Investigation of the process intergrowth of bone tissue into the hole in titanium implants (Experimental research).

INTRODUCTION: Despite the use of modern implants, complications such as nonunion and avascular necrosis of the femoral head are observed in femoral neck fractures (FNF). We have created a new perforated I-beam implant for FNF osteosynthesis and developed a new osteosynthesis philosophy based not only on the mechanical and biomechanical interaction of the bone-implant system, but also on the interaction of the biological properties of the bone and the implant. The purpose of the work is to study the interaction of the biological process of the bone - its regeneration (germination) of bone tissue into the holes of the implant. MATERIALS AND METHODS: The experiment was carried out on fourteen Chinchilla rabbits in accordance with all international standards. A perforated implant specially made of titanium (ChM, Poland) was surgically implanted into the proximal femur. The implant measurements were as follows: length - 6 mm, width - 3 mm, thickness - 2 mm, 2 holes with a diameter of 2 mm. The 14 rabbits were divided into 7 groups. After 1, 2, 3, 4, 5, 10 and 12 weeks the animals were withdrawn from the experiment according to the standard rules in sequential order. The preparations were placed in a formalin solution and sent to the pathomorphology laboratory (CITO, Russia) for histological studies. RESULTS: Weekly histopathological studies revealed a gradual transition from the organization of a hematoma to the formation of mature bone tissue in the holes of the implants. The titanium implant is bioinert and did not cause any visible reactions from the bone tissue. Simultaneous integration of vascular proliferation and newly formed bone tissue into the implant holes were revealed. On 10-12-week preparations, the formation of trabecular structures of mature bone tissue was revealed in the holes of the implants and elements of adipose and bone marrow tissue were observed. Macroscopic examination of 4-5-week preparations showed almost complete filling of the holes with bone tissue. On 10-12-week preparations, the bone tissue in the holes of the implants did not differ from the bone tissue surrounding the implant. The processes of formation of mature bone tissue in the holes of the implants were similar to the processes of physiological bone healing (regeneration) at the fracture site. CONCLUSIONS: The obtained results show the following: 1.The titanium implant is bioinert and does not cause any visible reactions from the bone tissue; 2. There is a gradual process of formation of new vessels, and then the formation of new bone tissue in the holes of the implant instead of the one damaged during implantation. Thus, the results of this experiment indirectly confirm our assumption that a perforated implant for FNF osteosynthesis will participate not only in the mechanical and biomechanical interaction of the bone-implant system, but will also include the 3rd element in this system - the biological properties of the bone itself. We assume that these properties of the new implant will increase blood flow in the femoral neck and partially replenish the volume of bone tissue destroyed during osteosynthesis which does not occur with FNF osteosynthesis by any of the known implants.

Efficiency of an implant: new criterion of objective assessment of implants for osteosynthesis of femoral neck fracture.

PURPOSE: In line with several designs for osteosynthesis of femoral neck fracture (FNF), their effectiveness is still estimated by the results of biomechanical and clinical trials, finite element method (FE). But surgeons require the criteria which would define their properties in advance and allow improve the results of treatment. METHODS: When new implant (NI) is being designed, we developed such criterion - index efficiency of an implant (IEI) - and performed mathematical comparative researches of properties of NI with the known designs. We analyzed the results of comparative clinical trials on treatment of FNF with various implants considering their IEI. RESULTS: Analysis showed that results of comparative clinical trials with the use of various implants for osteosynthesis FNF completely correlated to their IEI; IEI of the NI two to three times exceeds IEI of all known designs, and the destruction percentage of a bone tissue is two to three times less when it is applied. CONCLUSION: The offered IEI can be used for designing new implants and allows improving the results of treatment of patients with FNF by optimizing the choice of implant for osteosynthesis.

Perforated H-beam implant can be used in femoral neck fracture.

This biomechanical study evaluated comparison osteosynthesis of the femoral neck fracture model by 3 cannulated screw implants and new perforated H beam implants under different loading conditions with 45 third generation right proximal femur bones. A standardized Pauwels Type 3 of the femoral neck fracture was performed in the femur models. For assessing the rigidity and strength of fixation methods, the proximal femur bones after their osteosynthesis were then mechanically tested in axial compression, and torsional and dynamic axial compression loading. To determine the structural advantage of the new implant system, perforated and nonperforated new implant systems were comparing about pull out performance. When loading the samples, photographs were taken continuously. The reference parameters were described and measured from unloaded and loaded photographs of the static and dynamic tests. There was no significant difference between stiffness values of two fixation methods under static and rotational loading. Under dynamic loading, the displacement of the superior point of femoral head at the fracture line showed a significant decrease between the new implant system and cannulated screws. Comparing the relative motion at the mid line of the fracture in femoral neck between groups, a significant increase was found in H Beam implant group. Perforated H beam implants have similar static and torsion properties with golden standard. Although there was significant difference under dynamic loading which simulate movement early after surgery, the patient was not allowed to move early after surgery in the clinical practice. Therefore, the differences due to the perforated "H" beam implant would not cause clinical insecurity. Therefore, it is assumed that the perforated "H" beam implant can be used for internal fixation as an alternative to cannulated screws in the treatment of instable femoral neck fracture.