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Trabecular metal cementless implants lead to improved knee scores following TKA

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Author Verified

Trabecular metal cementless implants lead to improved knee scores following TKA

Vol: 3| Issue: 2| Number:31| ISSN#: 2564-2537
Study Type:Therapy
OE Level Evidence:1
Journal Level of Evidence:N/A

Trabecular metal in total knee arthroplasty associated with higher knee scores: a randomized controlled trial

Clin Orthop Relat Res. 2013 Nov;471(11):3543-53

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Synopsis

145 patients, between the ages of 50 and 70 years, who were admitted for primary TKA and who had moderate to severe femorotibial gonarthrosis were randomly assigned into 1 of 2 groups to compare the efficacy of a tibial component fixed by a porous tantalum system to a conventional cemented implant in terms of clinical outcomes, complications/reoperations, and radiographic results. The findings of the study indicate that at the 5 year follow-up mean KSS and mean WOMAC scores were significantly better in the cementless group when compared to the cemented group. However, no differences in frequency of complications or aseptic loosening between the two groups were found.

Publication Funding Details +
Funding:
Industry funded
Sponsor:
Zimmer GmbH, Winterthur, Switzerland.
Conflicts:
Other

Risk of Bias

8/10

Reporting Criteria

20/20

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

4/4

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?

TKA has become a widely accepted procedure for reducing pain and improving function in patients who are experiencing physical limitations of the knee/leg. Currently, cemented TKA is the accepted standard for TKA consistently providing predictable and durable results, but certain restrictions/limitations with this procedure have led to further development of alternative techniques. Cementless fixation seeks to address the common issue of aseptic failure in patients with cemented fixation (especially in younger individuals), and increased durable biological fixation with more physiologic transfer of stress to the underlying bone. Early results with cementless implants showed promising results with achieving these goals, but a wide variety of complications and failures occurred. Tantalum, a newer biomaterial that mimics cancellous bone, may be able to overcome the issues that occurred with previous cementless implants.

What was the principal research question?

Does a tibial component fixed by a porous tantalum system achieve better clinical outcomes, fewer complications/reoperations, and improved radiographic results when compared to a conventional cemented implant?

Study Characteristics -
Population:
145 patients, between the ages of 50 and 70 years, who were admitted for primary TKA and who had moderate to severe femorotibial gonarthrosis.
Intervention:
Group 1 (Cementless): Patients in this group received an uncemented fiber metal femoral component (NexGen; Zimmer Inc.) and an uncemented Trabecular Metal monoblock tibial component. The uncemented porous tantalum tibial component was designed to have the polyethylene intruded directly into the porous tantalum tray with two Trabecular Metal hexagonal-shaped pegs on its undersurface that are press-fitted into the tibial spongosia. (Mean age: 61 +/- 5.0, n=74, 69 completed follow up, M=19/F=55)
Comparison:
Group 2 (Cemented): Patients in this group received a hybrid TKA using the same uncemented femoral component and a cemented NexGen stemmed tibial component (made of titanium alloy with a 50-mm central stem with small posterolateral flanges). Prostheses were inserted in a conventional fashion (Mean age: 60 +/- 4.6, n=71, 63 completed follow up, M=17/F=54)
Outcomes:
Primary Outcome: Knee Society Score (KSS). Secondary Outcomes: Spanish adaptation of WOMAC, complications, reoperations, and radiographic failures.
Methods:
RCT; Single Center: Double-Blinded
Time:
5 years (Outcomes were assessed preoperatively, and 15 days, 6 months, and 5 years after surgery completion).

What were the important findings?

  • Patients who received Cementless tibia implants exhibited improved KSS and WOMAC scores when compared to those who received the cemented implants.
  • At 5 year follow up mean KSS score was 90.4 in Group 1 and 86.5 in Group 2, a significant difference in favour of the Cementless group (p=0.02). Effect size at 95% CI for difference between the means was 3.88 +/- 2.87.
  • At 5 year follow up the WOMAC mean was 15.1 in Group 1 and 19.1 in Group 2, a significant difference in favour of the Cementless implant group (p=0.02). Effect size at 95% CI for difference between the means was -4.0 +/- 3.9.
  • Average KSS and WOMAC scores reported at 6 months and 5 years post operatively were significantly improved from preoperative levels in both groups (p<0.001 at both follow ups for both outcomes)
  • No differences between groups in terms of frequency of complications or reoperations were found by final follow up. In total 10% of Group 1 patients and 14% of Group 2 patients underwent additional procedures for complications, most of which were manipulations under anesthesia.
  • Radiographic analysis showed no difference in radiologic alignment at 5 years between the groups, and no changes in component position or osteolysis were found during the follow up period. Two patients in group 1 had progressive radiolucent lines under the anterior flange of their femoral component, but zero patients (in either group) experienced progressive radiolucent lines around the tibial component or aseptic loosening.

What should I remember most?

At 5 year follow up KSS mean and mean WOMAC scores were significantly better in the cementless group when compared to the cemented group. There were no differences in frequency of complications or aseptic loosening between the two groups.

How will this affect the care of my patients?

The results of the study suggest that there are statistically significant differences between uncemented porous tantalum tibial components and conventional cemented tibial components in terms of knee function score, in favour of uncemented treatment. Further research determining if the difference in results outweighs the cost increase of the cementless treatment is needed.

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