Metal wear-induced pseudotumour following an endoprosthetic knee replacement for Ewing sarcoma

Taper Junction Subsidence Occurs in Modular Tumor Endoprostheses: How Concerned Should We Be?

BACKGROUND

Advancements in musculoskeletal oncologic treatment have allowed for longer survival of patients with malignant bone tumors and the associated longer use of tumor endoprostheses in those who have had such reconstructions. Several studies have reported on increased serum metal ions with the use of such implants. Modularity in these implants introduces the risk of taper junction corrosion and subsidence resulting in metal wear particle release that may cause an adverse local tissue reaction or systemic toxicity. Additionally, these implants contain a large surface area of cobalt and chromium. It is unclear whether the source of the increased serum ion levels was due to the taper junction corrosion or the implant itself. To our knowledge, no prior study has reported on taper junction subsidence.

QUESTIONS/PURPOSES

In this study we sought (1) to determine survivorship free from radiographic taper junction subsidence in a femoral modular tumor endoprosthesis, and (2) to identify the implant characteristics in the endoprostheses associated with taper subsidence.

METHODS

Between January 1996 and February 2020, the senior author performed 150 proximal or distal femur replacements following resections of soft tissue or bone tumors of the thigh and femur. Of those, 6% (9 of 150) of patients were lost to follow-up before 2 years, 25% (37 of 150) could not be analyzed due to absence of plain radiographs during follow-up, and 13% (20 of 150) died before 2 years follow-up, leaving 56% (84 of 150) for analysis in this retrospective study, with a median time for analysis of 14 years (range 2 to 31 years) after the index resection and endoprosthetic reconstruction for patients with distal femur replacements and 5 years (range 2 to 19 years) for patients with proximal femur replacement. Radiographs involving the entire implant were evaluated for the presence or absence of subsidence of the taper junction that was evident and clear to see if present. The association between the number of taper junctions, the length of resection, the number of collapsed junctions, and the time to collapse from the initial surgery were examined using regression analysis.

RESULTS

Overall, 14% (12 of 84) patients with a distal femur replacement had radiographic collapse of at least one of the modular tapers. Survivorship free from taper subsidence was 91% (95% CI 86% to 96%) at 10 years and 84% (95% CI 78% to 90%) at 20 years. All patients were in the distal femur replacement group. The median follow-up of patients with subsidence was 15 years (range 5 to 26). Fifty-eight percent (7 of 12) of patients had two junctions involved, 25% (3 of 12) had three junctions, and 17% (2 of 12) had one junction involved. All but one patient had subsidence in a single junction. The median time to subsidence was 15 years (range 4.5 to 24.0 years). The subsidence was progressive in all patients who demonstrated it. The taper junction subsidence was complete in 75% (9 of 12) of patients and partial in 25% (3 of 12). Univariate and multivariable regression analyses did not show that the risk factors we studied were associated with subsidence. Two patients with junction subsidence were revised, one for taper fracture and one during busing exchange for distal junction subsidence.

CONCLUSION

Taper damage with late and progressive subsidence of the intervening junction is not uncommon after distal femur replacement. The impact of such a complication is still unknown. Further studies should examine the long-term outcomes and correlate them with metal ion levels.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Ultrasound evaluations and guided procedures of the painful joint arthroplasty

The purpose of this article is to describe the use of ultrasound for the diagnosis and treatment of painful joint arthroplasty. Ultrasound plays a crucial role in the diagnosis of the painful joint arthroplasty, especially given its unique dynamic capabilities, convenience, and high resolution. Ultrasound guidance is also instrumental for procedures in both diagnosing and in select cases, treating the painful joint arthroplasty. Topics to be discussed in this article include trends in arthroplasty placement, benefits of the use of ultrasound overall, and ultrasound evaluation of periprosthetic joint infections. We will also review the sonographic findings with dissociated/displaced components and adverse reaction to metallic debris including metallosis, trunnionosis, and metal-on-metal pseudotumors. Additionally, we will discuss ultrasound evaluation of tendon pathologies with arthroplasties, including dynamic maneuvers to evaluate for tendon impingement/snapping. Finally, we will cover ultrasound-guided joint arthroplasty injection indications and precautions. KEY POINTS: • Ultrasound is preferred over MRI in patients with joint arthroplasty and plays a crucial role in diagnosis, especially given its unique dynamic capabilities, convenience and high resolution. • It is especially beneficial for US-guided aspiration in periprosthetic joint infections; effectively used to evaluate periprosthetic fluid collections, facilitating differentiation between abscesses and aseptic collections, and tracking sinus tracts. • Recently, the diagnosis of periprosthetic joint infections has shifted focus to biomarkers in the periprosthetic fluid, specifically α-defensin, which has a high sensitivity and specificity for diagnosing infection. • Cutibacterium acnes is a major pathogen responsible for shoulder arthroplasty infections, often presenting with normal laboratory values and since slow growing, must be kept for a minimum of 14 days.

Metal wear debris generation in primary total knee arthroplasty: is it an issue?

More durable total knee arthroplasties (TKAs) are needed, due to the rising life expectancy, the higher activity levels of patients and the growing concerns about aseptic loosening being caused by metal hypersensitivity. In response, different hypoallergenic metal coatings have been developed for TKAs. However, possible adverse effects of these different metals (cobalt-chromium-molybdenum, zirconium, titanium and tantalum) have been neglected. The aim was to summarize the local and systemic adverse effects (including metal hypersensitivity), survival ratios, patient-reported outcome measures (PROMs) and the plasma metal ion concentrations of the different TKA coatings. A literature search on PubMed and EMBASE was performed. In total, 15 studies were found eligible. Common adverse effects of TKA were infection, loosening, pain, instability and hyper- coagulation disorders. Serious adverse effects related to TKA implants were not reported. The survival ratios and patient-reported outcome measures seem to confirm these good results. In contrast with chromium and cobalt, no significant differences were reported in the nickel, molybdenum and titanium concentrations. No significant differences between the hypoallergenic and standard TKA implants were found in terms of adverse effects, survival ratios and PROMs. A causal relationship between the common adverse effects and the different metals is unlikely. Due to the heterogeneity of the TKA implants used, no firm conclusions could be made. Further research with longer follow-up studies are needed to find possible adverse effects and differences. Thus far, the hypoallergenic implants seem to perform equal to the standard implants.

Cobalt-chromium femoral components developed scratches and released metal debris in simulated wear whereas ceramic femoral components did not

AIMS

The aims of this study were to evaluate wear on the surface of cobalt-chromium (CoCr) femoral components used in total knee arthroplasty (TKA) and compare the wear of these components with that of ceramic femoral components.

METHODS

Optical profilometry was used to evaluate surface roughness and to examine the features created by the wear process in a knee wear simulator. We developed a method of measuring surface changes on five CoCr femoral components and quantifying the loss of material from the articular surface during the wear process. We also examined the articular surface of three ceramic femoral components from a previous test for evidence of surface damage, and compared it with that of CoCr components.

RESULTS

We found that the surface roughness of CoCr components rapidly increased during the first 1,000 wear cycles, then reached a steady state, but material loss from the surface continued at a rate of 1,778,000 μm³ per million cycles as carbides were removed from its matrix. These carbides formed third-body wear particles, leading to the formation of new scratches even as older scratches were worn away. In contrast, no scratching, loss of material, or other surface damage, when evaluated with one nanometer resolution, was found on the surface of the ceramic components after a 15 M wear cycle test.

CONCLUSION

This study showed wear and loss of CoCr material from scratching and microabrasive wear in TKA. The material loss from the surface continued in a linear relationship with increasing cycles. We also found the absence of scratching and roughening of ceramic femoral components in simulated wear, suggesting an advantage in wear rate and avoiding metal sensitivity. This may have implications in the management of persistent pain after TKA. Cite this article: Bone Joint J 2021;103-B(6 Supple A):94-101.

Large Soft-tissue Mass Formation After Revision Total Knee Arthroplasty: An Unusual Case of Adverse Reaction to Metal Debris and Review of the Literature

We report about the rare case of a patient who developed large soft-tissue mass formations related with revision total knee arthroplasty which was implanted 4 years prior. Owing to suspected periprosthetic joint infection, the prosthesis was removed and the lesions were resected, resulting in severe soft-tissue loss and temporary arthrodesis using a poly(methyl methacrylate) spacer. Histological analysis revealed a type VI periprosthetic membrane. The situation was further complicated by wound infection requiring multiple revision surgeries. After discussion and evaluation of the available treatment options, the decision for an above-the-knee amputation was made. The tissue reaction resulting in these soft-tissue lesions is referred to as an "adverse local tissue reaction." Wear-induced lesions after total knee arthroplasty, especially of this magnitude, are very rare and difficult to treat.

Blood Metal Ion Release After Primary Total Knee Arthroplasty: A Prospective Study

Objectives

To investigate the course of in vivo blood metal ion levels in patients undergoing primary total knee arthroplasty (TKA) and to investigate potential risk factors associated with metal ion release in these patients.

Methods

Twenty‐five patients with indication for TKA were included in this prospective study. Whole blood metal ion analysis was performed pre‐operatively and at 1 week, 6 weeks, 3 months, 6 months, and 12 months postoperatively. Clinical scores were obtained using the American Knee Society Score (AKSS) and the Oxford Knee Score (OKS) at each follow‐up and patientsʼ activity levels were assessed by measuring the mean annual walking cycles at 12 months follow‐up. Anteroposterior and lateral radiographs of the operated knee were evaluated postoperatively and at 12‐month follow‐up with regard to implant position and radiological signs of implant loosening. Correlation analysis using multivariate linear regression was performed to investigate the influence of different variables (age, gender, functional scores, number of walking cycles, and body mass index [BMI]) on blood cobalt ion concentrations.

Results

Mean metal ion levels of cobalt, chromium, molybdenum, and titanium were 0.28 μg/L (SD, 0.14), 0.43 μg/L (SD, 0.49), 0.62 μg/L (SD, 0.45), and 1.96 μg/L (SD, 0.98), respectively at 12‐month follow‐up. Mean cobalt ion levels significantly increased 1‐year after surgery compared to preoperative measurements. There was no statistically significant increase of mean metal ion levels of chromium, titanium, and molybdenum at 1‐year follow‐up. Overall, metal ion levels were low and no patient demonstrated cobalt ion levels above 1 μg/L. Postoperative radiographs demonstrated well‐aligned TKAs in all patients and no signs of osteolysis or implant loosening were detected at 1‐year follow‐up. Both the AKSS and OKS significantly improved during the course of the study up to the final follow‐up. Multivariate regression analysis did not show a statistically significant correlation between the tested variables and blood cobalt ion concentrations.

Conclusion

A statistically significant increase of mean cobalt ion concentration at 1‐year follow‐up was found in this cohort of patients with well‐functioning TKA, although overall blood metal ion levels were relatively low. Despite low systemic metal ion concentrations seen in this cohort, the local effects of increased metal ion concentrations in the periprosthetic environment on the long‐term outcome of TKA should be further investigated.

Ultrasonographic and radiographic findings of polyethylene component displacement with severe metallosis and metal-induced synovitis following total knee arthroplasty

Aseptic loosening and wear is second to only infection as the most common cause of arthroplasty failure. Degeneration of the polyethylene and metal arthroplasty components can lead to metallosis, which can cause a combination of direct cytotoxic effects and an inflammatory response within the synovial and periarticular tissues. This can result in bone resorption and secondary arthroplasty component loosening as well as a metal containing joint effusion and metal-induced synovitis. Little literature exists as to the ultrasonographic findings of metal-induced synovitis and polyethylene component displacement. As the use of musculoskeletal ultrasound significantly increases, being aware of these findings is important. The most important ultrasonographic findings include differentiating a joint effusion from synovitis utilizing dynamic compression, identifying areas of echogenic shadowing related to metal deposition and visualizing displaced arthroplasty components. The following is a case report that demonstrates the ultrasonographic imaging findings of metallosis, metal-induced synovitis and polyethylene component displacement. We will also demonstrate the ultrasound-guided aspiration findings as well as radiographic and gross pathologic correlations.