of the eight small carpal (wrist) bones. When blood supply to the lunate is limited, a condition known as Kienböck’s disease develops. A lack of blood to the bone can cause bone deterioration. Over time, the bone will lose its structural support, and it will collapse, causing a painful, stiff wrist. Eventually, these changes can lead to arthritis of the surrounding bones in the wrist, and ultimately, to the death of the bone (osteonecrosis).
What Causes Kienböck’s Disease?
While a lack of blood supply to the lunate is a constant, the true cause of Kienböck’s disease is not fully understood. Some believe this condition may occur due to a trauma to the blood vessels that supply the lunate .However, not all patients with Kienböck’s disease can tie their condition to a specific injury.
Some patients with the disease may have fewer blood vessels that supply the lunate; most people have two arteries that supply blood to the lunate, but in some patients there is only one.
Forces acting on the lunate may be different depending on the relative lengths of the radius and the ulna bones in the forearm. If the radius and ulna are different lengths, extra pressure can be put on the lunate during some wrist motions and when pressure is applied to the wrist during activity, such as when doing a push-up. Over time, this extra pressure may compromise the blood flow to the lunate.
How is it Diagnosed?
Kienböck's disease is a condition that progresses slowly, often over many months or years. Many patients do not seek medical help until they have lived with symptoms for months or even years. The disease may present with any of the following symptoms:
Decreased grip strength
Tenderness directly over the lunate bone
Difficulty turning the palm up
Kienböck’s disease may be diagnosed through a combinate of X-rays, magnetic resonance imaging (MRI), and computed tomography (CT) scan. Imaging will show Dr. Donnelly if there is hardening of the lunate, cystic growths, or disintegration of the bone, all symptoms that may suggest bone death.
The Four Stages of Kienböck's Disease
In stage one, the symptoms of Kienböck’s disease are similar to those of a wrist sprain. Although the blood supply to the lunate has been disrupted, X-rays may still appear normal or suggest a possible fracture. An MRI scan can better detect the effects of abnormal blood flow and is helpful in making the diagnosis in this early stage.
In stage two, the lunate begins to harden due to the disrupted blood supply. This hardening process is called sclerosis and is an abnormal increase in bone density. The lunate will appear brighter or whiter in areas on X-rays, which indicates where the bone has become more dense.
To better assess the condition of the lunate, Dr. Donnelly may order either an MRI scan or a computed tomography (CT) scan. The most common symptoms during this stage include wrist swelling and intermittent pain, particularly when force is applied to the wrist, such as with weightbearing.
In stage three, the dead lunate bone begins to collapse and break into pieces. As the bone begins to collapse, the surrounding bones become affected and may begin to shift position.
During this stage, this wrist instability may cause patients to experience increasing pain in the wrist, weakness in gripping, and limited wrist motion.
In stage four, the collapse of the lunate and shifting of the other wrist bones often result in arthritis of the wrist. As with stage three, patients typically experience increased wrist pain, a loss of grip strength, and limited wrist motion.
If you are diagnosed with Kienböck's disease, Dr. Donnelly will plan your treatment based on several factors, most important, the stage of your progression.
There is no cure for Kienböck’s disease. However, when the disease is detected and treated early, immobilization with a cast and anti-inflammatory medications can be used to decrease or eliminate symptoms. Dr. Donnelly will monitor any changes in your symptoms during the early stage of the disease. If the pain is not relieved with simple treatments or it returns, he may recommend surgery.
When diagnosed early, before the lunate has collapsed or fragmented, Dr. Donnelly may be able to restore the blood supply to the lunate bone through a procedure is called revascularization. When the disease reaches its final stages or produces severe symptoms, Dr. Donnelly can discuss further surgical options - including joint leveling, a proximal row carpectomy, or a fusion of the surrounding bones.