Session 4: Knee
Torsdag den 22. oktober
09:00 – 10:30
Chairmen: Henrik Husted / Mogens Berg Laursen
Christian Skovgaard Nielsen, Audrey Nebergall , James Huddleston, Christopher Barr, Henrik Malchau, Anders Troelsen
The Harris Orthopeadic Laboratory, Orthopeadic Department, Massachusetts General Hospital, Boston, USA; Department of Orthopaedic Surgery, Stanford University Medical Center, Stanford, California, USA; Department of Orthopeadics , Sahlgrenska University Hospital Gothenburg, Sweden; Department of Orthopaedic surgery, Copenhagen University Hospital Hvidovre, Copenhagen, Denmark,
Background: Consequences of tibial overhang and component
malaligment in knee replacement (TKA) have been
investigated, however, there is no consensus in
relation to patient reported outcome measures
(PROMs). KOOS (Knee Injury and Osteoarthritis
Outcome Score), specifically the subscale KOOS
pain, is used to monitor pain.
Purpose / Aim of Study: The aim of this prospective multicenter study was to
investigate the associations between 1) tibial
overhang and KOOS pain and 2) malalignment of
TKA components including overall malalignment and
KOOS pain, both 1 year after surgery.
Materials and Methods: 323 patients from 10 centers in Europe, US, Asia
and Australia were enrolled between October
2011 and Feb 2014.
Demographic data, postoperative X-ray, and 1
year KOOS pain were collected. Overhang was
defined as any portion of the tibial tray that
exceeds tibial bone. There were 4 categories of
malalignment: overall (<2.5° or >7.5° valgus);
femoral (<2° or >7° valgus); tibial (<3° varus or
>3°); and combined (defined as both tibial and
femoral malalignments). Any 1 Y KOOS pain
score of < 70 was used to represent
unsatisfactory pain based earlier on follow-up
Multiple logistic regression was used to assess
Findings / Results: 68.4% were females, mean BMI was 30.7(SD ± 8.2)
and mean age was 66.0 (SD ±8.2).
Significant association was observed between medial
overhang and 1Y KOOS pain of < 70 (p =0.04).
18.5% of patients had medial overhang. For overall,
tibial, femoral, and combined malalignment as for
anterior and lateral overhang no significant
associations were found in relation to 1 year KOOS
pain of < 70.
Conclusions: A significant association was shown between medial
overhang and a 1 year KOOS pain less than 70,
which demonstrates a significantly reduced chance
for entering a satisfactory pain category 1 year after
Christian Skovgaard Nielsen, Audrey Nebergall, James Huddleston, Christopher Barr, Henrik Malchau, Anders Troelsen
The Harris Orthopeadic Laboratory, Orthopeadic Department, , Massachusetts General Hospital, Boston, USA; The Harris Orthopeadic Laboratory, Orthopeadic Department, Massachusetts General Hospital, Boston, USA; Department of Orthopaedic Surgery, Stanford University Medical Center, Stanford, California, USA; Department of Orthopaedic Surgery , Sahlgrenska University Hospital Gothenburg, Sweden; Department of Orthopaedic surgery, Copenhagen University Hospital Hvidovre, Copenhagen, Denmark,
Background: Patient Reported Outcome Measures (PROMs) are
a reliable means of assessing preoperative pain and
function as well as clinical improvement after Knee
Replacement (TKA). There may be differences in
preoperative characteristic and improvement of
patients undergoing TKA between countries.
Purpose / Aim of Study: The aim of this prospective multicenter study was to
investigate differences between USA, Europe, Asia,
and Australia (4 regions) in preoperative
Osteoarthritis (OA) and KOOS (Knee Injury and
Osteoarthritis Outcome Score) as well as the
improvement in KOOS 1 year after TKA.
Materials and Methods: In 10 centers 435 patients were enrolled from
Europe (4), USA (2), Asia (2) and Australia (1).
Demographics, preoperative X-rays, and KOOS
were collected. KOOS consist of 5 individual
subscales: pain, symptoms, function in daily
living, function in sport, and quality of life (QoL).
Delta KOOS was defined as the improvement in
each subscale KOOS from preoperative score to
1 year after TKA.
Preoperative OA was graded according to the
Kellgren-Lawrence (KL) scoring system.
Parametric tests were used for statistics.
Findings / Results: There were significant differences in gender, age,
and BMI between the 4 regions (p < 0.001, for all).
For OA-severity, no significant difference was
observed between the 4 regions (p = 0.25).
Regarding preoperative pain (p = 0.13) no significant
difference was found between the regions. For Delta
KOOS significant differences were shown for all
subscales between the 4 regions (p < 0.01).
Conclusions: Significant demographics differences were shown
between the 4 regions. For OA severity and
preoperative pain, no significant differences were
observed, indicating similar radiological criteria and
pain thresholds prior to TKA in the 4 regions. There
were significant differences in improvement after
TKA between the regions.
Christoffer C Jørgensen, Frederik Pitter, Martin Lindberg-Larsen, Henrik Kehlet
Section for Surgical Pathophysiology & The Lundbeck Foundation Centre for Fast-Track Hip and Knee Re, Rigshospitalet; Department of Orthopedics & The Lundbeck Foundation Centre for Fast-Track Hip and Knee Replacment, Bispebjerg and Frederiksberg University Hospitals
Background: Elderly total hip (THA) and knee arthroplasty
(TKA) patients have increased length of
hospital stay (LOS), readmissions and non-
home discharge. However, the role of
patient and department-specific
characteristics within a fast-track protocol is
uncertain. Furthermore, differences
between “medical” and “surgical”
complications are rarely mentioned.
Purpose / Aim of Study: To investigate LOS>4 days, 90-days
readmissions and discharge destinations in
patients ≥85 years in relation to patient-
characteristics and department of surgery.
Materials and Methods: Observational prospective study in 8 fast-
track departments. 90-days follow-up from
the Danish Patient Registry and patient
Findings / Results: 549 (4% of 13775) procedures were in
patients ≥85 years, of which 12% had ≥4
conventional surgical risk-factors. In
dep2 more patients had preoperative
anemia (42%) and in dep7 more patients
used walking aids (86%) or had
psychotropic treatment (29%) (p<0.05).
Median LOS was 3 days and 27% had
LOS>4 days. Of these, 83% were
“medical”, mainly anemia requiring
transfusion and mobilization issues.
Preoperative anemia and use of walking
aids were associated with LOS >4 days
(OR:1.54 (95%CI:1.03–2.31) and 1.84
(95%CI:1.18–2.86)). Dep1 had more
(43%), and dep7 had fewer (13%)
patients with LOS>4 (p<0.05). 38
patients (6.9%) were not discharged to
home, more in dep1 (24%) and fewer in
dep3-5 (0-1%)(p<0.05). 90-day
readmission rate was 18%, more in dep2
(26%) and less in dep7 (10%)(p<0.05).
Of readmissions 80% were “medical”,
mainly falls and disproved
thromboembolic events. Mortality was
Conclusions: Patients >85 years can successfully
undergo a fast-track regime, but patient and
department-related factors influence LOS,
readmissions and discharge destination.
Attention to pre- and postoperative anemia
and prevention of “medical” complications is
Daan Koppens, Maiken Stilling, Stig Munk, Jesper Dalsgaard, Søren Rytter, Torben Bæk Hansen
Orthopaedic department, Regional Hospital Holstebro; Ortopaedic department, Regional Hospital Holstebro
Background: The Sigma unicompartmental knee arthroplasty
(UKA) is a relatively new implant offering a low 5–
year revision rate of 5.5% (2.9-10.1) in the Australian
arthroplasty register. Early implant migration can be
assessed by radiostereometric analysis (RSA).
Migration is a predictor of implant loosening/revision.
Purpose / Aim of Study: We evaluate migration of the Sigma UKA using RSA.
Materials and Methods: During December 2012 to December 2013, 45
cemented, uncoated, fixed-bearing medial Sigma
UKA were implanted in 45 patients (21 male; mean
age 63 years; SD 9.7). Stereoradiographs were
obtained postoperatively, at 4 months (4M) (N=37), 1
year (1Y) (N=40), and 2 years (2Y) (N=17) after
surgery. Model-based RSA was used to analyse
migration of the femoral and tibial components with
respect to their rigid bone-marker model. At the time
of the conference, 2Y follow-up data will be nearly
Findings / Results: Median maximal total point motion (MTPM) (95%CI)
for the femoral component was 0.54mm (0.44 0.66)
at 1Y and 0.50mm (0.35 0.73) at 2Y (t-test p=0.64),
and for the tibial component 0.45mm (0.35 0.56) at
1Y and 0.52mm (0.32 0.86) at 2Y (t-test p=0.54).
Continuous migration (MTPM>0.2mm at any follow-
up after 1Y) of the tibial component was seen in 6
knees. One patient was revised 19 months after
Conclusions: Pijls suggests a threshold for MPTM for the tibial
component of TKA at 1Y of 0.54 as acceptable. This
level is associated with a low revision rate in the
arthroplasty registries. Our data are comparable with
an MTPM for the tibial component at 1Y of 0.45.
Continuous migration is observed in 6 knees at 2Y
follow-up. These knees have a 20% chance of
loosening2. Our study shows low migration of the
Sigma UKA at 2Y follow-up, 6 knees are at risk for
Katrine Borum, Thomas Houe, Olsen Claus, Henrik Schrøder
Ortopædkirurgisk afd, Næstved Sygehus
Background: A new way of improving quality and logistics in TKA
surgery might be Patient Specific Instrumentation
(PSI), providing cuttingblocks and predetermining
component sizes from a MR or CT.
Purpose / Aim of Study: To report early results with PSI in a Danish
Materials and Methods: A retrospective review of 38 patients operated at
Næstved Sygehus with insertion of a Zimmer®
NexGen TKA with the use of PSI. All knees had been
operated by two experienced knee surgeons
between October 2014 and June 2015. We searched
the medical records, The Danish knee arthroplasty
register and the files from the Zimmer® PSI- online
Findings / Results: 42 patients were selected for PSI. 2 patients had
to drop out due to change of surgeon. Another 2
patients dropped out, because their scans were
dismissed for technical reasons by Zimmer®.
Thus 38 patients were reviewed: 16 men and 22
women, mean age 66,1 years (50-82), BMI 29
(21-44), all suffering from osteoarthritis. It took
70,8 days from time of indication until the
12 out of the 38 (31,6%) patients were per-
operatively converted to conventional operating
technique, because the predetermined size didn’t
fit. Four femurs and 8 tibias were converted. 9/12
of the converted patients got larger sizes that
pre-planned, equally divided between femoral and
The converted operations had an operating time
of 57,9 min compared to 54,4 min when the PSI
system was used successfully. In the Danish
Knee Arthroplasty Register (2013) the operating
time was on average 68 minutes.
Conclusions: With an average time from indication to operation of
almost 71 days, and a conversion rate of 31,6%
(12/38), our early results with PSI were not good.
However, given proper education of surgeons, the
potential logistic advantages warrants further
Kristian Horsager, Maiken Stilling, Peter Bo Jørgensen, Bart L. Kaptein
Orthopedic Research Department E, Aarhus University Hospital; Department of Orthopaedic Surgery, Leiden University Medical Center, Netherland
Background: Traditionally, RSA is used for static recordings
of joint implants at fixed time intervals to follow
fixation over time. Dynamic RSA allows for
assessment of implant fixation during loaded
Purpose / Aim of Study: To asses inducible micromotions (IMM) of the
Oxford UKA tibial component and evaluate IMM
for fixation methods (cemented vs. cementless),
tibial radiolucent lines (RLL), component
alignment and clinical outcome scores.
Materials and Methods: 15 patients (12 males and 3 females, mean
age: 69 years, n = 7 cemented/n = 8
cementless) with a well-fixed Oxford UKA
(mean in-situ: 4.4 years) were invited. Five
of these had tibial RLL. Each patient was
recorded with dynamic RSA (10 fr/sec)
during a continuous step-up / step-down
motion on a 30 cm. box. IMM was calculated
for the tibial component with respect to the
tibia bone. Postoperative component
alignment (posterior slope and varus slope)
was measured with Model-based RSA, RLL
was measured on screened X-rays, and
clinical outcome was evaluated as OKS,
AKSS and VAS.
Findings / Results: All tibial components had IMM which followed
the highest loadings during the step-cycle
(p<0.001) with subsidence up to -0.06 mm
(95%CI: -0.10 ;-0.03). Tibial component IMM
was similar for cemented and cementless
fixation (p>0.19). Patients with tibial RLL had
0.4° (95%CI: 0.06 ; 0.72) larger medio-lateral
tilt (p=0.03). Postoperative posterior slope of
the tibial plateau correlated with posterior tilt at
mean 4 years follow-up (p=0.008). No
correlation was found between IMM and
clinical outcome scores (p>0.07). Further
analysis are ongoing.
Conclusions: All Oxford UKA had IMM of the tibial component
during a step-up cycle. RLLs and component
alignment influenced the magnitude of IMM.
Dynamic RSA is a promising clinical tool for the
evaluation of functional implant fixation and
Madeline Therese Kudibal, Thomas Kallemose, Anders Troelsen, Henrik Husted, Kirill Gromov
dept. of orthopedic surgery , hvidovre hospital
Background: Background: Patient- and surgery
related parameters as well as
preoperative disability may influence
postoperative outcome following
primary TKA. The role that ethnicity
and level of education plays in
preoperative disability in patients
scheduled to undergo primary TKA
surgery is unknown.
Purpose / Aim of Study: Aim: In this prospective cohort study
we investigate the role that ethnicity
and level of education plays in
preoperative disability in patients
undergoing primary TKA.
Materials and Methods: Methods: We identified 651 patients
receiving primary TKA between Oct.
2013 and Dec. 2014, at our institution.
Patient demographics, including
ethnicity (place of birth) and level of
education as well as preoperative
disability, including Oxford Knee Score
(OKS) and pain on a Visual Analogue
Scale (VAS) were registered
preoperatively. Regression analysis
was performed to identify independent
factors affecting preoperative OKS and
VAS pain scores.
Findings / Results: Results: 46 (7%) of patients were
borne outside DK. 182 (28%) and 317
(49%) of patients had <9 years and
9-12 years of education respectively.
Adjusted for potential confounders
(age, gender and BMI), patients born
outside DK had higher VAS pain (1.0;
95%CI (0.4-1.6) and lower OKS scores
(3.6; 95%CI (1.7-5.5)) preoperatively.
Patients with >12 years of education
had higher VAS pain (0.7; 95%CI
(0.2-1.1) and lower OKS scores (1.9;
95%CI (0.6-3.3)) preoperatively.
Conclusions: Conclusion: Ethnicity and level of
education plays a role in preoperative
disability in patients undergoing
primary TKA. Further investigations on
what effect ethnicity and education
plays in utilization of medical services
and outcome following TKA are
Morten Grove Thomsen, Roshan Latifi, Thomas Kallemose, Kristoffer Barfoed, Henrik Husted, Anders Troelsen
Dept. of Orthopedic surgery, Copenhagen University Hospital Hvidovre, Denmark
Background: When evaluating the outcome after TKA
increasing emphasis has been put on
patient perceived outcome, such as patient
satisfaction and ability to perform activities
of daily living. To accommodate this, a new
scoring system, the Forgotten Joint Score
(FJS), has been developed.
Purpose / Aim of Study: The purpose of this study was to develop
and validate a Danish version of the FJS.
Materials and Methods: A danish version of the FJS questionnaire
was created according to internationally
adopted standards. 360 patients previously
treated with primary TKA were invited to
participate in the study (follow-up 1-4
years). Of these, 315 patients were included
in the validity study and 150 patients in the
reliability study. Correlation between the
Oxford Knee Score (OKS) and FJS was
calculated and test-retest evaluation was
performed. Ceiling effect was defined as
patients reaching a score within 10% of the
maximal achievable score.
Findings / Results: The reliability study revieled a strong
correlation between the FJS- and OKS
scoring systems with a correlation
coefficient of 0.81[0.77;0.85] (p < 0.001).
The test-retest showed almost perfect
reliability for the FJS total score (ICC = 0.91
[0.88;0.94]) and at least substantial
reliability for the individual FJS sub scores
(ICC > 0.79). We found a high level of
internal consistency amongst the 12
individual FJS sub scores (cronbach’s α =
0.96). The ceiling effect for the FJS was
12% compared to 26% for the OKS.
Conclusions: The danish version af the FJS
demonstrated high test–retest reliability and
validity. The FJS did not carry the same
degree of ceiling effect as found in the OKS.
The FJS is a usefull and reliable tool when
evaluating potential small differences in
knee performance of patients with good
clinical results after TKA.
Nikolaj Milandt, Tine Nymark, Hans Jørn Kolmos, Claus Emmeluth, Søren Overgaard
The Orthopaedic Research Unit, Department of Orthopaedic Surgery and Traumatology, Odense University Hospital; Department of Clinical Microbiology, Odense University Hospital
Background: Iodine impregnated incision drape (IIID)
was deemed ineffective in preventing
surgical site infection (SSI) in a
recent systematic review. Some evidence
suggests a potential increase in SSI
risk as a result of IIID use, possibly
from promotion of skin recolonization.
IIID is sparsely investigated in
orthopaedics. An increase in the number
of viable bacteria in the surgical field
of an arthroplasty has a potential to
increase operative infection risk
Purpose / Aim of Study: To investigate if IIID increase
bacterial recolonization rates compared
to no drape use under conditions of
simulated total knee arthroplasty (TKA)
Materials and Methods: 20 patients scheduled for TKA were
recruited. Each patient had one knee
randomized for draping with IIID, while
the contralateral knee was left bare,
thus the patients served as their own
control. Operating theatre conditions
and perioperative procedures of a TKA
were simulated. Cup-scrub samples were
collected from the skin of each knee
prior to disinfection and on 2 occasions
after skin-preparation, 75 minutes
apart. Bacterial quantities were
estimated by spread plating under
aerobic conditions. Outcome was measured
as colony forming units per cm2 of skin
Findings / Results: Following skin-disinfection we found no
significant difference in bacterial
quantities between the intervention and
the control knee (p = 0.823). Neither
did we see any difference after 75
minutes of simulated surgery (median
0.00 vs. 0.26 log10 CFU, p = 0.601).
Bacterial quantities had not increased
at the end of surgery when compared to
baseline in either groups, thus no
recolonization was detected (p = 0.852
and 0.304, respectively)
Conclusions: IIID did not increase bacterial
recolonization rates in simulated TKA.
This study does not support the
hypothesis that IIID promotes bacterial
recolonization and postoperative
Nikolaj Winther, Claus L jensen, Thomas Lind, Claus Munk Jensen, Henrik Schrøder, Michael Mørk Petersen
Background: Regenerex is a novel porous titanium
construct with a 3-dimensional porous
structure and biomechanical characteristics
close to that of normal trabecular bone. It is
believed that these characteristics will
facilitate bone ingrowth and secure a better
fixation to the host bone, thus increasing the
Purpose / Aim of Study: The aim of this study was to compare this
novel construct to a well-proven porous
plasma sprayed tibial (PPS) implant after
total knee arthroplasty.
Materials and Methods: Sixty-one patients scheduled for a TKA
were randomized to receive either the novel
titanium construct or the PPS tibial
component. Radiostereometric analysis of
the tibial components was performed
postoperatively at 3, 6, 12 and 24 months.
Maximum total point motion (MTPM) and
segment motion of the implant were
Findings / Results: Knee and function scores improved
significantly from preoperatively to 2-year
follow-up in both groups.The Regenerex
and the PPS both had the majority of
migration appearing during the first 3
months and then stabilized. MTPM in the
Regenerex group between 12 and 24
months were 0.06 mm with a total migration
of 1.7 mm. In the PPS group MTPM
between 12 and 24 months was 0.15mm
and total migration 1.35mm. the Regenerex
had significant lower migration rates
between 12 and 24 month compared with
the PPS implant (p=0.03).
Conclusions: The migration pattern expressed by rotation
and translation about X-, Y-and, Z –axes
were similary and considered stable in both
groups.If we excluded a group of high
migrators (n=12) the MTPM in both groups
could be reduced to approximately 1mm,
close to that of cemented implants.The
results of the novel titanium construct look
promising in terms of migration and with a
significant improvement in KSS score and
WOMAC score at all follow-up and
comparable with other uncemented implants
Roshan Latifi, Kirill Gromov, Madeline Frederiksen, Thomas Kallemose, Henrik Husted, Anders Troelsen
Orthopedics surgery, Hvidovre Hospital
Background: The definitions of an ideal alignment in total
knee arthroplasty (TKA) are much debated.
The pre- and postoperative alignment of the
knee and its components are hypothesized
to play a significant role in patient outcomes
Purpose / Aim of Study: The aim of this prospective cohort study is
to investigate pre- and postoperative overall
knee alignment and component alignment
and their relation to patient reported
outcomes one year after TKA
Materials and Methods: Through our TKA database, we have
identified 570 patients operated between
May 2013 and June 2014 at our hospital.
Secondary TKAs and bilateral simultaneous
TKAs were excluded, leaving 334 patients
for analysis. Oxford Knee score (OKS) was
obtained preoperatively and at 1-year
follow-up. Logistic regression was used to
analyze risk factors for improvement of less
than 10 OKS point. The model included the
9 radiologic parameters and was adjusted
for gender, age and BMI
Findings / Results: Preoperative tibial, femoral and overall knee
alignment were not significantly affecting
the postoperative outcome. Isolated
postoperative coronal femoral component
alignment did not affect outcome whereas
postoperative coronal tibial component
alignment of more than 3 degrees varus
(OR = 2.6, CI = 1.2-5.9, p =0.020) and
overall postoperative knee alignment of
more than 7.5 degrees valgus (OR = 2.5, CI
= 1.0-5.6, p=0.040) were associated with
Conclusions: The patients with the post-operative overall
knee alignment more than 7.5 degrees in
valgus or the post-operative tibial
component coronal alignment more than 3
degrees in varus are in a higher risk of
obtaining poor results at 1 year follow-up.
Therefore, according to this study, it is
suggested that surgeons pay special
attention to overall knee and tibial
component alignment during the surgery
Mikkel Rathsach Andersen, Nikolaj Wnther, Thomas Lind, Henrik Schrøder, Michael Mørk Petersen
Ortopædkirurgisk afd., Rigshospitalet
Background: Loss of bone stock as a response to the
bone trauma, immobilisation and stress
shielding related to joint replacement surgery
increases the risk of fracture of the distale
femur after total knee arthroplasty (TKA).
Purpose / Aim of Study: This study investigates the adaptive bone
remodelling of the distal femur after
Materials and Methods: We performed a 2 year follow up of 53
patients (mean age 61.5 (38-70) years,
F/M=27/26, BMI 29.5) who because of
osteoarthritis received an uncemented
TKA. The patients participated in a
randomised study regarding the tibial
component, but all received a NexGen
CR-Flex Porous Femoral Component.
Measurements of bone mineral density
(BMD) of the distal femur using DEXA
were performed postoperatively and
after 3, 6, 12 and, 24 months. BMD
(g/cm2) was measured in 3 regions of
interest (ROI) in the periprosthetic bone
of the distal femur. Statistics: Paired and
unpaired t-test for normally distributed
data (P< 0.05 were considered
Findings / Results: In the distal femur significant changes in
BMD were seen after 24 months of follow-
up and BMD decreased by 23,6% in the
anterior ROI behind the anterior flange of the
prosthesis (p<0.001), 10,1.0% in the
posterior ROI (p<0.001) and 5,5% in the
most proksimal ROI (p<0.001).
Conclusions: We found highly significant BMD-changes in
the distal femur after uncemented TKA, most
pronounced in the anterior ROI, where a
decrease in BMD of almost 25% was seen.
Taking the expected age related decay in
BMD in this age group in to consideration,
the decrease was substantial and must be
considered to predispose to periprosthetic