Avascular Necrosis of the Lunate

Last updated: Wednesday, December 30, 2009
Basics of Kienbock's disease

Kienbock’s disease is an idiopathic condition meaning there is no known cause.  The pathology results from ischemia and subsequent necrosis of the lunate one of the primary bones of the wrist.  As the lunate collapses the wrist undergoes a predictable pattern of arthritic degeneration and coinciding instability.  Patients will often complain of site-specific pain weakness and mechanical symptoms (clicking clunking subjective instability and stiffness).  Depending on the stage at presentation different modalities of treatment are available.

Immediate medical attention

The earliest symptom is pain on the mid-dorsal aspect of the wrist. It may or may not be preceded by a history of trauma.  Some authors believe it is caused by repetitive micro-trauma; however most cases are not precipitated by any identifiable injury.  Associated with the pain patients may report local swelling weakness and decreased wrist extension .  The pain will precede any findings on plain radiographs.  It may be detected earlier on MRI.  Once a diagnosis of Kienbock’s disease is made immediate referral to an orthopedic surgeon is indicated.

Anatomy

Kienbock’s is avascular necrosis of the lunate which is one of the eight bones that make up the carpus. The carpus consists of two rows of four small bones that lie directly distal to the wrist joint.  In fact the proximal row of the carpus forms part of the wrist or radiocarpal joint.  The lunate is a central bone of the radiocarpal joint. It articulates directly with the distal radius.  It has key ligamentous attachments that stabilize the rest of the carpus.  When it collapses the biomechanics of the wrist are altered in such a way that causes sequential degenerative changes throughout the radiocarpal and intercarpal joints.

Initial symptoms

Earliest symptom is central dorsal wrist pain that is aggravated by loading maneouvres such as compression in wrist extension (eg push-up position).

Symptoms

Initially patients will report central dorsal wrist pain that radiates up the forearm with associated stiffness tenderness and swelling over the lunate.

Passive dorsiflexion of middle finger may produce characteristic pain.

As the condition progresses patients will note a limitation of wrist motion (usually extension) and weakness of grip.

As the lunate collapses and degenerative changes develop the pain weakness and stiffness will increase causing severe and chronic disability.

Progression

Initially patients will report central dorsal wrist pain that radiates up the forearm with associated stiffness tenderness and swelling over the lunate.

Passive dorsiflexion of middle finger may produce characteristic pain.

As the condition progresses patients will note a limitation of wrist motion (usually extension) and weakness of grip.

As the lunate collapses and degenerative changes develop the pain weakness and stiffness will increase causing severe and chronic disability.

Secondary effects

There are no systemic effects of Kienbock’s. All the symptoms are directly related to collapse of the lunate and spread of arthritis through the carpus.

Conditions with similar symptoms

There are numerous conditions that can cause central dorsal wrist pain. These may originate from the subcutaneous tissues (tumors neuromas) extensor tendons (tenosynovitis) joint capsule (dorsal wrist ganglion) ligaments (scapholunate tears SLAC wrist SNAC wrist) and joint (arthritis).

Accurate diagnosis requires thorough history physical examination investigations follow-up and vigilance for the condition.

Prognosis

Once it is determined that the lunate has sustained a vascular insult immediate intervention is warranted. The condition follows a predictable pattern of arthritic degeneration which leads to progressive and debilitating pain with loss of function.  In the rare instance the lunate may spontaneously  revascularize before the onset of arthritis; however this should not be hoped for and treatment should not be delayed.

Lethality

The symptoms are limited to the affected wrist. There are no systemic manifestations of Kienbock’s disease and it is not fatal.

Pain

One of the earliest manifestations of Kienbock’s is mid-dorsal wrist pain. As the arthritis spreads the pain increases and becomes more diffuse.  It is aggravated by any activities that cause compression loading of the wrist particularly with extension. 

Debilitation

The pain eventually becomes debilitating as the arthritis spreads to involve the whole wrist. Patients will experience not only pain with activities but also at rest.  It will interfere with the ability to perform even sedentary work and often wakes them from sleep.  Increased dependency on analgesics is common.

Comfort

The pain eventually becomes debilitating as the arthritis spreads to involve the whole wrist. Patients will experience not only pain with activities but also at rest.  It will interfere with the ability to perform even sedentary work and often wakes them from sleep.  Increased dependency on analgesics is common.

Curability

If diagnosed early interventions can unload the lunate and potentially allow for revascularization. The choice of treatment is determined by the anatomy of the individual (ulnar variance) and the stage of disease. 

Once the arthritis becomes more widespread only salvage procedures can be attempted.  These typically involve a series of bony fusions or resections directed at ablating arthritic joints.  This alleviates the pain but also results in decreased motion and strength.

Fertility and pregnancy

Kienbock's disease will not change the patient's ability to have children or get pregnant.

Independence

The progressive and debilitating nature of Kienbocks disease often interferes with a person’s independence. The pain and loss of use of the affected extremity often affects vocation recreation and activities of daily living (personal hygiene cooking cleaning ability to dress etc.)

Mobility

Kienbock's disease will not change the patient's ability to move about.

Daily activities

The pain tends to be aggravated by activities that load the wrist. Initially this may only interfere with heavy labor or sports but as the arthritis progresses it typically will limit basic activities of daily living.  Eventually the pain will be present even with inactivity and will wake patients regularly at night.

Energy

Fatigue may result from lack of restful sleep and the stress of chronic pain. Otherwise kienbock’s does not have any systemic manifestations and will not affect a patient’s metabolism.

Diet

Kienbock's disease will not require a change in diet.

Relationships

The effects of chronic pain loss of work restrictions in recreational pursuits and loss of sleep will strain relationships both at work and home.

Other impacts

The condition is not contagious and does not spread to other joints in the body. The restrictions and limitations are associated with the loss of use of the extremity.  This may be secondary to the pain or as a consequence of surgical interventions directed at treating the pain.

Incidence

The condition tends to affect males in their third or fourth decades. It is usually limited to one wrist.  Certain individuals may be predisposed due to anatomic variations in blood supply ulnar length and lunate shape:

1. Vascular

There are various patterns of blood supply to the lunate including “X” “I” and “Y” patterns.  Between 7 and 26 percent of lunates have only one artery supplying them (“I” pattern) with 31 percent having no arterial branching within the lunate (Gelberman Bauman et al. 1980; Panagis Gelberman et al. 1983). This pattern may render the lunate more susceptible to avascular necrosis as injury to the single vessel cannot be compensated by collateral flow.

2. Load distribution

a. Ulnar Variance
The length of the distal ulna with respect to the distal radius in the AP plane is called ulnar variance. A shorter ulna or negative ulnar variance may lead to increased load across the radiolunate articulation with increased risk of lunate avascular necrosis. This relationship has been shown in some studies; others have found no such correlation and since Kienböck’s disease occurs in individuals with neutral and even positive ulnar variance other factors must be involved as well.(Gelberman Salamon et al. 1975; Chen and Shih 1990; Coe and Trumble 1993; Weiss 1994)

b. Lunate Shape
The geometry of the lunate itself and of surrounding bones may also be significant.

One investigator noted a tendency toward a smaller lunate in his patients with the disorder.(Tsuge and Nakamura 1993) Three different patterns of lunate morphology at the articulation with the scaphoid radius and triquetrum have been described along with findings that the vascular foramina tended to occur in proximal triangular areas of the bone such that some lunate specimens are less well vascularized than others.

Acquisition

Kienbock’s is idiopathic meaning there is no known etiology.  However as previously discussed it likely results from both being predisposed (triangular lunate negative ulnar variance “I” pattern artery) as well as being exposed to environmental influences (repetitive trauma). 

No single factor has been attributable to causing Kienbock’s disease.

Genetics

There is no familial pattern of inheritance for Kienbock’s disease.

Communicability

Kienbock's disease is not contagious.

Lifestyle risk factors

Exposure to repetitive trauma is a risk factor. Activities that involve compression loading of the wrist particularly in extension (eg jackhammers) have been postulated to cause vascular injury.

Other generic risk factors for avascular necrosis include history of steroid use sickle cell anemia exposure to increased barometric pressure (eg diving) and smoking.  These risk factors are not particular to Kienbock’s and have been documented more commonly in the hip knee and shoulder.

Injury & trauma risk factors

Trauma is the most common postulated etiology for Kienbock’s. This can take the form of a single traumatic episode such as a fracture dislocation of the wrist from a car accident or it may include repetitive microtrauma such as compression loading from using a jackhammer.
Prevention There is no prophylaxis against Kienbock’s since you cannot identify individuals at risk. Manual jackhammers have largely been replaced with hydraulic ones. Other than this intervention in the workplace there are no guidelines for primary prophylaxis against Kienbock’s.