CASE HISTORY

A 45 year old white housewife presented to the rheumatology outpatient clinic with a three month history of bilateral ankle swelling with pain. This was treated with a diuretic, which reduced the swelling but not the pain. She had a little difficulty in climbing stairs, and her walking distance was reduced to 200 metres from her normal distance of 2 km. She took no alcohol and had a smoking history of 25 pack-years. She had a past history of hypothyroidism, had had a hysterectomy at the age of 35 for menorrhagia, and was receiving thyroxine and hormone replacement therapy. There was no past medical history of fracture or family history of metabolic or genetic bone diseases.

On examination she looked generally well, had a normal physical build, and was clinically euthyroid. Her weight was 80 kg and her body mass index 25 kg/m². She was normotensive and there were no abnormalities on systemic examination. She had pain on inversion and eversion of the subtalar joints bilaterally and her ankles were tender on palpation. She had bilateral valgus deformity at the ankle joint. There were no other joint abnormalities.

An x ray examination of her ankles showed bilateral distal tibia and fibula stress fractures (fig 1), and a bone isotope scan confirmed increased distribution of the stress fractures. Serum 25-hydroxyvitamin D, parathyroid hormone, thyroxine, thyroid stimulating hormone, urinary creatinine/dipyridinoline ratio, bone-specific sialoprotein, acute phase response proteins, serum protein electrophoresis, follicle stimulating hormone, luteinising hormone, and bone, liver, and kidney profiles were all normal. Bone density measurements were normal. Surgery was not recommended and she was advised to reduce her activity and rest and to use mechanical supports and analgesics; this resulted in successful symptomatic improvement. She was also advised to stop smoking.

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Figure 1

Healing distal fibular and tibial stress fractures.

DISCUSSION

Stress fractures can occur in almost any bone in the body, with the lower extremity weightbearing bones, especially the tibia, tarsals, and metatarsals, being most commonly affected.^1–3 Stress fractures are common overuse injuries that are often seen in athletes and military recruits. In a study of 320 athletes the most common bones injured were the tibia (49.1%) and the fibula (6.6%), with stress fractures bilateral in 16.6% of cases.⁴ Isolated reports have indicated the development of these fractures in patients with specific clinical conditions such as rheumatoid arthritis, systemic lupus erythematosus, and calcium pyrophosphate deposition.^5–9 Stress fractures occur when normal or physiological muscular activity stresses a bone that is deficient in mineral or elastic resistance.¹⁰ The exact mechanical phenomenon responsible for initiating stress fractures remains unclear. One theory suggests that excessive forces are transmitted to bone when surrounding muscles become fatigued.¹¹ Other factors, genetic, nutritional deficiencies, metabolic bone disorders, and hormonal imbalances, known to contribute to stress fractures were not present in our patient. The valgus deformity at the ankles,⁵ heavy smoking, and surgically induced amenorrhoea, might have been predisposing factors.^12,13

This case shows that pain and swelling localised to the ankles, associated with poor mobility, should alert doctors to the possibility of stress fractures in a patient with a history of heavy smoking, and amenorrhoea. Early recognition and diagnosis of stress fractures is important in helping to ameliorate the pain and disability they cause.