Asian-Specific total knee system: 5-14 year follow-up study

Kunihiro Hosaka,Takanobu Sumino,Yasuaki Tokuhashi,Takao Ishii,Shu Saito,Sei Mori

doi:10.1186/1471-2474-12-251

Abstract

BackgroundKnee size and body size differ in Asians compared with Caucasians. Nevertheless, many total knee arthroplasty (TKA) prostheses used worldwide are made for Western Caucasian subjects. As a result, an Asian's knee might not fit these prostheses. We studied the Flexible Nichidai Knee (FNK) system, a new model of TKA for Asian patients. The purpose of this report is to investigate the outcomes of this prosthesis retrospectively.MethodsWe investigated 1055 primary TKAs in 595 patients who underwent FNK for osteoarthritis (OA) in Japan and were followed for > 5 years. The knee score and function score were used for clinical evaluation. We examined the range of motion (ROM) preoperatively and at final follow-up and radiographic assessments. In addition, postoperative complications were investigated. A survivorship analysis was also conducted using two endpoints: revision for any reason and aseptic failure.Results890 knees in 502 patients were available for study (follow-up rate of 96.0%). The mean follow-up term was 8.3 years (range, 5.0-14.1 years). The knee and function score significantly improved from 41.3 to 90.3 and from 39.1 to 76.2 points, respectively (p < 0.001). The mean ROM in FNK posterior cruciate retaining (CR) type and FNK posterior-stabilized (PS) type ameliorated significantly from 107.8° and 95.6° to 110.7° and 110.4°, respectively (p < 0.01). Ten knees underwent revision surgery (infection in 3 cases, instability in 2, loosening in 2, and non-union of femoral supracondylar fracture, severe pain, and recurrent hemarthrosis in 1 each). The survivorship rate was 99.4% (95% CI, 99.0-99.8) at 5 years (n = 952 patients at risk) and 96.2% (95% CI, 91.9-100) at 12.5 years (n = 49 patients at risk).ConclusionThe FNK prosthesis for Asians achieved excellent mid- to long-term survivorship and clinical results.

Highlights

Knee size and body size differ in Asians compared with Caucasians
Total knee arthroplasty (TKA) is a surgical procedure associated with good success worldwide
We examined the transition of the femorotibial angle (FTA) at pre- and post-total knee arthroplasty (TKA), existence of radiolucent lines, osteolysis, loosening, patellar dislocation, and polyethylene wear with radiographs

Summary

Introduction

Many total knee arthroplasty (TKA) prostheses used worldwide are made for Western Caucasian subjects. We studied the Flexible Nichidai Knee (FNK) system, a new model of TKA for Asian patients. We have used Flexible Nichidai Knee (FNK) systems (Nakashima Medical Co. Okayama, Japan) (Figure 1), manufactured for Asian patients and designed by Ryu et al, for TKA since July 1995. In addition to FNK posterior cruciate retaining (CR) type (Figure 1-a), FNK posterior-stabilized (PS) type (Figure 1-b) has been available since May 1998. Outcomes with these prostheses have not been previously reported. This report describes the outcome at 5 to 14 years follow-up of the FNK system used in Japanese patients with osteoarthritis (OA)

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