Author Verified
RCT
ACE Report #10257

Migration of mobile- and fixed-bearing total knee system similar over 6-year follow-up


Study Type:Randomized Trial
OE Level Evidence:2
Journal Level of Evidence:N/A

Migration and clinical outcome of mobile-bearing versus fixed-bearing single-radius total knee arthroplasty

Acta Orthop. 2018 Apr;89(2):190-196

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Synopsis

48 patients scheduled for total knee arthroplasty with a single radius implant were randomized to either a mobile-bearing or fixed-bearing design. Patients were primarily followed up for tibial component migration after 6 years. Secondary outcomes also included clinical scores and knee range of motion. Results demonstrated no significant differences between groups for any of the assessed outcome measures.

Publication Funding Details +
Funding:
Industry funded
Sponsor:
Stryker
Conflicts:
None disclosed

Risk of Bias

5/10

Reporting Criteria

9/21

Fragility Index

N/A

Was the allocation sequence adequately generated?

Was allocation adequately concealed?

Blinding Treatment Providers: Was knowledge of the allocated interventions adequately prevented?

Blinding Outcome Assessors: Was knowledge of the allocated interventions adequately prevented?

Blinding Patients: Was knowledge of the allocated interventions adequately prevented?

Was loss to follow-up (missing outcome data) infrequent?

Are reports of the study free of suggestion of selective outcome reporting?

Were outcomes objective, patient-important and assessed in a manner to limit bias (ie. duplicate assessors, Independent assessors)?

Was the sample size sufficiently large to assure a balance of prognosis and sufficiently large number of outcome events?

Was investigator expertise/experience with both treatment and control techniques likely the same (ie.were criteria for surgeon participation/expertise provided)?

Yes = 1

Uncertain = 0.5

Not Relevant = 0

No = 0

The Reporting Criteria Assessment evaluates the transparency with which authors report the methodological and trial characteristics of the trial within the publication. The assessment is divided into five categories which are presented below.

1/4

Randomization

3/4

Outcome Measurements

0/4

Inclusion / Exclusion

2/4

Therapy Description

3/5

Statistics

Detsky AS, Naylor CD, O'Rourke K, McGeer AJ, L'Abbé KA. J Clin Epidemiol. 1992;45:255-65

The Fragility Index is a tool that aids in the interpretation of significant findings, providing a measure of strength for a result. The Fragility Index represents the number of consecutive events that need to be added to a dichotomous outcome to make the finding no longer significant. A small number represents a weaker finding and a large number represents a stronger finding.

Why was this study needed now?

Many studies and analyses have been conducted comparing outcomes between mobile-bearing and fixed-bearing total knee implants. However, a number of these studies were completed using older implant designs, and may not reflect the comparative efficacy of newer designs. Furthermore, specific efficacy when considering single radius implants has not been thoroughly investigated previously.

What was the principal research question?

In single-radius total knee arthroplasty, is there a significant difference in mid-term (6-year) migration between a mobile-bearing implant and a fixed-bearing implant?

Study Characteristics -
Population:
48 patients (52 knees) scheduled for cemented total knee arthroplasty.
Intervention:
MB group: Total knee arthroplasty was completed using a mobile-bearing, posterior stabilized, single-radius total knee implant (Triathlon; Stryker) (n=23; Mean age: 67.5+/-10.1)
Comparison:
FB group: Total knee arthroplasty was completed using a fixed-bearing, posterior stabilized, single-radius total knee implant (Triathlon; Stryker) (n=23; Mean age: 68.0+/-9.6)
Outcomes:
The primary outcome was maximum total point motion of the tibial component, measured using radiostereometric analysis (RSA). Clinical measures included the Knee Society Knee and Function Scores and knee range of motion. The incidence of complications was also recorded.
Methods:
RCT; Single center
Time:
The follow-up in this study was 6 years postoperatively.

What were the important findings?

  • Maximum total point motion at 6 years did not significantly differ between the MB group (1.22mm [95%CI 0.75-1.80]) and the FB group (0.90mm [95%CI 0.49-1.41]) (p=0.30).
  • Change in range of knee flexion after 6 years did not significantly differ between the MB group and the FB group (p=0.2).
  • Change in range of knee extension after 6 years did not significantly differ between the MB group and the FB group (p=0.2).
  • Change in Knee Society Knee Scores after 6 years did not significantly differ between the MB group and the FB group (p=0.7).
  • Change in Knee Society Function Scores after 6 years did not significantly differ between the MB group and the FB group (p=0.2).
  • Revision due to aseptic loosening was performed in no patients of the MB group and 1 patient of the FB group. Revision due to septic loosening was performed in 1 patient of the MB group and 1 patients of the FB group.
  • Recruitment was stopped early due to the investigation of one case of mobile bearing insert dislocation.

What should I remember most?

In single-radius total knee arthroplasty, no significant differences in 6-year tibial migration, clinical outcome or revision rate were observed between cases completed using a mobile-bearing design and cases completed using a fixed-bearing design.

How will this affect the care of my patients?

The results of this study suggest that mid-term migration and clinical outcome is similar between mobile-bearing and fixed-bearing single-radius total knee implants. Therefore, it is unknown if there is any clear advantage of one design over the other.

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