Session 11: Knee Arthroplasty
16. November
13:30 - 15:00
Lokale: 202-205
Chair: Julie R Brandt and Kirill Gromov
94. Denosumab decreases the subsidence of cementless tibial implants by suppression of bone resorption. A randomized, double-blinded RSA study in 54 patients with 5 years follow-up
Karina Nørgaard Linde1, 2 , Søren Rytter1, 2, Bente Langdahl2, 3, Frank Madsen1, Maiken Stilling1, 2
1. Department of Orthopedics, Aarhus University Hospital;
2. Department of Clinical Medicine, Aarhus University;
3. Department of Endocrinology and Internal Medicine, Aarhus University
Hospital
Background: Cementless tibial implants migrate initially
until osseointegration.
Aim: We hypothesized that Denosumab
decreases migration and improves fixation
of cementless tibial implants.
Materials and Methods: A prospective, double-blinded, randomized
study including 54 patients operated with a
total knee arthroplasty (TKA) using a
cementless tibial implant (Regenerex).
Patients were randomized to two injections
subcutaneously (second postoperative day
and 6 months postoperative) of Denosumab
(60mg) (Dmab group) or 1 ml NaCl
(9mg/ml) (placebo group). We compared
Maximum Total Point Motion (MTPM) and
subsidence (Y-translation) using
Radiostereometry Analysis (RSA), bone
turnover markers (CTX, P1NP), and
periprosthetic Bone Mineral Density (p-
BMD) by dual-energy X-ray absorptiometry
(DXA). RSA, DXA and blood samples were
obtained postoperative and at 2-, 6-, 12-
and 24 weeks and at 1-, 2-, and 5-years
follow-up.
Results: The Dmab group had significantly less tibial
implant subsidence than the placebo group
at 2- and 5-years follow-up (p<0.04). At 5
years follow-up, mean tibial implant
subsidence was -0.20 mm (95% CI: -0.41;
0.00) in the Dmab group and -0.51 mm
(95% CI: -0.72; -0.31) in the placebo group.
MTPM throughout follow-up and continuous
migration (MPTM between 1- and 2-years
follow-up) were similar between groups
(p>0.05). Bone resorption (CTX) was in the
first year after surgery lower in the Dmab
group than in the placebo group (p<0.001),
bone formation (P1NP) was similar
throughout follow-up, except at 1-year
follow-up where P1NP was lower in the
Dmab group (p=0.02). P-BMD was
generally higher in the Dmab group until 12
months follow-up, but similar thereafter
(p>0.09).
Interpretation / Conclusion: Two Denosumab injections given with a 6
months interval after TKA surgery resulted
in lower subsidence of cementless tibial
implants compared to placebo throughout
follow-up. Bone resorption measured
systemically was suppressed and there was
a pattern of a higher early postoperative p-
BMD in the Dmab group compared with the
placebo group. However, p-BMD and CTX
were similar after 12 months indicating the
treatment did not have a lasting effect on
the bone.
95. Comparing Bone Mineral Density In Cemented And Uncemented Femoral And Asymmetrical Tibial Component Design In Total Knee Arthroplasty. - A Part Of A Randomized Control Trial Design Using Dual-Energy X-Ray Absorptiometry
Müjgan Yilmaz1, Gunnar Flivik2, Thomas Lind3, Anders Odgaard1, Michael Mørk Petersen1,
1. Rigshospitalet, Department of Orthopedic Surgery
2. Skane University Hospital, Lund, Sweden
3. Gentofte Hospital, Hellerup, Denmark
Background: Bone mineral density (BMD) tends to
decrease after TKA mainly caused by
surgical trauma, immobilization, stress-
shielding and foreign body reaction.
Clinically, a decrease in BMD is associated
with the breaking strength of the bone,
which is a related cause of periprosthetic
fractures.
Aim: This study aimed to analyze BMD changes
around cemented and uncemented femoral
and asymmetrical tibial components
following TKA surgery.
Materials and Methods: Patients in this study were included as part
of a randomized controlled trial evaluating
migration measured with radiostereometric
assay. Randomization was performed with
1:1 allocation with group A (uncemented
Trabecular Metal coated Persona® TKA,
Zimmer Biomet, Warsaw, Indiana) or group
B (cemented Persona® TKA, Zimmer
Biomet, Warsaw, Indiana).
A total of 66 patients were included of which
two patients did not get the allocated
treatment and one patient withdrew
consent.
Preoperative and postoperative after 1
week, 3 months, 6 months, 12 months and
24 months dual-energy X-ray
absorptiometry (DEXA) measurements were
performed.
DEXA measurements of the distal femur
and proximal tibia were analysed using
region of interest (ROI). An unpaired t-test
was used to evaluate differences in BMD
between the two groups after 24 months.
Approval from the scientific ethical
committee (case no. H-16035883), and
Danish Data Protection Agency (case no.
2012-58-0004), were obtained and
registered at clinicaltrial.gov
(NCT03563131).
Results: Femoral component: The highest decrease
in BMD was observed in ROI I (cemented:
23.9% and uncemented: 32.6%). A
significant difference between groups after
24 months was found in ROI I (p=0.00439)
whereas ROI II (p=0.203) and ROI III
(p=0.776) were non-significant.
Tibial component: The highest decrease in
BMD was observed in ROI I (cemented:
10.4% and uncemented: 5.05%). There
were no significant changes between
groups after 24 months (ROI I p=0.883, ROI
II p=0.106 and ROI III p=0.247).
Interpretation / Conclusion: The highest decrease in BMD is observed in
the anterior femur with a significant
difference between, groups which can be
clinically important due to the risk of
periprosthetic fractures. No significant
changes between tibial components were
observed.
96. Monoblock versus Modular tibia insert in cementless TKA - 7 years results from a RCT with RSA data
Mikkel Rathsach Andersen1, Nikolaj Sebastian Winther2, Thomas Lind1, Henrik Morville Schrøder2, Gunnar Flivik3, Michael Mørk Pedersen2
1. Department of Orthopeadics, Gentfote Hospital
2. Department of Orthopeadics, Rigshospitalet
3. Department of Orthopeadocs, Skånes Universitets Hospital
Background: Backside wear of the polyethylene insert in total
knee arthroplasty (TKA) has been described to
produce clinically significant levels of
polyethylene debris, which can lead to aseptic
loosening of the tibia components. Monoblock
design eliminates backside wear of the
polyethylene and therefore could improve
longterm implant fixation.
This randomized trial compares monoblock to
modular polyethylene inserts with 7 years follow
up including Radiostereometric Analysis (RSA)
data.
Aim: To compared monoblock and modular cementless
TKA designs in a randomized clinical trial with RSA
data, clinical outcome and longterm follow-up.
Materials and Methods: : 65 patients (mean age 61 years) were
randomized to receive either monobloc (n=33) or
modular (n=34) cementless Zimmer Nexgen
(TMT) tibia component and a cementless CR-
Flex Porous Femoral Component. 35 patients
(monoblok=18) (modular=17) completed 7 years
follow-up. RSA and clinical outcome score was
done postoperatively after weight bearing and
after 3, 6, 12, and 24 months. The primary
endpoint of the study was comparison of the
tibial component migration (maximum total point
motion (MTPM)) of the 2 different implant
designs.
Results: There was no statistically significant difference in
MTPM between the groups at 3 months (p = 0.2) or
at 6 months (p = 0.1), but at 12, 24 and 84 months
of follow-up there was a significant difference in
MTPM of 0.36 mm (p = 0.02), 0.42 mm (p = 0.02)
and 39 mm (p=0.02) between groups, with the
highest average amount of migration 1.17 (.39-2.0)
mm in the modular group. Continuous migration
(from 12-84 months) was 0.13 mm in the monoblock
group and 0.16 mm and in modular groups with no
statistically significant difference (0.45). The largest
translational and rotational migrations were a
subsidence and a posteriorly tilt.
Interpretation / Conclusion: In this study group we did not detect a significantly
different continuous migration for cementless
monoblock tibia design when compared to modular
design. The difference in initial migration between
the groups, we believe should not be attributed to
the elimination of backside wear in the monoblock
design group.
97. The Oxford Knee Score should be reported as two separate domains instead of one total score; assessment of data from the SPARK study using confirmatory factor analysis
Christian Fugl Hansen1, Michael Krogsgaard1, Anne Mørup-Petersen2, Anders Odgaard3, Karl Bang Christensen4
1. Department of Orthopaedic Surgery and Traumatology, Copenhagen University
Hospital, Bispebjerg; 2. Department of Orthopaedic Surgery, Copenhagen
University Hospital, Herlev-Gentofte; 3. Department of Orthopaedic Surgery,
Copenhagen University Hospital, Rigshospitalet; 4. Department of Biostatistics,
University of Copenhagen.
Background: The Oxford Knee Score (OKS) is a 12-item
patient reported outcome measure (PROM),
developed for patients having a total knee
arthroplasty (TKA) but widely used to assess the
impact of knee osteoarthritis (OA). A
prerequisite for a PROM to be considered an
adequate outcome is that it must be structurally
valid, and this includes confirmation of
unidimensionality, meaning that the sum score
reflects one construct only (e.g., ‘pain’).
However, the construct validity of OKS has
never been evaluated using modern test theory
(MTT) models. As OKS contains items related to
pain and physical function, we hypothesized
that it is not unidimensional
Aim: To evaluate the construct validity of the Danish
OKS
Materials and Methods: Data from the SPARK study of 1,452 patients
who had undergone knee replacement due to
OA was obtained. A randomly selected sample
of TKA patients with a suitable size (n=100) was
picked for analyses of unidimensionality, local
dependency and item fit to the model.
Confirmatory factor analysis (CFA) model fit was
evaluated using the chi-squared statistic, and
the close fit indices the root mean square error
of approximation, the comparative fit index, and
the Tucker-Lewis index
Results: OKS failed to fit into a unidimensional model of
one total score. Reporting scale scores as two
domains, “pain" with items 1, 4, 5, 6, 8, 9, 10,
and “function” with items 2, 3, 7, 11, 12,
improved fit indices, indicating better precision
and a reduction of measurement error
compared to the total score. Several items
exhibited misfit to the model, and local
dependence was also evident, but both were
less prominent when scores were reported as
two domains
Interpretation / Conclusion: The Danish OKS possessed inadequate
structural validity in a cohort of patients treated
surgically with TKA. Reporting scale scores as
two separate domains increased measurement
properties and the accuracy of the scale.
Although few items still exhibited problems
fitting the model, we advise that data in previous
studies using OKS are reanalyzed, since an
adequate calculation of scores may alter
previous study conclusions
98. Implementation of discharge on the day of surgery after hip and knee arthroplasty – a prospective multicenter study from the center for fast-track hip and knee replacement
Oddrún Danielsen1,2, Christian Bredgaard1,3, Claus Varnum1,4, Thomas Jakobsen1,5, Mikkel Rathsach1,6, Kim Sperling1,7, Søren Overgaard1,8, Christoffer Calov Jørgensen1,9, Henrik Kehlet1,10, Kirill Gromov1,3, Martin Lindberg-Larsen1,2
1. Center for Fast-track Hip and Knee Replacement, Denmark;
2. Department of Orthopaedic Surgery and traumatology, Odense
University Hospital and Svendborg;
3. Department of Orthopaedic Surgery, Hvidovre University Hospital;
4. Department of Orthopaedic Surgery, Lillebaelt Hospital – Vejle;
5. Department of Orthopaedic Surgery, Aalborg University Hospital;
6. Department of Orthopaedic Surgery, Copenhagen University Hospital,
Herlev-Gentofte;
7. Department of Orthopaedic Surgery, Næstved, Slagelse and Ringsted
Hospitals;
8. Department of Orthopaedic Surgery and Traumatology, Copenhagen
University Hospital, Bispebjerg;
9. Department of Anaesthesia, Hospital of Northern Zeeland, Hillerød;
10. Section of Surgical Pathophysiology, Copenhagen University Hospital,
Rigshospitalet;
Background: Length of hospital stay after hip and knee
arthroplasty is about 1 day in Denmark, but
only very few have been discharged on day
of surgery. Hence, a protocol for multicenter
implementation of discharge on day of
surgery has been performed [1].
[1]. Lindberg-Larsen et al. Study protocol for
discharge on day of surgery after hip and
knee arthroplasty from the Center for Fast-
track Hip and Knee Replacement. Acta
Orthop. 2023 Mar 20;94:121-127.
Aim: To investigate the implementation process
and feasibility of discharge on day of
surgery after primary hip and knee
arthroplasty in a multicenter collaboration.
Materials and Methods: A prospective multcenter study from 7 public
centers across Denmark. Patients were
screened for eligibility using well-defined in-
and exclusion criteria and eligible patients
fulfilling discharge criteria were discharged
on day of surgery. The study period is the
first 6 months (September 2022 to March
2023) after implementation of the study
protocol [1]. Data from the same centers in
a 6 months period before COVID from July
2019 to December 2019 was used for
baseline control.
Results: Of 2821 primary hip and knee
arthroplasties, 36.7% (95% CI 34.9-38.5)
were found eligible (range 21.4%-49.5% in
centers) and 50,1% (range 24,3%-62,7%) of
these were discharged on day of surgery.
Overall, 20.9% (95% CI 19.4-22.4%) of all
patients having primary hip and knee
arthroplasty were discharged on day of
surgery (range 9,2% to 30.9%). This was an
increase compared to 5.6% (95% CI 4.9-
6.3) at baseline (range 0-12.5%). The main
causes of not being discharged on day of
surgery despite being eligible were:
insufficient mobilization, postoperative
nausea and vomiting, late return to ward
and spinal anaesthesia that had not worn
off.
Interpretation / Conclusion: During the first 6 months implementation
period we found it possible to discharge
20,9% on day of surgery compared to 5.6%
at baseline. Hence, discharge on day of
surgery in a multicenter setting is feasible
and may be increased further as major
differences between centers were observed.
However, patient safety should be
monitored and reported.
99. Time trends in incidence and risk factors for revision due to periprosthetic joint infection after knee arthroplasty due to osteoarthritis: A Danish nationwide population-based cohort study, 1997-2019
Marie Anneberg1, Anders Troelsen2, Per Gundtoft3, Henrik Toft Sørensen1,4, Alma Becic Pedersen1,4
1 Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus
University, Denmark;
2 Department of Orthopedic Surgery, Hvidovre Hospital, Denmark;
3 Department of Orthopedic surgery, Aarhus University Hospital, Denmark;
4 Department of Clinical Medicine, Aarhus University Denmark
Background: Periprosthetic joint infection (PJI) is a serious
complication after knee arthroplasty (KA) surgery.
Aim: To examine the time trends in incidence and risk
factors for PJI after KA from 1997 to 2019 in
Denmark.
Materials and Methods: In this population-based cohort study, we used
Danish Knee Arthroplasty Register to include
primary KA due to osteoarthritis (n=115,120).
Outcome was first-time PJI revision, within 0-3
months (early), >3-12 months (delayed), and 0-
12 months after KA. We computed cumulative
incidences and adjusted hazard ratios (aHR) of
PJI with 95% confidence intervals by calendar
periods and by several patient- and surgical-
related predictors.
Results: The overall incidence of PJI within the first
year of primary KA was 0.7 (0.6 - 0.7).
The incidence of PJI within the first year after
primary KA increased from 0.5 (0.3 - 0.7) in
1997-2000 to 0.7 (0.6 - 0.8) in 2017-2019,
driven by an increase from 0.1(0.0 - 0.2) to
0.5 (0.5 - 0.6) in early PJIs. We observed a
decrease in the incidence of delayed PJIs
from 0.4 (0.3 - 0.7) to 0.2 (0.1-0.2) in the
same period.
The aHR for PJI within the first year of
primary KA was 1.6 (1.2 - 2.2) in 2018-2019
vs 2001-2004. The aHR was 5.1 (2.8 - 9.5)
for sustaining an early PJI in 2018-2019 vs
2001-2004, whereas the aHRs for sustaining
a delayed PJI was 0.5 (0.3 - 0.8) in 2018-
2019 vs 2001-2004
Age 75 years and above (vs age 65-74), male
gender, and extreme obesity (vs normal
weight) was associated with higher risk of
PJI. There was an indication that high
comorbidity (vs low) was associated with
higher risk of PJI. The aHRs were 0.6 (0.4-
0.8) early PJI and 0.4 (0.2-0.6) for delayed
PJI when comparing partial knee arthroplasty
(PKA) to total KA.
Interpretation / Conclusion: The overall incidence of PJI after KA is low.
The incidence of early PJI increased whereas
the incidence of delayed PJI decreased from
1997-2019.
PKA was associated with a lower risk of PJI
(compared to TKA). Non-modifiable factors as
gender, age, CCI and the observed time-
effect after surgery, will allow clinicians to
appropriately inform patients preoperatively
and tailor treatment, follow-up regimen, and
improve pre- and postoperative rehabilitation.
100. The influence of trochlea wear on patient reported outcome after medial unicompartmental knee arthroplasty.
Jonathan Winther Olsen 1, Christian Bredgaard Jensen 1, Kristine Ifigenia Bunyoz1, Kirill Gromov1, Anders Troelsen1
1. Clinical Orthopaedic Research Hvidovre, Department of Orthopaedic Surgery,
Copenhagen University Hospital Hvidovre.
Background: In the past patellofemoral osteoarthritis (PFOA)
was considered a contraindication to UKA. Re-
cent studies and contemporary indications state
that PFOA shouldn´t be considered a
contraindication. Despite current knowledge,
there is still a lack of insight into whether patients
with trochlea wear, have a different short-term
development in Patient Reported Outcome
Measures (PROM) scores.
Aim: To examine the association between trochlear
wear and PROM scores after medial UKA.
Materials and Methods: In this cohort study 549 medial UKA (mobile
baring, uncemented Oxford) surgeries were
performed between 2016 and 2020, of which
440 were included in the final dataset based
on complete trochlear wear data. Only severe
lateral facet PFAO with bony deformity was
applied as a contraindication. During surgery,
the patellofemoral joint was graded using the
ICRS cartilage lesion classification system
where the cartilage defects were
subclassified as 0=normal changes (refer-
ence group), 1-2=minor changes, and 3-4=
severe/full cartilage loss. The PROMs
included the Oxford Knee Score (OKS),
Activity and Participation Questionnaire
(APQ), and Forgotten Joint Score (FJS)
which were completed preoperatively and at
3, 12, and 24 months after surgery. PROM
changes were calculated, and linear
regression models were used to calculate
crude and adjusted estimates.
Results: We found no significant differences in PROM
change at any follow-up between the different
groups of trochlear wear regarding the OKS and
the FJS. However, group 1-2 had a significantly
larger change in their APQ score compared to
group 0, at both 3- (crude 7,02 (95% Confidence
Interval (CI) 0,347; 13,7) adjusted 8,60 (95% CI
1,76; 15,4)) and 24-month follow-up (adjusted
11,2 (95% CI 2,02; 20,4) with the latter applying
only for the adjusted analysis.
Interpretation / Conclusion: There were no differences in OKS and FJS
improvement between any of the trochlea wear
groups at any follow-up. The APQ change was
even favorable in group 1-2 vs group 0. Overall,
the results support that trochlea wear should not
be considered a contraindication to perform
medial UKA unless there is severe lateral facet
PFOA with bony deformation.
101. What if I told you that the Minimal Important Change is ZERO at three months after undergoing knee or hip arthroplasty?
Lasse Harris1, Anders Troelsen1, Berend Terluin2,3, Kirill Gromov1, Lina Ingelsrud1
1. Department of Orthopaedic Surgery, Copenhagen University Hospital Hvidovre,
Copenhagen Denmark;
2. Department of General Practice, Amsterdam UMC Location, Vrije Universiteit
Amsterdam, Amsterdam, The Netherlands;
3. Amsterdam Public Health Research Institute, Amsterdam, The Netherlands.
Background: The Minimal Important Change (MIC) reflects what patients, on average, consider the smallest improvement in a score
that is important to them. Numerous methods have been used to calculate MIC values, each with inherent limitations.
However, a new adjusted predictive modeling method accounting for the proportion of improved or deteriorated
patients and the imperfect reliability of the anchor question has been developed.
Aim: We applied the new predictive modeling method to determine Minimal Important Change values for the Oxford
Knee and Hip Score at 3 months follow-up in patients undergoing knee or hip arthroplasty.
Materials and Methods: This cohort study used data from patients undergoing Total Knee Arthroplasty (TKA), Unicompartmental Knee
Arthroplasty (UKA), or Total Hip Arthroplasty (THA) at a public hospital between April 2018 and September 2022. At 3
months postoperatively, patients responded to the Oxford Knee or Hip Score (OKS/OHS) and the MIC anchor
question determining experienced changes in knee or hip pain and functional limitations. We used the anchor-based
improved adjusted predictive modeling method to determine MIC values. Nonparametric bootstrapping was used to
determine 95% confidence intervals (CI).
Results: We obtained complete 3-month postoperative data for 638 of 888 (72%) patients undergoing TKA, 407 of 535 (76%)
undergoing UKA, and 859 of 1197 (72%) undergoing THA. The median age of the patients ranged from 68 to 71
years, and 57% to 60% were females. At 3 months postoperatively, 83% TKA, 86% UKA, and 93% THA patients
reported important improvement, respectively. The OKS MIC values were 0.3 (CI -1.1 to 1.6) and 2.1 (CI 0.0 to 3.9)
for TKA and UKA, respectively, and the OHS MIC value was 0.8 (CI -1.3 to 2.7) at 3 months postoperatively.
Interpretation / Conclusion: Three months after undergoing knee or hip arthroplasty, not experiencing any deterioration in
pain and functional limitations is considered an important improvement. In addition to improving
our understanding of patients’ views on early postoperative outcomes, these clinical thresholds
may aid in evaluating registry-based treatment quality.
102. Minimal Important Change for the 9-step Stair Climb Test in patients with knee osteoarthritis
Julie B. Pajaniaye1,2, Eric Cheret1, Cecilie H. Langvad1, Pætur M. Holm3,4, Søren T. Skou3,4, Josefine B. Larsen1,5, Inger Mechlenburg1,5,6
1. Department of Orthopaedics, Aarhus University Hospital;
2. Department of Dentistry and Oral Health, Aarhus University;
3. The Research Unit PROgrez, Department of Physiotherapy and Occupational Therapy, Næstved-Slagelse-Ringsted Hospitals;
4. Research Unit for Musculoskeletal Function and Physiotherapy, Department of Sports Science and Clinical Biomechanics, University of Southern Denmark;
5. Department of Clinical Medicine, Aarhus University;
6. Department of Public Health, Aarhus University.
Background: Stair climb tests (SCT) evaluate stair negotiation and are part of the core recommendations for evaluating treatment effects on performance-based function in individuals with knee osteoarthritis (KOA). While no specific SCT is recommended, the 9-step SCT is commonly used. Minimal Important Change (MIC) is described as a measure of interpretability and is being defined as the minimum within-person change between repeated measurements that a patient would both perceive as a change and ascribe as important. The MIC of the 9-step SCT for patients with KOA has not yet been established.
Aim: The aim of this prospective cohort study was to estimate the MIC for the 9-step SCT for patients with KOA. Secondly, to assess the proportion of patients obtaining MIC, i.e. being responders to a 12-week exercise program, and to assess whether being a responder was associated with experiencing an important change.
Materials and Methods: Data from a randomized controlled trial conducted from July 2017 to October 2018 at Næstved Hospital was used. Patients with KOA underwent a 12-week exercise intervention consisting of neuromuscular exercises with/without strength training. SCT data was collected at baseline and at 12-week follow-up. Patients’ self-reported experience of change of their knee problem was measured using the 7-point anchor question Global Perceived Effect Score (GPE) at follow-up. Perceived change was scored from “Better, an important improvement” to “Worse, an important worsening”. The MIC estimate for the SCT was calculated using logistic regression with predictive modeling.
Results: 72 participants (54% women; mean age 65.5 years) had complete data. MIC value (95% CI) for improvement was 2.3 (–1.2; 7.3) seconds for the 9-step SCT. 29 of 72 participants (40%) in the trial were responders and there was a statistically significant association between being a responder and experiencing an important change (GPE scores 6 and 7).
Interpretation / Conclusion: The MIC value of 2.3 seconds for the 9-step SCT for patients with KOA corresponds to minimal improvements that the average patient finds important. The estimated MIC value should be confirmed in larger cohorts to establish a narrower confidence interval.
103. Bone Remodeling Of The Distal Femur And Proximal Tibia After Cementless Total Knee Arthroplasty - A 7 Years Prospective Clinical DEXA Study
Mikkel Rathsach Andersen1, Nikolaj Sebastian Winther2, Thomas Lind1, Henrik Morville Schrøder2, Michael Mørk Pedersen2
1. Department of Orthopeadics, Gentofte Herlev Hospital
2. Department of Orthopeadics, Rigsjospitalet
Background: Loss of bone stock as a response to the bone
trauma and immobilization related to joint
replacement can increase the risk of periprosthetic
fracture and aseptic loosening. There are few
previous studies with longterm follow-up of of tibia
and femur bone loss after cementless total knee
arthroplasty (TKA).
Aim: The aim of this study was to investigate the short-
term and long-term adaptive bone remodelling of the
distal femur and the proximal tibia after cementless
TKA.
Materials and Methods: 65 patients (mean age 61 years) were included and
bone mineral density (BMD) mesassurements distal
femur using dual energy x-ray (DEXA) were
performed postoperatively and after 3, 6, 12, 24 and
84 months. We completed seven year follow up of
36 patients.
Bone mineral density (g/cm2) was measured in
three regions of interest in the periprosthetic bone of
the distal femur and the proximal tibia. Also the BMD
of distal tibia just above the ankles were meassured
bilaterally as control.
Results: In the distal femur significant changes in bone
mineral density were seen after 84 months of follow-
up and bone mineral density decreased by 28.7% in
the anterior region behind the anterior flange of the
prosthesis, 16.2% in the posterior region and 10.3%
in the proxiaml region. Most of the bone loss in the
femur occured within the first 24 months.
In the proximal medial region of the tibia bone
mineral density decreased by 8.9% and in the
proximal lateral tibia by 10.4%. During the first six
months we found a temporary BMD increase in
lateral proximal tibia. All the above BMD changes
were statistically highly significant (P<0.001).
Interpretation / Conclusion: We found highly significant bone mineral change
in the distal femur and proximal tibia after
cementless total knee arthroplasty. Most of the
BMD loss took place within the first 24 months.
In the anterior femur region a decrease in bone
mineral density of 28.7% during the seven year
period.
In the tibia we found less BMD loss and a
temporary increase in lateral BMD which could
be explained by correction of varus alignment.
Taking the expected age related decay in this
age group in to consideration the decrease was
substantial and must be considered to
predispose to periprosthetic fractures.