99Tcm-MDP, 67Ga-citrate and 111In-leucocytes for detecting prosthetic hip infection

Application of 68Ga-citrate PET/CT for differentiating periprosthetic joint infection from aseptic loosening after joint replacement surgery

AIMS

We aimed to evaluate the utility of ⁶⁸Ga-citrate positron emission tomography (PET)/CT in the differentiation of periprosthetic joint infection (PJI) and aseptic loosening (AL), and compare it with ^99mTc-methylene bisphosphonates (^99mTc-MDP) bone scan.

METHODS

We studied 39 patients with suspected PJI or AL. These patients underwent ⁶⁸Ga-citrate PET/CT, ^99mTc-MDP three-phase bone scan and single-photon emission CT (SPECT)/CT. PET/CT was performed at ten minutes and 60 minutes after injection, respectively. Images were evaluated by three nuclear medicine doctors based on: 1) visual analysis of the three methods based on tracer uptake model, and PET images attenuation-corrected with CT and those not attenuation-corrected with CT were analyzed, respectively; and 2) semi-quantitative analysis of PET/CT: maximum standardized uptake value (SUVmax) of lesions, SUVmax of the lesion/SUVmean of the normal bone, and SUVmax of the lesion/SUVmean of the normal muscle. The final diagnosis was based on the clinical and intraoperative findings, and histopathological and microbiological examinations.

RESULTS

Overall, 23 and 16 patients were diagnosed with PJI and AL, respectively. The sensitivity and specificity of three-phase bone scan and SPECT/CT were 100% and 62.5%, 82.6%, and 100%, respectively. Attenuation correction (AC) at 60 minutes and non-AC at 60 minutes of PET/CT had the same highest sensitivity and specificity (91.3% and 100%), and AC at 60 minutes combined with SPECT/CT could improve the diagnostic efficiency (sensitivity = 95.7%). Diagnostic efficacy of the SUVmax was low (area under the curve (AUC) of ten minutes and 60 minutes was 0.814 and 0.806, respectively), and SUVmax of the lesion/SUVmean of the normal bone at 60 minutes was the best semi-quantitative parameter (AUC = 0.969).

CONCLUSION

⁶⁸Ga-citrate showed the potential to differentiate PJI from AL, and visual analysis based on uptake pattern of tracer was reliable. The visual analysis method of AC at 60 minutes, combined with ^99mTc-MDP SPECT/CT, could improve the sensitivity from 91.3% to 95.7%. In addition, a major limitation of our study was that it had a limited sample size, and more detailed studies with a larger sample size are warranted. Cite this article: Bone Joint Res 2022;11(6):398-408.

SPECT/CT with a hybrid camera: a new imaging modality for the functional anatomical mapping of infections

Evaluation of: Bar-Shalom R, Yefremov N, Guralnik L et al. SPECT/CT using (67)Ga and (111)In-labeled leukocyte scintigraphy for diagnosis of infection. J. Nucl. Med. 47(4), 587-594 (2006). Labeled leukocytes and (67)Ga scan have been proved to be useful to image infectious and inflammatory processes. However, it is well known that nuclear imaging lacks precise anatomical landmarks. When highly specific tracers are used, the background activity may be too low to be used as a framework for spatial orientation. To overcome these drawbacks, the hybrid devices combining positron emission tomography/single photon emission computed tomography (SPECT) and computed tomography (CT) have been introduced, thereby providing a precise anatomical-functional correlation. The paper under evaluation highlights the emerging role of hybrid SPECT/CT to image infection with labeled leukocytes and (67)Ga. The authors suggest that fusion imaging can be of paramount value to locate the site of infection and to better define the extent of disease.

Nuclear medicine and the infected joint replacement

Nearly 700,000 hip and knee arthroplasties are performed annually in the United States. Although the results in most cases are excellent, implants do fail. Complications like heterotopic ossification, fracture, and dislocation are now relatively rare and easily diagnosed. Differentiating aseptic loosening, the most common cause of prosthetic joint failure, from infection, is important because their treatments are very different. Unfortunately, differentiating between these 2 entities can be challenging. Clinical signs of infection often are absent. Increased peripheral blood leukocytes, erythrocyte sedimentation rate, and C-reactive protein levels are neither sensitive nor specific for infection. Joint aspiration with Gram stain and culture is the definitive diagnostic test. Its specificity is in excess of 90%; its sensitivity is variable, however, ranging from 28% to 92%. Plain radiographs are neither sensitive nor specific and cross-sectional imaging modalities, such as computed tomography and magnetic resonance imaging, can be limited by hardware-induced artifacts. Radionuclide imaging is not affected by orthopedic hardware and is the current imaging modality of choice for suspected joint replacement infection. Bone scintigraphy is sensitive for identifying the failed joint replacement, but cannot be used to determine the cause of failure. Neither periprosthetic uptake patterns nor performing the test as a 3-phase study significantly improve accuracy, which is only about 50-70%. Thus, bone scintigraphy typically is used as a screening test or in conjunction with other radionuclide studies. Combined bone gallium imaging, with an accuracy of 65-80%, offers only modest improvement over bone scintigraphy alone. Presently, combined leukocyte/marrow imaging, with approximately 90% accuracy, is the radionuclide imaging procedure of choice for diagnosing prosthetic joint infection. In vivo leukocyte labeling techniques have shown promise for diagnosing musculoskeletal infection; their role in prosthetic joint infection has not been established. (111)In-labeled polyclonal immunoglobulin lacks specificity. (99m)Tc-ciprofloaxicin does not consistently differentiate infection from aseptic inflammation. (18)F-fluorodeoxyglucose positron emission tomography has been extensively investigated; its value in the diagnosis of prosthetic joint infection is debatable.

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 (99m)Tc-HMPAO or with (111)In-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.

Value of preoperative investigations in diagnosing prosthetic joint infection: retrospective cohort study and literature review

The diagnosis of a prosthetic joint infection is difficult, but crucial for appropriate treatment. Scintigraphy with specific markers for infection (labelled white cells or immunoglobulin-G) has been reported as a more reliable diagnostic tool than clinical assessment (fever, fistula), laboratory studies (polynuclear neutrophil count, erythrocyte rate sedimentation, and C-reactive protein), and preoperative aspiration. In the first part of this study, we retrospectively reviewed 230 patients admitted with a suspected prosthetic joint infection, and examined the validity of the different diagnostic tools for the group as a whole and for subgroups according to the Coventry classification. In the second part, we reviewed 35 articles about preoperative evaluation of infection in prosthetic joints and compared them to our findings. Our study indicates that C-reactive protein and joint aspiration are the most useful tools to diagnose prosthetic joint infection even in situations of chronic infection (Coventry type II).

Imaging orthopedic hardware with an emphasis on hip prostheses

This article reviews contemporary evaluation of hip prostheses, emphasizing both the accepted use of conventional radiographs, arthrograms, and scintigraphy, as well as the evolving use of CT and MR imaging in evaluating suspected complications. Developments in CT postprocessing and MR pulse sequence design now allow successful imaging of soft tissues adjacent to hardware components.

Radionuclide imaging in orthopedic infections

In otherwise normal bone, Three Phase Bone Scintigraphy is sensitive and specific for osteomyelitis. In patients with underlying osseous abnormalities the specificity of the study is decreased. The four phase bone scan, bone/gallium scintigraphy, leukocyte imaging, leukocyte/bone and leukocyte/marrow studies have all been reported to increase specificity. The techniques, strategies, and limitations are discussed. No single study is equally useful in all situations. Labeled leukocyte imaging is of little value in vertebral osteomyelitis because this entity often presents as a nonspecific photopenic defect. The preferred technique for the spine is bone/gallium imaging. Intense uptake, on bone scintigraphy, in two adjacent vertebrae with loss of the disc space is highly suggestive of spinal osteomyelitis. Gallium not only enhances the specificity of the diagnosis but provides information about surrounding soft tissue infection. In the diabetic foot, labeled leukocyte imaging alone is sufficient to determine the presence of osteomyelitis in the fore--foot. In the midfoot and hindfoot it may be necessary to combine leukocyte scintigraphy with bone scintigraphy to precisely localize the infection. Labeled leukocytes accumulate in the uninfected neuropathic joint and preliminary data suggest that leukocyte/marrow imaging may be useful to determine the significance of such uptake. For the painful joint replacement, if infection is the primary concern, leukocyte/marrow scintigraphy should be performed initially. If any postoperative complication, regardless of type, is the concern, it is reasonable to begin with bone scintigraphy because a normal study rules strongly against any complication. An abnormal bone scan will require additional studies to more precisely determine the cause of that abnormality.

Technetium-99m hexamethylpropylene amine oxime leucocyte scintigraphy for the diagnosis of bone and joint infections: a retrospective study in 116 patients

The aim of this study was to evaluate the diagnostic value of technetium-99m hexamethylpropylene amine oxime leucocyte scintigraphy (HMPAO-LS) by means of a retrospective review of 116 patients divided into three groups of bone and joint infection. One hundred and thirty-one LS examinations were performed, and 143 sites analysed. The final diagnosis of infection was based on surgical, histological and bacteriological data and follow-up. Ninety-four suspected localizations were examined in group 1, which included 74 patients with an infection suspected to involve orthopaedic implants. In this group, there were 38 true-positives, 1 false-negative, 49 true-negatives and 6 false-positives. Surgical confirmation was obtained in 34 cases. In group 2 (24 patients with suspected osteomyelitis), there were 27 localizations of which 14 were true-positives and 13 were true-negatives (including seven surgical confirmations). In group 3 (18 patients suspected of septic arthritis) there were eight true-positives, two false-negatives, ten true-negatives and two false-positives. Overall sensitivity of 99mTc-HMPAO-LS for the detection of bone and joint infection was 95%, with a specificity of 90% (group 1: sensitivity 97%, specificity 89%; group 2: 100% and 100%; group 3: 80% and 83%). It may be concluded that HMPAO-LS is an effective tool for the diagnosis of both bone infection involving implants and chronic osteomyelitis.

Radionuclide imaging after skeletal interventional procedures

Although nuclear medicine is often used as an adjunct to planning skeletal therapeutic interventions, its role in the assessment of these various interventional procedures, after the fact, is equally important. Skeletal therapeutic interventions studied with radionuclide imaging include bone grafts, the postoperative spine, and joint replacements. Vascularized bone grafts allow the successful reconstruction of large bone gaps. Early detection of vascular compromise permits prompt reevaluation of the vascular anastomosis so that potentially reversible causes of ischemia can be corrected. Radionuclide bone scintigraphy is a simple noninvasive method to evaluate the anastomotic patency of these grafts. Scintigraphically, vascular patency is characterized by normal or diffusely increased tracer uptake throughout the graft, whereas failure of the graft presents as photopenia. Bone scintigraphy, especially single photon emission computed tomography (SPECT), is of considerable value in the work-up of patients with persistent back pain after spinal surgery. Postoperatively, spinal fusion is characterized by diffusely increased uptake of radiotracer in the fused area. In contrast, focally increased uptake has been shown to be related to bony nonunion or pseudoarthroses. In patients who have undergone laminectomy, SPECT bone scintigraphy can localize the level of maximum instability and vertebral stress. The radionuclide evaluation of joint replacement complications, especially of hip and knee prostheses, has been extensively studied for nearly 2 decades. Bone scintigraphy is probably most useful when the images are normal. Although periprosthetic sites of increased uptake may be indicative of postoperative problems such as loosening or infection, they may also merely reflect postoperative changes. Dual tracer studies, focusing primarily on the diagnosis of the infected joint replacement, have consequently become the norm. Bone-gallium scintigraphy was the earliest dual tracer modality used, with an accuracy of 60% to 80%. The current radionuclide study of choice for diagnosing the infected prosthesis is labeled leukocyte-marrow imaging. Both leukocytes and colloid tracers accumulate in marrow, whereas only leukocytes accumulate in infection. This technique facilitates the discrimination of labeled leukocyte uptake in aberrant, but not abnormal, marrow from uptake in infection. The reported accuracy of this technique consistently exceeds 90%.

Investigation of joint disease

The role of nuclear medicine in the diagnosis and management of the major arthropathies is critically reviewed, with particular reference to osteoarthritis, rheumatoid and similar forms of arthritis, ankylosing spondylitis, non-specific back pain, gout, the neuropathic joint, avascular necrosis, infection and the consequences of prosthetic joint insertion. Attention is drawn both to practical applications and deficiencies in current techniques and knowledge.

Scintigraphic abnormalities in patients with painful hip replacements treated conservatively

A retrospective review of the scintigraphic appearances of 98 painful hip replacements was made. 16 patients (16%) underwent revision surgery whereas in the remaining 82 hips (84%), symptoms settled with conservative management. 73 of these (89%) had at least one area of increased activity on delayed diphosphonate scintigraphy with 27% having increased activity in three or more areas around the femoral component. Hips with increased activity at the lesser trochanter and tip were less likely to undergo spontaneous resolution of symptoms. Uncemented prostheses were more likely to have multiple areas of increased activity. Abnormalities in dynamic bone scintigraphy and gallium studies were also seen in patients whose symptoms resolved without surgery. Whereas a normal bone scintigram indicates that loosening or infection is most unlikely, the presence of increased activity does not necessarily indicate a need for revision surgery, even when multiple areas are present. A period of conservative management should be considered before operative intervention is undertaken.

The role of 99Tcm-HMPAO white cell imaging in suspected orthopaedic infection

Accurate diagnosis is essential for the effective management of suspected bone infection. Current imaging techniques have had limited success and further work is required. Although white cell labelling techniques have been available for many years the radiopharmaceuticals employed have disadvantages, particularly in their availability and suitability for imaging. These problems have been overcome by the use of 99Tcm-HMPAO as an in vitro leukocyte labelling agent. The aims of this study were to assess retrospectively its role and accuracy in imaging orthopaedic infection and to compare the results with three-phase bone imaging. 30 patients with suspected bone infection underwent three-phase methylene diphosphonate (MDP) bone imaging and labelled leukocyte imaging on separate occasions. 16 bone scans were positive for infection, of which 14 were subsequently confirmed, and there were no false negatives. There were no false positive white cell studies and only one infection was not identified. 99Tcm-HMPAO white cell imaging has been shown to be an accurate technique for the diagnosis of bone infection but should be performed only following a positive finding on three-phase bone scanning, since the latter is highly sensitive but significantly less expensive, making it a more appropriate screening procedure.

Tc-99m-MDP scintigraphy not informative in painful total hip arthroplasty

In 61 painful cemented total hip arthroplasties the diagnostic specificity was 0.7 for plain radiography and 0.46 for scintigraphy. The diagnostic sensitivity was 0.97 for radiography and 0.77 for scintigraphy. False negative radiology occurred in 0.05 and false positive in 0.23. False negative scintigraphy was encountered in 0.27 and false positive in 0.49. Seven of thirty-nine hips were operatively explored because of false positive scintigraphy. In conclusion, Tc-99m-MDP scintigraphy could not used as a complementary diagnostic measure in our hands.

The value of indium-labelled leucocytes in clinical practice

Following intravenous injection, autologous 111In labelled-leucocytes migrate to sites of inflammation, where they can be imaged with the gamma camera. The principle underlining the labelling technique is exposure of a population of leucocytes or purified granulocytes to a lipophilic 111In complex, such as 111In oxine or 111In tropolonate. As a result of cell activation, the in vitro manipulation to which the leucocytes are subjected modifies their biodistribution early after re-injection. Separation and labelling in plasma-enriched media, however, limits this activation and promotes early migration into inflammatory foci.