Current Data Does Not Support Routine Use of Patient-Specific Instrumentation in Total Knee Arthroplasty Pramod B. Voleti MD, Mathew Hamula BS, Keith D. Baldwin MD, MPH, MSPT, Gwo-Chin Lee MD PII: DOI: Reference:
S0883-5403(14)00345-3 doi: 10.1016/j.arth.2014.01.039 YARTH 54000
To appear in:
Journal of Arthroplasty
Received date: Revised date: Accepted date:
16 August 2013 18 December 2013 5 January 2014
Please cite this article as: Voleti Pramod B., Hamula Mathew, Baldwin Keith D., Lee Gwo-Chin, Current Data Does Not Support Routine Use of Patient-Specific Instrumentation in Total Knee Arthroplasty, Journal of Arthroplasty (2014), doi: 10.1016/j.arth.2014.01.039
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT Current Data Does Not Support Routine Use of Patient-Specific Instrumentation in Total Knee Arthroplasty
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Pramod B. Voleti, MD1 Mathew Hamula, BS1 Keith D. Baldwin, MD, MPH, MSPT1 Gwo-Chin Lee, MD1
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Department of Orthopaedic Surgery Hospital of the University of Pennsylvania 3400 Spruce Street, 2 Silverstein Philadelphia, PA 19104, USA
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Corresponding Author:
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Gwo-Chin Lee, MD Assistant Professor Department of Orthopaedic Surgery Hospital of the University of Pennsylvania 3400 Spruce Street, 2 Silverstein Philadelphia, PA 19104, USA Telephone: 215-349-8689 Fax: 215-349-5128 E-mail: [email protected]
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ACCEPTED MANUSCRIPT Abstract The purpose of this systematic review and meta-analysis is to compare patient-
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specific instrumentation (PSI) versus standard instrumentation for total knee arthroplasty
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(TKA) with regard to coronal and sagittal alignment, operative time, intraoperative blood loss, and cost. A systematic query in search of relevant studies was performed, and the
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data published in these studies were extracted and aggregated. In regard to coronal
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alignment, PSI demonstrated improved accuracy in femorotibial angle (FTA) (p = 0.0003), while standard instrumentation demonstrated improved accuracy in hip-knee-
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ankle angle (HKA) (p = 0.02). Importantly, there were no differences between treatment groups in the percentages of FTA or HKA outliers (> 3 degrees from target alignment) (p
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= 0.7). Sagittal alignment, operative time, intraoperative blood loss, and cost were also similar between groups (p > 0.1 for all comparisons). Given these results, current data
Keywords
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does not support routine use of patient-specific instrumentation in total knee arthroplasty.
patient-specific instrumentation; patient-specific guides; custom cutting guides; total knee arthroplasty instrumentation; primary total knee arthroplasty
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ACCEPTED MANUSCRIPT Introduction Total knee arthroplasty (TKA) is one of the most commonly performed
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musculoskeletal procedures in the United States with approximately 719,000 performed
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annually [1]. Given projected increases in population size and longevity, the incidence of TKA is predicted to rise in the future, reaching an estimated 3.48 million by 2030 [2].
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Perfecting surgical technique for TKA is therefore of paramount importance.
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In recent years, there has been an increased focus on the influence of limb alignment and component position on longevity and outcomes after TKA [3].
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Technological advancements aimed at improving limb alignment and component position include computer-assisted surgery (CAS) and patient-specific instrumentation (PSI).
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Meta-analyses comparing CAS versus conventional TKA have demonstrated mixed results with regard to component orientation and mechanical axis [4, 5] with no
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difference in functional outcomes [6]. The drawbacks of CAS include difficulty with accurate intraoperative landmark registration, increased set-up and operative time, increased perioperative cost, risk of pin loosening and pin-site fracture, and a substantial learning curve [7, 8].
Patient-specific instrumentation (PSI) was introduced with the goals of improving alignment through preoperative navigation, reducing operative time by minimizing intraoperative decision making, and decreasing perioperative cost by limiting the number of instrument trays required per procedure. This technology employs advanced imaging (MRI or CT) to generate an ideal cutting guide based on the patient’s anatomic parameters. Both femoral and tibial cutting guides are generated; these guides determine the location of the bone cuts; the size, position, and rotation of the components; and the
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ACCEPTED MANUSCRIPT alignment of the limb. In recent years, several comparative studies and randomized controlled trials that compare patient-specific versus standard TKA instrumentation have
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been published. Individually, these studies have failed to substantiate the theoretical
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benefits of PSI. To our knowledge, no systematic review or meta-analysis of these studies has been performed.
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Therefore, the purpose of this study is to perform a systematic review and meta-
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analysis of the current evidence comparing standard instrumentation to patient-specific instrumentation for TKA with regard to: (1) coronal alignment, (2) sagittal alignment, (3)
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operative time, (4) intraoperative blood loss, (5) transfusion requirement, and (6)
Materials and Methods
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perioperative cost.
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We performed a systematic query using both the Medline and Embase computerized literature databases in search for articles containing the keyword terms “total knee arthroplasty” and “patient-specific.” The search was performed on May 1, 2013, and all studies published prior to that date were considered. In addition to this primary search, we performed a secondary search by scrutinizing all references cited in the articles retrieved from the primary search in order to identify additional studies of interest. Three independent evaluators reviewed all articles retrieved from the primary and secondary searches using the systematic strategy outlined below. The evaluators were blinded with regard to the determinations of the other evaluators. Studies were included in the systematic review and meta-analysis if they met the following criteria: (1) they compared patients who underwent TKA with standard
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ACCEPTED MANUSCRIPT instrumentation to those who underwent TKA with patient-specific instrumentation and (2) they reported post-operative coronal alignment, post-operative sagittal alignment,
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operative time, intraoperative blood loss, transfusion requirement, and/or perioperative
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cost. Review articles, technique descriptions, and editorials were excluded. The initial combined Medline and Embase search using the aforementioned
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keyword terms yielded 207 unique articles. The titles of these studies were independently
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reviewed by all three authors (PBV, MH, GCL). Studies that were clearly irrelevant to the topic in question based on their title (113 in total) were eliminated. The abstracts of
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the remaining 94 articles were then independently scrutinized by all three authors. Studies that clearly did not meet the inclusion criteria based on the information contained
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in their abstracts (61 in total) were eliminated. The remaining 33 abstracts were determined to meet the inclusion criteria by at least one author, so the corresponding full
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texts were independently reviewed by all three authors. After full text review, 26 of these studies were unanimously eliminated by all three authors because they failed to meet the inclusion criteria. Therefore, seven articles were ultimately retained from the primary search. At every phase of review, if one or more authors selected a study, that article moved on to the next phase. In the final phase of review (full text review), there was no disagreement over which studies should ultimately be included. All references cited in the articles retrieved in the initial query were then compiled in our secondary search. These references were screened in the same manner as the articles from the primary search (title review then abstract review then full text review). Two additional studies that met the inclusion criteria were retained from the secondary search. Therefore, nine total studies were used for data retrieval (Figure 1) [9-17].
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ACCEPTED MANUSCRIPT These nine studies described a total of 957 patients who had undergone total knee arthroplasty: 428 with standard instrumentation and 529 with patient-specific
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instrumentation. Using previously published data, it was determined that a sample size of 80 patients per group would have sufficient power (0.80) to detect a significant difference
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(α = 0.05) in all primary outcomes [18]. The present study therefore met the minimum
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sample size requirement.
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The data published in the nine component studies were meticulously extracted and compiled. A random effects meta-analysis was generated using this data, allowing us
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to compare standard instrumentation versus patient-specific instrumentation with regard to coronal alignment, sagittal alignment, operative time, intraoperative blood loss,
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transfusion requirement, and perioperative cost. The meta-analysis was performed with
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MIX meta-analysis software (Version 1.7) for Windows.
Source of Funding: No external funding sources were utilized for this investigation.
Results
The nine component studies described a total of 957 total knee arthroplasties (428 performed with standard instrumentation and 529 with patient-specific instrumentation). All cases performed with patient-specific instrumentation utilized preoperative MRI rather than CT. The details of these nine studies are shown in Table 1. While patient-specific instrumentation demonstrated improved accuracy in coronal alignment as measured by femorotibial angle (FTA) (p = 0.0003), standard instrumentation demonstrated improved accuracy in coronal alignment as measured by
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ACCEPTED MANUSCRIPT hip-knee-ankle angle (HKA) (p = 0.02) (Table 2). Importantly, there were no significant differences in the ability of either technique to avoid outliers (> 3 degrees from target
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alignment) in either FTA (p = 0.7) or HKA (p = 0.7) (Table 3).
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Measures of sagittal alignment accuracy were equivalent between the two groups for both the femoral component (p = 0.5) and the tibial component (p = 0.9). The average
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femoral component was 7.4 degrees flexed relative to the anatomic axis of the femur in
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the PSI group compared to 5.3 degrees flexed in the standard instrumentation group. Operative time was not significantly reduced in the PSI group (n = 193 knees)
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compared to the standard instrumentation group (n = 192 knees) (p = 0.1). The mean operative time in the PSI group was 93 minutes compared to 104 minutes in the standard
until dressings.
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instrumentation group (p = 0.1). Operative time was defined as the time from incision
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Blood loss and transfusion requirements were also similar between treatment groups. The mean intraoperative blood loss was 371 mL for the PSI group versus 384 mL for the standard instrumentation group (p = 0.2). Intraoperative blood loss was defined by the component studies as the amount of blood noted in the suction device prior to irrigation of the knee. Of note, this value only includes intraoperative blood loss, not postoperative blood loss. The percentage of patients requiring blood transfusion was 10.1% for the PSI group and 14.1% for the standard instrumentation group (p = 0.1). Only one study presented data regarding perioperative cost [9]. That study reported a total savings of $322 per case with patient-specific instrumentation versus standard instrumentation as a result of decreased operative time and sterilization time with PSI [9]. However, once the cost of generating the custom cutting guide ($950) was
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ACCEPTED MANUSCRIPT taken into account, it was determined that PSI was actually more expensive than standard instrumentation by $628 per case [9]. Additionally, the cost of the preoperative MRI
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(varied between $400 and $1250 based on insurance) further added to the expense of PSI
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[9].
Four different patient-specific instrumentation systems were utilized in the
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component studies: Biomet Signature™ (6 studies, 393 TKA), Zimmer Patient Specific
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Instruments™ (1 study, 40 TKA), Smith & Nephew Visionaire™ (2 studies, 46 TKA), and Styker OtisMed™ (1 study, 50 TKA) (Table 1). Due to the limited sample sizes of
Discussion
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comparisons between PSI systems.
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these individual groups, the present study is underpowered to make statistical
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Patient-specific instrumentation (PSI) was designed to improve alignment through preoperative navigation, reduce operative time by minimizing intraoperative decision making, and decrease perioperative cost by limiting the number of instrument trays required per procedure. In recent years, several comparative studies and randomized controlled trials have sought to compare PSI to standard instrumentation. These studies, which were limited in power, have individually failed to substantiate the theoretical advantages of PSI. Therefore, the purpose of this study was to use the power of systematic review and meta-analysis to further evaluate the use of PSI in TKA. There are several limitations to this study. First, as this is a meta-analysis, the results presented are the aggregated data extracted from many smaller studies with various devices and varying patient populations. However, because the indications and
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ACCEPTED MANUSCRIPT techniques employed in these studies are similar, the likelihood of confounding variables and bias is minimized. Second, none of the component studies reported the ability of
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custom cutting guides to achieve proper femoral component rotation. Lakstein et al.
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showed that component malrotation following TKA can be a significant source of pain and dysfunction [19]. Therefore, the value of PSI cannot be fully evaluated when the
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ability of this technology to achieve proper component rotation is not reported. Third, the
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studies included in this analysis originated from high-volume surgical centers with experienced arthroplasty surgeons, and thus, may be subject to expert bias. Plaskos et al.
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demonstrated that experienced surgeons were more accurate in their bone cuts using standard TKA instrumentation compared to surgeons with less experience [20].
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Therefore, while this investigation found that PSI did not significantly improve alignment compared to standard instrumentation, this conclusion may not apply to orthopaedic
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surgeons with varying levels of experience. Finally, all of the component studies described cases performed with MRI-based PSI, rather than CT-based PSI. Hence, the data presented does not allow comparison between these two techniques. Our aggregated results did not demonstrate superiority of PSI over standard instrumentation with regard to post-operative coronal alignment. While the results indicate that on average the femorotibial angle (FTA) is more accurately recreated with PSI, the mean hip-knee-ankle angle (HKA) is closer to a neutral mechanical axis with standard instrumentation. Additionally, there were no significant differences in the ability of either technique to avoid outliers (> 3 degrees from target alignment) in either FTA (p = 0.7) or HKA (p = 0.7). This is of critical importance as one of the theoretical benefits of patient-specific instrumentation is that it reduces the likelihood of varus or valgus outliers
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ACCEPTED MANUSCRIPT that may lead to poor functional outcomes. This theoretical benefit was not substantiated with the results of the present study. Consequently, current evidence does not support the
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claim that patient-specific instrumentation improves alignment in the coronal plane
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compared to standard instrumentation.
Only three studies reported data on post-operative sagittal alignment following
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TKA performed with PSI (n = 112) versus standard instrumentation (n = 112) [10, 12,
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17]. The aggregated results demonstrated similar alignment in the sagittal plane for both the femoral and tibial components (p = 0.5 and 0.9, respectively) between treatment
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groups. Sagittal malalignment has been reported as an important potential drawback with PSI. Victor et al. found that sagittal outliers were a common error with patient-specific
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guides in their study population (21% with PSI versus 3% with standard instrumentation, p = 0.002) [21]. These outliers were so common that they were forced to abandon the
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patient-specific guides in 22% of patients and modify the guides in 28% of patients [21]. Lustig et al. reported that PSI achieved sagittal component alignment within +/- 3 degrees of the preoperative plan in only 54.5% of cases [22]. It is unclear whether this problem is device-specific or whether these inaccuracies are the result of the cutting blocks being sensitive to variations in osteophyte removal prior to placement. Stronach et al. reported in their series of 66 TKA’s that the custom cutting guides did not securely fit on 8 femurs (12%) and on 3 tibias (5%), and that 161 total intraoperative changes (2.4 changes per knee) were required with PSI [23]. Given this data, blind reliance on patient-specific instrumentation during primary TKA should not be done. Patient-specific instrumentation did not lead to a reduction in operative time compared to standard instrumentation. The mean operative time with PSI was 93 minutes
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ACCEPTED MANUSCRIPT versus 104 minutes with standard instrumentation (p = 0.1). This is important to note because one of the theoretical advantages of PSI is decreased operative time through
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minimization of intraoperative decision making and instrument handling. One potential
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explanation for why this reduction in operative time may not have been realized is the fact that the custom cutting guides often require intraoperative adjustments, as was noted
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in the Stronach et al study [23]. These intraoperative changes (on average 2.4 changes per
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knee) add to the operative time and may potentially offset any time saved by using the custom cutting guides.
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The present study also found no significant differences in intraoperative blood loss (p = 0.2) or transfusion requirements (p = 0.1) between PSI and standard
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instrumentation. This is surprising because, unlike standard instrumentation which often requires violation of the intramedullary canal during application of the femoral and tibial
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guides, PSI does not require breach of the intramedullary canal. Therefore, in theory, PSI should result in decreased blood loss and fewer transfusions than standard instrumentation. These findings, however, were not seen in the present study. Finally, the one study that evaluated cost found that PSI was actually more expensive than standard instrumentation by at least $1500 per case after taking into account the cost of generating the custom cutting guide and performing the preoperative MRI [9]. Any savings borne by reduced operative time and sterilization time were overwhelmed by the overhead costs necessitated by PSI [9]. In order to gain acceptance into modern practice, new technology must demonstrate either (1) increased efficacy compared to existing technology or (2) equivalent outcomes with reduced cost. Equivalent outcomes with more expensive technology do not fit into the current cost-
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ACCEPTED MANUSCRIPT effectiveness paradigm. Consequently, given the results of the present study, the widespread use of PSI in routine primary TKA cannot be recommended.
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Patient-specific instrumentation offers various theoretical advantages that make it
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an attractive option for total knee arthroplasty. However, in the absence of proven clinical, radiographic, and/or cost benefits over standard instrumentation, one cannot
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justify the widespread use of these custom cutting blocks. Current evidence does not
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support the routine use of patient-specific instrumentation in total knee arthroplasty.
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ACCEPTED MANUSCRIPT References 1. Centers for Disease Control and Prevention. Number of all-listed procedures for
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discharges from short-stay hospitals, by procedure category and age. 2010.
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http://www.cdc.gov/nchs/data/nhds/4procedures/2010pro4_numberprocedureage.pdf. Accesssed August 14, 2013.
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2. Kurtz S, Ong K, Lau E, Mowat F, Halpern M. Projections of primary and revision hip
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and knee arthroplasty in the United States from 2005 to 2030. The Journal of bone and joint surgery American volume 2007; 89:780.
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3. Sharkey PF, Hozack WJ, Rothman RH, Shastri S, Jacoby SM. Insall Award paper. Why are total knee arthroplasties failing today? Clinical orthopaedics and related
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research 2002; 7.
4. Mason JB, Fehring TK, Estok R, Banel D, Fahrbach K. Meta-analysis of alignment
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outcomes in computer-assisted total knee arthroplasty surgery. The Journal of arthroplasty 2007; 22:1097.
5. Bauwens K, Matthes G, Wich M, Gebhard F, Hanson B, Ekkernkamp A, Stengel D. Navigated total knee replacement. A meta-analysis. The Journal of bone and joint surgery American volume 2007; 89:261. 6. Cheng T, Zhang G, Zhang X. Clinical and radiographic outcomes of image-based computer-assisted total knee arthroplasty: an evidence-based evaluation. Surgical innovation 2011; 18:15. 7. Radermacher K, Portheine F, Anton M, Zimolong A, Kaspers G, Rau G, Staudte HW. Computer assisted orthopaedic surgery with image based individual templates. Clinical orthopaedics and related research 1998; 28.
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ACCEPTED MANUSCRIPT 8. Lombardi AV, Jr., Berend KR, Adams JB. Patient-specific approach in total knee arthroplasty. Orthopedics 2008; 31:927.
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9. Barrack RL, Ruh EL, Williams BM, Ford AD, Foreman K, Nunley RM. Patient
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specific cutting blocks are currently of no proven value. The Journal of bone and joint surgery British volume 2012; 94:95.
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10. Boonen B, Schotanus MG, Kort NP. Preliminary experience with the patient-specific
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templating total knee arthroplasty. Acta orthopaedica 2012; 83:387. 11. Chareancholvanich K, Narkbunnam R, Pornrattanamaneewong C. A prospective
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randomised controlled study of patient-specific cutting guides compared with conventional instrumentation in total knee replacement. The bone & joint journal 2013;
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95-B:354.
12. Dossett HG, Swartz GJ, Estrada NA, LeFevre GW, Kwasman BG. Kinematically
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versus mechanically aligned total knee arthroplasty. Orthopedics 2012; 35:e160. 13. Ng VY, DeClaire JH, Berend KR, Gulick BC, Lombardi AV, Jr. Improved accuracy of alignment with patient-specific positioning guides compared with manual instrumentation in TKA. Clinical orthopaedics and related research 2012; 470:99. 14. Noble JW, Jr., Moore CA, Liu N. The value of patient-matched instrumentation in total knee arthroplasty. The Journal of arthroplasty 2012; 27:153. 15. Nunley RM, Ellison BS, Ruh EL, Williams BM, Foreman K, Ford AD, Barrack RL. Are patient-specific cutting blocks cost-effective for total knee arthroplasty? Clinical orthopaedics and related research 2012; 470:889.
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ACCEPTED MANUSCRIPT 16. Nunley RM, Ellison BS, Zhu J, Ruh EL, Howell SM, Barrack RL. Do patient-specific guides improve coronal alignment in total knee arthroplasty? Clinical orthopaedics and
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related research 2012; 470:895.
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17. Vundelinckx BJ, Bruckers L, De Mulder K, De Schepper J, Van Esbroeck G. Functional and radiographic short-term outcome evaluation of the Visionaire system, a
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patient-matched instrumentation system for total knee arthroplasty. The Journal of
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arthroplasty 2013; 28:964.
18. Cohen J: Statistical power analysis for the behavioral sciences. Lawrence Erlbaum
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Associates, Hillsdale, NJ, 1988.
19. Lakstein D, Zarrabian M, Kosashvili Y, Safir O, Gross AE, Backstein D. Revision
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total knee arthroplasty for component malrotation is highly beneficial: a case control study. The Journal of arthroplasty 2010; 25:1047.
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20. Plaskos C, Hodgson AJ, Inkpen K, McGraw RW. Bone cutting errors in total knee arthroplasty. The Journal of arthroplasty 2002; 17:698. 21. Victor J, Dujardin J, Vandenneucker H, Arnout N, Bellemans J. Patient-specific Guides Do Not Improve Accuracy in Total Knee Arthroplasty: A Prospective Randomized Controlled Trial. Clinical orthopaedics and related research 2013; [Epub ahead of print]. 22. Lustig S, Scholes CJ, Oussedik SI, Kinzel V, Coolican MR, Parker DA. Unsatisfactory accuracy as determined by computer navigation of VISIONAIRE patientspecific instrumentation for total knee arthroplasty. The Journal of arthroplasty 2013; 28:469.
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ACCEPTED MANUSCRIPT 23. Stronach BM, Pelt CE, Erickson J, Peters CL. Patient-specific total knee arthroplasty required frequent surgeon-directed changes. Clinical orthopaedics and related research
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2013; 471:169.
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ACCEPTED MANUSCRIPT Figure Legend Figure 1. Flow diagram presenting the systematic search process utilized in this
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study.
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*The search keyword terms used were “total knee arthroplasty” and “patient-
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specific.”
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Figure 1
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ACCEPTED MANUSCRIPT Table 1. Details of the nine component studies used for data retrieval.
Boonen
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Patient Specific Cutting JBJS Blocks Are British Currently of No Proven Value Preliminary Experience with the Acta PatientOrthopaedi Specific ca Templating Total Knee Arthroplasty A Prospective Randomised Controlled Study of PatientSpecific Cutting JBJS Guides British Compared with Conventiona l Instrumentati on in Total Knee Replacement Kinematicall y versus Mechanicall Orthopedic y Aligned s Total Knee Arthroplasty Improved Accuracy of CORR Alignment
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201 2
Journal
PSI System
100
10 0
Biomet Signature ™
80
40
40
Biomet Signature ™
200
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Barrack
Title
Number of TKA Tot Standa PS al rd I
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First Author
Yea r
80
40
40
Zimmer Patient Specific Instruments ™
201 2
82
41
41
Biomet Signature ™
55
10 5
Biomet Signature ™
Chareancholvan ich
201 3
Dossett
Ng
201 2
19
160
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14
15
57
Biomet Signature ™
10 0
Biomet Signature ™ / Stryker OtisMed™
31
Smith & Nephew Visionaire ™
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Nunley
201 2
29
Smith & Nephew Visionaire ™
114
57
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Noble
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With PatientSpecific Positioning Guides Compared with Manual Instrumentati on in TKA The Value of PatientMatched Journal of Instrumentati Arthroplast on in Total y Knee Arthroplasty Are PatientSpecific Cutting Blocks CostCORR Effective for Total Knee Arthroplasty ? Do PatientSpecific Guides Improve Coronal CORR Alignment in Total Knee Arthroplasty ? Functional and Radiographi c ShortTerm Outcome Journal of Evaluation Arthroplast of the y Visionaire System, a PatientMatched Instrumentati
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Nunley
Vundelinckx
201 2
201 3
20
150
62
50
31
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on System for Total Knee Arthroplasty
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ACCEPTED MANUSCRIPT Table 2. Femorotibial angle (FTA) and hip-knee-ankle angle (HKA) reported in the nine component studies used for data retrieval. NR = not reported.
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FTA (degrees) Standard PSI 1.3 0.5 NR NR 0.3 0.3 2.2 1.4 0.3 0.6 2.8 1.7 NR NR 1.8 0.8 2.0 1.6 1.4 0.8 0.0003
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Year
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Number of TKA Standard PSI Barrack 2012 100 100 Boonen 2012 40 40 Chareancholvanich 2013 40 40 Dossett 2012 41 41 Ng 2012 55 105 Noble 2012 14 15 Nunley 2012 57 57 Nunley 2012 50 100 Vundelinckx 2013 31 31 Weighted Mean p value First Author
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HKA (degrees) Standard PSI 0.5 1.7 1.0 1.0 NR NR 0.0 0.3 2.1 2.0 NR NR NR NR 0.1 1.7 NR NR 0.6 1.6 0.02
ACCEPTED MANUSCRIPT Table 3. Percentage of femorotibial angle (FTA) and hip-knee-ankle angle (HKA) outliers (> 3 degrees from target alignment) reported in the nine component studies used for data retrieval. NR = not reported.
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FTA Outliers (%) Standard PSI 27 29 NR NR 8 3 NR NR NR NR NR NR 39 42 28 30 NR NR 27 28 0.7
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Year
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Number of TKA Standard PSI Barrack 2012 100 100 Boonen 2012 40 40 Chareancholvanich 2013 40 40 Dossett 2012 41 41 Ng 2012 55 105 Noble 2012 14 15 Nunley 2012 57 57 Nunley 2012 50 100 Vundelinckx 2013 31 31 Weighted Mean p value First Author
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HKA Outliers (%) Standard PSI 23 31 46 29 NR NR NR NR 22 9 NR NR 18 26 16 31 NR NR 23 24 0.7
S0883-5403(14)00345-3 doi: 10.1016/j.arth.2014.01.039 YARTH 54000
To appear in:
Journal of Arthroplasty
Received date: Revised date: Accepted date:
16 August 2013 18 December 2013 5 January 2014
Please cite this article as: Voleti Pramod B., Hamula Mathew, Baldwin Keith D., Lee Gwo-Chin, Current Data Does Not Support Routine Use of Patient-Specific Instrumentation in Total Knee Arthroplasty, Journal of Arthroplasty (2014), doi: 10.1016/j.arth.2014.01.039
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT Current Data Does Not Support Routine Use of Patient-Specific Instrumentation in Total Knee Arthroplasty
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Pramod B. Voleti, MD1 Mathew Hamula, BS1 Keith D. Baldwin, MD, MPH, MSPT1 Gwo-Chin Lee, MD1
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Department of Orthopaedic Surgery Hospital of the University of Pennsylvania 3400 Spruce Street, 2 Silverstein Philadelphia, PA 19104, USA
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Corresponding Author:
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Gwo-Chin Lee, MD Assistant Professor Department of Orthopaedic Surgery Hospital of the University of Pennsylvania 3400 Spruce Street, 2 Silverstein Philadelphia, PA 19104, USA Telephone: 215-349-8689 Fax: 215-349-5128 E-mail: [email protected]
1
ACCEPTED MANUSCRIPT Abstract The purpose of this systematic review and meta-analysis is to compare patient-
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specific instrumentation (PSI) versus standard instrumentation for total knee arthroplasty
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(TKA) with regard to coronal and sagittal alignment, operative time, intraoperative blood loss, and cost. A systematic query in search of relevant studies was performed, and the
SC
data published in these studies were extracted and aggregated. In regard to coronal
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alignment, PSI demonstrated improved accuracy in femorotibial angle (FTA) (p = 0.0003), while standard instrumentation demonstrated improved accuracy in hip-knee-
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ankle angle (HKA) (p = 0.02). Importantly, there were no differences between treatment groups in the percentages of FTA or HKA outliers (> 3 degrees from target alignment) (p
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= 0.7). Sagittal alignment, operative time, intraoperative blood loss, and cost were also similar between groups (p > 0.1 for all comparisons). Given these results, current data
Keywords
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does not support routine use of patient-specific instrumentation in total knee arthroplasty.
patient-specific instrumentation; patient-specific guides; custom cutting guides; total knee arthroplasty instrumentation; primary total knee arthroplasty
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ACCEPTED MANUSCRIPT Introduction Total knee arthroplasty (TKA) is one of the most commonly performed
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musculoskeletal procedures in the United States with approximately 719,000 performed
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annually [1]. Given projected increases in population size and longevity, the incidence of TKA is predicted to rise in the future, reaching an estimated 3.48 million by 2030 [2].
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Perfecting surgical technique for TKA is therefore of paramount importance.
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In recent years, there has been an increased focus on the influence of limb alignment and component position on longevity and outcomes after TKA [3].
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Technological advancements aimed at improving limb alignment and component position include computer-assisted surgery (CAS) and patient-specific instrumentation (PSI).
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Meta-analyses comparing CAS versus conventional TKA have demonstrated mixed results with regard to component orientation and mechanical axis [4, 5] with no
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difference in functional outcomes [6]. The drawbacks of CAS include difficulty with accurate intraoperative landmark registration, increased set-up and operative time, increased perioperative cost, risk of pin loosening and pin-site fracture, and a substantial learning curve [7, 8].
Patient-specific instrumentation (PSI) was introduced with the goals of improving alignment through preoperative navigation, reducing operative time by minimizing intraoperative decision making, and decreasing perioperative cost by limiting the number of instrument trays required per procedure. This technology employs advanced imaging (MRI or CT) to generate an ideal cutting guide based on the patient’s anatomic parameters. Both femoral and tibial cutting guides are generated; these guides determine the location of the bone cuts; the size, position, and rotation of the components; and the
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ACCEPTED MANUSCRIPT alignment of the limb. In recent years, several comparative studies and randomized controlled trials that compare patient-specific versus standard TKA instrumentation have
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been published. Individually, these studies have failed to substantiate the theoretical
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benefits of PSI. To our knowledge, no systematic review or meta-analysis of these studies has been performed.
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Therefore, the purpose of this study is to perform a systematic review and meta-
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analysis of the current evidence comparing standard instrumentation to patient-specific instrumentation for TKA with regard to: (1) coronal alignment, (2) sagittal alignment, (3)
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operative time, (4) intraoperative blood loss, (5) transfusion requirement, and (6)
Materials and Methods
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perioperative cost.
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We performed a systematic query using both the Medline and Embase computerized literature databases in search for articles containing the keyword terms “total knee arthroplasty” and “patient-specific.” The search was performed on May 1, 2013, and all studies published prior to that date were considered. In addition to this primary search, we performed a secondary search by scrutinizing all references cited in the articles retrieved from the primary search in order to identify additional studies of interest. Three independent evaluators reviewed all articles retrieved from the primary and secondary searches using the systematic strategy outlined below. The evaluators were blinded with regard to the determinations of the other evaluators. Studies were included in the systematic review and meta-analysis if they met the following criteria: (1) they compared patients who underwent TKA with standard
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ACCEPTED MANUSCRIPT instrumentation to those who underwent TKA with patient-specific instrumentation and (2) they reported post-operative coronal alignment, post-operative sagittal alignment,
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operative time, intraoperative blood loss, transfusion requirement, and/or perioperative
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cost. Review articles, technique descriptions, and editorials were excluded. The initial combined Medline and Embase search using the aforementioned
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keyword terms yielded 207 unique articles. The titles of these studies were independently
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reviewed by all three authors (PBV, MH, GCL). Studies that were clearly irrelevant to the topic in question based on their title (113 in total) were eliminated. The abstracts of
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the remaining 94 articles were then independently scrutinized by all three authors. Studies that clearly did not meet the inclusion criteria based on the information contained
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in their abstracts (61 in total) were eliminated. The remaining 33 abstracts were determined to meet the inclusion criteria by at least one author, so the corresponding full
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texts were independently reviewed by all three authors. After full text review, 26 of these studies were unanimously eliminated by all three authors because they failed to meet the inclusion criteria. Therefore, seven articles were ultimately retained from the primary search. At every phase of review, if one or more authors selected a study, that article moved on to the next phase. In the final phase of review (full text review), there was no disagreement over which studies should ultimately be included. All references cited in the articles retrieved in the initial query were then compiled in our secondary search. These references were screened in the same manner as the articles from the primary search (title review then abstract review then full text review). Two additional studies that met the inclusion criteria were retained from the secondary search. Therefore, nine total studies were used for data retrieval (Figure 1) [9-17].
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ACCEPTED MANUSCRIPT These nine studies described a total of 957 patients who had undergone total knee arthroplasty: 428 with standard instrumentation and 529 with patient-specific
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instrumentation. Using previously published data, it was determined that a sample size of 80 patients per group would have sufficient power (0.80) to detect a significant difference
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(α = 0.05) in all primary outcomes [18]. The present study therefore met the minimum
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sample size requirement.
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The data published in the nine component studies were meticulously extracted and compiled. A random effects meta-analysis was generated using this data, allowing us
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to compare standard instrumentation versus patient-specific instrumentation with regard to coronal alignment, sagittal alignment, operative time, intraoperative blood loss,
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transfusion requirement, and perioperative cost. The meta-analysis was performed with
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MIX meta-analysis software (Version 1.7) for Windows.
Source of Funding: No external funding sources were utilized for this investigation.
Results
The nine component studies described a total of 957 total knee arthroplasties (428 performed with standard instrumentation and 529 with patient-specific instrumentation). All cases performed with patient-specific instrumentation utilized preoperative MRI rather than CT. The details of these nine studies are shown in Table 1. While patient-specific instrumentation demonstrated improved accuracy in coronal alignment as measured by femorotibial angle (FTA) (p = 0.0003), standard instrumentation demonstrated improved accuracy in coronal alignment as measured by
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ACCEPTED MANUSCRIPT hip-knee-ankle angle (HKA) (p = 0.02) (Table 2). Importantly, there were no significant differences in the ability of either technique to avoid outliers (> 3 degrees from target
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alignment) in either FTA (p = 0.7) or HKA (p = 0.7) (Table 3).
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Measures of sagittal alignment accuracy were equivalent between the two groups for both the femoral component (p = 0.5) and the tibial component (p = 0.9). The average
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femoral component was 7.4 degrees flexed relative to the anatomic axis of the femur in
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the PSI group compared to 5.3 degrees flexed in the standard instrumentation group. Operative time was not significantly reduced in the PSI group (n = 193 knees)
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compared to the standard instrumentation group (n = 192 knees) (p = 0.1). The mean operative time in the PSI group was 93 minutes compared to 104 minutes in the standard
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instrumentation group (p = 0.1). Operative time was defined as the time from incision
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Blood loss and transfusion requirements were also similar between treatment groups. The mean intraoperative blood loss was 371 mL for the PSI group versus 384 mL for the standard instrumentation group (p = 0.2). Intraoperative blood loss was defined by the component studies as the amount of blood noted in the suction device prior to irrigation of the knee. Of note, this value only includes intraoperative blood loss, not postoperative blood loss. The percentage of patients requiring blood transfusion was 10.1% for the PSI group and 14.1% for the standard instrumentation group (p = 0.1). Only one study presented data regarding perioperative cost [9]. That study reported a total savings of $322 per case with patient-specific instrumentation versus standard instrumentation as a result of decreased operative time and sterilization time with PSI [9]. However, once the cost of generating the custom cutting guide ($950) was
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ACCEPTED MANUSCRIPT taken into account, it was determined that PSI was actually more expensive than standard instrumentation by $628 per case [9]. Additionally, the cost of the preoperative MRI
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(varied between $400 and $1250 based on insurance) further added to the expense of PSI
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[9].
Four different patient-specific instrumentation systems were utilized in the
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component studies: Biomet Signature™ (6 studies, 393 TKA), Zimmer Patient Specific
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Instruments™ (1 study, 40 TKA), Smith & Nephew Visionaire™ (2 studies, 46 TKA), and Styker OtisMed™ (1 study, 50 TKA) (Table 1). Due to the limited sample sizes of
Discussion
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comparisons between PSI systems.
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these individual groups, the present study is underpowered to make statistical
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Patient-specific instrumentation (PSI) was designed to improve alignment through preoperative navigation, reduce operative time by minimizing intraoperative decision making, and decrease perioperative cost by limiting the number of instrument trays required per procedure. In recent years, several comparative studies and randomized controlled trials have sought to compare PSI to standard instrumentation. These studies, which were limited in power, have individually failed to substantiate the theoretical advantages of PSI. Therefore, the purpose of this study was to use the power of systematic review and meta-analysis to further evaluate the use of PSI in TKA. There are several limitations to this study. First, as this is a meta-analysis, the results presented are the aggregated data extracted from many smaller studies with various devices and varying patient populations. However, because the indications and
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ACCEPTED MANUSCRIPT techniques employed in these studies are similar, the likelihood of confounding variables and bias is minimized. Second, none of the component studies reported the ability of
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custom cutting guides to achieve proper femoral component rotation. Lakstein et al.
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showed that component malrotation following TKA can be a significant source of pain and dysfunction [19]. Therefore, the value of PSI cannot be fully evaluated when the
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ability of this technology to achieve proper component rotation is not reported. Third, the
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studies included in this analysis originated from high-volume surgical centers with experienced arthroplasty surgeons, and thus, may be subject to expert bias. Plaskos et al.
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demonstrated that experienced surgeons were more accurate in their bone cuts using standard TKA instrumentation compared to surgeons with less experience [20].
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Therefore, while this investigation found that PSI did not significantly improve alignment compared to standard instrumentation, this conclusion may not apply to orthopaedic
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surgeons with varying levels of experience. Finally, all of the component studies described cases performed with MRI-based PSI, rather than CT-based PSI. Hence, the data presented does not allow comparison between these two techniques. Our aggregated results did not demonstrate superiority of PSI over standard instrumentation with regard to post-operative coronal alignment. While the results indicate that on average the femorotibial angle (FTA) is more accurately recreated with PSI, the mean hip-knee-ankle angle (HKA) is closer to a neutral mechanical axis with standard instrumentation. Additionally, there were no significant differences in the ability of either technique to avoid outliers (> 3 degrees from target alignment) in either FTA (p = 0.7) or HKA (p = 0.7). This is of critical importance as one of the theoretical benefits of patient-specific instrumentation is that it reduces the likelihood of varus or valgus outliers
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ACCEPTED MANUSCRIPT that may lead to poor functional outcomes. This theoretical benefit was not substantiated with the results of the present study. Consequently, current evidence does not support the
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claim that patient-specific instrumentation improves alignment in the coronal plane
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compared to standard instrumentation.
Only three studies reported data on post-operative sagittal alignment following
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TKA performed with PSI (n = 112) versus standard instrumentation (n = 112) [10, 12,
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17]. The aggregated results demonstrated similar alignment in the sagittal plane for both the femoral and tibial components (p = 0.5 and 0.9, respectively) between treatment
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groups. Sagittal malalignment has been reported as an important potential drawback with PSI. Victor et al. found that sagittal outliers were a common error with patient-specific
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guides in their study population (21% with PSI versus 3% with standard instrumentation, p = 0.002) [21]. These outliers were so common that they were forced to abandon the
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patient-specific guides in 22% of patients and modify the guides in 28% of patients [21]. Lustig et al. reported that PSI achieved sagittal component alignment within +/- 3 degrees of the preoperative plan in only 54.5% of cases [22]. It is unclear whether this problem is device-specific or whether these inaccuracies are the result of the cutting blocks being sensitive to variations in osteophyte removal prior to placement. Stronach et al. reported in their series of 66 TKA’s that the custom cutting guides did not securely fit on 8 femurs (12%) and on 3 tibias (5%), and that 161 total intraoperative changes (2.4 changes per knee) were required with PSI [23]. Given this data, blind reliance on patient-specific instrumentation during primary TKA should not be done. Patient-specific instrumentation did not lead to a reduction in operative time compared to standard instrumentation. The mean operative time with PSI was 93 minutes
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ACCEPTED MANUSCRIPT versus 104 minutes with standard instrumentation (p = 0.1). This is important to note because one of the theoretical advantages of PSI is decreased operative time through
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minimization of intraoperative decision making and instrument handling. One potential
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explanation for why this reduction in operative time may not have been realized is the fact that the custom cutting guides often require intraoperative adjustments, as was noted
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in the Stronach et al study [23]. These intraoperative changes (on average 2.4 changes per
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knee) add to the operative time and may potentially offset any time saved by using the custom cutting guides.
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The present study also found no significant differences in intraoperative blood loss (p = 0.2) or transfusion requirements (p = 0.1) between PSI and standard
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instrumentation. This is surprising because, unlike standard instrumentation which often requires violation of the intramedullary canal during application of the femoral and tibial
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guides, PSI does not require breach of the intramedullary canal. Therefore, in theory, PSI should result in decreased blood loss and fewer transfusions than standard instrumentation. These findings, however, were not seen in the present study. Finally, the one study that evaluated cost found that PSI was actually more expensive than standard instrumentation by at least $1500 per case after taking into account the cost of generating the custom cutting guide and performing the preoperative MRI [9]. Any savings borne by reduced operative time and sterilization time were overwhelmed by the overhead costs necessitated by PSI [9]. In order to gain acceptance into modern practice, new technology must demonstrate either (1) increased efficacy compared to existing technology or (2) equivalent outcomes with reduced cost. Equivalent outcomes with more expensive technology do not fit into the current cost-
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ACCEPTED MANUSCRIPT effectiveness paradigm. Consequently, given the results of the present study, the widespread use of PSI in routine primary TKA cannot be recommended.
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Patient-specific instrumentation offers various theoretical advantages that make it
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an attractive option for total knee arthroplasty. However, in the absence of proven clinical, radiographic, and/or cost benefits over standard instrumentation, one cannot
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justify the widespread use of these custom cutting blocks. Current evidence does not
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support the routine use of patient-specific instrumentation in total knee arthroplasty.
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ACCEPTED MANUSCRIPT References 1. Centers for Disease Control and Prevention. Number of all-listed procedures for
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discharges from short-stay hospitals, by procedure category and age. 2010.
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http://www.cdc.gov/nchs/data/nhds/4procedures/2010pro4_numberprocedureage.pdf. Accesssed August 14, 2013.
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2. Kurtz S, Ong K, Lau E, Mowat F, Halpern M. Projections of primary and revision hip
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and knee arthroplasty in the United States from 2005 to 2030. The Journal of bone and joint surgery American volume 2007; 89:780.
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3. Sharkey PF, Hozack WJ, Rothman RH, Shastri S, Jacoby SM. Insall Award paper. Why are total knee arthroplasties failing today? Clinical orthopaedics and related
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research 2002; 7.
4. Mason JB, Fehring TK, Estok R, Banel D, Fahrbach K. Meta-analysis of alignment
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outcomes in computer-assisted total knee arthroplasty surgery. The Journal of arthroplasty 2007; 22:1097.
5. Bauwens K, Matthes G, Wich M, Gebhard F, Hanson B, Ekkernkamp A, Stengel D. Navigated total knee replacement. A meta-analysis. The Journal of bone and joint surgery American volume 2007; 89:261. 6. Cheng T, Zhang G, Zhang X. Clinical and radiographic outcomes of image-based computer-assisted total knee arthroplasty: an evidence-based evaluation. Surgical innovation 2011; 18:15. 7. Radermacher K, Portheine F, Anton M, Zimolong A, Kaspers G, Rau G, Staudte HW. Computer assisted orthopaedic surgery with image based individual templates. Clinical orthopaedics and related research 1998; 28.
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ACCEPTED MANUSCRIPT 8. Lombardi AV, Jr., Berend KR, Adams JB. Patient-specific approach in total knee arthroplasty. Orthopedics 2008; 31:927.
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9. Barrack RL, Ruh EL, Williams BM, Ford AD, Foreman K, Nunley RM. Patient
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specific cutting blocks are currently of no proven value. The Journal of bone and joint surgery British volume 2012; 94:95.
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10. Boonen B, Schotanus MG, Kort NP. Preliminary experience with the patient-specific
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templating total knee arthroplasty. Acta orthopaedica 2012; 83:387. 11. Chareancholvanich K, Narkbunnam R, Pornrattanamaneewong C. A prospective
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randomised controlled study of patient-specific cutting guides compared with conventional instrumentation in total knee replacement. The bone & joint journal 2013;
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95-B:354.
12. Dossett HG, Swartz GJ, Estrada NA, LeFevre GW, Kwasman BG. Kinematically
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versus mechanically aligned total knee arthroplasty. Orthopedics 2012; 35:e160. 13. Ng VY, DeClaire JH, Berend KR, Gulick BC, Lombardi AV, Jr. Improved accuracy of alignment with patient-specific positioning guides compared with manual instrumentation in TKA. Clinical orthopaedics and related research 2012; 470:99. 14. Noble JW, Jr., Moore CA, Liu N. The value of patient-matched instrumentation in total knee arthroplasty. The Journal of arthroplasty 2012; 27:153. 15. Nunley RM, Ellison BS, Ruh EL, Williams BM, Foreman K, Ford AD, Barrack RL. Are patient-specific cutting blocks cost-effective for total knee arthroplasty? Clinical orthopaedics and related research 2012; 470:889.
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ACCEPTED MANUSCRIPT 16. Nunley RM, Ellison BS, Zhu J, Ruh EL, Howell SM, Barrack RL. Do patient-specific guides improve coronal alignment in total knee arthroplasty? Clinical orthopaedics and
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related research 2012; 470:895.
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17. Vundelinckx BJ, Bruckers L, De Mulder K, De Schepper J, Van Esbroeck G. Functional and radiographic short-term outcome evaluation of the Visionaire system, a
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patient-matched instrumentation system for total knee arthroplasty. The Journal of
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arthroplasty 2013; 28:964.
18. Cohen J: Statistical power analysis for the behavioral sciences. Lawrence Erlbaum
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Associates, Hillsdale, NJ, 1988.
19. Lakstein D, Zarrabian M, Kosashvili Y, Safir O, Gross AE, Backstein D. Revision
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total knee arthroplasty for component malrotation is highly beneficial: a case control study. The Journal of arthroplasty 2010; 25:1047.
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20. Plaskos C, Hodgson AJ, Inkpen K, McGraw RW. Bone cutting errors in total knee arthroplasty. The Journal of arthroplasty 2002; 17:698. 21. Victor J, Dujardin J, Vandenneucker H, Arnout N, Bellemans J. Patient-specific Guides Do Not Improve Accuracy in Total Knee Arthroplasty: A Prospective Randomized Controlled Trial. Clinical orthopaedics and related research 2013; [Epub ahead of print]. 22. Lustig S, Scholes CJ, Oussedik SI, Kinzel V, Coolican MR, Parker DA. Unsatisfactory accuracy as determined by computer navigation of VISIONAIRE patientspecific instrumentation for total knee arthroplasty. The Journal of arthroplasty 2013; 28:469.
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ACCEPTED MANUSCRIPT 23. Stronach BM, Pelt CE, Erickson J, Peters CL. Patient-specific total knee arthroplasty required frequent surgeon-directed changes. Clinical orthopaedics and related research
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2013; 471:169.
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ACCEPTED MANUSCRIPT Figure Legend Figure 1. Flow diagram presenting the systematic search process utilized in this
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study.
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*The search keyword terms used were “total knee arthroplasty” and “patient-
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specific.”
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Figure 1
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ACCEPTED MANUSCRIPT Table 1. Details of the nine component studies used for data retrieval.
Boonen
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Patient Specific Cutting JBJS Blocks Are British Currently of No Proven Value Preliminary Experience with the Acta PatientOrthopaedi Specific ca Templating Total Knee Arthroplasty A Prospective Randomised Controlled Study of PatientSpecific Cutting JBJS Guides British Compared with Conventiona l Instrumentati on in Total Knee Replacement Kinematicall y versus Mechanicall Orthopedic y Aligned s Total Knee Arthroplasty Improved Accuracy of CORR Alignment
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201 2
Journal
PSI System
100
10 0
Biomet Signature ™
80
40
40
Biomet Signature ™
200
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Barrack
Title
Number of TKA Tot Standa PS al rd I
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First Author
Yea r
80
40
40
Zimmer Patient Specific Instruments ™
201 2
82
41
41
Biomet Signature ™
55
10 5
Biomet Signature ™
Chareancholvan ich
201 3
Dossett
Ng
201 2
19
160
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14
15
57
Biomet Signature ™
10 0
Biomet Signature ™ / Stryker OtisMed™
31
Smith & Nephew Visionaire ™
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Nunley
201 2
29
Smith & Nephew Visionaire ™
114
57
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Noble
201 2
With PatientSpecific Positioning Guides Compared with Manual Instrumentati on in TKA The Value of PatientMatched Journal of Instrumentati Arthroplast on in Total y Knee Arthroplasty Are PatientSpecific Cutting Blocks CostCORR Effective for Total Knee Arthroplasty ? Do PatientSpecific Guides Improve Coronal CORR Alignment in Total Knee Arthroplasty ? Functional and Radiographi c ShortTerm Outcome Journal of Evaluation Arthroplast of the y Visionaire System, a PatientMatched Instrumentati
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Nunley
Vundelinckx
201 2
201 3
20
150
62
50
31
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on System for Total Knee Arthroplasty
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ACCEPTED MANUSCRIPT Table 2. Femorotibial angle (FTA) and hip-knee-ankle angle (HKA) reported in the nine component studies used for data retrieval. NR = not reported.
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FTA (degrees) Standard PSI 1.3 0.5 NR NR 0.3 0.3 2.2 1.4 0.3 0.6 2.8 1.7 NR NR 1.8 0.8 2.0 1.6 1.4 0.8 0.0003
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Year
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Number of TKA Standard PSI Barrack 2012 100 100 Boonen 2012 40 40 Chareancholvanich 2013 40 40 Dossett 2012 41 41 Ng 2012 55 105 Noble 2012 14 15 Nunley 2012 57 57 Nunley 2012 50 100 Vundelinckx 2013 31 31 Weighted Mean p value First Author
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HKA (degrees) Standard PSI 0.5 1.7 1.0 1.0 NR NR 0.0 0.3 2.1 2.0 NR NR NR NR 0.1 1.7 NR NR 0.6 1.6 0.02
ACCEPTED MANUSCRIPT Table 3. Percentage of femorotibial angle (FTA) and hip-knee-ankle angle (HKA) outliers (> 3 degrees from target alignment) reported in the nine component studies used for data retrieval. NR = not reported.
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FTA Outliers (%) Standard PSI 27 29 NR NR 8 3 NR NR NR NR NR NR 39 42 28 30 NR NR 27 28 0.7
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Year
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Number of TKA Standard PSI Barrack 2012 100 100 Boonen 2012 40 40 Chareancholvanich 2013 40 40 Dossett 2012 41 41 Ng 2012 55 105 Noble 2012 14 15 Nunley 2012 57 57 Nunley 2012 50 100 Vundelinckx 2013 31 31 Weighted Mean p value First Author
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HKA Outliers (%) Standard PSI 23 31 46 29 NR NR NR NR 22 9 NR NR 18 26 16 31 NR NR 23 24 0.7
