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Tibial components for primary knee osteoarthritis

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Tibial components for primary knee osteoarthritis

Vol: 2| Issue: 2| Number:68| ISSN#: 2564-2537
Study Type:Therapy
OE Level Evidence:2
Journal Level of Evidence:N/A

Superior fixation of pegged trabecular metal over screw-fixed pegged porous titanium fiber mesh: A randomized clinical RSA study on cementless tibial components

Acta Orthop. 2011 Apr;82(2):177-86.

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50 patients were randomized to receive either high-porosity trabecular metal (TM) tibial components or low-porosity titanium pegged porous fiber-metal (Ti) components in the treatment of primary osteoarthritis of the knee. This study was performed to compare the stability of these cementless implants. The results indicated that TM tibial components migrated less than the Ti components at 1 and 2 year post-surgery follow-ups.

Publication Funding Details +
Industry funded
Zimmer Inc., Warsaw, IN, USA.
None disclosed

Risk of Bias


Reporting Criteria


Fragility Index


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.




Outcome Measurements


Inclusion / Exclusion


Therapy Description



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?

There is currently insufficient evidence regarding the efficacy of high-porosity double-pegged trabecular metal versus low-porosity titanium pegged fiber-metal as a cementless tibial component for patients suffering from primary knee osteoarthritis.

What was the principal research question?

Does a high-porosity double-pegged trabecular metal component tibial lead to improved fixation as compared to a low-porosity titanium fiber-metal tibial component in patients undergoing intervention for primary knee osteoarthritis, when measured two years post-operatively?

Study Characteristics -
50 patients undergoing intervention for primary osteoarthritis of the knee (ages 18-70)
A NexGen trabecular metal (tantalum) monobloc with two hexagonal pegs. (n=25)
A NexGen porous titanium fiber-mesh tibial metal-backing with 4 short pegs. (n=25)
Model-based Radiostereometric analysis (RSA) to assess implant migration, American Knee Society score (AKSS) to asses knee function
RCT, single-centered, Department of Orthopedics and Department of Radiology, Aarhus University Hospital, Aarhus, Denmark
2 years post-operative

What were the important findings?

  • Migration of the trabecular (TM) component was significantly less than the low-porosity titanium component. This result was significant at both the one year (p = .01) and two year follow-up (p = .004).
  • AKSS reports of both groups indicated reductions in pain at 2 year follow-up compared to preoperative scores, with 14/22 in the TI group and 17/23 in the TM group, reporting no pain.

What should I remember most?

The trabecular metal component was superior to the low-porosity titanium component in terms of total migration, measured two years postoperatively.

How will this affect the care of my patients?

This study provides support for the use of porous tantalum as an alternative to traditional implants. However, the small sample size of the study and the unknown results of longer term follow up should be considered.

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