"Metallosis" and ICD-10 | Blog

"Metallosis" and ICD-10

“Metallosis" is a condition occurring in Orthopedic Surgery which is the result of “Metal-On-Metal” (MOM) hip joint prostheses. To my knowledge there are no other Metal-On-Metal prostheses implanted in humans other than in the hip. In the thinking of Orthopedic Surgeons, this is not a “Metal Allergy,” but is more of a local and possibly systemic “Metal Toxicity” reaction. The local reaction around the prosthesis is basically an inflammatory Foreign Body Reaction to the micro-particles of metallic debris resulting from the metal femoral head rubbing and wearing against the metal acetabular socket. Unfortunately, and in spite of the best efforts of all the contributing scientists, the problem of “Friction” between the articulating prosthetic parts has never been totally resolved. It is the friction from the metal components rubbing on each other that creates this microscopic metal debris. This is shed from the joint and picked up by the synovium. The human body does not like having foreign material within itself, and reacts accordingly by using whatever methods the human body is capable of doing. Ideally, the human body would prefer to breakdown, dissolve, digest, or metabolize this metal debris in such a way that it could be completely removed from the body. However, to a large extent the body’s ability to do this is minimal. Being unable to do so, the body’s next reaction is to try to isolate and “wall off” this metallic debris by surrounding it with scar tissue. This process of Foreign Body Reaction results in chronic inflammation. This chronic inflammation can result in loosening of the prosthetic components from the bone, particularly if it finds its way between the bone and the metal component. X-rays may show osteolysis of the bone around the prosthetic parts. This is usually results in hip pain and a failed hip replacement, thus leading to complex revision surgery.

The Metal-On-Metal hip prostheses being implanted are “Cobalt-Chrome.” These are alloys made up of several metals of which cobalt and chrome makeup the largest part. I am not completely certain, but I do not think that Titanium alloys have been used to any extent in these types of prostheses. For the most part these particular alloys are well tolerated by the human body in their implanted form, but when the microscopic metallic debris from the joint is created, this form of these metals is not tolerated, and results in the reaction described above. To the extent that any of this metallic debris can be dissolved, digested, or metabolized to the level of atoms and ions, then the Cobalt or Chromium ions may appear in the blood, and can be tested for in the lab. In a patient with Metallosis, blood testing may show elevated levels of either or both Cobalt and Chromium at levels above what would be considered “normal” (that is if there are any "normal levels” of these elements in human blood). If you combine the patient’s symptoms of pain and functional difficulty with the physical findings, X-ray studies, and appropriate lab work (i.e. “elevated” levels of cobalt or chrome ions in the blood), then you would have a diagnosis of Metallosis. I do not know with certainty that the “elevated" levels of these ions in the blood cause any systemic toxicity problems such as feeling "sick" or “ill." Also, at the blood levels found for these two ions, I do not know whether they cause any organ or tissue damage/disease of the liver, kidneys, brain, heart, or lungs (i.e. other vital organs).

I have seen queries as to how to code for this using ICD-10 in AAPC forums, and also personally from other Coders. The basic code for this would be T84.89X : “Other" Specific Complications of Internal Orthopedic Prosthetic Devices, Implants, or Grafts. Other codes from the T84 Code Set that might also apply are T84.05 : Periprosthetic Osteolysis (which would be an X-ray finding in the documentation); T84.03 : Mechanical Loosening of the prosthesis, which is the usual result of this process over time; T84.06 : Wear of the Articular Bearing Surface, which in reality is the underlying basis of this disorder. And since the patient is usually experiencing pain, then T84.84 _: Pain could also be added to the code list. The 6th Character would be for Laterality. These are 7 Character codes requiring A, D, or S. Any or all of these could be listed if pertinent and clearly documented in the records.

The next aspect of this coding process would be related to the "Metal Toxicity” which would come from the T56 Code Set. Chromium is covered specifically by T56.2X1 : Toxic effect of Chromium and its compounds, accidental and/or unintentional. I have chosen the 6th Character 1 since it is not the intent at the time of the surgical procedure to have this disorder occur, so would be considered “unintentional." Cobalt does not have its own specific code such that T56.891 : Toxic effect of “Other" Metal(s), again “unintentional." If there are any metals other than cobalt and chromium that are tested for, and they do show up as elevated levels in the blood work, then I would probably consider them to be under the same code T56.891 _. Again, these are 7 Character codes requiring A, D, or S.

Lastly, since none of the codes mentioned above are specific to the hip, then the Z96.64 _ code should be listed as that specifies the presence of an artificial hip joint. It is my personal philosophy in diagnosis coding to list all pertinent and relevant codes for the problem at hand. Give the payers everything you have and let them sort out what they do or don't want or need to process your claim. In other words, put the ball in their court and keep it there.

Some people may have questions as to whether the use of “Metal Toxicity" is appropriate when compared to "Metal Allergy” for this problem. People can truly be allergic to some metals, nickel being the most common, and possibly some others that I am less aware of. It is certainly possible that some of the other metals in Cobalt-Chrome alloy implants could be the source of an allergic reaction. Although possible, I am not aware that in the mindset of most Orthopedic Surgeons dealing with Metallosis that they consider this to be much of an allergic disorder. But, “Never say never, and never say always.” However, I would tend to believe that the most common conception of this disorder is that it is in the realm of a “Metal Toxicity.”

Hopefully this discussion of this disorder will help Coders better understand the process and also help guide them to accurate and complete coding of it.

Posted in Coding Blogs on Jul 13, 2017

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