Diagnostic Imaging of Osteomyelitis

Infection in the Immobile Host: A Practical Review for the Intensive Care Physician

Immobility in the critically ill patient is a significant risk factor for infection, independent of the patient's underlying critical illness. Specific causes of infection related to immobility in the intensive care setting are explored. The pathogenesis, treatment, complications, and prevention of pressure ulcers, pneumonia, and urinary tract infections in the immobile patient are emphasized. Featured topics include the differentiation of colonization versus infection in pressure ulcers and the urinary tract, the significance and optimal treatment of positive fungal cultures, as well as a rational clinical approach to the immobile patient with a fever and no obvious source of infection. The clinical relevance of anaerobic infections in this population is emphasized because it influences empiric antibiotic therapy and differential diagnosis.

An Unusual Cause of Chest Pain in a Young Healthy Female

BACKGROUND

Infection of the sternoclavicular joint is an uncommon disease that is usually seen in patients with underlying risk factors such as prior trauma, intravenous drug use, or diabetes mellitus. The true pathophysiology remains unknown, but underlying bacteremia has been found in a number of cases. Without proper diagnosis and treatment, severe complications such as mediastinitis, sepsis, or death can occur.

CASE REPORT

This is a case of spontaneous stenoclavicular septic arthritis in an otherwise healthy female. The patient's lack of risk factors and minimal examination findings highlight the unusual nature of the case, as well as the challenges it presents in making an early diagnosis. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS CONDITION?: Emergency physicians should consider sternoclavicular joint infections in patients who present to the emergency department with chest pain, even in patients without risk factors. They should especially consider the diagnosis in patients with suspected musculoskeletal etiologies or in those with return visits for chest pain. Although most patients do well with treatment, the infection can be life threatening without appropriate interventions.

A Novel Technique for the Surgical Treatment of Chronic Osteomyelitis of Long Bones: A Case Report

CASE

A twenty-eight-year-old man sustained an open, comminuted tibial plateau fracture from a gunshot wound. Treatment included external fixation, serial debridements, and subsequent open reduction and internal fixation. Five months later, he developed chronic osteomyelitis of the proximal part of the tibia. Intraosseous debridement and irrigation with an arthroscope and arthroscopic tools was performed through existing bone screw holes. At the time of the final follow-up, he had resolution of pain and no recurrent infection.

CONCLUSION

This minimally invasive technique may be considered for the treatment of chronic osteomyelitis of long bones to prevent structural destabilization and minimize disability.

Imaging in pelvic osteomyelitis: support for early magnetic resonance imaging

BACKGROUND

Children with pelvic osteomyelitis may present with symptoms that are nonspecific. Conventional imaging modalities including plain radiographs, ultrasound, technetium bone scan, and computed tomography rarely demonstrate pathology that is diagnostic of this condition. As a result, accurate diagnosis is often delayed, and children may undergo surgical diagnostic or therapeutic procedures that may be avoided. We report the radiographic and magnetic resonance imaging (MRI) findings in 23 children admitted with a suspected diagnosis of pelvic osteomyelitis. We are presenting imaging findings in children with suspected pelvic osteomyelitis with emphasis on MRI abnormalities and to propose an anatomical classification based on the patterns of pelvic involvement.

METHODS

The medical records and imaging reports of all patients admitted to our institution with a history and physical examination suggestive of pelvic osteomyelitis between July 31, 1992, and March 10, 2003 were reviewed. Criteria were defined for the diagnosis of pelvic osteomyelitis based on criteria used by Farley et al in 1985. Specific attention was paid to the imaging strategies used and the influence of each radiographic method on the ultimate diagnosis.

RESULTS

Abnormalities on the MRI included soft tissue inflammation and bone edema. These findings were bright on T2 and short inversion time Short T1 inversion recovery (STIR) images and enhanced after gadolinium administration. Five distinct patterns of pelvic involvement were observed, each corresponding to a cartilaginous epiphysis or apophysis. These were the sacroiliac joint, triradiate cartilage, pubic symphysis, ischium, and iliac apophysis. One patient had a noninfectious cause of presentation with a deep vein thrombosis, whereas another was diagnosed with Hodgkin lymphoma in addition to osteomyelitis of the ischium.

CONCLUSIONS

Magnetic resonance imaging is a sensitive technique for evaluation of pyogenic infections involving the pelvis. In patients presenting with clinical findings and laboratory studies suggesting an infectious process, MRI with gadolinium enhancement should be performed as an early study. Magnetic resonance imaging is also effective in identifying other conditions that may resemble pelvic osteomyelitis.

Decreased radiopharmaceutical uptake (photopenia) in delayed phase scintigraphic images in three horses

Decreased radiopharmaceutical uptake, photopenia, in delayed phase scintigraphic images is recognized in people but has only been reported rarely in horses. We describe three horses with septic osteitis, bone sequestrum formation, or distal limb thrombosis that had photopenia of the affected extremity. Photopenia may indicate the presence of ischemia and can be used to facilitate clinical decision making and prognosis assessment

Osteomyelitis in Horses

Much has been learned in the past decade about osteomyelitis. The inhibitory mechanisms of the "biofilm slime" layer that is formed by bacterial extracapsular exopolysaccharides and binds to bone, joints, and implants are now better understood than in the past. The surface colonization of bacteria that occurs within these biofilms is a biologic phenomenon that is somewhat unique to orthopedic infections. This survival strategy of bacteria is effective, and it is important for veterinarians who treat osteomyelitis to be aware of current diagnostic and therapeutic treatment modalities. The practitioner should be aware of the most common bacteria associated with osteomyelitis and the traditional treatments that are still used. Current therapeutic treatment modalities, such as antibiotic- impregnated polymethylmethacrylate, antibiotic-impregnated plaster of Paris, and regional perfusion, have become routine, however, and have been responsible for improving the prevention and outcome of osteomyelitis in the horse. It is the intent of this article to make equine veterinarians aware of current information as well as the future treatments of osteomyelitis.

Hematogenous Vertebral Osteomyelitis Due to Staphylococcus aureus in the Adult: Clinical Features and Therapeutic Outcomes

OBJECTIVE

Staphylococcus aureus is the most common cause of hematogenous vertebral osteomyelitis in adults. To better define clinical features and therapeutic outcomes, the charts of 40 adult patients with S aureus hematogenous vertebral osteomyelitis were retrospectively reviewed.

METHODS

Retrospective chart review using standardized data collection form.

RESULTS

S aureus hematogenous vertebral osteomyelitis commonly occurred in the settings of recent invasive procedures (55% of patients), insulin use (28%), and hemodialysis (20%). Ten percent of patients had S aureus bacteremia or vascular catheter infection within the preceding 6 months. Median time from first symptom to diagnosis was 51.3 days. A portal of entry for S aureus was identified in 13 patients (32.5%); intravenous catheters were the likely origin in 9 of those 13 patients. Concurrent endocarditis was present in 4 patients. Forty-eight percent of patients had neurologic abnormalities and 60% of patients had an epidural, paraspinous, or psoas abscess demonstrated by neuroimaging. S aureus was isolated through fine-needle aspiration in 17 of 23 patients (74%) and from blood cultures in 23 of 34 patients (68%). Infection was due to methicillin-susceptible S aureus in 67.5% of patients. All patients received intravenous antibiotics for a mean duration of 58.6 days; 36 of 40 (90%) also received concomitant rifampin. Twenty-seven percent and 12.5% of patients underwent surgical debridement and CT-guided drainage of abscesses, respectively. After intravenous therapy, 19 of 30 eligible patients received oral continuation treatment. The mean duration of total antibiotic therapy was 142.2 days.

CONCLUSIONS

Cure of infection was achieved in 83% (24/29) of evaluable patients, but 50% of those achieving cure still had infection-related sequelae. Intravenous antibiotic therapy for at least 8 weeks was the only clinical factor associated with cure (P = 0.05, two-tailed Fisher exact test).

MR imaging of the diabetic foot: diagnostic challenges

Pedal complications of diabetes have long presented a challenge for the clinician and radiologist predominately related to the difficulty in distinguishing infection from neuroarthropathy. The spectrum of diabetic foot infections is broad, ranging from callous and ulcer formation, to septic arthritis, abscess formation, and osteomyelitis. This article summarizes the MR imaging findings in the diabetic foot and the optimal pulse sequences. Focus is placed on aids in differentiating diabetic infection from other entities and increasing the specificity of diagnosing diabetic foot complications.

[Acute osteomyelitis in children: early MRI diagnosis]

PURPOSE

To assess the value of MRI for early diagnosis of osteomyelitis in children presenting with sepsis and acute onset of musculoskeletal pain.

MATERIALS AND METHODS

MRI including fat suppressed T2W, and fat suppressed pre- and postcontrast T1W sequences was performed within 48 hours of admission in 26 children with clinical (fever and acute musculoskeletal pain) and biological (elevated WBC count and ESR in all cases, and elevated CRP in 12 patients) suspicion of acute osteomyelitis. None of the patients had sickle cell disease.

RESULTS

MRI was normal in 7 children (26%). Bone marrow signal abnormality was noted in 19 cases (74%) consistent with acute osteomyelitis in 18 cases and metastatic neuroblastoma in 1 case.

CONCLUSION

MRI is useful for evaluation of children presenting with sepsis and acute musculoskeletal pain, early diagnosis of osteomyelitis and to prevent unnecessary hospital admission and work-up.

Retrospective study of 24 cases of septic calcaneal bursitis in the horse

REASONS FOR PERFORMING STUDY

Wounds to the plantar aspect of the tarsus present a diagnostic and treatment challenge. This study was undertaken to describe specific features of traumatic wounds involving the calcaneal bursa, with a view to determining which clinical examination findings and diagnostic tests results could provide reliable indicators of prognosis.

OBJECTIVES

To report clinical presentation, diagnostic findings, treatment and outcome of 24 cases of septic calcaneal bursitis; and to determine the importance of the involvement of specific anatomical structures in relation to the prognosis for survival and return to athletic function.

METHODS

Records of 24 horses that had suffered traumatic wounds involving the calcaneal bursae were reviewed and divided into 3 groups, based on the bursa involved and presence or absence of involvement of the tuber calcanei. Clinical, diagnostic imaging and surgical findings were recorded for each case. Differences between groups and outcome were examined for significance with Chi-squared, Fisher's Exact or Kruskal-Wallis tests, as appropriate.

RESULTS

Wounds involving only the subcutaneous bursa had an excellent prognosis for survival. Seventy-five percent of horses with wounds involving the intertendinous calcaneal bursa survived. Involvement of the tuber calcanei presented a fair to guarded prognosis, with only 44% of horses with involvement of this structure surviving.

CONCLUSIONS

In contrast to other studies of septic synovial structures, the time between initial injury and referral did not affect the outcome. Correct identification of invasion of the calcaneal bursa(e) and/or tuber calcanei in wounds to the plantar aspect of the tarsus allows for more accurate pronostication. Damage to the tuber calcanei presents a poorer prognosis than for cases that involve only the soft tissue structures in the region.

POTENTIAL RELEVANCE

This study demonstrates the importance of correct anatomical identification of structures involved in wounds in the region of the calcaneal bursa. The use of radiography, ultrasonography and synoviocentesis are essential in these cases to provide the most appropriate treatment for the horse and accurate prognosis for the owner.

Work-up of the diabetic foot

Diabetes is a common disease with potentially devastating complications affecting the foot and ankle. A combination of vascular disease, peripheral neuropathy, and immunopathy results in a cascade of conditions including ischemia and infarction, tendinopathy, atrophy, edema, deformity, neuropathic osteoarthropathy, callus, ulceration, and infection. MRI is useful for evaluation of these complications, and assists the clinician in medical or surgical planning.

Exclusion of chronic osteomyelitis with F-18 fluorodeoxyglucose positron emission tomographic imaging

PURPOSE

Excluding the diagnosis of chronic osteomyelitis is often difficult with noninvasive techniques, especially when bone anatomy and structure have been altered by trauma, surgery, or soft-tissue infection. It has been reported that fluorodeoxyglucose (FDG) positron emission tomography (PET) has excellent potential to diagnose osteomyelitis. In this study, the accuracy of FDG PET in the diagnosis of chronic osteomyelitis was determined.

METHOD

Twenty-two patients with possible osteomyelitis (5 in the tibia, 5 in the spine, 4 in the proximal femur, 4 in the pelvis, 2 in the maxilla, and 2 in the feet) who underwent FDG PET imaging and on whom operative or clinical follow-up data were available were included in this analysis. The final diagnosis was made by surgical exploration or clinical follow-up during a 1-year period.

RESULTS

FDG PET correctly diagnosed the presence or absence of chronic osteomyelitis in 20 of 22 patients. Six had chronic osteomyelitis and 16 proved to be free of osteomyelitis. FDG PET correctly identified all six patients with chronic osteomyelitis but produced two false-positive results. This study had a sensitivity rate of 100%, a specificity rate of 87.5%, and an accuracy rate of 90.9%.

CONCLUSION

FDG PET is a highly effective imaging method to exclude osteomyelitis when a negative scan result is obtained. However, positive results can be caused not only by true osteomyelitis but also by inflammation in the bone or surrounding soft tissues as a result of other causes. Overall, FDG PET may prove to be the preferred study in the management of patients with possible chronic osteomyelitis.

Spiral CT and three-dimensional CT of musculoskeletal pathology. Emergency room applications

Spiral CT is a fast and effective modality for evaluating a wide variety of musculoskeletal abnormalities in the emergency department setting. The role of spiral CT in evaluating musculoskeletal trauma and musculoskeletal inflammation and infections is discussed, as is the use of multiplanar and three-dimensional imaging.

Role of magnetic resonance imaging in the diagnosis of osteomyelitis in diabetic foot infections

PURPOSE

The role of magnetic resonance imaging (MRI) in the diagnosis of osteomyelitis in foot infections in diabetics was investigated. The accuracy, sensitivity, and specificity of MRI, plain radiography, and nuclear scanning were determined for diagnosing osteomyelitis, and a cost comparison was made.

METHODS

Twenty-seven patients with diabetic foot infections were studied prospectively. All patients underwent MRI and plain radiography. Twenty-two patients had technetium bone scans, and 19 patients had Indium scans. Nineteen patients had all four tests performed. Patients with obvious gangrene or a fetid foot were excluded.

RESULTS

The diagnosis of osteomyelitis was established by pathologic specimen (n = 18), bone culture (n = 3), or successful response to medical management (n = 6). Osteomyelitis was confirmed in nine of the pathologic specimens. The diagnostic sensitivity, specificity, and accuracy for MRI was 88%, 100%, and 95%, respectively, for plain radiography it was 22%, 94%, and 70%, respectively, for technetium bone scanning it was 50%, 50%, and 50%, respectively, and for Indium leukocyte scanning it was 33%, 69%, and 58%, respectively. The data were analyzed statistically with the two-tailed Fisher's exact test. MRI was the only test that was statistically significant (p < 0.01).

CONCLUSIONS

MRI appeared to be the single best test for the diagnosis of osteomyelitis associated with diabetic foot infections. It had a better diagnostic accuracy than conventional modalities and appeared to be more cost-effective than the frequently used Indium scan.

In-111 WBC imaging of osteomyelitis in patients with underlying bone scan abnormalities

One hundred seven combined In-111 WBC/Tc-99m MDP scans performed on 87 patients with a high clinical suspicion of osteomyelitis were retrospectively reviewed. An 86% sensitivity and a 94% specificity for detecting osteomyelitis were found. In addition, patients were grouped into one of five clinical settings for more detailed analysis: diabetic osteoarthropathy, previous arthroplasty, fracture, overlying skin ulcer, and other etiology. Forty-seven studies were performed while patients received antibiotic therapy without loss of sensitivity for detecting osteomyelitis. Results obtained with scintigraphy compared favorably to other imaging and laboratory studies used to detect osteomyelitis. In conclusion, the combined In-111 WBC/Tc-99m MDP scan is a very sensitive and specific method to detect osteomyelitis in patients with concurrent diabetic osteoarthropathy, fracture, postoperative healing, and overlying skin ulcer. Antibiotic treatment does not appear to adversely affect the sensitivity of these scans.

Evaluation of a rabbit model for osteomyelitis by high field, high resolution imaging using the chemical-shift-specific-slice-selection technique

The rabbit model of osteomyelitis introduced by C.W. Norden, based on injection of an infecting solution (Staphylococcus aureus, sodium morrhuate) into the tibia, was studied at 4.7 Tesla with a time-efficient chemical shift selective imaging technique, Chemical Shift Specific Slice Selection (C4S). The evolution of the disease over several weeks was followed on water-selective, fat-selective, and sum images obtained simultaneously with this imaging sequence. Experiments were performed either on different groups of rabbits at different times after infection with subsequent sacrifice of the animal and microbiological analysis of the infected tibia or on the same group of animals imaged several times after infection. Associated analysis of the water and fat selective images revealed marrow modifications very early (Day 5 after inoculation) demonstrating the high sensitivity of the employed imaging technique. Later on, bone modifications were best identified on the sum images. Additional experiments performed on animals injected with a noninfecting solution containing only sodium morrhuate showed however that the sclerosing agent alone can yield images similar to those produced by infection at early stages after inoculation. Therefore, the Norden model would not be suitable for monitoring quantitatively outcome of therapy by magnetic resonance imaging. It is however well adapted for the evaluation and optimization of MRI techniques or protocols intended to detect early changes of bone marrow produced by septic or aseptic infarct.