| ObjectiveTo create pure depression fracture of the lateral tibial plateau on fresh-frozen specimen for feasibility study and clinical application of the treatment to depressed tibial plateau fracture that the fracture was reduced by percutaneous balloon distension and fix by injectable calcium sulfate cement(CSC). There was a biomechanical comparison of different minimally invasive treatment to central depressed tibial plateau fracture for the initial fixation strength.Methods1. At room temperature, twenty-four fresh-frozen proximal tibia specimen were harvested. After soft tissue removal, the central part of the lateral tibial plateau was get on partly osteotomy to the subchondral bone. Then, a 15.0-millimeter diameter stainless steel rod was positioned on the surface of the central portion of the lateral tibial plateau in line with the long axis of the tibial shaft to make it depressed. And, the tibial plateau fracture of Schatker type III was produced. Anteroposterior and lateral radiographs of each specimen were obtained: before pure depression fracture, after fracture, after reduction and fixation, after biomechanical comparison. Each tibia was scanned in the coronal view by dual-energy x-ray absorptiometry. And region of interest (ROI) in the superior half of the lateral and proximal metaphyseal region were analyzed for bone mineral density(BMD).2. The twenty-four models of tibial plateau fracture of Schatker type III were randomly divided into three groups. A group (standard group) was received conventional treatment of morselized bone graft that fractures were reconstructed by "drag-and-draw" reduction and fixed with two cancellous screws; B group (CSC group) was received treatment that the fractures were reduced by percutaneous balloon distension and fix by injectable calcium sulfate cement; C group (CSC and screw group) was received treatment that the fractures were reduced by percutaneous balloon distension and fix by injectable calcium sulfate cement Combined use of two cancellous screws. Then to get the general observation and effect measurement of reduction and fixation.3. By reference to the experimental research, we used the treatment for clinical cases with depressed tibial plateau fracture that the fractures were reduced by percutaneous balloon distension and fixed by injectable calcium sulfate cement combined use of two cancellous screws under arthroscopy. And the effectiveness was followed up.4. The long axes of the specimen (included a control group) were mounted vertically onto the load plate of a Material Testing Systems materials testing machine. A 15.0-millimeter diameter stainless steel rod was attached to the actuator and used to apply load directly to the articular fracture fragment of the proximal tibia. Each specimen was loaded 100 newtons for preconditioning. Immediately after preconditioning, a compressive load was applied directly to the articular fracture fragment at a rate of 0.5 millimeter per minute by a 15.0-millimeter rod attached to the Material Testing Systems actuator for a displacement of twelve millimeters for biomechanical test. Data were recorded continuously during the biomechamcal test at a sampling rate of 15 hertz,and the pressure (KN) and displacement (mm) data were used to map pressure - displacement curve. There were biomechanical comparison for the stiffness and the displacement after 350 newtons loading, for the loading and the stiffness after 3 millimeters displacement and for the ultimate loading and the displacement by the ultimate loading. After the test was completed, a gross description of the fracture and location of CSC material or screw position was recorded.Results1. For control group, the BMD of the ROI was 1.087±0.295 grams per square centimeter.The standard group was 1.076±0.273 grams per square centimeter , the CSC group was 1.106±0.256 grams per square centimeter, the CSC and screw group was 1.091±0.302 grams per square centimeter. BMD showed no significant difference for all four groups. Radiographs showed no bone abnormality.2. Twenty-four fresh models of tibial plateau fracture of Schatker type III were obtained and the average depression (displacement) of the articular fracture fragment was 7.87±0.84 millimeters. And the preoperative average displacement was 7.95±0.72 millimeters for the standard group, 7.80±1.01 millimeters for the CSC group, and 7.87±0.87 millimeters for the CSC and screw group. There was no statistical difference among the three groups(p>0.05). Three groups with different treatments all have good reduction with depression -0.22±0.63 millimeters postoperatively. And the postoperative average displacement was -0.22±0.62 millimeters for the standard group, -0.23±0.67 millimeters for the CSC group, and -0.20±0.69 millimeters for the CSC and screw group. There was no statistical difference among the three groups(p> 0.05). The effectiveness of reduction by percutaneous balloon distension is excellent.3. On the clinical cases, the treatment with fractures reduced by percutaneous balloon distension and fixed by injectable calcium sulfate cement combined use of two cancellous screws under Arthroscopic-assisted had a good effectiveness. The cases had good reduction and were followed up postoperatively without depression again and with fracture healing well by radiographed.4. The average displacement of the articular fracture fragment after 350 newtons was 0.101±0.011 millimeters for the control group, 0.769±0.085 millimeters for the standard group, 0.389±0.047 millimeters for the CSC group, and 0.230±0.049 millimeters for the CSC and screw group. There was astatistical difference among the four groups(p< 0.05). And after 350 newtons, the average stiffness have statistical difference for the four groups: 3621±386 newtons per millimeter, 534±56 newtons per millimeter, 1053±115 newtons per millimeter and 1492±374 newtons per millimeter. After 3 millimeters displacement, the loading was 2110±191 newtons for the control group,1001±131 newtons for the standard group, 1310±169 newtons for the CSC group, 2378±213 newtons for the CSC and screw group. There was statistical difference among the four groups(p< 0.05). And after 3 millimeters displacement, the average stiffness have statistical difference for the four groups: 3387±264 newtons per millimeter, 436±44 newtons per millimeter, 837±56 newtons per millimeter and 1293±71 newtons per millimeter. The ultimate loading in 12 millimeters displacement was 2302±175 newtons at 2.611±0.102 millimeters displacement for the control group, 1839±293 newtons at 9.395±0.763 millimeters for the standard group, 1363±165 newtons at 3.145±0.708 millimeters for the CSC group, 3707±145 newtons at 10.191±0.934 millimeters for the CSC and screw group. The ultimate loading difference of the four groups reached statistical significance. There was no statistical difference between the displacement in the control group and the CSC group(p=0.301), and between the standard group and the CSC and screw group(p=0.374). The treatment with fractures reduced by percutaneous balloon distension and fixed by CSC combined use of two cancellous screws provides better stability than only CSC fixation in pure depression tibial plateau fractures.And,they both provide better stability than conventional drag-and-draw" reduction and fixed with two cancellous screws.Conclusions1.It is feasible to reduce fractures by percutaneous balloon distension in depression tibial plateau fractures.2.Calcium Sulfate Cement in tibial plateau fractures could provides good support and stability ,and if CSC is combined with cancellous screws, the support and stability is further improved.3.There is clinical applicational value for the fractures reduced by percutaneous balloon distension with CSC graft in minimally invasive treatment of depressed tibial plateau fracture.
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