Low Bone Density In Sickle Cell Disease Is a Risk Factor in The Development Of Avascular Necrosis
Authors: Al-Jafar Hassan A. , Aytoglu Leena M , Al-Shemmari Jehan , Afzal Uzma , Al-Shemmari Iman , Al-Enizi Saud 
Published: October 2019

Introduction
Sickle cell disease (SCD) is a highly prevalent disorder in the world, specifically in the region of Kuwait. A wide population suffers from sickle cell anaemia. It has been known that bone involvement is one of the most common clinical manifestations of sickle cell disease, both in the acute setting such as painful vaso-occlusive crises, and as a chronic, progressive process such as osteoporosis ,osteopenia and avascular necrosis (AVN), which can develop due to the low bone mass and the deterioration of the micro architecture of bone tissue. In this ongoing project, we used the radionuclide imaging technique for bone and bone marrow scintigraphy and dual-energy x-ray absorptiometry (DEXA). We attempted a correlation between low bone density and the bone infarct for SCD, and identified if low bone density is a risk factor for the severity and development of osteonecrosis in an at-risk population of sickle cell patients.

Patients and Methods
A total of 13 sickle cell patients participated in this correlation study; 5 males and 8 females, ages ranged from 16 to 55 years with a mean age of 35.5 years. To meet the participant selection criteria, patients were selected if they were never prescribed bisphosphonates or any type of medicine used to help strengthen bones weakened by osteoporosis, nor exposed to any other AVN risk factors other than SCD. Subjects were subjected to a scintigraphy (3-phase bone SPECT-CT, bone marrow) and bone mineral density scan (BMD). All subjects consented to the study approved by the ethics committee. Bone scintigraphy was performed by Tc-99m MDP, HDP 20mCi / 70kg intravenous injection. Bone Marrow Scintigraphy was performed by Tc-99m sulfur or tin colloid, 10-15 mCi / 70 kg I.V, Bone with Bone marrow scintigraphy imaging is required to assess bone marrow infarction and infection. BMD dual-energy x-ray absorptiometry (DEXA) was also performed to indicate the reliably changes in bone mineral content of the lumbar spine and proximal femur. Statistical analysis involved descriptive statistics and chi-square test.

Results
According to the WHO criteria used; low bone density was found in 9/13 (69%) while normal bone density was found in 4/13 patients (31 %). Based upon the application of a chi-square test, all those subjects 9/9 having a low bone density were showing AVN in several severity and multiple sites of the skeleton; it was found that there is an association between low bone density and incidents of AVN. However, it is of importance to note that 2/4 (50%) of the normal bone density patients were found to have AVN.

Conclusion
The preliminary conclusion discern from this ongoing project suggest that low bone mineral density in SCD could be considered a risk factor contributing to the development of AVN.
We hypothesise that the severity of AVN develops due to the low bone mass and the deterioration of the micro architecture of bone tissue. The results have shown that low bone density is highly associated with osteonecrosis. Further case studies are needed to confirm or disprove these findings. The findings of this project could inspire new protocols required for effective management of this disease. Our findings could also potentially point out and diagnose new clinical cases, which would normally not be clinically suspected. We also speculate that increasing bone density of this patient population may decrease the severity and incidents of AVN.
References
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Disclosures:
No relevant conflicts of interest to declare.