Assesment by MRI in the diagnosing of osteomyelitis in children

Transcription

1 Assesment by MRI in the diagnosing of osteomyelitis in children Poster No.: C-1295 Congress: ECR 2011 Type: Educational Exhibit Authors: M. Teixidor Viñas, J. L. Ribó, J. muxart, J. Blanch, L. Riaza ; Girona/ES, barcelona/es Keywords: Musculoskeletal joint, Paediatric, MR, Infection DOI: /ecr2011/C-1295 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 49

2 Learning objectives 1. Review the clinical behavior of musculoskeletal infection in childhood. 2. Address different forms of behavior of osteomyelitis during the course of the disease by dividing the progression of this disease in: - Acute - Subacute - Chronic 3. Illustrate the potential complications Page 2 of 49

3 Background We retrospectively studied 375 chiildren admetted to our hospital from 1999 to 2008 with osteomyelitis / osteoarthritis patients had osteoarthritis (54'1%) and 172 were diagnosed with osteomyelitis (47'9%). - The hip is the joint most commonly affected in osteoarthritis (97 patients), followed by knee (42) and shoulder (27). OSTEOARTHRITIS Septic arthritis is the most common form of infectious arthritis in childhood, most cases are observed in children under 3 years old. The most common causal mechanism is hematogenous spread, but it can also be caused by a joint involvement of osteomyelitis or soft-tissue infection or occur secondary to trauma. The pathophysiology of arthritis begins by bacterial infection of the richly vascularized synovial membrane. This leads to an inflammatory reaction, which is turn leads to the destruction of the cartilage matrix, resulting in increased intraarticular pressure secondary to purulent exsudates, exacerbating the destructive process. - Ostheomyelitis most often affects the long bones (n=1 16), followed by short bones and the axial skeleton (n= 56). Page 3 of 49

4 Fig.: Long bone involvement is most common in pediatric osteomyelitis. Different imaging studies are complementary. Plain films show osteomyelitic diaphyseal involvement with epiphyseal extension, and MRI identifies the involvement of the growth line. References: - Girona/ES - Insidious or subacute osteomyelitis was common in our series, so imaging plays a crucial role in the definitive diagnosis. - The germ most frequently isolated is S. Aureus in patients of all ages, but there has been a steady increase in less common causative organism such as Kingella. - Blood cultures were positive in 34.30% of patients. - Clinically, osteomyelitis often presents with fever, pseudoparalysis of the affected extremity, and pain on manipulation. But it also can manifest as decreased mobility, edema, or erythema. Page 4 of 49

5 - Plain film radiography is the initial technique of choice, although radiographic changes are not usually apparent until 7 to 10 days after onset. Fig.: Plain-film radiography is the technique of choice for diagnosing osteomyelitis, but no significant findings were observed during the first 7-10 days. References: - Girona/ES Page 5 of 49

6 Images for this section: Fig. 0: Long bone involvement is most common in pediatric osteomyelitis. Different imaging studies are complementary. Plain films show osteomyelitic diaphyseal involvement with epiphyseal extension, and MRI identifies the involvement of the growth line. - Girona/ES Page 6 of 49

7 Fig. 0: Plain-film radiography is the technique of choice for diagnosing osteomyelitis, but no significant findings were observed during the first 7-10 days. - Girona/ES Page 7 of 49

8 Imaging findings OR Procedure details Characteristically, bone infections in children occur with hematogenous bacterial seeding. Infections secondary to trauma or continuous spread from soft-tissue infections are rare. SPECIAL FEATURES OF OSTEOMYELITIS IN CHILDHOOD: To understand the manifestations of osteomyelitis in childhood, it is essential to bear in mind normal anatomy, bone development, and cartilage vascularization. Newborns' bones have diaphyseal vessels that extend through the metaphysis and penetrate the cartilaginous growth plate to reach the epiphysis. Page 8 of 49

9 Fig.: In the newborn, bones have diaphyseal vessels that extend through the metaphysis and penetrate the cartilaginous growth plate to reach the epiphysis. This explains the increased frequency of epiphyseal and joint infections in neonates. References: This explain the increased frequency of epiphyseal and joint infections in neonates. Fig.: There is an increased frequency of epiphyseal and joint infections in neonates. References: - Girona/ES Sometime between 8 and 18 months of age the vascular connection through the growth plate is severed. The diaphyseal vessels end in the metaphysis, where dilated veins form lakes, and subsequently enter the growth plate to supply it with blood. Venous blood flow through the lakes is slow and turbulent. This explains why osteomyelitis in children typically begin in the metaphysis of long bone. Page 9 of 49

10 Fig.: From 8 to 18 months of age the vascular connection through the growth plate is severed. The diaphyseal vessels end in the metaphysis, where dilated veins form lakes, and subsequently enter the growth plate to supply it with blood. Venous blood flow through the lakes is slow and turbulent. References: When the growth plate closes, the blood suppy of the diaphysis and epiphysis is independent being at this time more typical epiphyseal osteomyelitis with articular joint extension. 1. ACUTE OSTEOMYELITIS Bone infection starts in the medullary cavity, conditioning edema, cellular infiltration and increased caliber of vessels, made of an increase of pressure in the cortex and Volkmann's chanals with subsequent subperiosteal space involvement and ultimately term invaid the soft tissues adjacent to the periosteum.. Joint infection can occur when an abscess in an intra-articular metaphysis ruptures into the joint space. Page 10 of 49

11 1. 1. ACUTE OSTEOMYELITIS: FINDINGS ON MAGNETIC RESONANCE MRI is the most sensitive test for the diagnosis of osteomyelitis. The typical findings are: - Occupation of bone marrow: Edema, pus, or inflammatory cells in bone marrow and vascular engorgement: Bone marrow signal changes: hypointensity on T1-weighted sequences and hyperintensity on T2-weighted and STIR sequences. Dense areas seen within the affected bone on both T1- and T2-weighted images may be related to bone abscesses. - Involvement of adjacent soft tissues: Poorly defined hyperintense areas on T2-weighted sequences. Although soft-tissue infection is typically hyperintense on contrast-enhanced T1-weighted sequences, intravenous contrast is rarely used in children. - Ill-defined, hyperintense normal diameter cortical bone on T2-weighted sequences. Page 11 of 49

12 Fig.: MRI and plain-film correlation in a patient with acute osteomyelitis References: - Girona/ES Page 12 of 49

13 Fig.: T1-weighted image shows an ill-defined area of hypointense bone marrow. T2weighted image shows the hyperintense core with preserved diameter References: - Girona/ES Page 13 of 49

14 Fig.: 12-year-old boy with retrosternal pain, Lateral chest film shows reduced bone mineralization associated with increased retrosternal density. STIR MRI sequence shows a signal alteration associated with discontinuity of the cortex of the posterior aspect of the sternum and with an alteration of the anterior mediastinal structures. References: - Girona/ES Page 14 of 49

15 Fig.: MRI shows the retrosternal abscess is causing a mass effect on the heart. US shows a predominantly hyperechoic heterogeneous collection with ill-defined borders where the manubrium joins the body of the sternum. References: - Girona/ES Page 15 of 49

16 Fig.: Examples of MRI in patients with acute osteomyelitis. References: - Girona/ES 2. SUBACUTE OSTEOMYELITIS SUBACUTE OSTEOMYELITIS is defined as a non-suppurative sclerosing osteomyelitis. It is often caused by S. Aureus and the predisposing factors are: - Microbial resistance to antibiotics. - Low virulence of the organism: symptoms are often mild or absent. - Prior administration of antibiotics SUBACUTE OSTEOMYELITIS: MRI FINDINGS Page 16 of 49

17 The classic radiological sign is Brodie's abscess, with well-defined margins and communication with the physis through a channel that extends to the epiphysis. Fig.: Lytic lesion in the proximal metaphysis of the left femur (hyperintense signal on T2-weighted and STIR sequences and hypointense on T1-weighted sequences). Note the mild involvement of the epiphysis and the growth line References: - Girona/ES Detection of a sclerotic bone fragment is indicative of sequestration. DIFFERENTIAL DIAGNOSIS In 50% of cases, subacute osteomyelitis is confused with a tumor, with the differential diagnosis: Page 17 of 49

18 1. Histocitosis Langerhans cells. 2. Tuberculosis. 3. osteoid osteoma. 4. Enchondroma. 5. Osteosarcoma. 6. Ewing sarcoma. 7. Chondroblastoma BRODIES ABSCES: Type of paucisymptomatic subacute or chronic osteomyelitis caused by microorganisms of low virulence (often S. aureus). Commonly affects the metaphysis of long bones, the femur being the most frequently affected bone. In Brodie's abscess, the bone abscess was surrounded by fibrosis and bone sclerosis, seen as a halo on MRI. Page 18 of 49

19 Fig.: Illustrations on the formation of Brodie's abscess with fibrosis and bone sclerosis. References: MRI shows the 4 layers making up the abscess: - Granulation tissue surrounding the cavitated central part of the abscess is isointense on T1-w sequences, hyperintense on T2-w and STIR sequences, and hyperintense on contrast-enhanced T1-w sequences. - The peripheral ring from the fibrous reaction is hypointense on all MR sequences. - The peripheral layer is formed by a ring of endosteal reaction that is hypointense on T1-w sequences. Page 19 of 49

20 Fig.: Brodie's abscess that has eroded the periosteum and formed a fistulous tract into the soft tissues, reaching subcutaneous tissue. References: - Girona/ES Page 20 of 49

21 Fig.: Boy with minimal effusion and multiple fistulas through the bone that extend into the muscles of the left medial thigh. These findings suggest chronic osteoarthritis. References: - Girona/ES 3. CHRONIC OSTEOMYELITIS Chronic osteomyelitis is defined as symptomatic bone infection that persists after one month of starting antibiotic treatment or one month after surgery for trauma. In chronic osteomyelitis, the loss of blood supply to an area of bone may result in the formation of a necritic devitalized bone fragment (sequestrum) surrounded by granulation tissue. A thick sheath of periosteal new bone (involucrum) can develop can develop around the sequestrum. Page 21 of 49

22 Fig.:.: The top image shows signs of SUBACUTE OSTEOMYELITIS and bone sequestration in CHRONIC OSTEOMYELITIS. The bottom image shows patchy lesions in the sternal body (hypointense with a hyperintense halo on T1-w images and hyperintense on T2-w images) corresponding to bone sequestration in CHRONIC OSTEOMYELITIS. Note the significant decrease in the size of the retrosternal fluid collection. References: - Girona/ES Page 22 of 49

23 Fig.: 12 year old patient with chronic osteomyelitis in the right humerus. References: - Girona/ES Page 23 of 49

24 Fig.: Two-year-old boy with chronic osteomyelitis of the right femur limited by the growth plate. References: - Girona/ES Sequestering is rare in neonates and elevation of the periosteum is common CHRONIC OSTEOMYELITIS: MRI FINDINGS Useful for the diagnosis of bone sequestering: a sequestrum is depicted as a hypointense focus on unenhanced T1- and T2-w sequences that enhances on postcontrast T1-w images. - Sinus tract: hyperintense linear image on T2-w images that does not enhance on postcontrast T1-w images. Page 24 of 49

25 ARTHRITIS IN CHILDHOOD Plain-film X-rays show normal muscle in many cases. Pathological findings (not always present) include increased joint space and soft-tissue edema with disruption of normal muscle levels. Ultrasound has an important role in the diagnosis of osteoarthritis, in which the amount of articular fluid is increased. Pus is echogenic and confirms the diagnosis, whereas suppurative fluid is anechoic and only suggestive of osteoarthritis. Ultrasound can also guide percutaneus needle aspiration of the lfluid observed. CT provides very little information, although it can suggests bone involvement in osteoarthritis. Contrast-enhanced MRI is the most sensitive test for the diagnosis of arthritis, showing increased amounts of joint fluid and wall enhancement on postcontrast T1-w sequences. Page 25 of 49

26 Fig.: MRI studies show arthritis as an increase in joint fluid. MRI can also evaluate bone marrow involvement and assess lymph nodes and collections. References: - Girona/ES ILLUSTRATION OF POSSIBLE OSTEOMYELITIS COMPLICATIONS The following complications can develop to various complications: - Subluxation, ischemia or avascular necrosis: As a result of the increased intra-articular pressure in the infected joint. - Cartilage degeneration: Chondritis and subsequent deformation as a result of proteolytic degradation of cartilage by the joint exsudate s from infection. - Fractures, early closure of the line of growth, chronic infection. Page 26 of 49

27 Fig.: Chronic osteomyelitis has resulted in non-fracture-related ossification and the loss of bone mineralization. References: - Girona/ES Page 27 of 49

28 Images for this section: Fig. 0: In the newborn, bones have diaphyseal vessels that extend through the metaphysis and penetrate the cartilaginous growth plate to reach the epiphysis. This explains the increased frequency of epiphyseal and joint infections in neonates. Page 28 of 49

29 Fig. 0: There is an increased frequency of epiphyseal and joint infections in neonates. - Girona/ES Page 29 of 49

30 Fig. 0: From 8 to 18 months of age the vascular connection through the growth plate is severed. The diaphyseal vessels end in the metaphysis, where dilated veins form lakes, and subsequently enter the growth plate to supply it with blood. Venous blood flow through the lakes is slow and turbulent. Page 30 of 49

31 Fig. 0: MRI and plain-film correlation in a patient with acute osteomyelitis - Girona/ES Page 31 of 49

32 Fig. 0: T1-weighted image shows an ill-defined area of hypointense bone marrow. T2weighted image shows the hyperintense core with preserved diameter - Girona/ES Page 32 of 49

33 Fig. 0: 12-year-old boy with retrosternal pain, Lateral chest film shows reduced bone mineralization associated with increased retrosternal density. STIR MRI sequence shows a signal alteration associated with discontinuity of the cortex of the posterior aspect of the sternum and with an alteration of the anterior mediastinal structures. - Girona/ES Page 33 of 49

34 Fig. 0: MRI shows the retrosternal abscess is causing a mass effect on the heart. US shows a predominantly hyperechoic heterogeneous collection with ill-defined borders where the manubrium joins the body of the sternum. - Girona/ES Page 34 of 49

35 Fig. 0: Examples of MRI in patients with acute osteomyelitis. - Girona/ES Page 35 of 49

36 Fig. 0: Lytic lesion in the proximal metaphysis of the left femur (hyperintense signal on T2-weighted and STIR sequences and hypointense on T1-weighted sequences). Note the mild involvement of the epiphysis and the growth line - Girona/ES Page 36 of 49

37 Fig. 0: Correlation of different types of imaging studies performed in a 7-year-old girl with subacute osteomyelitis in the right acetabulum - Girona/ES Page 37 of 49

38 Fig. 0:.: The top image shows signs of SUBACUTE OSTEOMYELITIS and bone sequestration in CHRONIC OSTEOMYELITIS. The bottom image shows patchy lesions in the sternal body (hypointense with a hyperintense halo on T1-w images and hyperintense on T2-w images) corresponding to bone sequestration in CHRONIC OSTEOMYELITIS. Note the significant decrease in the size of the retrosternal fluid collection. - Girona/ES Page 38 of 49

39 Fig. 0: Illustrations on the formation of Brodie's abscess with fibrosis and bone sclerosis. Page 39 of 49

40 Fig. 0: Brodie's abscess that has eroded the periosteum and formed a fistulous tract into the soft tissues, reaching subcutaneous tissue. - Girona/ES Page 40 of 49

41 Fig. 0: Boy with minimal effusion and multiple fistulas through the bone that extend into the muscles of the left medial thigh. These findings suggest chronic osteoarthritis. - Girona/ES Page 41 of 49

42 Fig. 0: 12 year old patient with chronic osteomyelitis in the right humerus. - Girona/ES Page 42 of 49

43 Fig. 0: Two-year-old boy with chronic osteomyelitis of the right femur limited by the growth plate. - Girona/ES Page 43 of 49

44 Fig. 0: MRI studies show arthritis as an increase in joint fluid. MRI can also evaluate bone marrow involvement and assess lymph nodes and collections. - Girona/ES Page 44 of 49

45 Fig. 0: Chronic osteomyelitis has resulted in non-fracture-related ossification and the loss of bone mineralization. - Girona/ES Page 45 of 49

46 Conclusion Imaging tests are necessary for early diagnosis; they can identify the exact location of involvement, evaluate whether it is multifocal or unilateral, and determine whether it extends to the soft tissues. Osteomyelitis / subacute osteoarthritis is increasingly common, making both the clinical examination and imaging tests increasingly important. Subacute osteomyelitis has a greater impact in children, and clinical examination alone cannot reach the correct diagnosis; thus, imaging studies are essential. MRI is necessary to ensure the earliest diagnosis, to determine the exact location of involvement, to evaluate whether the focus of infection is single or multiple, and to assess the extension of the infection into adjacent soft tissue. Page 46 of 49

47 Fig.: MRI is useful for the assessment of multiple focal OSTEOMYELITIS References: - Girona/ES Page 47 of 49

48 Personal Information Page 48 of 49

49 References 1. Imaging of musculoskeletal infections. Kothari, Pelchovitz, Meyer. Pediatric musculoskeletal radiology. Volume 39 (4); july A regional approach to osteomyelitis of the lower extremities in children. Kleinman. Radiologic clinics of north america, 2002; Imaging of osteomyelitis in the mature skeleton. Tehranzanadech. Radiologic clinics of north america, 2001 (39) num 2, march Imaging of osteomyelitis in children. Radiologic clinics of north america, 2001 (39) num 2, march Imaging of chronical and recurrent multifocal osteomyelitis. Jurriaans, Singh, Finlay. Radiologic clinics of north america, 2001 (39) num 2, march Page 49 of 49