A Primal Experimental Study Of Designing And Manufacturing New Type Of Point Contact-Locking Compression Plate (PC-LCP)

Bone plates internal fixation was a common technique for limb fracture at present. In recent years, with the cognition of the bone's biology character, people have advanced the BO theoretics based on AO. The aims of this change were reduce the breakage of the part of bone blood supply and degrade the complications after bone fracture operation. The change promoted the design of internal fixation evolution greatly. The Low Contact Dynamic compression plate (LC-DCP), Locking Compression plate(LCP), Point Contact Fixator (PC-Fix) and Conical Cylinder Point Contact-Fixator (CCPC-Fix) etc as minimally invasive internal fixation had been designed. However, the limited contact function of LC-DCP has been doubted by many scholar that it still depended on the friction between bone and internal fixation to attaining the stabilization. The integrative design between taper locking bore and dynamic compression bore of LCP weakened the biomechanical of the plate.The question of contact that existed between plate and the bone surface of PC-Fix had been dissolved, but the bore of PC-Fix still been designed to the rotundity which had not reserved compressing function like the traditional internal fixation plate. CCPC-Fix Reserved the function of compression, but it still depended on the friction between the plate and the bone surface to keeping the stabilization of the bone fracture. For protecting the supply of bone fracture and the bone cortex further and providing the best bone healing biological environment, we had designed one new internal fixation plate PC-LCP which integrated the function of locking, point contact and compression. The point contact design could decrease the contact area between the plate and the bone surface that could protect the blood supply of the bone cortex and the bone fracture. The compression function of PC-LCP were a strongpoint of plate which was used to adapting the type of the bone fracture and been used freely when the plate fixed the bone fracture. The locking function changed the force mode between the plate and the bone surface, which changed from the friction force between the plate and the bone surface to the strength between the boil and the plate.In order to provide theoretical and experimental basis for future clinical application, the biomechanical, the biological characteristics, the contact proportion and animal experiments of the PC-LCP were studied with traditional DCP and LC-DCP as a control group.The study of the biomechanical and the contact proportion under the bone surface of the PC-LCP showed: 1. The torsion and bending rigidity biomechanical of PC-LCP compared with that of DCP had not distinct difference; 2. The contact proportion under bone surface of PC-LCP decreased greatly compare with that of LC-DCP. The PC-LCP had the same contact character on different bone surface while the LC-DCP effected easily by the bone surface in contrast. This result revealed that the PC-LCP had the same biomechanical character as the other two traditional bone plate and the PC-LCP could decrease the contact proportion furthest for the aim of protecting the blood supply of bone cortex under the plate.The result of testing the regional microcirculation in cortical bone and observing the change of cortical bone collagen fibers after fixed by PC-LCP and DCP showed: 1.24 hours after operation, the blood supply of cortical bone affected by PC-LCP less than that of DCP group and LC-DCP. 2. Region of the perfusion deficiency was found at 1 day after operation with PC-LCP and DCP fixation. However, it had recovered at 4week with PC-LCP fixation group. DCP application resulted in a continuous perfusion deficiency under the plate at 1day, 2weeks and 4weeks. The perfusion deficiency did not disappear until 8week after operation; The blood supply of bone cortex under the plate PC-LCP was higher than that under the plate DCP at all time. 3. Both the PC-LCP and the DCP had affected the collagen fibers at a certain degree, but the DCP had more affection on the collagen fibers. At 12week, many collagen fibers presented the appearance of corrosion, break and disarrangement under cortical bone fixed by DCP, but the change of collagen fibers in group PC-LCP were not obvious than that in group DCP. PC-LCP illuminated the merit that it disturbed bone cortex less and protected the bone cortex blood supply under the plate effectively which provided a gooe method for promoting the bone healing and decreasing the infecton. Fracture healing experiment was studied in goats. The immunity histochemistry demarcating the growth of new blood vessel, fluorescence marker, Sirius Red stained, histology, X-ray and the biomechanical test of healing bone were used to observed the degree of bone fracture healing. The results showed: 1.The PC-LCP fixed group had more new blood vessel growth than that of DCP fixed group. The newborn blood vessel in group PC-LCP had the more mature character in all times.2. Fluorescence marker showed no distinct difference between group PC-LCP and group DCP in bone healing ability. 3. In group PC-LCP, type I collagen fibers growth more mature than that of group DCP. 4. The histology results showed that in group PC-LCP the rate of fracture healing were better than that of group DCP. 5. X-ray scanning revealed that the fractures healed well in both group PC-LCP and group DCP, but the bone cortex found the phenolmenon of absorb and atenudation. 6. The mechanical test showed that the quality of the fracture healing was superior in group PC-LCP than that of the group DCP.From the analysis above, we can get the conclusions as follow: 1. PC-LCP has the character of the same fixation stability as the traditional bone plate while it has the less contact proportion under the bone surface greatly. 2.PC-LCP can provide the environment of optima bone healing biology by protecting the blood supply and the collagen fibers of cortical bone under the plate, that can prevent the occur of the bone loose later. 2. The PC-LCP can provide better healing rate and healing quality than that of traditional plates. PC-LCP can provide more choice for the clinic application as one perfect internal fixation plate.