OBJECTIVETo study the anatomical and biomechanical features of sacral pedicle and lateral mass so as to provide reference for clinical screw fixation technology of sacral pedicle and lateral mass.

METHODSA total of 60 adult patients'spiral CT images of the sacrum and coccyx were selected randomly. The entry points of sacral pedicle and lateral mass screws were determined, and the screw trajectory was measured using the three dimensional reconstruction method. Meanwhile, the gross anatomy was scrutinized in 15 adult cadaver specimens to determine the sacral pedicle and lateral mass screw entry points. The length, width and angle of sacral pedicle and lateral mass screw trajectory were measured. Eight of 15 cadaver specimens were selected to test the maximal extraction force of sacral pedicle and lateral mass screws. The clinical data of 15 cases treated by pedicle and lateral mass screw technology were collected and analyzed.

RESULTSThe diameter and length of S(1)-S(5) sacral pedicle and lateral mass screw trajectory were regular, with about 20 degree inclination angle. The S(1) pedicle screw entry point was located at the intersection point of the basal lateral part of articular process and median line of transverse process, and no significant difference was found for the maximal extraction force between pedicle and lateral mass screws (P larger than 0.05). The entry points of S(2)-S(5) pedicle screws were located at the intersection point of the line connecting adjacent posterior sacral foramina and median line of the transverse process. The lateral mass screw entry point of S(2)-S(5) was on the median side of intersection point between median line of the transverse process and lateral sacral crest. The maximal extraction force of pedicle screws was significantly greater than that of lateral mass screws (P less than 0.05).

CONCLUSIONBoth the sacral pedicle and the lateral mass screw fixation techniques can offer effective fixation and reconstruction for fracture of the sacrum and coccyx, but pedicle screw fixation may be more convenient, safe and reliable than lateral mass screw fixation.

Adult ; Biomechanical Phenomena ; Bone Screws ; Female ; Fracture Fixation, Internal ; methods ; Humans ; Imaging, Three-Dimensional ; Male ; Sacrum ; anatomy & histology ; physiology ; surgery ; Tomography, X-Ray Computed

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.

Orthodontic treatment is more complicated when both soft and hard tissues must be considered because an impacted maxillary canine has important effects on function and esthetics. Compared with extraction of impacted maxillary canines, exposure followed by orthodontic traction can improve esthetics and better protect the patient's teeth and alveolar bone. Therefore, in order to achieve desirable tooth movement with minimal unexpected complications, a precise diagnosis is indispensable to establish an effective and efficient force system. In this report, we describe the case of a 31-year-old patient who had a labio-palatal horizontally impacted maxillary left canine with a severe occlusal alveolar bone defect and a missing maxillary left first premolar. Herein, with the aid of three-dimensional imaging, sequential traction was performed with a three-directional force device that finally achieved acceptable occlusion by bringing the horizontally impacted maxillary left canine into alignment. The maxillary left canine had normal gingival contours and was surrounded by a substantial amount of regenerated alveolar bone. The 1-year follow-up stability assessment demonstrated that the esthetic and functional outcomes were successful.

Vibration represents a micro reciprocating motion of a particle or object along a line or arc relative to a reference position, while the effect of low-magnitude high-frequency vibration (LMHFV) on skeletal system cells is similar to the mechanical stimulation of muscle movement. Bone mesenchymal stem cells (BMSCs), which have been identified as force-sensitive cells, exist in the bone marrows and have the potential of multi-lineage differentiation. Their biological characteristics can change functionally according to the appropriate stimulation in vitro, in order to reach the optimal demand of the stimulation. LMHFV can promote the osteogenic differentiation of BMSCs, therefore, the research on its mechanism can contribute to the application of vibration in the treatment of diseases such as osteoporosis, fracture, osteogenesis imperfecta, obesity as well as the promotion of orthodontic tooth movement. This paper summarizes the recent progress about the effects of vibration on BMSCs stem cells in osteogenesis and the possible mechanisms, so as to provide research ideas and methods for studying the mechanical as well as biological changes of BMSCs under vibration stimulation.