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Lower Dorsal and Lumbar Pedicle Morphometry in Indian Population: A Study of Four Hundred Fifty Vertebrae

Study Design. Prospective, computer aided pedicle morphometric data measurements obtained from computed tomography (CT) scan of lower thoracic (T9-T12) and lumbar vertebrae in a large group of Indian population. Objectives. Measurement on CT scan of the surgically relevant parameters of transverse pedicle isthmus width, transverse pedicle angle, and depth to anterior cortex along the midline axis and the pedicle axis by Computer software aid in a large sample of Indian population. To compare the results with those of similar studies of Western and Indian population in literature by other methods and to deduce safety parameters for pedicular screw placements in these areas. Summary of Background Data. Although differences have been reported in literature between various ethnic groups, most studies reported are for white populations and Indian studies are few. The Indian studies have had small sample size, and been done on patients with preexisting spinal disorder or cadavers and by manual data measurements. To the authors' knowledge, the present study is the largest published for patients from the Indian subcontinent and only using computer software aided measurements. Methods. CT scans of the lower thoracic and lumbosacral spine of patients free from spinal disorders from the Indian subcontinent were reviewed. We analyzed a total of 450 vertebrae in 50 consecutive patients. Parameters recorded were transverse pedicle isthmus width, transverse pedicle angle, and depth to anterior cortex along the midline axis and the pedicle axis with help of computer software. Results. The mean transverse pedicle isthmus width was least at the T9 level (5.65 mm). Majority of pedicles at thoracic level had diameter over 5 mm T9 (94%), T10 (100%), T11 (96%), T12 (100%). At lumbar all had diameters over 7 mm with wide range at upper levels. The mean transverse pedicle angle faced laterally at thoracic vertebrae with exception of T9. In lumbar area, all were medially directed with maximum at L5 and least at L1. The depth to the anterior cortex was more along the pedicle axis at all levels except T11 and T12. Conclusion. Significant differences exist between the pedicles of Indian and white populations. It is suggested that preoperative software-based morphometric data should be collected if possible for preoperative planning of pedicle implant placement and sizes to avoid inadvertent complications. Further, data from study can be used as a guide for implant size, intraoperative placement trajectory at lower thoracic and lumbar vertebrae pedicles.