KIENBOCK DISEASE

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KIENBOCK DISEASE

Post by Admin on Sat Jan 22 2011, 18:37

Kienböck disease is a condition of uncertain etiology that results in osteonecrosis of the carpal lunate.Kienböck disease usually affects the dominant wrist of men aged 20-40 years.
Etiology
Although the underlying etiology is not known, the final results of fragmentation and collapse are secondary to osteonecrosis. Intrinsic and extrinsic factors have been implicated.
Pathophysiology
Force transmission studies have formed an important part of the understanding of the pathophysiology of Kienböck disease. In the normal wrist in neutral alignment, 80% of the axial load through the wrist is transmitted through the radiocarpal joint, while the remaining 20% goes through the ulnocarpal joint. Two-dimensional theoretical models of force transmission in patients with Kienböck disease have demonstrated that in the early stages of the disease (II and IIIa), the normally positioned scaphoid prevents excessive forces on the lunate. However, as the scaphoid assumes its flexed position in stage IIIB, loads across the lunate are increased. These excessive loads may further accelerate the process of fracture and fragmentation leading to collapse.
Presentation
The most common patient with Kienböck disease is a man aged 20-40 years who is either a manual laborer or one who participates in recreational activities that repetitively load the wrist. Patients present with reports of activity-related dorsal wrist pain, decreased wrist motion in the flexion-extension arc, and poor grip strength. The symptoms tend to occur more often in the dominant hand. Dorsal wrist swelling and tenderness are frequently present over the radiocarpal joint. A history of trauma is variable and may be in the distant past. Women had roughly equivalent involvement of the dominant and nondominant sides, and they tended to present at a much older age (46 years versus 31 years for men).
Imaging Studies
• Plain radiographs
o Plain films form the basis for staging and treatment of Kienböck disease. Lichtman's modification of Stahl's classification is most widely used and divides the disease into 5 stages, as follows:
 Stage I - Normal radiograph
 Stage II - Increased radiodensity of lunate with possible decrease of lunate height on radial side only
 Stage IIIa - Lunate collapse, no scaphoid rotation
 Stage IIIb - Lunate collapse, fixed scaphoid rotation
 Stage IV - Degenerative changes around the lunate
• Tomograms
o Tomograms may be useful in determining the true extent of disease.
• MRI
o MRI is most helpful early in the course of the disease when plain films are not diagnostic.
Treatment
Medical Therapy
The primary methods of nonoperative treatment are immobilization and anti-inflammatory medications. As noted previously, the natural history of Kienböck disease is not well determined. Therefore, treatment is primarily directed by the level of symptoms. Certainly, a very young patient, although an unusual presentation of Kienböck disease, should be given an adequate trial of immobilization in hopes of allowing revascularization of the lunate and preventing disease progression.
Surgical Therapy
A number of options are available for surgical management of Kienböck disease. The 2 most important pieces of information are the stage of the disease and the presence or absence of ulnar variance.
Operative treatment can be classified broadly into 6 categories, as follows:
• Lunate excision with or without replacement
• Joint-leveling procedures
• Intercarpal fusions
• Revascularization
• Salvage procedures
A reasonable approach to determining the surgical treatment of Kienböck disease based on stage is as follows:
• Stage 0, I, II, or IIIa with ulnar-negative variance – Radial shortening, revascularization, denervation
• Stage 0, I, II, or IIIa with ulnar-neutral or positive variance – Revascularization, coracohumeral (CH) fusion with capitate shortening, distal radius wedge osteotomy, denervation
• Stage IIIb – SC fusion, radial shortening, denervation
• Stage IV – PRC, total wrist arthrodesis, denervation

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