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Volume:1 Issue:3 Number:153 ISSN#:2563-5476
RCT
ACE Report #3122

THA: Less transverse rotation of tantalum trabecular metal acetabular cup


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

Comparison of trabecular metal cups and titanium fiber-mesh cups in primary hip arthroplasty: A randomized RSA and bone mineral densitometry study of 50 hips

Acta Orthop. 2011 Apr;82(2):155-60. Epub 2011 Mar 25

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Synopsis

60 patients with noninflammatory hip arthritis were randomized to receive either a tantalum trabecular metal acetabular cup or titanium fiber-mesh cup, as part of the primary hip arthroplasty surgical procedure. The primary endpoint was cup migration. Bone mineral density and the Harris hip score were also evaluated. Results indicated positive early results with the tantalum trabecular metal cup on fixation outcomes, as well as comparable results on the secondary endpoint outcomes. A longer observation period is recommended to examine the effects over a longer time period.

Publication Funding Details +
Funding:
Industry funded
Sponsor:
Zimmer Inc.
Conflicts:
None disclosed

Risk of Bias

6/10

Reporting Criteria

16/20

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

3/4

Inclusion / Exclusion

2/4

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?

Initial stability is critical for an implant to achieve bone ingrowth. A number of clinical studies have shown good outcomes in bone ingrowth with trabecular metal. However, no published studies have examined this relationship with radiostereometric analysis (RSA). This study compares tantalum trabecular metal acetabular cups and titanium fiber-mesh cups in primary hip arthroplasty.

What was the principal research question?

What are the outcomes in cup migration, bone mineral density, and Harris hip scores with tantalum trabecular metal acetabular cups compared to titanium fibermesh cups, in patients with noninflammatory hip arthritis undergoing primary hip arthroplasty at 2 years?

Study Characteristics -
Population:
60 patients with noninflammatory hip arthritis (Male: 34, Female: 26) (Age: 52-76 years; Median: 62 years)
Intervention:
Tantalum trabecular metal acetabular cup (Monoblock cup, Zimmer) (n=30)
Comparison:
Uncemented cup with a titanium fiber-mesh surface (Trilogy cup, Zimmer) (n=30)
Outcomes:
Primary endpoint: cup migration within 2 years (early implant loosening) (Radiostereometric analysis); Secondary endpoints: change in bone mineral density, and change in Harris hip score (HHS) at 3 months
Methods:
RCT
Time:
2 years

What were the important findings?

  • Radiostereometric analysis (RSA) indicated minimal rotation and translation at the 2-year follow-up. No statistically significant difference was seen between the two groups on translation. The trabecular tantalum surface cups (Monoblock) had less rotation on the transverse axis compared to the titanium fiber-mesh cup (Trilogy) (Monoblock: Mean -0.01 degrees [95%CI: -0.11 to 0.12]; Trilogy: Mean -0.60 degrees [95%CI: -0.72 to -0.48]) (p=0.04)
  • Both groups reported a similar increase in Harris hip score at 3 months postoperatively from a score of 50 (28-70) to 92 (76-100) in the tantalum group and from 48 (34-64) to 95 (77-100) in the Trilogy group
  • Both groups had similar degrees of reduction in bone mineral density

What should I remember most?

Positive early results were seen for both implant cups in terms of fixation onto the acetabular host bone. RSA revealed both groups had minimal rotation and translation (with less rotation on the transverse axis for the tantalum group). Results also indicated similar reduction in bone mineral density and similar increase in Harris hip score.

How will this affect the care of my patients?

A study with a longer observation period is recommended to determine the long-term outcomes of the tantalum trabecular metal acetabular cups.

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