Knee arthroplasty clinical performance

Collier J.P., D.K. Sperling, J.H. Currier, et al. 1996. Impact of gamma sterilization on clinical performance of polyethylene in the knee. Arthroplasty 11 377-389. 

The data plotted in Figure 5.2 indicate that approximately 36 to 37% of primary tofal joinf procedures are performed for fhe hip and opposed fo the knee, and this ratio is not expected to change substantially over the next 30 years. Although total hip arthroplasty (THA) is performed less offen than total knee arthroplasty, the clinical performance of fhe hip has been sfudied to a much greater extent than that of the knee. Consequently, the focus of this chapter is on the clinical performance of THA. 

Although knee arthroplasty enjoys a remarkable clinical track record, problems with wear and fatigue damage of UHMWPE continue to limit the longevity of both unicondylar and bicondylar knee replacement components. Unlike in the hip, where radiographic techniques have been developed to quantify in vivo wear rates, there currently exist no standard and widely accepted techniques for tracking the clinical performance of UHMWPE in patients with knee replacement. Thus, today the most effective way to evaluate the in vivo performance of UHMWPE continues to be the analysis of retrieved components from revision surgery or from autopsy donations. 

This chapter contains four main sections covering TKA and, where applicable, UKA. The first section reviews the biomechanical considerations of knee arthroplasty that distinguish it from hip replacement. The second section describes the survivorship of TKA and UKA, and outlines measures of clinical performance for UHMWPE in knee arthroplasty. The third section is devoted to wear and osteolysis in TKA. In the final section of this chapter, alternatives to metal-on-conventional UHMWPE articulation for knee arttiroplasty are described. 

On the other hand, survivorship alone does not fully capture the clinical performance of UHMWPE in the knee. Surface damage and wear of the UHMWPE insert are also important metrics of clinical performance of knee arthroplasty. If a knee prosthesis survives the first 10 years of implantation, wear behavior of the insert plays an increasing role in the longevity of the joint replacement. In the following sections, we describe the survivorship of TKA, as well as the assessment of wear and surface damage in knee arthroplasty. 

Collier JP, Sperling DK, Currier JH, Sutula LC, Saum KA, Mayor MB. Impact of ganuna sterilization on clinical performance of polyethylene in the knee. J Arthroplasty 1996 ll(4) 377-89. 

UHMWPE wear continues to be an important factor in the long-term survivability of orthopedic implants [1-3]. As established in Chapter 23, periprosthetic osteolysis occurs secondary to the generation of UHMWPE wear debris in total hip arthroplasty (THA) [1, 2, 4]. In the last decade, efforts have been made to increase the wear resistance of UHMWPE [1, 5, 6], Highly crosslinked UHMWPE (Chapters 13 and 14) was introduced in THA 10 years ago and more recently in total knee arthroplasty. UHMWPE wear volume and wear patterns must be fiiUy evaluated to understand historic UHMWPE wear processes to evaluate the efficacy of highly crosslinked UHMWPE and to analyze future UHMWPE formulations that attempt to improve the clinical performance of UHMWPE. 

Hydroxylapatite plasma sprayed coatings have been used in total hip arthroplasties (Jaffe and Scott 1996), dental implants (Ong and Chan 1999), knee replacements, ankle arthroplasties (Zerahn et al. 2000), orthopaedic screws (Magyar et al. 1997), and spinal implants. The most widely used application is the femoral stem where 11 year clinical results show slightly better performance than cemented prostheses (Ravelin et al. 2000). 

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