Eur J Anat, 17 (4): 230-236 (2013)

Importance of transverse pedicle angle & chord length of lumbar pedicle in screw placement: a CT scan study on North West Indian population

Kunal Chawla¹, Mahesh Sharma², Suman Kochhar², Avinash Abhaya², Daisy Sahni¹ and Richa Gupta¹

¹Department of Anatomy, Post Graduate Institute of Medical Education & Research, Chandigarh, India, ²Department of Anatomy, Government Medical College & Hospital, Chandigarh, India

ABSTRACT The aim of this study was to measure the lumbar pedicle dimensions and its angulations for the development of techniques and devices for spinal instrumentation on computed tomography (CT) scan. Fifty CT scans of lumbar vertebral column of patients belonging to North West Indian population was randomly selected. Various morphometric parameters were recorded using software. The transverse pedicle angle increased from L1 to L5 in both males and females. In males it was maximum at L5 (25.7°) and minimum at L1 (7.5°). In females it was maximum at L5 (24.0°) and minimum at L1 (7.4°). The chord length in males was maximum at L5 (51.3 mm) and minimum at L1 (48.1 mm). In female chord length was maximum at L2 (51.1 mm) and minimum at L4 (47.6) on right side and on left side it was maximum at L3 (50.9 mm) and minimum at L1 (46.7 mm). A screw of 40 mm length appeared to be safe at all lumbar levels as all the vertebrae studied had a chord length well in excess of 40 mm. The length of the pedicular screw needs to be substantially smaller for Indian population than those mentioned in Western literature. At the lower lumber levels, greater lateral inclination of the pedicle should be kept in mind. Otherwise it may lead to the breach of the medial cortex of the pedicle with resultant risk to the neural tissues.

Keywords: Chord length, CT scan, Lumbar, Pedicle, Spine, Transverse pedicle angle, Vertebra