Morphometric properties and bone mineral density of the lumbar spine in a South African population : surgical considerations for spinal fusion

Abstract

The raised prevalence of lumbar spine pathologies and injuries, has lead to the investigation into more efficient and less invasive treatments for these diseases. In order to establish more specialised techniques, various authors have turned their attention to the morphometrics and material properties of the lumbar spine. Some of these properties might be considered as population specific, however possible trends have not yet been investigated in certain population groups. This study aimed to determine which factors, if any, might be specific to South African population groups. Twenty white adult (age > 20) cadaver specimens were obtained from the University of Pretoria (n = 12) and the University of Witwatersrand (n = 8), of which nine were male and eleven female. The lumbar spines were dissected to measure parameters of Kambin’s triangle (a safety zone used to avoid the dorsal nerve root and ganglion during microdiscectomies), and record the position of the dorsal root ganglion (DRG) in relation to the caudal pedicle. Computed Tomography (CT) scans, obtained from Steve Biko Academic Hospital (SBAH), were used to determine the lumbar lordosis angle (LLA), bone mineral density (BMD), and morphometrics of healthy lumbar spines. The sample consisted of eighty-two adult scans of which forty-six were male (33 black; 13 white) and thirty-six female (22 black; 14 white). Magnetic Resonance Imaging (MRI) scans, also from SBAH, were used to measure the neural foramen, and map the position of the nerve root and ganglion within. The sample consisted of twenty-six black adult scans (9 female; 17 male). The DRG’s were generally seen at the midline of the caudal pedicle. The dimensions of Kambin’s triangle showed little variation between sexes. The lordosis angles, most morphometric parameters, and most BMD parameters varied greatly between groups and sexes. The neural foramen and nerve root measurements indicated little variation between sexes. When comparing measurements between vertebral levels for all three components, patterns of increase, decrease, or combinations thereof were seen when moving caudally in the spine. Population differences were seen for some parameters. Also, some differences were evident when comparing results from the current study to previous studies, however the exact reason for variation was not established. Therefore, further investigation is needed into the cause of variation in trends between and within the population groups.