![Fig. 3 Measurement of femoral and tibial TKA component positions (varus-valgus, flexion-extension, internal rotation-external rotation) in 3-D reconstructed CT images using a customized software [3]](/figures/fig-3-measurement-of-femoral-and-tibial-tka-component-193hyejc.webp)
ORIGINAL ARTICLE
Clinical value of SPECT/CT in the painful total knee arthroplasty
(TKA): a prospective study in a consecutive series of 100 TKA
Michael T. Hirschmann
1
& Felix Amsler
2
& Helmut Rasch
3
Received: 25 February 2015 /Accepted: 21 May 2015 / Published online: 6 June 2015
#
Springer-Verlag Berlin Heidelberg 2015
Abstract
Purpose Bone single photon emission computed tomography
(SPECT)/CT is considered as beneficial in unhappy patients
with pain, stiffness or swelling after total knee arthroplasty
(TKA). The purpose of this study was to identify typical pat-
terns of bone tracer uptake (BTU), distribution and intensity
values in patients after TKA. The above findings were corre-
lated with the type and fixation of TKA, the time from TKA
and intraoperative findings at revision surgery.
Methods A total of 100 knees of 84 consecutive patients
(mean age±SD 70±11 years) after TKA with persistent knee
pain were prospectively included. All patients underwent
clinical examination, standardized radiographs and
99m
Tc-
hydroxymethane diphosphonate (HDP) SPECT/CT as part of
a routine diagnostic algorithm. The diagnosis before and after
SPECT/CT and final treatment were recorded. TKA compo-
nent position was determined on 3-D reconstructed images.
Intensity and anatomical distribution of BTU was determined.
Maximum intensity values were recorded as well as ratios in
relation to the proximal midshaft of the femur. Uni variate
analyses (chi-square test, Pearson’s correlation and t test for
independent samples) were performed (p<0.05).
Results SPECT/CT changed the clinical diagnosis and final
treatment in 85/100 (85 %) knees. Intraoperative findings
confirmed the preoperative SPECT/CT diagnosis in 32/33
knees (97 %). TKA loosening as well as progression of
patellofemoral osteoarthritis (OA) was correctly diagnosed
in 100 % of knees. Typical patterns of BTU for specific pa-
thologies were identified. Loose femoral TKA components
significantly correlated with increased BTU at the lateral fem-
oral regions (p<0.05). Loose tibial TKA components signifi-
cantly correlated w ith increased BTU at all tibial regions
(p<0.05) and around the tibial peg (p>0.01).
Conclusion The diagnostic benefits of SPECT/CT in patients
after TKA have been proven. Typical pathology-related BTU
patterns were identified, which will improve reporting quality.
Due to the benefits in establishing the correct diagnosis,
SPECT/CT should be part of the routine diagnostic algorithm
for patients with pain after TKA.
Keywords Knee
.
SPECT/CT
.
SPECT
.
CT
.
Total knee
arthroplasty
.
Replacement
.
Component position
.
Tracer
uptake
.
Bone
Introduction
When carefully reviewing the orthopaedic and rheumatologi-
cal literature, 20–30 % of patients after primary total knee
arthroplasty (TKA) are not satisfied. A considerable number
also report persistent or recurrent pain [1–5].
As the most common causes infection, aseptic loosening,
instability, malposition of the TKA, arthrofibrosis and
patellofemoral problems have been reported [2]. However,
in many cases after TKA the cause for the patient’sproblems
cannot be identified unambiguously [3–5]. The current routine
diagnostics including conventional radiographs, CT, MRI,
scintigraphy, single photon emission computed tomography
(SPECT) or positron emission tomography (PET)/CT fail to
* Michael T. Hirschmann
Michael.Hirschmann@unibas.ch
1
Department of Orthopaedic Surgery and Traumatology,
Kantonsspital Baselland (Bruderholz, Liestal, Laufen),
4101 Bruderholz, Switzerland
2
Amsler Consulting, Basel, Switzerland
3
Institute of Radiology and Nuclear Medicine, Kantonsspital
Baselland, 4101 Bruderholz, Switzerland
Eur J Nucl Med Mol Imaging (2015) 42:1869–1882
DOI 10.1007/s00259-015-3095-5
accurately establish the correct diagnosis [2–5]. This is in part
due to the fact that in many of the cases a combination of
different causes is responsible for these problems.
Recently, Hirschmann et al. highlighted the clinical value
of a standardized diagnostic algorithm including SPECT/CT
in patients with problems after TKA [3]. They reported near
perfect inter- and intra-observer reliability for their proposed
standardized SPECT/CT algorithm including a localization
scheme, intensity value and 3-D prosthetic component analysis
[3, 6]. W ith this specific algorithm the authors aim to identify
typical distribution patterns and intensity thresholds of bone
tracer uptake, which reflect pathologies such as mechanical
loosening, instability, component malposition or patellofemoral
problems [3]. Hence, they piloted the method in a consecutive
series of 23 patients after TKA. It was observed that there is a
distinct relationship of the position of the prosthetic compo-
nents, the postoperative alignment and the pattern and intensity
of bone tracer uptake in SPECT/CT [2]. They further reported
that SPECT/CT significantly changed the diagnosis and subse-
quent treatment [2, 5].
By a combination of 3-D analysis of component position,
mechanical and anatomical axes as well as the pattern of dis-
tribution and intensity of bone tracer uptake SPECT/CT offers
a richer source of diagnostic data to the radiology, the nuclear
medicine and finally the orthopaedic fraternity [2, 3, 5–9].
Hence, SPECT/CT is considered as one important diagnostic
part of their routine algorithm in patients with pain, stiffness,
swelling or instability after TKA.
A more profound insight into the relationship of TKA
component design and position, alignment and physiologi-
cal remodelling within the bone-prosthesis interface could
help to establish new diagnostic algorithms and a signifi-
cant improvement of specificity and sensitivity of SPECT/
CT in patients after TKA [2, 3, 5–9].
The purpose of this study was to investigate in how many
patients SPECT/CT changed the diagnosis and subsequent
treatment as well the sensitivity and specificity for loosening,
infection, patellofemoral osteoarthritis (OA) and malposition
of TKA. The secondary purpose was to identify typical pat-
terns of bone tracer uptake distribution and intensity values in
unhappy patients after TKA. The above findings were corre-
lated with the type of TKA, the time from primary TKA sur-
gery, type of TKA, cemented or non-cemented, and intraop-
erative findings at revision surgery (loose versus well-fixed
TKA components).
Materials and methods
A total of 100 knees (male to female ratio=34:66, mean age±
standard deviation 70±11 years) of 84 consecutive patients
(male to female ratio=29:55) with persistent pain after primary
TKAwere prospectively included. Patients who had undergone
a previous TKA revision surgery were excluded. All patients
underwent clinical and radiological examination including
standardized radiographs (anteroposterior and lateral weight-
bearing, patellar skyline view) and
99m
Tc-hydroxymethane
diphosphonate (HDP) SPECT/CT as part of a routine diagnos-
tic algorithm (Fig. 1). Infection was ruled out clinically, by
aspiration and biopsy before revision surgery. In addition, bi-
opsies were taken intraoperatively. All infected cases were not
included in this study.
Ethical approval was obtained from the local Ethics Com-
mittee. All procedures performed were in accordance with the
ethical standards of the institutional and/or national research
committee and with the 1964 Declaration of Helsinki and its
later amendments or comparable ethical standards. Informed
consent was obtained from all individual participants included
in the study.
The median time from primary TKA to the date of SPECT/
CT imaging was 36 months (range 6–240 months). The pa-
tients’ demographics such as age, gender, time from primary
TKA, type and model of primary TKA were noted. For 53
(53 %) knees a fixed and for 47 (47 %) a mobile-bearing
polyethylene inlay was present. A cemented TKA was found
in 12 (12 %) femoral and 97 (97 %) tibial components.
The diagnosis before and after SPECT/CT imaging as well
as the final treatment (surgical versus non-surgical) were re-
corded. Radiolucent lines and osteolysis were taken into con-
sideration as criteria for loosening. For the intraoperative di-
agnosis of loosening very strict criteria were used. Only if the
TKA was already toggling after standard approach including
thorough synovial debridement and removal of all
osteophytes it was considered to be loose.
The final diagnosis was based on microbiology, histology,
clinical and radiological as well as intraoperative findings.
Data were analysed to determine whether SPECT/CT had
changed the diagnosis and/or subsequent treatment.
99m
Tc-HDP SPECT/CT was performed using a hybrid sys-
tem (Symbia T16, Siemens, Erlangen, Germany) which con-
sists of a pair of low-energy, high-resolution collimators and a
dual-head gamm a camera and an integrated 16×0.75-mm-
slice thickness CT. All patients received a commercial 500–
700 MBq
99m
Tc-HDP inj ection (Mallinckr odt, Wollerau,
Switzerland). Two-plane scintigraphic images were taken in
the perfusion phase (immediately after injection), the soft tis-
sue phase (1–5 min after injection) and the delayed metabolic
phase (2 h after injection). SPECT/CT was performed with a
matrix size of 128×128, an angle step of 32 and a time per
frame of 25 s 2 h after injection.
SPECT/CT images were analysed on 3-D reconstructed
images for analysis of femoral and tibial TKA component
position as well for measurements of bone tracer uptake
(intensity and anatomic al distribut ion pattern). The rotational
(internal-external rotation), sagittal (flexion-extension, anterior-
posterior slope) and coronal (varus-valgus) positions of the
1870 Eur J Nucl Med Mol Imaging (2015) 42:1869–1882
tibial and femoral TKA components were assessed using a
customized analysis software (OrthoExpert©, London, UK;
Fig. 2). The measurement method has been previously val-
idated and showed near perfect inter- and intra-observer
reliability [3](Fig.3).
The anatomical areas represented by a previously validated
localization scheme were volumetrically measured for bone
tracer uptake intensity in 3-D. Maximum intensity values were
recorded as well as ratios between the respective value in the
measured area and the background tracer activities (proximal
midshaft of the femur) were calculated. The inter- and intra-
observer reliability (intraclass correlation coefficient, ICCs)
for every area investigated was >0.85, which is considered
to be a near perfect reliability [3].
Statistical analysis
All data were analysed by an independent professional statis-
tician using SPSS version 17.0 (SPSS, Chicago, IL, USA).
Continuous variables were described using means and
standard devia tions or medians and ranges. Categorical
variables were tabulated with absolute and relative fre-
quencies. Univariate analysis (chi-square test, Pearson’s
correlation and t test for independent samples) was per-
formed to identify any correlations between component
position, tracer uptake and diagnosis. For all analysis,
p<0.05 was considered statistically significant.
Results
SPECT/CT changed the clinical diagnosis and final treatment
in 85/100 (85 %) knees. A total of 33 knees (33 %) were
surgically revised (male to female ratio=10:23), 58 knees
(58 %) non-surgically treated and 9 knees (9 %) were sched-
uled for revision surgery.
The mean time from primary TKA for the knees being
revised was 4.8±3.8 years. In 27 knees (82 %) the femoral
TKA component and in 32 (97 %) the tibial TKA component
was cemented; 17 knees (51.5 %) had a fixed and 16 (48.5 %)
a mobile-bearing polyethylene inlay. In 14/33 knees the fem-
oral TKA component and in 12/33 knees the tibial TKA com-
ponent was revised. In 20 knees a secondary patellar
resurfacing was performed.
The intraoperative findings confirmed the preoperative
SPECT/CT diagnosis in 32/33 knees (97 %). In one case in
SPECT/CT no loosening was identified. However, intraoper-
atively loosening was found (Figs. 4 and 5). The bone inter-
face was separated from the cement and TKA component by a
periprosthetic membrane. Femoral (n=7) and tibial loosening
(n=6) of the TKA was correctly diagnosed with SPECT/CT in
100 % of knees. Progression of patellofemoral OA was cor-
rectly diagnosed in 19 knees (100 %).
Tibial and femoral TKA component position [varus-val-
gus, flexion-extension, internal rotation (IR)-external rotation
(ER)] measured on 3-D CT are presented for all patients and
Fig. 1 Diagnostic algorithm for unhappy patients after TKA
Eur J Nucl Med Mol Imaging (2015) 42:1869–1882 1871
then compared between revised and non-revised patients in
Table 1.
Therelationshipofbonetraceruptakeineachanatomical
region and TKA component position is presented for the en-
tire study group and revised TKA in Tables 2 and 3. Table 4
shows that patients with a malpositioned TKA can be identi-
fied by increased bone tracer uptake in all patellar regions.
Loose femoral TKA components significantly correlated
with increased bone tracer uptake only at the lateral femoral
regions (Flat sa 0.5, Flat sp 0.57, Flat ia 0.42, Flatip 0.4;
p<0.05). Loose tibial TKA components significantly correlat-
ed with increased bone tracer uptake at a ll tibial regions
(Tmed a 0.33, Tmed p 0.37, Tlat a 0.43, Tlat p 0.46;
p<0.05). In addition, there was a highly significant correlation
for the regions around the tibial stem (0.49; p>0.01). Table 5
presents diagnosis, treatment and SPECT/CT findings in all
revised knees (Fig. 6). Table 6 shows typical SPECT/CT find-
ings in relation to the pathology diagnosed.
Discussion
The most important findings of the study were:
Firstly, including SPECT/CT in a diagnostic algorithm for
unhappy patients after TKA led to an improved diagnosis and
treatment in 85 % of patients. SPECT/CT diagnosis was
confirmed in 97 % intraoperatively. Loosening of tibial or
femoral TKA components as well as progression of
patellofemoral OA was diagnosed correctly in all patients.
These findings are in agreement with a previous study by
our group. In this pilot study on 23 knees of patients with
problems after TKA it was shown that SPECT/CT imaging
changed the suspected diagnosis and the proposed treatment
in 83 % of knees [2]. Progression of patellofemoral OA, loos-
ening of the tibial and loosening of the femoral TKA compo-
nent were the leading causes of pain after TKA [2].
Due to the benefits in establishing the correct diagnosis,
when performed and analysed as described here, SPECT/CT
should be part of the routine diagnostic algorithm for patients
with pain after TKA [5]. As bone scans or SPECT it has been
shown useful for diagnosis of loosening after TKA, but was
limited due to its poor specificity [10, 11]. However, only
qualitative analysis of bone scans and SPECT was performed.
Several years ago Klett et al. highlighted the clinical value
of quantitative bone scintigraphy for the diagnosis of aseptic
loosening in TKA [12]. They retrospectively investigated 31
tibial components of cemented total knee prostheses using
quantitative bone scintigraphy and found a sensitivity of 0.9,
a specificity of 1, a negative predictive value of 0.85, a posi-
tive predictive value of 1 and an accuracy of 0.94, respectively
[12]. The authors concluded that quantitative bone scintigra-
phy appears to be a reliable diagnostic tool for aseptic
Fig. 2 The previously validated scheme for anatomical localization of bone tracer uptake (reprinted with permission)
1872 Eur J Nucl Med Mol Imaging (2015) 42:1869–1882
loosening [12]. However, Sacchetti et al. reported a low repro-
ducibility for the quantitative measurements using region of
interest (ROI) analysis [13].
Many authors used bone densitometry for assessment of
bone density around TKA [14–17]. In contrast to bone densi-
tometry, in which only the density of bone is detected,
SPECT/CT offers a window into the pro cess of bone
remodelling. In addition, it has a better ability to localize areas
of increased or decreased bone tracer uptake. Localization of
bone density around TKA is rather inaccurate and broad. The
bone tracer is directed towards bone-forming minerals, which
areproducedbyactiveosteoblasts[18].
In theory the process of aseptic loosening leads to
micromotion of the TKA components. Aiming for stabilization
Fig. 3 Measurement of femoral and tibial TKA component positions (varus-valgus, flexion-extension, internal rotation-external rotation) in 3-D
reconstructed CT images using a customized software [3]
Fig. 4 Patient with loosening of
tibial TKA component, which is
identified by the increased bone
tracer uptake around the tibial peg
and the tibial plateau
Eur J Nucl Med Mol Imaging (2015) 42:1869–1882 1873