Patient specific guides for total knee arthroplasty are ready for primetime

Abstract

Aim:
To present the radiological results of total knee arthroplasty (TKA) with use of patient specific matched guides (PSG) from different manufacturer in patients suffering from severe osteoarthritis of the knee joint.

Methods:
This study describes the results of 57 knees operated with 4 different PSG systems and a group operated with conventional instrumentation (n = 60) by a single surgeon. The PSG systems were compared with each other and subdivided into cut- and pin PSG. The biomechanical axis [hip-knee-ankle angle (HKA)], varus/valgus of the femur [frontal femoral component (FFC)] and tibia (frontal tibial component) component, flexion/extension of the femur [flexion/extension of the femur component (LFC)] and posterior slope of the tibia [lateral tibial component (LTC)] component were evaluated on long-leg standing and lateral X-rays. A percentage of > 3(°) deviation was seen as an outlier.

Results:
The inter class correlation coefficient (ICC) revealed that radiographic measurements between both assessors were reliable (ICC > 0.8). Fisher exact test was used to test differences of proportions. The percentage of outliers of the HKA-axis was comparable between both the PSG and conventional groups (12.28% vs 18.33%, P < 0.424) and the cut- and pin PSG groups (14.3% vs 10.3%, P < 1.00). The percentage of outliers of the FFC (0% vs 18.33%, P < 0.000), LFC (15.78% vs 58.33%, P < 0.000) and LTC (15.78% vs 41.67%, P < 0.033) were significant different in favour of the PSG group. There were no significant differences regarding the outliers between the individual PSG systems and the PSG group subdivided into cut- and pin PSG.

Conclusion:
PSG for TKA show significant less outliers compared to the conventional technique. These single surgeon results suggest that PSG are ready for primetime.

Full text

Martijn GM Schotanus, Bert Boonen, Nanne P Kort
ORIGINAL ARTICLE
61 January 18, 2016
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Patient specific guides for total knee arthroplasty are ready
for primetime
Case Control Study
Martijn GM Schotanus, Bert Boonen, Nanne P Kort, Depart-
ment of Orthopaedic Surgery, Zuyderland Medical Centre, 6162
BG Sittard-Geleen, The Netherlands
Author contributions: Schotanus MGM designed the study,
gathered and analysed all the data, wrote the initial draft of the
manuscript, managed and performed the study; Boonen B ensured
the accuracy of the data and the analysis and gave critical revisions
related to important intellectual content of the manuscript; Kort NP
designed the study, revised the manuscript and gave final approval
of the version of the article to be published.
Institutional review board statement: The study was reviewed
and approved by the Institutional Review Board (METC Atrium-
Orbis-Zuyd, Heerlen, the Netherlands) file name 13-N-09.
Informed consent statement: All patients gave informed
consent prior to the study enrolment.
Conflict-of-interest statement: Dr. Nanne P Kort is a consultant
on the PSG technique for Biomet, Europe. The other authors
declare that they have no conflict of interest.
Data sharing statement: No additional data are available.
Open-Access: This article is an open-access article which was
selected by an in-house editor and fully peer-reviewed by external
reviewers. It is distributed in accordance with the Creative
Commons Attribution Non Commercial (CC BY-NC 4.0) license,
which permits others to distribute, remix, adapt, build upon this
work non-commercially, and license their derivative works on
different terms, provided the original work is properly cited and
the use is non-commercial. See: http://creativecommons.org/
licenses/by-nc/4.0/
Correspondence to: Martijn GM Schotanus, MSc, Research
Manager, Department of Orthopaedic Surgery, Zuyderland
Medical Centre, location Dr. H vd Hoffplein 1, 6162 BG Sittard-
Geleen, The Netherlands. martijnschotanus@hotmail.com
Telephone: +31-88-4597433
Fax: +31-88-4597986
Received: February 11, 2015
Peer-review started: February 12, 2015
First decision: June 18, 2015
Revised: October 22, 2015
Accepted: November 17, 2015
Article in press: November 25, 2015
Published online: January 18, 2016
Abstract
AIM: To present the radiological results of total knee
arthroplasty (TKA) with use of patient specific matched
guides (PSG) from different manufacturer in patients
suffering from severe osteoarthritis of the knee joint.
METHODS: This study describes the results of 57
knees operated with 4 different PSG systems and a
group operated with conventional instrumentation (
n
= 60) by a single surgeon. The PSG systems were
compared with each other and subdivided into cut- and
pin PSG. The biomechanical axis [hip-knee-ankle angle
(HKA)], varus/valgus of the femur [frontal femoral
component (FFC)] and tibia (frontal tibial component)
component, flexion/extension of the femur [flexion/
extension of the femur component (LFC)] and posterior
slope of the tibia [lateral tibial component (LTC)]
component were evaluated on long-leg standing and
lateral X-rays. A percentage of > 3° deviation was seen
as an outlier.
RESULTS: The inter class correlation coefficient (ICC)
revealed that radiographic measurements between
both assessors were reliable (ICC > 0.8). Fisher exact
test was used to test differences of proportions. The
percentage of outliers of the HKA-axis was comparable
between both the PSG and conventional groups (12.28%
vs
18.33%,
P
< 0.424) and the cut- and pin PSG groups
(14.3%
vs
10.3%,
P
< 1.00). The percentage of outliers
of the FFC (0%
vs
18.33%,
P
< 0.000), LFC (15.78%
vs
58.33%,
P
< 0.000) and LTC (15.78%
vs
41.67%,
P
< 0.033) were significant different in favour of the PSG
Submit a Manuscript: http://www.wjgnet.com/esps/
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DOI: 10.5312/wjo.v7.i1.61
World J Orthop 2016 January 18; 7(1): 61-68
ISSN 2218-5836 (online)
© 2016 Baishideng Publishing Group Inc. All rights reserved.

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Schotanus MGM
et al
. Patient specific guides ready for primetime
group. There were no significant differences regarding
the outliers between the individual PSG systems and the
PSG group subdivided into cut- and pin PSG.
CONCLUSION: PSG for TKA show significant less
outliers compared to the conventional technique. These
single surgeon results suggest that PSG are ready for
primetime.
Key words: Total knee arthroplasty; Patient specific
matched guides; Patient matched instruments; Single
surgeon; Alignment; Conventional instruments; Cutting
guides; Pin guides
© The Author(s) 2016. Published by Baishideng Publishing
Group Inc. All rights reserved.
Core tip: Total knee arthroplasty (TKA) is one of the most
successful and commonly performed surgical procedure
for the treatment of severe knee osteoarthritis with
excellent 15-20 years survivorships. This article provides
an analysis on patient specific matched guides (PSG)
between different manufacturers and the conventional
technique and between pin- and cutting guides for
TKA. In ad diti on, we compar ed our res ults wi th
previous studies (level 1 evidence), which are generally
unambiguous, and show no radiological difference.
However, in this trial, we do see difference in favour of
the PSG technique.
Schotanus MGM, Boonen B, Kort NP. Patient specific guides
for total knee arthroplasty are ready for primetime. World J
Orthop
2016; 7(1): 61-68 Available from: URL: http://www.
wjgnet.com/2218-5836/full/v7/i1/61.htm DOI: http://dx.doi.
org/10.5312/wjo.v7.i1.61
INTRODUCTION
Total knee arthroplasty (TKA) has been developed
signicantly over the last decades. Many changes have
been made to improve both survival and functioning. A
good postoperative biomechanical axis is one of the key
elements for a good implant survival. Malalignment is
associated with poor implant survivorship[1-4]. Several
studies reported results of postoperative malalignment
using conventional intramedullary alignment rods in
TKA[5-9]. Computer navigation was introduced to cope
with malalignment and instability in conventionally
placed prostheses[10]. These days, revolutionary changes
within the elective knee arthroplasty have taken place
due to industry driven interventions[11]. Patient specic
matched guides (PSG) for TKA is a relatively new
technique to align the knee prosthesis, using 3D rapid
prototyped disposable cut or pin guides that fits on
the native anatomy of the individual patient[12,13]. This
perioperative guiding technique eliminates the use of
intra- and extra medullar rods to make bony resections.
Previous published results on PSG suggest this to be a
good alternative to conventional instrumentation with
comparable results, improved radiological outcome and
reduced operation time and blood loss[7,13-23].
This prospective study on PSG between different
manufacturers and conventional technique for the im-
plantation of TKA was designed to address the following
research questions: Is there a significant difference
in outliers in alignment in the frontal and lateral plane
between PSG and conventional TKA, secondly between
the four individual different PSG systems and thirdly
between cut- and pin PSG? We hypothesise that
there will be fewer outliers with PSG TKA compared to
conventional TKA without differences between different
PSG systems and cut- and pin PSG.
MATERIALS AND METHODS
Patients were operated for TKA with PSG systems from
4 different manufactures (Table 1). In daily practice the
TKA system and PSG from the company Biomet is used.
Between May 2013 and April 2014, 60 consecutive
patients with debilitating osteoarthritis (OA) of the
knee joint, who were eligible for primary TKA were
included (Figure 1). Patients who were not eligible to
undergo magnetic resonance imaging (MRI) due to
metal artefacts around the knee joint from previous
surgery, claustrophobia, movement artefacts during
MRI scanning time, pigmented villonodular synovitis,
implanted electronic devices and patients that refused
to consent were excluded. TKA surgery was done
using PSG and consisted of guides from 4 different
TKA suppliers (Table 1). The conventional TKA group
consisted of 60 patients who were randomly selected
from a cohort (n ≥ 500) as a comparison group. We did
not match patients (e.g., body mass index, gender, age
and severity of OA) to avoid selection bias.
All patients gave informed consent to participate
in this prospective study and were operated by a
senior knee orthopaedic surgeon (NK) with extensive
experience with PSG[15,16]. Patients were not blinded to
the type of alignment method used. Three patients were
excluded from the study and therefore did not receive
the intervention as planned. A flowchart of the study
design is shown in Figure 2. There were no signicant
differences in baseline demographics, as summarized in
Table 2.
PSG and the conventional TKA surgery are ex-
tensively described in previous published studies[15,16].
Preoperative, a virtual 3 dimensional plan was made
based on the imaging protocols of the different manu-
facturers (Table 1). Preferred component position of
the prosthesis was planned to obtain a neutral biome-
chanical axis [hip-knee-ankle angle (HKA)] and position
of the femoral [frontal femoral component (FFC)] and
tibial [frontal tibial component (FTC)] components in
the frontal plane. All settings during planning in the
lateral plane were similar for all PSG systems: Femoral
component flexion [flexion/extension of the femur
component (LFC)] and tibial component posterior slope

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[lateral tibial component (LTC)] were set at 3°. The nal
approval of settings was done by the operating surgeon
(NK). After approval, the disposable cut or pin guides
(Table 1) for perioperative alignment were manufactured
and used during surgery. A midline approach was used
and a cemented prosthesis implemented in all cases
(Table 1). The guides were designed to make contact
with osteophytes and therefore it was not allowed
to remove these prior to the bony cuts. The same
procedure was performed in the conventional group,
except for the standard conventional rods for femur
and tibia with the same implant as the Signature group
(Vanguard Complete Knee System, Biomet, Warsaw,
INC). Conventional rods were used to align the position
of the cutting blocks: LFC and LTC were set at 0°.
All patients received a multimodal pain protocol
including spinal or general anesthesia and local infil-
tration analgesia without a drain and urine catheter.
Postoperative procedures were the same in all TKA
patients. Patients followed an enhanced recovery path-
way and received subcutaneous thromboprophylaxis
(Fondaparinux) once daily for 35 d, starting on the
evening on the rst postoperative day.
Preoperative approved planning for the femur and
tibia component were compared with the postoperative
achieved alignment of each component on radiographs.
HKA-axis and implant position were measured with
a calibrated protocol on digital images on a PACS sys-
tem[15,16]. HKA angle was evaluated on standardized
1-year postoperative frontal long-leg standing X-rays.
Varus/valgus position of the FFC and FTC perpendicular
to the HKA angle were measured on the same frontal
radiographs. Flexion/extension of the LFC, measured
from the anterior femoral cortex and posterior or anterior
slope of the LTC measured from the posterior cortex of
the tibia, were evaluated on 1-year postoperative lateral
radiographs. Deviations of > 3° between preoperative
planned HKA-axis (sum of FFC and FTC) and individual
components (FFC, FTC, LFC and LTC) compared to the
postoperative achieved alignment on radiographs, were
considered as outliers. Mean values, SD and percentages
of > 3° deviation of the preoperative planned alignment
and postoperative alignment were first compared
between the complete PSG group and the conventional
group and all PSG groups were compared with each
other. A comparison between cut- and pin guides was
also made (Table 1).
Ethical approval
This study was approved by the institutional review
board (IRB Atrium-Orbis Zuyd Heerlen, the Netherlands;
Dupuy-Synthes Smith and Nephew Zimmer Biomet
PSG Trumatch Visionaire PSI Signature
Guides Cut Cut Pin Pin
Implant Sigma CR Genesis ⅡNexGen Vanguard CR
Imaging protocol CT1MRI2CT or MRI1CT or MRI1
Table 1 Different industries with brand names, guide type, implant name and
scanning modality
1Scan of the hip, knee and ankle join; 2MRI of the knee joint with long leg standing X-ray. PSI:
Patient-specific instrument; PSG: Patient specific matched guides; CT: Computed tomography;
MRI: Magnetic resonance imaging; CR: Computed radiography.
Trumatch Visionaire PSI Signature Conventional
P
value
Number of patients 15 13 14 15 60
Mean age, yr (range) 72 (57-90) 72 (63-82) 69 (52-86) 68 (56-74) 65 (50-83) 0.097
Male, n (%) 6 (40) 7 (54) 7 (50) 7 (47) 34 (57) 0.967
Mean BMI (range) 30 (23-36) 30 (23-37) 30 (26-36) 30 (23-38) 28 (21-37) 0.373
Severity OA
Moderate, n (%) 13 (87) 11 (85) 13 (93) 14 (93) 53 (88) 0.991
Severe, n (%) 2 (13) 2 (15) 1 (7) 1 (7) 7 (12) 0.959
Table 2 Baseline demographics per alignment method
PSI: Patient-specic instrument; BMI: Body mass index; OA: Osteoarthritis.
Figure 1 Anterior-posterior radiograph of a left knee of a female patient.
A: Preoperative severe osteoarthritis; B: Postoperative with the Sigma CR, total
knee arthroplasty (Depuy) in situ.
AB
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IRB-nr.13N09), registered online at the Dutch Trial
Register (NTR4739) and was performed in compliance
with the Helsinki Declaration of 1975, as revised in
2000. All patients were informed and they consented to
providing data for anonymous use.
Statistical analysis
Statistical Package for the Social Sciences V17.0 (SPSS,
Inc., Chicago, IL) for Windows was used. All radiographic
evaluation was performed once for each radiograph,
performed by 2 independent assessors (MS and SH).
Inter class correlation coefficient (ICC) was calculated
to check for inter observer reliability. An ICC ≥ 0.7 was
considered as good correlation. Statistically signicant
differences for radiographs were analyzed with a one-
way ANOVA. The Bonferroni method for correcting for
multiple comparisons was used to reduce the chances
of obtaining false-positive results (type
Ⅰ
errors). Fisher
exact test was used to test differences of proportions.
P-value was considered to be statistically signicant at P
≤ 0.05 for all statistical analyses.
RESULTS
Of the 120 patients included, 3 patients could not
be scanned with MRI and were operated with use of
computed tomography (CT)-based PSG (Signature,
Biomet). Baseline demographics are shown in Table 2.
All guides tted well during the time of operation, there
were no conversions to conventional instrumentation.
All radiographic measurements of both observers were
reliable and ICC’s were excellent (Table 3).
With regard to the individual components, per-
centage of outliers of the FFC (P < 0.000), LFC (P <
0.000) and LTC (P < 0.05) were significantly different
in favour of the PSG group (Table 4). Regarding the
individual different PSG systems, the mean (SD) HKA-
axis (P < 0.000), the FFC (P < 0.000) and LTC (P <
0.000) alignment were signicantly different (Table 5).
The PSG group subdivided into cut- and pin PSG showed
signicant difference regarding the mean FFC (P < 0.022)
and the LTC (P < 0.009) alignment (Table 6).
DISCUSSION
This industry driven technology proved to be safe, reprodu-
cible and easy to use. This leads to a commercial success
compared to other computer-assisted technologies[11].
Although, published results on PSG are contrasted,
even on level
Ⅰ studies. Seven level
Ⅰ studies compared
conventional instrumentation with PSG and compared
different PSG manufacturers. None of them had
measured a signicant difference in outliers of HKA axis
(Table 7). However, Ptzner et al[24], recently published
results comparing conventional instrumentation with
CT and MRI based PSG from 2 different manufacturers,
and between both PSG groups. They found a signicant
difference regarding the outliers in HKA-axis between
MRI based PSG (Visionaire; 7%) and conventional
instruments (43%), but no signicant difference between
Gave consent (
n
= 120)
TrueMatch
n
= 15
Visionaire
n
= 13
PSI
n
= 14
Signature
n
= 15
Conventional
n
= 60
2 patients excluded
due to pacemaker
1 patient excluded
due to movement
during MRI scanning
time
Figure 2 Flowchart study design. PSI: Patient-specific instrument; MRI: Magnetic resonance imaging.
HKA FFC FTC LFC LTC
Inter CC 0.811 0.879 0.883 0.850 0.943
Table 3 Inter observer correlation coefcients
HKA: Hip-knee-ankle angle; FFC: Frontal femoral component; FTC:
Frontal tibial component; LFC: Flexion/extension of the femur component;
LTC: Lateral tibial component; CC: Class correlation coefcient.
Outliers PSG Conventional
P
value
HKA outliers, n (%) 7 (12.28) 11 (18.33) 0.424
Mean (SD) 179.49 (2.24) 178.54 (2.27) 0.015
FFC outliers, n (%) 0 (0) 11 (18.33) 0.000
Mean (SD) 89.44 (1.73) 88.03 (1.73) 0.000
FTC outliers, n (%) 1 (1.75) 0 (0) 1.000
Mean (SD) 89.87 (1.32) 90.37 (1.38) 0.058
LFC outliers, n (%) 9 (15.78) 35 (58.33) 0.000
Mean (SD) 86.09 (2.86) 86.04 (3.14) 0.314
LTC outliers, n (%) 9 (15.78) 25 (41.67) 0.033
Mean (SD) 92.86 (2.64) 87.43 (2.63) 0.000
Table 4 Mean (SD) values and amount of patients and
percentages of outliers of > 3˚ deviation of the planned
alignment and postoperative alignment compared between the
patient specic matched guides and the conventional group
PSG: Patient specic matched guides; HKA: Hip-knee-ankle angle; FFC:
Frontal femoral component; FTC: Frontal tibial component; LFC: Flexion/
extension of the femur component; LTC: Lateral tibial component.
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CT based PSG and conventional instruments, neither
between both PSG systems[24]. This was contrary to what
Victor et al[25] found. They compared 4 different PSG
systems with the conventional technique, operated by 4
surgeons, with more signicant outliers for the FTC and
LTC in favour of the intra- and extramedular technique
(Table 7). Even between the 4 different PSG systems,
percentages of outliers of > 3° deviation of the planned
HKA and LFC angle were signicantly different, ranging
from 6% to 45% and 20% to 82%, respectively[25]
(Table 7). Published level
Ⅰ percentages of outliers in
the frontal and lateral plane for individual components
for both femur and tibia vary and are inconclusive.
Outliers of the FFC for the PSG are comparable or less
than the conventional intramedular technique. Only 2
authors published significant differences in favour of
the MRI based PSG[17,24]. This was in contrast to the
FTC (Table 7). Most of the outcomes are comparable,
however, 2 articles published signicant better outcome
with extramedular rods[25,26]. Only Ng et al[22] found
signicant better outcome with MRI based PSG for the
tibia. LevelⅠ results are very remarkable in regard to the
LTC. These were signicantly better with PSG than with
conventional instrumentation (Table 7). Most notable
are the signicant differences that have been found with
CT based PSG, which scored poorer outcome regarding
to LTC outliers, ranging from 21% to 65%[19,25-27] (Table
7). A possible explanation for these outcomes can be
the limitations in visualization and outlining of intra-
articular cartilage in CT based 3D models[28-31]. Another
explanation, based on our experience, is that CT based
guides were more difcult to place on the bony surface
compared to MRI based guides. Nevertheless, we did not
reveal a signicant difference between the MRI and CT
PSG surgeries for HKA-axis and individual components
for the different planes.
There may be some concerns regarding our radi-
ological measurements. A wide variety of different
analyses in the literature are used to objectively deter-
mine the postoperative position for both the femur
and tibia implants (Table 7). Despite a good ICC for
the evaluation of the frontal and lateral position of both
femur and tibia implants, rotational alignment was not
examined. Most of the literature use long-standing
radiographs, except for 1 paper which used scout CT
scan[17] and two used full-leg CT scans[22,27]. Postoperative
evaluation on 3D-CT have shown to be a valuable tool
to measure position and orientation of both the femur
and tibia components and it is more accurate with
signicantly better femoral rotation alignment after use
of PSG[18,22,32]. Unfortunately, a postoperative 3D-CT is
not routinely performed in our clinic. On the other hand,
plane radiographs are generally applicable for everyone.
This single surgeon experience with different PSG
manufacturers could raise questions about the general
applicability. We had the opportunity to use different
types of PSG and implants. Based on the experience
with TKA, the use of PSG and a possible learning curve,
implementation of a new implant system may be a
Trumatch Visionaire PSI Signature
P
value
HKA outliers, n (%) 3 (20.00) 1 (7.69) 2 (14.28) 1 (6.66) 0.819
Mean (SD) 178.5 (2.3) 181.3 (1.6) 180.6 (1.6) 177.9 (1.8) 0.000
FFC outliers, n (%) 0 0 0 0 1.000
Mean (SD) 89.9 (1.6) 90.1 (1.5) 89.9 (1.2) 87.9 (1.8) 0.000
FTC outliers, n (%) 0 0 1 (7.14) 0 1.000
Mean (SD) 89.3 (1.4) 90.0 (1.2) 89.9 (1.6) 90.6 (1.3) 0.081
LFC outliers, n (%) 2 (13.33) 2 (15.38) 1 (7.14) 4 (26.66) 0.663
Mean (SD) 85.7 (1.6) 85.4 (2.1) 87.4 (1.9) 85.8 (4.5) 0.307
LTC outliers, n (%) 2 (13.33) 4 (30.76) 2 (14.28) 1 (6.66) 0.594
Mean (SD) 92.7 (2.4) 91.2 (3.0) 94.8 (1.2) 92.8 (2.7) 0.000
Table 5 Mean (SD) values and amount of patients and percentages of outliers of > 3˚
deviation of the planned alignment and postoperative alignment compared between the
patient specic matched guides groups
PSI: Patient-specic instrument; HKA: Hip-knee-ankle angle; FFC: Frontal femoral component; FTC: Frontal
tibial component; LFC: Flexion/extension of the femur component; LTC: Lateral tibial component.
Cut PSG Pin PSG
P
value
HKA outliers, n (%) 4 (14.3) 3 (10.3) 1.000
Mean (SD) 179.9 (2.4) 179.3 (2.2) 0.342
FFC outliers, n (%) 0 0 1.000
Mean (SD) 90.0 (1.5) 89.6 (1.8) 0.022
FTC outliers, n (%) 0 1 (3.4) 1.000
Mean (SD) 89.6 (1.3) 90.2 (1.5) 0.115
LFC outliers, n (%) 4 (14.3) 5 (17.2) 1.000
Mean (SD) 85.6 (1.8) 86.6 (3.5) 0.184
LTC outliers, n (%) 6 (21.4) 3 (10.3) 0.477
Mean (SD) 92.0 (2.7) 93.8 (2.3) 0.009
Table 6 Mean (SD) values and amount of patients and
percentages of outliers of > 3˚ deviation of the planned
alignment and postoperative alignment compared between
the cut (
n
= 28, Trumatch and Visionaire) and pin (
n
=
29, patient-specic instrument and signature) patient specic
matched guides group
PSG: Patient specic matched guides; HKA: Hip-knee-ankle angle; FFC:
Frontal femoral component; FTC: Frontal tibial component; LFC: Flexion/
extension of the femur component; LTC: Lateral tibial component.
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potential bias in the outcome[25]. However, research
is mostly performed by high-volume surgeons who
probably easier adapt to a new surgical technique than
low-volume surgeons or residents. PSG could be an
added value in less experienced surgeons due to their
simplicity[19]. On the other hand, we evaluated cut and
pin PSG from different manufacturers with less outliers
compared to the conventional group.
Our primary goal was to investigate the accuracy of
alignment between conventional and PSG and between
different PSG systems compared with published
level
Ⅰ evidence. A comparison on perioperative and
clinical outcome were not made, although there is a
trend towards significant shorter operating time[16-18]
and blood loss[16] with surgeries performed with PSG.
However, published results on component sizing are
inconclusive to come up with a statement[18,19,27].
Finally, even though this study was a consecutive
series compared with a historical cohort and not a
randomized trial, a potential criticism was the sample
size and power of this study.
The present study illustrates that this simplified
surgical technique for TKA is safe and effective with
acceptable radiological outcome. The PSG group shows
signicantly less outliers compared to the conventional
technique. Whether these differences are clinically
relevant is questionable and should be investigated on
the long term. Based on these single surgeon results,
we conclude that PSG are ready for prime time.
ACKNOWLEDGMENTS
The authors want to thank Stef van Hoef for his work
in measuring the alignment on digital long-leg standing
and lateral radiographs. We also thank Dr. Rob Sollie
from Flinders Medical Centre Adelaide, Australia, who
served as external reader, and for his comments that
greatly improved the manuscript.
COMMENTS
Background
Patients with knee osteoarthritis often results in debilitating function of the knee
joint warranting a total knee arthroplasty (TKA). This study aims to present the
radiological results of TKA with use of patient specic matched guides (PSG)
from different manufacturer in patients suffering from severe osteoarthritis of
the knee joint.
Research frontiers
Patients suffering from osteoarthritis of the knee joint can be operated with
use of PSG for TKA from different manufacturer. TKA with PSG has concerns
regarding accurate implant alignment and the long term survival of the TKA
compared to the conventional instrumentation.
Innovations and breakthroughs
In this study, PSG for TKA from different manufacturer restored good biome
chanical axis and individual implant alignment in patients suffering from
moderate to severe osteoarthritis of the knee joint compared to conventional
alignment.
Applications
To summarize, PSG from different manufacturer can be an added value in daily
Outliers (%) > 3°
deviation
PSG system Modality Conventional Control Sample size Signicant outliers (%)
femur/tibia (PSG/conventional) (PSG/conventional)
Boonen et al[16] Signature MRI Intra X-ray 90/90 LFC (49/65)1
Chareancholvanich
et al[17]
PSI MRI Intra/Extra X-ray and CT 40/40 FFC (0/18)1
Chotanaphuti et al[18] TruMatch CT Intra/Extra X-ray and CT 40/40 NA
Hamilton et al[19] TruMatch Scout CT Intra/Extra X-ray 26/26 LTC (65/50)2
Ng et al[22] [Outliers
(%) > 2° deviation]
PSI MRI Intra CT 51/27 FTC (27/67)2, Femoral rotation (16/67)2,
Tibial rotation (22/95)2
Ptzner et al[24] TruMatch CT Intra/Extra X-ray and CT (30/30)/30 HKA (30/7/43)2
Visionaire MRI + X-ray FTC (13/3/23)1
Femoral rotation (1/13 /50)1
Victor et al[25] Signature MRI, CT Intra/Extra X-ray and CT (16/16/16/16)/64 FTC (15/3)1
TruMatch MRI + X-ray LTC (21/3)2
Visionaire MRI HKA (6/25/45/19)1,3
PSI LFC (62/20/20/56)2,3
Kotela et al[26] Signature CT Intra/Extra X-ray 49/46 FTC (39/20)1
Woolson et al[27] TruMatch CT Intra/Extra CT 22/26 LTC (32/8)1
Current study Signature MRI Intra X-ray (15/13/14/15)/60 FFC (022)2
TruMatch CT LFC (16/67)2
Visionaire MRI + X-ray LTC (16/42)1
PSI MRI
Table 7 Published level Ⅰ studies with signicant percentage of outliers of > 3˚ deviation between the patient specic matched
guides and conventional intramedular and/or extramedular alignment method for hip-knee-ankle angle axis, frontal femoral
component, frontal tibial component, exion/extension of the femur component, lateral tibial component and axial rotation of
the femur and/or tibia component controlled with postoperative X-ray (long-leg standing and/or lateral X-rays) and/or computed
tomography
1Statistically signicant different, P ≤ 0.05; 2Statistically signicant different, P ≤ 0.005; 3Outliers > 3° deviation between the different PSG groups. NA:
Not applicable for outliers; PSG: Patient specic matched guides; PSI: Patient-specic instrument; CT: Computed tomography; MRI: Magnetic resonance
imaging; Intra: Intramedular; Extra: Extramedular; HKA: Hip-knee-ankle angle; FFC: Frontal femoral component; FTC: Frontal tibial component; LFC:
Flexion/extension of the femur component; LTC: Lateral tibial component.
COMMENTS
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et al
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TKA practice in patients suffering from moderate to severe osteoarthritis of the
knee joint compared to the conventional instrumentation for TKA.
Peer-review
The authors compared the accuracy of TKA using patientspecic instruments
(PSIs) with that of TKA using the conventional technique. In addition, they
compared the accuracy of 4 different manufactured PSI TKAs. In conclusion,
TKA using PSIs was more accurate than TKA using the conventional method,
and no difference in accuracy was found between the 4 different manufactured
PSI TKAs. Regarding the PSI TKA that was recently developed, more research
studies, including precision, cost, operation time, blood loss, radiation exposure,
and longterm survival, should be conducted in order to examine if it confers
more benets to patients than the conventional TKA. The manuscript could add
new information on PSI TKA regarding its accuracy.
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S- Editor: Song XX L- Editor: A E- Editor: Li D
Schotanus MGM
et al
. Patient specific guides ready for primetime