Role of scintigraphy in musculoskeletal and spinal infections

Septic arthritis in children: frequency of coexisting unsuspected osteomyelitis and implications on imaging work-up and management

OBJECTIVE

Osteomyelitis and septic arthritis clinically present at any age with overlapping signs and symptoms. The purposes of this study were to evaluate the demographic distribution of septic arthritis and osteomyelitis in children and to explore optimal imaging guidelines for these patients.

MATERIALS AND METHODS

We performed a retrospective study of children up to 18 years old who were treated for osteomyelitis or septic arthritis between January 2011 and September 2013. All patients underwent MRI without previous intervention. Studies were reviewed to determine the incidence of septic arthritis or superimposed osteomyelitis. The reference diagnosis was based on the combined review by the orthopedic surgeon and infectious disease notes, discharge summary, operative report, and MRI examination.

RESULTS

One hundred sixty-two children who underwent 177 MRI examinations were diagnosed with acute musculoskeletal infection. One hundred three patients were included in the septic arthritis category, of whom 70 (68%) had septic arthritis with osteomyelitis. Seventy-four (42.1%) patients had isolated osteomyelitis without septic arthritis. Children under 2 years old were more likely to have septic arthritis (either isolated or with osteomyelitis) than isolated osteomyelitis compared with older children (p = 0.0003).

CONCLUSION

In children who underwent MRI for suspected musculoskeletal infection, septic arthritis was more prevalent in children under the age of 2 years than in older children. However, both septic arthritis and osteomyelitis were found frequently in older children. Musculoskeletal infection imaging workup guidelines for children of all ages should address the frequent association of osteomyelitis and septic arthritis. We recommend that MRI should be used in the evaluation of suspected musculoskeletal infections in children, and the nearest joint should always be included to evaluate the extent of articular disease.

Septic arthritis in immunocompetent and immunosuppressed hosts

Septic arthritis has long been considered an orthopedic emergency. Historically, Neisseria gonorrhoeae and Staphylococcus aureus have been the most common causes of septic arthritis worldwide but in the modern era of biological therapy and extensive use of prosthetic joint replacements, the spectrum of microbiological causes of septic arthritis has widened considerably. There are also new approaches to diagnosis but therapy remains a challenge, with a need for careful consideration of a combined medical and surgical approach in most cases.

Cervical osteomyelitis with thoracic myelitis and meningitis in a diabetic patient

A 45-year-old man with a history of untreated diabetes mellitus had a persisting fever, back pain, and diarrhea. The primary care physician diagnosed the patient with the flu and gastroenteritis. The patient developed paraplegia for two weeks and was admitted to another hospital. The physician in this hospital suspected infectious meningitis and myelitis, and administered piperacillin and steroids without cerebrospinal fluid (CSF) examination. On referral to our hospital, he presented a high fever and complete paraplegia. The lumbar puncture revealed a yellowish CSF, polynucleosis, and hypoglycorrhachia. Bacteria were not detected on Gram's staining and were not confirmed by CSF culture. Magnetic resonance imaging (MRI) showed no thoracolumbar lesion and suggested a cervical epidural abscess without any spinal cord compression. He was diagnosed as having osteomyelitis with meningitis and thoracic myelitis. The infection subsided with broad-spectrum antibiotics. After two weeks, bilateral sensorimotor disturbances of the upper extremities appeared. MRI findings showed the epidural abscess compressing the cervical spinal cord. We performed debridement of the epidural abscess. The infection was clinically controlled by using another antibiotic. One month after the infection subsided, a 360° reconstruction was performed. In this case, the misdiagnosis and the absence of CSF examination and culture to detect the pathogenic bacteria at an earlier stage in the patient's disease course might have led to the exacerbation of the pathology.

[Acute limping in children between 1 and 4 years old]

Recent limping in children aged between 1 and 4 years old are often a diagnostic problem because the young child may not be able to show the area of pain. Dominated by the traumatic causes like hairline fracture, the physician should eliminate the most severe, including infectious etiologies that require urgent treatment. The clinical examination is fundamental and simple complementary investigations like standard X-rays and biology (blood count cell, C reactive protein) looking for increased inflammatory parameters will help to find the cause in the majority of cases. The persistence of a limp beyond a week involves the realization of bone scan or MRI imaging.

Diagnosis of bone infection by complementary role of technetium-99m MDP and technetium-99m hexamethylpropylene-amineoxime-leukocytes

Purpose:

Valuate complementary role of ^99mTc-MDP bone scan and ^99mTechnetium hexamethylpropylene-amineoxime (^99mTc-HMPAO) labeled leukocyte scintigraphy in diagnosis of bone infection.

Patients and Methods:

Ninety one sites suspected to have bone infection were divided in to two groups: Group I 49 sites with current endo-prothesis; and group II 42 sites with no prosthesis. All patients were subjected to serial images of ^99mTc-HMPAO labeled leukocyte (^99mTc-white blood cells (WBCs)), triple phase bone scan (^99mTc-MDP) and plain X-ray, in addition to clinical and bacteriological assessment, together with follow-up.

Results:

The overall sensitivity (Sn) was found to be 34.9%, 95.4%, and 86% for plain X-ray, ^99mTc-MDP, and ^99mTc-WBCs respectively. Concerning specificity (Sp) was found to be 47.9%, 45.8%, and 91.7% respectively for the three imaging modalities. ^99mTc-WBCs showed better Sn, Sp, and accuracy in group I (95%, 93.1% and 93.9%, respectively) compared to 40%, 41.4%, and 40.8% for plain X-ray and 90%, 62%, and 73.5% respectively for ^99mTc-MDP. On the other hand, ^99mTc-MDP proved to have best Sn 100% versus 78.3% and 30.4% for ^99mTc-WBCs and plain X-ray respectively. Yet, Sp and accuracy was found to best for ^99mTc-WBCs (89.5% and 83.3% respectively) compared to 57.9% and 42.9% for plain X-ray and 21.1% and 64.3% for ^99mTc-MDP.

Conclusion:

Combined imaging with ^99mTc-WBCs and ^99mTc-MDP proved to be effective in early detection of bone infection in the presence or absence of prosthesis.

Central Nervous System Infections

Central nervous system (CNS) infections—i.e., infections involving the brain (cerebrum and cerebellum), spinal cord, optic nerves, and their covering membranes—are medical emergencies that are associated with substantial morbidity, mortality, or long-term sequelae that may have catastrophic implications for the quality of life of affected individuals. Acute CNS infections that warrant neurointensive care (ICU) admission fall broadly into three categories—meningitis, encephalitis, and abscesses—and generally result from blood-borne spread of the respective microorganisms. Other causes of CNS infections include head trauma resulting in fractures at the base of the skull or the cribriform plate that can lead to an opening between the CNS and the sinuses, mastoid, the middle ear, or the nasopharynx. Extrinsic contamination of the CNS can occur intraoperatively during neurosurgical procedures. Also, implanted medical devices or adjunct hardware (e.g., shunts, ventriculostomies, or external drainage tubes) and congenital malformations (e.g., spina bifida or sinus tracts) can become colonized and serve as sources or foci of infection. Viruses, such as rabies, herpes simplex virus, or polioviruses, can spread to the CNS via intraneural pathways resulting in encephalitis. If infection occurs at sites (e.g., middle ear or mastoid) contiguous with the CNS, infection may spread directly into the CNS causing brain abscesses; alternatively, the organism may reach the CNS indirectly via venous drainage or the sheaths of cranial and spinal nerves. Abscesses also may become localized in the subdural or epidural spaces. Meningitis results if bacteria spread directly from an abscess to the subarachnoid space. CNS abscesses may be a result of pyogenic meningitis or from septic emboli associated with endocarditis, lung abscess, or other serious purulent infections. Breaches of the blood–brain barrier (BBB) can result in CNS infections. Causes of such breaches include damage (e.g., microhemorrhage or necrosis of surrounding tissue) to the BBB; mechanical obstruction of microvessels by parasitized red blood cells, leukocytes, or platelets; overproduction of cytokines that degrade tight junction proteins; or microbe-specific interactions with the BBB that facilitate transcellular passage of the microorganism. The microorganisms that cause CNS infections include a wide range of bacteria, mycobacteria, yeasts, fungi, viruses, spirochaetes (e.g., neurosyphilis), and parasites (e.g., cerebral malaria and strongyloidiasis). The clinical picture of the various infections can be nonspecific or characterized by distinct, recognizable clinical syndromes. At some juncture, individuals with severe acute CNS infections require critical care management that warrants neuro-ICU admission. The implications for CNS infections are serious and complex and include the increased human and material resources necessary to manage very sick patients, the difficulties in triaging patients with vague or mild symptoms, and ascertaining the precise cause and degree of CNS involvement at the time of admission to the neuro-ICU. This chapter addresses a wide range of severe CNS infections that are better managed in the neuro-ICU. Topics covered include the medical epidemiology of the respective CNS infection; discussions of the relevant neuroanatomy and blood supply (essential for understanding the pathogenesis of CNS infections) and pathophysiology; symptoms and signs; diagnostic procedures, including essential neuroimaging studies; therapeutic options, including empirical therapy where indicated; and the perennial issue of the utility and effectiveness of steroid therapy for certain CNS infections. Finally, therapeutic options and alternatives are discussed, including the choices of antimicrobial agents best able to cross the BBB, supportive therapy, and prognosis.

[SPECT/CT diagnostics for skeletal infections]

CLINICAL/METHODICAL ISSUE

Skeletal infections are often a diagnostic and clinical challenge.

STANDARD RADIOLOGICAL METHODS

Nuclear imaging modalities used in the diagnostic workup of acute and chronic skeletal infections include three-phase bone scintigraphy and scintigraphy with labelled leucocytes.

METHODICAL INNOVATIONS

The introduction of hybrid technologies, such as single photon emission computed tomography/computed tomography (SPECT/CT) has dramatically changed nuclear medical imaging of infections.

PERFORMANCE

In general SPECT/CT leads to a considerably more accurate diagnosis than planar or SPECT imaging.

ACHIEVEMENTS

Given the integrated acquisition of metabolic, functional and morphological information, SPECT/CT has increased in particular the specificity of three-phase skeletal scanning and scintigraphy with labeled leucocytes.

Musculoskeletal disorders in the elderly

Musculoskeletal disorders are among the most common problems affecting the elderly. The resulting loss of mobility and physical independence can be particularly devastating in this population. The aim of this article is to present some of the most frequent musculoskeletal disorders of the elderly, such as fractures, osteoporosis, osteoarthritis, microcrystal disorders, infections, and tumors.

Percutaneous vertebral body cement augmentation for back pain related to occult osteomyelitis/diskitis

Although complications related to vertebroplasty or kyphoplasty are few, we treated 2 patients with vertebroplasty or kyphoplasty for pain, presumed to be due to vertebral compression fractures, which were subsequently found to be due to occult osteomyelitis/diskitis. The onset of their infections appeared to have preceded their vertebral body augmentation procedures and was possibly due to prior interventional procedures for histories of back pain.An 86-year-old woman had had 3 prior kyphoplasty procedures for fractures at T10, T11, and L1. She reported continued severe pain, and subsequent magnetic resonance imaging was misinterpreted for another fracture at T12, resulting in her fourth kyphoplasty. She became septic and had some improvement with antibiotics, but she declined specialty care and died. A 74-year-old man with chronic back pain had recently undergone lumbar facet joint injections. Computed tomography and subsequent bone scan found uptake at both L2 and L3. Despite abnormal erythrocyte sedimentation rate and C-reactive protein level and normal radiographic vertebral height, he underwent a vertebroplasty. His pain increased, and subsequent workup found L2-3 diskitis. He recovered with antibiotics and specialty care. Similar to prior reports of spondylodiskitis, both patients had multiple medical comorbidities.This article emphasizes the need for clinical reevaluation and scrutiny in the interpretation of imaging studies, including for infection in patients with continued pain after spinal procedures. The differential diagnosis of infectious etiology is an important consideration prior to vertebral cement augmentation for presumed fragility fracture.

Childhood osteomyelitis-incidence and differentiation from other acute onset musculoskeletal features in a population-based study

BACKGROUND

Osteomyelitis can be difficult to diagnose and there has previously not been a prospective approach to identify all children in a defined geographic area. The aim of this study was to assess the annual incidence of osteomyelitis in children, describe the patient and disease characteristics in those with acute (< 14 days disease duration) and subacute osteomyelitis (> or = 14 days disease duration), and differentiate osteomyelitis patients from those with other acute onset musculoskeletal features.

METHODS

In a population-based Norwegian study physicians were asked to refer all children with suspected osteomyelitis. Children with osteomyelitis received follow-up at six weeks, six months and thereafter as long as clinically needed.

RESULTS

The total annual incidence rate of osteomyelitis was 13 per 100,000 (acute osteomyelitis 8 and subacute osteomyelitis 5 per 100,000). The incidence was higher in patients under the age of 3 than in older children (OR 2.9, 95%: CI 2.3-3.7). The incidence of non-vertebral osteomyelitis was higher than the incidence of vertebral osteomyelitis (10 vs. 3 per 100 000; p = .002). Vertebral osteomyelitis was more frequent in girls than in boys (OR 7.0, 95%: CI 3.3-14.7). ESR > or = 40 mm/hr had the highest positive predictive laboratory value to identify osteomyelitis patients at 26% and MRI had a positive predictive value of 85%. Long-bone infection was found in 16 (43%) patients. ESR, CRP, white blood cell count, neutrophils and platelet count were higher for patients with acute osteomyelitis than for patients with subacute osteomyelitis. Subacute findings on MRI and doctor's delay were more common in subacute osteomyelitis than in acute osteomyelitis patients. Blood culture was positive in 26% of the acute osteomyelitis patients and was negative in all the subacute osteomyelitis patients.

CONCLUSION

The annual incidence of osteomyelitis in Norway remains high. ESR values and MRI scan may help to identify osteomyelitis patients and differentiate acute and subacute osteomyelitis.

Image-guided musculoskeletal biopsy

Image guidance allows safe passage of needles, often into small and otherwise inaccessible lesions, and into the portions of the lesion most likely to yield useful samples, while avoiding damage to important structures. This article hopes to provide a useful guide to image-guided musculoskeletal biopsy for radiologists in practice and in training.

99mTc-HMPAO labelled white blood cell scintigraphy in patients with osteoarticular infection: the value of late images for diagnostic accuracy and interobserver reproducibility

The objectives of this study were to evaluate the diagnostic value of 99mTc-HMPAO labelled white blood cell scintigraphy (WBCS) in patients with suspected osteomyelitis using late images and to study interobserver reproducibility. This study prospectively included 120 patients, and after a follow-up of one year, only 70 patients (n = 49 with implants, n = 21 without implants) were selected. The final diagnosis of infection was based either on microbiological data (n = 54) or follow-up (n = 16). We performed WBCS with 4 h and 24 h scans. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 77%, 72%, 83%, 64%, and 75% at 4 h, and 74%, 87%, 91%, 59%, and 79% at 24 h, respectively. The interobserver reproducibility shows a 63% prevalence of agreement between results (kappa = 0.5) at 4 h and 80% (kappa = 0.74) at 24 h, respectively. WBCS with 24-h images improves specificity and interobserver reproducibility in patients with suspected osteoarticular sepsis.

Nuclear medicine imaging of bone infections

The inflammation and infection of bone include a wide range of processes that can result in a reduction of function or in the complete inability of patients. Apart from the inflammation, infection is sustained by pyogenic microorganisms and results mostly in massive destruction of bones and joints. The treatment of osteomyelitis requires long and expensive medical therapies and, sometimes, surgical resection for debridement of necrotic bone or to consolidate or substitute the compromised bones and joints. Radiographs and bone cultures are the mainstays for the diagnosis but often are useless in the diagnosis of activity or relapse of infection in the lengthy management of these patients. Imaging with radiopharmaceuticals, computed tomography and magnetic resonance are also used to study secondary and chronic infections and their diffusion to soft or deep tissues. The diagnosis is quite easy in acute osteomyelitis of long bones when the structure of bone is still intact. But most cases of osteomyelitis are subacute or chronic at the onset or become chronic during their evolution because of the frequent resistance to antibiotics. In chronic osteomyelitis the structure of bones is altered by fractures, surgical interventions and as a result of bone reabsorption produced by the infection. Metallic implants and prostheses produce artefacts both in computed tomography and magnetic resonance images, and radionuclide studies should be essential in these cases. Vertebral osteomyelitis is a specific entity that can be correctly diagnosed by computed tomography or magnetic resonance imaging at the onset of symptoms but only with radionuclide imaging is it possible to assess the activity of the disease after surgical stabilization or medical therapy. The lack of comparative studies showing the accuracy of each radiopharmaceutical for the study of bone infection does not allow the best nuclear medicine techniques to be chosen in an evidence-based manner. To this end we performed a meta-analysis of peer reviewed articles published between 1984 and 2004 describing the use of nuclear medicine imaging for the study of the most frequent causes of bone infections, including prosthetic joint, peripheric post-traumatic bone infections, vertebral and sternal infections. Guidelines for the choice of the optimal radiopharmaceuticals to be used in each clinical condition and for different aims is provided.

CT-guided core biopsy of subchondral bone and intervertebral space in suspected spondylodiskitis

OBJECTIVE

Our objective was to determine the diagnostic performance of CT-guided core biopsy including both intervertebral disks and subchondral bone in suspected spondylodiskitis and compare the results with those for other biopsy techniques.

CONCLUSION

CT-guided core biopsy of subchondral bone and intervertebral space compares favorably to previously published studies because histology can provide the diagnosis even when no specific infectious agent is isolated.

Surgical strategies for vertebral osteomyelitis and epidural abscess

Pyogenic vertebral discitis and osteomyelitis (PVDO) has become an increasing problem for the spine surgeon. Despite recent advances in medical care and improved diagnostic neuroimaging, PVDO remains a major cause of illness and death in the elderly population. Infection of the spinal column often presents insidiously; however, if not treated appropriately and in a timely manner it can lead to severe neurological impairment, systemic septicemia, and progressive spinal deformity. In this paper the authors review the epidemiological and pathophysiological features and the clinical presentation of PVDO. Conventional medical therapy is described, with a particular focus on the methods of diagnosis. Surgical strategies for PVDO are then presented based on the literature and according to the practice of the senior author (S.L.O.), with an emphasis placed on structural considerations, implant selection, and techniques for augmenting vascular tissue to the site of infection.

[Osteomyelitis of the spine]

Spinal infections are rare, occurring most often in elderly patients with urinary tract infections or diabetes. With the increasing number of patients with immune suppression, and also the increasing number of immigrants in the population, spinal infections are seen more frequently, especially in young adults. Typically spinal infections are monomicrobial, Staphylococcus aureus being the most common organism. Hematogenous spread of bacteria through the arterial paravertebral collateral vessels into the subchondral bone marrow of the vertebral bodies is the most common source of infection. Clinical presentation is often nonspecific. Important diagnostic measurements are laboratory studies, radiological evaluation including MR image scans, and CT-guided percutaneous biopsy of the lesion for microbiological studies. The management of spinal infections consists of antimicrobial therapy over 6-8 weeks. Surgical intervention is indicated in neurologically compromised patients for spinal instability and abscesses.

Clinical feasibility of two-step streptavidin/111In-biotin scintigraphy in patients with suspected vertebral osteomyelitis

PURPOSE

Streptavidin accumulates at sites of inflammation and infection as a result of increased capillary permeability. In addition to being utilised by bacteria for their own growth, biotin forms a stable, high-affinity non-covalent complex with avidin. The objective of this investigation was to determine the diagnostic performance of two-step streptavidin/111In-biotin imaging for evaluating patients with suspected vertebral osteomyelitis.

METHODS

We evaluated 55 consecutive patients with suspected vertebral osteomyelitis (34 women and 21 men aged 27-86 years), within 2 weeks after the onset of clinical symptoms. Thirty-two of the patients underwent magnetic resonance imaging (MRI) and 24, computed tomography (CT). DTPA-conjugated biotin was radiolabelled by incubating 500 microg of DTPA-biotin with 111 MBq of 111In-chloride. Two-step scintigraphy was performed by first infusing 3 mg streptavidin intravenously, followed 4 h later by 111In-biotin. Imaging was begun 60 min later.

RESULTS

Streptavidin/111In-biotin scintigraphy was positive in 32/34 patients with spinal infection (94.12% sensitivity). The study was negative in 19/21 patients without infection (95.24% specificity). The corresponding results for MRI and CT were 54.17% and 35.29% (sensitivity), and 75% and 57.14% (specificity), respectively. All statistical parameters of diagnostic performance (Youden's J index, kappa measure of agreement with correct classification, accuracy, sensitivity, specificity, positive likelihood and negative likelihood) were clearly better for streptavidin/111In-biotin scintigraphy than for either MRI or CT.

CONCLUSION

Streptavidin/111In-biotin scintigraphy is highly sensitive and specific for detecting vertebral osteomyelitis in the first 2 weeks after the onset of clinical symptoms, and is potentially very useful for guiding clinical decisions on instituting appropriate therapy.

Biological imaging for the diagnosis of inflammatory conditions

Radiopharmaceuticals used for in vivo imaging of inflammatory conditions can be conveniently classified into six categories according to the different phases in which the inflammatory process develops. The trigger of an inflammatory process is a pathogenic insult (phase I) that causes activation of endothelial cells (phase II); there is then an increase of vascular permeability followed by tissue oedema (phase III). Phase IV is characterised by infiltration of polymorphonuclear cells, and a self-limiting regulatory process called apoptosis is observed (phase V). If the inflammatory process persists, late chronic inflammation takes place (phase VI). In some pathological conditions, such as organ-specific autoimmune diseases, chronic inflammation is present early in the disease. The aim of nuclear medicine in the field of inflammation/infection is to develop noninvasive tools for the in vivo detection of specific cells and tissues. This would allow early diagnosis of initial pathophysiological changes that are undetectable by clinical examination or by other diagnostic tools, and could also be used to evaluate the state of activity of the disease during therapy. These potential applications are of great interest in clinical practice. In this review, we describe the various approaches that have been developed in the last 25 years of experience. Recent advances in the diagnosis of inflammatory processes have led to the development of specific radiopharmaceuticals that are intended to allow specific stage-related diagnosis.