| PART ONEObject:To observe the structure and measure the morphologic parameters of pedicle rib complex.Methods:The thin-section CT scan data in the upper thoracic spine of 30 patients were reconstructed, select the transverse sections on the axis of each pedicle and pedicle-rib complex. Observed and measured the PW, PH, PAL and TPA of each pedicle, and PRCW, PRCH, PRCL and TPRCA of each pedicle-rib complex in the segments of Th3～Th5. Then, select the above 20 CT scan data and reconstructed 3-D model of pedicle rib complex of Th1-Th6 by Mimics software. After that, the best approach of ARPRCS and its axis were simulated. Finally, the DtlARPRCS, DslARPRCS, tARPRCSA, sARPRCSA and ARPRCSL were measured through the 3-D measuring tool of that software.Results:The mean of the PRCW in the Th3-Th5 was 5.03 mm, which was bigger significantly than the PW (12.73 mm) The mean of the PRCH was 9.17mm, which was smaller significantly than the PH (11.73 mm). The mean of the TPRCA (31.43°) was bigger significantly than the TPA (13.32°) and the mean of the PRCL (58.44 mm) was longer than the PL (38.77 mm). The PH was bigger than its PW, whereas the PRCH was smaller than its PRCW, which was bigger than the same segmental PW.The date of the ARPRCSL, DtlARPRCS, DslARPRCS and sARPRCSA was bigger gradually from Th3 to Th5, whereas, the trend of tARPRCSA was contrary. The mean of the ARPRCSL was 57.25mm (range 46.1 mm～65.8 mm) in the Th3-Th5, which was 55.03 mm, 57.27 mm and 59.45 mm, respectively. The mean of the DtlARPRCS was -3.58 mm (range 0～-5.8 mm), which was -2.82 mm,-3.69 mm and -4.26mm, respectively. The mean of the tARPRCSA was 32.68° (range 21.3°～39.6°), which was 34.82°,32.73° and 30.48°, respectively. The mean of the DslARPRCS was 5.68 mm (range 2.7～ 9.1 mm), which was 4.58 mm,5.89 mm and 6.56 mm, respectively. The mean of the sARPRCSA was 82.44°(range 71.1°～91.2°), which was 78.17°,83.30°and 85.85°, respectively.Conclusions:1. The diameter of ARPRCS is depended on the PRCH.2. We can implant bigger and longer screw in the pedicle rib unit than that in the pedicle.3. The TPRCA is bigger than its PA and the risk of spinal injure maybe smaller.4. The complexity of three-dimensional structure of PRC should be in our mind when we reverse implant screw into PRC. We should implant the screw into the overlap bone structure. We also should choice different screw, insertional point and orientation in the different segment.PART TWOObject:To compare the maximal axis pullout strength between the anterior reverse pedicle-rib complex screw (ARPRCS) instrumentation and pedicle screw instrumentation and to evaluate their biomechanical property of the ARPRCS.Methods:Ten formalin-preserved thoracic spines (Th1～Th6) were harvested with the medial 5-6 cm of rib, overlying parietal pleura and the intercostal soft tissue intact. The ARPRCS technique was adopted on one side and the standard pedicle screw technique was carried out on the other side in the segment of Th3～Th5. Then, biomechanical testing was performed on an electronic biomechanical testing device and the maximum axial pullout of strength was measured.Results:The maximal axis pullout strength of ARPRCS was 322.1±66.6 N, which seem lower than that of pedicle screw (340.6±5.0 N), whereas the difference was not statistical significance (P=0.254).Conclusions:With the bigger and longer screw, the fixation method of anterior reverse pedicle-rib complex screw has similar pullout force with the method of pedicle screw. The fixation approach of anterior reverse pedicle-rib complex screw can supply enough biomechanical fixation strength for upper thoracic spine. |
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