this report describes a case of a 14 year old boy who presented with a clinical and radiological picture of osteoid osteoma of proximal femur but found to have a brodie 's abscess on histology and culture .
it describes the clinical spectrum of subacute osteomyelitis , its unusual mri features and the importance of obtaining a histological diagnosis before definitive treatment .
brodie 's abscess usually presents as a diagnostic dilemma and clinically mimics various benign and malignant conditions ( 13 ) .
brodie 's abscess or primary subacute osteomyelitis is known to occur more commonly in children .
metaphyseal lesions are the most common and occur most commonly in proximal tibia ( 2 , 6 , 7 ) .
the neck and the surrounding metaphyseal region of proximal femur is a less commonly affected site ( 8 , 9 ) .
roberts et al described a classification of brodie 's abscess depending on their anatomical location and their resemblance to specific neoplasms .
type 1 b represents a metaphyseal lesion comprising a radiolucent area with a sclerotic margin along with periosteal reaction ( 10 ) .
this report describes a case of a 14 year old boy who presented with a clinical and radiological picture of osteoid osteoma of proximal femur but found to have a brodie 's abscess on histology and culture .
it describes the clinical spectrum of subacute osteomyelitis , its unusual mri features and the importance of obtaining a histological diagnosis before treatment .
we report a case of a 14 years old boy who came to our clinic , i.e. the out - patient department of a tertiary care referral center in india , in february 2014 , with complaints of pain in his left hip .
the pain was insidious in onset , dull aching in nature , mild to moderate in severity , more during the nights and was present for the last three months .
physically , he was able to carry out all his daily activities including squatting with some discomfort but was not able to carry out strenuous activities like running and jumping .
the patient did not complain of any other constitutional symptoms like fever , weight loss , decreased appetite or night sweats . on clinical examination ,
the patient had tenderness anteriorly over the left hip joint , with no local signs of infection .
passive movements over the left hip , specifically flexion , adduction and internal rotation were restricted and painful terminally as compared to the right side .
there was no limb length discrepancy ; however , the patient walked with an antalgic limp .
the examination of the right hip , the left knee and the spine showed no positive findings .
it included a total wbc count of 8,400 , differential neutrophil count of 70% and lymphocyte count of 26% .
the esr ( erythrocyte sedimentation rate ) after 1 hour was 26 and crp ( c- reactive protein ) was 2.8
a true size plain radiograph ap view revealed an osteolytic area of around 1 cm diameter in the calcar region surrounded by osteosclerotic margins along with periosteal reaction along the medial aspect of neck and metaphysis ( figure 1 ) .
a true size ap radiograph of a 14 year old male with a radiolucent lesion in the calcar region of the left proximal femur with surrounding sclerosis and periosteal reaction after thorough clinical examination and routine investigations , a provisional diagnosis of an osteoid osteoma was considered , and the patient was further subjected to magnetic resonance imaging ( mri ) to substantiate this .
mr imaging showed a lesion measuring around 12  8 mm with a central nidus which was hypointense on t1-weighted images and was hyperintense on t - weighted images ( figures 2 & 3 ) .
the clinical and radiological picture was quite confirmatory for the diagnosis of osteoid osteoma , and it was imperative to treat it with radio frequency ablation .
thus , the patient underwent a curettage procedure , which was done through a lateral approach . under image guidance
, a 2 mm k - wire was directed towards the osteolytic lesion over which a 5 mm cannulated drill was passed and the cavitary lesion was opened ( figure 4 ) .
the track in the outer femoral cortex was widened , and a curette was passed through the tract into the lesion , and the lesion was curetted out and the tissue obtained was sent for histopathology and microbial culture .
the histopathology revealed granulation tissue with both acute and chronic inflammatory cells with areas of dead bony tissue , and the culture grew staphylococcus aureus .
these findings led to the final diagnosis of brodie 's abscess in contrast to our provisional diagnosis , which was based on clinical examination and radiological features , emphasizing the importance of culture and histology of every suspected bony neoplasm .
the patient was managed with antibiotics based on the sensitivity , and he was allowed only partial weight bearing with support for the next 6 weeks . at 6 months ' followup , the patient was asymptomatic and could do all the activities which were restricted previously .
a mri scan was repeated at 6 months followup , which did not show any signs of persistent disease .
t1 weighted axial mr image showing a hypointense nidus surrounded by a zone of hyperintensity and bone oedema t2 weighted axial image showing the incresed intensity of the nidus as compared to t1 image intra - operative lateral radiograph showing the k - wire placed in the lesion opening the cavity
subacute osteomyelitis has not been strictly defined , but most people agree to its definition as any infectious process in the bony tissue persisting for more than 2 weeks without any symptoms of acute illness ( 5 , 6 ) .
the infection persists in subacute form either due to low virulence of the organism or good host resistance or because of inappropriate use of antibiotics .
the disease occurring due to two earlier reasons is termed as primary subacute osteomyelitis , and is mostly due to haematogenous seeding ( 5 ) .
occurring predominantly in young adult males with a history of trauma , recurrent pain and localized tenderness are common presenting symptoms , and are usually associated with fever , chills or malaise due to systemic infection ( 5 , 6 ) . however , in a significant number of patients , localized pain or vague symptoms ranging from 1 month to 3 years are the only manifestations of a brodie 's abscess .
radiographically , brodie 's abscess appears as a radiolucent lesion , usually eccentric , varying in size from as small as 1 cm to as large as occupying the entire diameter of the bone , with marginal sclerosis and some periosteal thickening ( 8) . on computed tomography , a sinus tract can be visualized in a few cases .
a  penumbra sign  has been described on t1-weighted mri in cases of brodie 's abscess .
it is a discrete zone of transition of relatively hyperintense signal between the intermediate to low signal intensity abscess cavity and the adjacent oedematous or sclerotic bone marrow on unenhanced t1-weighted imaging .
brodie 's abscess is known to mimic osteoid osteoma , more so in the metaphysis of tibia or femur ( 13 ) .
only a few cases have been reported which describe the diagnostic dilemma in the neck of femur ( 7 ) .
the case reported in this paper talks about a brodie 's abscess in the neck of femur , specifically in the calcar region which masquerades an osteoid osteoma .
osteoid osteoma occurs most commonly in the second decade and presents a typical history as was in this case.(13 , 5,6 ) .
radiographically , a typical osteoid osteoma appears as a dense sclerotic area surrounding a radiolucent nidus and does not usually exceed a size of 15 mm . on computed tomography ,
t1-weighted images ; the nidus demonstrates low to intermediate signal intensity , though on t2-weighted images , the nidus intensity is increased ( 9,10 ) .
the misleading appearance of osteoid osteoma on ct or mri often leads to the diagnosis of osteomyelitis .
although both the entities are quite similar in their clinical and radiological presentation , the incidence of brodie 's abscess is lower than that of osteoid osteoma ( 7 ) .
the presence of sinus tract on computed tomography is almost diagnostic for brodie 's abscess .
the nidus of osteoid osteoma is centrally placed in contrast to brodie 's abscess where sequestration is eccentrically placed .
labeled scintigraphy has also been of use to distinguish the two but has been reported to be non - specific ( 9 , 10 ) .
this case re - emphasizes the fact that a detailed histological and microbiological work up is essential before subjecting the patient to definitive treatment .
microbial cultures of tissue specimen from brodie 's abscess are inconsistently positive for any organism ( 3 ) .
cultures , when positive , usually grow staphylococcus aureus , as in this case ; some other organisms have also been reported ( 2 , 3 , 7 ) . the unusual location of the abscess in the neck of femur often results in incomplete excision of the diseased tissue , which further leads to recurrence .
moreover , it has been recommended that abscess in the femoral neck approached from the side where they are closest to cortex to minimize bone resection ( 6 ) .
however , in this case , as the abscess was located in the calcar region , it was decided to approach it laterally , thereby avoiding any disruption in the medial calcar . in the light of the above discussion
, it can be concluded that brodie 's abscess in femoral neck is a rare entity and can mimic osteoid osteoma clinico - radiologically .
this case further substantiates the old dictum  culture every tumor and biopsy every infection before definitive treatment  .
 backgroundbrodie 's abscess usually presents as a diagnostic dilemma resulting in a diagnostic delay . 
 it mimics various benign and malignant conditions both clinically and radiologically.case detailsthis report describes a case of a 14 year old boy who presented with a clinical and radiological picture of osteoid osteoma of proximal femur but found to have a brodie 's abscess on histology and culture.conclusionit describes the clinical spectrum of subacute osteomyelitis , its unusual mri features and the importance of obtaining a histological diagnosis before definitive treatment . 
Background
Case Details
Conclusion
Introduction
Case Report
Discussion