Patellar Component Loosening

CASE STUDY

A 57-year-old man with a medical history of hypertension and hyperlipidemia presented to our clinic for consultation. He had undergone right total knee arthroplasty 3 years earlier at another institution. He has developed progressive anterior knee pain and crepitus, which has limited his ambulatory capacity. He denies having had fever, chills, or wound problems. He is able to perform a straight leg raise, although with pain.

Radiographs taken in the clinic demonstrated patellar osteolysis and radiolucencies surrounding the femoral and tibial components ( Fig. 25.1 ). Test results for serum inflammatory markers were negative. At the time of revision surgery, after removal of the polyethylene patellar button and surrounding membrane, the residual shell of bone was too thin to accept a standard cemented patellar component ( Fig. 25.2 ).

FIGURE 25.1, A, Lateral radiograph of a failed total knee arthroplasty before revision surgery shows osteolysis about the patellar, femoral, and tibial components. Severe osteolysis is demonstrated behind the polyethylene button (arrow) . B, Merchant view radiograph of the patellofemoral articulation shows evidence of osteolysis about the patellar button (arrow) .

FIGURE 25.2, Remnant patella bone after removal of a failed patellar implant is débrided of membranous tissue.

Algorithm

Management of a failed patellar component follows the tenets of revision total knee arthroplasty. Care must be taken to evaluate the cause of failure, the integrity of the patellar prosthesis and extensor mechanism, and the alignment and orientation of the femoral and tibial components. Periprosthetic infection should be ruled out, and host factors should be optimized. Findings of the intraoperative assessment of the patellar host bone bed guide the choice of surgical options. The algorithm presents an approach to the patient with a failed patellar component that requires revision arthroplasty; nonoperative options are not discussed.

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Chapter Synopsis

Management of patella bone loss during revision total knee arthroplasty (TKA) can pose significant challenges. Treatment options depend on the integrity of the extensor mechanism and the quantity and vascularity of remnant host bone. This chapter describes a case of patella bone loss managed with a porous metal patellar component.

Important Points

Proper femoral and tibial component rotation is crucial for patellar component tracking and successful patella reconstruction.
Viable and vascular host bone is critical for bone ingrowth and reconstruction using a porous tantalum (PT) or trabecular metal patellar component.

Clinical/Surgical Pearls

Before patellar reconstruction, attention must be paid to proper femoral and tibial component positioning.
The extensor mechanism must be inspected for continuity and disruptions.
When using PT patellar components, a high-speed bur or hemispherical reamers can be used to prepare the patellar surface before implantation. The tourniquet should be deflated to confirm the presence of bleeding and viable host bone before implantation.
At least 50% contact with host bone is needed to accept the PT implant.

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