Case Report Osteoporosis - Springer Link

3 downloads 0 Views 139KB Size Report
is so-called insufficiency fracture due to transient osteoporosis of the sacrum associated with pregnancy or so-called fatigue fracture due to unaccustomed stress.
Osteoporos Int (1999) 10:91–93 ß 1999 International Osteoporosis Foundation and National Osteoporosis Foundation

Osteoporosis International

Case Report Bilateral Fracture of the Sacrum Associated with Pregnancy: A Case Report L. Schmid1, C. Pfirrmann2, T. Hess3 and U. Schlumpf1 1 3

Rheumatologische Abteilung, Medizinische Klinik, Kantonsspital Luzern; 2Ro¨ntgeninstitut, Kantonsspital Luzern; and Frauenklinik, Kantonsspital Luzern, Luzern, Switzerland

Abstract. We describe a 33-year-old woman with a bilateral fracture of the sacrum associated with pregnancy. Dual-energy X-ray absorptiometry of the lumbar spine and femoral neck showed normal bone mineral density, whereas bilateral osteopenic areas in the massae laterales were demonstrated by the initial CTscan. The question remains whether the correct diagnosis is so-called insufficiency fracture due to transient osteoporosis of the sacrum associated with pregnancy or so-called fatigue fracture due to unaccustomed stress related to rapid and excessive weight gain in the last trimester of pregnancy. Keywords: Pregnancy; Sacrum fracture

Introduction Stress fractures are either fatigue fractures occurring in a bone with normal resistance under unaccustomed stress, or insufficiency fractures occurring in a weakened bone under normal stress. Fractures of the sacrum are now known to be much more frequent in involutional osteoporosis than formerly believed [1,2]. Sacrum fractures usually extend in a vertical direction parallel to the sacroiliac joint. Pregnancy-associated osteoporosis is a rare condition during the last trimester of pregnancy or immediately post-partum. It shows a reduction in the bone mineral density (BMD), especially in the vertebral column. The pathogenesis of pregnancy-associated osteoporosis is Correspondence and offprint requests to: Dr L. Schmid, Rheumatologische Abteilung, Medizinische Klinik, CH-6000 Luzern 16, Switzerland. Tel: +41 41 205 11 11. Fax: +41 41 205 51 09.

unknown and even the question of whether pregnancy is simply an aggravating situation disclosing a latent disease or a direct aetiologic factor remains undecided. The situation resembles juvenile osteoporosis, especially concerning the reversibility of the disease and the preferred involvement of the vertebrae. Decreased 1,25-dihydroxyvitamin D3 (1,25 (OH)2D3) and calcitonin levels are discussed as causes for a failure in calcium homeostasis, and the effects of cytokines on bone remodeling in pregnancy and osteoporosis are the subject of increasing interest [3,4]. Transient osteoporosis of the hip in pregnancy occurs usually in the third trimester without affecting the total BMD. Rarely bones other than the femoral head are involved. The etiology of this condition remains uncertain; it may be neurovascular and perhaps related to reflex sympathetic dystrophy. Almost all reported cases have been in women in their late twenties or early to mid-thirties [5–7].

Case Report A 33-year-old healthy Caucasian woman developed pain in the left buttock in the upright standing and walking position during the last trimester of her second pregnancy. After an uncomplicated cesarean section, the described pain increased within a few days and at the same time a lesser pain affected the right buttock. Finally the condition made it impossible for the patient to walk without crutches, whereas the pain showed prompt relief under bedrest. The pregnancy was uncomplicated (in particular there was no history of pre-eclampsia, gestational diabetes or other metabolic disorders) except for a maximal gain in body weight of

92

22 kg. No prolonged bedrest or immobilization occurred and we also did not find any family history of osteoporosis. Daily calcium intake was more than 1 g; vitamin D3 was supplemented with 400 IU daily throughout pregnancy. Except for 6 days of lowmolecular-weight heparin (5000 IU/day) immediately after cesarean delivery, the patient did not receive heparin or other medication affecting bone metabolism. Smoking was ceased 3 years previously and there was no regular alcohol consumption either before or during pregnancy. Cesarean section was performed because the patient refused to have a vaginal delivery (after breech presentation of the baby in the first pregnancy with a cesarean delivery). At the first examination in our outpatient department the patient presented with an extreme pain in her left buttock radiating to the dorsolateral aspect of the thigh and calf. Her body weight at the time of examination was 81 kg and height was 174 cm, corresponding to a body mass index of 27. When trying to walk she presented a striking limp with a positive Trendelenburg sign accentuated on the left side. Mennell’s sign was positive and the sacroiliac joint region was tender on pressure. Otherwise the physical examination was normal except for an insufficiency of postural muscles and a slight peripheral hypermobility. Conventional radiographs of the sacrum and the pelvis showed normal findings. A radionuclide bone scan with 99m Tc revealed striking longitudinal activity in the massa lateralis on the left, and less pronounced on the right side, in the blood pool as well as in the late phase (Fig. 1). Magnetic resonance imaging (MRI) was performed to exclude acute arthritis of the sacroiliac joint. T2weighted images (TR = 2500–3500 ms, TE = 103 ms)

Fig. 1. Radionuclide bone scan at the time of initial presentation. Delayed scans of the pelvis show a marked increase in activity longitudinally in the left massa lateralis of the sacrum, less pronounced on the right side.

L. Schmid et al.

as well as fat-saturated images after gadolinium-DTPA administration showed a band of increased signal intensity with marked enhancement in the left massa lateralis of the sacrum. On the right side a similar, but less prominent abnormality was observed. T1-weighted images (TR = 360–465 ms, TE = 15 ms) showed a band of signal loss in the same areas. The sacroiliac joints were normal. A high-resolution computed tomography (CT) scan of the sacrum (2 mm slices) was performed, revealing osteopenia on both sides in the massae laterales and a hardly visible fissure of the cortical bone on the anterior aspect of os sacrum. Dual-energy X-ray absorptiometry (DXA) showed normal T-scores in the lumbar spine (+0.477 on average), femoral neck (+1.28), Ward’s triangle (+1.59) and trochanteric region (+0.76). Laboratory findings showed normal values of serum calcium (2.46 mmol/l), albumin (51 g/l), phosphorus (1.22 mmol/l), magnesium (0.7 mmol/l), creatinine (81 mmol/l), liver enzymes, cholestatic parameters, ESR, CRP, blood count, cortisol, thyroid and parathyroid hormone (intact PTH 30 pg/ml). Urinary excretion of calcium was below normal (1.21 mmol/l). 25-Hydroxyvitamin D3 was in the normal range (83 nmol/l), but 1,25(OH)2D3 was slightly below normal (57 pmol/l). Alkaline phosphatase was slightly elevated (141 U/l). The deoxypyridinoline/creatinine ratio was 20.9 (normal range 9.4-20).

Clinical and Radiologic Follow-up After 3 weeks of treatment with 200 IU of calcitonin (lactation was stopped) and initial bedrest for 2 weeks the patient was able to walk without pain using crutches. After 2 months the pain disappeared completely and the patient could perform normal daily activities.

Fig. 2. MRI at 4 months follow-up. T1-weighted (TR = 2500–360– 465 ms, TE = 15 ms) coronal MR images reveal thin hypointense lines representing sclerosed fracture lines.

Bilateral Fracture of the Sacrum in Pregnancy

Fig. 3. CT scan at 4 months follow-up. Scans show marked bilateral sclerosis and callus formation.

An MRI examination 4 months later showed complete normalization of the edematous changes and no further enhancement. The bone had slight irregularities and the appearance of sclerosis. On both sides of the sacrum a thin line of low intensity represented the healed fractures (Fig. 2). A follow-up CT scan revealed sclerosis of cancellous bone in both massae laterales and callus formation at the anterior aspect of the sacrum (Fig. 3).

Discussion The differential diagnosis of buttock pain in the postpartum period includes at least the dysfunction of the sacroiliac joint and a sacroiliitis, as well as an irritation of the sciatic nerve. To the best of our knowledge, only two other case reports have described a fracture of the sacrum associated with pregnancy. The first was a 33-year-old woman who developed a fracture of the right sacrum post-partum [8] after an uneventful pregnancy without any notable features except a gain in weight of 18 kg (no information was given about biologic markers or BMD). The second report described a 29-year-old woman with an insufficiency fracture of the left sacrum during the seventh month of pregnancy [9]. This patient had received heparin after a miscarriage in a former pregnancy and showed a decreased BMD in the lumbar spine and femoral neck. Our described patient showed a bilateral fracture of the sacrum without any abnormality in BMD of the lumbar spine and femoral neck. These findings argue against a classical osteoporosis of pregnancy. An initial CT scan showed localized osteopenia of of the sacrum.

93

The etiology and the significance of this osteopenia remains unclear. If it were to correspond to a transient regional osteoporosis of the sacrum, the fracture would be an insufficiency fracture. However, we can not completely exclude this osteopenia being a secondary phenomenon (a fracture healing under conditions that do not fulfill the requirements of rigid fixation is associated with osteoclastic resorption induced by micromovement). However, the osteopenia documented in the initial CT scan was larger than just a widening of the gap and it also seems questionable whether the rapid and marked gain of weight in our patient could cause a fatigue fracture. The minimal deficiency in 1,25(OH)2D3 in our patient represents a finding of doubtful significance, although the absence of a physiologic increase in 1,25(OH)2D3 during pregnancy and lactation has been observed in several cases of osteoporosis of pregnancy [10]. It also seems unlikely that the fracture was caused by immobilization, because of the absence of hypercalciuria, hypercalcemia and hypoparathyroidism. Measurement of 25-hydroxyvitamin D3 and 1,25(OH)2D3 5 months after delivery showed high normal values, which makes a true diagnosis of hydroxylase deficiency unlikely. In conclusion, sacrum fractures are rare conditions but should be included in the differential diagnosis of posterior pelvic pain during pregnancy and in the early post-partum period. The MRI appearance of this lesion is nonspecific and the differential diagnosis on T1weighted lesions must exclude infection and malignancy. The radiologic course with sclerosis of the initial edematous and osteopenic zone (seen particularly on the CT scan) is classical and can help to establish the diagnosis in initially doubtful cases.

References 1. Renner JB. Pelvic insufficiency fractures. Arthritis Rheum 1990;33:426–30. 2. Crayton HE, Bell CL, De Smet AA. Sacral insufficiency fractures. Semin Arthritis Rheum 1991;20:378–84. 3. Khovidhunkit W, Epstein S. Osteoporosis in pregnancy. Osteoporos Int 1996;6:345–54. 4. Dunne F, Walters B, Marshall T, Heath DA. Pregnancy associated osteoporosis. Clin Endocrinol 1993;39:487–90. 5. Bramlett KW, Killian JT, Nasca RJ, Daniel WW. Transient osteoporosis. Clin Orthop Rel Res 1987;222:197–202. 6. Lakhanpal S, Ginsburg W, Luthra H, Hunder G. Transient regional osteoporosis. Ann Intern Med 1987;106:444–50. 7. Brodell JD, Burns JE, Heiple KG. Transient osteoporosis of the hip in pregnancy. J Bone Joint Surg Am 1989;71: 1252–7. 8. Hoang TA, Nguyen TH, Daffner RH, Lupetin AR, Deeb ZL. Case report 491. Skeletal Radiol 1988;17:364-7. 9. Breuil V, Brocq O, Euller L, Grimaud A. Insufficiency fracture of the sacrum revealing a pregnancy associated osteoporosis. Ann Rheum Dis 1997;56:278. 10. Smith R, Winearls CG, Stevenson JC, Woods CG. Osteoporosis of pregnancy. Lancet 1985;i:1178–80. Received for publication 5 August 1998 Accepted in revised form 27 November 1998