99mTc-PP and 67Ga imaging following insertion of orthopedic devices

Nuclear Medicine for the Orthopedic Foot and Ankle Surgeon

Nuclear medicine has been widely applied as a diagnostic tool for orthopedic foot and ankle pathology. Although its indications have diminished with improvements in and the availability of magnetic resonance imaging, nuclear medicine still has a significant and valuable role. The present article offers a comprehensive and current review of the most common nuclear imaging modalities for the orthopedic foot and ankle surgeon. Methods discussed include bone scintigraphy, gallium citrate scintigraphy, labeled-leukocyte scintigraphy, and single-photon emission computed tomography (SPECT). We review the indications and utility of these techniques as they pertain to specific foot and ankle conditions, including osteomyelitis, stress fractures, talar osteochondral lesions, complex regional pain syndrome, oncology, plantar fasciitis, and the painful total ankle arthroplasty. We conclude with a discussion of our approach to nuclear medicine with illustrative cases. Level of Evidence: Level V, expert opinion.

Bone scan in painful knee arthroplasty: obsolete or actual examination?

ptic loosening, instability and infection are the major causes of TKA failure. For many years, nuclear medicine (NM) imaging was helpful to frame a painful total joint arthroplasty. The differentiation of septic from aseptic prosthetic loosening is critical. The latest AAOS guidelines to detect periprosthetic joint infection (PJI) restrict the role of NM scintigraphy. On the other hand, several studies suggest that NM imaging plays an important role in the evaluation of patients with painful prosthesis, but its specificity in differentiating aseptic loosening from infection is low. Moreover, scintigraphic exams showed different diagnostic accuracy in TKA compared to total hip arthroplasty (THA).

PURPOSE

To assess and discuss current knowledges about the diagnostic value of the various scans in TKA failure alone.

METHODS

We perform a pubmed/medline search to identify all papers published in the literature matching the following key words: "total knee arthroplasty", "bone", "scintigraphy", "imaging", "three-phase", "triple-phase", "99mTc-HDP", "99mTc-MDP", "99mTc-hydroxymethane diphosphonate", and "99m Tc-methylenediphosphonate", "leukocyte scanning", "labeled leukocyte scintigraphy", "antigranulocyte", "nuclear medicine", "septic loosening", "aseptic loosening" and "infection".

RESULTS

Three phases bone scintigraphy results an early diagnostic screening test or part of the preoperative tests for painful TKA and when PJI is suspected. Instead, leukocyte/bone marrow scintigraphy is superior to other scintigraphic tools in diagnosis of TKA infections. Granulocyte scintigraphy, seems to be an excellent choice when the diagnosis is unclear. Moreover, nuclear diagnostic tests showed different diagnostic accuracy between TKA and THA.

CONCLUSIONS

Although nuclear diagnostic tests for THA failure are superior in  diagnostic accuracy compared to TKA, NM scintigraphy is still an effective tool in the identification of chronic, low grade PJI. To date, scintigraphic exams have an higher levels of sensitivity, specificity and accuracy. Currently, leukocyte/bone marrow scintigraphy is considered the gold standard for this aim.  Nevertheless, further studies are needed to assess and improve the accuracy of the scintigraphic exams in order to discriminate the causes of failure for painful TKA.

Does 99mTc-MDP bone scintigraphy add to the investigation of patients with symptomatic unicompartmental knee replacement?

AIM

The purpose of this study was to determine whether nuclear medicine (99m)Tc-Methyl diphosphonate bone scintigraphy ((99m)Tc-MDP bone scintigraphy) added information over plain radiographs loosening infection in symptomatic unicompartmental knee replacements (UKRs).

METHODS AND MATERIALS

A cohort of 39 patients who presented with knee pain following UKR was retrospectively reviewed. All had undergone nuclear medicine bone scans for possible loosening or infection of the prosthesis. The findings of the bone scintigraphy were compared to subsequent operative findings during diagnostic arthroscopic investigation or revision surgery for those patients who had undergone these procedures.

RESULTS

Of the 39 patients with painful knees following UKR, surgical findings confirmed that 11 had either loose (n=9) or infected (n=2) implants. Logistic regression analysis demonstrated no statistically significant combination of features on nuclear medicine or radiographs associated with failure of the prosthesis due to infection or loosening (p>0.05). Classification of a satisfactory position of the UKR on plain radiography exhibited a high negative predictive value (96% for infections, and 80% for loosening). However, plain radiograph was not sensitive for loosening (50%) or infection (37%) of the UKR with very low positive predictive values (9.1% for infection and 27.3% for loosening).

CONCLUSION

This study provides no evidence to support the routine use of (99m)Tc-MDP bone scintigraphy in the clinical decision-making for patients with a painful UKR.

LEVEL OF EVIDENCE

level 4.

Prosthetic joint infections: radionuclide state-of-the-art imaging

Prosthetic joint replacement surgery is performed with increasing frequency. Overall the incidence of prosthetic joint infection (PJI) and subsequently prosthesis revision failure is estimated to be between 1 and 3%. Differentiating infection from aseptic mechanical loosening, which is the most common cause of prosthetic failure, is especially important because of different types of therapeutic management. Despite a thorough patient history, physical examination, multiple diagnostic tests and complex algorithms, differentiating PJI from aseptic loosening remains challenging. Among imaging modalities, radiographs are neither sensitive nor specific and cross-sectional imaging techniques, such as computed tomography and magnetic resonance imaging, are limited by hardware-induced artefacts. Radionuclide imaging reflects functional rather than anatomical changes and is not hampered by the presence of a metallic joint prosthesis. As a result scintigraphy is currently the modality of choice in the investigation of suspected PJI. Unfortunately, there is no true consensus about the gold standard technique since there are several drawbacks and limitations inherent to each modality. Bone scintigraphy (BS) is sensitive for identifying the failed joint replacement, but cannot differentiate between infection and aseptic loosening. Combined bone/gallium scintigraphy (BS/GS) offers modest improvement over BS alone for diagnosing PJI. However, due to a number of drawbacks, BS/GS has generally been superseded by other techniques but it still may have a role in neutropenic patients. Radiolabelled leucocyte scintigraphy remains the gold standard technique for diagnosing neutrophil-mediated processes. It seems to be that combined in vitro labelled leucocyte/bone marrow scintigraphy (LS/BMS), with an accuracy of about 90%, is currently the imaging modality of choice for diagnosing PJI. There are, however, significant limitations using in vitro labelled leucocytes and considerable effort has been devoted to developing alternative radiotracers, such as radiolabelled HIGs, liposomes, antigranulocyte antibodies and fragments, as well as more investigational tracers such as radiolabelled antibiotics, antimicrobial peptides, bacteriophages and thymidine kinase. On the other hand, positron emission tomography (PET) is still growing in the field of PJI imaging with radiotracers such as (18)F-fluorodeoxyglucose (FDG), (18)F-FDG white blood cells and (18)F-fluoride. But unfortunately this superb tomographic technique will only receive full acceptance when specific PET uptake patterns can be successfully developed. The emergence of hybrid modality imaging using integrated single photon emission computed tomography (SPECT) and PET with computed tomography (SPECT/CT and PET/CT) may also have a contributing role for more accurate assessment of joint replacement complications, especially combined with new radiotracers such as (68)Ga and (64)Cu. Finally, in searching for infection-specific tracers, currently there is no such diagnostic agent available.

Evaluation of patients with a painful total knee replacement

Evaluation of patients with painful total knee replacement requires a thorough clinical examination and relevant investigations in order to reach a diagnosis. Awareness of the common and uncommon problems leading to painful total knee replacement is useful in the diagnostic approach. This review article aims to act as a guide to the evaluation of patients with painful total knee replacement.

Added value of SPECT/CT in patients suspected of having bone infection: preliminary results

AIM

We evaluated the contribution of SPECT/CT as an adjunct to combined three-phase bone scintigraphy (planar and SPECT) for diagnosing and localizing bone infection. Subsequently, the diagnostic performance of SPECT/CT was compared to visual fusion of SPECT with data of additional CT, X-ray, or MRI studies (SPECT + CT/X-ray/MRI).

MATERIALS AND METHODS

Thirty-one patients suspected of bone infection, presenting pathological findings on triple-phase bone scintigraphy, underwent additional SPECT/CT. The SPECT/CT-technology combines the acquisition of SPECT and CT data with the same imaging device enabling perfect overlay of anatomical and functional images. (99m)Tc-DPD was used as radiopharmaceutical in all patients. For data analysis findings of bone scintigraphy (planar scans as well as SPECT) were categorized as positive, negative, or equivocal for the presence of osteomyelitis. In a second step, they were compared with SPECT/CT and SPECT + CT/X-ray/MRI with respect to localization and classification of lesions. Validation was achieved by surgery, biopsy, or by clinical follow up over at least 9 months including microbiological and radiological findings.

RESULTS

Three-phase bone scan (incl. SPECT) correctly classified 7 lesions as positive and 11 lesions as negative for osteomyelitis. Six scans were interpreted false positive, two false negative, and five as equivocal. Rating the latter as positive for osteomyelitis, sensitivity of bone scan was (78%), specificity (50%). SPECT/CT was true positive in 7 patients, and true negative in 19. There were two false positive and two false negative findings, one scan was equivocal (sensitivity 78%, specificity 86%). Definition of anatomical localization of inflammatory foci was much easier by SPECT/CT due to better depiction of underlying anatomical details. SPECT + CT/X-ray/MRI yielded the highest sensitivity (100% compared to 78% of SPECT/CT), if equivocal findings (5/31 compared to 1/31 for SPECT/CT) are rated as true positive for osteomyelitis. Among radiological techniques, MRI (2 x FP) and CT (2 x FN) proved equal and expectedly superior to X-ray in delivering the correct diagnosis.

CONCLUSION

SPECT/CT improves the diagnostic performance of three-phase bone scan for osteomyelitis by avoiding false positive or equivocal results. An additional benefit over visual fusion of SPECT with X-ray, CT, or MRI studies could not be confirmed in our study.

Use of scintigraphy for assessment of fracture healing and early diagnosis of osteomyelitis following fracture repair in rabbits

OBJECTIVE

To evaluate use of technetium Tc 99m disodium hydroxymethylene diphosphonate (99m-Tc-HDP) for assessing fracture healing and 99m-Tc-HDP and technetium Tc 99m ciprofloxacin (99m-Tc-CIPRO) for early diagnosis of osteomyelitis in rabbits.

ANIMALS

32 skeletally mature New Zealand White rabbits.

PROCEDURE

A femoral fracture defect stabilized with bone plates and cortical screws was used. Scintigraphy was performed 4, 8, 12, and 16 weeks after surgery. The 99m-Tc-CIPRO scan was performed 48 hours after the 99m-Tc-HDP scan. The uptake ratio of the experimental limb to the normal limb was calculated by use of multiple regions of interest. Results of radiography performed to determine external callus and lysis grade and percentage defect ossification at 16 weeks were compared with scintigraphy results.

RESULTS

Infected fractures had a higher uptake ratio for 99m-Tc-HDP and 99m-Tc-CIPRO than noninfected fractures. Infected fractures could be differentiated from noninfected fractures late in healing by use of 99m-Tc-HDP. Although 99m-Tc-CIPRO was better than 99m-Tc-HDP for identifying infection, there was a high incidence of false positive and negative results with 99m-Tc-CIPRO. There was an association between 99m-Tc-HDP uptake ratio and callus formation and a good correlation between 99m-Tc-HDP uptake ratio and defect ossification after 4 weeks.

CONCLUSIONS AND CLINICAL RELEVANCE

99m-Tc-HDP and 99m-Tc-CIPRO may be useful for diagnosing osteomyelitis late in fracture healing; however, false positive and false negative results occur. Technetium Tc 99m disodium hydroxymethylene diphosphonate may be useful for evaluating fracture healing.

Acute septic arthritis

Acute septic arthritis may develop as a result of hematogenous seeding, direct introduction, or extension from a contiguous focus of infection. The pathogenesis of acute septic arthritis is multifactorial and depends on the interaction of the host immune response and the adherence factors, toxins, and immunoavoidance strategies of the invading pathogen. Neisseria gonorrhoeae and Staphylococcus aureus are used in discussing the host-pathogen interaction in the pathogenesis of acute septic arthritis. While diagnosis rests on isolation of the bacterial species from synovial fluid samples, patient history, clinical presentation, laboratory findings, and imaging studies are also important. Acute nongonococcal septic arthritis is a medical emergency that can lead to significant morbidity and mortality. Therefore, prompt recognition, rapid and aggressive antimicrobial therapy, and surgical treatment are critical to ensuring a good prognosis. Even with prompt diagnosis and treatment, high mortality and morbidity rates still occur. In contrast, gonococcal arthritis is often successfully treated with antimicrobial therapy alone and demonstrates a very low rate of complications and an excellent prognosis for full return of normal joint function. In the case of prosthetic joint infections, the hardware must be eventually removed by a two-stage revision in order to cure the infection.

[Chronic infections multifocal osteomyelitis vs chronic recurrent multifocal osteomyelitis: with reference to one case]

We present a rare case of chronic infectious multifocal osteomyelitis with affectation symmetric in the both femures in a patient with spondyarthropathic secondary Inflammatory Bowel Disease. The diagnosis was confirmed with culture of the bone biopsy. The aim of this work is the revision of the Chronic Infectious Multifocal Osteomyelitis and the Chronic Recurrent Multifocal Osteomyelitis into SAPHO syndrome that both were the possibilities diagnoses.

[Atypical findings of the combined scintigraphy of bone marrow and labeled leukocytes in osteonecrosis of the hip secondary to infection]

Avascular osteonecrosis can be associated with septic arthritis and osteomyelitis. Combined labeled leukocyte-marrow imaging scintigraphy has demonstrated excellent accuracy for the detection of infection since both tracers accumulate in the bone marrow and only leukocytes accumulate in infection. We report an unusual total absence of 99mTc HMPAO leukocytes/9mTc-sulfur colloid tracer accumulation, not only in the femoral head but also in the acetabulum and hip in hip osteonecrosis secondary to septic arthritis and osteomyelitis.

Diagnosis of infection after total hip arthroplasty

Forty-eight total hip arthroplasties for which revision surgery was performed were reviewed to determine the accuracy of laboratory tests, plain radiographs, hip aspiration, and technetium-99m MDP and gallium-67 scans in demonstrating the presence or absence of infection of the prosthesis. Six of the 48 hips were diagnosed as having an infection at the revision surgery. The erythrocyte sedimentation rate and the C-reactive protein levels were significantly higher in the patients with infected prostheses. The difference in the white blood cell count was not significant. There was no significant relationship between the presence of infection and the severity of loosening and instability of the implants diagnosed by plain radiographs. The accuracy of hip aspiration in diagnosing the infection was 83%, with a sensitivity of 40% and a specificity of 92%. The accuracy of technetium-99m MDP bone scan was 79%, with a sensitivity of 83%, and a specificity of 79%. Gallium-67 scan had an accuracy of 96%, a sensitivity of 67%, and a specificity of 100%. The findings in the present study indicated that diagnostic tests consisting of laboratory tests and plain radiography, followed by hip aspiration and sequential use of technetium-99m MDP and gallium-67 scintigraphies, are suitable for differentiation between mechanical loosening and infection of total hip arthroplasty.

Indium-111 leukocyte scintigraphic detection of subclinical osteomyelitis complicating delayed and nonunion long bone fractures: a prospective study

Twenty patients were studied prospectively with indium-labeled leukocyte imaging to evaluate its effectiveness in differentiating noninfected delayed or nonunion from osteomyelitis complicating these entities. All patients underwent an open surgical procedure within 24 h of the scan. Bone specimens from the nonunion site were obtained for microbiological and histological analysis to confirm the presence or absence of osteomyelitis. In these twenty patients, the sensitivity of the indium scintigraphy was 100%, the specificity 100%, and the overall accuracy 100%. Indium-labeled leukocyte scintigraphy is significantly more accurate than 99mtechnetium and 67gallium imaging had been, when studied earlier, in detecting subclinical osteomyelitis complicating nonunion. Indium-labeled leukocyte scintigraphy should supplant sequential technetium and gallium studies in this patient population when the surgeon must determine whether subclinical osteomyelitis is complicating fracture management of delayed and nonunions.

Role of scintigraphy in musculoskeletal and spinal infections

Clinical findings are still the mainstay for suspecting the diagnosis of musculoskeletal infections, especially osteomyelitis. No single complementary imaging technique has 100% specificity and sensitivity for every case of musculoskeletal infection. Depending on the age of the patient, presence of orthopedic hardware, location of infection, underlying bone, and systemic conditions, the choice of imaging modalities must be tailored to the patient's condition. Plain radiographs are performed first and may be sufficient. In children, bone scan is highly accurate to diagnose osteomyelitis. Labeled leukocytes with complementary bone or bone marrow studies are recommended for orthopedic hardware or diabetic foot. Finally, gallium scanning is useful for the diagnosis of vertebral osteomyelitis. Current radiopharmaceuticals used for diagnosing infection also label inflammation. Newer products, as Infecton, should in the future allow better differentiation between infection and sterile inflammation.

Sequential indium-labeled leukocyte and bone scans to diagnose prosthetic joint infection

Previous studies suggest that sequential technetium-99-hydroxymethyl diphosphonate bone scanning and indium-111 leukocyte scintigraphy may play a role during revision arthroplasty. Preoperative sequential imaging was compared with joint aspiration and clinical assessment during revision knee or hip arthroplasty. Scans were considered positive if indium-111 leukocyte uptake was incongruent or focally more intense than that of technetium-99-hydroxymethyl diphosphonate uptake. Of 166 cases, 22 were infected. Sequential technetium-99-hydroxymethyl diphosphonate and indium-111 leukocyte imaging was 64% sensitive and 78% specific. Fever, physical findings, or sedimentation rate did not identify infection reliably, and preoperative aspirate culture was only 28% sensitive. Positive scintigraphy increased the likelihood of finding infection intraoperatively from 14% to 30%, although negative scintigraphy decreased this likelihood to 7%. Based on the current study, the routine use of sequential technetium-99-hydroxymethyl diphosphonate and indium-111 leukocyte imaging cannot be advocated for differentiating occult infection from mechanical failure in painful, loose total joint arthroplasties.

67Ga-citrate and 99Tcm-MDP for estimating the severity of vertebral osteomyelitis

The aim of this study was to evaluate the roles of 67Ga-citrate and 99Tcm-methylene diphosphonate (99Tcm-MDP) planar and single photon emission tomographic (SPET) imaging in patients with vertebral osteomyelitis. Thirty patients (22 females, 8 males) aged 62.7 +/- 16.4 years (mean +/- s) were enrolled prospectively between May 1995 and May 1998. The patients had been on antibiotics for 7 +/- 4 weeks prior to the study. Histology was available for all but nine patients with mild infections, who were evaluated by a combination of magnetic resonance imaging (MRI), clinical and laboratory tests. 67Ga-citrate (185 MBq) and three-phase bone (555 MBq 99Tcm-MDP) planar and SPET imaging were performed in all patients, together with MRI as a comparison. In total, 67 infectious foci were detected. Based on histology, there were four cases of severe, 13 cases of moderate and four cases of mild osteomyelitis; nine mild infections were also classified by the combination of MRI, clinical and laboratory results. Combined MRI and 67Ga-citrate SPET correctly classified all patients; MRI detected all 67 infectious foci, whereas 67Ga-citrate SPET identified 54 only. False-negative results were seen with all other modalities, especially in cases of mild and moderate infection. 67Ga-citrate SPET identified unsuspected cases of endocarditis (n = 2), paravertebral abscess (n = 1), subaxillary soft tissue abscess (n = 1) and rib osteomyelitis (n = 1). For 67Ga-citrate SPET, the target-to-background ratio was 2.24 +/- 0.31, 1.76 +/- 0.07 and 1.30 +/- 0.18 for severe, moderate and mild osteomyelitis, respectively. Significant differences were noted between severe and moderate infection (P = 0.0051) and between severe and mild infection (P < 0.0001); that between moderate and mild infection was non-significant. For 99Tcm-MDP planar and SPET imaging, and for planar 67Ga-citrate imaging, there was no correlation with severity. We conclude that 67Ga-citrate SPET is able to identify vertebral osteomyelitis and detect additional sites of infection. It can also aid in determining the severity of infection and, potentially, the response to therapy.

Clinical, radiographic, and scintigraphic comparison of the mechanical stability of Mueller and Zweymueller total hip prostheses

Twenty-two cemented Mueller and 25 uncemented Zweymueller total hip arthroplasties (THAs) were performed in the same period in 47 consecutive randomly selected patients with unilateral primary osteoarthritis. Patients were evaluated using the same clinical and radiographic protocol preoperatively; 3, 6, and 12 months postoperatively; and annually thereafter as well as with Tc 99m MDP three-phase bone scintigraphy 3, 6, 12, and 24 months postoperatively. At 11 periprosthetic regions of interest (ROIs) around the stem and socket of each prosthesis, several radiographic parameters and bone scintigram uptake grade were recorded and correlated to determine the significance of early scintigraphic uptake for prediction of the stability of cemented and uncemented THA components over time. Around stable Zweymueller and Mueller sockets, the radionuclide uptake was similar during all periods of observation. Radionuclide uptake around stable Zweymueller stems was significantly more than around stable Mueller stems at the medial femoral cortex 3 and 6 months postoperatively, at the lateral femoral cortex 3-24 months postoperatively, and near the tip of the stem 3 months postoperatively. Radionuclide uptake around stable Mueller stems was significantly more than around Zweymueller stems at the greater trochanter 6 and 12 months postoperatively and at the lesser trochanter 12 months postoperatively. Any significant deviation of radionuclide uptake at any ROI, time, and THA component during the first 2 years postoperatively in combination with radiographic findings of loosening should be considered a serious predictive sign for loosening of a Mueller or Zweymueller THA component.

Scintigraphic evaluation in total knee failure secondary to severe metallosis

The scintigraphic findings are described for a patient with severe metallosis in a failed noninfected total knee arthroplasty secondary to metal-metal friction between the femoral and tibial components as a result of polyethylene wear. Technetium-99m phosphate and gallium-67 citrate scans were positive in incongruent uptake areas. This uptake is classically associated with septic loosening. The recommendation is made that metallosis be suspected before surgery as a possible cause of a false positive scan where sequential technetium-gallium scans are employed.

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.

Aseptic necrosis. A scintigraphic imitator of osseous involvement in Ga-67 avid lymphoma

Based on the data by Armas et al, avascular necrosis, a not uncommon treatment-associated complication in patients with lymphoma, it should be easily distinguishable from osseous lymphomatous involvement in patients with Ga-67 avid lymphoma. In avascular necrosis, Ga-67 uptake will be either absent, decreased, or normal, whereas in lymphoma Ga-67 uptake will be increased. The authors present a patient with Hodgkin's disease who had new foci of simultaneously increased Ga-67 and Tc-99m MDP uptake because of avascular necrosis as proven by biopsy and long-term follow-up. The authors hypothesize that a possible-explanation for the discrepancy between this patient report and the series by Armas et al may be that increased Ga-67 is a delayed phenomenon related to healing.

Complicated bone and soft-tissue infections. Imaging with 0.1 T MR and 99mTc-HMPAO-labeled leukocytes. ff

PURPOSE

To assess the value of imaging by 0.1 T MR and by 99mTc-HMPAO-labeled leukocytes in confirming skeletal infection in patients with soft-tissue infections and/or bone pathology.

METHODS

Thirty-nine anatomical sites (35 patients) with suspected bone infection were prospectively imaged with 0.1 T MR and 99mTc-HMPAO-labeled leukocytes. Thirty-two infected areas were confirmed: 12 osteomyelitis (out of which 3 were spondylitis) and 27 soft-tissue infections (both bone and soft-tissue infection in 7 areas).

RESULTS

MR imaging showed 31 true-positive, 3 true-negative, 4 false-positive and one false-negative diagnosis of infection and scintigraphy 27, 7, 0 and 5 respectively. The sensitivity of MR for osteomyelitis was 100% (12/12) and of scintigraphy 42% (5/12), p<0.01. The specificity of MR and of scintigraphy for osteomyelitis were 81% (22/27) and 93% (25/27) respectively. The sensitivity of MR for soft-tissue infection was 96% (26/27) and specificity 75% (9/12). The correspoding figures for scintigraphy were 85% (23/27) and 100% (12/12). MR and scintigraphy were concordant with respect to the final diagnosis in 28/39 (72%) sites and discordant in 10 (26%). In one patient with Charcot osteoarthropathy a false-positive finding was found by both methods. MR detected all 3 cases of spondylitis, scintigraphy none. Nonpyogenic inflammations and neuroarthropathic joints were indistinguishable from infection by MR.

CONCLUSION

Combined imaging with MR and 99mTc-labeled leukocytes is recommended in diagnostically complicated bone infections except for spondylitis where MR is the method of choice. Congruent positive findings are highly suggestive of infection, the extent of which can be determined. Congruent negative results exclude infection.

Isotope bone scans in patients with painful knee replacements: do they alter management?

A retrospective review of the scintigraphic appearances, clinical findings and outcome in 12 patients presenting with painful knee replacements was made. Three patients required revision surgery; symptoms in the remaining nine patients settled without operative management. Three examinations failed to identify prostheses proven to be infected by aspiration and four were falsely positive for infection without supportive clinical evidence. Four examinations demonstrated loosening and in one patient the bone scan was normal but the prostheses was loose at revision surgery. There were no specific features to predict which prostheses required surgical revision and the ability to diagnose or exclude infection was limited. It is concluded that the results of three phase 99Tcm bone scans in symptomatic knee prostheses are of little assistance in guiding clinical management and that a period of conservative management should be considered prior to operative intervention.

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%.

Quantitative bone scanning after asymptomatic Charnley arthroplasty

To establish the normal pattern of postoperative tracer uptake we performed 73 99mtechnetium methylene diphosphonate scans following primary Charnley hip replacements for arthrosis in 68 patients without clinical, hematological and radiographic complications. The patients were divided into 7 subgroups according to the period, 6-24 months, between surgery and scan. There were 10-12 patients in each subgroup. A high-resolution gamma camera with a large field of view was used. Ratios of uptake in each of 10 peri-prosthetic zones to normal bone were calculated. Femoral uptake was found to decrease in linear fashion from 6 to 12 months after surgery. Thereafter the uptake remained unaltered at levels nearly twice the normal ones in the greater trochanter and nearly 1.5 times in the lesser trochanter, returning to almost normal levels in other zones. Acetabular uptake remained elevated throughout.

The current role of gallium imaging in infection

The role of gallium imaging in infection has changed considerably during the past several years. Once the mainstay of radionuclide imaging of infection, it has been supplanted to a very great extent by labeled leukocyte imaging. Despite the success of the labeled white-cell technique, gallium still plays an important role in the radionuclide evaluation of infection. It is not possible, for a variety of reasons, to perform white-cell imaging on all patients, and gallium imaging is certainly an acceptable substitute. In certain circumstances, rather than merely being a substitute, gallium is an important complement to leukocyte imaging. This is best illustrated by the patient with a fever of unknown origin (FUO). Although a negative leukocyte study effectively excludes an acute infection, it fails to identify the source of the patient's fever, a not uncommon situation in view of the fact that only approximately 25% of all FUOs are caused by infection. A complementary gallium study under these circumstances may identify either a chronic infectious process or even a neoplasm, conditions for which white-cell imaging is relatively insensitive. Although leukocyte imaging is probably superior to gallium for most infections of the musculoskeletal system, this technique is of limited value in patients with suspected vertebral osteomyelitis. There are data that suggest that sequential bone gallium imaging may be a better way to diagnose this entity. Finally, in immunocompromised patients, gallium imaging is clearly the procedure of choice for detecting the opportunistic respiratory infections and lymph node abnormalities that are so prevalent in this population.

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.

Radionuclide imaging in osteomyelitis

The utility of bone imaging has remained significantly high despite the proven suboptimal specificity of the conventional three-phase bone scan. The quantitative four-phase study may play a role in maintaining its usefulness in the future. However, due to its extremely high sensitivity and excellent anatomical information, it remains as the first diagnostic study in most suspected cases of acute osteomyelitis. The future would see development of new imaging modalities aimed at enhancing the specificity for diagnosis of active osteomyelitis. The indium leucocyte study has been the single most important development in this respect in the last decade. NMR has been another important addition to complement the anatomical information for defining the extent and nature of infectious process--acute or chronic. It remains to be seen if the other investigative work on antigranulocyte antibodies or other imaging agents or techniques would make the future diagnosis of osteomyelitis more reliable and accurate using the nuclear medicine techniques.

Scintigraphy with Tc, Ga and In in painful total hip prostheses

A series of 40 patients were studied, who were operated upon for a painful total hip prosthesis, half of which were infected. In each case, preoperative scintigraphy was performed using Tc99, Ga67 and In111. The images obtained with Tc and Ga were compared with those of In111 and analysed with respect to sensitivity, specificity, accuracy and the predictive value of a positive or negative test. In111 had a predictive value of more than 90% and showed greater reliability in the diagnosis of an infection as the cause of a painful total hip prosthesis.

RM isoelastic total hip arthroplasty. A review of 34 cases

Thirty-four cases of RM isoelastic total hip arthroplasty were followed for an average period of 42 months after surgery. Eleven (32%) were revised because of purely mechanical loosening of the femoral stem. Of the remaining cases, 16 (69%) had poor Mayo hip scores and only 2 (9%) had good results. Radiologic evidence of loosening of the uncemented femoral stem, as exemplified by radiopaque lines within radiolucent zones, the so-called "pedestal sign" of increased density at the stem tip, and proximal bony overgrowth around the collar were present in all 11 cases that were revised. Marked stem shift and localized cortical hypertrophy were noted in nine revised cases. Radiopaque lines were observed in 11 nonrevised cases, all with poor Mayo hip scores.

Craniotomy flap osteomyelitis: a diagnostic approach

Nine cases of suspected craniotomy flap osteomyelitis evaluated by combined bone and gallium scanning are presented. In six cases, the clinical data were inconclusive and evaluation by radionuclide imaging provided an accurate negative diagnosis. The other three cases considered positive by this technique were proven infected at subsequent exploration and flap removal. The use of radionuclide bone and gallium imaging should be considered in cases of possible craniotomy flap osteomyelitis.

Definition of endoprosthetic loosening. Comparison of arthrography, scintigraphy and roentgen stereophotogrammetry in prosthetic hips

Contrast arthrography, radionuclide arthrography, scintigraphy and roentgen stereophotogrammetric analysis (RSA) were used to detect mechanical loosening in 14 painful total hip replacements. All prosthetic components unstable by RSA, or with abnormal arthrogram, or with increased scintigraphic activity, or loose at revision were migrating, but no non-migrating components demonstrated any of these signs of loosening. Our findings indicate that mechanical loosening should be defined as migration.

Sequential technetium-99m/gallium-67 scintigraphic evaluation of subclinical osteomyelitis complicating fracture nonunion

Twenty-four patients with a history of post-traumatic fracture nonunion underwent sequential 99mTc and 67Ga citrate scintigraphy in an attempt to differentiate between posttraumatic fracture nonunion and nonunion complicated by subclinical osteomyelitis. Neither technetium nor gallium studies alone nor in combination, with or without clinical correlation, could help delineate between fracture nonunion and nonunion complicated by subclinical osteomyelitis because of the increased technetium and gallium radioisotope uptake associated with the nonunion site.

The radiology of total hip replacement

The radiology of total hip replacement (THR) and its complication is reviewed in conjunction with a long-term follow-up study on 402 patients with 501 prostheses. The indications, contraindications, biomechanics, and operative management of these patients is discussed. Clinical complications such as deep vein thrombosis, pulmonary embolism, and hemorrhage are mentioned. Postoperative infections including granulomatous pseudotumors, dislocations and fractures, true loosening of the prosthesis, and heterotopic bone formation (HBF) are discussed and illustrated. The importance of differentiating the lucent line from true loosening is stressed. Mechanical and other clinical complications which are largely ignored by radiologists are also discussed. The uses of arthrography and bone scanning are included.

Scintigraphic evaluation of the painful prosthetic joint: a comparison of gallium-67 citrate and indium-111 labelled leucocyte imaging

The radiopharmaceuticals gallium-67 and indium-111 labelled leucocytes have been compared in 15 patients with a painful joint prosthesis in an attempt to identify those patients with periprosthetic infection. Gallium-67 images were abnormal in five out of six patients with periprosthetic infection and normal in seven out of nine without evidence of infection. Indium-111 leucocyte images were abnormal in three out of six patients with infection and normal in all nine patients without infection. Indium-111 labelled leucocyte imaging is technically more difficult to perform than gallium-67 imaging. This, combined with the higher sensitivity of gallium-67 imaging for infection around a prosthetic joint, leads us to conclude that gallium-67 imaging is superior to indium-111 leucocyte imaging in identifying infection as a cause of a painful prosthetic joint.

Group B streptococcal arthritis in adults

Group B streptococcal arthritis in adults is uncommon. This report describes seven cases seen at these institutions over the past five years and reviews the previous 17 documented cases. Of seven adults, three were diabetics, three had prosthetic hips, and one had undergone splenectomy. Six had undergone no prior dental, genitourinary, or gastrointestinal procedures. The most common clinical presentation was fever and acute joint pain. Five patients had monoarticular arthritis; two had multiple joint involvement. Underlying joint abnormalities included osteoarthritis (two), prosthetic hip (three), and neuropathic joint (one). Bacteremia was documented in three and suspected in the remaining four patients, often without a primary source. Therapy included parenteral antibiotics, usually penicillin G, and drainage of the involved joint. Two of three patients with prosthetic implants required Girdlestone procedures; the third was apparently cured. The three diabetic patients died, one with resolution of group B streptococcal arthritis. The seventh patient was cured. Group B streptococcal arthritis is a serious infection in adults with diabetes and late prosthetic hip infections.

Indium-111 leucocyte scanning in the evaluation of painful hip arthroplasty

Thirty patients with a painful hip arthroplasty had an In-111 leucocyte scan before surgical reexploration. In 12 patients, the In-111 leucocyte scan was abnormal and in all of them, microorganisms were found at the culture of the material from their hips at the operation. Among the 18 patients with a normal scan no infection was found in 17. In one patient, a thick-walled abscess growing Escherichia coli was found. We conclude that In-111 scanning is sensitive, specific and therefore useful in the differential diagnosis of pain after hip arthroplasty.

Bone scintigraphy in the diagnosis and management of traumatic injury

Imaging with bone-seeking nuclear medicine radiopharmaceuticals has changed dramatically in a span of 10 years. The only indication for bone scintigraphy a decade ago was to detect skeletal metastases in patients with known carcinoma. Improvements in equipment and radiopharmaceuticals have led to the use of nuclear medicine studies for the detection and evaluation of a multitude of benign abnormalities. This article discusses the use of bone-seeking radiopharmaceuticals in traumatic processes involving the skeletal system, connective tissues, and muscles. A review of the subject is included, as well as some new ideas regarding the interpretation and evaluation of scintigraphs with respect to trauma to the bones and soft tissues.

Gallium 67 scanning in rheumatoid arthritis

Gallium 67 scans were performed on both knees of 38 patients with rheumatoid arthritis. There was a significantly higher level of 67Ga accumulation in those knees with clinically active synovitis (p less than 0.001). Synovial white cell concentration was also elevated in the group with active synovitis. The white cell concentration correlated with the 67Ga knee/femoral ratio at the p less than 0.001 level. 67Ga activity in the synovial fluid was predominantly in the supinate and activity was also present in the synovium. The findings indicate that 67Ga uptake occurs in rheumatoid joints and reflects the degree of synovial inflammation.