Kienböck disease, or osteonecrosis of the lunate, can lead to
debilitating wrist pain with complete disruption of the radiocarpal
and carpal joints. It occurs most frequently between the ages of 20
and 40 and more commonly afflicts the right hand. The etiologic
factors have been debated and include a single episode of trauma
vs. repetitive, minor trauma, ischemic events vs. venous
congestion, and mechanical forces caused by negative ulnar variance.
Ulnar length is thought to influence the manner in which stresses
are transmitted across the wrist. Normally, the articulation of the
ulna and radius with the lunate is in a neutral variance. When the
ulnar articular surface projects proximal to the radius, negative
ulnar variance exists. Mechanical forces acting on the wrist joint
may be accentuated by the presence of a short ulna, a finding seen
in up to 75% of Kienböck disease cases. However, Kienböck disease
is rare and negative ulnar variance is not infrequent, which
illustrates the fact that other important causative factors play a
role.
Early diagnosis of Kienböck disease is crucial in preventing the
end-stage degenerative wrist. The goal of surgical treatment is the
relief of pain and the preservation of wrist range of motion.
Attempts at revascularization of the lunate prior to its’ collapse
are achieved directly with vascularized bone grafting or indirectly
by unloading the lunate. Radial shortening and ulnar lengthening
procedures in patients with negative ulnar variance have been
successful. In the later stages of the disease, the treatment
addresses the carpal collapse. Surgical options include
scaphotrapeziotrapezoid arthrodesis, capitohamate arthrodesis,
scaphocapitate arthrodesis, and proximal row carpectomy. Despite
the large number of procedures available for the treatment of
Kienböck disease, no single method has emerged as being clearly
superior.
Radiologic Overview of the Diagnosis:
Radiographic changes seen in Kienböck disease are distinctive and
follow a progressive sequence of events. In stage I, plain films
are normal. The diagnosis requires CT, MR, or bone scintigraphy. A
subtle fracture seen on CT or decreased signal intensity of the
lunate on T1WI MR are the earliest findings of the disease. In
stage II, plain films demonstrate sclerosis of the lunate and/or
flattening of its’ radial border. In stage III, the lunate
collapses and proximal capitate migration occurs. This results in a
disruption of the carpal bone architecture and often, ligamentous
instability. In stage IV, there is almost complete degeneration of
the lunate and secondary degenerative joint disease in the
radiocarpal and midcarpal compartments. This includes joint space
narrowing, sclerosis, osteophytosis, and subchondral cyst formation.
Diagnosing Kienböck disease is not, in itself, sufficient from
the orthopedic prospective. It is essential for the radiologist to
demonstrate the integrity of the lunate in order to facilitate
treatment planning.
Key Points:
- Kienböck disease is a sequence of events that occur as a
result of osteonecrosis of the lunate.
- A high index of suspicion is required to diagnose early
Kienböck disease and may require CT, MR, or bone scintigraphy.
- Early diagnosis is essential in preventing end-stage
osteoarthritis of the wrist.
- Management of Kienböck disease often requires surgical
treatment
