Prosthesis Stem Research Articles

Bilateral total hip arthroplasty in a case with fibrous dysplasia: a case report

BackgroundFibrous dysplasia (FD) is a benign neoplasm with a broad spectrum of presentations. The treatment of FD in the hip region is controversial among orthopedic surgeons. Several treatment options exist, including curettage and grafting, valgus osteotomy, medial displacement osteotomy, and so on. Performing total hip arthroplasty (THA) on these patients and their subsequent outcome is still in infancy.Case presentationThe patient is a 32-year-old white female with bilateral proximal femur FD who underwent bilateral THA with long stem implants. A year following surgery, she had no complications and had satisfactory radiological, pain, and functional outcomes.ConclusionA bilateral THA with a long stem prosthesis showed promising results when performed following appropriate curettage of the proximal bone in an FD case. A cementless long stem could have enabled better diaphyseal fixation distal to the lesion site.

Retrospective clinical and X-ray-based outcome analysis of a short-stem hip arthroplasty taking into account the operative learning curve over 7 years in the 3-year control course

IntroductionSelf-monitoring is crucial to work progressively with a high-quality standard. A retrospective analysis is a valuable tool for studying the postoperative outcome of a prosthesis and for evaluating the learning process for the surgeon.Materials and methodsThe learning process of one surgeon was analysed in 133 cases of hip arthroplasty. These were divided into seven groups representing the surgical years 2008–2014. Over the course of 3 postoperative years, a total of 655 radiographs were analysed at regarding three radiological quality parameters (centrum-collum-diaphyseal angle (CCD angle), intramedullary fit&fill ratio (FFR), and migration) and ancillary outcome parameters (Harris Hip Score (HHS), blood loss, operating time, and complications). This period was divided into five times: 1st-day post-op, 6 M, 12 M, 24 M, and 36 M. Bivariate Spearman's correlation analysis and pairwise comparisons were performed.ResultsThe total collective achieved a proximal FFR of over 0.8. The distal prosthesis tip migrated and was located on the lateral cortex within the first months. The CCD angle initially showed a variation with a subsequent constant course. The HHS showed a significant increase (p < 0.001) to over 90 points postoperatively. Over time, the operating time and blood loss decreased. Intraoperative complications existed only at the beginning of the learning phase. A learning curve effect can be determined for almost all parameters by comparing the subject groups.ConclusionsOperative expertise was shown to gain through a learning curve, whereby postoperative results corresponded to the system philosophy of the short hip stem prosthesis. The distal FFR and the distal lateral distance could represent the principle of the prosthesis, which overall could be an interesting approach for verification of a new parameter.

Mid-Term Follow-Up Results After Hemiarthroplasty Using Long Femoral Stem Prosthesis (Peerless-160) for Intertrochanteric Fractures in Octogenarians.

To analyze the clinical effect and imaging data of cementless bipolar hemiarthroplasty employing a long femoral stem (peerless-160) and 2 reconstructed femoral titanium wires to repair intertrochanteric fractures among the octogenarians. Between June 2014 and August 2016, 58 octogenarians with femoral intertrochanteric fractures underwent the long femoral stem (peerless-160) cementless bipolar hemiarthroplasty by the same surgeon. We assessed clinical and radiological outcomes such as operative time, bleeding volume, blood transfusion volume, length of hospital stay, full weight-bearing walking time, walking ability calculated by Koval classification and Harris Hip Score (HHS), including fracture healing and greater trochanter fragments subsidence. The surgery was successfully performed in all patients. The average operation time was 72.8 ± 13.2min, the average blood loss during surgery was 225.0 ± 91.4mL, 200mL of blood was transfused, the mean duration of hospitalization was 11.9 ± 4.0days, the mean time of full weight bearing was 12.5 ± 3.8days. Patients were followed up for 24-68months, averagely 49.4 ± 10.3months. During follow-up, 4 (6.9%) patients died, and 1 (1.7%) was completely lost to ask about the recent situation. The average Harris Hip Score at the last follow-up was 87.8 ± 6.1, most of the patients recovered walking ability, under radiological examination, the prosthesis showed no signs of loosening. All trochanteric fractures gradually healed, the clinical and radiographic signs of healing occurred at average of 4.0 ± 1.1months postoperatively. For osteoporotic unstable intertrochanteric fractures in octogenarians, this study confirmed that the Cementless Bipolar Hemiarthroplasty Using a Long Femoral stem (peerless-160) with double cross binding technique is a satisfactory and safe choice for the octogenarians.

Dosimetric effects of different hip prosthesis materials during pelvic radiotherapy using high energy photons

This study investigates the effects of different hip prosthesis materials on the secondary neutron and electron contamination produced by high energy, i.e. 18 MV, photon beams during pelvic irradiation. Three different materials, including Titanium-alloy (Ti-alloy), Stainless Steel (SST), and Cobalt–Chromium–Molybdenum-alloy (Co–Cr–Mo), were evaluated in a Monte Carlo (MC) study. The Varian 2100 C/D linac head and an ICRP reference adult male voxel phantom with a realistic hip prosthesis were simulated using the MCNPX (ver. 2.6) MC code. As expected, results showed that secondary electron and neutron generation mainly depends on the shape and material type of the prosthesis. The mean dose increase factor (DIF) for electron contamination is 1.72, 1.53, and 1.35 for Co–Cr–Mo, SST, and Ti-alloy, respectively, at the tissue-prosthesis interface. Electron contamination also depends on the prosthesis thickness and it is increased by increasing the thickness. The maximum DIF for neutrons occurs at the center of the prosthesis stem and its mean DIF is 2.91, 2.49, and 2.34 underneath Co–Cr–Mo, SST, and Ti-alloy prostheses, respectively. The amount of neutron DIF is slightly reduced above prostheses. Furthermore, the results indicate that the most significant change in the electron dose distribution is observed at the tissue-prosthesis interface. The neutron dose equivalent is increased from 76% to 200% in the presence of the different materials of the prosthesis. Hip prostheses made of Ti-alloy can significantly decrease the dose due to neutron and electron contamination, compared to the other materials considered in the simulations.

Osteogenic properties of nanohydroxyapatite/polyamide 66-Coated femoral stem prosthesis and its efficacy in total hip replacement combined with staged functional rehabilitation exercises

To evaluate the efficacy of nanohydroxyapatite/polyamide 66 (nHA/Pa66)-coated femoral stem prosthesis in total hip arthroplasty (THA) and the advantages of combined post-operative staged rehabilitation functional exercises (SRFE) in restoring hip function, 112 patients with femoral neck fractures were enrolled in the clinical study. Patients were randomized to routine and nHA/Pa66 groups. Patients in the nHA/Pa66 group were treated with nHA/Pa66-coated femoral stem prosthesis and the post-operative SRFE program. We evaluated the physical properties, cytotoxicity, and osteogenic capacity of nHA/Pa66 in an in vitro trial, and the clinical treatment, postoperative improvement in joint function (Barthel score, VAS score, Harris score), imaging performance, and incidence of adverse events were compared between groups. The porosity of nHA/Pa66 was ∼75% and its pore size was in the range of 300–500 μm. Moreover, nHA/Pa66 had good biocompatibility and could improve bone marrow stem cells (BMSCs) activity and enhance the osteogenic function of BMSCs, effectively increasing the levels of COL I, ALP, and OCN. A combination of nHA/Pa66 and SRFE could effectively shorten hospital stay, better restore hip function, and reduce the incidence of complications. Therefore, nHA/Pa66-coated femoral stem prosthesis combined with SRFE showed great potential in THA for femoral neck fractures.

The effect of shoulder prosthesis stem length on failure due to torsional loading. A biomechanical study in composite humeri

Shoulder arthroplasty is becoming increasingly common. With evolving implant designs, multiple humeral stem options exist for the surgeon to choose from. New stemless and short-stem systems are modular, remove less native bone stock, and better adapt to patient anatomy. It has been suggested that shorter stem implants may be protective against periprosthetic fracture; however, this has not been mechanistically evaluated. Therefore, this study aimed to biomechanically test synthetic humeri with long-stem, short-stem, and stemless arthroplasty components in a torsional manner to evaluate their response to loading and characterize failure. Twenty-four synthetic humeri were implanted with long stem, short stem, or stemless uncemented prosthesis, 8 in each group. Humeri were mounted in a custom testing jig with a morse taper interfacing with a mechanical testing system. After a 20N axial force, specimens were torsionally loaded to failure at 15 degrees/sec, with 50 Hz collection. Torque vs. rotation curves were generated for each specimen, and stiffness, yield, ultimate strength, and failure load were measured. ANOVA and post hoc pairwise comparisons were used to assess effect of stem type on mechanical test variable. The association of the stem type with fracture type was analyzed by a Fisher's Exact test. Statistical significance was set at P<.05. During torsional loading, long-stem implants were significantly stiffer than short or stemless implants. The angle of implant yielding was similar across stem designs; however, stemless implants had a lower yield torque. This correlated with a decreased yield energy in stemless compared to short stems as well. Maximum torque and failure torque was also significantly higher in short-stem and long-stem implants compared to stemless. Periprosthetic fractures in shoulder arthroplasty are a concern in low-energy trauma, and stem design likely plays a significant role in early implant-bone failure. Our results suggest stemless implants under torsional load fail at lower stress and are less stiff than stemmed implants. The failure mechanism of stemless implants through metaphyseal cancellous bone emphasizes the effect bone quality has on implant fixation. There is likely a balance of torsional stability to survive physiologic loads while minimizing diaphyseal stress and risk of diaphyseal periprosthetic fracture. This combined with revision and fixation options represent decisions the surgeon is faced with when performing shoulder arthroplasty.

DESIGN AND STRUCTRAL ANALYSIS OF HIP-JOINT IMPLANT

An artificial joint (prosthesis) helps reduce pain and improve function. Also called total hip arthroplasty, hip replacement surgery might be an option if hip pain interferes with daily activities and nonsurgical treatments haven't helped or are no longer effective. We review the different materials, constructions, and surfaces used in the development of femoral stems, in order to solve and avoid various problems associated with their use. Femoral stem prostheses have undergone substantial changes and design optimizations since their introduction In this project a new design of hip joint implant is introduced by using Ti6Al4V(alpha-beta Ti alloy), Cobalt Chromium(Co Cr) alloy, 316L stainless steel alloy materials. All the parts are designed in CATIA V5.18 and static structural analysis was done in ANSYS WORKBENCH. The equivalent (Von Mises) stresses are analyzed and deformation of the Hip joint for all the three materials are compared. Also, Ti6AL4V has better properties that are similar to bone compared to the rest of the bio materials that are considered during the project work. KEYWORDS: Implant, Femoral stem, Femoral head, Plastic liner, Acetabular component, Support plate, Structural analysis.

Development of an algorithm-based approach for Computational Design Synthesis of individualized implants

The trend towards product individualization in medical technology, e.g., for implants, is based on the realization that taking patient-specific characteristics into account significantly influences the therapy of diseases. However, one problem in the individualization of implants is the inaccessible position in the body, which only permits computer-aided modeling of individual solutions. A promising solution is using a Computer-Aided Engineering Environment (CAEE), which enables an algorithm-based approach to implement tools based on Computational Design Synthesis (CDS) that can build design knowledge and robustly generate patient-specific variants. In this paper, a case study is used to demonstrate the development of an algorithm-based approach within the framework of the CDS in a CAEE that performs hip arthroplasty individualization. The functions, implemented in a CAEE, includes all process steps, from medical image processing of Computed Tomographic (CT) data to generating a patient-specific solution. Relevant research questions addressed here include the automated recognition of geometry information from initialized data, processing of these data in product models to derive solutions automatically and implementing optimization algorithms to maximize requirement satisfaction. The result of this work is a fully automated model generator for hip stem prosthesis that requires only a CT scan for its design synthesis and optimization.

Retracted: Effect of nHA‐Coated Femoral Stem Prosthesis Combined with Platelet‐Rich Plasma in Hemi Hip Replacement of Femoral Neck Fracture in the Elderly

Retracted: Effect of nHA‐Coated Femoral Stem Prosthesis Combined with Platelet‐Rich Plasma in Hemi Hip Replacement of Femoral Neck Fracture in the Elderly

Structural composite based on 3D printing polylactic acid/carbon fiber laminates (PLA/CFRC) as an alternative material for femoral stem prosthesis

In recent years, surgical procedures for hip prostheses have increased. These implants are manufactured with materials with high stiffness compared to the bone, causing bone loss or aseptic loosening. This research proposes an alternative structural composite consisting of 3D-printing polylactic acid layers and carbon fiber laminates (PLA/CFRC) with potential application in prosthetic implants. Fourier-transform infrared spectroscopy (FTIR) achieved to characterize starting materials and structural composites revealed secondary chemical interactions between the carbonyl group of PLA with the hydroxyl group of epoxy resin from CFRC. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) results show both components (PLA and CFRC) influence the structural composite's thermal behavior, observed in the temperatures of degradation, glass transition, and melting. Furthermore, the composite reached cell viability above 80%, a tensile modulus of 19.29 ± 0.48 GPa and tensile strength of 238.91 ± 25.95 MPa, with mechanical properties very similar to the bone. The results of this study demonstrated that the proposed PLA/CFRC composite can be used as candidate base material for the manufacturing of a hip femoral stem prostheses.

The short-term outcomes of cementless stem for hip arthroplasty in the elderly patients: comparison with patients < 65 years

ObjectiveThe use of cement or cementless femoral stem prosthesis for hip arthroplasty in elderly patients has been controversial. This study investigated the efficacy and safety of cementless femoral stem in elderly patients (age ≥ 65 years).MethodsThe short-term efficacy of primary hip arthroplasty with cementless femoral stem in our hospital from January 2014 to June 2021 was retrospectively analyzed. Patients were divided into two groups according to age: young group (< 65 years) and the elder group (≥ 65 years). The evaluation index was the Harris Hip score (Harris), postoperative femoral stem prosthesis sinking distance and femoral plant-related complications (periprosthetic fracture, prosthesis loosening, infection, dislocation, etc.).ResultsThere were 72 cases of 86 hips in the young group and 83 cases of 92 hips in the elder group. The recovery trend of functional score in the elder group was similar to that in the young group, and the Harris score increased from (38.35 ± 18.21) before surgery to (86.91 ± 12.55) at last follow-up (p < 0.01). Compared with the two groups at the same time of 3 months, 6 months and 12 months after operation, the sinking distance of the elder group was significantly greater (P < 0.05). Even in the elder group, there was a significant difference in sinking distance between 6 and 3 months after surgery (2.44 ± 0.49 mm vs 2.10 ± 0.65 mm, P = 0.004). However, there was no significant difference between 12 and 6 months (2.53 ± 0.53 mm vs 2.44 ± 0.49 mm, P = 0.40). A total of 10 patients in the elder group and 6 patients in the young group had a complication event (P = 0.36).ConclusionsElderly patients with cementless femoral stems can achieve metal-bone integration slightly longer than young patients, but short-term clinical outcomes can be restored to a satisfactory level with adequate safety. However, the long-term efficacy still needs to be verified by multicenter, large sample size and prospective clinical follow-up results.

Novel axial compressive endoprosthesis ACE can enhance metaphyseal fixation and facilitate osseointegration: A biomechanical study.

Background: Metaphyseal fixation for endoprosthetic reconstruction after bone tumor resection is difficult due to the short residual bone length and reverse funnel shape of the metaphysis. In the current study, 3D-printed axial compressive endoprosthesis (ACE) with a short stem and intramedullary axial compressive mechanism is proposed to improve metaphyseal fixation. The rationales of ACE are that 1) intramedullary axial compress enhances the stability of endoprosthesis and facilitates bone ingrowth at the osteotomy site; 2) 3D printed porous metallic surface at osteotomy surface and stem allows bone ingrowth to achieve osseointegration. Methods: A biomechanical study was performed to explore the initial stability using Sawbones. A diaphysis and metaphyseal segmental defect were created and four fixation structures were simulated: 1) ACE; 2) ACE + lateral plate; 3) stem prosthesis + unilateral plate; 4) stem prosthesis + bilateral plates. Bending and torsional stiffness were determined with a material testing machine. The relationship between the torque of the compression nut and the axial compression force of the bone-implant surface was measured using a round gasket load sensor. Results: ACE + lateral plate was the stiffest in the bending test (sagittal 324.3 ± 110.8N/mm, coronal 307.7 ± 8.7N/mm). ACE + lateral plate and stem prosthesis + bilateral plates had the highest torsional stiffness (10.9 ± 1.3Nm/° and 10.7 ± 0.2Nm/° respectively). The bending stiffness of ACE was equivalent to stem prosthesis + bilateral plates (sagittal 196 ± 10N/mm vs. 200 ± 7N/mm, coronal 197 ± 14N/mm vs. 209 ± 3N/mm), but the torsional stiffness of ACE was inferior to stem prosthesis + bilateral plates (6.1 ± 1.3Nm/° vs. 10.7 ± 0.2Nm/°). Stem prosthesis + unilateral plate was the least stiff both in bending and torsion. The relationship between torque (T/Nm) and axial pressure (F/N) was F = 233.5T. Conclusion: The axial compressive design of ACE enhances primary stability and facilitates osseointegration, which provides an alternative option of metaphyseal fixation for endoprosthetic reconstruction.

Clinical effect of Corail femoral prosthesis with different offset in total hip arthroplasty

To explore the early clinical efficacy of primary total hip arthroplasty(THA) with Corail standard stems (KS type) and high offset stems (KHO type), by analyzing the postoperative radiographic parameters of different offset of femoral components with Corail stem which has a neck-shaft angle of 135 ° in unilateral primary THA, by comparing the measurement results on both sides and analyzing the reconstruction of the postoperative femoral offset and the hip joint function recovery. A retrospective analysis was made of 186 patients with unilateral hip joint lesions who underwent the first total hip arthroplasty with Johnson & Johnson Corail prostheses from January 2015 to June 2017. According to the use of femoral prostheses with different eccentricities during the operation, the patients were divided into high eccentricity group and standard eccentricity group. In the high eccentricity group, there were 52 cases of Corail high eccentricity prosthesis(KHO type), including 20 females and 32 males;aged 21 to 71 years old with an average of(50.6±13.2) years;body mass index(BMI) was (26.0±4.1) kg/m2. The standard eccentricity group included 134 Corail standard femoral stem prostheses(KS type), 57 females and 77 males;aged 18 to 77 years old with an average of (47.3±14.0) years;BMI was (25.3±3.5) kg/m2. The abduction arm, femoral eccentricity, acetabular eccentricity and the length difference of lower limbs were measured on the postoperatively positive X-ray film of the hip joint. Harris score and related complications were recorded before and after the operation, and the stability of the prosthesis was analyzed. There were significant differences in femoral eccentricity, joint eccentricity and abduction arm between the affected side and the healthy side in the high eccentricity group(P<0.05). There were significant differences in femoral eccentricity and acetabular eccentricity between the affected side and the healthy side in the standard eccentricity group(P<0.05). There were significant differences in combined eccentricity, abduction arm and length of lower limbs between two groups(P<0.05). In the high eccentricity group, the abduction arm of the affected hip joint was positively correlated with the femoral eccentricity, acetabular eccentricity and joint eccentricity(r=0.633, P<0.001;r=0.384, P=0.005;r=0.690, P<0.001). The same results were also obtained in the healthy side(r=0.688, P<0.001;r=0.574, P<0.001;r=0.765, P<0.001). In the standard eccentricity group, the abduction arm of the affected hip joint was positively correlated with the femoral eccentricity, acetabular eccentricity and combined eccentricity(r=0.734, P<0.001;r=0.418, P<0.001;r=0.749, P<0.001). The same results were also obtained in the healthy side(r=0.775, P<0.001;r=0.397, P<0.001;r=0.773, P<0.001). The difference of the length of both lower limbs was significantly correlated with the difference of bilateral joint eccentricity and bilateral abduction arm (r=0.376, P=0.006;r=-0.346, P=0.012). There was no significant correlation between the difference of the length of both lower limbs and the difference of bilateral joint eccentricity and bilateral abduction arm (r=-0.009, P=0.919;r=-0.036, P=0.682). There was no significant difference in Harris score between two groups at the last follow-up(P>0.05). At the last follow-up, Trendelenburg was negative in all patients in both groups, and the prostheses were stable. Both Corail standard stem and high offset stem may be effectively reconstruct the femoral offset, reconstruct the anatomical structure and biomechanics of the hip joint, and maintain the length of lower limbs and the stability of the hip joint in the unilateral primary total hip arthroplasty. Although the offset of the femur was not reconstructed normally in some cases, the stability of the components and postoperative function were not affected.

A novel method of manual positioning based on anatomical mark (shoulder-to-shoulder) to prevent postoperative leg-length discrepancy for femoral neck fractures in hip arthroplasty.

To determine whether the two lower extremities are of equal length after hip arthroplasty for femoral neck fractures, we developed a novel method of manual positioning based on anatomical mark (shoulder-to-shoulder) in hip arthroplasty. Patients with femoral neck fractures requiring hip arthroplasty from July 2020 to March 2022 in the orthopedic department of Jinjiang Municipal Hospital, Fujian Province, China were recruited. Hip arthroplasty was performed using the proposed "shoulder-to-shoulder" method of manual positioning based on anatomical mark in 52 patients with femoral neck fractures who met the inclusion criteria. "Shoulder-to-shoulder" was achieved by alignment of the marked femoral "shoulder" and the "shoulder" of prosthesis stem. There were 16 male and 36 female patients, with 27 undergoing total hip arthroplasty (THA) and 25 undergoing hip hemiarthroplasty (HA). The fractures were categorized according to the Garden classification: type II, type III, and type IV in 5, 11, and 36 patients, respectively. The vertical distance from the apex of the medial margin of the femoral trochanter to the tear drop line on both sides which was regarded as the length of both limbs were compared via postoperative imaging, and the apex-shoulder distance on the ipsilateral side measured via postoperative imaging was compared with those measured intraoperatively. All patients completed the surgery successfully. The measurement results for the lower extremities after THA were as follows: contralateral group, 43.87 ± 5.59 mm; ipsilateral group, 44.64 ± 5.43 mm. The measurement results for the lower extremities after HA were as follows: contralateral group, 45.18 ± 7.82 mm; ipsilateral group, 45.16 ± 6.43 mm. The measurement results for the lower extremities after all arthroplasties were as follows: contralateral group, 44.50 ± 6.72 mm; ipsilateral group, 44.89 ± 5.90 mm. The results for the apex-shoulder distance were as follows: postoperative imaging, 19.44 ± 3.54 mm; intraoperative apex-shoulder distance, 27.28 ± 2.84 mm. Statistical analysis results indicated no statistically significant difference in the postoperative bilateral lower extremity length after hip arthroplasty (P = 0.75), while a statistically significant difference was found between the intraoperative and postoperative imaging measurements of the apex-shoulder distance (P < 0.01). The novel method of manual positioning based on anatomical mark (shoulder-to-shoulder) for femoral neck fractures in hip arthroplasty is simple and accurate, making it effective for preventing postoperative bilateral leg length discrepancy.

3D-printed hemipelvic prosthesis combined with a dual mobility bearing in patients with primary malignant neoplasm involving the acetabulum: clinical outcomes and finite element analysis

BackgroundLimb salvage reconstruction for pelvic tumors, especially periacetabular tumors, is challenging. We combined the use of dual mobility bearing and 3D-printed hemipelvic prosthesis to improve function and reduce the probability of complications after hemi-pelvic resection in patients with primary acetabular malignancy. The purpose of this study was to evaluate the efficacy and safety of this combination.MethodsBetween October 2011 and May 2021, 11 patients with malignancies involving the acetabulum received hemipelvic replacement with a 3D-printed prosthesis and dual mobility bearing. Follow‐up of postoperative survival, complications, and Musculoskeletal Tumor Society 93 (MSTS-93) lower limb functional scores were carried out. A finite element model of the postoperative pelvis was developed and input into the finite element analysis software. The Von Mises equivalent stress formula was used to analyze the stress distribution of each part of the pelvis under one gait cycle and the stress distribution at different angles of the hip joint.ResultsBy the last follow-up, 9 of the 11 patients (81.8%) were still alive, and 2 patients had local tumor recurrence. The complications including 1 deep infection and 1 dislocation of the artificial joint. Excluding 1 amputation patient, the average score of the remaining 8 patients at the last follow-up was 21.4/30 (71.3%) on the MSTS-93. In the reconstructed pelvis, stress distributions were concentrated on the junction between hemipelvic prosthesis and screw and iliac bone on the resected side, and between femoral prosthesis stem and femoral bulb, while the stress of polyethylene lining was small. Before impact, the polyethylene lining will rotate at a small angle, about 3°. The inner stress of polyethylene liner is greater than the outer stress in all conditions. The polyethylene liner has no tendency to slide out.ConclusionPelvic tumor resection and reconstruction using 3D-printed hemipelvic prosthesis combined with dual mobility bearing was an effective treatment for pelvic tumors. Our patients achieved good early postoperative efficacy and functional recovery. The dual mobility bearing is beneficial to prevent dislocation, and the mechanical distribution and wear of the prosthesis are acceptable.

Impending atypical femoral fractures associated with bisphosphonates: postoperative diagnosis after hip prosthesis. Clinical cases presentation.

Number of hip prosthesis implants in arthritis, number of patients treated with bisphosphonates to prevent fragility fractures and, together, number of atypical femoral fracture's cases are increasing. This article describes two cases of hip arthritis, treated with hip replacement, in patients using bisphosphonates for a long time; in both cases an incomplete atypical femoral fracture was misdiagnosed before the surgery. Authors describe the importance to carry out a complete osteometabolic and radiographic pre-operative examination of patients in treatment with bisphosphonates going to hip replacement, to check the possible presence of incomplete atypical femoral fracture and to optimize surgical and pharmacological treatment. In hip prosthesis surgery, prior diagnosis of incomplete atypical femoral fractures can indicate the choice of a different kind of prosthesis stem to optimize surgical results. This can also positively impact to rehabilitation in term of duration and daily activities recovery.

Short hip stem for THA in avascular necrosis of the femoral head

Osteonecrosis of the femoral head or avascular necrosis of the femoral head (HKN) is acomplex disease that, without treatment, leads to infraction of the femoral head in most cases. In these cases, only replacement of the hip joint will help, although there is no clear recommendation of an arthroplasty type. In the last two decades, the treatment of primary and secondary coxarthrosis with short-shaft prostheses with different anchoring philosophies has increased. Since short-shaft fitting is apossible option especially in younger patients, the question arises about possible fittings of advanced HKN with these stem types, especially with metaphyseal anchorage. The aim of this study was to review the existing literature on the results of short stem prosthesis in HKN and to present the advantages and disadvantages of short stem prosthesis in osteonecrosis of the femoral head. This review analyzes the existing studies on short stem arthroplasty for HKN. Only a few studies exist that have analyzed clinical and radiologic outcomes of short stem replacement in HKN. The existing short- and medium-term results show mostly good outcomes. However, it is difficult to draw ageneral conclusion due to differences in stem design and fixation. Short stems with primary diaphyseal fixation do not show an increased risk of failed osseointegration or loosening. Constructions with primary metaphyseal fixation should undergo MRI to rule out the possibility of necrosis extending beyond the femoral neck.

Monitoring Osseointegration Process Using Vibration Analysis.

Osseointegration implant has attracted significant attention as an alternative treatment for transfemoral amputees. It has been shown to improve patients’ sitting and walking comfort and control of the artificial limb, compared to the conventional socket device. However, the patients treated with osseointegration implants require a long rehabilitation period to establish sufficient femur–implant connection, allowing the full body weight on the prosthesis stem. Hence, a robust assessment method on the osseointegration process is essential to shorten the rehabilitation period and identify the degree of osseointegration prior to the connection of an artificial limb. This paper investigates the capability of a vibration-related index (E-index) on detecting the degree of simulated osseointegration process with three lengths of the residual femur (152, 190 and 228 mm). The adhesive epoxy with a setting time of 5 min was applied at the femur–implant interface to represent the stiffness change during the osseointegration process. The cross-spectrum and colormap of the normalised magnitude demonstrated significant changes during the cure time, showing that application of these plots could improve the accuracy of the currently available diagnostic techniques. Furthermore, the E-index exhibited a clear trend with a noticeable average increase of 53% against the cure time for all three residual length conditions. These findings highlight that the E-index can be employed as a quantitative justification to assess the degree of osseointegration process without selecting and tracing the resonant frequency based on the geometry of the residual femur.

Finite element analysis of optimal design of distal geometry of cementless femoral prosthesis.

This study aims to improve the geometric design of the distal cementless femoral prosthesis stem, thereby changing the stress distribution of the femoral prosthesis and reducing the proximal stress shielding and distal stress concentration of the femur, so as to obtain better bone growth and long-term stability. Two geometric shapes of the femoral stems, namely, inverted hollow cone and cross-shaped bottom groove, are designed for the distal femoral prosthesis. The model is built based on the femoral computed tomography (CT) data of healthy volunteers, and the finite element method is used to analyze and calculate the stress distribution of the two femoral prosthesis stems. According to the length and width of bottom "cross" groove, the stress values of the femoral region of the cross-grooved distal femur are divided into five groups, namely, group 1 (length 1:1, groove width 1.0 mm); group 2 (length 1:1, groove width 1.5 mm); group 3 (length 1:1, groove width 2.0 mm); group 4 (length 1:2, groove width 1.0 mm); group 5 (length 1:2, groove 1.5 mm wide). And the non-grooved group of the distal femur is designated as group 0. In the segment A, B, and C of the femoral region, the difference in the mean stress between group 0 and groups 1, 2, and 3 have statistical significance. The bottom "cross" groove of the distal femoral prosthesis can change the stress distribution in the prosthesis-distal femoral region and reduce the stress concentration at the distal prosthesis. Wherein, the grooved design of length ratio 1:1 is more advantageous.

Convenient design method for customized implants based on bionic vein structure features.

Matching implants to bones is crucial for customized orthopedic medicine. Existing methods for designing customized implants predominantly adopt the parameterized deformation method that uses a fragmented representation of semantic parameters. Such a representation cannot provide information integration management and therefore restricts the retrieval of information regarding implant features and the improvement of customized design efficiency. Therefore, this study proposes a rapid design method for customized implants based on bionic vein structure features. First, a bionic vein structure was designed to represent the implant type. Second, the bionic vein structure was represented by a digraph structure with morphological and dimensional features. Finally, the implant model was rapidly built by retrieving the sketch and other modeling operations. Common implants such as the T-shaped plate, L-shaped plate, clover plate, and femoral stem prosthesis were used as explanations or test cases. The experimental work shows that combining the traditional parametric deformation method with bionic vein structure features in our present method is flexible and efficient results, and can improve the efficiency of customized implant design.