Anatomical Study For Pedicle Screw Placement In The Upper Thoracic Spine

Objective: To provide an anatomical basis for pedicle screw placement ofPCTPMLTDUAS (the Point to the Crest of the Transverse Process and the Mid-verticalLine of Transverse Diameter of the Upper Articular Surface) through observing thePresence of the Crest of the Transverse Process and studying the Anatomicalrelationship between PCTPMLTDUAS and the vertebral pedicle in the upper thoracicspine.Method:①10dry upper thoracic specimens were measured and statistically analyzedfor study of pedicle parameters using anatomical and CT measurement.②The pedicleparameters of10dry upper thoracic specimens and60patients were compared andstatistically analyzed.③20dry upper thoracic specimens were obtained to study thepresence rate of the Crest of the Transverse Process.④10dry upper thoracic specimenswere measured and the anatomical relationship between PCTPMLTDUAS and thevertebral pedicle was assessed.⑤10dry upper thoracic specimens were imitativelyimplanted pedicle screws using the start point of PCTPMLTDUAS and the relevantparameters were measured and statistically analyzed.Results:①The pedicle parameters of the upper thoracic spine is varied betweenmeasurement methods, the results of anatomical measure is slightlier increased(about1.72%～13.64%) than the ones of CT measure, and they do not differ significantly. Thismeans the pedicle parameters is equivalent between anatomical measurement and CTmeasurement.②The presence rate of the Crest of the Transverse Process is100%in theupper thoracic spine and only the distinct level of form is different but is identifiedeasily.③The percentage between the distances from the Crest of the Transverse processto superior,inferior margin of vertebral pedicle and the pedicle height and the onebetween the Mid-vertical Line of Transverse Diameter of the Upper Articular Surface tothe lateral, the medial margin of the vertebral pedicle and the pedicle width isconstant,the former ranges from44.74%to44.95%and the latter from45.24%to45.90%.④the percentage between Pedicle Spongy Width (PSW) and Pedicle Width(PW) of T1—3is60%,as3.6—5.6mm and T4-6is50%,as2.5—2.8mm. the pedicle transverse angle (PTA) decreases from29.6°to6.4°and the pedicle sagittal angle(PSA) ranges from12.1°to19.3°and the pedicle length (PL) ranges from33.7mm to38.2mm.⑤Using the start point of PCTPMLTDUAS as anatomical location for pediclescrew placement, the screw diameters range from2.5mm to5.6mm；the implantationdirections decrease from29.6°to6.4°as angle E and range from12.1°to19.3°as angleF and pedicle channel length ranges from33.7mm to38.2mm.Conclusions:①The pedicle parameters of the upper thoracic spine usinganatomical and CT measure do not differ significantly. This means the both areequivalent in evaluating the pedicle parameters.②the Crest of the Transverse Processappears constantly in the upper thoracic spine and only the distinct level of form isdifferent but is identified easily.③This study gives the anatomical relationshipbetween PCTPMLUAS and the vertebral pedicle, and provides a new anatomicallocation for transpedicular operation.④Using the start point of PCTPMLTDUAS asan anatomical location for pedicle screw placement,the screw diameters, theimplantation directions and pedicle channel lengths are obtained in this study.