Dimensions of the cervical spinal canal in the South African negroid population

Abstract

The dimensions of the cervical spinal canal (C3 – C7) of the South African black population were measured on skeletal remains of 179 individuals (90 males and 89 females divided into age categories of 30-45; 46-60 and 61-75 years), and compared to measurements taken from CT-scans of 55 individuals divided into the same categories. There was no significant difference between measurements taken on skeletal material and CT-scans. The spinal canal is larger in males (mean = 13.96mm) than in females (mean = 13.84mm) and the Pavlov ratio is larger for females (mean = 0.89) than males (mean = 0.81). The Pavlov ratio seems to overestimate the occurrence of spinal stenosis in this population group, as almost all individuals older than 46 years are classified as stenotic according to this ratio. The shape of the canal was determined morphometrically by processing digital images of the vertebrae of 60 individuals with the tps-Series of software programs and was found to be significantly different between males and females. In males the canal is congenitally triangular, whereas in females the canal assumes a more “safe”, rounded shape. The low Pavlov ratio for this population group, especially in males, can possibly be explained by these shape differences. Even slight degenerative changes affecting the spinal canal, such as osteophytosis or ossification of the posterior longitudinal ligament (OPLL), will alter the triangular-shaped male canal in such a way that the cord may become compromised. Cervical vertebrae of 107 individuals were inspected for occurrence of osteophytes within the spinal canal and the incidence of OPLL. Osteophyte occurrence within the cervical spinal canal is the same for males and females and OPLL occurs frequently within this population group, especially in the cephalic region (incidence: C3 = 64.5%; C4 = 47.7%; C5 = 21%; C6 = 12.2%; C7 = 7.5%).