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Objective To study the anatomical and biomechanical features of sacral pedicle and lateral mass to provide evidence for clinical sacral pedicle and lateral mass screw fixation technology. Method 60 adult patient's spiral CT images of sacrum and coccyx were selected randomly. The sacral pedicle and lateral mass screw entry point was determined, and the crew trajectory were measured using the three dimensional reconstruction. Meanwhile, the gross anatomy was done for 15 adult cadavers to determine the sacral pedicle and lateral mass screw entry point. The length, width and angle of sacral pedicle and lateral mass screw trajectory was measured. 8 of 15 cadaver specimens were selected to test for the maximal extraction force for sacral pedicle and lateral mass screws. ResultsThe diameter and length of S1～S5 sacral pedicle and lateral mass screw trajectory are significantly regular, with inclination angle is about 20°. The S1 pedicle screw entry point is located at intersection point of basal lateral part of articular process and median line of transverse process, no significant difference is found between the maximal extraction force of pedicle and lateral mass screws (P>0.05）. The entry points of S2～5 pedicle screws are located at the intersection point of the line connecting adjacent posterior sacral foramina and median line of transverse process. The lateral mass screw entry point of S2～5 is on the median side of intersection point between median line of transverse process and lateral sacral crest. The maximal extraction force of pedicle screws are significantly different from the lateral mass screws（P<0.05）. Conclusions Both the sacral pedicle and the lateral mass screw fixation technology can offer effective fixation and reconstruction for the fracture of sacrum and coccyx, but the pedicle screw fixation may be more convenient, safe and reliable than the lateral mass screw fixation technology.
RESUMO
<p><b>OBJECTIVE</b>To study the feasibility of applying expanded forehead axial flaps with fascia pedicles carrying bilateral frontal branches of superficial temporal artery and vein (expanded forehead axial flap with double pedicles in brief, EFAF-DP) in repairing scars in submaxillary region.</p><p><b>METHODS</b>Sixteen patients with mandibular scars hospitalized in Department of Burns and Plastic Surgery of the First Hospital Affiliated to Fuzhou General Hospital in Nanjing Military Area Command from July 2005 to December 2009 were repaired with EFAF-DP. The operation consisted of 3 stages. Before operation, the location and course of superficial temporal arteries and veins (STAV) and their frontal and parietal branches were identified with Ultrasonic Doppler blood flow detector. In stage I, STAV were dissected from the frontalis muscle as a pedicle to form a skin soft tissue space to hold the dilator of a proper size. In stage II, after gradual dilation by repeated filling with saline, the dilator was removed. EFAF-DP was dissected to repair mandibular scar. Donor site was closed with sutures. In stage III, flap pedicles were divided and pruned.</p><p><b>RESULTS</b>Flap sizes ranged from 25 cm × 6 cm to 33 cm × 16 cm. The duration of dilation was 3-5 months, with 3.6 months in average. Ten patients underwent the operation of EFAF-DP transplantation and cervical skin dilatation. All flaps survived with healing of wounds. Disorder of venous return at the distal end of one flap was seen after second stage surgery, and it was corrected after comprehensive treatment including relieving spasm and improving venous return. Donor site wounds healed with normally grown hair without cicatricial alopecia along the hairline. Few hairs grew around mandible in one female patient out of the three (no hair grew on flaps of other two patients). This female patient and two male patients requesting for beard plasty received laser depilation treatment 1 to 3 months after discharge, with good result. Other male patients received no special treatment for their beard, and they shaped their beard with shaver. Sixteen patients were followed up for 6 to 24 months, and the shape of the flaps and beard (excluding female patients) were satisfactory with good appearance, satisfactory skin color and texture. The mobility of neck was obviously improved.</p><p><b>CONCLUSIONS</b>EFAF-DP provides bigger areas of a thin flap besides promoting vascularization of new vessels of flap. Extra expanded skin can be directly sutured at the fringe of hairline, which makes skin grafting unnecessary, and decreases the incidence of secondary deformity in donor sites. Some hair carried by the flaps can be directly used for beard reconstruction after rotation to help the male patients have a better appearance.</p>