Objective:To explore the optimal index of rotational displacement of femoral neck fractures by modeling the axial rotational displacement of femoral neck fractures after reduction and based on X-ray projections.Methods:Six dry human femur specimens, comprising 2 males and 4 females, were utilized in the study. Design and manufacture a proximal femur ortholateral and oblique X-ray casting jigs and mounts. The femoral neck fracture was modeled on the femoral specimen, with Pauwells 30°, 50°, and 70° models (2 each) made according to Pauwells typing. The fractures were manually repositioned with residual anterior 20°, 40° and 60° axial rotational displacements. Each fracture model was projected at different angles (pedicled 40°, pedicled 20°, vertical 0°, cephalad 20°, and cephalad 40°), and the trabecular angle and Garden's alignment index of the model were measured to observe the imaging characteristics of the fracture line on the medial oblique and lateral oblique radiographs.Results:In the presence of a 20° and 40° anterior rotational displacement following reduction of a femoral neck fracture, the trabecular angle in the rotationally displaced group was not significantly different from that of the anatomically repositioned group in various projection positions. However, when a residual rotational displacement of 60° was present, the trabeculae appeared blurred at most projection angles in the Pauwells 30° and 50° models, failing to measure trabecular angles. In the Pauwells 70° fracture model, the trabecular angle in the rotational displacement group was significantly different from that in the anatomical reduction group. In anteroposterior radiographs, when the anterior rotation displacement was 60° in the Pauwells 70° group, Garden's contralateral index showed an unsatisfactory restoration (150°, 142°), whereas all rotationally displaced models in the Pauwells 30° and Pauwells 50° groups had a Garden's contralateral index of >155°, which achieved an acceptable restoration. In lateral radiographs, all rotational displacement models with Garden's alignment index>180° failed to achieve acceptable repositioning, and the larger the Pauwells angle the greater the Garden's alignment index at the same rotational displacement. In the internal oblique position with a bias towards the foot side, the image showed partial overlap between the femoral head and the shaft, making it difficult to assess the quality of the reduction. Conversely, when projected cephalad, the femoral neck appeared longer, particularly at a projection angle of 40° cephalad, allowing for clear observation of the fracture line and the anatomy of the proximal femur. The trabeculae were not well visualized in the external oblique position.Conclusion:There are limitations in applying the trabecular angle to assess the axial rotational displacement of the femoral head after reduction of femoral neck fractures. The Pauwells 70° with residual rotational anterior displacement of 60° was the only way to detect axial rotational displacement of the femoral head on anteroposterior radiographs Garden's alignment index. For the determination of axial rotational displacement of the femoral head, the Garden's alignment index on lateral radiographs provides higher reliability.

Examining mechanisms involved in the mutual regulation between the muscular system and the skeletal system, elucidating the key issues responsible for loss of muscle and bone mass and strength, and thus halting the progression of these conditions are critical measures for reducing fractures caused by falls and subsequent disability and mortality.At present, most studies have treated the muscular system and the skeletal system separately, often ignoring the mutual regulation and connections between them.This article reviews the current research progress on the mechanisms of interaction between the two systems, aiming to provide a basis for the prevention, diagnosis and treatment of disuse-related diseases in the elderly population.

Shape memory materials are intelligent materials that have the effect of remembering and recovering their original shape in response to external stimuli. The preparation methods include heat treatment and laser sintering for alloy-based memory materials, and thermoplastic methods for polymer-based and composite shape memory materials. Shape memory materials have shown great application value in the field of orthopaedics, such as fracture treatment, bone tissue engineering repair, spinal correction and joint replacement. Shape memory materials have excellent biomechanical properties, providing sustained and effective compression, support and torsion resistance during fracture treatment, as well as the advantage of reducing stress masking in internal fixation of fractures. The sustained stress exerted on the surrounding bone tissue due to environmental changes provides continuous corrective force for spinal deformity correction, and improves the durability of prostheses in arthroplasty. Shape memory materials exhibit good biocompatibility and the performance of inducing cell proliferation, making them suitable for fabricating self-adapting" scaffolds for tissue engineering. When precisely filling bone defect sites, they apply mechanical forces to the autogenous bone, stimulate the proliferation and differentiation of osteoblasts, guide bone regeneration and accelerate bone repair. Moreover, shape memory materials can be used as carriers for drug delivery and release, controlling drug release by adjusting temperature, stress and environmental factors to achieve targeted therapy. With the development of 4D printing technology, shape memory materials have extensive potential in the fields of personalized orthopaedic diagnosis and treatment as well as individualized medical device customization.

Objective:To propose a method to measure the femoral anteversion angle based on the three-dimensional model of femur.Methods:From January 2019 to December 2023, a total of 50 patients (100 femurs) with patellar instability who underwent full-length CT examination of both lower limbs in Tianjin Hospital were retrospectively analyzed, including 16 males and 34 females, aged 28.5±11.9 years (range, 16-57 years). All patients underwent CT examination of both lower limbs, and the imaging data were imported into Mimics 21.0 software as DICOM format files. The femur was extracted by the threshold segmentation function, and the 3D model of the femur was reconstructed by appropriate trimming and smoothing. Three-dimensional models of the femur from 30 patients (60 femurs) were selected and imported into 3-matic 13.0 software for labeling of anatomical points and drawing of axes. The angle between the axis of the distal femur and the axis of the proximal femur was the femoral anteversion angle. Two observers positioned the spatial coordinates of the intercondylar fossa apex, the greater trochanter apex, the center of the femoral head, the femoral through-condylar axis and the posterior condylar tangent marker points on a 3D model of the femur to compare the differences between the groups. The femoral anteversion angles measured by different three-dimensional measurement methods were compared with the clinically reported femoral anteversion angles.Results:The difference between the femoral head center and intercondylar fossa apex coordinate data of 30 patients (60 femurs) measured by the two observers was not statistically significant ( P>0.05), whereas the data for the Y-axis coordinate of the greater trochanter apex were 25.77±23.21 and 22.08±25.73, respectively, and the difference was statistically significant ( t=2.906, P=0.017). The difference between the data of femoral through condylar and posterior condylar tangential coordinates of 30 patients (60 femurs) measured by the two observers was not statistically significant ( P>0.05). Using the femoral mechanical axis as the projection direction, the angle between the transcondylar axis and the posterior condylar tangent line was 5.97°±2.02° (range, 1.48°-12.08°). The anterior tilt of the femur measured by the two observers in the femoral neck cylinder fitting method was 23.35°±7.45° and 24.94°±9.01°, respectively, and the difference was statistically significant ( t=-2.147, P=0.040). The anterior inclination of the femur measured by the two observers in the femoral head ball enlargement method was 24.63°±7.66° and 25.12°±8.84°, the difference was not statistically significant ( t=-0.820, P=0.419). Using the femoral head ball expansion method to locate the proximal femoral axis, two observers measured the anterior tilt angle of the femur in 50 patients (100 femurs) according to the method described above, which was 23.30°±9.41° and 23.57°±9.97°, respectively, without a statistically significant difference ( t=-0.664, P=0.508), both smaller than the 29.56°±8.74° measured based on two-dimensional images in the imaging report, and the difference was statistically significant ( P<0.05). Conclusion:The femoral anteversion angle measured by the angle between the axis of the femoral condyle and the axis of the femoral neck based on the three-dimensional model is accurate and effective, and the measured value is smaller than that based on the two-dimensional images in clinical practice.

Objective:To establish a risk assessment system focusing on surgical and anesthesian-related indicators for the incidence of complications and mortality of hip fracture surgery in senile patients, and to evaluate its prediction accuracy, sensitivity and specificity.Methods:From January 2020 to February 2021, a total of 1 086 elderly patients (493 males and 593 females) aged 76±5 years (ranging from 60 to 94 years) underwent hip fracture surgery in Tianjin Hospital were collected. A total of 543 patients were randomly selected for the establishment of the hip fracture scoring system in senile patients, including 253 males and 290 females, aged 75±6 years (ranging from 60 to 92 years). With the preoperative physiological factor score and surgical risk factor score as independent variables and the occurrence of complications and death as dependent variables, binary logistic regression analysis was performed to establish a surgical risk scoring system for hip fracture in senile patients. The remaining 543 patients, including 240 males and 303 females, aged 74±7 years (range 60-94 years), their data were used to compare AUC, sensitivity, specificity, and compliance of the physiological and operative severity score for the enumeration of mortality and morbidity (POSSUM), Daping orthopedics operative risk scoring system for senile patient (DORSSSP), and our surgical risk scoring system for hip fracture in senile patients through receiver operating characteristic (ROC) curves, and to compare the predictive value of these systems for complication incidence and mortality.Results:The predictive model equation of the elderly hip fracture scoring system is: ln R1/ (1- R1) =-7.13+0.112× PS+0.148× OS; ln R2/ (1- R2) =-6.14+0.124× PS+0.136× OS; [ R1 is the incidence of complications, R2 is the mortality, PS (physiology score) is the score of preoperative physiological factors, and OS (operation score) is the score of surgical risk factors]. Among the 543 patients whose data were used to compared with the hip fracture scoring system, POSSUM and DORSSSP, 72 actually developed complications and 36 died. The complication rate predicted by surgical risk scoring system for hip fracture in senile patients was 12.05%±6.34% (range 6.18%-61.29%), and 64 cases were predicted to have complications. The predicted mortality was 6.05%±3.26% (range 2.45%-58.36%), and 29 cases were predicted to die. The complication rate predicted by POSSUM was 25.36%±13.95% (range 9.16%-76.34%), and 126 cases were predicted to have complications. The predicted mortality rate was 10.46%±5.31% (range 6.23%-59.34%), and 54 deaths were predicted. The predicted complication rate of DORSSSP was 19.34%±9.67% (range 8.36%-70.85%), and 99 cases were predicted to have complications. The predicted mortality was 10.12%±5.16% (range 7.35%-57.54%), and 52 deaths were predicted. In predicting the incidence of complications, the AUC of surgical risk scoring system for hip fracture in senile patients, POSSUM and DORSSSP were 0.95, 0.82 and 0.75, the sensitivity was 0.89, 0.83 and 0.85, the specificity was 0.80, 0.86 and 0.92, and the compliance rate was 0.94, 0.93 and 0.94, respectively. In the prediction of mortality, the AUC of surgical risk scoring system for hip fracture in senile patients, POSSUM and DORSSSP were 0.87, 0.67 and 0.71, the sensitivity was 0.85, 0.69 and 0.75, the specificity was 0.73, 0.94, 0.95, and the compliance rate was 0.94, 0.93 and 0.94, respectively. Conclusion:Compared with POSSUM and DORSSSP, hip fracture scoring system in elderly patients has improved its ability to predict surgical risk, and can accurately predict the incidence of complications and mortality in elderly patients undergoing hip surgery.

The sources of common knee valgus deformities were classified in order to better plan the orthopedic methods, matching prostheses and soft tissue repair of knee valgus deformities.Based on the analysis of typical clinical cases and the operability of classification standards in practical clinical practice, it is of great significance to establish a reasonable morphological classification of knee valgus deformity, in order to grasp the characteristics and patterns of the onset of valgus deformity. According to the origin of the deformity and the tension of the medial and lateral collateral ligaments, the classification of the genu valgus deformity can be divided into the classification of the traditional Genu valgum deformity origin and the classification of the new Genu valgum deformity origin. Although both of them highlight the skeletal characteristics and soft tissue conditions of the valgus deformity, they are quite different. Traditional classification is based on femoral tibial angle, valgus angle, etc; The new classification is divided into mechanical angle, anatomical angle, distal condylar angle, etc. The origin of Genu valgum deformity is generally complex. The traditional classification cannot fully reflect the origin of valgus deformity and the tension state of soft tissue. The new classification, especially based on the classification of anatomical angle valgus deformity, can not only reflect the morphological and anatomical details of knee valgus deformity, but also reflect the tension state of the medial and lateral collateral ligaments and local soft tissue stress state that determine the stability of the knee joint. At present, the commonly used surgical methods for valgus deformity of the knee include periarticular osteotomy of the knee and total knee Joint replacement. The former focuses on correcting extraarticular deformity without over repairing ligaments, and the latter focuses on force line correction, which is the final treatment for terminal valgus deformity. The application of digital technology in clinical orthopedics can improve the accuracy of implant placement. Implant placement needs to be based on the patient's bone characteristics and degree of deformity. For patients with severe deformity, the application of digital technology can improve the accuracy of implant placement and assist in the treatment of knee valgus deformity.

Objective To analyze the influence from material and size of the filling block on stress distributions of the tibial osteotomy model. Methods The filling blocks with three different materials (iliac bone, cancellous bone and polyetheretherketone (PEEK)) and five different sizes were established and implanted to the tibial osteotomy models, respectively. The mechanical loads were applied on the model, the stress distribution and edge displacement of the model were analyzed. Results For three kinds of materials, the stress at proximal end of the tibia and the plate, as well as edge displacement in the model implanted with filling block by iliac bone material were lower than those of the cancellous bone and PEEK, but the filling block by iliac bone material had the highest stress. When the filling blocks with different sizes were implanted in osteotomy space, the stress distribution on each part of the tibial osteotomy and edge displacement were different. Especially when the width of the filling block was reduced from 30 mm to 10 mm, the peak stress of the proximal tibia, steel plate and filling block was increased by 49. 3% , 92. 7% and 54. 4% on average. Conclusions Different filling block parameters will affect the stress distribution in different parts of the tibial osteotomy. The research results provide the theoretical basis for parameter selection of the tibial osteotomy filling block in clinic.

Objective To compare the differences in kinematic parameters and plantar pressures for two types of knee varus with tibial and femoral origins in gait analysis, so as to provide biomechanical theoretical basis for different types of genu varus. Methods Twenty-six patients with unilateral knee osteoarthritis (KOA) varus genu were enrolled, with 13 from femoral and 13 from tibial sources. Using Noraxon MyoMotion three-dimensional (3D) motion capture system and Footscan plantar pressure test system, the gait of the subjects during natural walking was measured, the temporal and spatial parameters of the gait, the kinematics parameters of lower limb joints and plantar pressures were collected, to make comparative analysis between the two groups. Results The range of knee flexion and extension of tibial varus, the peak of hip abduction, the range of motion (ROM) of hip adduction and abduction and the peak of ankle pronation were larger than those of femoral lateral genu varus. The peak of knee flexion and hip adduction was smaller than that of femoral lateral genu varus. Compared with femoral varus, subjects with tibial varus had increased stress time and peak pressure on the plantar of the 4th and 5th metatarsals (P<0.05). In the 3rd metatarsal region, the impulse of healthy femoral limb was greater than that of healthy limb with tibial deformity. While in the medial calcaneal region, the impulse of healthy femoral limb was smaller (P<0.05). Conclusions There are some differences in kinematic parameters and plantar pressures between two different types of unilateral genu varus patients. The results of this study are helpful to understand the abnormal gait caused by genu varus, and provide reliable reference for postoperative rehabilitation and limb exercise for different types of genu varus.

Objective To investigate biomechanical characteristics of femoral neck fracture with different reduction qualities. Methods Three cases of Sawbones artificial femoral models were selected, and two cases of Pauwel III femoral neck fracture were modeled. Three cannulated screws were inserted into the models in the form of inverted triangle to fix the fracture. Two cases maintained different reduction qualities (defined as Model 1 and Model 2). In the 3 third case, no modeling operation was performed (defined as intact model). Then the strain gauges were respectively pasted on regions of interest of the 3 femoral models. Finally, the femur model was applied with the vertical load on mechanical testing machine. Results When the displacement of femoral head reached 4 mm, the average load of intact model, Model 1 and Model 2 was (236.30±5.35), (196.57±3.56), (69.50±2.95) N, showing significant differences. When the displacement of femoral head reached 5 mm, the average load of intact model, Model 1 and Model 2 was (276.7±3.40)，(232.93±2.64)，(80.83±4.54) N, showing significant differences. Conclusions The lower the reduction quality of the femoral neck fracture, the weaker the ability of the femur to bear stress, the higher the probability of nonunion, re-fracture and femoral head necrosis in the process of postoperative rehabilitation.

A 3D printed patient-specific surgical guide plate is an auxiliary device made with the help of computer-aided design and 3D printing technology according to a surgical plan. It is used in reduction and internal fixation of fracture and specific corrective osteotomy as well. It is very adaptive as it has been widely used in trauma surgery, joint surgery and spine surgery, as well as in surgical treatment of bone tumors. Digital orthopedic technology is an important means to realize orthopedic precision medicine. This paper reviews the technical advantages, applications, main problems and future prospects of 3D printed patient-specific surgical guide plates in the field of orthopedics based on the recent literature.