No radiographic or clinical benefit of patient specific instrumentation in TKA
Patient-specific instrumentation does not improve radiographic alignment or clinical outcomes after total knee arthroplastyActa Orthop. 2016 Aug;87(4):386-94
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21 studies evaluating the use of patient-specific instrumentation in total knee arthroplasty were included in this meta-analysis and systematic review. Pooled analyses demonstrated no significant difference between patient-specific instrumentation systems and conventional instruments in the incidence of excessive malalignment (>3 degrees deviation) in hip-knee-ankle angle. Additionally, the incidence of femoral component outliers in the coronal, sagittal, and axial planes, and tibial component outliers in the sagittal plane did not significantly differ, while tibial component outliers in the coronal plane occurred significantly more often with patient-specific instrumentation. No significant differences were found in short-term (3-month) clinical outcome measures. Two analyses which did favour patient-specific instrumentation were a lower number of surgical trays required during the procedure and shorter length of stay.
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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?
Patient-specific instrumentation (PSI) for component implantation in total knee arthroplasty is a recently-developed technology, with a number of randomized controlled trials performed investigating the systems of major orthopaedic device companies. PSI systems were designed to improve component alignment in these procedures, though conclusions on efficacy from previous studies vary widely. A synthesis of the literature was therefore needed to assess the current status of the role of PSI in TKA procedures.
What was the principal research question?
In total knee arthroplasty, are there any significant differences in radiographic alignment accuracy of component placement, perioperative parameters (blood loss, operative time, etc), and patient-reported outcome measures between patient-specific instrumentation and conventional instrumentation?
What were the important findings?
- There was no significant difference in the incidence of outliers in hip-knee-ankle angle (>3deg deviation from neutral) overall between patient-specific and conventional instruments (13 studies; RR 1.02 [95%CI 0.82-1.27]; p=0.86), or when specific products (PSI-Zimmer, Signature-Biomet, TruMatch-DePuy, Visionaire-Smith & Nephew) were analyzed as subgroups (all p>0.05).
- There was no significant difference between groups in the incidence of femoral component outliers in the coronal plane (11 studies; RR 0.81 [95%CI 0.6-1.09]). The incidence of tibial component outliers in the coronal plane was significantly higher among patient specific groups (11 studies; RR 1.64 [95%CI 1.12-2.42]).
- There were no significant differences between groups in the incidence of outliers in the sagittal plane of either the femoral component (8 studies; RR 0.97 [95%CI 0.82-1.15]) or the tibial component (8 studies; RR 1.47 [95%CI 0.97-2.23]).
- There was no significant difference between groups in the incidence of femoral component rotational outliers (6 studies; RR 0.80 [95%CI 0.52-1.23]).
- No significant difference between patient-specific and conventional instrumentation groups was observed in operative time (12 studies; MD -0.90min [95%CI -4.78, 2.98]; p=0.65) or tourniquet time (3 studies; MD -6min [95%CI -21.2, 10.1]). No significant differences were observed in analyses of intra-, postoperative, and total perioperative blood loss.
- The length of hospital stay was shortened by 8 hours (95%CI 3.1-12.5) following the use of patient-specific instrumentation versus conventional instrumentation.
- Two studies demonstrated a significantly lower use of surgical trays (MD 4 trays [95%CI 2.58-5.61]) with patient-specific versus conventional instrumentation.
- No significant differences between groups were observed in patient-reported outcome measures at 3 months, including Knee Society Scores and Oxford Knee Scores.
What should I remember most?
In total knee arthroplasty, the use of patient-specific instrumentation did not significantly reduce the incidence of malalignment overall, or of individual components in the coronal, sagittal, and axial planes. In fact, the incidence of tibial component outliers in the coronal plane was significantly higher following TKA with patient-specific instrumentation. No significant differences were observed in analyses of operative time, blood loss, or short-term clinical outcome. Advantages with the use of patient-specific instrumentation were noted concerning the number of surgical trays during the procedure, as well as in length of hospital stay.
How will this affect the care of my patients?
The results of this study suggest that there is no radiographic or clinical advantage to the use of patient-specific instrumentation in total knee arthroplasty, and in fact may compromise alignment of the tibial component. Benefits of patient-specific instrumentation appear limited to parameters of resource consumption, as evidenced by the analyses on surgical trays and the short, but significant, reduction in hospital stay. An economic analysis is needed to determine if these improvements in efficiency off-set the cost of the patient-specific instrumentation technology itself, as well as the preoperative imaging required to make the technology.
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