Early Clinical Outcomes of a New Posteriorly Stabilized Total Knee Arthroplasty Prosthesis: Comparisons with Two Established Prostheses

Article (PDF Available) · September 2017with 293 Reads
DOI: 10.5792/ksrr.16.047
Cite this publication
Abstract
Purpose: We sought to determine whether early clinical performance of new posterior stabilized (PS) knee system, the Vega-PS (Aesculap), is better than that of two established total knee arthroplasty (TKA) prostheses, the E.motion-PS (Aesculap) and the Genesis II (Smith & Nephew) in terms of functional outcomes, patient satisfaction, and incidence of adverse events. Materials and methods: We compared the clinical outcomes of 206 consecutive TKAs using Vega-PS with those of 205 TKAs using E.motion-PS and 216 TKAs using Genesis II at 2 years of follow-up. Results: Overall, the knees with the Vega-PS had better functional outcome scores than the knees with the E.motion-PS, but had similar outcome scores to the knees with the Genesis II, as evident from the American Knee Society knee score (94.2 vs. 92.5 vs. 93.2), Western Ontario McMaster Universities Osteoarthritis (WOMAC) stiffness index (1.8 vs. 2.3 vs. 2.0), WOMAC function index (11.8 vs. 16.8 vs. 18.5), Short Form 36 (SF-36) physical component summary score (41.9 vs. 39.3 vs. 41.6), and SF-36 mental component summary score (50.0 vs. 45.8 vs. 46.9). Patient satisfaction was higher in the Vega-PS and Genesis II groups than the E.motion-PS group. No notable group differences were found in terms of the incidence of adverse events. Conclusions: The Vega-PS, a newly developed PS fixed bearing prosthesis, had comparable or superior clinical performance in comparison with the two established fixed or mobile bearing PS prostheses.
Figures - available via license: CC BY-NC 4.0
Content may be subject to copyright.
Introduction
Total knee arthroplasty (TKA) has emerged as a durable ap-
proach to replicate the healthy osseous anatomy and restore
natural knee joint kinematics. However, recent expansion of indi-
cations for TKA in a younger and more active patient population
demands further improvement for greater durability1,2) and func-
tion3,4). Many new implant designs have incorporated modifica-
tions to achieve the goal of better clinical outcomes and implant
longevity. However, these designs do not guarantee improved
results, and several new prostheses were reported to have unex-
pected problems or unsatisfactory outcomes5-7). Therefore, with
any new design, it is prudent to maintain a close surveillance of
its performance and safety from the outset. Although a short-
term outcome analysis is limited in predicting long-term success,
information from short-term studies is still valuable for early de-
tection of adverse events, if any, originating from new prostheses.
Posterior stabilized (PS) knee prostheses have cam and post
mechanisms to provide stability in flexion, increase range of mo-
tion (ROM), and improve the quadriceps lever arm. Moreover,
multiple mid-term and long-term follow-up studies have evi-
Early Clinical Outcomes of a New Posteriorly Stabilized
Total Knee Arthroplasty Prosthesis: Comparisons with
Two Established Prostheses
Nimesh P. Jain, MS1, Sung Yup Lee, MD2, Vivek M. Morey, MS3, Suri Chong, MD2, Yeon Gwi Kang, MS2, and
Tae Kyun Kim, MD2
1Department Orthopaedics, North Cumbria University Hospitals NHS Trust, Carlisle, UK; 2Department of Orthopaedic Surgery, Seoul National University Bundang
Hospital, Seongnam, Korea; 3Department of Orthopedics, Datta Meghe Institute of Medical Sciences, Wardha, India
Purpose: We sought to determine whether early clinical performance of new posterior stabilized (PS) knee system, the Vega-PS (Aesculap), is better
than that of two established total knee arthroplasty (TKA) prostheses, the E.motion-PS (Aesculap) and the Genesis II (Smith & Nephew) in terms of
functional outcomes, patient satisfaction, and incidence of adverse events.
Materials and Methods: We compared the clinical outcomes of 206 consecutive TKAs using Vega-PS with those of 205 TKAs using E.motion-PS and
216 TKAs using Genesis II at 2 years of follow-up.
Results: Overall, the knees with the Vega-PS had better functional outcome scores than the knees with the E.motion-PS, but had similar outcome
scores to the knees with the Genesis II, as evident from the American Knee Society knee score (94.2 vs. 92.5 vs. 93.2), Western Ontario McMaster
Universities Osteoarthritis (WOMAC) stiffness index (1.8 vs. 2.3 vs. 2.0), WOMAC function index (11.8 vs. 16.8 vs. 18.5), Short Form 36 (SF-36)
physical component summary score (41.9 vs. 39.3 vs. 41.6), and SF-36 mental component summary score (50.0 vs. 45.8 vs. 46.9). Patient satisfaction
was higher in the Vega-PS and Genesis II groups than the E.motion-PS group. No notable group differences were found in terms of the incidence of
adverse events.
Conclusions: The Vega-PS, a newly developed PS fixed bearing prosthesis, had comparable or superior clinical performance in comparison with the
two established fixed or mobile bearing PS prostheses.
Keywords: Arthroplasty, Replacement, Knee, Prosthesis design, Outcome assessment
Original Article
Knee Surg Relat Res 2017;29(3):180-188
https://doi.org/10.5792/ksrr.16.047
pISSN 2234-0726 · eISSN 2234-2451
Knee Surgery & Related Research
Received September 1, 2016; Revised (1st) January 6, 2017;
(2nd) March 12, 2017; Accepted April 7, 2017
Correspondence to: Tae Kyun Kim, MD
Department of Orthopaedic Surgery, Joint Reconstruction Center,
Seoul National University Bundang Hospital, 82 Gumi-ro 173 beon-gil,
Bundang-gu, Seongnam 13620, Korea
Tel: +82-31-787-7196, Fax: +82-31-787-4056
E-mail: osktk@snubh.org
180
This is an Open Access article distributed under the terms of the Creative Commons
Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/)
which permits unrestricted non-commercial use, distribution, and reproduction in any
medium, provided the original work is properly cited.
Copyright © 2017 KOREAN KNEE SOCIETY www.jksrr.org
Knee Surg Relat Res, Vol. 29, No. 3, Sep. 2017 181
denced good function, movement, and survivorship of PS knee
prostheses8,9). However, certain drawbacks have been reported
with PS knee prostheses, namely large intercondylar bone stock
removal to accommodate the femoral cam10), dislocation of the
cam11), patellar clunk syndrome12), and wear of the tibial post13).
Subsequently, there have been many attempts to modify the de-
signs of PS knee prostheses in order to address their problems as
well as to achieve more physiologic and stable knee kinematics.
Several studies in the past have shown that changes in compo-
nent geometry and modularity with the PS designs have led to
improved short- and long-term results14-16) in addition to permit-
ting greater surgical flexibility in severe osteoarthritis cases16).
A new PS knee prosthesis system, Vega-PS (Aesculap; B. Braun,
Tuttlingen, Germany), is designed to improve TKA outcomes. Its
distinguishing characteristics include a low profile intercondylar
box, reduced posterior condyle length, and narrowed mediolater-
al width of the femoral component, along with an anterior cutout
and increased post inclination of the tibial insert. It was designed
to achieve high performance, including high flexion and shape
optimization to avoid overhang. However, no clinical informa-
tion regarding this new prosthesis is available yet to validate
its functional performance and safety. We sought to determine
whether early clinical performance of this new prosthesis is bet-
ter than two established TKA prostheses, the E.motion-PS and
Genesis II, in terms of functional outcomes, patient satisfaction,
and incidence of adverse events. We had two hypotheses: 1) The
functional outcomes and patient satisfaction in patients having
Vega-PS prostheses implanted are better than the outcomes and
satisfaction in patients having the previously established PS type
TKA prostheses implanted. 2) There is no increased incidence of
adverse events in the knees replaced with the Vega-PS.
Materials and Methods
Seven hundred and eighty-six TKAs were performed by one
surgeon (KTK) between May 2006 and May 2012. These in-
cluded 240 TKAs using a new PS knee system, the Vega-PS (Fig.
1), along with 546 consecutive TKAs performed for advanced os-
teoarthritis using two established PS knee systems, the E.motion-
PS (Aesculap), a mobile bearing PS prosthesis (257 knees), and
the Genesis II (Smith & Nephew, Memphis, TN, USA), a fixed
bearing PS prosthesis (289 knees). All of the Vega-PS TKAs were
performed in the years after we completed the 257 E.motion-PS
TKAs. In contrast, the 289 Genesis II TKAs were done through-
out the entire study period. The implant selection was at the sur-
geons discretion without any selection criteria. We included only
patients with a diagnosis of primary osteoarthritis, scheduled for
unilateral TKA, between May 2006 and May 2012. We excluded
patients with a diagnosis of secondary osteoarthritis or a past
medical history of previous hip or spine surgery, in an attempt to
reduce potential outcome confounders. A total of 159 patients,
including 16 patients with a history of prior hip and spine prob-
lems, 24 patients with secondary arthritis, 89 patients with other
systemic comorbidities that might interfere with the benefits of
the replaced knee, 15 patients with postoperative complications
affecting outcomes, and 15 patients who died due to unrelated
causes, were excluded from the study. Thus, data from a total of
627 patients were used for analysis (Vega-PS, n=206; E.motion-PS,
n=205; and Genesis II, n=216). In the Vega-PS group, the mean
age of the patients was 70.7 years and the number of female pa-
tients was 198 (96.1%). In the E.motion-PS group, the mean age
of the patients was 68.3 years, and the number of female patients
was 196 (95.6%), while in the Genesis II group, the mean age was
Fig. 1. The photographs show the Vega-PS prosthesis. The anterior and
posterior narrowing of the femoral component with a low profile inter-
condylar box minimizes interference with the surrounding soft tissues.
Fifty-five degrees posterior inclination of the post acts to avoid post-
edge loading for better load distribution, prevents impingement with
the extensor mechanism, and increases resistance to dislocation. The
deepened anterior cutout of the insert allows smooth articulation with
the patellar tendon.
182 Jain et al. Short-Term Results of Vega-PS Prosthesis
69.7 years, and the number of female patients was 203 (98.5%).
This study was approved by the Institutional Review Board of our
hospital, and all patients provided informed consent concerning
the use of medical records.
All surgeries were performed by a single surgeon, using the me-
dial parapatellar approach. The patella was routinely resurfaced
and all implants were fixed with cement (Palacos; Heraeus Kulzer
GmbH, Hanau, Germany). We used measured resection, com-
bined with gap balancing techniques without navigation.
There were not any significant differences in surgical techniques
between the mobile and fixed bearing instruments. After surgery,
a compressive dressing was applied, with immobilization of the
knee for 24 hours. The knees were then placed in a continuous
passive-motion machine. On the second postoperative day, the
drain and compressive dressing were removed, and all patients
were encouraged to walk with crutches or a walker and started
active and passive ROM exercises. The knee ROM exercises and
weight bearing were gradually increased.
All clinical information was prospectively collected, using pre-
designed data sheets, and maintained in a database by an inde-
pendent investigator (LSY). The retrospective evaluation of all the
data was done with a minimum follow-up of 2 years. The clinical
information gathered included demographic data, preoperative
clinical status, and postoperative clinical status at 12 months and
2 years. Patient evaluation using the outcome scales was done at 2
years after surgery. For this purpose, knee ROM, American Knee
Society (AKS) scores17), Western Ontario McMaster Universities
Osteoarthritis Index (WOMAC) scales18), and Short Form 36
(SF-36) scores19) were used. In addition, patient satisfaction was
evaluated at the 2 year follow-up using a 1–4 point Likert scale,
based on the grading system developed by the British Orthopae-
dic Association, which is divided into four levels, i.e., enthusiastic,
satisfied, not committed, and disappointed20). The knee motion
arc was expressed in terms of flexion contracture and maximum
flexion angle. An independent investigator (LSY) measured the
flexion contracture and maximum flexion angles to the nearest 5°
by using a standard (38 cm) clinical goniometer, with the patient
in the supine position.
The radiographic assessment was performed at 2 years after
surgery to measure five parameters: mechanical tibiofemoral
angle (MTFA), coronal femoral prosthesis alignment, coronal
tibial prosthesis alignment, sagittal femoral prosthesis align-
ment, and sagittal tibial prosthesis alignment (Fig. 2). Two of the
authors took all radiographic measurements using full-length
weight bearing anteroposterior radiographs, and lateral radio-
graphs of the operated limb. To achieve the same foot rotation
MTFAMTFA
TCLA
TCLA
a
b
A B C D FE
MTFAMTFA
b
a
FCLAFCLA
Fig. 2. (A) The radiograph shows the preoperative mechanical tibiofemoral angle (MTFA). (B) The radiograph shows the postoperative MTFA. (C)
The radiograph shows the femoral component lateral angle (FCLA), defined as the lateral angle between the femoral mechanical axis and a line con-
necting the most distal points of the medial and lateral condyles of the femoral component. (D) The radiograph shows the the tibial component lat-
eral angle (TCLA), defined as the lateral angle between the tibial mechanical axis and a line parallel to the top surface of the tibial component. (E) The
radiograph shows the femoral component flexion angle. To assess the sagittal alignment of the femoral component, we measured the angle between
the line perpendicular to the tangent line of the femoral component box (a) and the line connecting the anterior cortical point of 10 cm proximal to
the joint line and the anterior point of the meta-epiphysis junction before metaphyseal diverging (b). (F) The radiograph shows the tibial component
posterior slope. To assess the sagittal alignment of the tibial component, we measured the angle between the line parallel to the upper surface of the
tibial tray (b) and the line perpendicular to the tangent line of the anatomical axis (the posterior cortical line of tibia at two points, 5 cm and 15 cm
distal to the joint line) of the proximal tibia (a).
Knee Surg Relat Res, Vol. 29, No. 3, Sep. 2017 183
angle, a reference template was positioned on the platform of our
plain radiographic system. All radiographic images were digitally
acquired using a picture archiving and communication system
(PACS; Infinitt, Seoul, Korea). Assessments were performed on a
20-inch LCD monitor in portrait mode using the PACS software.
To determine intra- and inter-observer reliabilities of the radio-
graphic assessments, the two investigators performed all radio-
graphic assessments in 20 randomly selected radiographs twice,
with an interval of 1 week. The intra- and inter-observer reliabili-
ties were then evaluated using intraclass correlation coefficients,
which were found to be >0.80 for all measurements. Since the
measurements were judged as reliable, measurements taken by a
single investigator (LSY) were used in the final analyses.
In order to gauge overall limb alignment, we measured the
MTFA of the knee, which was defined as the angle formed by the
intersection between the mechanical axis of the femur (the line
from the femoral head center to the femoral intercondylar notch
center) and the tibia (the line from the ankle talus center to the
center of tibial spine tips) (Fig. 2A and B). A negative value was
given to the angle of the knees in varus alignment. To assess the
coronal alignment of the femoral component, we measured the
femoral component lateral angle (FCLA), defined as the lateral
angle between the femoral mechanical axis and a line connecting
the most distal points of the medial and lateral condyles of the
femoral component (Fig. 2C). The coronal femoral prosthesis
alignment was calculated by subtracting the FCLA from 90, and
accordingly, a negative value was given to the angle of varus ori-
entation of the femoral component. To assess the coronal align-
ment of the tibial component, we measured the tibial component
lateral angle, (TCLA) defined as the lateral angle between the
tibial mechanical axis and the line parallel to the top surface of
the tibial component (Fig. 2D). We calculated the coronal tibial
prosthesis alignment by subtracting the TCLA from 90°, and
accordingly, a negative value was assigned to the angle for varus
orientation of the tibial component. To assess the sagittal align-
ment of the femoral component, we measured the angle between
Table 1. Comparison of Demographic Characteristics, Preoperative Mechanical Axis (MA) and Outcome Scales among the Vega-PS, E.motion-PS,
and Genesis II Groups
Variabl e Vega-PS
(n=206)
E.motion-PS
(n=205)
Genesis II
(n=216) p-value p-valuea)
P-V V-G P-G
Sex (female, %) 198 (96.1) 196 (95.6) 203 (98.5) 0.199
Age (yr) 70.7 (5.6) 68.3 (5.2) 69.7 (5.8) <0.001 <0.001 >0.05 0.033
Height (cm) 151.5 (6.0) 151.9 (6.0) 151.5 (5.8) 0.733
Weight (kg) 61.5 (8.7) 63.0 (8.2) 63.9 (9.9) 0.023 >0.05 0.020 >0.05
Body mass index (kg/m2)26.8 (3.5) 27.3 (3.0) 27.8 (3.8) 0.013 >0.05 0.010 >0.05
Preoperative MA (°) –10.7 (4.8) –10.1 (5.1) –11.6 (6.7) 0.827
Motion arc (°)
Flexion contracture 11.2 (6.3) 9.9 (6.5) 12.0 (6.6) 0.006 (0.022) 0.152 (0.223) 0.005 (0.019) 0.685 (1.000)
Maximum flexion 135.6 (13.8) 135.9 (13.5) 135.0 (14.2) 0.527 (0.782)
AKS score
Knee 46.6 (9.5) 45.9 (8.1) 45.7 (8.3) 0.586 (0.745)
Function 58.4 (9.8) 57.5 (10.0) 56.5 (13.2) 0.250 (0.221)
WOMAC
Pain 9.8 (4.3) 12.2 (4.6) 11.0 (4.5) <0.001 (<0.001) <0.001 (<0.001) 0.032 (0.036) 0.016 (0.017)
Stiffness 4.4 (2.1) 4.9 (2.0) 4.4 (1.9) 0.011 (0.013) 0.031 (0.050) 0.021 (0.019) 1.000 (1.000)
Function 34.1 (13.9) 41.2 (14.5) 39.6 (12.2) <0.001(<0.001) <0.001 (<0.001) 0.813 (0.667) <0.001 (<0.001)
Short Form 36
PCS 31.6 (8.0) 29.8 (7.1) 30.1 (8.1) 0.051 (0.053)
MCS 48.4 (11.5) 41.1 (12.3) 41.6 (12.3) <0.001 (<0.001) <0.001 (<0.001) 1.000 (1.000) <0.001 (<0.001)
Values are presented as mean (standard deviation).
P-V: E.motion-PS vs. Vega-PS, P-G: E.motion-PS vs. Genesis II, V-G: Vega-PS vs. Genesis II, AKS: American Knee Society, WOMAC: Western
Ontario McMaster Universities Osteoarthritis Index, PCS: physical component summary, MCS: mental component summary.
a)p-value is listed along with the adjusted p-value (after taking the preoperative differences as covariates).
184 Jain et al. Short-Term Results of Vega-PS Prosthesis
the line perpendicular to the tangent line of the femoral compo-
nent box and the line connecting the anterior cortical point of 10
cm proximal to the joint line and the anterior point of the meta-
epiphysis junction before metaphyseal diverging (Fig. 2E). A
negative value was given to the angle for extension of the femoral
component, while a positive value was given to the angle for flex-
ion of the component. To assess the sagittal alignment of the tibi-
al component, we measured the angle between the line parallel to
the upper surface of the tibial tray and the line perpendicular to
the tangent line of the anatomical axis (the posterior cortical line
of the tibia at two points, 5 cm and 15 cm distal to the joint line)
of the proximal tibia (Fig. 2F). A positive value was given to the
posterior slope of the tibial component and a negative value was
given to the anterior slope of the component.
Statistical analyses were carried out using SPSS ver. 21.0 (IBM
Co., Armonk, NY, USA), and a p-value <0.05 was considered
significant. Knees with the Vega-PS were compared to knees with
the E.motion-PS and knees with the Genesis II for functional out-
come scales and incidence of adverse events. Patient satisfaction
was also measured and compared. The Kolmogorov-Smirnov test
was used to confirm that the clinical outcome scores, including
maximal flexion, were normally distributed. As preoperative dif-
ferences could have confounding effects on postoperative func-
tional outcomes, all three groups were compared with respect to
their demographic characteristics and preoperative clinical status
(Table 1). There were a few parameters, which were different
among the groups, and their confounding effects were adjusted
using the analysis of covariance (ANCOVA) test, when compar-
ing postoperative outcomes. To determine the significance of the
differences in the functional outcome scores among the three
implant systems, post hoc analysis was performed.
To determine adequacy of our sample size, we performed an
a priori power analysis using the two-sided hypothesis test at
an alpha level of 0.05. Sixty-four knees were required to detect a
difference of 5° in a motion arc and a 6% difference in outcome
scales. We considered these cutoff values to be clinically impor-
tant because motion arc was measured to the nearest 5°, and a 6%
difference of maximum score has been suggested as the minimal
clinically important difference for WOMAC and SF-36 indices14).
Thus, the sample sizes used were regarded as adequate.
Results
Knees replaced with the Vega-PS had comparable func-
tional outcomes with the Genesis II but better results than the
E.motion-PS. In the knees with the Vega-PS, almost all of the
measured outcome scales improved at 2 years postoperatively
(p<0.05) (Table 2). On comparisons among the three groups, the
mean AKS knee score (Vega-PS, 94.2; E.motion-PS, 92.5; and
Genesis II, 93.2) (p=0.046) and WOMAC stiffness score (Vega-
PS, 1.8; E.motion-PS, 2.3; and Genesis II, 2.0) (p=0.020) were
found to be better for the knees replaced with the Vega-PS than
for the knees with the E.motion-PS (Table 3). Although knees
replaced with the Vega-PS and Genesis II revealed similar results
in terms of most of the outcome scores, the Vega-PS knees had
better WOMAC function scores compared with the Genesis II
group (Vega-PS, 11.8; E.motion-PS, 16.8; and Genesis II, 18.5)
(p<0.001). Conversely, knees replaced with the Genesis II had
better AKS function scores than knees with the Vega-PS and
knees with the E.motion-PS (Genesis II, 95.7; Vega-PS, 93.0;
E.motion-PS, 93.6) (p=0.022). Nevertheless, the three groups
showed similar results in terms of flexion contracture, maximal
flexion achieved, WOMAC pain score, SF-36 mental component
summary (MCS) scores, and physical component summary (PCS)
scores (Table 3). Patient satisfaction was higher in the Vega-PS
and Genesis II groups than the E.motion-PS group (p=0.001)
(Table 4). No notable differences were found in limb and prosthe-
sis alignment among the three groups postoperatively (Table 5).
Table 2. Comparison of Preoperative and 2-Year Postoperative Out-
comes of the Vega-PS Prosthesis
Variabl e Preoperative Postoperative
2-year p-value
Motion arc (°)
Flexion contracture 11.2 (6.3) 0.3 (1.5) <0.001
Maximum flexion 135.6 (13.8) 132.4 (10.4) <0.001
Range of motion 124.4 (17.3) 132.1 (10.6) <0.001
AKS score
Knee 46.6 (9.5) 94.2 (4.5) <0.001
Function 58.4 (9.8) 93.0 (9.2) <0.001
WOMAC
Pain 9.8 (4.3) 2.3 (2.7) <0.001
Stiffness 4.4 (2.1) 1.8 (1.5) <0.001
Function 34.1 (13.9) 11.8 (9.7) <0.001
Short Form 36
PCS 31.6 (8.0) 41.9 (8.0) <0.001
MCS 48.4 (11.5) 50.0 (11.6) <0.001
Values are presented as mean (standard deviation).
AKS: American Knee Society, WOMAC: Western Ontario McMaster
Universities Osteoarthritis Index, PCS: physical component summary,
MCS: mental component summary.
  • Article
    Full-text available
    There is little information about the management and clinical outcomes of the periprosthetic fracture after total knee arthroplasty (TKA) with a stem extension. The purposes of this study were to demonstrate management of the periprosthetic fractures after TKA with a stem extension, to report treatment outcomes, and to determine whether dual-plate fixation is superior to single-plate fixation regarding the radiographic bone union time and incidence of metal failure.This retrospective study included 15 knees with periprosthetic fractures after TKA using a stem extension. We demonstrated the fracture characteristics and management according to the fracture location and implant stability. The radiographic union time was determined. Complications, range of motion, and functional outcomes, including Western Ontario and McMaster Universities Osteoarthritis Index and Knee Society Score were assessed. Periprosthetic fractures after TKA with stem extension were 1 metaphyseal fracture without implant loosening, 7 diaphyseal fractures adjacent to the stem without implant loosening, 3 diaphyseal fractures away from the stem without implant loosening, and 4 fractures with implant loosening.Treatment included immobilization using a long leg cast, open reduction and internal fixation (ORIF), and re-revision TKA. There was no difference in functional outcomes and range of motion pre- and posttreatment. The complications included 2 cases of subsequent implant loosening. Patients in the dual-plating required a shorter bony union time than those in the single-plating (2.4 ± 1.1 vs 7.4 ± 2.2 months; P = .003).Periprosthetic fractures after TKA with stem extension could be managed individually according to the fracture location and implant stability. Complications were not uncommon even if patients were able to return to their preinjury functional level posttreatment. To avoid complications after ORIF, the dual plate was superior to the single plate, and subtle implant loosening should not be overlooked.
  • Article
    Purpose: This study was performed to prospectively compare the clinical and radiographic results between mobile-bearing (MB) and fixed-bearing (FB) TKAs using ceramic titanium nitride (TiN)-coated prostheses. Methods: Seventy MB and 70 FB TKAs using TiN-coated prostheses (ACS®) were prospectively evaluated. There were no differences in demographic characteristics between the two groups. Clinically, the Knee Society knee and function scores, WOMAC, and range of motion (ROM) were compared. Considering the possibility of a kinematic change in the polyethylene (PE) insert and a decrease in ROM following MB TKA, serial changes in the ROM were also compared. The thickness of the PE insert was compared according to the size of the femoral component. Radiographically, the alignment and positions of the components were compared. Results: There were no differences between the two groups in clinical scores or ROM (n.s.). The maximum flexion increased from 133.5° ± 8.3° to 137.6° ± 5.5° across all time points in the MB group. The serial maximum flexion angles did not differ between the two groups over time (n.s.). The average thickness of the PE insert was greater in the MB group (12.0 ± 1.9 vs. 11.2 ± 1.6 mm, respectively, p = 0.008), especially when a large femoral component was used (12.7 ± 1.9 vs. 11.0 ± 1.5 mm, p = 0.005). The pre- and postoperative mechanical axes and positions of the components did not differ between the two groups (n.s.). Conclusions: TiN-coated MB TKA showed no significant advantage over FB TKA. The selection of bearing design would be clinically insignificant when using the TiN-coated TKA prosthesis. Level of evidence: II.
  • Article
    Purpose: It is unknown whether the conforming superiority of ultracongruent (UC) inserts over posterior stabilized (PS) inserts, due to an increased anterior lip for prevention of anterior displacement of the condyles during knee flexion, leads to better knee scores or greater knee stability in arthroplasty patients. This meta-analysis compared clinical outcomes, intraoperative kinematics, sagittal stability, and range of motion (ROM) between groups with either UC or PS inserts in primary total knee arthroplasty (TKA). Methods: Studies that recorded clinical outcomes, intraoperative kinematics, sagittal stability, and ROM in patients who underwent primary TKA with UC or PS inserts were included in the meta-analysis. Subgroup analyses based on differences in flexion angles were performed for intraoperative kinematics. Results: Thirteen studies met the criteria for inclusion in the meta-analysis. The UC and PS insert groups reported similar pain scores (95% CI - 0.15 to 0.16; n.s.) and function scores (95% CI - 0.30 to 0.14; n.s.). In contrast, femoral rotation during flexion (95% CI - 0.06 to 6.35; p = 0.05), posterior femoral translation during flexion (95% CI - 2.74 to - 0.15; p = 0.03), tibial sagittal laxity at 90° (95% CI 2.91 to 7.72; p < 0.0001), and ROM (95% CI - 4.84 to - 1.53; p = 0.0002) differed significantly between the groups. Subgroup analyses revealed that the pooled data for femoral rotation were significantly different between groups: 60°, 4.09 (p < 0.00001); 90°, 7.94 (p < 0.00001); and 120°, 8.16 (p < 0.00001). Furthermore, pooled data for posterior femoral translation were significantly different between groups: 90°, - 3.70 (p < 0.00001); and 120°, - 3.96 (p < 0.00001). Conclusions: There were no significant differences in clinical outcomes between the groups with UC and PS inserts. However, the UC insert group showed significantly greater external femoral rotation, less posterior femoral translation, greater tibial laxity in the sagittal plane, and less ROM than the PS insert group. Based on the results of the current meta-analysis, in substituting the PCL, PS inserts are preferable to UC inserts due to more favourable kinematics and stability, even though both inserts have equivalent clinical outcomes. Level of evidence: Therapeutic study, Level II.