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Polyethylene tibial components for younger, active patients JBJS

Josephine

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All-polyethylene tibial components may be appropriate for younger, active patients

Despite advocating the use of all-polyethylene tibial implants in elderly patients under 180lbs., a surgeon has reported excellent long-term clinical and radiographic results in younger patients who underwent total knee arthroplasty using all-polyethylene tibial components.

“The following technical points are important: achieve a flat tibial cut, size the component correctly, cement the femur first, restore the posterior offset, lateralize the femur, cement the tibia last, and clean the cement posteriorly,” Chitranjan S. Ranawat, MD, said at the "Current Concepts in Joint Replacement 2010 Winter Meeting"

Ranawat presented 10- to 18-year follow-up data on a series of 46 all-polyethylene tibial implants in 33 active, younger patients. The average patient age at the time of the procedure was 55 years.

Results with all-polyethylene
Knee Society scores showed good-to-excellent results in 97% of patients, and patient-administered questionnaires showed satisfaction among all patients, Ranawat said.
Long-term radiographic analysis was performed for 42 knees in 30 patients. No signs of malalignment, aseptic loosening, excessive wear or osteolysis were observed on the radiographs. However, investigators found nonprogressive demarcation in nine knees.
Ranawat and colleagues also performed Kaplan-Meyer analysis, which revealed a survivorship of 97% for mechanical failure and 92% for failure from all causes.

Literature review
During a brief literature review, Ranawat referred to four studies conducted between 1983 and 1997 that demonstrated an average 90% to 95% survivorship of all-polyethylene tibial implants at 10 to 20 years. Two other studies, conducted by Muller and colleagues in 2006 and Gioe and colleagues in 2007, provided level 1 evidence showing no difference between results with all-polyethylene tibial implant designs compared with those of metal-backed designs. Radiostereometric analysis studies also showed equal or better fixation with the all-polyethylene design.

“It is very cost-effective and, despite good scientific evidence, its penetration in the U.S. market is around 5%,” Ranawat said. “It appears that the benefit of modularity, both for surgeon and manufacturer, are overwhelming.”

Ranawat concluded by saying that all-polyethylene tibial components are best-suited for elderly patients who weigh less than 180 lbs., as well as carefully selected younger patients.

by Thomas M. Springer

References:
Font-Rodriguez DE, et al. Survivorship of cemented total knee arthroplasty. Clin Orthop Relat Res. 1997;(345):79-86.
Gioe TJ, et al. Excellent survival of all-polyethylene tibial components in a community joint registry. Clin Orthop Relat Res. 2007;(464):88-92.
Insall JN, et al. The total condylar knee prosthesis in gonarthrosis. A five to nine-year follow-up of the first one hundred consecutive replacements. J Bone Joint Surg Am. 1983;65(5):619-628.
Muller SD, et al. Should we reconsider all-polyethylene tibial implants in total knee replacement? J Bone Joint Surg Br. 2006;88(12):1596-1602.
Ranawat CS, et al. Long-term results of the total condylar knee arthroplasty. A 15-year survivorship study. Clin Orthop Relat Res. 1993;(286):94-102.
Vince KG, et al. The total condylar prosthesis. 10- to 12-year results of a cemented knee replacement. J Bone Joint Surg Br. 1989;71(5):793-797.
Ranawat CS. The all-poly tibia – a contemporary health care solution (affirms). Paper #99. Presented at the Current Concepts in Joint Replacement 2010 Winter Meeting. December 8-11, 2010. Orlando.
Chitranjan S. Ranawat, MD, can be reached at Hospital for Special Surgery, 535 E. 70th, 6th floor, New York, NY 10021; 646-797-8700;
 

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