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RCT
ACE Report #36

Coatings for femoral stems


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

Excessive distal migration of fiber-mesh coated femoral stems

Acta Orthop. 2011 Jun;82(3):308-14. Epub 2011 Apr 19

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Synopsis

50 arthritic patients undergoing total hip arthroplasty were randomized to receive either distally tapered, extended coated stems, or straight proximally coated stems, to study potential differences in implant migration. At 2 years post-surgery, radiostereometric analysis revealed that both stem types demonstrated large amounts of implant migration, with no significant differences between groups.

Publication Funding Details +
Funding:
Industry funded
Sponsor:
Zimmer, Warsaw, IN.
Conflicts:
None disclosed

Risk of Bias

6.5/10

Reporting Criteria

19/20

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.

4/4

Randomization

3/4

Outcome Measurements

4/4

Inclusion / Exclusion

4/4

Therapy Description

4/4

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?

The varying types of femoral stem coatings used for total hip arthroplasty have been investigated in studies to determine implant migration and rotation. This study aims to further investigate the outcomes with respect to extended coating versus proximal coating.

What was the principal research question?

Does an extended coated stem lead to reduced implant migration two years postoperatively, when compared to a proximally coated stem in patients undergoing total hip arthroplasty for primary osteoarthritis?

Study Characteristics -
Population:
50 patients with a median age of 60 undergoing total hip arthroplasty for primary hip osteoarthritis.
Intervention:
Distally tapered, extended coated stem (VerSys Fiber Metal Taper Hip Prosthesis) (n=20)
Comparison:
Straight, proximally coated stem (VerSys Fiber Metal MidCoat Hip Prosthesis) (n=21)
Outcomes:
Radiostereometric analysis
Methods:
RCT; Single-centered
Time:
24 month follow-up

What were the important findings?

  • no statistically significant difference during RSA assessment with respect to rotation or translation detected between groups at any of the follow-up points
  • implant migration of both groups was significant from initial postoperative measurements

What should I remember most?

Both implant stem groups demonstrated significant migration in comparison to baseline measures; however, no statistically significant difference was detected between the groups. The authors recommend that additional follow-ups are required in future trials.

How will this affect the care of my patients?

Both implants demonstrate significant migration,which warrants further investigation; however, this trial was unable to conclude which coating is superior. Additionally, the authors cite this study as an evidence for the necessity of RSA, as standard protocol to monitor all new implants.

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