Objective To evaluate the therapeutic effects of expandable pedicle screw (EPS) combined with interbody fusion cage on lumbar spondylolisthesis. Methods From June 2004 to March 2008, 23 patients with lumbar spondylolisthesiswere treated, including 9 males and 14 females aged 24-72 years old (average 48.7 years old). The course of the disease varied from 6 months to 6 years (average 30.4 months). There were 18 cases of degenerative spondylol isthesis and 5 of isthmic spondylolisthesis, including 1 case at L3,4 level, 14 at L4,5 level, and 8 at L5 and S1 levels. There were 17 cases of grade I, 4 of grade II, and 2 of grade III (including 1 case of recurrent L5 spondylolysis) according to Meyerding classification system. Posterior lumbar interbody fusion was performed using 48 PLIVIOS interbody fusion cages, and spondylolisthesis reduction and internal fixation were conducted using 84 pieces of EPS. The indications for use of EPS were initial operation with bone mass reduction or osteoporosis, reoperation of previous pedicle instrumentation, intraoperative screw relocation, sacral anchoring, and construct reinforcement. Cl inical outcomes, radiographic reduction of spondylol isthesis and bone fusion of lumbar interbody were evaluated based on JOA score, Boxall index, and Cook criteria. Results The incision healed by first intension in all cases except for one revision case that suffered from postoperative cerebrospinal fluid leakage and obtained delayed-healing without infection 23 days after operation using conservative treatment. No operative compl ications such as nerve and organ injuries were found.All cases were followed up for 12-39 months (average 17.8 months). X-ray exams of spine AP, lateral, fully extended position and fully flexed position view showed all 84 EPS were fully expanded within vertebral body. The improvement rate of JOA at the final follow-up visit was markedly effective in 14 cases, and effective in 5 cases, and noneffective in 4 cases, with a total effective rate of 82.61%. Anatomic reduction was achieved in 14 cases, improvement was obtained in 6 cases, no improvement was observed in 3 cases, and the reduction rate was 86.69%. Lumber interbody fusion was achieved in 20 cases, fixation was achieved in 2 cases, failure was observed in 1 cases, and the fusion rate was 86.69%. Conclusion EPS in complex with interbody fusion cage provides effective reduction, internal fixation and interbody fusion for the reconstruction of lumbar spondylolisthesis.
Objective To evaluate the fixation strength of expansive pedicle screw (EPS) at different bone mineral density (BMD) levels, further to provide theoretical evidence for the clinical application of the EPS in patients with osteoporosis. Methods Fresh human cadaver spines (T12-L5 spines) were divided into 4 levels: normal BMD, osteopenia, osteoporosis, and severe osteoporosis according to the value of BMD, 12 vertebra in each level. Conventional pedicle screw (CPS) or EPS was implanted into the bilateral vertebra in CPS group and EPS group, respectively, 12 screws in each group per BMD level. Screw pullout tests were conducted. The maximum pullout strength, stiffness, and energy absorption were determined by an AG-IS material testing machine with constant rate of loading in a speed of 5 mm/ min. Results With the decline of BMD from normal to severe osteoporosis level, the maximum pullout strength and the stiffness correspondingly declined (P lt; 0.05). In CPS group, the energy absorption gradually decreased (P lt; 0.05); in EPS group, significant difference was found between other different BMD levels (P lt; 0.05) except between normal BMD and osteopenia and between osteoporosis and severe osteoporosis (P gt; 0.05). At the same BMD level, the maximum pullout strength of EPS group was significantly larger than that of CPS group (P lt; 0.05); the stiffness of EPS group was significantly higher than that of CPS group (P lt; 0.05) except one at normal BMD level; and no significant difference was found in the energy absorption between 2 groups (P gt; 0.05) except one at osteopenia level. No significant difference was found in maximum pullout strength, stiffness, and energy absorption between EPS group at osteoporosis level and CPS group at osteopenia level (P gt; 0.05); however, the maximum pullout strength, stiffness, and energy absorption of EPS group at severe osteoporosis level were significantly lower than those of CPS group at osteopenia level (P lt; 0.05). Conclusion Compared with CPS, the EPS can significantly improve the fixation strength, especially in patients with osteopenia or osteoporosis.
Objective Gunshot wound spreads to the surrounding tissues and organs, it is difficult to debride and easy to infect. The conventional treatment is thorough, extensive debridement, fully open drainage, which often causes normal tissue damage and compl ications. To evaluate the effectiveness of vacuum seal ing drainage (VSD) treating thepenetrating wound in porcine extremity by MRI and pathological methods so as to provide theoretical basis for future cl inical use. Methods Eight healthy adult pigs, weighing (45 ± 5) kg, were selected. Eight pairs of hind l imb penetrating wounds (16 wounds) were made by using Chinese-made 95-type rifle at 25 meters distance, which were randomly divided into experimental group (left side, n=8) and the control group (right side, n=8). After debriding and disinfecting the penetrating wounds at 6 hours after injury, wounds were treated with VSD in experimental group. The ball istics exports of the wounds were covered with single-layer gauze and imports were directly sutured and covered with sterile gauze in control group. The trajectory and the general condition of the adjacent skin were observed. MRI and histological observation were taken at 5, 24, 48, and 72 hours after injury, bacterial counting analysis was done at 0, 12, 24, 48, and 72 hours after injury. Results The aperture of the trajectory exit and entry were (5.00 ± 2.50) cm and (0.30 ± 0.15) cm immediately after injury. The wound surface was clean, rosy without leakage and swell ing after 72 hours in experimental group; wound and adjacent tissue were swell ing obviously, pus, muscle necrosis and exfol iative tissue was observed, and deep defect cavity at the trajectory exit could be seen in control group. MRI showed that pairs of l inear low signal in T1WI and T2WI was seen in trajector of experimental group at 5 hours after injury, and signal in T1WI gradually increased at disrupted area and tissue deformation area at 24, 48, and 72 hours; in control group, low signal in T1WI was observed at 5 hours after injury, and signal in T2WI gradually increased and a clear boundari between edema and surrounding tissue, and the increase of signal in T1WI was not obvious at 24, 48, and 72 hours. The histological observation showed that wound was dominated by effusion at 5 hours after injury, granulation tissue gradually increased, muscle tissue dissolved and inflammatory cell infiltration was not obvious at 24, 48, and 72 hours in experimental group; in control group, the gradual dissolution of muscle fibers and inflammatory cell infiltration were observed at 5, 24, and 48 hours, muscle tissue became swell ing, dissolving and degeneration and a large number of inflammatory cell infiltration gathered into the bacteria group at 72 hours. There was no significant difference in the number of bacteria per gram of tissue (P gt; 0.05) between experimental group and control group at 0 hour after injury; the numbers of bacteria in control group were significantly higher than those in experimental group at 12, 24, 48, and 72 hours (P lt; 0.05). Conclusion MRI combined with pathology show diagnostic meaning in treatment of gunshot wound with VSD. MRI can accurately reflect the scope of l imb gunshot wound 72 hours after injury. VSD may be an approach to delay infective time, shorten wound heal ing time, and promote the growth of healthy granulation tissue.