Anatomical Variation in South Indian Population in the Parietal Bones: Wormian Bone/Inca Bone

Background of the Study: Accessory bone found in the human skull bone between squamous part of parietal and in between lambda suture is called inca bone or wormian bone .A total of 100 dried skulls were examined to know the anatomical variations of the inter parietal bone. This variants of the bones are considered as normal. This knowledge of the study very useful for the neurosurgeon, orthopedic surgeons and forensic experts for their clinical intervention.

The presence of Wormian bones increases the fracture resistance of equine cranial bone

Wormian (intrasutural) bones are small, irregular bones, that are found in the cranial sutures of the skull. The occurrence of Wormian bones in human skulls has been well documented but few studies have detected the presence of such bones in domestic animals. Although some research has linked the presence of Wormian bones to bone pathology, its anatomical significance in healthy individuals is not known. To the best of our knowledge, no previous study has examined the biomechanical features of Wormian bone. This study uses microCT imaging of the parietal bone region to determine the frequency of occurrence of Wormian bones in horse skulls and, through 3-point bending tests, to calculate the mechanical differences that result from the presence of such bones. In addition, bone properties such as bone mineral density (BMD) and stiffness were measured and analysed to determine the influence of Wormian bone. Our findings on 54 specimens taken from 10 horses (ages ranging from 4 to 29 years) showed that Wormian bone was present in 70% of subjects and that its occurrence was unrelated to age or sex. 3-point bend tests revealed that the stiffness normalised by cross section area (P = 0.038) was lower in samples where Wormian bone was present. An idealised Finite Element simulation confirmed that the presence of Wormian bone reduced the maximum stress and strain, as well as their distribution throughout the sample. We consequently conclude that the presence of Wormian bones, which are confined to the calvaria, increase the compliance of the bone and reduce the likelihood of skull fracture. As all skull samples were collected from a local abattoir, ethical approval was not required for this work.

A STUDY ON THE OCCURRENCE OF WORMIAN BONES IN ADULT DRY SKULLS

Background: Sutural or wormian bones are islands of bone that are commonly found in the sutures of the skull mainly along the lambdoid suture. These sutural bones which are irregular in size, shape and number may arise from separate centres of ossification. The prior knowledge about the Wormian bones is important because they are present in normal individuals as well as in various disorders such as osteogenesis imperfect, rickets, etc. Aim: To study the occurence of wormian bones in adult dry skulls Materials and Methods: The present study was carried out on 95 adult dry human skulls in the department of Anatomy, Adichunchanagiri Institute of Medical Sciences, B G Nagara. Skulls with fractures and deformities were excluded from the study. Intact skulls were cleaned thoroughly and observed for the presence of wormian bones along the sutures of skull. Results: Out of 95 skull bones studied, 24 (25.26%) skulls showed the presence of wormian bones. We also observed that maximum number of such bones (single or multiple) were present along the lambdoid suture followed by lambda, asterion, sagittal suture & coronal suture. A very small wormian bone was also found near the bregma of the skull. Conclusion: The awareness about the occurrence of wormian bones and their topographical distribution will guide the clinicians mainly neurosurgeons in their practice. These bones mimic fracture lines in radiograph; therefore radiologists must also be aware of this normal variation. KEY WORDS: Wormian bone, Lambdoid suture, skull.