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TKA: Press-fit condylar prosthesis superior to continuum knee system prosthesis

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TKA: Press-fit condylar prosthesis superior to continuum knee system prosthesis

Vol: 2| Issue: 2| Number:151| ISSN#: 2564-2537
Study Type:Therapy
OE Level Evidence:2
Journal Level of Evidence:N/A

Similar TKA designs with differences in clinical outcome: A randomized, controlled trial of 77 knees with a mean follow-up of 6 years

Acta Orthop. 2011 Dec;82(6):685-91. Epub 2011 Nov 9

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82 patients (90 knees) with either osteo- or rheumatoid arthritis requiring total knee arthroplasty (TKA) were randomized to receive the continuum knee system prosthesis (CKS) or the press-fit condylar prosthesis (PFC) to determine if differences were present in clinical outcomes. A mean follow-up of 5.6 years indicated that use of the PFC prosthesis resulted in superior Knee Society scores (KSS), a decreased revision rate, and better implant survival when compared to the CKS prosthesis.

Publication Funding Details +
Not Reported
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?

The development and introduction of new prostheses for total knee arthroplasty (TKA) is an ongoing process with the ultimate goal of improving survival rates, range of motion, and the anatomical reconstruction of the joint. The use of a continuum knee system prosthesis (CKS) has recently been advocated as a good alternative to the standard press-fit condylar prosthesis (PFC). However, a recent retrospective analysis reported that TKA using the CKS prosthesis tended to produce worse results, indicating the need for a randomized trial to compare the effectiveness of both the CKS and PFC prostheses.

What was the principal research question?

Did the minor differences in design between the continuum knee system (CKS) prosthesis and the press-fit condylar (PFC) prosthesis result in different clinical outcomes of patients undergoing total knee arthroplasty, measured over a 6 year follow-up period?

Study Characteristics -
90 knees (82 patients) with osteo- or rheumatoid arthritis, requiring total knee replacement surgery.
Continuum knee system prosthesis (CKS prosthesis) (Stratec Medical, Oberdorf, Switzerland) (n=45 knees).
Press-fit condylar prosthesis (PFC prosthesis) (DePuy/Johnson and Johnson, Warsaw, IN) (n=45 knees).
The primary outcome was the difference between groups in the total Knee Society score (KSS). Secondary outcomes included KSS subscore results, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score, range of motion, survival (any re-operation), and patient satisfaction as well as pain (both measured using VAS). Any re-operations or revisions were recorded.
Randomized controlled trial
Follow up at 3 months, 6 months, and 1 year, with a 6 year final follow up.

What were the important findings?

  • At final follow up, a significant difference was observed between groups in favour of the PFC prosthesis group, with respect to the KSS primary outcome measure (p=0.04).
  • The PFC group showed a trend towards superior results in terms of the KSS scores, WOMAC score, range of motion, patient satisfaction and pain compared to the CKS group.
  • At the final follow up period, the KSS knee subscore and VAS satisfaction values were in favour of the PFC treatment group (p=0.04 for both outcomes).
  • 1 revision occurred in the PFC group compared to 6 revisions in the CKS group (p=0.1).
  • The survival analysis (with re-operation as the endpoint) showed there was better survival in patients that received the PFC prosthesis: 97% (95% CI 92-100) for the PFC prosthesis and 79% (95% CI 66-92) for CKS prosthesis (p=0.02).

What should I remember most?

Use of the PFC prosthesis resulted in superior KSS scores, decreased revision rate and better survival in comparison to the CKS prosthesis group at a mean of 5.6 years.

How will this affect the care of my patients?

This study demonstrates that TKA using the PFC prosthesis may result in superior clinical outcomes (KSS) and greater patient satisfaction when compared to the CKS prosthesis. These results should be taken under consideration when contemplating the use of the CKS prosthesis.

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