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Paper text:
a 30-year - old woman visited our clinic with pain on the right inguinal area and lateral aspect of the thigh , which spontaneously started 3 months ago and had become aggravated a week before .
the pain intensity in the visual analogue scale ( vas ) was about 80 of 100 .
she was experiencing right groin and thigh pain precipitated by walking , which made it difficult for her to walk normally .
lumbar magnetic resonance imaging ( mri ) done at a previous clinic showed otherwise normal ( fig .
, lumbar epidural steroid injection was done twice in combination with medications such as nonsteroidal anti - inflammatory drugs ( nsaids ) and muscle relaxants for 2 months ; however , these failed to improve her symptoms . she has even had a gynecological examination to rule out the disorder such as pelvic inflammatory disease , yield to normal . on physical examination
, she complained of tenderness over the right buttock and the anterolateral aspect of the thigh , as well as pain with flexion and internal rotation of the right hip joint .
both the straight - leg - raising test and the flip test were negative , as concordant with previous mri showing non - specific finding .
her body temperature was 36.3 , and laboratory findings such as complete blood count , erythrocyte sedimentation rate , c - reactive protein , and rheumatoid factor were normal .
we checked the hip radiograph and found a small amorphous calcification near the right anterior inferior iliac spine ( aiis)-the attachment site of the rectus tendon - suggesting calcific tendinitis of rectus femoris .
additionally , it was more visible in frog leg lateral views around the bony structure ( fig .
, calcification was noted in the right rectus femoris tendon , showing thickening with a small amount of fluid collection and edematous change of peripheral soft tissue ( fig .
, the transducer was positioned over the hip area to find the calcification . around the calcified lesion ,
we injected 5 ml of 1% of mepivacaine with 20 mg triamcinolone acetate , by using a 25 g 38-mm needle ( bd precisionglide needle ; becton dickinson medical , singapore ) with the short - axis in - plane technique . at 1 week intervals ,
the pain intensity started to decrease 2 days after the first injection and decreased to 0 - 10 of 100 in the vas 3 days after the second injection .
she returned to work in a pain - free state and after 6 weeks of follow - up , us image demonstrated decreased echogenicity of surrounding fat and also decreased amount of fluid collection with resolved symptom ( fig .
painful periarticular calcification is an acute inflammatory reaction , with pain , exquisite tenderness , local swelling , and redness .
it is most commonly seen within the rotator cuffs of the shoulder , although it can develop around the wrist , elbow , hip , knee , foot , and , rarely , in the neck . in the hip area , since the report of king and vanderpool   in 1967 , it has been rarely reported in the literature .
the exact etiology of the origin and resorption of the calcium deposits are not clearly understood , although several hypothetical mechanisms have been proposed .
the only disorders reported to be associated with the disease are chronic renal failure with persistent hemodialysis and diabetes mellitus .
however , historically , it was assumed that these deposits might have resulted from trauma around the involved joints , although no specific mechanism was elucidated . as repetitive trauma has been cited as a factor , especially in the shoulder region , tendinous tears of hip abductors
, the patient 's history of overuse of the hip abductors , in relation to her job that involves walking for 6 - 8 h a day , supported the above by describing repetitive trauma hypothesis .
it is known that periarticular calcific tendinitis can be classified as acute or chronic . in acute disease ,
most attacks last 2 weeks and the calcification disappears from radiographs at 4 weeks to 8 months post - onset . despite its self - limiting nature , if mild or moderate pain persists for 2 - 24 months after disease onset , the disease can be classified as chronic . in the hip , it is known that calcification occurs at three sites , namely the tendon of the gluteus medius , the bursa between the tendon of the gluteus medius and the greater trochanter , and the undersurface of the gluteus medius but not connected to the trochanter .
all locations can cause pain in the posterolateral aspect of the thigh that can simulate radicular pain from a herniated intervertebral disc .
hence , misdiagnosis is common and leads to a delay in treatment , as in our case ; this case was primarily managed under the diagnosis of a herniated lumbar disc , and the patient 's condition failed to improve .
the diagnosis is usually based on clinical suspicion and typical findings of plain radiography of the hip , locating calcific depositions in the tendon or bursa .
however , plain radiography can lead to misdiagnosis without additional diagnostic tools , as the bone , adjacent soft tissue , ligaments , and tendons around hip are arranged three - dimensionally . furthermore , if the calcification is very thin and small , and located in the posterior aspect , it is even more difficult to detect with only plain radiography , sometimes even in retrospective examinations .
the use of the " frog - leg position " while obtaining the plain x - ray image also supports this three - dimensional anatomical characteristic as it was also shown in our case . in the diagnosis of calcific tendinitis , computed tomography ( ct ) allows the best visualization and localization of proper lesions , as well as facilitates accurate injection , when required .
mri can be a useful tool to rule out other conditions , especially when the lesions involve soft tissue areas , and to show the severity of inflammation .
the real - time nature of ultrasonography has led to its use in both diagnostic and therapeutic procedures , as we did in our case .
ultrasonography is reliable for the detection and localization of calcifications ; however , it is unable to classify the pathophysiologic phase . therefore , clinical correlations and other radiographs are necessary to evaluate the disease .
the differential diagnoses of calcifications in the rectus femoris include osacetabuli , avulsion fractures , sesamoid bones in the rectus femoris , myositis ossificans , and malignancies , usually based on the size , characteristic ovoid shape , bony trabeculation , and painlessness of the ossicle .
the comet - tail appearance of the calcific deposit suggests that it lies within a tendon .
periarticular calcific tendinitis is widely accepted as a self - limited disease ; however , some refractory patients need treatment because the duration of symptoms varies from months to years .
the treatment options include conservative management such as rest , nsaids , local applications of heat and cold , arthroscopy , local surgical excision , and local steroid injection .
surgical excision is usually considered in case of long - lasting symptoms that are refractory to conservative treatment . among the conservative modalities ,
local steroid and anesthetic injections provide rapid and long - lasting pain relief and shorten the clinical course . however , their mechanisms of action are still unclear .
there are several literature reports in which a prompt diagnosis and early treatment with a local injection of corticosteroid under ct or fluoroscopy guidance were performed .
evaluating the general condition by using ultrasonography alone has some limitations ; however , it has the benefits of convenience and the lack of radiation exposure compared with ct or fluoroscopy .
there are insufficient cases reported in the literature in which ultrasonography was mainly used to treat calcific tendinitis in the hip area as this case , compared with that in the rotator cuff of the shoulder .
we performed local injection under ultrasound guidance because it has the advantage of real - time image acquisition , enabling fast and accurate diagnosis and treatment . especially in a hip lesion , although a tiny calcification can cause severe pain , a misdiagnosis is easily made , causing the disease to progress into the chronic state .
it is difficult to detect the calcification initially because of its rarity and the complex three - dimensional anatomic structure of the hip .
it could be more easily found in conjugation with valid radiographs of the patient 's pain area .
physicians should consider acute calcific tendinitis of the rectus femoris when making a differential diagnosis of hip pain , although it is a rare disease entity , as misdiagnosis leads to inappropriate treatment and delays in recovery .
we also recommend ultrasonography in the evaluation of hip pain , as it can be used as a rapid and effective diagnostic and therapeutic tool .
painful periarticular calcification most commonly occurs within the rotator cuff of the shoulder and rarely around the elbow , hip , foot , and neck . as acute inflammatory reaction develops , severe pain , exquisite tenderness , local swelling , and 
 limitation of motion with pain occur . in case of calcific tendinitis of the shoulder 
 , it can be easily diagnosed according to the symptoms and with x - ray . 
 however , in lesions of the hip , as it is a rare location and usually involves pain in the posterolateral aspect of the thigh , which can simulate radicular pain from a lumbar intervertebral disc , it could be difficult to diagnose . 
 hence , physicians usually focus on lumbar lesions ; therefore , misdiagnosis is common and leads to a delayed management . here , we report the case of a 30-year - old female patient with calcific tendinitis of the rectus femoris that was successfully managed with ultrasound - guided steroid injection . 
 this study offers knowledge about the rectus femoris calcification .