Morphometric analysis of lumbar pedicles among adult kenyans using computer tomography scans and dry bone specimens

Abstract

Background: There is a rise in the number of spine surgeries performed in kenya. Complications arising from misplaced lumbar pedicle screws are projected to rise with the use of free hand technique. This study was designed to provide accurate measurements of the adult kenyan lumbar pedicle. Objectives: To determine the width, height, angulation and chord length of the lumbar vertebrae pedicle from L1 to L5 in adult Kenyans using Computer tomography scans and dry bone specimens. Methods: This was a cross sectional descriptive study conducted at the Nairobi National Museum and St. Luke’s Hospital from January 1st – 31st December 2016. Ethical clearance was granted from IREC.Lumbar pedicle dimensions from L1-L5 were measured.100 dry bone specimens and 100 computer tomography scans were used. Data was recorded in data collection sheets, extracted and entered into Microsoft Excel then transferred to SPSS version 21 for analysis. Results from the analysis were summarized as means, standard deviations and presented in line and bar graphs. Results: One hundred dry bones were used for the study. Out of the 100 dry bones, 55 were male, with an age range of 31-89 years.100 computer tomography scans were used for the study with 49 males, with an age range of 18-63 years. Pedicle width mean measurements were L1-8.6mm, L2-9.6mm, L3-11.4mm, L4-13.5mm, L5- 16.3mm on dry bone specimens. On computer tomography scans, pedicle width mean measurements were L1-7.2mm, L2-7.6mm, L3-9.2mm, L4-10.8mm, L5-14. 6mm.Pedicle height mean measurements on dry bone specimen were L1-16.2mm, L2- 15.4mm, L3-14.5mm, L4-13.5mm, and L5-12.1 mm. The mean angle of insertion on computer tomography scans was L1-19.7o , L2-20.5o , L3-22o , L4-24.1o , L5-29.8o . Pedicle chord length measurements obtained were L1-47.9mm, L2-48.9mm, L3- 48.9mm, L4-47.7mm, and L5-47.0 mm on dry bone specimen. On computer tomography scan it was, L1-48.6mm, L2-49.9mm, L3-50.1mm, L4-49.8mm, and L5- 50.1 mm. Conclusion: The pedicle width on computer tomography scan measurements increased from 7.2mm to 14.6mm and on dry bone specimen it increased from 8.6mm to 16.3mm between L1 to L5. The pedicle height decreased from 16.2mm to 12.1mm between L1 to L5 on dry bone specimen measurement. The angulation increased from L1 to L5 on computer tomography scan measurements from 19.7o at L1 to 29.8o at L5. The chord length range measurement on dry bone specimen ranged from 47.9mm to 48.9mm and on computer tomography scans from 48.6mm to 50.1mm. Recommendations: The minimum size of screw diameter that should be used is 6.5mm with a length of 45mm angulated between 20o to 30o from L1 to L5. Based on the variation there is need for measurements of the pedicle dimensions before trans pedicular instrumentation. Further research should be carried out on lumbar pedicle dimensions based on age, weight and height as there exists variations.