Osteomyelitis & Avascular necrosis in sickle cell patientsAvascular necrosis of bone is a common problem in patients with sickle cell disease. Hip is the commonest joint driving patients to seek hip replacement.However this scenario can be complicated by osteomyelitis (bone infection) In this case report, we discuss how this combination was approached.
Case report – The patient was a 34 year old Nigerian male, one out of 6 siblings. All other siblings were normal. Both parents were haploid for sickle cell trait. He presented with severe avascular necrosis of the left hip needing a hip replacement. Work up included a complete blood count, ESR, Haemoglobin electrophoresis, blood culture, pre operative X-rays of the hip.
The ESR was elevated at 121 mm/ hr and his WBC count was 12,000/cu mm. Blood culture was negative. The x ray of the pelvis revealed avascular changes of both hips with secondary osteoarthritic changes. The proximal portion of the left femur showed a bone in bone appearance with some discontinuity seen in the region below the greater trochanter. An MRI with contrast was done. This showed a breach in the cortex with a bright signal intensity which was negative to fat suppression. There was edema in the surrounding tissues and an effusion was present in the hip joint. A CT guided biopsy was taken from the area and this drew a sample of yellowish fluid.
This fluid was set up for culture in two labs. One lab reported a negative culture and another lab reported a growth of scanty “coagulase negative staphylococcus.”With a near positive diagnosis of chronic osteomyelitis, the patient was taken up for an open debridement.
The hip was approached by a lateral approach with division of the vastus lateralis. A cavitary lesion was identified below the greater trochanter. It was debrided thoroughly and specimen sent for culture. Bio absorbable bone substitute of Calcium sulphate and antibiotic was packed inside the cavity to deliver a high local concentration of antibiotics, Vancomycin and Tobramycin. In addition intra venous infusion of Vancomycin and Clindamycin was started. The patient is making progress.
Discussion – This case helps to draw attention to the co existence of infection in sickle cell patients with avascular necrosis. Performance of a hip replacement without eradication of infection would have lead to disastrous results. This cautious approach can possibly eradicate infection and allow a safe hip replacement later on. Another aspect is the method of local antibiotic delivery. It is well known that intravenous antibiotics have poor tissue concentration in the affected bone. The prevalent method of local antibiotic delivery is combination of antibiotics with Bone cement (Poly methyl methacrylate). This comes in the form of Septopal beads which contain Gentamycin. This is impregnated into the affected area after an open operation; however this restricts the choice of antibiotics.
It requires another operation to remove the beads after 6 weeks. The main advantage of our technique is that the procedure achieves two purposes. Firstly it allows packing of the bony defect with a bone substitute. This substitute is resorbed over 60 days and osteogenesis occurs. Secondly antibiotics are delivered in high concentration locally for duration of three months. There is no need for a second operation to remove the beads as it is self absorbing.
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