Technique for identification of submicron metal particulate from implants in histological specimens

Histological Analysis of a Retrieved Porous Tantalum Total Ankle Replacement: A Case Report

CASE

We present a case report documenting the retrieval and histological analysis of a porous tantalum (P-Ta) total ankle replacement (TAR) from a 50-year-old woman after a below-knee transtibial amputation. This rare opportunity to examine an intact TAR may help to better understand the implant-bone relationship because it would be in situ.

CONCLUSION

In this case study, we demonstrate bone ingrowth to the first layer of the P-Ta and organized trabecular orientation, suggesting that equal bone load was achieved on the base and the rails in both components using a transfibular surgical approach.

Histologic retrieval analysis of a porous tantalum metal implant in an infected primary total knee arthroplasty

Porous tantalum (Zimmer, Inc, Warsaw, Ind) has the theoretical advantage of improved biologic fixation because of its high porosity, interconnected pore space, and modulus of elasticity. We present a case report documenting the retrieval and bone ingrowth analysis of a porous tantalum tibial component in an infected total knee arthroplasty. Results demonstrated a significantly larger amount of bone ingrowth present in the tibial posts (36.7%) when compared with the bone ingrowth into the tibial baseplate (4.9%) (P < .001). The data suggest that bone ingrowth seen in the plugs as well as baseplate was suggestive of viable bone tissue with healthy bone marrow, osteocytes, and lamella, resulting in a well-fixed tibial implant even at revision surgery for an infected total knee arthroplasty.

Polymethylmethacrylate (PMMA) as an embedding medium preserving tissues and foreign materials encroaching in endovascular devices

Problems of displacement, poor healing, degradation of the polymers and corrosion of the metallic frame in endovascular devices still require in-depth investigations. As the tissues and the foreign materials are in close contact, it is of paramount importance to efficiently investigate the interfaces between them. Inclusion in polymethymethacrylate (PMMA) permits us to obtain thin slides and preserve the capacity to perform the appropriate stainings. An AneuRx prosthesis was harvested in bloc with the surrounding tissues at the autopsy of a patient 25 months post deployment in a 5.7 cm diameter AAA and sectioned in the direction of the blood flow in two halves. A cross-section of the encapsulated distal segment together with the surrounding aneuryshmal sac was embedded in polymethylmethacrylate (PMMA). Further to complete polymerization, slices of the specimen were cut on a precision banding saw under coolant. They were affixed onto methacrylate slides with a UV cured adhesive. Binding and polishing were done on a numeric grinder and slices 25 to 30 microm in thickness were stained with toluidine blue prior to observation in light microscopy. Additional slices were prepared for scanning electron microscopy and X-ray energy dispersive spectrometry for determination of the elemental composition of the Nitinol stent. The aortic wall did not demonstrate complete integrity along with its circumference. Some areas of rupture were noted. The content of the sac was heavily shrunk and was mostly acellular. The walls of the device were very well encapsulated. The PMMA embedding permitted the polyester wall, the Nitinol wire and the collagen to keep in close contact. Scanning electron microscopy involved backscattered electrons and confirmed the corrosion the Nitinol wire at the boundary with living tissues. Based upon the results obtained, we believe that PMMA embedding is the most appropriate method to process endovascular devices for histological and material investigation. Needless to say, that paraffin embedding would have not been feasible for such a big size specimen involving different materials.

Elemental and morphological identification of third-body particulate and calcium stearate inclusions in polyethylene components

Third-body particulate such as human bone chips, hydroxyapatite, and bone cement are considered contributing factors in accelerated wear in total joint replacement. Particulate wear debris is now considered the major contributing factor in aseptic loosening of total joint replacements. The ability to distinguish between different third-body particulate is necessary to better understand wear mechanisms when conducting implant retrieval analysis. The objective of this investigation is to demonstrate that backscattered electron imaging with correlated energy dispersive X-ray analysis can accurately identify third-body particulate in retrieved polyethylene components. It is important that this technique can also distinguish between third-body particulate and normal inclusions in the polyethylene such as calcium stearate, based on the distinct morphology and elemental composition of each material. Therefore, the ability to distinguish third-body particulate from calcium stearate inclusions is essential in gaining a better understanding of the contributing factors associated with coating separation and accelerated wear observed in clinically retrieved polyethylene components.