Objective: To find out the number of other skeletons in the Galloway collection that have a variation of six lumbar vertabrae.
Design: A descriptive cross-sectional study.
Setting: Department of Anatomy, Faculty of Medicine, Makerere University, Kampala.
Materials: Five hundred and ninety one skeletons in the Galloway Osteological Collection housed in the basement of the Department of Anatomy, Faculty of Medicine, Makerere University.
Interventions: The skeletons were examined. Those found to have six lumbar vertebrae were scrutinised further. A recount was done of the cervical and thoracic vertebrae in order to ascertain the identity and number of the lumbar vertebrae. Some of the skeletons were x-rayed and photographed to illustrate the finding and the manner in which the transverse processes of the sixth lumbar vertebrum articulated with the alar of the sacrum.
Results: Out of the 591 skeletons examined, twenty (4%) were found to have a sixth lumbar vertebrum. In seven (35%) of these, the transverse processes of the sixth lumbar vertebrum were found to be bilaterally articulated with the alar of th sacrum and in another five (25%) only the left was. In the remaining eight (40%), the transverse processes did not articulate with the alar of the sacrum at all. Right unilateral articulation between the transverse process and the alar of the sacrum was not observed in any of the twenty skeletons that had six lumbar vertebrae.
Conclusion: In the Galloway osteological collection there is a small number of skeletons in which the number of lumbar vertabrae is six instead of 5 as is normally the case. In most of them the transverse processes of th sixth lumbar vertebrum articulate with the alar of the sacrum through a synovial joint (bilateral or unilateral). The above observations have raised several questions in the mind of the author regarding the mechanism of causation of the variation and its clinical and functional implications.