Personalized digital simulation­assisted acetabular component implantation in revision hip arthroplasty.

The number of artificial total hip revision arthroplasties is increasing yearly in China, and >50% of these cases have acetabular defects. Accurately locating and quantifying the bone defect is one of the current challenges of this surgery. Thus, the objective of the present study was to simulate acetabular implantation with the aid of Mimics 17.0 software (Materialise NV) in patients with loosened acetabular prosthesis, to evaluate the 'ideal acetabular center' and the 'actual acetabular center' to guide the choice of prosthesis and surgical method. From January 2017 to June 2021, the present study included 10 hips from 10 patients [seven men (seven hips) and three women (three hips)]. In all patients, the Mimics software was applied to simulate the dislocation of the femoral prosthesis and acetabular prosthesis implantation before surgery; calculate the height difference between the 'ideal acetabular center' and the 'actual acetabular center' to assess the bone defect; confirm the size of the acetabular prosthesis, abduction angle, anteversion angle and bone coverage of the acetabular cup; and measure the intraoperative bleeding and postoperative follow-up Harris score of the hip joint. After statistical analysis, the present study revealed that digital simulation assistance could improve the accuracy of hip revision acetabular prosthesis implantation, reduce postoperative shortening of the affected limb, especially for surgeons with relatively little experience in hip revision surgery, and greatly reduce the occurrence of complications such as hip dislocation because of poor postoperative prosthesis position.

[Application of personalized digital analog assisted acetabular prosthesis precise implantation in Crowe typeâ and â ¡ hip dysplasia].

OBJECTIVE: To explore the effect of personalized digital analog assisted acetabular prosthesis precise implantation in hip dysplasia. METHODS: From February 2017 to July 2019, 11 patients(12 hips) with hip dysplasia underwent total hip arthroplasty, including 4 males(5 hips) and 7 females(7 hips), aged from 27 to 61 years old, with an average of (46.64±12.93) years old;Crowe classification:8 hips in typeⅠ and 4 hips in typeⅡ. The preoperative thin-layer CT scan was imported into Mimics 10.01 software. The appropriate size and placement angle of acetabular prosthesis were selected through preoperative simulation, and the acetabular bone defect was understood to determine whether structural bone grafting was needed during the operation. The length of both lower limbs, the anteversion angle of acetabular prosthesis, the abduction angle, the height of acetabular rotation center and the horizontal distance of hip joint center before and after the operation were measured, and the postoperative dislocation, bone graft healing and acetabular cup loosening were observed. The hip Harris score was used to evaluate the joint function. RESULTS: All patients were followed up for 18 to 30 months with an average of (23.45±3.70) months. There was no prosthesis dislocation, loosening and bone graft healing after operation. One case had numbness in the innervation area due to the traction of sciatic nerve during operation, and was treated with neurotrophic drugs and recovered one month after operation. The length difference of both lower limbs decreased from (31.73±5.98) mm before operation to (4.73±1.90) mm 3 months after operation (t=15.268, P<0.01). The anteversion angle of acetabular cup and acetabulum was (17.45±3.62)°and abduction angle was (40.10 ± 2.30)° after operation. In all cases, the abduction angle and anteversion angle were within the safe range of Lewinek. The height of hip rotation center was (20.64±2.58) mm and the horizontal inward displacement of hip was (33.46±3.61) mm. Harris score increased from (45.36±2.34) before operation to (91.27±2.37) 3 months after operation (P<0.05). CONCLUSION: Through preoperative personalized digital analog reconstruction of acetabulum in patients with hip dysplasia, we can better understand the acetabular defect, help to evaluate the size and placement angle of acetabular prosthesis and whether structural bone grafting is needed, and obtain satisfactory clinical curative effect.

Biomechanical study of injectable hollow pedicle screws for PMMA augmentation in severely osteoporotic lumbar vertebrae: effect of PMMA distribution and volume on screw stability.

OBJECTIVEThe purpose of this study was to compare stability of injectable hollow pedicle screws with different numbers of holes using different volumes of polymethylmethacrylate (PMMA) in severely osteoporotic lumbar vertebrae and analyze the relationship between screw stability and distribution and volume of PMMA.METHODSForty-eight severely osteoporotic cadaveric lumbar vertebrae were randomly divided into 3 groups-groups A, B, and C (16 vertebrae per group). The screws used in group A had 4 holes (2 pairs of holes, with the second hole of each pair placed 180° further along the thread than the first). The screws used in group B had 6 holes (3 pairs of holes, placed with the same 180° difference in position). Unmodified conventional screws were used in group C. Each group was randomly divided into subgroups 0, 1, 2, and 3, with different volumes of PMMA used in each subgroup. Type A and B pedicle screws were directly inserted into the vertebrae in groups A and B, respectively, and then different volumes of PMMA were injected through the screws into the vertebrae in subgroups 0, 1, 2, and 3. The pilot hole was filled with different volumes of PMMA followed by insertion of screws in groups C0, C1, C2, and C3. Distributions of PMMA were evaluated radiographically, and axial pull-out tests were performed to measure the maximum axial pullout strength (Fmax).RESULTSRadiographic examination revealed that PMMA surrounded the anterior third of the screws in the vertebral bodies (VBs) in groups A1, A2, and A3; the middle third of screws in the junction area of the vertebral body (VB) and pedicle in groups B1, B2, and B3; and the full length of screws evenly in both VB and pedicle in groups C1, C2, and C3. In addition, in groups A3 and B3, PMMA from each of the screws (left and right) was in contact with PMMA from the other screw and the PMMA was closer to the posterior wall and pedicle than in groups A1, A2, B1, and B2. One instance of PMMA leakage was found (in group B3). Two-way analysis of variance revealed that 2 factors-distribution and volume of PMMA-significantly influenced Fmax (p < 0.05) but that they were not significantly correlated (p = 0.078). The Fmax values in groups in which screws were augmented with PMMA were significantly better than those in groups in which no PMMA was used (p < 0.05).CONCLUSIONSPMMA can significantly improve stability of different injectable pedicle screws in severely osteoporotic lumbar vertebrae, and screw stability is significantly correlated with distribution and volume of PMMA. The closer the PMMA is to the pedicle and the greater the quantity of injected PMMA used, the greater the pedicle screw stability is. Injection of 3.0 mL PMMA through screws with 4 holes (2 pair of holes, with the screws in each pair placed on opposite sides of the screw) produces optimal stability in severely osteoporotic lumbar vertebrae.

Biomechanical comparative study of the stability of injectable pedicle screws with different lateral holes augmented with different volumes of polymethylmethacrylate in osteoporotic lumbar vertebrae.

BACKGROUND CONTEXT: Polymethylmethacrylate (PMMA) is widely used for pedicle screw augmentation in osteoporosis. Until now, there had been no studies of the relationship between screw stability and the distribution and volume of PMMA. PURPOSE: The objective of this study was to analyze the relationship between screw stability and the distribution pattern and injected volume of PMMA. STUDY DESIGN: This is a biomechanical comparison of injectable pedicle screws with different lateral holes augmented with different volumes of PMMA in cadaveric osteoporotic lumbar vertebrae. METHODS: Forty-eight osteoporotic lumbar vertebrae were randomly divided into Groups A, B, and C with different pedicle screws (16 vertebrae in each group), and then each group was randomly divided into Subgroups 0, 1, 2, and 3 with different volumes of PMMA (four vertebra with eight pedicles in each subgroup). A pilot hole was prepared in advance using the same method in all samples. Type A and type B pedicle screws were directly inserted into vertebrae in Groups A and B, respectively, and then different volumes of PMMA (0, 1.0, 1.5, and 2.0 mL) were injected through the screws and into vertebrae in Subgroups 0, 1, 2, and 3. The pilot holes were filled with different volumes of PMMA (0, 1.0, 1.5, and 2.0 mL), and then the screws were inserted in Groups C0, C1, C2, and C3. Screw position and distribution of PMMA were evaluated radiographically, and axial pullout tests were performed to measure maximum axial pullout strength (Fmax). RESULTS: Polymethylmethacrylate surrounded the anterior one-third of screws in the vertebral body in Groups A1, A2, and A3; the middle one-third of screws in the junction area of the vertebral body and the pedicle in Groups B1, B2, and B3; and the full length of screws evenly in both the vertebral body and the pedicle in Groups C1, C2, and C3. There was no malpositioning of screws or leakage of PMMA in any sample. Two-way analysis of variance revealed that two factors-distribution and volume of PMMA-significantly influenced Fmax (p<.05) but that they were not significantly correlated (p=.088). Fmax values in groups using augmentation with PMMA values significantly improved compared with those in groups without PMMA (p<.05). CONCLUSIONS: Polymethylmethacrylate can significantly enhance the stability of different injectable pedicle screws in osteoporotic lumbar vertebrae, and screw stability is significantly correlated with the distribution pattern and the injected volume of PMMA. The closer the PMMA to the pedicle and the greater the quantity of injected PMMA, the greater is the pedicle screw stability. Injection of 2.0 mL of PMMA through screws with four lateral 180° holes or of 1.0 mL of PMMA through screws with six lateral 180° holes increases the stability of pedicle screws.

Biomechanical Property of a Newly Designed Assembly Locking Compression Plate: Three-Dimensional Finite Element Analysis.

In this study, we developed and validated a refined three-dimensional finite element model of middle femoral comminuted fracture to compare the biomechanical stability after two kinds of plate fixation: a newly designed assembly locking compression plate (NALCP) and a locking compression plate (LCP). CT data of a male volunteer was converted to middle femoral comminuted fracture finite element analysis model. The fracture was fixated by NALCP and LCP. Stress distributions were observed. Under slow walking load and torsion load, the stress distribution tendency of the two plates was roughly uniform. The anterolateral femur was the tension stress area, and the bone block shifted toward the anterolateral femur. Maximum stress was found on the lateral border of the number 5 countersink of the plate. Under a slow walking load, the NALCP maximum stress was 2.160e+03 MPa and the LCP was 8.561e+02 MPa. Under torsion load, the NALCP maximum stress was 2.260e+03 MPa and the LCP was 6.813e+02 MPa. Based on those results of finite element analysis, the NALCP can provide adequate mechanical stability for comminuted fractures, which would help fixate the bone block and promote bone healing.

Biomechanical comparison of pedicle screw augmented with different volumes of polymethylmethacrylate in osteoporotic and severely osteoporotic cadaveric lumbar vertebrae: an experimental study.

BACKGROUND CONTEXT: Polymethylmethacrylate (PMMA) is widely used for pedicle screw augmentation in osteoporosis. Intriguingly, there have been no biomechanical comparisons of the stability of pedicle screws augmented with different volumes of PMMA or studies of the relationship between screw stability and volume of PMMA, especially in different degrees of osteoporosis. PURPOSE: The purposes of the study reported here were to compare screw stability by different volumes of PMMA augmentation, to analyze the relationship between screw stability and PMMA volume, and to make a preliminary determination of the optimum volume of PMMA augmentation for different degrees of osteoporosis. STUDY DESIGN: This study is a biomechanical comparison of pedicle screws augmented with various volumes of PMMA in cadaveric lumbar vertebrae. METHODS: Thirty-six pedicles from 18 osteoporotic lumbar vertebrae were randomly divided into groups A0 through A5, and 36 pedicles from 18 severely osteoporotic lumbar vertebrae were randomly divided into groups B0 through B5. A different volume of PMMA was injected into each one of groups A0 through A5 (0, 0.5, 1.0, 1.5, 2.0, and 2.5 mL, respectively) and into each one of groups B0 through B5 (0, 1.0, 1.5, 2.0, 2.5, and 3.0 mL, respectively), and then pedicle screws were inserted in all vertebrae. After complete solidification of the PMMA, we examined pedicle X-rays, performed axial pullout tests, and determined the maximum axial pullout strength (Fmax) for all samples. RESULTS: No PMMA was found around the screws in groups A0 and B0. In groups A1 to A5 and B1 to B5, screws were wrapped by gradually increasing amounts of PMMA. There was no PMMA leakage or screw malpositioning in any samples. The Fmax in groups A1 through A5 increased by 32.40%, 64.42%, 116.02%, 174.07%, and 207.42%, respectively, compared with that in group A0. There were no significant differences in Fmax between groups A0 and A1, A1 and A2, A2 and A3, A3 and A4, and A4 and A5 (p>.05), but there were significant differences in Fmax between any other two groups (p<.05). The Fmax in groups B1 through B5 increased by 23.48%, 48.40%, 106.60%, 134.73%, and 210.04%, respectively, compared with that in group B0. There were no significant differences in Fmax between groups B0 and B1, B0 and B2, B1 and B2, B2 and B3, B3 and B4 (p>.05), but there were significant differences in Fmax between any other two groups (p<.05). There was a significant positive correlation between Fmax and volume of PMMA in both osteoporotic and severely osteoporotic lumbar vertebrae (p<.05). CONCLUSIONS: Polymethylmethacrylate can significantly enhance stability of pedicle screws in both osteoporotic and severely osteoporotic lumbar vertebrae. There is a significant positive correlation between screw stability and volume of PMMA. Within a certain range, nevertheless, increasing the volume of PMMA does not significantly improve screw stability. We suggest that 1.5 and 3 mL, respectively, are the volumes of injected PMMA that will optimize pedicle screw stability in osteoporotic and severely osteoporotic lumbar vertebrae.

Biomechanical Comparison of Pedicle Screw Augmented with Different Volumes of Polymethylmethacrylate in Osteoporotic and Severely Osteoporotic Synthetic Bone Blocks in Primary Implantation: An Experimental Study.

This study was designed to compare screw stabilities augmented with different volumes of PMMA and analyze relationship between screw stability and volume of PMMA and optimum volume of PMMA in different bone condition. Osteoporotic and severely osteoporotic synthetic bone blocks were divided into groups A0-A5 and B0-B5, respectively. Different volumes of PMMA were injected in groups A0 to A5 and B0 to B5. Axial pullout tests were performed and F max was measured. F max in groups A1-A5 were all significantly higher than group A0. Except between groups A1 and A2, A3 and A4, and A4 and A5, there were significant differences on F max between any other two groups. F max in groups B1-B5 were all significantly higher than group B0. Except between groups B1 and B2, B2 and B3, and B4 and B5, there were significant differences on F max between any other two groups. There was significantly positive correlation between F max and volume of PMMA in osteoporotic and severely osteoporotic blocks. PMMA can significantly enhance pedicle screw stability in osteoporosis and severe osteoporosis. There were positive correlations between screw stability and volume of PMMA. In this study, injection of 3 mL and 4 mL PMMA was preferred in osteoporotic and severely osteoporotic blocks, respectively.

Computer Simulation and Analysis on Flow Characteristics and Distribution Patterns of Polymethylmethacrylate in Lumbar Vertebral Body and Vertebral Pedicle.

This study was designed to analyze the flow and distribution of polymethylmethacrylate (PMMA) in vertebral body through computer simulation. Cadaveric lumbar vertebrae were scanned through electron beam tomography (EBT). The data was imported into Mimics software to build computational model. Vertebral body center and junction of pedicle and vertebral body were chosen as injection points. Silicone oil with viscosity of 100,000 cSt matching with PMMA bone cement was chosen for injection. The flow and distribution of silicone oil were analyzed using Fluent software. In vertebral body, silicone oil formed a circle-like shape centered by injection point on transverse and longitudinal sections, finally forming a sphere-like shape as a whole. Silicone oil diffused along lateral and posterior walls forming a circle-like shape on transverse section centered by injection point in pedicle, eventually forming a sphere-like shape as a whole. This study demonstrated that silicone oil flowed and diffused into a circle-like shape centered by injection point and finally formed a sphere-like shape as a whole in both vertebral body and pedicle. The flow and distribution of silicon oil in computational model could simulate PMMA distribution in vertebral body. It may provide theoretical evidence to reduce PMMA leakage risk during percutaneous vertebroplasty.

[Changes of MMP-9 and TIMP-1 levels in gingival crevicular fluid during orthodontic tooth movement under orthodontic forces].

AIM: To investigate the dynamic changes of MMP-9 and TIMP-1 levels in gingival crevicular fluid during orthodontic tooth movement under orthodontic forces. METHODS: select 20 cases which fit experiment condition. The cases divided randomly into 2 groups, 1- cases for each group. The distal forces of 100g and 250 g were exerted to the canine on the one side of two groups separately. The GCF were taken before activation and at 1, 2, 3, 4, 5, 6, 7 week respectively after initiation of the experiment. The levels of MMP-9 and TIMP-1 in GCF were determined by ELISA. RESULTS: The levels of MMP-9 in A group began to increase at 1 week and reached to its peak value at 3 week after initiation of the experiment, but the level returned to baseline at 7 week. The levels of TIMP-1 in A group began to increase at 1, 2, 3 week and decreased at 4 week after initiation of the experiment, but the level at 6,7 week was higher than that before initiation of the experiment. The level of MMP-9 in A group was higher than that in B group at all times and the level of TIMP-1 in A group was lower than that in B group. CONCLUSION: The level of MMP-9 and TIMP-1 in GCF may play an importance role in maintaining the health, the regular remodeling of the periodontium and the fast-moving of orthodontic tooth.