Bilateral hip pain

Abstract

In October, 2008, a 40-year-old man was referred to our hospital because of pain in his right groin, which had started a few days after he fell on his back at work 10 days earlier. He had mild asthma, which was treated with an occasional dose of inhaled broncholytics. On physical examination, he had right groin tenderness, and pain that was provoked by weight-bearing. A pelvic radiograph was normal. A tendon or muscle injury was suspected, and ultrasonography suggested a partial rupture of the rectus femoris muscle. MRI was planned as an elective outpatient procedure to rule out a total rupture of the tendon. A month after the onset of symptoms, the pain on weight bearing in the right groin had decreased but not resolved. He had also started to have pain in the left groin, and on examination, pain on rotation of both hip joints. MRI showed bilateral insuffi ciency fractures of the femoral necks (fi gure). Although he denied any regular recreational sports activities, his new job as a delivery-van driver required a lot of climbing. He had no dietary restrictions. Elderly relatives of our patient had a history of osteoporosis and osteopenia. Our patient was asked to restrict weight-bearing. A dual-energy x-ray absorptiometry scan showed that his bone mineral density was osteopenic at the lumbar spine and right femoral neck. The left femoral neck showed osteoporotic values (0·706 g/cm2; T score –2·8; Z score –2·4). Biochemistry tests for parathyroid and coeliac disease excluded secondary reasons for osteoporosis. His serum 25-hydroxyvitamin D(3) concentration was 33 nmol/L (normal > 40nmol/L). He was referred for iliac crest bone biopsy after tetracycline double-labelling. Low trabecular bone volume was found by histomorphometry (BV/TV 9·0%), and confi rmed by microcomputed tomography (9·9%). The turnover rate was normal as shown by normal amounts of formation and erosion surfaces (OV/BV 1·5%, OS/BS 14·2%, ES/BS 7·0%). The osteoblast and osteoclast surfaces were normal (Ob.S/BS 1·9%, Oc.S/BS 0·0%) as was the amount of mineralising surface (MS/BS 8·0%), but the mineral apposition rate was slightly low (0·28 μm/day). The results were consistent with normal-turnover osteoporosis. In a repeat MRI 10 weeks after the beginning of the symptoms bone oedema was diminished and in the follow up visit in March 2009, the fractures had clinically healed. His osteoporosis was treated with daily calcium 1000 mg, vitamin D 800 IU supplementation and weekly alendronate 70 mg. When last seen in June, 2010, he was asymptomatic. The diagnosis of insuffi ciency fracture of the femoral neck is commonly missed in clinical practice. The diagnostic algorithm should include, but not be restricted to radiographs. A normal radiograph does not rule out insuffi ciency fractures, as our patient’s case demonstrates. Osteoporosis may in itself be an aetiological factor in the case of insuffi ciency fractures. Long term bisphosphonate therapy has been linked with insuffi ciency fracturees in the femoral shaft. However, our patient’s fractures did not show features of such atypical fractures.Although secondary osteoporosis should be considered in young male patients, primary osteoporosis remains the diagnosis for up to half of patients. In the case of insuffi ciency fractures, the possibility of bilateral injury should be considered. Early diagnosis is warranted because untreated insuffi ciency fracture of the femoral neck can lead to a displaced fracture.