Polyethylene wear and particulate-induced complications affect the survival of primary and revision total hip prostheses. Polyethylene failure can present as a fracture of the acetabular liner, massive liner wear with or without osteolysis-associated complications, or a combination of the two. Various degrees of metallosis can be seen in cases of catastrophic polyethylene failure. If the polyethylene wear or failure is not surgically addressed in a timely fashion, not only can the acetabular cup loosen, but massive wear of the acetabular metal shell may ensue with possible destruction of the component's locking mechanism.
We present a case of a patient with catastrophic polyethylene failure and wear-through of the titanium acetabular component, resulting in severe periacetabular metallosis. Preoperatively, the patient was known to have chronic renal insufficiency thought to be secondary to hypertension. After removal of the metal-ion generator by revision of the acetabular cup, the renal insufficiency markedly improved. We are not aware of any other articles describing renal failure in the setting of metallosis secondary to total hip arthroplasty failure and its improvement with revision of the total hip arthroplasty. The patient was informed that data concerning the case would be submitted for publication, and he consented.
A forty-year-old male automobile mechanic, who had undergone a right total hip arthroplasty seventeen years earlier, presented with a squeaking noise from the right hip and pain of one year's duration. Prior to this presentation, he had been lost to follow-up for approximately ten years after the arthroplasty. The patient's medical history was notable for colon cancer and hypertension. On physical examination, there was obvious noise and crepitus during hip motion, and the patient had an antalgic gait. The Harris hip score was 43 points. Radiographs (Fig. 1) showed catastrophic wear of the femoral head through the acetabular cup with fracture of the supplemental screw fixation. Initially, it appeared that the hip was dislocated, but a lateral radiograph confirmed wear-through of the acetabular cup.
Preoperative laboratory values, including the white blood-cell count, erythrocyte sedimentation rate, and C-reactive protein level, were normal. The patient, however, was found to have renal insufficiency with a blood urea nitrogen level of 37 mg/dL (normal, 7 to 20 mg/dL) and a creatinine level of 2.26 mg/dL (normal, 0.5 to 1.5 mg/dL). The renal insufficiency was considered to be chronic and secondary to the hypertension. Serum metal-ions levels were: titanium, 456.87 ng/mL (normal, 4.1 ng/mL); cobalt, 1.55 ng/mL (normal, 0.1 to 0.2 ng/mL); chromium, 0.914 ng/mL (normal, 0.15 ng/mL); and nickel, 0.48 ng/mL (normal, 0.3 ng/mL).
The patient subsequently underwent an isolated revision of the right acetabular component. A large amount of black, metallic-stained synovial fluid was present. On surgical exposure of the acetabulum, a large amount of metallic debris and metallic-stained tissue was encountered and debrided. Catastrophic failure of the polyethylene liner, with destruction of the screw heads and holes in the cup, was noted. A metal cutting burr was used to section the remainder of the cup for removal.
An intraoperative frozen section was negative for acute inflammation, and the cell counts revealed 1150 white blood cells/μL (38% segmented leukocytes, 11% lymphocytes, and 51% monocytes) and 30,000 red blood cells/μL in the synovial fluid. A porous tantalum revision acetabular shell (Zimmer, Warsaw, Indiana) with supplemental screw fixation and a cemented highly cross-linked polyethylene liner was implanted. An unconstrained tripolar construct (a large bipolar head mating with an acetabular cup) was utilized to provide hip stability and avoid the high implant-bone stress associated with a constrained liner.
The patient did well in the initial postoperative period and progressed accordingly. Six-month follow-up radiographs of the right hip showed an osseointegrated acetabular component. The Harris hip score had improved from 43 points preoperatively to 88 points at the time of the most recent follow-up, fourteen months postoperatively.
Serial serum assessment exhibited an overall trend toward decreasing metal-ion levels over the time interval studied. The titanium, chromium, and nickel levels decreased substantially, whereas the cobalt levels fluctuated (Figs. 2-A and 2-B). Improvement in renal function was noted throughout the follow-up period, with the blood urea nitrogen level decreasing from 33 mg/dL at ten weeks to 22 mg/dL at six months (normal range, 7 to 20 mg/dL) and the creatinine level decreasing from 2.4 mg/dL preoperatively to 1.6 mg/dL at six months (normal range, 0.5 to 1.5 mg/dL) (Figs. 3-A and 3-B). There was no other apparent explanation to account for these findings other than removal of the metal-ion generator. It appeared that the decreasing serum metal-ion levels coincided with a precipitous improvement in the patient's renal function.
We present the case of a patient with impaired renal function as well as massive acetabular wear-through and marked metallosis seventeen years following a primary total hip arthroplasty. After revision total hip arthroplasty and excision of the metallosis debris, the kidney function improved, as did the systemic metal-ion levels. To our knowledge, there are no other reports documenting this association among elevated metal ion levels, catastrophic implant failure, and renal impairment.
There are several reports in the literature describing extensive polyethylene wear with a variety of acetabular components and polyethylene combinations1-6. Furthermore, wear-through of the polyethylene may be associated with pericapsular metallosis, which can extend throughout the so-called effective joint space. The case that we present here demonstrates that complete wear-through of a polyethylene liner and adjacent cup can result in notable metallosis. The long-term systemic effects of metallosis and potential increases in serum titanium, vanadium, chromium, and cobalt levels are currently unknown7-9.
We believe that it is likely that the metallosis in our patient was related to his renal insufficiency, as his renal function improved after the potential offending agent was removed. He had a history of hypertension that may have contributed to the compromised renal function; however, the improvement in renal function coincided with the revision surgery and was not a result of a change in medication or improved blood pressure control. Thus, it is feasible that the metallosis and associated increase in serum metal-ion levels affected kidney performance, as these ions are typically cleared by the renal system. A recent study demonstrated increased serum cobalt levels after metal-on-metal total hip arthroplasty in patients with renal failure as compared with the levels in patients with normal renal function10. It is important that the potential harmful sequelae of the use of a metal-on-metal bearing be considered. According to U.S. Food and Drug Administration (FDA) recommendations, renal failure is a contraindication to metal-on-metal hip resurfacing11.
Our case raises important concerns with regard to the frequency of follow-up after total joint arthroplasty. Teeny et al. conducted a survey of members of the American Association of Hip and Knee Surgeons and found substantial differences among surgeons with regard to follow-up after total joint arthroplasty12. The authors of a recent study proposed that no follow-up for seven years after total joint arthroplasty is cost-effective13. However, many authors have stated that the optimal screening time starts at five years postoperatively14,15. Regardless of recommendations regarding annual or biannual follow-up, patient compliance is extremely low16. Emphasis on continued follow-up is even more important for younger, active individuals as they tend to experience wear at a quicker rate than older individuals.
The present case emphasizes the importance of continued outpatient follow-up after total hip arthroplasty. With routine clinical visits, polyethylene wear can be diagnosed early and be addressed with a relatively routine femoral head and liner exchange. With delayed presentation, the revision procedure can be more complex and costly, with a lower potential for long-term success17. More importantly, deleterious and potentially catastrophic systemic effects, such as renal failure, may be avoided with earlier detection.