Answer for BIR CoW 09 May 2021
Osteomyelitis of scapula with adjoining peri osseous abscess
Findings
Lytic area with surrounding bone marrow infiltration and adjoining soft tissue collection noted in inferior aspect of body of scapula. Collection measures 1.8 (cranio caudal) x 1 (anteroposterior) x 1.8 (transverse) cms. Lytic areas with adjoining collection shows diffusion restriction with low ADC values. STIR hyperintensity noted in infraspinatus muscle with subcutaneous edema noted adjacent to the lesion -reactive inflammatory changes. Subcentric right axillary lymph nodes noted.
Discussion
AOM is defined as an acute infection of the bone by a pathogenic bacterium, most often S. aureus, occurring forthe most part in children. The metaphysis of the long bones is the most frequent location of hematogenic AOM in children. Involvement of the short and flat bones is rare. Scapula involvement is usually in the body of the scapula and is exceptional. AOM occurs more frequently in boys often living in under-privileged areas with poor hygiene, promoting entry points for infection. CLINICAL FEATURES: The clinical picture of AOM of the scapula presents certain features and varies with the progressive stages of the disease. At onset, the symptoms are vague, comprising of unspecific clinical signs, sometimes misleading and possibly confused with osteoarthritis of the shoulder (poorly localized pain, painful mobilization of the shoulder explainedby reactive joint effusion). This inconclusive picture was responsible for the delay in diagnosis and management, lasting less than 12 h At a more advanced stage or at the disease stage, the extension of pus outside the scapula is rapid. This scapular periosteum explains the rapidity of the dissemination of the pus to the soft tissues contained under the infraspinatus muscle. The clinical manifestation is tumefaction of the posterior area of the scapula, indicating the location of theosteomyelitis and associating fever and pain upon mobilization of the scapula. At this stage, functional incapacity is total.At end-stage disease, the spread of pus into the scapula and the surrounding soft tissues causes frank spinal column disease (scoliotic posture) in association with severe tumefaction of the scapular region and alteration of the patient’s general condition IMAGING: First line modality radiography is useful for excluding other differential diagnoses such as trauma or tumor, however radiographs are insensitive for the detection of early osteomyelitis. Radiography may be normal in cases of osteomyelitis up to 14 d after the onset of infection and even then, only 20% of cases demonstrate radiographic abnormalities after this two-week delay. Additionally, the early radiographic findings, including soft tissue swelling, vague bony lucency, and periosteal reaction, may be subtle and may not reflect the true extent of disease. Triple-phase bone scintigraphy using 99mTc-methylene diphosphonate (99mTc-MDP) can demonstrate evidence of infection as soon as 24 h after onset and also has the advantage of being able to depict multiple sites of infection. Osteomyelitis typically manifests as increased radiotracer uptake on all phases (angiographic, blood pool, and delayed) of the triple-phase examination. However 99mTc-MDP scintigraphy is limited by poor anatomic detail and is insensitive for the detection of abscesses and extraosseous involvement. Furthermore, the sensitivity of 99mTc-MDP scintigraphy for the diagnosis of osteomyelitis, which in the past has been reported to be as high as 80%, may be decreasing with the increasing incidence of MRSA infections that tend to have significant soft-tissue involvement. MRI is both sensitive for the detection of early osteomyelitis and can also accurately depict the extent of disease as well as any associated abscess or soft-tissue extension without the risks associated with radiation exposure. MRI combines high-resolution anatomic delineation of the medullary space, cortex, and periosteum with high soft tissue contrast for detection of edema and fluid. Pre-operative MRI has been shown to reduce operative time and extent of surgical exposure in cases requiring surgical debridement. The earliest finding of osteomyelitis on MRI is bone marrow edema and T2 and STIR sequences are very important for detecting these early changes MRI is also sensitive for detection of periosteal elevation and the presence of a subperiosteal fluid collection or abscess .Distinguishing normal hematopoietic marrow from abnormal marrow can be challenging in certain situations because of the normal hematopoietic marrow often seen in the metaphyses in children. Normal hematopoietic marrow T1 signal should be hyperintense relative to muscle. If there is marrow infiltration or edema, the T1 signal is generally isointense or hypointense to muscle. Early diagnosis can be made based on technetium scintigraphy or MRI showing modification of the scapula body signal. MRI’s sensitivity (after fat saturation and gadolinium injection) is 88% and its speci-ficity is 93% MRI is the imaging modality of choice for the detection of osteomyelitis and associated infection of the extraosseous soft tissues. As such, the current best imaging approach for suspected osteomyelitis is radiography followed by MRI. Imaging chronic osteomyelitis is helpful to evaluate the extent of infection within bone and surrounding soft tissues, identification of an abscess, sequestrum and sinus tract . Sequestra of cortical bone appear as low signal on T1, T2 and STIR and do not enhance. Imaging findings of chronic osteomyelitis include Brodie abscess, thick periosteum, sequestrum/necrotic bone fragments, and cloaca/draining tract . Sequestra of cancellous bone also do not enhance but are relatively hyperintense to cortical sequestra on T1, T2 and STIR. Granulation tissue, soft tissue inflammation and sinus tracts are all T1 hypointense, T2 and STIR hyperintense and enhance with gadolinium.
REFERENCE: [1] Essaddam H, Hammou A. Ostéomyélites. Encycl Med Chir(Elsevier, Paris), Radiodiagnostic, neuroradiologie, appareillocomoteur, 31-218-B-10, 1998. p. 18. [2] Martini M, Daoud A, Saïghi-Bouaouina A, Ziani F, Burny F,Donkerwolcke M. Traitement chirurgical des ostéomyéliteshématogènes chroniques. Une série de 420 cas. Rev Chir Orthop1994;80:642—50. [3] Immerman. Osteomyelitis of the scapula. Case Rep Child MemlHosp Chic 1949;8(10):1491—3. [4] Fardon DF. Osteomyelitis of the scapula in an infant. Casereport Mo Med 1970;67(5):299—302. [5] Kovbasenko LA, Gordienko IuA, Kliatski ̆ı IuP. Osteomyelitisof the scapula and its treatment. Ortop Travmatol Protez1990;11:67—70. [6] Csillag A. Scapula resection due to osteomyelitis. Magy Seb1957;10(1):61—4.
Findings
Lytic area with surrounding bone marrow infiltration and adjoining soft tissue collection noted in inferior aspect of body of scapula. Collection measures 1.8 (cranio caudal) x 1 (anteroposterior) x 1.8 (transverse) cms. Lytic areas with adjoining collection shows diffusion restriction with low ADC values. STIR hyperintensity noted in infraspinatus muscle with subcutaneous edema noted adjacent to the lesion -reactive inflammatory changes. Subcentric right axillary lymph nodes noted.
Discussion
AOM is defined as an acute infection of the bone by a pathogenic bacterium, most often S. aureus, occurring forthe most part in children. The metaphysis of the long bones is the most frequent location of hematogenic AOM in children. Involvement of the short and flat bones is rare. Scapula involvement is usually in the body of the scapula and is exceptional. AOM occurs more frequently in boys often living in under-privileged areas with poor hygiene, promoting entry points for infection. CLINICAL FEATURES: The clinical picture of AOM of the scapula presents certain features and varies with the progressive stages of the disease. At onset, the symptoms are vague, comprising of unspecific clinical signs, sometimes misleading and possibly confused with osteoarthritis of the shoulder (poorly localized pain, painful mobilization of the shoulder explainedby reactive joint effusion). This inconclusive picture was responsible for the delay in diagnosis and management, lasting less than 12 h At a more advanced stage or at the disease stage, the extension of pus outside the scapula is rapid. This scapular periosteum explains the rapidity of the dissemination of the pus to the soft tissues contained under the infraspinatus muscle. The clinical manifestation is tumefaction of the posterior area of the scapula, indicating the location of theosteomyelitis and associating fever and pain upon mobilization of the scapula. At this stage, functional incapacity is total.At end-stage disease, the spread of pus into the scapula and the surrounding soft tissues causes frank spinal column disease (scoliotic posture) in association with severe tumefaction of the scapular region and alteration of the patient’s general condition IMAGING: First line modality radiography is useful for excluding other differential diagnoses such as trauma or tumor, however radiographs are insensitive for the detection of early osteomyelitis. Radiography may be normal in cases of osteomyelitis up to 14 d after the onset of infection and even then, only 20% of cases demonstrate radiographic abnormalities after this two-week delay. Additionally, the early radiographic findings, including soft tissue swelling, vague bony lucency, and periosteal reaction, may be subtle and may not reflect the true extent of disease. Triple-phase bone scintigraphy using 99mTc-methylene diphosphonate (99mTc-MDP) can demonstrate evidence of infection as soon as 24 h after onset and also has the advantage of being able to depict multiple sites of infection. Osteomyelitis typically manifests as increased radiotracer uptake on all phases (angiographic, blood pool, and delayed) of the triple-phase examination. However 99mTc-MDP scintigraphy is limited by poor anatomic detail and is insensitive for the detection of abscesses and extraosseous involvement. Furthermore, the sensitivity of 99mTc-MDP scintigraphy for the diagnosis of osteomyelitis, which in the past has been reported to be as high as 80%, may be decreasing with the increasing incidence of MRSA infections that tend to have significant soft-tissue involvement. MRI is both sensitive for the detection of early osteomyelitis and can also accurately depict the extent of disease as well as any associated abscess or soft-tissue extension without the risks associated with radiation exposure. MRI combines high-resolution anatomic delineation of the medullary space, cortex, and periosteum with high soft tissue contrast for detection of edema and fluid. Pre-operative MRI has been shown to reduce operative time and extent of surgical exposure in cases requiring surgical debridement. The earliest finding of osteomyelitis on MRI is bone marrow edema and T2 and STIR sequences are very important for detecting these early changes MRI is also sensitive for detection of periosteal elevation and the presence of a subperiosteal fluid collection or abscess .Distinguishing normal hematopoietic marrow from abnormal marrow can be challenging in certain situations because of the normal hematopoietic marrow often seen in the metaphyses in children. Normal hematopoietic marrow T1 signal should be hyperintense relative to muscle. If there is marrow infiltration or edema, the T1 signal is generally isointense or hypointense to muscle. Early diagnosis can be made based on technetium scintigraphy or MRI showing modification of the scapula body signal. MRI’s sensitivity (after fat saturation and gadolinium injection) is 88% and its speci-ficity is 93% MRI is the imaging modality of choice for the detection of osteomyelitis and associated infection of the extraosseous soft tissues. As such, the current best imaging approach for suspected osteomyelitis is radiography followed by MRI. Imaging chronic osteomyelitis is helpful to evaluate the extent of infection within bone and surrounding soft tissues, identification of an abscess, sequestrum and sinus tract . Sequestra of cortical bone appear as low signal on T1, T2 and STIR and do not enhance. Imaging findings of chronic osteomyelitis include Brodie abscess, thick periosteum, sequestrum/necrotic bone fragments, and cloaca/draining tract . Sequestra of cancellous bone also do not enhance but are relatively hyperintense to cortical sequestra on T1, T2 and STIR. Granulation tissue, soft tissue inflammation and sinus tracts are all T1 hypointense, T2 and STIR hyperintense and enhance with gadolinium.
REFERENCE: [1] Essaddam H, Hammou A. Ostéomyélites. Encycl Med Chir(Elsevier, Paris), Radiodiagnostic, neuroradiologie, appareillocomoteur, 31-218-B-10, 1998. p. 18. [2] Martini M, Daoud A, Saïghi-Bouaouina A, Ziani F, Burny F,Donkerwolcke M. Traitement chirurgical des ostéomyéliteshématogènes chroniques. Une série de 420 cas. Rev Chir Orthop1994;80:642—50. [3] Immerman. Osteomyelitis of the scapula. Case Rep Child MemlHosp Chic 1949;8(10):1491—3. [4] Fardon DF. Osteomyelitis of the scapula in an infant. Casereport Mo Med 1970;67(5):299—302. [5] Kovbasenko LA, Gordienko IuA, Kliatski ̆ı IuP. Osteomyelitisof the scapula and its treatment. Ortop Travmatol Protez1990;11:67—70. [6] Csillag A. Scapula resection due to osteomyelitis. Magy Seb1957;10(1):61—4.
Note:
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
If you feel you have answered rightly but cannot find your name in the above list, please call 09551942599.
Did you Know?
The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
If you feel you have answered rightly but cannot find your name in the above list, please call 09551942599.
Did you Know?
The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!