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No difference in rate of malalignment between PSI and conventional instruments in TKA
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June 2018
No difference in rate of malalignment between PSI and conventional instruments in TKA
Study Type:Randomized Trial
OE Level Evidence:2
Journal Level of Evidence:N/A
No radiological and clinical advantages with patient-specific positioning guides in total knee replacement
Acta Orthop. 2018 Feb;89(1):89-94Did you know you're eligible to earn 0.5 CME credits for reading this report? Click Here
Synopsis
109 patients scheduled for total knee arthroplasty were randomized to surgery with either the use of patient-specific cutting guides or conventional intra- and extramedullary guides. Patients were assessed for overall lower limb alignment, femoral component alignment in the coronal, sagittal, and axial planes, tibial component alignment in the coronal and sagittal planes, and patient-reported outcome measures and knee range of motion over a 2-year follow-up. Results demonstrated no statistically significant differences between groups in the rate of outliers (>3deg deviation from planned alignment) in any alignment comparison, or in any patient-reported outcome measure or range of motion over a 2-year follow-up.
Publication Funding Details
+
Funding:
Non-funded
Conflicts:
None disclosed
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.
2/4
Randomization
2/4
Outcome Measurements
4/4
Inclusion / Exclusion
4/4
Therapy Description
4/5
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?
When first introduced, there was a lot of interest in patient-specific instruments as a method to potentially improve the alignment of components in total knee arthroplasty. As randomized controlled trials have been published on their use, mixed evidence in support of their efficacy has been reported. There is a continued need for high-quality studies on their use in order to determine their role in routine practice for total knee arthroplasty.
What was the principal research question?
In total knee arthroplasty, is there any significant difference in mean component alignment, the incidence of outliers in component alignment (>3deg deviation from planned alignment), or patient-reported outcome measures, over 2 years postoperatively between patient-specific instrumentation and convention instruments?
Study Characteristics
-
Population:
109 patients scheduled for total knee arthroplasty due to knee osteoarthritis. All cases were completed using a medial parapatellar approach and the same cemented total knee implant (Vanguard Cruciate Retaining Knee; Biomet Inc.).
Intervention:
PSI group: Patient-specific cutting guides were manufactured from preoperative MRI scans, with femoral rotation set relative to the surgical epicondylar axis, femoral flexion set at 3 degrees, and tibial slope set at 3 degrees. (n=44; Mean age: 67+/-8.8)
Comparison:
CONV group: Femoral resection was aided with the use of a standard intramedullary guide, and tibial resection with a standard extramedullary guide. (n=50; Mean age: 64+/-6.9)
Outcomes:
Full weight-bearing radiographs were used to measure the hip-knee-ankle angle, while CT was used to measure the coronal angles of the tibial and femoral components, the sagittal angles of the tibial and femoral components, and axial alignment of the femoral component. Component outliers were defined as alignment exceeding 3-degree deviation from planned alignment. Clinical scores included the Knee Injury and Osteoarthritis Outcome Score (KOOS), pain on a numeric rating scale, and the EuroQol 5-dimensions health survey (EQ-5D). The range of motion was also measured.
Methods:
RCT; Multicenter (3 sites)
Time:
Imaging was performed at 3 months postoperatively. Clinical measures were assessed at 3 months, 1 year, and 2 years postoperatively.
What were the important findings?
- The incidence of femoral outliers did not significantly differ between the PSI group and the CONV group in the coronal plane (7/43 vs. 4/47; p=0.3), sagittal plane (29/43 vs. 23/47; p=0.08), or axial plane (5/43 vs. 7/47; p=0.7).
- The incidence of tibial outliers did not significantly differ between the PSI group and the CONV group in the coronal plane (8/43 vs. 3/47; p=0.08) or the sagittal plane (17/43 vs. 26/47; p=0.1).
- The incidence of outliers in HKA angle (reference: neutral alignment) did not significantly differ between the PSI group and the CONV group (11/42 vs. 11/49; p=0.7).
- No significant differences between the PSI group and the CONV group were observed in KOOS scores, NRS pain scores, EQ-5D scores, or knee range of motion in flexion and extension at 3 months, 1 year, or 2 years (all p>0.05).
What should I remember most?
In total knee arthroplasty, there were no significant differences between cases completed using patient-specific instruments and cases completed using standard intra- and extramedullary guides in rate of overall lower limb malalignment, rate of malalignment of either the femoral component or tibial component individually, or in patient-reported outcome measured and knee range of motion over 2 year follow-up.
How will this affect the care of my patients?
The results of this study suggest that there does not appear to be a clinical benefit to the use of patient-specific instruments over conventional instruments in completing total knee arthroplasties.
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Orthopaedic Surgeon - Canada
If clinically results of both instrumentations are equals, as most of the studies on that topic suggest, at this time of cost containment which one should we cho$e...