Prosthesis loosening is the leading cause of postoperative revision in unicompartmental knee arthroplasty (UKA). The deviation of medial and lateral translational installation of the prosthesis during surgery is a common clinical phenomenon and an important factor in increasing the risk of prosthesis loosening. This study established a UKA finite element model and a bone-prosthesis fixation interface micromotion prediction model. The predicted medial contact force and joint motion of the knee joint from a patient-specific lower extremity musculoskeletal multibody dynamics model of UKA were used as boundary conditions. The effects of 9 femoral component medial and lateral translational installation deviations on the Von Mises stress of the proximal tibia, the contact stress, and the micro-motion of the bone prosthesis fixation interface were quantitatively studied. It was found that compared with the neutral position (a/A of 0.492), the lateral translational deviation of the femoral component significantly increased the tibial Von Mises stress and the bone-prosthesis fixation interface contact stress. The maximum Von Mises stress and the maximum contact stress of the fixation interface increased by 14.08% and 143.15%, respectively, when a/A was 0.361. The medial translational deviation of the femoral component significantly increased the bone-prosthesis fixation interface micro-motion. The maximum value of micromotion under the conditions of femoral neutral and medial translation deviation was in the range of 20-50 μm, which is suitable for osseointegration. Therefore, based on considerations such as the micromotion range suitable for osseointegration reported in the literature, the risk of reducing prosthesis loosening, and factors that may induce pain, it is recommended that clinicians control the mounting position of the femoral component during surgery within the safe range of 0-4 mm medial translation deviation.
Humans ; Arthroplasty, Replacement, Knee/methods* ; Finite Element Analysis ; Biomechanical Phenomena ; Knee Prosthesis ; Tibia/surgery* ; Femur/surgery* ; Stress, Mechanical ; Prosthesis Failure ; Knee Joint/surgery* ; Prosthesis Design

Although metal blocks have been widely used for reconstructing uncontained tibial bone defects, the influence of their elastic modulus on the stability of tibial prosthesis fixation remains unclear. Based on this, a finite element model incorporating constrained condylar knee (CCK) prosthesis, tibia, and metal block was established. Considering the influence of the post-restraint structure of the prosthesis, the effects of variations in the elastic modulus of the block on the von Mises stress distribution in the tibia and the block, as well as on the micromotion at the bone-prosthesis fixation interface, were investigated. Results demonstrated that collision between the insert post and femoral prosthesis during tibial internal rotation increased tibial von Mises stress, significantly influencing the prediction of block elastic modulus variation. A decrease in the elastic modulus of the metal block resulted in increased von Mises stress in the proximal tibia, significantly reduced von Mises stress in the distal tibia, decreased von Mises stress of the block, and increased micromotion at the bone-prosthesis fixation interface. When the elastic modulus of the metal block fell below that of bone cement, inadequate block support substantially increased the risk of stress shielding in the distal tibia and fixation interface loosening. Therefore, this study recommends that biomechanical investigations of CCK prostheses must consider the post-constraint effect, and the elastic modulus of metal blocks for bone reconstruction should not be lower than 3 600 MPa.
Knee Prosthesis ; Humans ; Finite Element Analysis ; Tibia/surgery* ; Elastic Modulus ; Arthroplasty, Replacement, Knee/methods* ; Stress, Mechanical ; Metals ; Prosthesis Design ; Knee Joint/surgery* ; Biomechanical Phenomena

Stent migration is one of the common complications following transcatheter valve implantation. This study aims to design a "drum-shaped" balloon-expandable aortic valve stent to address this issue and conduct a mechanical analysis. The implantation process of the stent was evaluated using a method that combines numerical simulation and in vitro experiments. Furthermore, the fatigue process of the stent under pulsatile cyclic loading was simulated, and its fatigue performance was assessed using a Goodman diagram. The process of the stent migrating toward the left ventricular side was simulated, and the force-displacement curve of the stent was extracted to evaluate its anti- migration performance. The results showed that all five stent models could be crimped into a 14F sheath and enabled uniform expansion of the native valve leaflets. The stress in each stent was below the ultimate stress, so no fatigue fracture occurred. As the cell height ratio decreased, the contact area fraction between the stent and the aortic root gradually decreased. However, the mean contact force and the maximum anti-migration force first decreased and then increased. Specifically, model S5 had the smallest contact area fraction but the largest mean contact force and maximum anti-migration force, reaching approximately 0.16 MPa and 10.73 N, respectively. The designed stent achieves a "drum-shaped" change after expansion and has good anti-migration performance.
Stents ; Prosthesis Design ; Heart Valve Prosthesis ; Humans ; Aortic Valve/surgery* ; Stress, Mechanical ; Transcatheter Aortic Valve Replacement/instrumentation*

The post-and-core is a widely accepted method to restore endodontically treated teeth with compromised tooth structure. Currently, cast metal post-and-core systems and prefabricated fiber posts combined with composite resin cores are the most frequently options in dental clinical practice, but both also come with advantages and limitations. The development of computer-aided design/computer-aided manufacturing (CAD/CAM) custom fiber post-and-core represents one of the significant trends in the advancement of dentistry. Society of Digital Dental Industry, National Association of Health Industry and Enterprise Management organized experts to formulate Guidelines for CAD/CAM custom fiber post-and-core, standardizing the clinical operation procedures of this technology, enhancing the success rate of CAD/CAM custom fiber post-and-core, and promoting its application and development.
Computer-Aided Design ; Humans ; Post and Core Technique ; Composite Resins ; Dental Prosthesis Design

OBJECTIVE: To analyze the short-term effectiveness and safety of personalized three-dimensional (3D) printed customized prostheses in severe Paprosky type Ⅲ acetabular bone defects. METHODS: A retrospective analysis was conducted on 8 patients with severe Paprosky type Ⅲ acetabular bone defects and met the selection criteria between January 2023 and June 2024. There were 3 males and 5 females, with an average age of 64.6 years ranged from 56 to 73 years. All primary replacement prostheses were non-cemented, including 1 ceramic-ceramic interface, 1 ceramic-polyethylene interface, and 6 metal-polyethylene interfaces. The time from the primary replacement to the revision was 4 days to 18 years. The reasons for revision were aseptic loosening in 5 cases, revision after exclusion in 2 cases, and repeated dislocation in 1 case. The preoperative Harris score was 39.5±3.7 and the visual analogue scale (VAS) score was 7.1±0.8. The operation time, intraoperative blood loss, hospital stay, and complications were recorded. The hip function was evaluated by Harris score, and the degree of pain was evaluated by VAS score. The acetabular cup abduction angle, anteversion angle, rotational center height, greater trochanter height, and femoral offset were measured on X-ray film. RESULTS: The operation time was 95-223 minutes, with an average of 151.13 minutes. The intraoperative blood loss was 600-3 500 mL, with an average of 1 250.00 mL. The hospital stay was 13-20 days, with an average of 16.88 days. All 8 patients were followed up 2-12 months, with an average of 6.4 months. One patient had poor wound healing after operation, which healed well after active symptomatic treatment. One patient had lower limb intermuscular vein thrombosis, but no thrombosis was found at last follow-up. No serious complications such as aseptic loosening, infection, dislocation, and periprosthetic fracture occurred during the follow-up. At last follow-up, the Harris score was 72.0±6.2 and the VAS score was 1.8±0.7, which were significantly different from those before operation ( t=-12.011, P<0.001; t=16.595, P<0.001). On the second day after operation, the acetabular cup abduction angle ranged from 40° to 49°, with an average of 44.18°, and the acetabular cup anteversion angle ranged from 19° to 26°, with an average of 21.36°, which were within the "Lewinneck safety zone". There was no significant difference in the rotational center height, greater trochanter height, and femoral offset between the healthy side and the affected side ( P>0.05). CONCLUSION The use of personalized 3D printed customized prostheses for the reconstruction of severe Paprosky type Ⅲ acetabular bone defects can alleviate pain and enhances hip joint function, and have good postoperative prosthesis position, without serious complications and have good safety.
Humans ; Printing, Three-Dimensional ; Male ; Female ; Middle Aged ; Acetabulum/surgery* ; Aged ; Retrospective Studies ; Hip Prosthesis ; Prosthesis Design ; Arthroplasty, Replacement, Hip/instrumentation* ; Reoperation ; Treatment Outcome

OBJECTIVE: To evaluate precise assessment methods for predicting the optimal acetabular cup size in total hip arthroplasty (THA). METHODS: A clinical data of 73 patients (80 hips) who underwent primary THA between December 2022 and July 2024 and met the inclusion criteria was analyzed. There were 39 males and 34 females with an average age of 66.3 years (range, 56-78 years). Among them, 66 cases were unilateral THA and 7 were bilateral THAs. There were 29 patients (34 hips) of osteoarthritis, 35 patients (35 hips) of femoral neck fractures, and 9 patients (11 hips) of osteonecrosis of the femoral head. Based on anteroposterior pelvic X-ray films, three methods were employed to predict acetabular cup size, including preoperative template planning, radiographic femoral head diameter (FHD) measurement, and intraoperative FHD measurement. The predicted acetabular cup sizes from these methods were compared with the actual implanted sizes. RESULTS: The predicted acetabular cup sizes using the preoperative template planning, radiographic FHD measurement, and intraoperative FHD measurement were (51.25±2.81), (49.72±3.11), and (49.90±2.74) mm, respectively, compared to the actual implanted cup size of (50.57±2.74) mm, with no significant difference ( P>0.05). Regarding agreement with the actual implanted cup size, the preoperative template planning achieved exact matches in 35 hips (43.75%), one-size deviation in 41 hips (51.25%), and two-size deviations in 4 hips (5%); the radiographic FHD measurement achieved exact matches in 12 hips (15%), one-size deviation in 57 hips (71.25%), and two-size deviations in 11 hips (13.75%); and the intraoperative FHD measurement achieved exact matches in 26 hips (32.5%), one-size deviation in 52 hips (65%), and two-size deviations in 2 hips (2.5%). There were significant differences in agreement distributions between the three methods and the actual implanted cup sizes ( H=18.579, P<0.001). CONCLUSION The intraoperative FHD measurement, as a simple, cost-effective, and accurate method, effectively guides acetabular cup selection, reduces the risk of prosthesis wear, enhances postoperative joint stability.
Humans ; Arthroplasty, Replacement, Hip/instrumentation* ; Male ; Female ; Middle Aged ; Acetabulum/diagnostic imaging* ; Aged ; Hip Prosthesis ; Prosthesis Design ; Femur Head/surgery* ; Osteoarthritis, Hip/surgery* ; Radiography ; Femoral Neck Fractures/surgery* ; Femur Head Necrosis/surgery*

OBJECTIVE: To analyze the effectiveness of single three-dimensional (3D)-printed microporous titanium prostheses and flap combined prostheses implantation in the treatment of large segmental infectious bone defects in limbs. METHODS: A retrospective analysis was conducted on the clinical data of 76 patients with large segmental infectious bone defects in limbs who were treated between January 2019 and February 2024 and met the selection criteria. Among them, 51 were male and 25 were female, with an age of (47.7±9.4) years. Of the 76 patients, 51 had no soft tissue defects (single prostheses group), while 25 had associated soft tissue defects (flap combined group). The single prostheses group included 28 cases of tibial bone defects, 11 cases of femoral defects, 5 cases of humeral defects, 4 cases of radial bone defects, and 3 cases of metacarpal, or carpal bone defects, with bone defect length ranging from 3.5 to 28.0 cm. The flap combined group included 3 cases of extensive dorsum of foot soft tissue defects combined with large segmental metatarsal bone defects, 19 cases of lower leg soft tissue defects combined with large segmental tibial bone defects, and 3 cases of hand and forearm soft tissue defects combined with metacarpal, carpal, or radial bone defects, with bone defect length ranging from 3.8 to 32.0 cm and soft tissue defect areas ranging from 8 cm×5 cm to 33 cm×10 cm. In the first stage, vancomycin-loaded bone cement was used to control infection, and flap repair was performed in the flap combined group. In the second stage, 3D-printed microporous titanium prostheses were implanted. Postoperative assessments were performed to evaluate infection control and bone integration, and pain release was evaluated using the visual analogue scale (VAS) score. RESULTS: All patients were followed up postoperatively, with an average follow-up time of (35.2±13.4) months. In the 61 lower limb injury patients, the time of standing, walk with crutches, and fully bear weight were (2.2±0.6), (3.9±1.1), and (5.4±1.1) months, respectively. The VAS score at 1 year postoperatively was significantly lower than preoperative one ( t=-10.678, P<0.001). At 1 year postoperatively, 69 patients (90.8%) showed no complication such as infection, fracture, prosthesis displacement, or breakage, and X-ray films indicated good integration at the prosthesis-bone interface. According to the Paley scoring system for the healing of infectious bone defects, the results were excellent in 37 cases, good in 29 cases, fair in 3 cases, and poor in 7 cases. In the single prostheses group, during the follow-up, there was 1 case each of femoral prostheses fracture, femoral infection, and tibial infection, with a treatment success rate of 94.1% (48/51). In lower limb injury patients, the time of fully bear weight was (5.0±1.0) months. In the flap combined group, during the follow-up, 1 case of tibial fixation prostheses screw fracture occurred, along with 2 cases of recurrent foot infection in diabetic patients and 1 case of tibial infection. The treatment success rate was 84.0% (21/25). The time of fully bear weight in lower limb injury patients was (5.8±1.2) months. The overall infection eradication rate for all patients was 93.4% (71/76). CONCLUSION The use of 3D-printed microporous titanium prostheses, either alone or in combination with flaps, for the treatment of large segmental infectious bone defects in the limbs results in good effectiveness with a low incidence of complications. It is a feasible strategy for the reconstruction of infectious bone defects.
Humans ; Male ; Female ; Middle Aged ; Printing, Three-Dimensional ; Titanium ; Retrospective Studies ; Surgical Flaps ; Adult ; Prosthesis Implantation/methods* ; Plastic Surgery Procedures/methods* ; Treatment Outcome ; Prostheses and Implants ; Bone Diseases, Infectious/surgery* ; Extremities/surgery* ; Prosthesis Design

OBJECTIVE: To compare the biomechanical properties of personalized Y-shaped plates with horizontal plates, vertical plates, and traditional Y-shaped plates in the treatment of distal humeral intra-articular fractures through finite element analysis, and to evaluate their potential for clinical application. METHODS: The study selected a 38-year-old male volunteer and obtained a three-dimensional model of the humerus by scanning his upper limbs using a 64-slice spiral CT. Four types of fracture-internal fixation models were constructed using Mimics 19.0, Geomagic Wrap 2017, Creo 6.0, and other software: horizontal plates, vertical plates, traditional Y-shaped plate, and personalized Y-shaped plate. The models were then meshed using Hypermesh 14.0 software, and material properties and boundary conditions were defined in Abaqus 6.14 software. AnyBody 7.3 software was used to simulate elbow flexion and extension movements, calculate muscle strength, joint forces, and load torques, and compare the peak stress and maximum displacement of the four fixation methods at different motion angles (10°, 30°, 50°, 70°, 90°, 110°, 130°, 150°) during elbow flexion and extension. RESULTS: Under dynamic loading during elbow flexion and extension, the personalized Y-shaped plate exhibits significant biomechanical advantages. During elbow flexion, the peak internal fixation stress of the personalized Y-shaped plate was (28.8±0.9) MPa, which was significantly lower than that of the horizontal plates, vertical plates, and traditional Y-shaped plate ( P<0.05). During elbow extension, the peak internal fixation stress of the personalized Y-shaped plate was (18.1±1.6) MPa, which was lower than those of the other three models, with significant differences when compared with horizontal plates and vertical plates ( P<0.05). Regarding the peak humeral stress, the personalized Y-shaped plate model showed mean values of (10.9±0.8) and (13.1±1.4) MPa during elbow flexion and extension, respectively, which were significantly lower than those of the other three models ( P<0.05). Displacement analysis showed that the maximum displacement of the humerus with the personalized Y-shaped plate during elbow flexion was (2.03±0.08) mm, slightly higher than that of the horizontal plates, but significantly lower than that of the vertical plates, showing significant differences ( P<0.05). During elbow extension, the maximum displacement of the humerus with the personalized Y-shaped plate was (1.93±0.13) mm, which was lower than that of the other three models, with significant differences when compared with vertical plates and traditional Y-shaped plates ( P<0.05). Stress contour analysis showed that the stress of the personalized Y-shaped plate was primarily concentrated at the bifurcation of the Y-shaped structure. Displacement contour analysis showed that the personalized Y-shaped plate effectively controlled the displacement of the distal humerus during both flexion and extension, demonstrating excellent stability. CONCLUSION The personalized Y-shaped plate demonstrates excellent biomechanical performance in the treatment of distal humeral intra-articular fractures, with lower stress and displacement, providing more stable fixation effects.
Humans ; Male ; Adult ; Healthy Volunteers ; Finite Element Analysis ; Tomography, Spiral Computed ; Models, Anatomic ; Biomechanical Phenomena ; Humeral Fractures, Distal/surgery* ; Fracture Fixation, Internal/instrumentation* ; Bone Plates ; Computer Simulation ; Precision Medicine/methods* ; Elbow Joint/surgery* ; Elbow/surgery* ; Humerus/surgery* ; Torque ; Stress, Mechanical ; Intra-Articular Fractures/surgery* ; Prosthesis Design/methods* ; Imaging, Three-Dimensional ; Range of Motion, Articular

OBJECTIVE: To investigate the effectiveness of three-dimensional (3D) printed customized hemi-pelvic prosthesis for pelvic reconstruction after resection of massive pelvic tumors. METHODS: A retrospective analysis was conducted on 26 patients with massive pelvic tumors who met the selection criteria and were treated between November 2021 and May 2024. The cohort included 11 males and 15 females, with a mean age of 52.65 years (range, 17-73 years). Histopathological diagnoses were as follows: 9 cases of chondrosarcoma, 2 of undifferentiated pleomorphic sarcoma, 4 of spindle cell sarcoma, 2 of osteosarcoma, 1 of solitary fibrous tumor, 1 of myxoid chondroma, 1 of malignant peripheral nerve sheath tumor, 1 of chondromyxoid epithelioma, and 5 of metastatic malignant tumors. According to the Enneking classification, tumor involvement was distributed as 4 cases in zones Ⅰ+Ⅱ, 9 in zones Ⅱ+Ⅲ, 3 in zones Ⅰ+Ⅳ, 8 in zones Ⅰ+Ⅱ+Ⅲ, and 2 in zones Ⅰ+Ⅱ+Ⅳ. The disease duration ranged from 3 to 40 months, with a mean of 9.85 months. All patients underwent reconstruction with customized 3D-printed hemi-pelvic prostheses. The effectiveness was evaluated by Musculoskeletal Tumor Society (MSTS) score and Harris hip score before operation and at last follow-up, and pain levels were evaluated by visual analogue scale (VAS) score before operation, at 3 months after operation, and at last follow-up. RESULTS: The operation time ranged from 186 to 528 minutes, with a mean of 334.58 minutes. The intraoperative blood loss ranged from 1 400 to 4 000 mL, with a mean of 2173.08 mL, and the transfusion volume ranged from 750 to 3 500 mL, with a mean of 1 659.62 mL. All 26 patients were followed up 10-42 months (mean, 18.5 months). Postoperative complications included prosthetic dislocation in 2 cases, which were attributed to improper positioning during home care and an accidental fall, respectively. One patient developed a vesicocutaneous fistula and poor wound healing due to pre-existing tumor invasion into the bladder. One patient experienced failure and loosening of the internal fixation at 8 months after operation caused by local tumor recurrence, and subsequently died at 14 months postoperatively due to progression of brain metastases. Postoperative complications such as poor healing of incisions, prosthetic dislocation, or failure of internal fixation was not observed in the remaining patients. At last follow-up, the walking ability of most patients recovered to varying degrees. The VAS scores at 3 months and at last follow-up significantly improved when compared with those before operation, and the scores at last follow-up further improved when compared with 3 months after operation, all showing significant differences ( P<0.05). The MSTS scores and Harris scores at last follow-up were significantly higher than those before operation ( P<0.05). CONCLUSION 3D printed customized hemi-pelvic prosthesis is effective for reconstruction of massive pelvic tumors after resection, but there are still some limitations, and soft tissue reconstruction should be paid attention to.
Humans ; Printing, Three-Dimensional ; Female ; Male ; Adult ; Plastic Surgery Procedures/methods* ; Retrospective Studies ; Middle Aged ; Aged ; Pelvic Bones/surgery* ; Bone Neoplasms/surgery* ; Adolescent ; Pelvic Neoplasms/surgery* ; Prosthesis Design ; Young Adult ; Treatment Outcome ; Prostheses and Implants

OBJECTIVE: To evaluate the feasibility and short-term effectiveness of three-dimensional (3D)-printed customized porous acetabular components for reconstruction of extensive acetabular bone defects during primary total hip arthroplasty (THA). METHODS: The clinical data of 8 patients with extensive acetabular bone defects, who were treated with 3D-printed individualized porous acetabular components between July 2018 and January 2022, were retrospectively analyzed. The cohort comprised 4 males and 4 females with an average age of 48 years ranging from 34 to 56 years. Acetabular bone defects were classified as Paprosky type ⅢA in 3 cases and type ⅢB in 5 cases. The causes of acetabular destruction were hip tuberculosis (5 cases), pigmented villonodular synovitis (2 cases), and syphilitic arthritis (1 case). Visual analogue scale (VAS) score and Harris hip score (HHS) were used to evaluate the pain relief and hip function before and after operation. Reconstruction outcomes were further assessed by imaging results [X-ray film and Tomosynthesis Shimadzumetal artefact reduction technology (T-SMART)], and the mechanical properties were evaluated by finite element analysis. RESULTS: The operation time ranged from 174 to 195 minutes (mean, 187 minutes), and intraoperative blood loss ranged from 390 to 530 mL (mean, 465 mL). All 8 patients were follow-up 26-74 months (mean, 44 months). Among the 5 patients with tuberculosis, none experienced postoperative recurrence. At last follow-up, the VAS score was 0.3±0.5 and the HHS score was 87.9±3.7, both significantly improved compared to preoperative values ( t=25.170, P<0.001; t=-28.322, P<0.001). X-ray films at 2 years after operation demonstrated satisfactory matching between the 3D-printed customized acetabular component and the acetabulum. The postoperative center of rotation of the operated hip was shifted by (2.1±0.5) mm horizontally and (2.0±0.7) mm vertically relative to the contralateral side, with both offsets showing significant differences compared to preoperative values ( t=24.700, P<0.001; t=55.230, P<0.001). T-SMART imaging showed satisfactory osseointegration at the implant-host bone interface. No complications such as aseptic loosening or screw breakage was observed during follow-up. Finite element analysis showed that the acetabular component had good mechanical properties. CONCLUSION The application of 3D-printed individualized porous acetabular components in the reconstruction of extensive acetabular bone defects demonstrated precise anatomical reconstruction, stable mechanical support, and good functional performance in short-term follow-up, offering a potential alternative for acetabular defect reconstruction in primary THA.
Humans ; Middle Aged ; Male ; Female ; Printing, Three-Dimensional ; Arthroplasty, Replacement, Hip/instrumentation* ; Acetabulum/diagnostic imaging* ; Adult ; Follow-Up Studies ; Retrospective Studies ; Hip Prosthesis ; Prosthesis Design ; Porosity ; Treatment Outcome ; Plastic Surgery Procedures/methods*