Influence of cement-augmented pedicle screw instrumentation in an osteoporotic lumbosacral spine over the adjacent segments: a 3D finite element study.

PURPOSE: To compare the effect of conventional pedicle screw (CPS) and cement-augmented pedicle screw instrumentation (CAPSI) on adjacent segment degeneration (ASD). METHODS: A normal male volunteer without a history of spinal disease was selected, lumbar CT data was collected, an intact L3-S1 three-dimensional finite element model was created by software including Mimics, Geomagic, and SolidWorks, and the fixation methods were performed accordingly. A common pedicle screw model and a cement-augmented pedicle screw model of L4-L5 with fusion and internal fixation were constructed. With ANSYS Workbench 17.0, a 500 N load was applied to the upper surface of L3 to simulate the weight of a human body, and a 7.5 N m moment was applied at the neutral point to simulate flexion, extension, left/right bending, left/right rotation of the spine. The peak von Mises stress of intervertebral disc and the range of motion (ROM) on the adjacent segments (L3-4 and L5-S1) were compared. RESULTS: The validity of the intact model shows that the ROM of the model is similar to that of a cadaveric study. Compared with the intact model, CPS model and CAPSI model in all motion patterns increased the ROM of adjacent segments. The intervertebral disc stress and the ROM of adjacent segments were found to be higher in the CAPSI model than in the CPS model, especially in L3-4. CONCLUSION: In general, the biomechanical analysis of an osteoporotic lumbar spine showed that both CPS and CAPSI can increase the ROM and disc stresses of osteoporotic lumbar models, and compared with CPS, CAPSI is more likely to increase the potential risk of adjacent segment degeneration.

[Manipulative reduction and internal fixation by percutaneous locking compression plate for the treatment of mid-distal tibiofibula shaft fractures].

OBJECTIVE: To investigate the clinical effects of manipulative reduction and percutaneous locking compression plate internal fixation for the treatment of mid-distal tibiofibula shaft fractures. METHODS: From January 2006 to October 2009,46 patients suffering from mid-distal tibiofibula shaft fractures were treated with closed manipulative reduction and LCP, involved 27 males and 19 females with an average age of 39 years old ranging from 17 to 56 years. According to AO classification, there were 12 cases of type A, 24 of type B, 10 of type C. The duration of visiting hospital were from 2 hours to 3 days after being injured for these patients. The injured limbs of the patients were swollen and painful,even with bony crepitus. The wound, function of the injured limb and union of fractures were observed after operation. RESULTS: All the patients were followed up from 12 to 18 months (averaged 15 months). It was found that the wound of all patients had primary healing without any infection. The fracture healing time was 12 to 18 weeks (means 14 weeks). The results were excellent in 40 cases,good in 4 and fair in 2. CONCLUSION: Less invasive, more stable fixation, shorter healing time and better functional rehabilitation are observed in the treatment of mid-distal tibiofibula shaft fractures after manipulative reduction and percutaneous locking compression plate internal fixation.