Avascular Necrosis of the Lunate (Kienbock’s Disease)

Kienbock’s Disease occurs when a wrist bone named the lunate loses its blood supply. Without blood supply, the lunate eventually fragments and collapses. Degenerative changes then occur throughout the wrist. Kienbock’s was previously classified into 4 stages based just on regular x-rays. Because this defunct system fails to include the two most important evaluations of lunate status, it is not useful in patient care, as explained in our extensively peer-reviewed 2021 article.

Henry MH, Lundy FH, Henry GK. Matching Kienbock’s Treatment Options to Specific Features of Each Case. Journal of Hand and Microsurgery 2021; 13: (In Press).

It is difficult, if not impossible, for a surgeon to care for a patient unless he is confident in his ability to execute all of the possible treatment options.

Henry MH. Double bundle tendon graft for rotational stabilization of lunate implant arthroplasty. Techniques in Hand and Upper Extremity Surgery 2011; 15:16-23.

Kienbock’s is best understood as occurring in three phases: early, transitional, and late. The existing published literature provides evidence to support spontaneous revascularization of the lunate in adolescent patients, but not in adults.  Progression through the transitional phase typically takes only a matter of months.  So, once the diagnosis is established, patients usually educate themselves promptly and then choose their preferred treatment. 

Henry MH. Outcomes Assessment of Lunate Replacement Arthroplasty with Intrinsic Carpal Ligament Reconstruction in Kienböck’s disease. . HAND 2014; 9(1):1-8. 9(3): 364-369. 10.1007/s11552-014-9624-z

CLINICAL EVALUATION

Unfortunately, patients may not initially have many symptoms initially, which makes it hard to catch the problem early. Eventually, the wrist becomes painful, weak, swollen, and loses motion.

ADDITIONAL TESTS

Regular x-rays can demonstrate some of the changes seen in Kienbock’s but cannot answer the most important questions. MRI scans demonstrate vascular supply in wrist bones and are useful in confirming that the reason for symptoms is indeed Kienbock’s, not something else. Unfortunately, many physicians are confused about the role of MRI and incorrectly think it has something to do with treatment selection; it does not. The medical test that guides selection of one treatment over another is a CT scan that demonstrates bone structure in three dimensions. It is the CT scan that identifies early, transitional, or late phases of the degenerative process and reveals which treatments can even be considered. Final check points must then be verified during surgery before actually proceeding with specific treatments. This is why it is impossible to plan treatment for a Kienbock’s patient just looking at regular x-rays and a MRI scan, unable to understand the critical findings that actually determine treatment.

TREATMENT OPTIONS – EARLY

In early Kienbock’s, the lunate has lost its blood supply but remains structurally intact on CT scan and confirmed at surgery. The treatment requirement is to provide a source of new blood supply to revascularize the lunate and decompress the excess pressure considered to have stopped the blood flow in the first place. This is accomplished by drilling a tunnel through the lunate into which a new source of blood supply is directly inserted.

Unfortunately, much incorrect information has historically circulated about Kienbock’s that has led doctors to pursue unjustifiable treatments. One widely disseminated misconception is that Kienbock’s is caused by having one of the forearm bones, ulna, shorter than the other forearm bone, radius. Current published analyses do not support this flawed theory. More unfortunate is that a highly invasive treatment was based on this incorrect concept, radial shortening osteotomy. One of the forearm bones (radius) is cut in half with a power saw, a section taken out, and then fixed back to itself with a long metal plate and screws. Modern research has demonstrated that the ultimate result is not better than just doing nothing and allowing the lunate to keep collapsing. But, changing the length or angle of the radius also changes the contact of the forearm rotational joint that can promote arthritis, introducing a whole new problem.

TREATMENT OPTIONS – TRANSITIONAL

In transitional Kienbock’s, the structure has started to collapse, but as long as one or both cartilage surfaces remain intact, the bone can still be reconstructed by transferring vascularized bone and cartilage using microsurgery techniques. The lunate is compressed between two bones: the capitate (another wrist bone closer to the fingertips at the joint surface called distal) and the radius (the larger forearm bone of top of which all the wrist bones sit at the joint surface called proximal). In order for the joint cartilage that lives on the surface of all bones that rub against each other to survive, the cartilage must have a viable layer of bone support. If the bone supporting the cartilage layer becomes unsalvageable (terminally necrotic), then that particular joint surface (distal or proximal) cannot be saved. If neither joint surface can be saved, then the entire lunate cannot be saved.

As the patient heads into the transitional phase, first the core of the lunate degrades but both joint surfaces appear to have adequate bone support on CT scan, but the quality of this bone support must be confirmed at surgery (the CT scan alone can only prove that a joint surface does not have adequate support). Reconstruction of the core is by a vascularized flap of bone from the nearby radius carried on a leash of blood vessels directly supplying to the lunate.

As degradation progresses, the proximal joint surface facing the radius will be next to collapse. If the distal surface facing the capitate is still supported by bone (suggested by CT and confirmed at the time of surgery) then an entirely new proximal cartilage surface, supported by bone and direct blood vessels, can be imported from the knee joint (medial femoral trochlea flap = MFT). Because either of these complex reconstructive options requires a final confirmation of the bone quality at the time of surgery, the patient must always select an alternate operation to be performed right then and there. A core bone radius flap can transition into a MFT flap. If the distal bone proves incapable of receiving and bonding with a MFT flap, then the patient must select from the options for late phase Kienbock’s.

TREATMENT OPTIONS – LATE

In late Kienbock’s the structure of the lunate has already collapsed beyond the capacity for reconstruction, and treatment options aim to create a new design for wrist function after removing the dead and fragmented lunate bone.

The most common operation performed for late Kienbock’s is called proximal row carpectomy (PRC). In addition to removing the fragmented lunate, the two normal bones on either side of it are also removed to simplify the design of how the wrist joint operates. Because the wrist joint is a naturally unstable joint, just taking out only the lunate does not work as the two most important stabilizer ligaments attach to the missing lunate. Although PRC is favored by surgeons because it is easy to perform and does not require any special skills, it has a critical problem in that all the force across the wrist occurs at one small point of contact between the capitate and radius. With the passage of time, the cartilage wears down at this interface; some patients find it so painful that they go back to surgery and get a complete fusion of the wrist. If there is already any existing damage to the cartilage on the capitate or radius from grinding against the fragments of the lunate, then the PRC will burn out even sooner.

The teaching in wrist surgery is that if there is already cartilage damage, a PRC should not be performed. To overcome this prohibition, a polished metal alloy prosthesis was developed to provide a smooth surface for the capitate bone. This Cobalt-Chrome prosthesis comes in various sizes that can be matched to fit the curvature of the opposing radius so the forces spread out more. Further research is needed to determine the outcomes achieved by this newer device.

While PRC is the simplest operation for Kienbock’s, the most complex operation is replacing the lunate with a prosthetic replica made out of a special material called pyrocarbon. The reason this is the most complex operation we have for Kienbock’s (more complex than the MFT flap) is that the other normal bones are not taken out of the wrist. Because all the other bones remain, the wrist is completely unstable until the surgeon creates a complex series of new connections between 3 different bones using two different grafts going in opposite directions. The pyrocarbon material has the favorable properties of density similar to bone and incredibly low friction as a joint surface, but very unfavorable in that nothing will bond or heal to that low friction surface. So, the surgeon has no way to directly control the position of the prosthesis that can tilt forwards or backwards or slide to the side. The final position of the prosthesis and the overall stability of the wrist depend on the complex series of new connections created that have to bypass the lunate, compared to the original wrist ligaments that connected directly to the lunate.

Other treatments that are possible for late phase Kienbock’s include partial and total wrist fusions. Literature on partial wrist fusion (just like radial shortening osteotomy) indicates that it is no better than just letting the lunate degenerate naturally as well as worse outcomes compared to other options – for those reasons we do not offer partial wrist fusion in this Kienbock’s specialty practice. We do offer total wrist fusion. When conducting face-to-face patient education, we present total wrist fusion as the first option for late Kienbock’s because it is a very predictable surgery with the best pain relief, the most durability, able to withstand any amount of abuse, and likely the last wrist surgery the patient will ever have. Despite all of those advantages over the other options, we have not seen a single patient ever select total fusion as a first option simply because it takes away all motion in the wrist.


RECOVERY

The steps taken in recovery depend in part on 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 pyrocarbon replacement or MFT flap. 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 onward towards six months using a home based program. For any option other than a total wrist fusion, patients must consider future lifestyle choices that do not abuse the wrist joint if they want to get the best and most durable result from the chosen treatment.

Houston Hand and Wrist