Imaging of hip arthroplasty

Imaging in Periprosthetic Joint Infection Diagnosis: A Comprehensive Review

Various imaging methods assist in diagnosing periprosthetic joint infection (PJI). These include radiological techniques such as radiography, computed tomography (CT), magnetic resonance imaging (MRI), and ultrasound (US); as well as advanced nuclear medicine techniques including bone scintigraphy (BS), anti-granulocyte antibody imaging (AGS), leukocyte scintigraphy (LS), and fluorodeoxyglucose positron emission tomography (FDG-PET and FDG-PET/CT). Each imaging technique and radiopharmaceutical has been extensively studied, with unique diagnostic accuracy, limitations, and benefits for PJI diagnosis. This review aims to detail and describe the most commonly used imaging techniques and radiopharmaceuticals for evaluating PJI, focusing particularly on knee and hip arthroplasties.

Imaging approach to prosthetic joint infection

The diagnosis of prosthetic joint infection (PJI) remains challenging, despite multiple available laboratory tests for both serum and synovial fluid analysis. The clinical symptoms of PJI are not always characteristic, particularly in the chronic phase, and there is often significant overlap in symptoms with non-infectious forms of arthroplasty failure. Further exacerbating this challenge is lack of a universally accepted definition for PJI, with publications from multiple professional societies citing different diagnostic criteria. While not included in many of the major societies' guidelines for diagnosis of PJI, diagnostic imaging can play an important role in the workup of suspected PJI. In this article, we will review an approach to diagnostic imaging modalities (radiography, ultrasound, CT, MRI) in the workup of suspected PJI, with special attention to the limitations and benefits of each modality. We will also discuss the role that image-guided interventions play in the workup of these patients, through ultrasound and fluoroscopically guided joint aspirations. While there is no standard imaging algorithm that can universally applied to all patients with suspected PJI, we will discuss a general approach to diagnostic imaging and image-guided intervention in this clinical scenario.

Diagnostic and prognostic relevance of plain radiographs for periprosthetic joint infections of the hip: a literature review

Conventional radiography is regularly used to evaluate complications after total hip arthroplasty. In various recent consensus meetings, however, plain radiographs of a potentially infected hip joint have been judged as being only relevant to exclude diagnoses other than infection. Solid data on radiographic presentations of periprosthetic joint infection (PJI) are scarce. As a result, the prognostic value of radiological features in low-grade PJI remains uncertain. The present review article aims to present an overview of the available literature and to develop ideas on future perspectives to define the diagnostic possibilities of radiography in PJIs of the hip. The primary outcome of interest of this systematic review was the radiologic presentation of periprosthetic joint infections of the hip. As secondary outcome of interest served the sensitivity and specificity of the radiologic presentation of periprosthetic joint infections. Of the included articles, 26 were reviews, essays, or case reports and only 18 were clinical studies. Typical radiologic abnormalities of PJI were a periosteal reaction, a wide band of radiolucency at the cement-bone or metal-bone interface, patchy osteolysis, implant loosening, bone resorption around the implant, and transcortical sinus tracts. The frequency of their occurrence is still inadequately defined. A deeper understanding of the underlying causes and the relation between microorganisms to radiologic abnormalities can probably help clinicians in the future to diagnose a PJI. This is why further research shall focus on the radiographic features of PJI.

Deviation of Latitude Cut: A Simple Sign to Differentiate Total Hip Arthroplasty from Hemiarthroplasty in Radiography

This study aims to propose latitude cut deviation for differentiating hip arthroplasty types and evaluate its diagnostic utility in distinguishing total hip arthroplasty (THA) from hemiarthroplasty using radiography. After assessing various cup designs from top manufacturers for THA and hemiarthroplasty, we conducted a retrospective study on 40 patients (20 THA and 20 hemiarthroplasty). Three readers independently evaluated the radiographs, assessing acetabular sparing, cup-bone interface texture, and latitude cut deviation. Diagnostic performance and inter-observer agreement were compared using receiver operating characteristic curves and the Fleiss kappa coefficient. Latitude cut deviation measured on implant designs ranged from 19% to 42% in hemiarthroplasty and from -12% to 9% in THA. The sensitivity, specificity, and accuracy used to distinguish THA from hemiarthroplasty were 60-85%, 55-95%, and 62.5-77.5% for acetabular sparing; 100%, 50-80%, and 75-90% for cup-bone interface texture; and 100%, 90-100%, and 95-100% for latitude cut deviation. Inter-observer agreement for acetabular sparing, cup-bone interface texture, and latitude cut deviation ranged from moderate to excellent (κ = 0.499, 0.772, and 0.900, respectively). The latitude cut deviation exhibited excellent diagnostic performance and inter-reader agreement in distinguishing hemiarthroplasty from THA on radiographs, offering a concise way to identify hip arthroplasty type.

Hip and Knee Arthroplasty: A Review of Complications and Advances in Imaging

Arthroplasty-related complications are challenging to diagnose as they often present with nonspecific signs and symptoms, and can lead to long-term morbidity if inadequately managed. The difficulty in imaging implants is compounded by its intrinsic propensity to artifacts. Strategies to reduce this include: Judicious use of the appropriate imaging modality for the relevant clinical indication; knowledge of optimizing imaging acquisition parameters; and use of metal artifact reduction (MAR) software. We review the literature on expected normal appearances of hip and knee arthroplasties, findings of arthroplasty-related complications on various imaging modalities, advances in imaging techniques, and subsequently, suggest an algorithm for painful arthroplasty assessment. Serial radiographs remain key in identifying subtle changes in component position, hardware failure, periprosthetic osteolysis, and potential for loosening, given their ready availability, high resolution, and minimal metal-related artifact. Computed tomography with MAR provides 3D assessment and information on bone stock for surgical planning and custom implants. Magnetic resonance imaging with MAR can identify complications at earlier stages, such as loosening, capsular dehiscence in instability, and periprosthetic edema in nondisplaced fractures. It has high diagnostic performance in infection (lamellated synovitis), particle disease, adverse reactions to metal debris, in addition to demonstrating impingement on neurovascular structures. Nuclear medicine imaging is used as a problem-solving tool and is valuable in its high negative predictive value. Novel imaging techniques can further reduce artifacts and improve visualization of the implant-bone interface, and machine learning can facilitate image interpretation although attaining sufficient data and clinical validation will be challenging.

Imaging of total hip arthroplasty: Part I – Implant design, imaging techniques, and imaging of component wear and fracture

Despite being one of the most reliable procedures in orthopedic surgery, complications can occur after total hip arthroplasty, and radiology plays an essential role in their evaluation. This article will review the various types of hip arthroplasty and their normal appearances on imaging, followed by mechanisms and imaging appearances of component wear and fracture.

Diagnosis and Detection of Subtle Aseptic Loosening in Total Hip Arthroplasty

Aseptic loosening is a common cause of revision total hip arthroplasty (rTHA), and with the rising number of primary THAs, revisions for aseptic loosening represent a significant burden for arthroplasty surgeons. Aseptic loosening remains a diagnostic and management challenge. Loosening can occur as a result of inadequate initial fixation, mechanical loss of fixation over time, or a biological loss of fixation over time. However, in most cases, etiology is multifactorial, involving all 3 factors. The diagnosis of aseptic loosening involves a careful history, focused clinical exam, and thorough evaluation of imaging using several diagnostic modalities. The careful evaluation of serial radiographs remains the cornerstone of diagnosis with additional input from advanced imaging modalities such as FDG-PET, DEXA, MRI, and several others, each offering unique advantages and disadvantages. In certain patients, history and physical exam might be the only initial obvious signs of loosening, and thus, unexplained continuous pain augmented by imaging findings serves as an indication for revision surgery.

New Evaluation Method for Bone Formation around a Fully Hydroxyapatite-Coated Stem Using Digital Tomosynthesis: A Retrospective Cross-Sectional Study

Digital tomosynthesis (DTS) is a new imaging technique derived from radiography, and its usefulness has been gradually reported in the field of orthopedic diagnosis in recent years. A fully hydroxyapatite (HA)-coated stem, which is used for total hip arthroplasty (THA), is a type of cementless stem that has been widely used recently and reported to have good results. However, stem loosening on plain radiographs is difficult to determine in some cases due to cancellous condensation around the stem. In this retrospective cross-sectional study, we compared the results of plain radiography versus DTS to evaluate the imaging findings after THA using a fully HA-coated stem. Twenty joints each in the 3 y and 1 y postoperative groups underwent plain radiography and DTS. On DTS, bone formation around the stem was confirmed in all cases; however, this formation was not reproducible on plain radiography, and there were cases in which the reaction could not be confirmed or cases with cancellous condensation resembling reactive lines. This reaction was not reproducible on plain radiographs, and in some cases, the reaction could not be confirmed, or there were cases with cancellous condensation that resembled reactive lines. Therefore, DTS was useful in the diagnosis of bone formation around the implant.

Imaging update in arthroplasty

Imaging of metal implants has historically been difficult, regardless of the applied modality. The number of primary arthroplasties is increasing over the years. With it, we expect the number of symptomatic complications to increase as well. Acquiring accurate imaging for diagnosis and treatment planning for these cases is of paramount importance. Significant advancements have been made to reduce artifacts, leading to better imaging representation of arthroplasty. This review article would give a background on the current ways of imaging arthroplasty and metal implants, covering recent advances in imaging techniques.

15-year follow-up of MoM 36-mm THA: clinical, laboratory, and radiological (CT and MRI) prospective assessment

INTRODUCTION

There is limited knowledge of the long-term results of metal-on-metal total hip arthroplasty (MoM THA), particularly concerning adverse local tissue reaction (ALTR), Co/Cr ions level and revision rate. Even if MoM bearing surfaces are no longer used, long-term data could help in defining the course and best management for these patients. The purpose of this study is to investigate the clinical outcomes, describe radiological findings including CT metal artefact reduction algorithm for orthopaedic implants (O-MAR) and MRI multi acquisition variable resonance image combination (MAVRIC) in 36-mm MoM THA.

METHODS

In this long-term prospective study, 46 consecutive patients with primary MoM THA (mono- or bilateral) were enrolled between 2004 and 2005. Pinnacle acetabular cup, Summit cementless stem with 36-mm metal head and Ultamet CoCr alloy liner (Depuy Inc.) were implanted, in the same centre by the same senior surgeon. Patients were reviewed at 5-, 10- and 15-years, including Co/Cr levels and standard radiographs at every follow-up, whilst the 15-year follow-up included hip sonography, MRI MAVRIC and CT O-MAR.

RESULTS

At 15 years, the overall survival rate of the implants (both stems and cups) was 83% (30/36). Revisions were performed in 9% (4/46) because of ALTR, 2% (1/46) septic loosening and 2% periprosthetic fracture. Both Cr and Co concentration increased over time, even though remaining at low level risk at 15 years: Co from 0.11 (+/- 0.18) to 4.29 (+/- 3.26) and Cr from 0.38 (+/- 0.32) to 1.37 (+/- 1.15). Functional scores in non-revised patients showed good to excellent results in more than 90%. Engh-score correlated with time from surgery (p = 0.017) and with sonographic, CT and RM findings (p < 0.05). Concordance has been found between CT and MRI findings (sign-rank test, p = 0.241; Intraclass Correlation Coefficients 0.987); however, no specific MRI or CT lesion patterns could be recognised among symptomatic and non-symptomatic patients.

DISCUSSION

The long-term rate of ALTR after 36-mm MoM THA was comparable with previous studies; a regular follow-up for those implants is mandatory. During follow-up Co-Cr levels increased over time and radiography was a suitable screening technique; the Engh score in particular, proved to be a reliable assessment tool. CT O-MAR and MRI with MAVRIC protocols may add valuable data in clinical practice, although MRI is significantly more efficient than CT in the identification of ALTR lesions, peri-articular effusion and in the evaluation of soft tissues.

Evaluation of peri-prosthetic radiolucent lines surrounding the cementless femoral stem using digital tomosynthesis with metal artifact reduction: a cadaveric study in comparison with radiography and computed tomography

Background

The traditional criterion for the diagnosis of implant loosening in total hip arthroplasty (THA) was once defined as a radiolucent line of >2 mm in width, based on plain radiography. Recent progress in imaging technology has allowed for the identification of complete radiolucent lines of ≤2 mm around the whole prosthesis as the basis for diagnosing component loosening in the absence of component migration. This study aimed to compare the sensitivity and specificity of digital tomosynthesis with metal artifact reduction with those of radiography and conventional computed tomography (CT) for detecting radiolucent lines of ≤2 mm surrounding cementless femoral stems of different widths.

Methods

The medullary canals of 4 cadaveric femurs were broached to 13 mm in diameter. Cylindrical cementless femoral stems with diameters of 9, 10, 11, 12, and 13 mm were sequentially inserted into each femur, creating 5 groups of radiolucent lines 2.0, 1.5-1.6, 1.1-1.2, 0.5-0.6, and 0 mm in diameter, respectively. Imaging by tomosynthesis, radiography, and CT was conducted for each radiolucent line model. The width information of the radiolucent line models was used as a reference standard for calculating sensitivity and specificity: observations in the group of 0 mm were used for calculating specificity, and those in the other four groups were used for sensitivity. The differences in sensitivity and specificity between the imaging methods were compared with chi-square test, and the 95% confidence intervals of improvements in the sensitivity and specificity of tomosynthesis compared with radiography and CT were calculated using mixed effects models.

Results

The overall sensitivity of tomosynthesis (63.3%) for detecting radiolucent lines ≤2 mm wide was significantly higher (P<0.017) than that of radiography (20.5%) and CT (50.2%), an improvement of 58.2%±3.1% (95% CI, P<0.001) and 21.7%±7.1% (95% CI, P<0.001) compared to radiography and CT, respectively. The sensitivity values for detecting radiolucent lines in all four groups by tomosynthesis and CT were significantly higher than those of radiography (P<0.017). Tomosynthesis also had significantly higher sensitivity than CT (P<0.017) in detecting radiolucent line ≤1.2 mm wide. The specificity of TMAR, radiography, and CT for detecting radiolucent lines was 87.5%, 92.5%, and 82.5%, respectively, with no significant difference (P>0.017).

Conclusions

Digital tomosynthesis with metal artifact reduction had significantly higher sensitivity than radiography for detecting radiolucent lines ≤2 mm wide surrounding cementless femoral stems. It also displayed higher sensitivity than CT for detecting radiolucent lines ≤1.2 mm in width. With a higher rate of detection for radiolucent lines narrower than 2 mm, tomosynthesis has the potential to improve the accuracy of early diagnosis of cementless THA stem loosening in clinical practice.

Radiological Imaging Evaluation of the Failing Total Hip Replacement

Total hip replacements (THR) have been performed in the UK from the 1960s and since then we have seen surgical techniques, the design of implants, and imaging modalities rapidly develop. This paper will aim to review the different complications and imaging appearance which help to evaluate each problem. As for all investigations for bone and joints, a radiograph is the first imaging to be performed for any patient with a THR and can detect a majority of complications. CT is relatively low-cost, simple to perform and easily available making it an excellent tool to supplement radiographs when trying to evaluate a hip prosthesis. Single photon emission computed tomography with CT (SPECT-CT) is an emerging modality which has shown to combine the sensitivity that bone scintigraphy offers with the high specificity of CT. SPECT imaging also has the advantage of showing the bone's metabolic activity and is less prone to metal artifact than Magnetic resonance imaging (MRI). MRI has evolved to become an important diagnostic tool for the evaluation of THR in the post-operative period. Optimized pulse sequences and metal artifact reduction techniques have made MRI a useful tool in diagnosis of soft tissue abnormalities and is particularly useful in identifying adverse local tissue reactions in metal on metal implants. CT and MRI are accurate in identifying the diagnosis of most causes of THR complications except infection. Research confirms that leukocyte-marrow scintigraphy is the modality of choice for accurately diagnosing prosthetic joint infection and reassures us of its superiority over other nuclear medicine imaging. However, due to the limited availability and increased costs when performing leukocyte-marrow scintigraphy, CT and SPECT-CT would be a more preferred option when suspecting prosthesis infection. Ultrasound (US) has a limited role in the assessment of most THR complications but can be useful to identify peri-prosthetic fluid collections and the presence of soft tissue sinus tracts. Being aware of the imaging modalities that are available to orthopedic surgeons, and discussing these challenging cases with specialist radiologists will enable optimal management of THR complications.

Rapid Acetabular Chondrolysis following Hemiarthroplasty of the Hip: A Poor Prognostic Sign

Both hemiarthroplasty and total hip arthroplasty have been well described as effective methods of management for displaced femoral neck fractures in the elderly. Acetabular erosion is a common long-term complication of hemiarthroplasty. We present a case in which rapid acetabular erosion occurs within weeks of hemiarthroplasty, ultimately leading to an acetabular fracture and need for revision to total hip arthroplasty. Early and rapid acetabular erosion following hip hemiarthroplasty has not been well documented in current literature. It may lead to acetabular fracture and may be secondary to infectious causes. If encountered, an infection workup should be initiated.

Reduction of metal artifacts from unilateral hip arthroplasty on dual-energy CT with metal artifact reduction software

Background The evaluation of hip arthroplasty is a challenge in computed tomography (CT). The virtual monochromatic spectral (VMS) images with metal artifact reduction software (MARs) in spectral CT can reduce the artifacts and improve the image quality. Purpose To evaluate the effects of VMS images and MARs for metal artifact reduction in patients with unilateral hip arthroplasty. Material and Methods Thirty-five patients underwent dual-energy CT. Four sets of VMS images without MARs and four sets of VMS images with MARs were obtained. Artifact index (AI), CT number, and SD value were assessed at the periprosthetic region and the pelvic organs. The scores of two observers for different images and the inter-observer agreement were evaluated. Results The AIs in 120 and 140 keV images were significantly lower than those in 80 and 100 keV images. The AIs of the periprosthetic region in VMS images with MARs were significantly lower than those in VMS images without MARs, while the AIs of pelvic organs were not significantly different. VMS images with MARs improved the accuracy of CT numbers for the periprosthetic region. The inter-observer agreements were good for all the images. VMS images with MARs at 120 and 140 keV had higher subjective scores and could improve the image quality, leading to reliable diagnosis of prosthesis-related problems. Conclusion VMS images with MARs at 120 and 140 keV could significantly reduce the artifacts from hip arthroplasty and improve the image quality at the periprosthetic region but had no obvious advantage for pelvic organs.

Accuracy of Digital Tomosynthesis With Metal Artifact Reduction for Detecting Osteointegration in Cementless Hip Arthroplasty

BACKGROUND

Cementless hip arthroplasty is increasingly gaining popularity worldwide. Radiologic identification of osteointegration is key to confirming biologic fixation. We conducted the study reported here to determine the sensitivity and specificity of digital tomosynthesis with metal artifact reduction (TMAR), radiography, and conventional computed tomography in detecting osteointegration in cementless hip arthroplasty.

METHODS

We prospectively included data for 24 patients who underwent revision hip arthroplasty in our hospital, with 13 femoral and 14 acetabular cementless components retrieved that contained solid evidence of biologic fixation. All patients underwent 3 examinations before surgery, and evidence of osteointegration on retrieved prostheses was used as the reference standard. Seven orthopedic surgeons evaluated these images independently using uniform criteria.

RESULTS

On the femoral side, the sensitivity and specificity of detecting osteointegration were 73.8% ± 4.6% and 94.3% ± 1.5%, respectively, for TMAR; 50.4% ± 5.3% and 87.8% ± 2.1%, respectively, for radiography; and 36.4% ± 5.1% and 90.9% ± 1.9%, respectively, for CT. On the cup side, the corresponding values were 60.2% ± 8.3% and 86.4% ± 5.7%, respectively, for TMAR; 45.9% ± 8.5% and 66.4% ± 7.8%, respectively, for radiography; and 45.1% ± 8.5% and 73.5% ± 7.3%, respectively, by computed tomography.

CONCLUSION

TMAR significantly improved the accuracy osteointegration detection in cementless hip arthroplasty (P < .017).

Validity and Reliability of Intraoperative Radiographs to Assess Leg Length During Total Hip Arthroplasty: Correlation and Reproducibility of Anatomic Distances

BACKGROUND

Leg length discrepancy after total hip arthroplasty is a frequent complication. The aim of this study was to assess the validity (correlation) and reproducibility (inter-rater agreement) of various intraoperative hip radiographs measures to estimate leg length.

METHODS

Patients were included if they were aged 15 years or older; were eligible for a total hip arthroplasty, and were operated in lateral recumbent. An intraoperative hip radiograph was performed with the definitive implants in place. At 6 weeks postoperatively, anteroposterior pelvis radiograph was taken. We used 3 measures to assess leg length: the height from the ischial tuberosity to the lesser trochanter (LTI), the height from the center of femoral head to the greater trochanter (GTC), and to the inferior teardrop (TC).

RESULTS

The study group consisted of 71 hips with an average age of 69 years (range, 24-92 years). The correlation was 0.545 (95% CI: 0.35-0.69) for GTC, 0.75 (95% CI: 0.61-0.84) for TC, and 0.70 (95% CI: 0.56-0.80) for LTI. Intraoperative and postoperative measures were statistically different for GTC (<0.0001) and TC (<0.0001), and not significant for LTI (P = .06). Reproducibility of these measures were excellent with intraclass correlation coefficients of 0.977, 0.814, and 0.983 for the GTC, TC, and LTI, respectively.

CONCLUSION

None of the parameters used to assess leg-length based on an intraoperative radiograph showed good correlation with the postoperative radiograph.

Higher reliability of triple-phase bone scintigraphy in cementless total hip arthroplasty compared to cementless bipolar hemiarthroplasty

Purpose

Periprosthetic infection is one of the main reasons for revision surgery after hip arthroplasty. The purpose of the present study is to compare the reliability of triple-phase bone scintigraphy (TPBS) in the diagnosis of periprosthetic infection between cementless total hip arthroplasty (THA) and bipolar hemiarthroplasty (BHA).

Methods

In this retrospective study, 52 patients were analyzed; 33 of them were performed with THA and 19 of them were performed with BHA. The exclusion criteria were cementation in previous surgery, romatological joint disorders, periprosthetic fracture and malignancy history. C reactive protein (CRP) and erythrocyte sedimentation (ESR) rate results were recorded preoperatively. Tissue samples from the different areas periprosthetic tissue were obtained for histopathological examination and sample tissue culture.

Results

In the present study, the sensitivity, specificity and accuracy were 90.9%, 77.3% and 81.8%, respectively, for THA and 77.8%, 60.0% and 68.4%, respectively, for BHA. Positive predictive values for THA and BHA were 66.7% and 63.6%, and negative predictive values were 94.4% and 75.0%, respectively.

Conclusions

Due to the higher sensitivity, specificity and accuracy, TPBS has a more reliable diagnostic value for cementless THA in the diagnosis of periprosthetic infection compared to cementless BHA.

•

Triple-phase bone scintigraphy is effective in ruling out infection with its higher sensitivity.

•

Triple-phase bone scintigraphy has relatively low specificity compared to its high sensitivity.

Developments in imaging methods used in hip arthroplasty: A diagnostic algorithm

BACKGROUND

Several imaging modalities can be used to diagnose complications of hip prosthesis placement. Despite progress in these imaging techniques, there are, as yet, no guidelines as to their respective indications.

METHODS

We formed a panel of experts in fields related to prosthesis imaging (radiology, nuclear medicine, orthopedic surgery) and conducted a review of the literature to determine the value of each modality for diagnosing complications following hip replacement.

RESULTS

Few recent studies have investigated the benefits related to the use of the latest technical developments, and studies comparing different methods are extremely rare.

CONCLUSIONS

We have developed a diagnostic tree based on the characteristics of each imaging technique and recommend its use. Computed topography was found to be the most versatile and cost-effective imaging solution and therefore a key tool for diagnosing the complications of hip replacement surgery.

Periprosthetic pathology in 'at risk' ceramic-on-polyethylene total hip arthroplasty: a clinical study using MARS-MRI in 50 patients

PURPOSE

Recent studies of metal-on-metal (MoM) total hip arthroplasty (THA) using metal-artefact-reducing-sequence software for magnetic resonance Imaging (MARS-MRI) have revealed remarkable soft tissue pathology around the hip, usually referred to as pseudotumours. Case reports describe identical pathology in non-MoM THA, but descriptive overviews of MRI abnormalities in patients with non-MoM prosthesis are scarce.

METHODS

A clinical study in a cohort of 50 ceramic-on-polyethylene (CoP) THA selected for high risk of peri-prosthetic pathology including 2 subgroups: (i) 40 patients with a high polyethylene (PE) wear rate (&gt;0.2 mm per year) and 5-12 years follow-up; (ii) 10 patients with a 2 to 5 years follow-up and a documented history of persistent complaints. All patients were clinically evaluated, MARS-MRIs were completed and chrome and cobalt serum samples were taken.

RESULTS

17 scans were normal (34%). Periprosthetic fluid collections were seen as a bursae iliopsoas (n = 12, 24%), in the trochanter bursae (n = 4, 8%) and in the surgical tract (n = 9, 18%). 1 case demonstrated a cyst on MARS-MRI resembling a pseudotumour as seen with MoM THA (2%). Intraosseous acetabular cysts were seen in 12 cases (24%), intraosseous trochanteric cysts in 10 cases (20%).

CONCLUSIONS

Soft tissue abnormalities after non-MoM THA are common in selected patients and can be clearly visualised with MARS-MRI. Pseudotumours as seen on MARS-MRI do occur in non-MoM hip arthroplasty but with low prevalence.

Precision and Accuracy of Measurements on CT Scout View

OBJECTIVES

The purposes of this study were to (1) investigate the limits of measurements on scout view in three computed tomography axes, x, y and z and (2) develop a model to provide better understanding of measurement accuracy.

METHODS

For the first objective, anteroposterior and lateral scout views of a Catphan phantom 200 mm in diameter and length were acquired with a GE scanner at 21 different table heights. Phantom measurements on scout view were performed by two experienced readers. The comparison of their measures provided estimation of precision. The accuracy was assessed by determining the bias, calculated as the difference between the values measured on scout view and the real phantom size. Second, a model was developed investigating the relationship between the dimensions of the object, its image, and the table height. This relationship was tested on our data.

RESULTS

Scout view measurements were precise, with less than 0.53% difference between readers. In addition, small biases of about 1 mm were detected in the z-axis, whatever the table height. In the other axes, serious biases from -13 to +73 mm were measured. Furthermore, at isocentre, overestimations up to 7 mm were shown. The results also indicated that biases in scout view measurements are because of the geometrical projection related to the object-detector distance.

CONCLUSIONS

Measurements in the table movement axis are precise and accurate, conferring to scout views an added value for preoperative planning in orthopedic surgery.

The Accuracy of Single Photon Emission Computed Tomography/Computed Tomography Arthrography in Evaluating Aseptic Loosening of Hip and Knee Prostheses

Aseptic loosening represents the most common complication associated with hip and knee arthroplasty and is a common indication for surgical revision in the post-arthroplasty population. The optimal imaging methodology in evaluating clinical suspected loosening is not well-defined. Our study retrospectively evaluated nuclear medicine arthrography with hybrid single photon emission computed tomography/computed tomography (SPECT/CT) in 38 patients (21 hip, 17 knee) compared with reference standards of surgical evaluation, spontaneous resolution of symptoms without revision, or a minimum of 1 year clinical and radiographic follow-up. Our study demonstrated a sensitivity of 100%, specificity of 96.0%, PPV of 92.9%, NPV of 100%, and accuracy of 97.4% with this imaging technique suggesting utility of nuclear medicine arthrography with SPECT/CT in the clinical evaluation of suspected aseptic loosening.

Total hip prosthesis CT with single-energy projection-based metallic artifact reduction: impact on the visualization of specific periprosthetic soft tissue structures

OBJECTIVES

To compare the image quality of CT with iterative reconstruction alone and in association with projection-based single-energy metal artifact reduction (SEMAR) for the visualization of specific periarticular soft tissue structures in patients with hip prostheses.

METHODS

CT studies from 48 consecutive patients with a hip prosthesis (24 unilateral and 24 bilateral) were retrospectively reconstructed using two different methods: iterative reconstruction (IR) alone and IR associated with SEMAR. The influence of metallic artifacts on the identification of various periarticular structures was evaluated subjectively by two readers. The image quality was compared in patients with unilateral and bilateral prostheses.

RESULTS

Visualization of periprosthetic soft tissue was significantly improved by the SEMAR algorithm (p < 0.0001). When SEMAR was associated with IR, the gluteus minimus and medius tendons, obturator internus muscle, prostate/uterus and bladder could be seen with medium or high confidence. There were no significant differences in image quality between patients with unilateral or bilateral prosthesis when SEMAR was used (p > 0.2). This algorithm increased the detection of periarticular masses by 30%.

CONCLUSION

SEMAR significantly improves the image quality of periarticular soft-tissue structures in patients with hip prostheses.

The utility of digital linear tomosynthesis imaging of total hip joint arthroplasty with suspicion of loosening: a prospective study in 40 patients

Aim. The clinical utility of digital linear tomosynthesis in musculoskeletal applications has been validated in only a few reports. Technical performance and utility in hip prosthesis imaging have been discussed in technical reports, but no clinical evaluation has been reported. The purpose of the current study was to assess the added clinical utility of digital linear tomosynthesis compared to radiography in loosening of total hip joint arthroplasty. Materials and Methods. In a prospective study, radiography and digital tomosynthesis were performed in 40 consecutive patients with total hip arthroplasty referred for suspect prosthesis loosening. Tomosynthesis images were compared to anterior-posterior (AP) and cross-table lateral radiographs regarding demarcation and extent of demineralization and osteolysis. Further noted were skeletal fractures, cement fractures, fragmentation, and artifacts interfering with the diagnosis. Results. Tomosynthesis was superior to radiography with sharper delineation of demineralization and osteolysis in the AP projection. A limitation was the inability to generate lateral tomosynthesis images, with inferior assessment of the area anterior and posterior to the acetabular cup compared to cross-table radiographs. Artifacts interfering with diagnosis were found in one hip. Conclusion. Tomosynthesis improved evaluation of total hip arthroplasty in the AP projection but was limited by the lack of lateral projections.