Painful Hip Prosthesis Research Articles

Diagnostic Performance of Dual-Energy CT for Detecting Painful Hip Prosthesis Loosening.

Background Revisions of hip prostheses are increasing, and conventional radiography (CR) is a primary tool for managing -complications. However, dual-energy CT (DECT) with virtual monoenergetic imaging is capable of reducing periprosthetic metal artifacts compared with standard CT. Purpose To compare the diagnostic performance of DECT and CR in detecting hip prosthesis loosening, using surgery as a reference for diagnosis. Materials and Methods This retrospective single-center study conducted between January 2018 and October 2020 included -consecutive patients with unilateral painful hip prostheses. Two independent readers (with 15 years and 4 years of experience) who were blinded to clinical findings evaluated CR and DECT images. At imaging, diagnosis of loosening prosthesis was made for -periprosthetic radiolucency greater than or equal to 2 mm wide or the presence of two or more secondary findings, including -periprosthetic osteolysis, angulation of the implant, fracture, or abnormal periosteal reaction. For each reader and for each imaging parameter, -sensitivity and specificity were calculated. The diagnostic performance of each imaging tool was compared by using the McNemar test. Interobserver agreements were calculated with Cohen κ statistics. Statistical software was used. Results Overall, 178 patients (mean age ± standard deviation, 74 years ± 20; 96 men) were included (121 undergoing surgery, 57 follow-up). Overall, 87 of 178 patients (49%) were diagnosed with a loosened prosthesis. DECT had higher sensitivity and specificity than CR for both reader 1 (94% [82 of 87 examinations; 95% CI: 87, 98] and 93% [85 of 91 examinations; 95% CI: 86, 97] vs 84% [73 of 87 examinations; 95% CI: 74, 91] and 91% [83 of 91 examinations; 95% CI: 83, 96], respectively; P < .001) and reader 2 (92% [80 of 87 examinations; 95% CI: 84, 97] and 95% [86 of 91 examinations; 95% CI: 88, 98] vs 80% [70 of 87 -examinations; 95% CI: 71, 88] and 91% [83 of 91 examinations; 95% CI: 83, 96], respectively; P = .001), with better interobserver agreement (κ, 0.88 [95% CI: 0.81, 0.95] vs 0.78 [95% CI: 0.69, 0.88]). Conclusion Dual-energy CT showed better diagnostic performance than conventional radiography in diagnosing hip prosthesis loosening. See also the editorial by Lutz in this issue. © RSNA, 2021.

Comparison of radiographs, tomosynthesis and CT with metal artifact reduction for the detection of hip prosthetic loosening.

To evaluate the diagnostic performance of digital tomosynthesis (DTS) for the diagnosis of hip prosthesis loosening (PL) compared with conventional radiographs and CT with metal artifact reduction (CT-MAR). Forty-nine patients with painful hip prosthesis were prospectively included and underwent anteroposterior and lateral radiographs, anteroposterior DTS and CT-MAR of the hip. This study was approved by the local ethics committee, and all patients signed an informed consent form. Images were evaluated independently by two radiologists. Periprosthetic radiolucent lines wider than 2 mm found in two or more Gruen or De Lee and Charnley zones were considered diagnostic of PL. All cases of PL were confirmed surgically. Patients with a stable radiological follow-up for at least 1 year with an alternative cause for the symptoms or with no surgical evidence of PL were considered PL negative. There were 21 cases of PL, 9 unilateral and 12 bilateral. For both the acetabular and femoral sides, DTS had a specificity for PL detection similar to that of conventional radiographs and CT-MAR (98.5-100%, 96.9%-100% and 96.9-95.4% respectively for both readers) and a sensitivity similar to conventional radiographs (39.9-45.4% versus 33.3-51.5% for both readers) but lower than CT-MAR (84.85% for both readers). The interobserver agreement was 0.84 for CT-MAR, 0.53 for DTS and 0.39 for conventional radiographs. DTS has a similar diagnostic performance to radiographs for the diagnosis of PL with a better interobserver agreement. The sensitivity however remains lower than that of CT-MAR. • Plain radiograph is still the first imaging step when hip prosthesis loosening is suspected. • Interobserver agreement is better with digital tomosynthesis than radiographs. • Sensitivity of CT with state-of-the-art metal artifact reduction is superior to that of digital tomosynthesis.

Fluorodeoxyglucose positron emission tomography imaging for diagnosing periprosthetic hip infection: the importance of diagnostic criteria.

Fluorodeoxyglucose positron emission tomography (FDG-PET) is a novel method of assessing suspected periprosthetic hip infection. However, a heterogeneity of sensitivity and specificity using different diagnostic criteria across clinical studies has been published. The objective of this study is to evaluate the various diagnostic criteria using FDG-PET in diagnosing periprosthetic hip infection. FDG-PET scans of patients suffering from painful hip prostheses between 2008 and 2015 were retrospectively reviewed. The PET images were considered positive for infection using five criteria: any increased uptake at the (1) bone-prosthesis-interface, (2) periprosthetic soft tissue (PST), or (3) both, (4) increased uptake in the bone-prosthesis-interface compared to the PST, and (5) increased uptake along the femoral bone-prosthesis-interface. The final diagnosis of infection was based on the pre-operative and intra-operative findings with clinical follow-up > 12months. A total of 33 hip prostheses were evaluated in this study, of which 16 were determined to be infected and 17 uninfected. Any periprosthetic FDG uptake was found in all symptomatic prostheses (sensitivity 100%; specificity 0%). When increased uptake in the bone-prosthesis-interface (sensitivity 100%; specificity 65%) or PST (sensitivity 94%; specificity 59%) was considered infected, specificity increased. A higher intensity of uptake at the bone-prosthesis-interface than PST demonstrated only moderate specificity (sensitivity 44%; specificity 71%). The most specific criterion for infection was an increased FDG uptake along the femoral bone-prosthesis-interface (sensitivity 81%; specificity 94%). Our results demonstrated that the accuracy of FDG-PET is highly dependent of the diagnostic criteria used for periprosthetic hip infection. Only an acceptable diagnostic accuracy (sensitivity 81%; specificity 94%) was found when increased FDG uptake along the femoral bone-prosthesis-interface was considered positive for infection.

Clinical utility of 99mTc-ubiquicidin (29–41) as an adjunct to bone scan in differentiating infected versus noninfected loosening of prosthesis before revision surgery

The aim of this study was to evaluate the utility of Tc-ubiquicidin (Tc-UBI) (29-41) as an adjunct to an methylene diphosphonate (MDP) bone scan in differentiating septic versus aseptic loosening in patients with painful prosthesis posted for revision surgery. A two-vial cold kit of UBI (29-41) was prepared and utilized for the preparation of patient dose of Tc-UBI (29-41). Twenty two patients with painful hip or knee prosthesis and scheduled for revision surgery were included in the study. Overall, 370-555 MBq of Tc-UBI (29-41) was injected intravenously in all the patients. A blood pool image at 20 min after injection was followed by spot views of the suspected region of infection (target) and a corresponding normal area (nontarget) at 60 min. All patients underwent a routine Tc-MDP three-phase whole-body bone scan, followed by single-photon emission computed tomography/computed tomography of the prosthesis within a week of the Tc-UBI (29-41) study. For Tc-UBI scans, a visual score (0-3) was used to categorize studies as positive or negative, with scores of 0 (minimal or no uptake; less than soft tissue or contralateral extremity) and 1 (mild; equivalent to soft tissue or contralateral extremity) being considered negative and scores of 2 (moderate; uptake greater than soft tissue or contralateral extremity, but less than the liver) or 3 (intense; uptake greater than soft tissue or contralateral extremity and equivalent to the liver) being considered positive. The final correlation was on the basis of bacterial culture as the major criterion and the results of clinical tests, radiography, fluorine-18-fluorodeoxyglucose PET-CT, and three-phase bone scanning as the minor criteria. In all, 22 studies were carried out with Tc-UBI (29-41). Of these, 16 scans were considered positive and six were negative for infection foci. All negative scans were subsequently confirmed to be true negative. Adverse reactions were not observed during image acquisition and within 5 days after the study. The overall sensitivity, specificity, and positive and negative predictive values were 100, 85.7, 93.75, and 100%, respectively. A combination of an MDP bone scan and UBI scans was considered to yield maximum confidence toward reporting for the presence of infection. Patient dose of Tc-UBI (29-41) was prepared successfully and a simple quality control method to check radiolabeling yield was used at the hospital radiopharmacy. Tc-UBI (29-41) showed promise in localizing foci of infection, with optimal visualization at 20-60 min, for the evaluation of prosthesis loosening.

Designing a New Molecular Probe: The Potential Role for Tilmanocept (Lymphoseek®) in the Assessment of Patients with Painful Hip and Knee Joint Prostheses.

Background:There is a long history of nuclear medicine developments in orthopaedics beginning in the early 20th century. Technetium-99m (99mTc) has a short half-life of six hours, emits 140 keV gamma rays and is the most widely used isotope, imaged with the Anger (gamma) camera. Gamma image quality and test sensitivity in painful prosthetic joints can be improved with single photon emission computed tomography (SPECT) and SPECT/CT. Positron Emission Tomography-Computed Tomography (PET-CT) with Sodium Fluoride (18F-NaF) and 18Fluorine-fluorodeoxyglucose (18F-FDG) PET have promising and limited roles respectively in the investigation of painful prosthetic joints. New SPECT/CT and PET-CT isotopes targeting activated macrophages with 99mTc Tilmanocept (Lymphoseek®) and 68Gallium labelled Tilmanocept respectively show potential as agents to demonstrate wear particles ingested by macrophages and multinucleated giant cells. An imaging algorithm using SPECT and/or PET agents is proffered as a cost effective way of speedily and accurately arriving a diagnosis.Methods: Review of the historical role of nuclear medicine in orthopaedics and research into the potential role of new radiopharmaceutical agents was undertaken. Guidelines and algorithms for the imaging of complicated joint prosthesis are provided.Results:There is an established role for nuclear medicine in orthopaedics and particularly in the investigation of complicated joint prostheses. Imaging with Tilmanocept provides new opportunities to shorten the time to diagnose loosened and infected joint prostheses.Conclusion:There is a potential new role for Tilmanocept, which can be utilised with both PET-CT and SPECT-CT technologies. Tilmanocept is a relatively new radiopharmaceutical which has a potential role in the imaging assessment of painful joint prosthesis.

Bone scan usefulness in patients with painful hip or knee prosthesis: 10 situations that can cause pain, other than loosening and infection.

In recent years, with the higher median life expectancy, the number of hip and knee replacements has increased. Clinical examination and morphological studies are essential to evaluate patients with a painful arthroplasty. Nuclear medicine examinations also play an important role, their main usefulness being the exclusion of prosthesis complications. Nevertheless, conventional examinations, namely bone scan and white blood cell scintigraphy, can also identify complications, such as loosening and infection. This study describes the normal and pathologic patterns of a bone scan and exemplifies ten common situations that can cause pain in patients with hip or knee arthroplasty, other than loosening and infection, which can be disclosed on a bone scintigraphy. The ten situations that should be considered and looked for when analysing a bone scan are: referred pain, patellofemoral pain syndrome, fractures, fissures, abscess/haematoma, bone insert behaviour, heterotopic ossification, greater trochanter pseudarthrosis, osteoarthritis extension in a knee with an unicompartmental prosthesis, and systemic disease with bone involvement.

Potential clinical implication of (18) F-FDG PET/CT in diagnosis of periprosthetic infection and its comparison with (18) F-Fluoride PET/CT.

The differentiation between septic and aseptic loosening of prosthetic hip joint is a major challenge for the clinician. This study assessed and compared the diagnostic accuracy of (18) F- flouro-deoxyglucose positron emission tomography/computed tomography ((18) F-FDG PET/CT) with (18) F-fluoride PET/CT for diagnosis of infection in the painful hip prosthesis. In this prospective study, we included the patients with painful hip prostheses with radiological or clinical suspicion of loosening, those who had given the written consent and scheduled for clinical and diagnostic evaluation before revision arthroplasty. To rule out the nature of loosening (septic vs. aseptic), all the patients underwent (18) F-Fluoride PET/CT and (18) F-FDG PET/CT. The reference standard for periprosthetic infection was based on histopathology and/or microbial culture and/or intraoperative findings. We prospectively evaluated 42 patients of hip prostheses before revision arthroplasty. Visual and semi-quantitative analysis of both the positron emission tomography (PET) images was done and the results were compared with a reference standard. The sensitivity, specificity, positive predictive value (PPV), negative predictive values (NPV) and accuracy of (18) F-FDG PET/CT were 93.7%, 92.3%, 88.2%, 96% and 92.8% respectively. The sensitivity, specificity, PPV, NPV and accuracy of (18) F-fluoride PET/CT were 75%, 96.1%, 92.3%, 86% and 88.1% respectively. FDG PET/CT has higher sensitivity, NPV and accuracy as compared to compared to Fluoride PET/CT and comparable specificity and PPV. Fluoride PET/CT had shown slightly higher specificity than FDG-PET/CT, but the overall diagnostic performance of FDG-PET/CT in periprosthetic infection is optimal in routine clinical practice and better than fluoride PET/CT.

Comparative analysis of dual-phase 18F-fluoride PET/CT and three phase bone scintigraphy in the evaluation of septic (or painful) hip prostheses: A prospective study.

The preoperative differentiation of aseptic and septic loosening of hip prostheses remains a diagnostic challenge for clinicians and many molecular imaging techniques have been evaluated. The objective of current study was to establish the clinical utility of dual phase 18F-fluoride PET/CT (DPFP) in diagnosing implant loosening, differentiation between septic and aseptic loosening and to compare the diagnostic accuracy of DPFP and three-phase bone scan (TPBS). In this prospective study, we evaluated 57 hip components in 45 patients (bilateral prostheses in 12 patients, 45 painful and 12 asymptomatic contralateral hip components) with dual phase fluoride PET/CT and TPBS. Findings of skeletal scintigraphy and PET/CT were evaluated by two expert nuclear medicine physicians, blinded with clinical findings and final diagnosis. The patterns of tracer uptake and maximum standardized uptake value (SUVmax) were noted for each joint. The final diagnosis was based on intraoperative findings, histopathological or microbiological examinations. Out of twelve non-painful hips, DPFP correctly identified no loosening in 11 hips while TPBS detected in 10 hips. In the remaining 45 hips with radiological proven loosening to rule out sepsis, DPFP had a sensitivity, specificity, PPV, NPV and accuracy of 75%, 97%, 92%, 88% and 88% respectively while TPBS revealed 81%, 86%, 76%, 89% and 82% respectively. DPFP had shown a higher specificity and PPV as compared to the TPBS in the evaluation of painful hip prostheses. The pattern of tracer uptake may help in the differentiation between the two entities. We also noted a significant difference between SUVmax values of septic and aseptic loosening. The results suggested that DPFP has considerable potential in differentiating septic from aseptic loosening of hip prostheses and more specific to rule out sepsis than TPBS. It may be employed before revision arthroplasty to evaluate implant for loosening and sepsis in loosened implant.

CT and MRI of hip arthroplasty

Metal-induced artifacts impair image quality of computed tomography (CT) and magnetic resonance imaging (MRI) in patients with hip prostheses. Due to new developments in metal artifact reduction both methods can now be used for evaluation of a painful hip prosthesis. Iterative reconstruction algorithms and dual-energy scans are among the newer CT techniques for artifact reduction, while slice-encoding for metal artifact correction (SEMAC) and multi-acquisition variable-resonance image combination (MAVRIC) have introduced substantial improvements for MRI. Loosening of the hip prosthesis, osteolysis from small wear particles and pseudotumors in metal-on-metal prostheses are specific pathologies in patients with total hip arthroplasty. Other causes of painful hip prostheses are infections, fractures, tendinopathies, tendon ruptures, muscle and nerve alterations and heterotopic ossifications.

Pseudotumors in Association with Well-Functioning Metal-on-Metal Hip Prostheses

Many papers have been published recently on the subject of pseudotumors surrounding metal-on-metal hip resurfacing and replacement prostheses. These pseudotumors are sterile, inflammatory lesions within the periprosthetic tissues and have been variously termed masses, cysts, bursae, collections, or aseptic lymphocyte-dominated vasculitis-associated lesions (ALVAL). The prevalence of pseudotumors in patients with a well-functioning metal-on-metal hip prosthesis is not well known. The purpose of this study was to quantify the prevalence of pseudotumors adjacent to well-functioning and painful metal-on-metal hip prostheses, to characterize these lesions with use of magnetic resonance imaging, and to assess the relationship between their presence and acetabular cup position with use of three-dimensional computed tomography. We performed a case-control study to compare the magnetic resonance imaging findings of patients with a well-functioning unilateral metal-on-metal hip prosthesis and patients with a painful prosthesis (defined by either revision arthroplasty performed because of unexplained pain or an Oxford hip score of <30 of 48 possible points). Thirty patients with a painful hip prosthesis and twenty-eight controls with a well-functioning prosthesis were recruited consecutively. All patients also underwent computed tomography to assess the position of the acetabular component. Thirty-four patients were diagnosed with a pseudotumor. However, the prevalence of pseudotumors in patients with a painful hip (seventeen of thirty, 57%) was not significantly different from the prevalence in the control group (seventeen of twenty-eight, 61%). No objective differences in pseudotumor characteristics between the groups were identified. No clear association between the presence of a pseudotumor and acetabular component position was identified. The Oxford hip score in the group with a painful hip (mean, 20.2; 95% confidence interval [CI], 12.7 to 45.8) was poorer than that in the control group (mean, 41.2; 95% CI, 18.5 to 45.8; p ≤ 0.0001). A periprosthetic cystic pseudotumor was diagnosed commonly (in thirty-four [59%] of the entire study cohort) with use of metal artifact reduction sequence (MARS) magnetic resonance imaging in this series of patients with a metal-on-metal hip prosthesis. The prevalence of pseudotumors was similar in patients with a well-functioning hip prosthesis and patients with a painful hip. Pseudotumors were also diagnosed commonly in patients with a well-positioned acetabular component. Although magnetic resonance imaging is useful for surgical planning, the presence of a cystic pseudotumor may not necessarily indicate the need for revision arthroplasty. Further correlation of clinical and imaging data is needed to determine the natural history of pseudotumors to guide clinical practice.

99mTc-labeled ubiquicidin scintigraphy

SummaryAim: Hip prosthesis implantation has witnessed a significant increase in recent years. Despite the advantages of this surgical procedure, it has some complications, the most serious of which is prosthetic infection. This study was conducted to investigate the feasibility of 99mTc-UBI scintigraphy in detection of infectious foci in painful hip prosthesis. UBI (Ubiquicidin 29–41) is an antimicrobial peptide fragment with the ability to target the bacterial colony directly. Patients, methods: 34 patients, aged 20–79 years, with painful hip prosthesis were included. 99mTc-UBI scan and three phase bone scan were performed and two nuclear medicine specialists interpreted the UBI scans with and without bone scan results at hand. Both qualitative and semiquantitative methods were used to interpret the 30 minute post injection images. The patients were actively followed up. According to the surgical findings, microbiological culture and active follow up, final diagnosis was made. Results: 24 negative and 10 positive UBI scans were recorded. The sensitivity, specificity, negative and positive predictive values and accuracy of the study were all 100%. Bone scan did not have any influence on UBI interpretation. We were able to achieve excellent differentiation between infected and non-infected prostheses with a cut off value of 1.8 for target to non target (T/NT) ratio. No adverse effects were noticed following UBI scan. Conclusion: Based on the findings, the authors believe that 99mTc-UBI scintigraphy, with its high sensitivity and specificity, provides the physician with an excellent tool for differentiating infection from aseptic loosening of hip prostheses. Using this radiopharmaceutical, it is possible to obtain highly accurate results only 30 minutes after the beginning of the study.

Magnetic resonance imaging of painful total hip replacement: detection and characterisation of periprosthetic fluid collection and interobserver reproducibility

The purpose of our study was to demonstrate the diagnostic value of magnetic resonance imaging (MRI) when measuring and characterising periprosthetic fluid collections in patients with painful hip prosthesis and to provide an estimation of interobserver reproducibility. Nineteen patients (mean age 59±13 years) with painful total hip replacement and clinical suspicion of infection underwent MRI. Images were reviewed blindly by two musculoskeletal radiologists with different levels of experience who evaluated the presence/absence of soft tissue oedema or fluid collection (when present, three-plane maximal diameters were measured; involvement of skin/subcutaneous/deep tissues or prosthesis were estimated; fluid was classified as serous/purulent/haematic according to signal behaviour). Interobserver agreement was calculated (Cohen's ). A total of 26 MRI studies were carried out (three patients underwent two and two patients underwent three MRI examinations). Both readers detected soft tissue oedema (13/26, 50%) or fluid collection (21/26, 81%) and characterised the fluid as serous (9/21, 43%), purulent (8/21, 38%) or haematic (4/21, 19%). The collection involved skin/subcutaneous tissues (16/21, 76%), deep soft tissues (19/21, 91%) or the implant (12/21, 57%). For all evaluations, interobserver agreement was complete (=1). No significant differences were found between the measurements of the collections (p>0.258). MRI is highly reproducible in detection, localisation, quantification, and characterisation of fluid collections when the presence of implant infection is clinically suspected.

Antigranulocyte scintigraphy in infected hip prosthesis: the diagnostic importance of delayed 20–24-h imaging and semiquantitative analysis

To evaluate clinical efficacy of a dual-time acquisition protocol, which included 4 and 20/24-h imaging with antigranulocyte antibody scintigraphy (LeukoScan) combined with semiquantitative analysis in the diagnosis of infection in painful hip prosthesis. Sixty-seven consecutive patients with hip prosthesis were enrolled in this research project: 35 females, 32 males, mean age of 56.3 years. All patients had clinical and biochemical suspicious of infection. Each prosthesis had been implanted 3 months to 12 years before enrollment in this study. Twenty-four patients were on antibiotic therapy at the time of scintigraphy. Seven patients had bilateral hip prosthesis, one painful and the other painless: the seven painless prostheses were considered controls. LeukoScan examination was performed both at early (4 h) and delayed (20/24 h) times. The scintigraphic data were assessed both by visual and semiquantitative methods by three experienced nuclear medicine physicians blinded to clinical, laboratory and radiographic results. The uptake was graded visually by a 4-point scale: intense=3, moderate=2, mild=1 and absent=0. The semiquantitative analysis was obtained by a region of interest (ROI) analysis used in the anterior views to measure the ratio between the mean radioactivity in the prosthesis and the background radioactivity in the early and delayed images. An increase in the intensity of uptake of at least one scale-step at visual analysis and 20% at semiquantitative ROI analysis at the dual-time (early vs. delayed) LeukoScan was considered consistent with infection, whereas a stable or decreasing pattern was judged a negative result. Three-phase 99mTc-hydroxymethane diphosphonate bone scan was also performed routinely. Final diagnosis was determined at surgery and/or long-term clinical and imaging follow-up. At visual analysis, sensitivity for both early and delayed imaging was 94%, whereas specificity was 71% for early imaging and 83% for early and delayed imaging approach. At semiquantitative ROI analysis, sensitivity remained 94%, whereas specificity rose slightly to 73% for early imaging and to 90% for early and delayed imaging combined. Of note, four false-positive early scans were diagnosed correctly as negative on delayed imaging showing a decreasing pattern in uptake intensity. Sensitivity and specificity were similar whether patients were on or off antibiotic therapy. Our data show that early imaging LeukoScan is highly sensitive in evaluating septic prosthesis, but it is not optimally specific. Although the dual-time LeukoScan is capable of significantly increasing specificity for detecting infection. The semiquantitative ROI analysis further increased the specificity. Concomitant antibiotic treatment did not seem to influence the diagnostic efficacy of LeukoScan scintigraphy in detecting infected hip prosthesis.

Potential use of bone marrow scintigraphy in suspected prosthetic hip infection evaluated with 99mTc-HMPAO-leukocytes

To evaluate the usefulness of (99m)Tc-Sulphur colloid when combined with leukocyte scintigraphy in suspected prosthetic hip infection, comparing the results with information from (99m)Tc-HMPAO-leukocyte scintigraphy alone. Seventy patients (42 women, 28 men; mean age 68 +/- 13 years) with painful hip prostheses and suspicion of infection were evaluated prospectively. All patients had bone scintigraphy, (99m)Tc-HMPAO-labelled white blood cell scintigraphy and (99m)Tc-Sulphur colloid bone marrow scintigraphy. ESR and CRP levels were measured in all patients. The final diagnosis was made with microbiological findings or by clinical follow up of at least 12 months. Infections were diagnosed in 12 of the 70 patients (3 coagulase-negative Staphylococcus, 2 Staphylococcus aureus, 2 Staphylococcus epidermidis, 2 enterococcus and 3 polymicrobial agents). ESR and CRP values were higher in patients with infection than in patients without infection (51.8 +/- 29.4 vs. 25.4 +/- 16.4 and 2.8 +/- 2.2 vs. 1.1 +/- 1.3, respectively; p < 0.05). Bone scintigraphy did not show a characteristic pattern to differentiate infection from aseptic loosening. The pool phase of the bone scintigraphy was positive in only 3/12 patients with infection (25 %). Sensitivity and specificity of the leukocyte scintigraphy was 83 % and 57 %, respectively. When the results of the bone marrow scintigraphy were added, these values increased to 92 % and 98 %, respectively. Performing bone marrow scintigraphy significantly improves results when compared with leukocyte scintigraphy alone in the diagnosis of infected hip prostheses. Bone scintigraphy did not help to differentiate aseptic loosening from infection in this series.

FDG-PET Imaging Can Diagnose Periprosthetic Infection of the Hip

A battery of diagnostic tests is often required to differentiate aseptic loosening from periprosthetic infection since the gold standard remains elusive. We designed a prospective study to determine the accuracy of fluorodeoxyglucose positron emission tomography (FDG-PET) imaging in diagnosing periprosthetic infection in a large multicenter setting. One hundred and thirteen patients with 127 painful hip prostheses were evaluated by FDG-PET. Images were considered positive for infection if PET demonstrated increased FDG activity at the bone-prosthesis interface of the femoral component. A combination of preoperative tests, intraoperative findings, histopathology, and clinical followup constituted the gold standard for diagnosing infection. Among the 35 positive PET scans, 28 hips were confirmed infected according to our criteria for diagnosing periprosthetic infection. Of the 92 hip prostheses with negative FDG-PET findings, 87 were considered aseptic. The sensitivity, specificity, positive and negative predictive values for FDG-PET were 0.85 (28 of 33), 0.93 (87 of 94), 0.80 (28 of 35), and 0.95 (87 of 92), respectively. The overall accuracy of this novel noninvasive imaging modality reached 0.91 (115 of 127). Based on our results, FDG-PET appears a promising and accurate diagnostic tool for distinguishing septic from aseptic painful hip prostheses. Level II, diagnostic study. See Guidelines for Authors for a complete description of levels of evidence.

FDG-PET Imaging in the Differentiation of Infected from Noninfected Painful Hip Prosthesis

FDG-PET Imaging in the Differentiation of Infected from Noninfected Painful Hip Prosthesis

White blood cell scintigraphy for differentiation of infection and aseptic loosening: A retrospective study of 76 painful hip prostheses

Background Diagnosis of an infected arthroplasty is often difficult. Fever, abnormal physical findings, radiographic changes, findings at bone scintigraphy, an elevated erythrocyte sedimentation rate, CRP, and leucocytosis are not specific enough. We evaluated the diagnostic value of white blood cell scintigraphy.Methods We retrospectively reviewed 76 cases (66 patients) admitted for white blood cell scintigraphy with a clinical suspicion of infection in a hip prosthesis during the period 1995–2003. The leukocytes were labeled with 99mTc-HMPAO or with 111In-oxin. Anterior and posterior views were taken of both hip joints at 3 different time points after injection: 1 h, 3 h, and 22 h. Infection was verified by means of bacteriological cultures, histopathological findings, intraoperative frozen sections, and follow-up (up to 3.5 years).Results Of 76 scintigraphies, 51 were negative and 25 were positive. There were 81% true positive, 94% true negative, 6% false positive, and 19% false negative outcomes.Interpretation White blood cell scintigraphy with additional late imaging is an effective tool for differentiation between loosening and infection in painful hip arthroplasty.

Comparison of Fluorodeoxyglucose Positron Emission Tomography and 111Indium–White Blood Cell Imaging in the Diagnosis of Periprosthetic Infection of the Hip

We aimed to compare the accuracy of fluorodeoxyglucose positron emission tomography (FDG-PET) with technetium-99m sulfur colloid 111indium-labeled white blood cell scintigraphy (TcSC-Ind BM/WBC) in diagnosis of periprosthetic infection. Eighty-nine patients with 92 painful hip prostheses were recruited prospectively and given the option of undergoing either combined FDG-PET and TcSC-Ind BM/WBC or FDG-PET only. FDG-PET correctly diagnosed 20 of the 21 infected cases (sensitivity, 95.2%) and ruled out infection in 66 of the 71 aseptic hips (specificity, 93%) corresponding to a positive predictive value of 80% (20/25) and a negative predictive value of 98.5% (66/67). TcSC-Ind BM/WBC correctly identified 5 of the 10 infected cases (sensitivity, 50%) and 39 of 41 aseptic cases (specificity, 95.1%) corresponding to a positive and negative predictive values of 41.7% (5/12 cases) and 88.6% (39/44 cases), respectively. Based on these preliminary results, FDG-PET appears to be a promising diagnostic tool for distinguishing septic from aseptic painful hip prostheses.

The diagnostic value of digital subtraction arthrography and radionuclide bone scan in revision hip arthroplasty

A prospective analysis of plain serial radigraphs (PSR), digital subtraction arthrography (DSA), and radionuclide bone scans (RBS) was performed in 56 cemented total hip arthroplasties to evaluate the efficacy and usefulness of each study in the diagnosis of loosening. To avoid selection bias in the evaluation of DSA and RBS, the decision to perform repeat surgery was based exclusively on the clinical history and PSR. Results of each study were compared with intraoperative assessment of the status of components and expressed in terms of sensitivity, specificity, and accuracy. Overall accuracy for the acetabular component by PSR was 66%; by DSA, 93%; by RBS, 46%. Overall accuracy for the femoral component by PSR was 79%; by DSA, 93%; RBS, 50%. Our results indicate that DSA can be recommended as a further analysis in cases with a painful hip prosthesis and no or inconclusive findings on PSR. RBS did not give any useful information and cannot be recommended routinely.

Analysis of 18F-FDG uptake patterns in PET for diagnosis of septic and aseptic loosening after total hip arthroplasty

Identification of typical patterns for fluorodeoxy-glucose (FDG) uptake in positron emission tomography (PET) to detect aseptic loosening of hip prosthesis (ace-tabular and/or femoral component) and prosthetic infection. 18 patients with painful hip prosthesis underwent PET using a dedicated full ring scanner after application of 200-300 MBq FDG. The interface between bone and surrounding soft tissue or bone as displayed on coronal slices was divided into 12 segments in accordance with the classifications of Delee and Gruen. FDG uptake in each of the segments was scored (0-3) by two independent observers. Intraoperative findings were regarded as the gold standard. After surgical revision 14 acetabular components and 9 femoral components were found to be loose and prosthetic infection was present in 7 prostheses. Loosening of the acetabular component was correlated to enhanced uptake in the middle of the acetabular interface, while loosening of the femoral component was correlated to enhanced uptake in the proximal and middle segment of the lateral femoral interface and the proximal segment of the medial femoral interface. A similar pattern was found in prosthetic infection with high uptake along the middle portion of the lateral femoral interface. In 6 of 7 infected prostheses loosening of the acetabular and of the femoral component was present. Taking the typical uptake patterns as criteria for loosening and grade 3 uptake as an additional criterion for septic loosening the accuracy of PET imaging in the detection of loosening of the acetabular or the femoral component and of prosthetic infection was 72, 78 and 89%, respectively. This pilot study presents FDG-PET as a promising diagnostic tool for patients with painful hip prostheses. Its clinical value should be evaluated in a larger patient population.