International Journal of Research in Orthopaedics | May-June 2019 | Vol 5 | Issue 3 Page 485
International Journal of Research in Orthopaedics
Saraf HR et al. Int J Res Orthop. 2019 May;5(3):485-489
http://www.ijoro.org
Original Research Article
Comparative study of early functional outcome between cruciate
retaining knee and 3D knee: who is more satisfied?
Hrushikesh Ramesh Saraf, Shreepal Munot*
INTRODUCTION
The primary goal of total knee arthroplasty (TKA) is to
relief pain and to improve the quality of life. Outcome of
various studies are typically very good.1-3 But quite a few
times patient do not get satisfactory range of motion and
functional outcome. A variety of prosthesis have been
designed with most of the implants either substituting a
resected PCL or allow for its preservation.4,5 During
recent times, in addition to cruciate substituting or
retaining, mobile or fixed bearing, there are studies
regarding rotation of pivot, centre of rotation (COR) of
the knee joint.6-10 Implants were designed with COR in
the medial compartment which was explained by high
congruity of femoral epicondyle with concave medial
tibial plateau and has been accepted in literature for
years.11-13
But more recently studies suggested that during dynamic
activities and walking COR found to be lateral
compartment of knee joint but during kneeling and
squatting COR shift to the medial side.14-19
The effect of lateral COR on TKA’s functional outcome
and patient’s satisfaction is still missing in the literature.
So current study is initiated to gather evidence of this
ABSTRACT
Background:
With growing demand on quality of life, there is drastic increase in total knee arthroplasty (TKA)
surgeries and accordingly there is increase in research on TKA design to get the best possible outcome. Commonly
known TKA designs are PCL substituting or retaining, fixed bearing or mobile bearing. Now the scientific research
shifted to center of rotation of angulation (CORA) of knee i.e. medial or lateral pivot. 3D knee is based on lateral
pivot system and designed to match the natural knee. The purpose of this study is to compare 3D knee with cruciate
retaining (CR) knee functionally and also to assess the patient’s level of satisfaction.
Methods:
20 patients each included in 3D knee and CR knee group from June 2016 to June 2018 who satisfied the
inclusion and exclusion criteria. Patients were followed up for 1 year. Their functional outcome assessed using knee
society score (KSS) part 1 and 2. Also patient’s knee range of motion documented separately.
Results:
Postoperatively there is improvement in knee society score in both the groups. 3D knee showed significant
better KSS score than CR knee groups in first 3 months but as the patients followed up for 1 year both groups reached
similar KSS score and also similar knee range of motion.
Conclusions:
3D knee showed satisfactory outcome when compared with CR knee and definitely provides a step
ahead in search of natural knee.
Keywords: 3D knee, Cruciate retaining knee, Lateral pivot, Knee society score
Department of Orthopaedics, Shashwat Hospital, Pune, Maharashtra, India
Received: 24 January 2019
Revised: 09 March 2019
Accepted: 12 March 2019
*Correspondence:
Dr. Shreepal Munot,
E-mail: drshreepalmunot@gmail.com
Copyright: © the author(s), publisher and licensee Medip Academy. This is an open-access article distributed under
the terms of the Creative Commons Attribution Non-Commercial License, which permits unrestricted non-commercial
use, distribution, and reproduction in any medium, provided the original work is properly cited.
DOI: http://dx.doi.org/10.18203/issn.2455-4510.IntJResOrthop20191789
Saraf HR et al. Int J Res Orthop. 2019 May;5(3):485-489
International Journal of Research in Orthopaedics | May-June 2019 | Vol 5 | Issue 3 Page 486
new TKA articular design concept that incorporates
programme congruency in bilateral compartment (3D
knee) aiming to provide inherent antero-posterior knee
stability and recreates the motion pattern of natural knee
and to compare its functional outcome and patients
satisfaction with cruciate retaining(CR) knees.
METHODS
This prospective study done in shashwat hospital pune
from June 2016 to June 2018. Total 40 patients were
included in the study (20 patients in 3D knee group and
20 patients in CR knee group). Inclusion criteria were age
>60 years; moderate to severe knee pain which disturb
the daily routine activities; patient with tricompartmental
osteoarthritis knee with less than grade III varus
deformity and up to 20 degree FFD. Exclusion criteria
were age >80 year; inflammatory arthritis; valgus knee,
Charcot joints; previous surgery, infection; severe
comorbid conditions; severe varus– grade IV, FFD more
than 20.
All patients operated at same centre by single surgeon.
Well informed, written consent taken before the surgery.
All patients operated under spinal/epidural anaesthesia on
standard OT table. All aseptic precautions taken like
modular OT setup, body exhaust system to minimise
infection. Standard anterior midline incision, medial
Parapatellar approach used for all the cases (Figure 1).
Other steps almost same in both the system with only two
main difference. (1) In CR knee PCL is preserved but in
3D knee PCL can be maintained or excised depending on
its integrity; (2) in CR knee soft tissue balancing done
with usual measured resection technique but in 3D knee
balancing achieved with gap balancing technique where
extension gap is matched with flexion gap using gap
balancer jig. Post op pain management includes nerve
blocks, NSAIDS (COX-2 inhibitors), gabapentin,
cryotherapy, CPM.
Patient discharged on DAY 4 with FWB walking with
walker, knee exercises, commode training and suture
removal done on 15th day. All patients followed up every
month and knee society score calculated on 1, 2, 3, 12
months post-surgery.
Principle questions related to satisfaction consists of
asking the patient regarding overall function of the knee,
ability to perform normal activities of daily living,
satisfaction with degree of pain relief and categorised as
very satisfied, somewhat satisfied, somewhat dissatisfied,
very dissatisfied.
Figure 1: (A) 3D knee; B) CR knee.
The 3D knee incorporates a hemispherical lateral condyle and
tibial articulation to provide definitive AP translational control
while providing for proper axial rotation. The asymmetric
femoral component incorporates a constant sagittal radius from
−150to 800 while providing progressively decreasing articular
constraint with higher flexion to allow femoral condyle
rollback.
Statistical analysis
Data statistically analysed using Fisher’s exact test for
categorical variables and student’s T test for continuous
variables. Two tailed P value of less than 0.05 considered
to be significant.
RESULTS
The demographic data is given in Table 1. The mean ages
of both the groups of patients were comparable. There
was no statistically significant difference in the age, sex,
pre-operative deformity, pre-operative Range of motion,
pre-operative knee society score (p>0.05) among both the
groups.
Assessment of knee society score part I,II done for both
groups and means calculated at 4th week,8th week,12th
week,1 year and compared at each follow. 3D knee group
patients showed better knee society score at the end of
12th weeks (p<0.05) but at the end of 1 year both groups
showed similar scores (p>0.05) (Table 2, Figure 2).
Table 1: Preoperative parameters of patients in both groups.
3D knee
CR knee
P value
Age (mean)
69.5±4.0years
68.4±4.6years
0.381
Sex (F:M)
14:6
15:5
>0.999
Preoperative knee society score (mean)
Part 1
39.50±11.33
37.25±13.19
0.566
Part 2
33.25±16.08
30.5±16.58
0.885
Preoperative knee ROM (mean)
1160±100
1170±90
0.676
FFD
5.50±5.38
5.25±5.25
0.882
Varus deformity
8.15±3.56
8.10±3.58
0.964
M-male, F-female, ROM –range of motion, FFD-fixed flexion deformity.
A
B
Saraf HR et al. Int J Res Orthop. 2019 May;5(3):485-489
International Journal of Research in Orthopaedics | May-June 2019 | Vol 5 | Issue 3 Page 487
Table 2: Comparison of postoperative knee society score of both groups.
KSS1
KSS2
3D knee
CR knee
P value
3D knee
CR knee
P value
4 weeks
68.05±8.82
62.25±7.52
0.031
63.25±7.48
57.75±5.50
0.011
8weeks
74.70±7.79
67.75±6.97
0.005
69.50±8.41
62.75±5.25
0.004
12 weeks
79.30±7.61
73.40±7.80
0.020
76.75±5.91
70.75±7.30
0.007
1 year
94.20±3.19
94.60±2.91
0.681
94.25±5.20
94.00±3.84
0.864
KSS –knee society score, CR – cruciate retaining
Table 3: Comparision of post-operative knee range of motion in both groups.
Knee ROM
3 D Knee
CR Knee
P value
4weeks
91.75±6.34
86.00±7.88
0.015
8 weeks
105.50±8.57
99.00±8.37
0.020
12 weeks
115.25±7.69
109.50±8.41
0.030
1 year
123.25±6.74
124.25±6.74
0.641
ROM- range of motion
Figure 2: Comparative improvement in KSS in both
the groups.
Figure 3: Comparison of knee range of motion
between both groups.
Figure 4: Patient’s level of satisfaction among both the
groups.
Patients knee range of motion also documented
separately at each visit and improvement noted at each
visit and comparison done between both the groups.
Again 3D knee group patient had significantly better knee
range of motion during initial 3 months compared to CR
knee group(p<0.05) but both groups showed similar
range of motion at the end of 1 year (p>0.5) (Table 3,
Figure 3).
Patients satisfaction was classified into very satisfied,
somewhat satisfied, somewhat dissatisfied, very
dissatisfied at 3 months and at the end of 1 years. 3D
knee group patients showed better satisfaction in early
post-operative period though insignificant (p=0.261)but
by the end of 1 year both groups are equally satisfied
(Figure 4).
50.
60.
70.
80.
90.
100.
4th wk 8th wk 12th wk 1 year
3D knee KSS
1
3D knee KSS
2
CR knee KSS
1
CR knee KSS
2
91.75
105.5 115.25 123.25
86
99 109.5
124.25
4 week 8 week 12 weeks 1 year
3D knee CR knee
CR knee 3 months
3D knee 3 months
cr knee 1 year
3D knee 1 year
0
2
4
6
8
10
12
14
16
18
CR knee 3 months 3D knee 3 months
cr knee 1 year 3D knee 1 year
Saraf HR et al. Int J Res Orthop. 2019 May;5(3):485-489
International Journal of Research in Orthopaedics | May-June 2019 | Vol 5 | Issue 3 Page 488
DISCUSSION
The successful outcome of any TKA is not only
dependent on proper preoperative planning but also
partially dependent upon TKA design with suitable
congruity and constraint to provide adequate knee joint
stability not only during walking but also during daily
activity like kneeling, squatting which give patient sense
of normal knee.20 There are several research articles to
understand kinematics of knee joint. Few studies reports
that COR of the knee is in the medial compartment13,21-25
but instantaneous COR does occur in the medial
compartment in only about 25% of the stance. Medial
pivoting motion is required during non-ambulatory
activities such as squatting and during passive range of
motions.26 The studies by Andriacchi et al, Lawfortune et
al, Banks et al, showed that COR of the knee is in lateral
compartment for most of the time (70%) during stance
phase of normal walking.27,28,20 Though ideal TKA design
should permit both medial and lateral pivoting at different
phase of stance but it is always a challenge to design a
knee that mimic exactly the natural knee.
The principle question for any TKA design with or
without PCL is to address the knee stability during
dynamic activities like gait, stair climbing and whether
the tibiofemoral articulation reduces unproductive AP
sliding without compromising the knee range of motion.
In this current TKA design (3D) knee PCL can be either
meticulously maintained or summarily excised
demonstrating the adaptability of this TKA design with
any of the surgical technique.
The most common design accepted throughout the world
to provide AP stability is cam and post design. But
several complications like increased strain at prosthesis –
bone interface and wear of tibial post has been
documented with these designs.29-33 O’rourke et al
reported osteolysis in 16% of PS knee, Mikulak et al
reported osteolysis and 3% revision rate in PS knee,
similarly Han et al reported 38% loosening rate in PS
knee at 2-4 years follow up.31-33 As 3D and CR knee
design does not depend on cam and post mechanism, it
definitely provide advantage in avoiding such
complications associated with cam and post design.
In this study we compared CR knee with 3D knee
because both design mimic more normal knee
kinematics.CR knee have the advantage of preservation
of bone, increased proprioception and greater
stabilisation of the prosthesis. 3D knee as described
earlier is based on lateral pivot system that is required
during most of the stance phase. In literature there is
hardly any study to compare the functional outcome of
3D knee and CR knee. We observed 3D knee patients
outscoring CR knee patients in KSS, knee range of
motion, level of satisfaction during first 3 month of
operation. Reason can be 3D knee congruity mimic
natural knee design which may give patient better sense
of stability and confidence to rehabilitate early, CR knee
being bone preserving knee also provide same advantages
with time. So both groups have similar functional
outcome at the end of 1 year with good range of knee
motion. Both groups of patients are equally satisfied at
the end of one year.
CONCLUSION
3D knee and CR knee both being bone preserving design
and closer to natural knee kinematics had similar
functional outcome, knee range of motion and patient
level of satisfaction at the end of 1 year, though 3D group
showed better score during early postoperative period.
The concept of lateral pivot definitely provides a good
prospective for the search of natural knee.
Limitations
Sample size is small and Long term follow up is required
to further study the complications, survivorship and end
results
Funding: No funding sources
Conflict of interest: None declared
Ethical approval: Not required
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Cite this article as: Saraf HR, Munot S. Comparative
study of early functional outcome between cruciate
retaining knee and 3D knee: who is more satisfied?. Int
J Res Orthop 2019;5:485-9.
