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Case discussion: calcaneal osteomyelitis masquerading as sever's disease in a 10 year old girl

Miss W is a 10 year old girl who presented to her local health practitioner with insidious onset of left heel pain. This was initially diagnosed as Sever's disease (calcaneal apophysitis). However, her pain increased dramatically over the following five days and Miss W was completely unable to weight bear which prompted a return to her General Practitioner for review. She also developed a temperature of 38.5. Her General Practitioner was concerned about Miss W's increasing pain, and called our rooms for advice. After speaking to the patient and her mother, we arranged an urgent admission to Frankston Public Hospital due to concerns about the potential for osteomyelitis. On examination, she had a large, erythematous area of soft tissue swelling at the level of the achilles tendon insertion (see below) and was extremely tender to palpation.


On admission to Frankston Public Hospital, Miss W underwent blood tests which demonstrated a C-reactive protein level (CRP) of 180mg/L and erythrocyte sedimentary rate (ESR) of 82mm/hr, and a white cell count of 13 x10^9/L with neutrophil shift. This is highly suggestive of bacterial infection.


An urgent MRI scan was obtained the evening of her presentation which demonstrated osteomyelitis at the calcaneal apophysis as well as a large abscess in the retrocalcaneal bursa.


Miss W urgently underwent an open debridement and washout of the calcaneum and retrocalcaneal space. Multiple intra-operative samples were taken. The achilles tendon was partially avulsed approximately 20% of the tendon insertion. Given the extensive infective debris and reluctance to insert any foreign material into ankle, plus limited tendon involvement, the partial avulsion was not repaired.


Miss W was commenced on intravenous antibiotics and her intra-operative samples grew staphylococcus aureus, sensitive to flucloxacillin. Three days later, she developed right knee pain. A repeat MRI scan demonstrated osteomyelitis of her femur, with no abscess formation.


Her femoral osteomyelitis was treated with ongoing antibiotic therapy, and initially Miss W improved. Her CRP dropped to 12 and she had 48 hours of being afebrile. However, whilst in hospital she suddenly became febrile again and also developed back pain.


At this stage, she was urgently transferred to the Royal Children's Hospital as Frankston public hospital does not have a paediatric spinal service should urgent spinal cord decompression be required.


Fortunately, subsequent scans did not demonstrate further foci for her multifocal osteomyelitis and she made a gradual improvement without further surgical intervention. She returned home, and her heel pain is gradually improving and her right knee pain has resolved. She will require a six week course in total of intravenous antibiotic therapy followed by a further six weeks of oral antibiotics. It is expected she will make a full recovery.


DISCUSSION

This is an extremely rare cause of heel pain which was initially thought to be Sever's disease. Red flags for Miss L's case included inability to weight bear, temperature and malaise. Multifocal osteomyelitis is also rare in otherwise healthy children, but can be treated successfully with antibiotics and surgical debridement, without long term sequelae if detected early.


All cases and clinical photographs have been shared following discussion and written permission from the patient and/or guardian.

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