Pseudotumor in Metal-on-Polyethylene THA
This case report details an adverse local tissue reaction in the head-neck junction of a non-modular femoral neck stem with a metal-on-polyethylene bearing.
Terry A. Clyburn, MD
Total hip arthroplasty (THA) is a common and highly successful procedure. Foreign body reaction was recognized early in the history of hip arthroplasty and was initially thought to be solely the result of poly-methyl-methacrylate (PMMA). In fact, this was termed “cement disease.”
Later, even in uncemented implants, severe osteolysis and soft tissue damage were observed, and clearly polyethylene wear was the causative factor. Polyethylene wear disease leading to osteolysis became such a significant issue that extensive work by many researchers and extensive resource expenditures by industry led to the development of ceramic-on-ceramic, metal-on-metal, and “improved polyethylene” bearing surfaces.
Reports of higher-than-expected failure rates with some metal-on-metal implants have led to recalls, lawsuits, and a significant downturn in their use. [1,2,3] Most have presumed that the actual metal-on-metal articulation was the source of elevated ion levels and, thus, the local tissue reactions. There are, however, reports of cases of adverse local tissue reaction (ALTR) in non-metal-on-metal total hips. [4,5,6,7]
Modular necks introduce an additional interface that may contribute to local metal debris and ion loads. [8,9] A recent case report documents the stem-neck interface as a probable cause of ALTR in a ceramic-on-polyethylene articulation. 
The present case report details an ALTR in the head-neck junction of a non-modular femoral neck stem with a metal-on-polyethylene bearing. Surgical findings and photographs show that the metal source was the head-neck articulation.
A 52-year-old female underwent THA in 2007 at another facility. The surgeon utilized an Accolade 52-mm acetabulum with a Trident X3 standard polyethylene and a metal 32-mm +4 head on a size 2 Accolade TMZF HA stem. (Stryker, Kalamazoo, Michigan)
The patient did well until August of 2012, when she experienced increasing pain in the right groin and buttocks region. Ambulation became increasingly difficult. Workup in her home facility included an X-ray that revealed a stable implant, but with evidence of osteolysis about the ischium (Figure 1). A technetium three-phase bone scan showed increased uptake about the greater trochanter.
Figure 1. Note the severe osteolysis about the greater trochanter, calcar region and ischium.
Due to increasing pain, an aspirate was performed under fluoroscopic guidance and 1 mL of purulent appearing material was obtained. Cultures were sent to the lab, but no growth was observed. The patient was advised to return for further follow-up should the pain continue.
The patient presented to our facility wheelchair-bound and in severe pain. Her temperature was 100.5 F. She denied taking antibiotics but was taking large doses of hydrocodone/acetominophen.
She had a palpable and large mass on the lateral aspect of her hip, which was felt to be fluctuant. Her ESR was 40 and her CRP was 46. A needle aspiration in the office with an 18-gauge needle produced no fluid.
The patient was admitted to the hospital and a Jamshidi needle (CareFusion, Chicago, IL) was used. With the large-bore needle, more than 120 mL of fluid was collected; remarkably, a large amount of fluid was lost as it literally shot to the ceiling before the syringe could be attached. The material appeared to be grossly purulent. The fluid, however, showed only 2000 WBCs.
Although the presentation was somewhat unusual, the patient’s pain was so severe and the aspiration so profound that we assumed she had a non-standard presentation of an infected total hip. She was taken to the OR for explantation and an antibiotic loaded PMMA implant (PROSTALAC). (Figure 2). Cultures from the aspirate and also from the surgical specimens were negative, but permanent pathology was typical of ALTR. (Figures 3,4,5).
Figure 2. PROSTALAC in place. Note thin shell of greater trochanter and fragmentation about abductor attachment points.
Figure 3. Note chronic inflammation with plasma cells and lymphocytes.
Figure 4. Taken from the backside of the acetabulum with fragments of bone with ischemic necrosis, chronic inflammatory tissue and dense fibrous tissue.
Figure 5. Note primarily chronic inflammatory changes, but with small areas of acute inflammatory change.
In the OR, it was observed that the patient had a massive pseudotumor under extreme pressure. The lesion was noted to be immediately under the skin, and when touched with the #10 scalpel, purulent-appearing fluid reached 3 feet above the patient. Figure 6 is taken of the pseudotumor after removal of this fluid.
Figure 6. The pseudotumor is seen posterior to the greater trochanter. This photo was taken after at least 200-300 cc of purulent appearing fluid had been removed.
The tissue of the pseudotumor appeared to be very aggressive. Significant damage was noted about the abductor attachment to the greater trochanter. Although the tendons remained attached, much of the trochanter was denuded of attachments. The osteolysis had resulted in marked loss of the inner aspect of the greater trochanter and had eroded around the stem extensively. (Figure 7).
Figure 7. Note the inflammatory tissue about the stem and the marked osteolysis about the entire proximal femur and greater trochanter.
There was marked osteolysis about the inferior aspect of the acetabulum and mild metallic staining of all of the removed tissue. The metallic femoral head was easily removed from the femoral stem. We observed and photographed evidence of metal debris and damage at this interface, which would seem to reveal evidence of movement. (Figures 8, 9).
Figure 8. Note the metallic staining and obvious fretting about the trunion.
Figure 9. Note the damage inside the head with severe fretting.
The femoral stem did have areas of osseous integration, but was easily removed without need for an extended trochanteric osteotomy. The cup was also relatively easily removed with Moreland Acetabular chisels (Innomed, Savannah, GA). The back side showed small areas of osseous integration, but this was minimal. (Figure 10).
Figure 10. Note the small areas of osseous integration with primarily no or only fibrous ingrowth.
Again, as we presumed the patient to have an infection, we chose to place the PROSTALAC and await cultures. All cultures including those for acid fast bacteria and fungus were negative at 6 weeks. The patient was not treated parenterally, other than the first 24 hours of prophylactic antibiotics after the PROSTALAC was implanted.
The patient’s ESR and CRP were 3 and 0.34, respectively, at the time of reimplantation of the hip. All tissues had a benign appearance; frozen section revealed “mild” inflammation, but with 1-2 polymorphonucleocytes (PMNs) per high power field (HPF).
We chose to use a ceramic-on-highly cross-linked polyethylene and we augmented the acetabular fixation with screws. (Figure 11).
Figure 11. Immediate postop radiographs of reimplanted prosthesis.
Virtually all modern total hip stems incorporate a Morse taper, allowing for adjustability of femoral head diameter, head length, and material choices. There is variability of design of the Morse taper. The stem used in this case report was a V-40 taper. The head size was not particularly large at 32 mm.
Theoretically, as the diameter of the head is increased, and thus the lever arm about the Morse taper, rotational forces on the Morse taper interface may increase. Also, in this case, a plus 4-mm head length was used. It is possible, in theory, that with plus size head lengths, the actual contact area of the Morse taper interface would be reduced, resulting in less stability, movement, and fretting.
In this case, the stem was an HA-coated stem. The stem appeared to be stable with evidence of bone in-growth, but there are reports of HA material resulting in ALTRs . Although it would be impossible to argue that the HA could not have been a factor in the failure and pseudotumor formation in this case, the findings about the Morse taper were quite profound and would be most likely the cause of failure. No gross particulate matter was noted in the pathology sections.
In my practice, I recommended a metal-on-metal articulation for the majority of my patients from 1998 until 2011. Due to reports, published data, and a generally negative legal environment with regard to metal-on-metal, I have reduced the use of metal-on-metal articulations to less than 5% of my cases. I have not performed a revision, and I am not aware of any of my metal-on-metal patients having undergone revision as a result of an ALTR.
Ironically, the only revision I have done is the one highlighted in this case report, in which a patient with a metal-on-polyethylene articulation developed a pseudotumor with histologic findings of ALTR.
Clearly, we must continue to carefully document all failures, study them, and report them. We must be cautious to avoid making broad assumptions when failures occur. It is apparent that there are multiple modes of failure and that the metal-on-metal articulation alone is not the sole cause of failure in every case.
Terry A. Clyburn, MD, is an orthopaedic surgeon from Joint Replacement Associates, Houston, Texas.
Clyburn TA. Pseudotumor in Metal-on-Polyethylene Total Hip Arthroplasty – A Case Report. Reconstructive Review, a publication of the Joint Implant Surgery & Research Foundation (JISRF). 2013;3(1):18-21. Copyright 2014 Terry Clyburn MD. This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.
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