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      Flexion contracture can cause component mismatch in the Prophecy ® preoperative patient-specific instrumentation for Evolution ® medial-pivot knee system


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          Introduction: Patient-specific instrumentation (PSI) systems are used to conduct total knee arthroplasty. PSI reduces operative time, is less invasive and easier to use, and minimizes the risk of errors by providing precise measurements and reducing operating room turnover time. However, a study on the accuracy of Prophecy Evolution PSI (Microport Inc., Arlington, TN, USA) reported that 94% were below the error margin of 1.5 mm and 90% had error margins of 1 mm. This study aimed to evaluate the accuracy of the Prophecy Evolution PSI system in terms of the thickness of “total” bony resection required to achieve adequate extension/flexion gaps and the component match ratio between preoperative planning and actual component size inserted. Methods: Comparisons were made between the sizes of femoral and tibial components planned with PSI and those inserted. The primary outcome was the average preoperative range of motion with and without matched femoral/tibial components. The study further analyzed the proportions of cases in which both the femoral and tibial components matched, neither matched, and only one of the femoral or tibial components matched. Results: The ratio of the same sizes between the PSI planning and those inserted was 50.8% (33 patients) for both the femoral and tibial components. For the femoral component alone, the ratio was 84.6% (55 patients), and for the tibial component, it was 58.4% (38 patients). A receiver-operating characteristic curve analysis indicated that flexion contracture greater than 20° was a significant prognostic factor for the PSI component match group versus the mismatch group. Discussion: Flexion contracture may cause PSI mismatch. Notably, flexion contracture greater than 20° was a significant risk factor for the PSI component match group versus the mismatch group. During preoperative planning for a patient with flexion contracture, surgeons should prepare for the possibility of inserting an undersized tibial component.

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          Most cited references28

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          G*Power 3: A flexible statistical power analysis program for the social, behavioral, and biomedical sciences

          G*Power (Erdfelder, Faul, & Buchner, 1996) was designed as a general stand-alone power analysis program for statistical tests commonly used in social and behavioral research. G*Power 3 is a major extension of, and improvement over, the previous versions. It runs on widely used computer platforms (i.e., Windows XP, Windows Vista, and Mac OS X 10.4) and covers many different statistical tests of the t, F, and chi2 test families. In addition, it includes power analyses for z tests and some exact tests. G*Power 3 provides improved effect size calculators and graphic options, supports both distribution-based and design-based input modes, and offers all types of power analyses in which users might be interested. Like its predecessors, G*Power 3 is free.
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            A prospective randomised controlled study of patient-specific cutting guides compared with conventional instrumentation in total knee replacement.

            Patient-specific cutting guides (PSCGs) are designed to improve the accuracy of alignment of total knee replacement (TKR). We compared the accuracy of limb alignment and component positioning after TKR performed using PSCGs or conventional instrumentation. A total of 80 patients were randomised to undergo TKR with either of the different forms of instrumentation, and radiological outcomes and peri-operative factors such as operating time were assessed. No significant difference was observed between the groups in terms of tibiofemoral angle or femoral component alignment. Although the tibial component in the PSCGs group was measurably closer to neutral alignment than in the conventional group, the size of the difference was very small (89.8° (sd 1.2) vs 90.5° (sd 1.6); p = 0.030). This new technology slightly shortened the bone-cutting time by a mean of 3.6 minutes (p < 0.001) and the operating time by a mean 5.1 minutes (p = 0.019), without tangible differences in post-operative blood loss (p = 0.528) or need for blood transfusion (p = 0.789). This study demonstrated that both PSCGs and conventional instrumentation restore limb alignment and place the components with the similar accuracy. The minimal advantages of PSCGs in terms of consistency of alignment or operative time are unlikely to be clinically relevant.
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              The value of patient-matched instrumentation in total knee arthroplasty.

              The purpose of the current prospective, randomized study was to compare the value of a new mechanically aligned patient-matched instrument system for total knee arthroplasty (TKA) (Visionaire; Smith & Nephew, Inc, Memphis, Tenn) (VIS) to that of standard TKA surgical instrumentation (STD). Twenty-nine primary TKA patients were enrolled and completed surgery (15 VIS and 14 STD). Postoperatively, mechanical alignment was significantly closer to neutral zero in the VIS group (1.7° vs 2.8°; P = .03). Furthermore, the VIS group demonstrated significant reductions in duration of hospital stay, operative time, incision length, and number of used instrument trays (P < .05). Although additional research is underway to confirm these preliminary results, this evidence suggests that patient-matched instrumentation may support repeatable improvements in surgical accuracy and hospital efficiency.

                Author and article information

                SICOT J
                SICOT J
                EDP Sciences
                09 April 2024
                : 10
                : 12
                [1 ] Department of Orthopedics, Jichi Medical University 3311-1 Yakushiji Shimotsuke Tochigi 329-0498 Japan
                [2 ] Department of Orthopedics, Ishibashi General Hospital 1-15-4 Shimokoyama Shimotsuke 329-0502 Japan
                Author notes
                [* ]Corresponding author: tsuneari9@ 123456jichi.ac.jp
                Author information
                sicotj230112 10.1051/sicotj/2024009
                © The Authors, published by EDP Sciences, 2024

                This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                : 28 December 2023
                : 10 March 2024
                Page count
                Figures: 2, Tables: 3, Equations: 0, References: 26, Pages: 6
                Funded by: Microport
                Original Article

                prophecy evolution medial-pivot patient-specific instrumentation (psi),total knee arthroplasty (tka),accuracy,component match ratio,medial pivot knee system


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