Medium to Long-term Results of PFC Sigma Total Knee Arthroplasty
The PFC Sigma knee implant was introduced in 1997. It is the most commonly used system for total knee arthroplasty in England and Wales, accounting for 34.9% of primary implantations in 2006. Studies evaluating medium to long-term implantation outcomes have shown that it is an implant with a high survival rate, low re-implantation rate, and very good clinical results.
Introduction
The PFC Sigma knee endoprosthesis system was designed to achieve maximum flexion in the knee joint without compromising the implant's stability. The intention of this combination was to improve knee mobility to facilitate activities such as kneeling or squatting1. According to data from the National Joint Registry of England, Wales, Northern Ireland, and the Isle of Man, more than 25,000 patients received the implant in 2016 alone, accounting for a 27% share of all primary implantations2. The Sigma implant achieves excellent clinical and radiological results, as evidenced by numerous studies evaluating its survival and functionality in the medium to long term3, 4.
Study Results
Hunter et al. evaluated the results of the PFC Sigma system implantation in the medium to long term of 7–9 years. The study included 275 patients who received a total of 318 PFC Sigma total knee arthroplasties between 1998 and 2000. Out of the original number, 193 patients (225 implants) survived until the final evaluation, with 5 patients (6 implants) lost to follow-up.
Revision surgery was performed on 7 implants (2.2%), with 6 cases due to infection within the first 2 years post-implantation and 1 case involving the replacement of a polyethylene insert 59 months post-implantation. The 9-year implant survival rate was 97.7% for any reason and 99.6% for aseptic failure. The average American Knee Society score was 84 ± 16/100 at 7–9 years post-implantation compared to an average value of 33/100 before implantation. Radiolucent lines were observed in 48 implants, but no radiological signs of implant loosening were recorded in any knee3.
Jain et al. evaluated functional medium-term outcomes over 5–7 years in 501 patients (701 implants). This study also observed significant postoperative improvements in all monitored parameters. After implant surgery, patients achieved an average knee flexion of 134.95° (range 120–150°), compared to a preoperative average flexion of 108.8° (90–120°). A total of 95% of patients were able to sit cross-legged postoperatively, 90% were able to kneel, 70% could perform a half-squat, and 20% a full squat4.
Conclusion
Study results indicate that the PFC Sigma implant demonstrates excellent clinical and radiological outcomes in primary implantations over the medium to long term, with high durability and a low need for revision surgeries.
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CZ-2020-11-120
Sources:
1. Nutton R. W., Wade F. A., Coutts F. J. et al. Does a mobile bearing high flexion design increase the knee flexion after total knee replacement. J Bone Joint Surg Br 2012; 94 (8): 1051−1057, doi: 10.1302/0301-620X.94B8.28828.
2. National Joint Registry for England, Wales, Northern Ireland and the Isle of Man 14th Annual Report, 2017. Prostheses used in hip, knee, ankle, elbow and shoulder replacement procedures 2016. Table 9(a). Available at: www.njrreports.org.uk
3. Hunter N., Clayton R., Brenkel I. Press fit condylar Sigma total knee arthroplasty: 7–9 years results. Eur J Orthop Surg Traumatol 2009; 19: 409–413, doi: 10.1007/s00590-009-0446-6.
4. Jain S., Pathak A. C., Kalaivanan K. Minimum 5-year follow-up results and functional outcome of rotating-platform high-flexion total knee arthroplasty: a prospective study of 701 knees. Arthroplast Today 2016; 2 (3): 127–132, doi: 10.1016/j.artd.2016.01.006.
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