Migration and clinical outcome of mobile-bearing versus fixed-bearing single-radius total knee arthroplasty
A randomized controlled trial
K. T. Van Hamersveld (Leiden University Medical Center)
Perla Jacqueline Marang-van de Mheen (Leiden University Medical Center)
Huub J.L. Van Der Heide (Leiden University Medical Center)
Henrica M.J. Van Der Linden-Van Der Zwaag (Leiden University Medical Center)
E.R. Valstar (Leiden University Medical Center)
Rob G.H.H. Nelissen (Leiden University Medical Center)
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Abstract
Background and purpose — Mobile-bearing total knee prostheses (TKPs) were developed in the 1970s in an attempt to increase function and improve implant longevity. However, modern fixed-bearing designs like the single-radius TKP may provide similar advantages. We compared tibial component migration measured with radiostereometric analysis (RSA) and clinical outcome of otherwise similarly designed cemented fixed-bearing and mobile-bearing single-radius TKPs. Patients and methods — RSA measurements and clinical scores were assessed in 46 randomized patients at baseline, 6 months, 1 year, and annually thereafter up to 6 years postoperatively. A linear mixed-effects model was used to analyze the repeated measurements. Results — Both groups showed comparable migration (p = 0.3), with a mean migration at 6-year follow-up of 0.90 mm (95% CI 0.49–1.41) for the fixed-bearing group compared with 1.22 mm (95% CI 0.75–1.80) for the mobile-bearing group. Clinical outcomes were similar between groups. 1 fixed-bearing knee was revised for aseptic loosening after 6 years and 2 knees (1 in each group) were revised for late infection. 2 knees (1 in each group) were suspected for loosening due to excessive migration. Another mobile-bearing knee was revised after an insert dislocation due to failure of the locking mechanism 6 weeks postoperatively, after which study inclusion was preliminary terminated. Interpretation — Fixed-bearing and mobile-bearing single-radius TKPs showed similar migration. The latter may, however, expose patients to more complex surgical techniques and risks such as insert dislocations inherent to this rotating-platform design.
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