WHAT YOU SHOULD KNOW
Kienbock’s disease occurs when one of the wrist bones named the lunate spontaneously loses its blood supply. A recent trauma may have occurred that plays some role in the lunate becoming avascular (without blood supply). Without a blood supply, the lunate bone dies (avascular necrosis = AVN) and then eventually collapses. Once the lunate collapses the whole wrist then develops arthritis. This progressive degeneration has been separated into stages I-IV with stage IV representing wrist arthritis. Stage III is where the lunate begins to collapse and is broken down into stage IIIA (just starting to collapse) and stage IIIB (collapsed enough that it affects the position of other wrist bones). The key to a better outcome is to catch the progression early enough to save the lunate (stage IIIA or before). Reasonable options still exist for stage IIIB and stage IV, but require substantial change to the wrist anatomy.
Unfortunately, patients may not have many symptoms in the earlier stages, which makes it hard to catch the problem near the beginning. Eventually, the first symptoms are pain and limited wrist motion. As the problem worsens, patients experience weakness of grip and the inability to perform heavier or more complex tasks.
In earlier stages, the only sign on physical examination may be localized tenderness in the wrist. Loss of wrist motion can be measured. Eventually, the wrist will exhibit actual tissue swelling that can be palpated and visualized. Grip strength tested on the affected side will usually be less than the normal side.
A digital high resolution x-ray taken in the office can demonstrate the typical changes seen in avascular necrosis of the lunate through the various stages, including determining if the other wrist bones are collapsing as the patient goes from stage IIIA to stage IIIB. In early stages, if there is a question of whether the patient truly has Kienbock’s or not, a MRI scan is very accurate in demonstrating the pattern of avascular necrosis. In later stages, if there is a question of whether the lunate has fragmented or not, a CT scan is very accurate in demonstrating the number and sizes of the lunate fragments. This can determine the suitability of different reconstructions.
Early stages of Kienbock’s are managed by supportive measures to include activity modification, oral anti-inflammatory medications, and wrist injection with a cortisone type solution. Since most Kienbock’s progresses through the stages towards an ever worsening result, surgery is usually chosen by the patient not long after the condition is confirmed. The appropriate surgery is largely determined by the stage of the condition.
||PROXIMAL ROW CARPECTOMY
||Providing a direct new blood supply and bone material to the lunate from the nearby distal radius bone
||Removing the lunate as well as the normal bones on either side of it completely
||Replaces just the lunate bone with a prosthetic replica and stabilizing the adjacent ligaments
||Surgically fusing together all the wrist bones
||Best treatment for stages I-IIIA, can still be used in select cases of stage IIIB
||The new site for motion of the wrist is between the capitate bone and the radius bone
||The prosthesis that replaces the lunate with the correct size and shape is made of a special pyrolytic carbon material that is very smooth as well as durable
||A large plate connects the metacarpal bone of the hand through the wrist bones to the radius bone with screws
||Saves the lunate and maintains normal wrist anatomy
||Simple to perform for the surgeon
||Preserves the normal anatomy of all the other bones; implanted material is very durable
||Once fused the result is durable for the patient’s lifetime
||Once the lunate has crumbled too much, the procedure is not capable of being used
||The two new bones that rub together do not match and arthritis develops where they make contact
||The long term results of this treatment are not known since it is a relatively new treatment at this location in the body
||Sacrifices all wrist motion entirely; scarring around the extensor tendons to the hand
The steps taken in recovery depend in part of which reconstruction has been performed. In general, the first phase will consist of immobilization in a splint / cast until the new tissue connections have healed. This may range from 3 weeks for a proximal row carpectomy up to 8 weeks for an implant arthroplasty. Once the reconstruction has healed, wrist motion is begun under the guidance of a hand therapist. At this intermediate stage, the priority is placed on regaining motion. Once the motion program is solidly underway at several months following surgery, strength training is added. For these types of major wrist surgery, patients will continue to progress in rehabilitation onwards towards six months using a home based program.