An Interesting Case of Osteolysis With Accompanying Metallosis in a Primary Total Knee Arthroplasty

Abstract

Arthroplasty implants are comprised of metal alloys designed to function within the human body. Implant-related issues and associated soft-tissue reactions have been well documented for modular revision hip and knee constructs. This case highlights findings of metallosis in the context of polyethylene wear in a failed primary total knee arthroplasty. Fretting of a polyethylene reinforcement pin within the tibial baseplate as a direct result of knee joint instability appears to be the root cause of observed periprosthetic metallosis. Enhanced design principles and improved polyethylene locking mechanisms may be useful to potentially mitigate fretting-related issues in future knee replacement designs. The authors recommend surveillance in patients with this construct especially when prosthetic instability is present.

Keywords: Locking Mechanism; Metallosis; Osteolysis; Primary Total Knee Arthroplasty.

Figure 1

Radiographs: Preoperative anteroposterior (a) and lateral (b) views. Immediate postoperative anteroposterior (c) and lateral (b) views. Five-year postoperative anteroposterior (e) and lateral (f) views. Seven-year postoperative anteroposterior (g), lateral (h), and oblique views (i and j). Note the gradual varus migration of the tibial and femoral components and progressive bone loss around the lateral femoral condyle and lateral tibial plateau. Postoperative anteroposterior (k) and lateral (l) views of the revision surgery to a distal femoral replacement.

Figure 2

Intraoperative lateral view depicting gray and white fibrous material in the region of the lateral femoral condyle after removal of femoral implant.

Figure 3

Intraoperative anterior view of the distal femur demonstrating complete loss of lateral femoral condyle after debridement of nonviable fibrous tissue.

Figure 4

Representative histology samples from the fibrous tissue collected from the lateral femoral condyle displaying benign bone fragments with areas of remodeling and fibrosis among black pigmented debris material. (left 100x; right 200x).

Figure 5

Representative images of the bearing surface and backside of the retrieved tibial insert in this case.

Figure 6

Optical micrographs of the PE component backside, showing evidence of wear that is consistent with rotational motion of the PE component against the CoCr baseplate. Yellow arrows indicate direction of rotational wear.

Figure 7

Optical micrographs of the Ti post within the tibial insert. There is a clear region of material loss (yellow arrow).

Figure 8

Representative SEM images of the anterior aspect of the metallic post using backscattered imaging. Top left: There is a visible transition between the as-manufactured region and region of apparent material loss on the pin (32x). Top right, bottom: higher magnification images (500x, 300x) of the region of material loss. In the bottom image, the yellow arrows indicate a localized region of mechanically assisted corrosion damage.

Figure 9

Image of one region of interest of possible material transfer and corresponding maps of elemental composition for titanium and iron. The material transferred to the surface was comprised primarily of iron (bottom right).

Conflict of Interest Statement for Denning