evaluation of athletic hip pain routinely includes radiographs and magnetic resonance imaging ( mri ) .
computed tomography ( ct ) is applied at some centers and in certain clinical scenarios .
although mri (  arthrogram ) alone can clearly define changes to labrum or cartilage , osseous pathology may be underappreciated .
we present the case of an unrecognized osteoid osteoma in a patient with femoral acetabular impingement ( fai ) , cam morphology , and labral injury to emphasize the need to maintain a high index of clinical suspicion for this atypical cause of hip pain .
a 19-year - old male soccer player presented with hip pain unresponsive to non - steroidal anti - inflammatory drugs ( nsaids ) and physical therapy .
range of motion demonstrated 10 loss of internal rotation and muscle weakness ( 4+/5 hip flexion ) was present .
radiographs revealed cam morphology (  angle  =  74 ) with slight acetabular retroversion ( + cranial crossover sign ) ( fig .
( c ) ct of patient s right hip revealing osteoid osteoma at the lesser trochanter .
( d , e ) right hip ct scan in prone position with needle and radiofrequency ablation system at level of the osteoid osteoma . 
 
( c ) ct of patient s right hip revealing osteoid osteoma at the lesser trochanter .
( d , e ) right hip ct scan in prone position with needle and radiofrequency ablation system at level of the osteoid osteoma .
incidentally noted was the atypical appearance of the lesser trochanter attributed to lesser trochanter apophysitis .
mri arthrogram confirmed labral tear , partial thickness chondral injury with mild iliopsoas tendonitis with bone marrow edema at the lesser trochanter .
one year later the patient returned with buttock pain but denied anterior hip or groin pain .
repeat radiographs and mri arthrogram revealed well healed labrum and no evidence of heterotopic ossification .
ct with 3d reconstruction confirmed extent of bony resection but also clearly defined the osteoid osteoma nidus at the lesser trochanter ( fig .
salicylic acid failed to relieve pain and the patient was referred for radiofrequency ablation . under ct guidance , via a posterolateral approach , a 10-gauge bone biopsy needle was advanced to the nidus of the osteoid osteoma and through the reactive bone .
radiofrequency ablation was performed at the proximal and distal termini of the nidus and surrounding periosteum using a dfine , inc .
post - procedure recovery was uneventful and at 3 months the patient returned to all activities denying further hip pain .
our case emphasizes the value of advanced imaging in the setting of any incompletely defined bony changes of the proximal femur or acetabulum .
due to limitations of radiographs and mri , bony changes were inaccurately attributed to apophysitis versus osteoid osteoma .
we also draw attention to the complete lack of response to nsaids for the entirety of this patient s treatment .
recent literature has shown that clinical response to nsaids in osteoid osteoma may be overstated .
the lack of response certainly does not exclude osteoid osteoma as the cause of pain [ 3 , 4 ] .
the authors report no funding or external sponsors relevant in the authorship and publication of this clinical vignette formal conflict of interest statement : the authors report no conflict of interest or disclosures relevant in the authorship and publication of this clinical vignette .
 femoro - acetabular impingement is a common cause of hip pain in young athletes . 
 evaluation typically includes radiographs and magnetic resonance imaging . 
 it is important to appreciate uncommon diagnoses and the role of complimentary imaging . 
 this clinical vignette emphasizes the need complete imaging with ct in select case of atypical hip pain.we present a 19-year old soccer player who underwent seemingly successful arthroscopic fai surgery but returned with pain . 
 computed tomography ( ct ) revealed osteoid osteoma of the lesser trochanter . 
 the lesion was successfully treated with percutaneous ct guided radiofrequency ablation . 
INTRODUCTION
CASE REPORT
DISCUSSION/CONCLUSION
FUNDING
CONFLICT OF INTEREST