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

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*

OBJECTIVE: To compare the influence of different emergence profile of implants in mandibular molar on the peri-implant soft tissue. METHODS: Forty-four implants were divided into two equal groups by mucosal thickness, ≥2 mm (group A) or < 2 mm (group B), and were randomly included in the test group and the control group. In the control group, the patients were treated by a prosthesis with no transmucosal modifications (subgroups A1 and B1). In groups A1 and B1, the prostheses maintained the original emergence profile of the healing abutment. In the test group, the prostheses were designed based on a width-to-height ratio (W/H) of 1.3 ∶ 1 (subgroups A2 and B2). In group A2, the buccal transmucosal configuration design was slightly concave, and in group B2, the prostheses were designed with convex buccal transmucosal configuration. Assessments were made before delivery of the definitive restoration (T0), one month (T1) and 12 months (T2) after loading. The soft tissue and prosthesis information were obtained by intraoral scan and were converted to digital models. The digital models of different time were superimposed together. Buccal mucosal W/H, emergence angle (EA) and buccal mucosal margin recession (ΔGM) were measured. RESULTS: One year after loading, the buccal mucosal margin recession in the test group (groups A2 and B2) was significantly lower than that in the control group (groups A1 and B1). The ΔGM in group A2 was significantly lower than that in group A1 (P=0.033), but in groups B1 and B2, it was not significantly different. The W/H in group A2 increased significantly one month after loading, but remained stable at one year. In the A1 group, the W/H changed little from initial to one month, but increased significantly at one year after loading. The W/H in group B2 remained stable from the beginning to one year, while in group B1, it changed little one month after loading, but increased significantly by one year. CONCLUSION When the initial mucosal thickness was ≥2 mm, the slightly concave prosthesis designed based on the biological W/H significantly maintained the level of buccal mucosa. When the mucosal thickness was < 2 mm, the slightly convex prosthesis design maintained a more stable W/H over one year.
Humans ; Mandible/surgery* ; Molar/surgery* ; Male ; Female ; Adult ; Middle Aged ; Dental Prosthesis Design ; Dental Implants ; Dental Implantation, Endosseous/methods*

OBJECTIVE: To analyze the accuracy of prosthesis size selection in Naton robot-assisted medial unicondyle knee arthroplasty by comparing the actual prosthesis size used during operation and the preoperative planning. METHODS: The clinical data of 100 patients (110 knees) who underwent Naton robot-assisted medial unicondylar knee arthroplasty between June 2023 and July 2024 was retrospectively analyzed, including 47 knees on left side and 63 knees on right side. There were 37 males (40 knees) and 63 females (70 knees) with a mean age of 65.4 years (range, 59-71 years). Body mass index was 22.2-28.6 kg/m ² (mean, 25.4 kg/m ²). The disease duration ranged from 1 to 8 years (mean, 3.4 years). Preoperative planning was performed by Naton robotic surgical system based on lower limb CT data. The final prosthesis size after osteotomy was recorded and compared with the preoperative plan to analyse whether it was consistent with the preoperative plan, as well as the situation of knee flexion and extension gaps (<0.5 mm, >2.0 mm) corresponding to the different models of prostheses. RESULTS: During operation, 5 patients (5 knees) were treated with traditional UKA due to mechanical arm failure, software obstacles, significant bone amputation bias, or loose reference frame, and were excluded from the final analysis. The remaining 95 patients (105 knees) successfully received Naton robot-assisted surgery, and no related complications occurred. The prosthesis size was consistent with the preoperative plan in 101 knees (96.2%) on the femur side, 100 knees (95.2%) on the tibia side, and 97 knees (92.4%) on both femur and tibia sides. The prosthesis size was inconsistent in 3 cases (2.86%) on the femur side alone, 4 cases (3.81%) on the tibial side alone, and 1 case (0.95%) on both femur and tibial sides. Among the prostheses with different models, the flexion and extension gaps were less than 0.5 mm in 3 knees, the flexion gap was less than 0.5 mm and the extension gap was more than 2.0 mm in 3 knees, and the flexion gap was more than 2.0 mm and the extension gap was less than 0.5 mm in 2 knees. CONCLUSION The accuracy of prosthesis size selection for Naton robot-assisted medial unicondylar knee arthroplasty is relatively high.
Humans ; Arthroplasty, Replacement, Knee/instrumentation* ; Female ; Male ; Middle Aged ; Aged ; Knee Prosthesis ; Retrospective Studies ; Robotic Surgical Procedures/methods* ; Prosthesis Design ; Knee Joint/surgery* ; Osteoarthritis, Knee/surgery* ; Range of Motion, Articular

OBJECTIVE: To review research progress on the design, manufacturing, and clinical application of three-dimensional (3D) printed customized prosthesis in acetabular reconstruction of hip revision surgery. METHODS: The related research literature on 3D printed customized prosthesis and its application in acetabular reconstruction of hip revision surgery was searched by key words of "3D printed customized prosthesis", "revision hip arthroplasty", "acetabular bone defect", and "acetabular reconstruction" between January 2013 and May 2024 in Chinese and English databases, such as CNKI, Wanfang database, PubMed, etc. A total of 34 271 articles were included. After reading the literature titles, abstracts, or full texts, the literature of unrelated, repetitive, low-quality, and low evidence level was screened out, and a total of 48 articles were finally included for analysis and summary. RESULTS: The bone growth and mechanical properties of 3D printed customized prosthesis materials are better than those of non-3D printed customized prosthesis, which further solves the problem of elastic modulus mismatch between the implant and natural bone caused by "stress shielding"; the porous structure and antibacterial coating on the surface of 3D printed customized prosthesis have good anti-bacterial effect. 3D printed customized prosthesis can perfectly match the patient's individual acetabular anatomical characteristics and defect type, thus improving the accuracy of acetabular reconstruction and reducing the surgical time and trauma. CONCLUSION 3D printed customized prosthesis can be used for precise and efficient individualized acetabular reconstruction in hip revision surgery with good early- and mid-term effectiveness. More optimized production technics and procedures need to be developed to improve the efficiency of clinical application and long-term effectiveness.
Printing, Three-Dimensional ; Humans ; Acetabulum/surgery* ; Prosthesis Design ; Hip Prosthesis ; Arthroplasty, Replacement, Hip/methods* ; Reoperation ; Plastic Surgery Procedures/methods*

OBJECTIVE: To compare the long-term follow-up effect and complications of ceramic on ceramic (CoC) interface and ceramic on polyethyleneon ceramic (CoP) interface in primary total hip arthroplasty, and provide clinical evidence. METHODS: Search PubMed, EMBase, the CoChrane Library databases, Web of science, Wanfang database, and CNKI from January 2000 to September 2021, screening and inclusion of randomized controlled trials (RCTs) comparing the long-term efficacy and complications of CoC interface and CoP interface in total hip arthroplasty. Literature screening, quality evaluation and data extraction were carried out according to the inclusion and exclusion criteria, using Review Manager 5.3 statistical software. The software was used to perform statistical analysis on joint function, revision, prosthesis fracture, abnormal joint noise, and prosthesis wear rate after CoC or CoP. RESULTS: Seven RCTs studies were included, including 390 cases of hips with CoC artificial joints and 384 cases of hips with CoP artificial joints. The long-term joint function improvement of CoC and CoP artificial joints was similar and there was no significant differences, with an average difference was MD=0.63, 95%CI=(-1.81, 3.07), P=0.61. About the postoperative complications, CoC artificial joints have higher incidence rate of abnormal joint noise, with odds ratio (OR)=11.05, 95%CI=(2.04, 59.84), P=0.005. CoP artificial joints wear faster, with an average MD=-87.11, 95%CI=(-114.40, -59.82), P<0.000 1. There was no significant difference between the two groups in the replacement-related complications such as joint dislocation, prosthesis loosening, osteolysis, and the rate of prosthesis revision caused by various reasons. CONCLUSION The clinical function results and complications of CoC artificial joints are comparable to those of CoP artificial joints. Although CoP artificial joint prosthesis has a faster wear rate, it does not affect joint function and increase complications, and there is no abnormal joint noise. CoC is expensive and the long-term efficacy is equivalent to CoP. Clinicians should consider cost performance when choosing CoC.
Humans ; Arthroplasty, Replacement, Hip/methods* ; Hip Prosthesis ; Follow-Up Studies ; Prosthesis Design ; Polyethylene ; Prosthesis Failure ; Reoperation ; Ceramics ; Treatment Outcome