Study Design Analysis of morphometric data obtained from direct measurements of 100 cadaveric thoracic spines in Indian population. Purpose To collect a base line morphometric data and analyze it in reference to the musculoskeletal anatomy and biomechanics of the spine; implants and instrumentations; and to suggest the requisite modification in spinal surgery instrumentations. Overview of Literature Most of the previous studies in the world literature have focused primarily on the parameters of the pedicle and to the authors' knowledge; no study has been published from the Indian subcontinent reporting a detailed morphometry of the thoracic spine. Methods One thousand and two hundred thoracic vertebrae were studied by direct measurements for linear and angular dimensions of the vertebral body, spinal canal, pedicle, and spinous and transverse processes in 100 human cadavers. Results Thirty-five point five percent of all the pedicles; 71% of T5 pedicles; 54.6% of all the female pedicles; and 94.4% of the T5 pedicles in females were smaller than 5 mm in mid-pedicle width dimension. Transverse pedicle angle was more at all levels and pedicles were sagittaly angulated in cephalad direction in comparison to other studies. Minimum value of interpedicular distance was at T5 (15.48 ± 1.24). Vertebral body width showed slight decrease from T1 to T4. The transverse process length was relatively constant between T2 to T10. The spinous process angle showed increasing trend from T1 to T6 and then gradually decreased to T12. Conclusions Most of the trends in changes of the parameters from T1 to T12 can be explained on the basis of local musculoskeletal anatomy and biomechanical stresses. The smallest diameter screw and shortest available screw for adults may not be safe in majority of the Indian population in mid-thoracic region. The results of the present study can help in designing implants and instrumentations; understanding spine pathologies; and management of spinal disorders in this part of the world.
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