Kienbock's Disease

Synonyms: lunatomalacia.

Kienbock's disease involves collapse of the lunate bone in the wrist and is caused by vascular insufficiency and avascular necrosis of the lunate. It is usually unilateral. This was first described by Robert Kienbock in 1910.

The avascular necrosis is caused by disruption of blood supply to the lunate.¹ This may be caused by:

• Single or repetitive microfractures
• Recurrent compression of the lunate between capitate and distal radius (this disrupts interosseous blood supply)
• Extreme wrist positions or repetitive compression loading of the wrist

Gymnasts may be at risk. Use of agents such as corticosteroids or systemic disease such as osteoporosis could in theory predispose to Kienbock's disease but a study of bilateral disease did not find such risk factors.²

It occurs most often in young adults between 15 and 40 years of age.

History:

• Difficult to diagnose in the early stages when symptoms are similar to wrist sprain
• It presents as wrist pain with pain and tenderness over the lunate
• The pain may radiate up the wrist and forearm
• There is associated stiffness at the wrist
• There may be a history of a single injury or repetitive injury/ compression loading

On examination:

• There may be associated swelling over the lunate
• Passive dorsiflexion of the middle finger produces the characteristic pain
• There may be limitation of wrist dorsiflexion, but can also limit wrist extension
• There is often a weakened grip

Symptoms are progressive and chronic as the lunate bone progressively collapses and degenerative changes occur.

Wrist sprains and any cause of arthritis in the wrist joint may give similar symptoms.

• Wrist X-ray:
  • Initially may be normal or sclerosis of the lunate
  • May show ulnar variance (see below)
  • Lunate shows progressive loss of height and fragmentation
  • Lunate collapse causes further degenerative joint changes (because of carpal instability) with bone cysts within the lunate
  • Eventually degenerative changes may involve the whole wrist
  Ulnar variance has been held as important in the aetiology and treatment of Kienbock's disease but meta-analysis reveals that there is insufficient evidence to support this hypothesis.³
  • Measurement of ulnar variance^4,5 requires a zero rotation view on a PA radiograph of the wrist in neutral pronation/supination. This measurement is mentioned a lot in relation to wrist disease. It is not simple to measure accurately⁵ and meaningfully and this has perhaps confused research results on the significance of ulnar variance in disease.
  • Negative ulnar variance (26% of patients) is often associated with Kienbock's disease^6,7 (although the association is contested^8,9,10).
• MRI and CT scans are also frequently helpful in assessing the disease (staging of the disease) and planning treatment.
• Wrist arthroscopy can also be important in evaluating wrist pain.¹¹

Osteoarthritis

There are 2 classifications of Kienbock's disease:

• Stahl's classification (stages 1 to 5, from normal with evidence of lunate compression to 5 with osteoarthrosis of radial carpal and inner- carpal joints)
• Lichtman's classification (Stages 1 to 4)

A simplified version is:

• Stage 1. Symptoms similar to wrist sprain. Normal X-rays or line indicating possible fracture. MRI may be useful to confirm diagnosis.
• Stage 2. Symptoms of recurrent pain and swelling. The lunate bone becomes hard/ sclerotic and X-ray show this sclerosis (indicating the bone is infarcting). CT scans and MRI may be useful to assess condition of the lunate bone.
• Stage 3. Increasing pain, weakened grip and limited wrist movement occur. The infarcted bone collapses and breaks up causing a shift in position of surrounding bones.
• Stage 4. Disruption of surrounding bones causes arthritis of the wrist.

Early disease

The aim is to reduce compressive loading of the lunate, permitting revascularisation and preventing lunate collapse. In early disease this may be aided by splinting and anti-inflammatories. Referral to an orthopaedic or hand surgeon is recommended. The aim of reducing lunate loading and allowing revascularisation may require surgery:

• Establishing a negative ulnar variance (unloading the lunate fossa and distributing load to the scaphoid fossa) by:
  • Radial shortening
  • Ulnar lengthening
  • Fusion of the capitate and hamate
  • Scaphotrapeziotrapezoid (STT) joint fusion (up to stage 3)
• Vascular bundle implantation
• Establish neutral ulnar variance by radial wedge osteotomy

Late disease

These are for more advanced disease and used less often:

• Wrist arthrodesis. This may be necessary when severe degenerative changes are present and when the hands used for heavy labour.
• Proximal row carpectomy. This may not work with Kienbock's disease because of damage to the articular surfaces of capitate and radius.

Stiffness and progressive loss of wrist function are well described sequelae of the condition. Grip strength deteriorates by 40% between stages 2 and 4 of the disease.

If left untreated it is a progressive disease passing through the various stages described by Lichtman. However it is picked up as an incidental finding on X-rays and it does not always cause pain or interfere with activities of daily living.¹²

Awareness of this condition can prompt earlier diagnosis and corrective measures to prevent progression of the disease.¹³ However it should be remembered that symptoms can be mild for many years with no treatment.¹²