Fracture of the neck of the femur and osteomalacia in pregnancy

Authors


* L. Bowyer, St George Hospital, Kogarah, Sydney, NSW 2177, Australia.

Case report

A 24 year old Muslim woman in full purdah, (no skin exposed in public, including veiling of the face and gloving of the hands), appeared at the antenatal clinic in a wheelchair at term. This was her third pregnancy, having received no antenatal care until consulting her general practitioner at 38 weeks of gestation by uncertain dates. She had had two previous vaginal deliveries, in January 1999 and May 2000, both at term. Her second pregnancy had been complicated by right-sided ‘sciatica’ in the third trimester, but her obstetric and medical history was otherwise unremarkable and she took no medications apart from iron supplements. Antenatal blood results were normal as was an ultrasound scan. She had complained to her general practitioner of severe right-sided leg pain on mobilising. Doppler ultrasound examination of her legs was normal. No further examination or investigation of her leg was undertaken at the antenatal clinic. The pain, which continued to confine her to a wheelchair, was again thought to be due to ‘sciatica’.

At 42 weeks of gestation by a late ultrasound scan she was admitted to the delivery suite in early labour. Her labour progressed slowly over the following 22 hours and the fetal head failed to engage into the pelvis. The woman agreed to a caesarean section, resulting in the delivery of a healthy boy weighing 4285 g. On the fourth day after her caesarean section, it was noted that the woman walked with extreme difficulty. On examination, the right quadriceps and gastrocnemius muscles were wasted and there was weakness of the muscles of the right hip. Her reflexes were normal and there was no loss of sensation. She had a markedly abnormal gait. Plain X-rays of her pelvis and right hip showed a fracture of the neck of her right femur, with significant displacement. In addition, there were subacute healing fractures of the left superior and inferior pubic rami, a sclerotic area of the right ischium suggestive of an old healing fracture and generally osteopenic bones with subcortical tunnelling and thinning of the cortex.

The results of bone mineral densitometry were in keeping with established osteoporosis. The results of bone biochemistry are shown in Table 1. A bone scan showed abnormal focal uptake throughout the ribs bilaterally, the intertrochanteric area of the right femur, the neck of the left femur medially and the distal part of the left femur, in keeping with multiple fractures. Bone marrow biopsy performed 16 days postnatally was normal, showing normal cellularity, a little patchy endosteal fibrosis and some bone resorption and remodelling with groups of osteoclasts. Screening for the malabsorption syndrome found a high IgG gliadin but normal IgA and endomysial antibody.

Table 1.  Bone biochemistry and bone mineral densitometry results.
 Bone biochemistryNormal rangeLikely significance
  1. ALP = alkaline phosphatase.

  2. PTH = parathormone.

ALP (five days postpartum, U/L)30038–126Uncertain (often high in pregnancy)
Serum calcium (mmol/L)2.232.25–2.58Slightly low
Serum phosphate (mmol/L)0.610.8–1.5Response to ↑PTH
25-hydrocalciferal (nmol/L)<1039–140Clear deficiency
Parathyroid hormone (pmol/L)22.31.1–6.9Secondary hyperparathyroidism
Osteocalcin (μg/L)<4.26.8–32.3Poor laying down of bone matrix
 Bone density (g/cm2)% Young adultT Score
Lumbar spine0.7361−3.9
Left femoral neck0.6061−3.2

A diagnosis of osteomalacia secondary to vitamin D deficiency was made, with superimposed osteoporosis and possibly a component of malabsorption (the woman preferred not to undergo further gastrointestinal investigations). Her vitamin D deficiency was thought to be a combination of lack of exposure to sunlight (she had been wearing full purdah since arrival in Australia four years previously), poor nutrition and possible malabsorption. She denied the possibility of physical abuse when questioned through a female interpreter by a female doctor without her husband present, and there were no marks on her body to suggest this alternative diagnosis.

Closed reduction of the right hip fracture and insertion of three cannulated screws was performed by the orthopaedic team. The woman was discharged 23 days postnatally partially weight-bearing on her left leg (the bone scan suggested incipient left-sided femoral fracture) and still non-weight-bearing on her right leg. She was given 600,000 units of vitamin D intramuscularly before her discharge. She went home taking ergocalciferol 1000 U twice daily and calcium 600 mg twice daily. Her baby showed no signs of neonatal hypocalcaemia and had normal alkaline phosphatase but low vitamin D levels.

Discussion

Although symptomatic osteomalacia in pregnancy has been reported previously, we believe this is the first case of fractured neck of femur in pregnancy secondary to osteomalacia. The fetus at term contains approximately 30 g of calcium and lactating women excrete approximately 210 mg/day of calcium in breast milk1. Pregnancy and lactation, therefore, are a time of increased requirements for calcium and vitamin D. Vitamin D may be obtained in the mother either through the direct action of sunlight on the skin or in the diet, animal products (especially eggs and fish) being the richest sources.

Women thought to be particularly at risk of vitamin D deficiency are dark skinned, vegetarians living at high latitudes. Studies of pregnant Asian women in England and Norway have shown rates of vitamin D insufficiency (25-hydroxycalciferal <10 ng/mL) during pregnancy of 53% of 43 women and 83% of 36 women, respectively2,3. Neither of these studies reported osteomalacia, but osteomalacia in pregnancy has otherwise been reported in Asian immigrants to Britain4. There are also case series of children with symptomatic vitamin D deficiency, a common association with maternal osteomalacia. These children have rickets or hypocalcaemic seizures. In a series of 55 infants with vitamin D deficiency, Nozza and Rodda5 found 25 of the 31 mothers tested (81%) also had vitamin D deficiency.

Women who do not expose themselves to sunlight for religious or cultural reasons are at risk of vitamin D deficiency irrespective of climate. A study of 119 term pregnant women in Saudi Arabia found vitamin D deficiency in 25%6. A recent study from Israel compared vitamin D levels in 156 orthodox mothers (who wear concealing clothing) with 185 non-orthodox mothers, and found vitamin D deficiency in 37.2% and 13%, respectively7. The woman in our case had a deficiency of sunlight and deficiency of nutritional vitamin D. This case is a reminder that a substantial number of pregnant women, living in high or low latitudes, are at risk of vitamin D deficiency. In a recent Australian study8, 80% of 82 veiled or dark-skinned pregnant women were found to have vitamin D deficiency.

The clinical effects of vitamin D supplementation in pregnancy are uncertain. Although trials have shown that supplementation in the third trimester leads to a significant rise in serum 25-hydrocalciferal9,10, the Cochrane Review on supplementation with vitamin D found only two trials involving 232 women fulfilling the inclusion criteria for the systematic review. The conclusion was that there is insufficient clinical evidence to justify supplementation with vitamin D11. We recommend that further randomised trials should be carried out.

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