Kienbock’s Disease Investigations
The basic diagnosis of Kienbock’s Disease can be done on plain X-ray of the wrist. But due to lack of obvious findings, and the obscured view of the lunate bone on a wrist x-ray (Picture 1), only an expert orthopedist can identify this disease. There is always reason to doubt the judgment of a primary care physician in this regard. Therefore, in order to eliminate the risk of not identifying this disease, many physicians prefer to use higher investigations like CT Scan and MRI. Also, one should note the fact that, even though CT scan is cheaper than MRI, it diagnoses this disease better and is also used for staging.
Picture 1: Wrist X-ray with Lunate (inside box)
(Source: Wikimedia Commons)
Importance of Investigations
Treatment options for Kienbock’s disease are mostly a path of no return. Interventions mostly involve complex surgeries, trying to save the dying bone at any cost. Some of the surgeries assume that the bone is dead, and involve removal of the lunate and stabilization of the rest of the wrist bones to prevent collapse of the wrist. Hence, it is highly important to double check that Kienbock’s disease, is the actual cause of the wrist pain. This is done by performing additional investigations like bone scan and MRI, which rule out other musculo-skeletal causes of wrist pain.
Staging of Kienbock’s Disease
CT scan has also helped in staging of the disease, by documenting minute changes, which were missed earlier or not visible on x-ray. There are 4 stages of Kienbock’s disease:
- Stage 1 : Wrist pain without visible changes (on CT scan).
- Stage 2 : Sclerosis of lunate, where the lunate bone has lost its blood supply and so has white patches of dead portions.
- Stage 3 : Death of entire lunate bone, is when it appears completely white (on CT scan).
- Stage 4 : Collapse of the wrist, due to unbalanced forces acting on the other wrist bones.
Wrist arthritis ensues shortly after the 4th stage, to make the entire wrist stiff and painful with even small movements.
Apart from the changes taking place in lunate bone, there is a finding which have been consistently observed in patients of Kienbock’s disease. This is called negative ulnar variance, in which a person has a relatively short ulna bone compared to the radius bone of the forearm.
Picture 2: Forces across normal wrist
(Source: Wikimedia Commons)
Picture 3: Forces in Negative Ulnar Variance
(Source: Wikimedia Commons)
Thus, the forces transmitted across the wrist are concentrated on the lunate bone (Picture 2 and 3), making it susceptible to collapse. However, whether this helps in initiation of the disease or propagation of the disease after lunate looses its blood supply is yet an unanswered question !
