Metaphyseal anchoring short stem hip arthroplasty provides a more physiological load transfer: a comparative finite element analysis study

Primary stability of multi-hole acetabular cup combined with posterior column plating for the fixation of complex acetabular fractures in elderly patients: a biomechanical analysis

BACKGROUND

Acute total hip arthroplasty has gained increasing popularity in the treatment of complex acetabular fractures in elderly patients, but the biomechanical evidence is lacking. Therefore, we measured the primary stability to evaluate whether acute total hip arthroplasty using a multi-hole acetabular cup and posterior column plating through a single K-L approach can safely be used for treating complexed acetabular fractures in the elderly.

METHODS

In 18 composite osteoporotic hemipelves, T-type acetabular fractures were treated in three ways: CSP (Cup with acetabular screws augmentation combined with posterior plate) group, CP (Cup without acetabular screw combined with posterior plate) group and CSPA (Cup with acetabular screws combined with posterior plate and anterior plate) group. Each specimen was dynamically loaded (300 to 1700 N, 1 Hz). Primary stability of the acetabular cup and fracture gap was evaluated by 3-dimensional (3D) micromotions.

RESULTS

No significant differences in the 3D-micromotions were observed among the CSP, CP and CSPA groups except the test point on the anterior column of the acetabulum in the CP scenario (CSP 49.33 ± 21.08 μm vs. CP 224.83 ± 52.29 μm, p < 0.001; CSPA 45.50 ± 12.16 μm vs. CP 224.83 ± 52.29 μm, p < 0.001). No significant differences in the fracture gap displacement on the posterior column of acetabulum were observed among the CSP, CP and CSPA groups.

CONCLUSION

Our results show, that acute total hip arthroplasty using a multi-hole cup with acetabular screws and posterior column plating through single a K-L approach offers good primary stability to allow good osseous integration for treating complex acetabular fractures in the elderly. Furthermore, it also provides good fracture gap displacement on the posterior column.

The Function and Mechanism of Anti-Inflammatory Factor Metrnl Prevents the Progression of Inflammatory-Mediated Pathological Bone Osteolytic Diseases

Metrnl, recently identified as an adipokine, is a secreted protein notably expressed in white adipose tissue, barrier tissues, and activated macrophages. This adipokine plays a pivotal role in counteracting obesity-induced insulin resistance. It enhances adipose tissue functionality by promoting adipocyte differentiation, activating metabolic pathways, and exerting anti-inflammatory effects. Extensive research has identified Metrnl as a key player in modulating inflammatory responses and as an integral regulator of muscle regeneration. These findings position Metrnl as a promising biomarker and potential therapeutic target in treating inflammation-associated pathologies. Despite this, the specific anti-inflammatory mechanisms of Metrnl in immune-mediated osteolysis and arthritis remain elusive, warranting further investigation. In this review, we will briefly elaborate on the role of Metrnl in anti-inflammation function in inflammation-related osteolysis, arthritis, and pathological bone resorption, which could facilitate Metrnl's clinical application as a novel therapeutic strategy to prevent bone loss. While the pathogenesis of elbow stiffness remains elusive, current literature suggests that Metrnl likely exerts a pivotal role in its development.

Effect of short stem alignment on initial fixation, stress transfer, and failure risk

BACKGROUND

Short stems are advantageous for revision as they preserve autogenous bone. At present, the method of short-stem installation is determined based on the surgeon's experience.

OBJECTIVE

To provide the guideline for installing a short stem, we aimed to investigate the alignment effect on the initial fixation of the stem, stress transfer, and the risk of failure numerically.

METHODS

Models in which the caput-collum-diaphyseal (CCD) angle and flexion angle were hypothetically changed based on the two clinical cases of hip osteoarthritis were analyzed using the non-linear finite element method.

RESULTS

The medial settlement of the stem increased in the varus model and decreased in the valgus model. With varus alignment, the stresses acting on the femur were high in the distal to the femoral neck. In contrast, the stresses in the proximal to the femoral neck tend to be higher with valgus alignment, although the difference in the femur stress between varus and valgus alignment was slight.

CONCLUSION

Both initial fixation and stress transmission are lower when the device was placed in the valgus model than in the actual surgical case. In order to obtain initial fixation and suppress stress shielding, it is essential to extend the contact area between the medial portion of the stem and the femur along the bone axis, and to ensure adequate contact between the lateral portion of the stem tip and the femur.

Stress-shielding resistant design of custom pelvic prostheses using lattice-based topology optimization

Endoprosthetic reconstruction of the pelvic bone using 3D-printed, custom-made implants has delivered early load-bearing ability and good functional outcomes in the short term to individuals with pelvic sarcoma. However, excessive stress-shielding and subsequent resorption of peri‑prosthetic bone can imperil the long-term stability of such implants. To evaluate the stress-shielding performance of pelvic prostheses, we developed a sequential modeling scheme using subject-specific finite element models of the pelvic bone-implant complex and personalized neuromusculoskeletal models for pre- and post-surgery walking. A new topology optimization approach is introduced for the stress-shielding resistant (SSR) design of custom pelvic prostheses, which uses 3D-printable porous lattice structures. The SSR optimization was applied to a typical pelvic prosthesis to reconstruct a type II+III bone resection. The stress-shielding performance of the optimized implant based on the SSR approach was compared against the conventional optimization. The volume of the peri‑prosthetic bone predicted to undergo resorption post-surgery decreased from 44 to 18%. This improvement in stress-shielding resistance was achieved without compromising the structural integrity of the prosthesis. The SSR design approach has the potential to improve the long-term stability of custom-made pelvic prostheses.

Bone remodeling and cortical thinning distal to the femoral stem: a retrospective review

INTRODUCTION

There is a paucity of information on the bone remodeling that occurs distal to the femoral stem following total hip arthroplasty as most previous studies have focused on proximal changes. In this study, we report the cortical thinning that occur distal to the femoral stem after primary total hip arthroplasty.

METHODS

A retrospective review was performed at one institution over a 5-year period. 156 primary total hip arthroplasty procedures were included. The Cortical Thickness Index (CTI) was measured on both operative and non-operative hips at 1 cm, 3 cm and 5 cm below the prosthetic stem tip on anteroposterior radiographic images pre-operatively as well as at 6 months, 12 months and 24 months post-operatively. The difference in average CTI was measured using paired t-tests.

RESULTS

There were statistically significant decreases in CTI distal to the femoral stem at 12 months and 24 months (-1.3% and -2.8%, respectively). Greater losses were seen in female patients, patients older than 75, and patients with BMI less than 35 at 6 months postoperative. There were no differences in CTI at any time point on the non-operative side.

CONCLUSION

The current study demonstrates that patients undergo bone loss as measured by CTI distal to the stem in the first 2 years following total hip arthroplasty. Comparison to the contralateral non-operative side confirms that this change is greater than expected for the natural aging process. A greater understanding of these changes will help optimize post-operative management and direct future innovations in implant design.

Influence of stem design parameters on periprosthetic femoral fractures examined by subject specific finite element analyses

Due to the increasing number of periprosthetic femoral fractures (PFF), the optimisation of implant design gains importance. For the presented research a validated, subject specific finite element model of a human femur with an inlying total hip stem was used to compare the influence of different geometrical implant parameters on the development of PFF. The heterogeneous bone tissue was modelled on the basis of computed tomography scans. A ductile damage model with element deletion was applied to simulate bone fracture in a load case re-enacting a stumbling scenario. The results were compared in terms of fracture load, subsidence and fracture pattern to analyse the influence of friction at the implant-bone interface, implant size and stem length. The results showed that higher friction coefficients lead to an increase of fracture load. Also, the usage of an oversized implant has a negligible effect while an undersized implant reduces the fracture load by 48.9% for the investigated femur. Lastly, a higher fracture load was reached with an elongated stem, but the bending and change in fracture path indicate a more distal force transmission and subsequent stress shielding in the proximal femur.

Subsidence analysis of a cementless short stem THA using EBRA-FCA - A seven-year prospective multicentre study

Background

Metaphyseal fixation of short stem THA allows for minimally invasive surgery, less bone removal, improved bone load transfer and reduced stress shielding. Short stems facilitate the anatomic restoration i.a. of leg length, femoroacetabular offset, and center of rotation. However, metaphyseal fixation might cause impaired primary and/or secondary stability resulting in an inherent tendency for early axial migration and aseptic loosening eventually. The objective of this study was to investigate the long-term outcome and migration pattern of a calcar-guided short stem.

Methods

In a prospective multicenter study, 213 patients (224 THAs) were enrolled. Patients were followed for up to 84 months postoperatively. Clinical outcome was assessed using the Harris Hip Score and the VAS for pain and satisfaction. Standardized and calibrated radiographs were screened i.a. for stress shielding and loosening. Einzel-Bild-Roentgen-Analyse - femoral component analysis (EBRA-FCA) was used to detect longitudinal subsidence.

Results

At 7 year follow-up, n = 139/224 cases were available for analysis. All clinical parameters improved significantly (p < 0.001) and improvement persisted. There were no radiographic changes indicating stress shielding. EBRA-FCA revealed a mean subsidence of -1.44 mm followed by a stabilization. Weight >80 kg (p = 0.115), BMI <30 kg/m2 (p = 0.282), male gender (p = 0.246), and age <65 years (p = 0.304) seemed to be associated with a higher risk for migration. The cumulative revision rate was 2.23%. Revisions due to stem migration (0.89%) occurred early (mean time between index surgery and revision: 3.3 months).

Conclusions

If at all, there appears to be a pronounced initial subsidence, which stabilizes thereafter. Stem migration was rarely a compelling reason for failure or revision. Demographics do not seem to have a significant effect on migration pattern. The absence of radioluce lines, resorption or hypertrophy of the proximal femora support the hypothesis of a reduced stress shielding for metaphyseal anchoring short stems.

Bionic reconstruction of tension trabeculae in short-stem hip arthroplasty: a finite element analysis

BACKGROUND

Short-stem hip arthroplasty (SHA) is characterized by metaphyseal load transfer that effectively preserves the bone stock, but still suffers from stress shielding in the proximal femur. We designed a tension screw to mimic tension trabeculae in the new bionic collum femoris preserving (BCFP) short stem for bionic reconstruction, aiming to restore the biomechanics of hip joint.

METHODS

Native femur finite element model was constructed to investigate the biomechanics of hip joint based on computed tomography (CT) data. The maximum absolute principal stress/strain cloud chart allowed the direction of stress/strain to be assessed. Six BCFP models with different screw angles (5°, 10°, 15°, 20°, 25°, and 30°) and the Corail model were created. The stress/strain distribution and overall stiffness were compared between each of the BCFP and Corail implanted models.

RESULTS

The native model visualized the transfer pathways of tensile and compressive stress. The BCFP stems showed significantly higher stress and strain distribution in the greater trochanteric region compared to conventional total hip arthroplasty (THA). In particular, the BCFP-5° stem demonstrated the highest average strain in both medial and lateral regions and the overall stiffness was closest to the intact femur.

CONCLUSIONS

Stress transfer pathways of trabecular architecture provide biomechanical insight that serves as the basis for bionic reconstruction. The tension screw improves load transfer pattern in the proximal femur and prevents stress reduction in the greater trochanteric region. The BCFP-5° stem minimizes the stress shielding effect and presents a more bionic mechanical performance.

Doctor, what does my ceramic-on-ceramic hip arthroplasty weigh?

BACKGROUND

While total hip arthroplasty (THA) is generally very successful, certain patients remain dissatisfied. A common concern, especially in younger and more active patients, is the weight the implant will add to the hip. However, there is very little data available to help guide surgeons in addressing this concern. The goal of this study was therefore to compare the weight of the total hip arthroplasty implants to that of tissue removed.

HYPOTHESIS

That the weight of the total hip arthroplasty implants would exceed that removed tissue.

PATIENTS AND METHODS

A prospective study was conducted in 104 patients, without interfering with surgical plans. To account for different implant designs, especially relating to stem fixation, we included both cementless (n=51) and cemented (n=53) femoral stems. During the procedure, the removed bone and soft tissues, as well as the post-implantation cement were collected and weighed. The weight of the implants was provided by the manufacturer.

RESULTS

Both cemented and cementless THA implants proved significantly heavier than the removed bone and soft tissues. The median weight gained was 145g [IQR: 123-168] with the cementless implant and 241g [221-364] with the cemented implant (p<0.001). Multivariable regression analysis of patient- or implant factors influencing weight gain after THA revealed that weight gain decreased with patient BMI (β=-1.0, 95% CI: -2.0--0.1 (p=0.034)). In contrast, weight gain increased slightly with total implant weight (β=0.7, 95% CI: 0.6-0.8 (p≤0.001)). Further, weight gain was greater for women (β=19.0, 95% CI: 9.1-29.0 (p≤0.001) (men 150g [135-219], women 211g [157-250] (p=0.010)) and patients who received the cemented stem (β=40.0, 95% CI, 19.4-46.5, p≤0.001).

DISCUSSION

Current models cause a two- to three-fold gain of weight at the hip joint after THA. While it is not clear whether this weight increase has any clinical repercussions, this finding can be helpful when a patient raises questions on this topic during the preoperative counseling. More research is necessary to determine whether lighter implants may be beneficial for patients.

LEVEL OF EVIDENCE

III, case control study.

Osteoimmune Interactions and Therapeutic Potential of Macrophage-Derived Small Extracellular Vesicles in Bone-Related Diseases

Due to the aging of the global population, the burden of bone-related diseases has increased sharply. Macrophage, as indispensable components of both innate immune responses and adaptive immunity, plays a considerable role in maintaining bone homeostasis and promoting bone establishment. Small extracellular vesicles (sEVs) have attracted increasing attention because they participate in cell cross-talk in pathological environments and can serve as drug delivery systems. In recent years, an increasing number of studies have expanded our knowledge about the effects of macrophage-derived sEVs (M-sEVs) in bone diseases via different forms of polarization and their biological functions. In this review, we comprehensively describe on the application and mechanisms of M-sEVs in various bone diseases and drug delivery, which may provide new perspectives for treating and diagnosing human bone disorders, especially osteoporosis, arthritis, osteolysis, and bone defects.

Novel Design of the Compound Sleeve and Stem Prosthesis for Treatment of Proximal Femur Bone Defects Based on Topology Optimization

The loosening of traditional prosthetics is among the leading causes of surgical failure of proximal femoral bone defects. A novel compound sleeve and stem prosthesis was designed using an optimization methodology that combined an octet-truss porous structure with density-based topology optimization to improve stability, promote bone ingrowth, and enhance biomechanical properties. Biomechanical changes were assessed using finite element analysis. The distribution of stress, the strain energy density, and the relative micromotion in the optimized group were considered. The optimized sleeve prosthesis achieved a 31.5% weight reduction. The maximum stresses in the optimized group were observed to decrease by 30.33 and 4.74% at the back sleeve and neck part of stem prosthesis, with a 29.52% increase in the femur, respectively. The average stress in most selected regions in the optimized group was significantly greater than that in the original group (p &lt; 0.05). The maximum relative micromotion decreased by 15.18% (from 63.9 to 54.2 μm) in the optimized group. The novel designed compound sleeve and stem prosthesis could effectively improve the biomechanical performance of next-generation prosthetics and provide a microenvironment for bone ingrowth. The presented method could serve as a model for clinical practice and a platform for future orthopedic surgery applications.

Factors influencing the outcomes of minimally invasive total hip arthroplasty: a systematic review

Introduction

The present systematic review investigated possible factors which may influence the surgical outcome of minimally invasive surgery for total hip arthroplasty (MIS THA).

Methods

In January 2022, the Embase, Google Scholar, PubMed, and Scopus databases were accessed. All the clinical trials investigating the clinical outcome of MIS THA were considered.

Results

Data from 9486 procedures were collected. Older age was moderately associated with greater Visual Analogue Scale (VAS) (P = 0.02) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) (P = 0.009) at last follow-up, and shorter surgical duration (P = 0.01). Greater body mass index (BMI) at baseline was moderately associated with greater cup anteversion (P = 0.0009), Oxford Hip Score (OHS) at last follow-up (P = 0.04), longer surgical duration (P = 0.04), increased leg length discrepancy (P = 0.02), and greater rate of infection (P = 0.04). Greater VAS at baseline was weakly associated with greater VAS at last follow-up (P < 0.0001), total estimated blood lost (P = 0.01), and lower value of Harris Hip Score (HHS) (P = 0.0005). Greater OHS at baseline was associated with greater post-operative VAS (P = 0.01). Greater WOMAC at baseline was associated with lower cup anteversion (P = 0.009) and greater VAS (P = 0.02). Greater HHS at baseline was associated with shorter hospitalisation (P = 0.001).

Conclusion

Older age and greater BMI may represent negative prognostic factors for MIS THA. The clinical outcome is strongly influenced by the preoperative status of patients.

French Hip & Knee Society classification of short-stem hip prostheses: Inter- and intra-observer reproducibility

INTRODUCTION

In total hip replacement (THR), a short stem theoretically provides more physiological force transfer to the proximal femur, conserves bone stock and facilitates minimally invasive surgery. On the other hand, such implants involve a learning curve and incur risk of malpositioning or fracture and of secondary mobilization. There are several types of short stem, and classification is needed. Classifications exist, but are based more on implant length than on anchorage zone, and most have not been tested for reproducibility. The French Hip & Knee Society (SFHG) developed a short-stem classification based on anchorage zone inside the femur. The objectives of the present study were: (1) to present the classification, (2) to apply it to the short-stem models available in France and those widely used worldwide, and (3) to assess reproducibility.

HYPOTHESIS

The SFHG short-stem classification enables reproducible comparison.

MATERIAL AND METHOD

A short-stem classification according to anchorage zone was drawn up by an expert group. The stems and the classification were presented to 12 surgeons performing THR, who classified the stems according to the classification; a retest was performed 2 months later.

RESULTS

The classification is based on femoral stem anchorage site, in 5 types: type 1, cephalic; type 2, isolated cervical; type 3, Calcar femorale; type 4, metaphyseal; and type 5, conventional metaphyseal-diaphyseal, with shortened stems. Inter-observer reproducibility was 92.7% [95%CI: 91.7%-93.6%], with kappa 0.785 [95%CI: 0.755-0.814], and Lin test-rest concordance correlation coefficient 0.852 [95%CI: 0.836-0.869]. Intra-observer reproducibility was 94.0% [95%CI: 91.9%-96.1%], with kappa 0.820 [95%CI: 0.759-0.882], and Lin test-retest concordance correlation coefficient 0.820 [95%CI: 0.792-0.849].

DISCUSSION

This new classification enables femoral implants to be reproducibly compared according to anchorage zone.

LEVEL OF EVIDENCE

IV; retrospective study without control group.

Innovative Design Methodology for Patient-Specific Short Femoral Stems

The biomechanical performance of hip prostheses is often suboptimal, which leads to problems such as strain shielding, bone resorption and implant loosening, affecting the long-term viability of these implants for articular repair. Different studies have highlighted the interest of short stems for preserving bone stock and minimizing shielding, hence providing an alternative to conventional hip prostheses with long stems. Such short stems are especially valuable for younger patients, as they may require additional surgical interventions and replacements in the future, for which the preservation of bone stock is fundamental. Arguably, enhanced results may be achieved by combining the benefits of short stems with the possibilities of personalization, which are now empowered by a wise combination of medical images, computer-aided design and engineering resources and automated manufacturing tools. In this study, an innovative design methodology for custom-made short femoral stems is presented. The design process is enhanced through a novel app employing elliptical adjustment for the quasi-automated CAD modeling of personalized short femoral stems. The proposed methodology is validated by completely developing two personalized short femoral stems, which are evaluated by combining in silico studies (finite element method (FEM) simulations), for quantifying their biomechanical performance, and rapid prototyping, for evaluating implantability.

Similar stress repartition for a standard uncemented collared femoral stem versus a shortened collared femoral stem

Introduction: The design of uncemented femoral stems for use in total hip arthroplasty has evolved. Several uncemented short stems have been developed with different bone fixations, shapes, or stem lengths. The literature analyzing the biomechanical performance of short to standard stem lengths is limited. The aim was to compare the stress repartition on a standard uncemented stem and a shortened uncemented femoral stem with the same design features. Material and methods: This finite element analysis assessed the stress repartition on two femoral components with the same design (uncemented, collared, proximal trapezoidal cross-section, and a tapered quadrangular distal stem) but with two different lengths. The shortened stem was shorter by 40 mm compared to the standard stem. The stress repartition was analysed according to the Von Mises criterion. Results: The stress repartition was similar for the standard and shorter stem without significant difference (p = 0.94). The mean Von Mises stress was 58.1 MPa [0.2; 154.1] for the standard stem and 57.2 MPa [0.03; 160.2] for the short stem. The distal part of the standard stem, which was removed in the short stem, had mean stress of 3.7 MPa [0.2; 7.0]. Conclusion: The finite element analysis found similar stress repartitions between a standard uncemented collared stem and a short, collared stem with the same design. A clinical study assessing the clinical outcomes and the bone remodelling with a collared short stem would be interesting to confirm these first promising results.

Future of total hip arthroplasty with the Metha short stem in modern surgeries

The aim of the study was to analyse the results of uncemented total hip replacement, using the Metha (metaphyseal) stem. A total of 158 patients (70 females and 88 males) were qualified to the study and submitted to total hip arthroplasty (183 procedures altogether), using the Metha stem. The mean age of the patients on the day of surgery was 51.7 years (the range from 17 to 69 years). The mean follow up period was 9.2 years (the range from 5 to 13.5 years). Preoperative assessments gave poor scores, according to the Merle d’Aubigne and Postel classification, modified by Charnley. The average improvement after surgery, according to the used scale, was 6.9 points. A very good outcome was recorded in 154 cases (84.2%), a good outcome was achieved in 20 cases (10.9%) and a poor outcome was confirmed in 9 cases, while no satisfactory case was observed. Poor outcomes were associated with implant loosening. Extraskeletal ossification was noted in 10 cases (5.5%). According to the Kaplan–Meier estimator, the 10-year survival was 93.2% and 97.3% for the whole implant and the stem alone, respectively. 1. Our follow-up period of more than 9 years on the average, indicates that Metha stems produce excellent clinical and functional results in operated young patients with advanced degenerative changes of the hip joint. 2. Assuming a proper qualification for the procedure, the absence of complications and a correct surgical technique, which is slightly more difficult, when compared to standard stem implantation, the risk of aseptic loosening is fairly negligible.

Promising medium-term results of anterior approach with an anatomical short stem in primary hip arthroplasty

BACKGROUND

In the last decade, the increase in the use of the direct anterior approach to the hip has contributed to the diffusion of the use of short stems in orthopedic surgery. The aim of the study is to verify the medium-term clinical and radiographic results of a cementless anatomic short stem in the anterior approach to the hip. We also want to verify whether the use of the standard operating room table or the leg positioner can affect the incidence of pre- and postoperative complications.

MATERIALS AND METHODS

All total hip arthroplasty patients with a 1-year minimum follow-up who were operated using the MiniMAX stem between January 2010 and December 2019 were included in this study. Clinical evaluation included the Harris Hip Score (HHS), Western Ontario and McMaster Universities Hip Outcome Assessment (WOMAC) Score, and Short Form-36 (SF-36) questionnaires. Bone resorption and remodeling, radiolucency, osteolysis, and cortical hypertrophy were analyzed in the postoperative radiograph and were related to the final follow-up radiographic results. Complications due to the use of the standard operating room table or the leg positioner were evaluated.

RESULTS

A total of 227 patients (238 hips) were included in the study. Average age at time of surgery was 62 years (range 38-77 years). Mean follow-up time was 67.7 months (range 12-120 months). Kaplan-Meier survivorship analysis after 10 years revealed 98.2% survival rate with revision for loosening as endpoint. The mean preoperative and postoperative HHS were 38.35 and 94.2, respectively. The mean preoperative and postoperative WOMAC Scores were 82.4 and 16.8, respectively. SF-36 physical and mental scores averaged 36.8 and 42.4, respectively, before surgery and 72.4 and 76.2, respectively, at final follow-up. The radiographic change around the stem showed bone hypertrophy in 55 cases (23%) at zone 3. In total, 183 surgeries were performed via the direct anterior approach (DAA) on a standard operating room table, and 44 surgeries were performed on the AMIS mobile leg positioner. Comparison between the two patient groups did not reveal significant differences.

CONCLUSION

In conclusion, a short, anatomic, cementless femoral stem provided stable metaphyseal fixation in younger patients. Our clinical and radiographic results support the use of this short stem in the direct anterior approach.

LEVEL OF EVIDENCE

IV.