Hip Stem Research Articles

Longitudinal Radiographic Bone Density Measurement in Revision Hip Arthroplasty and Its Correlation with Clinical Outcome.

The subjective analysis of conventional radiography represents the principal method for bone diagnostics in endoprosthetics. Alternative objective quantitative methods are described but not commonly used. Therefore, semi-quantitative methods are tested using digital computation and artificial intelligence to standardize, simplify, and ultimately improve the assessment. This study aimed to evaluate the correlation between relative density progressions and clinical outcomes. Radiographs and clinical examinations before and 24 and 48 weeks after surgery were obtained from sixty-eight patients with a modular hip stem. For the calculation of the relative bone density, the modal gray values of the Gruen zones were measured using ImageJ and were normalized by gray values of the highest and lowest ROI. The clinical outcomes were measured according to the Harris hip score before evaluating them for correlations. Analyses were performed separately for subgroups and bone regions. The Harris hip score increased from 44.15 ± 15.00 pre-operatively to 66.20 ± 13.87 at the latest follow-up. The relative bone density adjustment of Gruen zone 7 showed a significant correlation to its clinical outcome. Other bone adaptations could be realistically reproduced and differences by regional zones and patients' histories visualized. Next to the simplicity and that no additional examination is required, the method provides good semi-quantitative results and visualizes adaptations, which make it suitable for use.

Finite element analysis of a stemmed hip prosthesis to reduce stress shielding in the proximal femur

A finite element analysis (FEA) was performed on four prosthesis designs with different internal structures within identical prosthetic stem geometry. A novel hexagonal structure akin to one of the strongest structures in nature is used internally in the stem. The hip implant designs were then analyzed for an applied force of 3227 N. This force was selected because a typical gait cycle generates forces up to 3.87 times the body weight in the hip joint. The FEA results were compared for various stem designs with rectangular cross-sections. The design objective for a hip stem is to have a low stiffness and stress shielding together with a very high fatigue life. The stress shielding reduction of the prothesis was measured by observing the change in stress distribution in a FE femur model before and after implant. Stress shielding was quantified volumetrically, and the surface stresses of the femur were considered to appraise any increased risk of periprosthetic fracture due to increased bone stress. Subsequently, the stems that had the lowest stress shielding models were then optimized. Results showed a reduction of stiffness of 18%, and a reduction in stress shielding of 30% compared to a solid stem.

REDUCTION OF METAL ION RELEASE IN CEMENTED HIP STEMS BY A ZIRCONIUM NITRIDE MULTILAYER COATING

ZrN-multilayer coating is clinically well established in total knee arthroplasty [1–3] and has demonstrated significant reduction in polyethylene wear and metal ion release [4,5].The goal of our study was to analyze the biotribological behaviour of the ZrN-multilayer coating on a polished cobalt-chromium cemented hip stem.CoCr28Mo6 alloy hip stems with ZrN-multilayer coating (CoreHip®AS) were tested versus an un-coated version. In a worst-case-scenario the stems with ceramic heads have been tested in bovine serum in a severe cement interface debonding condition under a cyclic load of 3,875 N for 15 million cycles. After 1, 3, 5, 10 & 15 million cycles the surface texture was analysed by scanning-electron-microscopy (SEM) and energy-dispersive x-ray (EDX). Metal ion concentration of Co,Cr,Mo was measured by inductively coupled plasma mass spectroscopy (ICP-MS) after each test interval.Based on SEM/EDX analysis, it has been demonstrated that the ZrN-multilayer coating keeps his integrity over 15 million cycles of severe stem cemented interface debonding without any exposure of the CoCr28Mo6 substrate.The ZrN-multilayer coated polished cobalt-chromium cemented hip stem has shown a reduction of Co & Cr metal ion release by two orders of a magnitude, even under severe stem debonding and high interface micro-motion conditions.ZrN-multilayer coating on polished cobalt-chromium cemented hip stems might be a suitable option for further minimisation of Co & Cr metal ion release in total hip arthroplasty. Clinical evidence has to be proven during the next years.

FIVE-YEAR RSA RESULTS ASSESSING SUBSIDENCE AND ROTATION OF THE PARAGON HIP SYSTEM CONFIRMING IMPLANT STABILITY

Roentgen Stereophotogrammetric Analysis (RSA) is the gold standard for measuring implant micromotion thereby predicting implant loosening. Early migration has been associated with the risk of long-term clinical failure. We used RSA to assess the stability of the Australian designed cementless hip stem (Paragon TM) and now report our 5-year results.Fifty-three patients were prospectively and consecutively enrolled to receive a Paragon hip replacement. Tantalum beads were inserted into the bone as per RSA protocol and in the implant. RSA x-rays were taken at baseline 1–4 days post-surgery, at 6 weeks, 6 months, 12 months, 2 years, and 5 years. RSA was completed by an experienced, independent assessor.We reported the 2-year results on 46 hips (ANZJS 91 (3) March 2021 p398) and now present the 5-year results on 27 hips. From the 2-year cohort 5 patients had died, 8 patients were uncontactable, 1 patient was too unwell to attend, 5 patients had relocated too far away and declined. At 5 years the mean axial subsidence of the stem was 0.66mm (0.05 to 2.96); the mean rotation into retroversion was 0.49˚ (−0.78˚ to 2.09˚), rotation of the stem into valgus was −0.23˚ (−0.627˚ to 1.56˚). There was no detectable increase in subsidence or rotation between 6 weeks and 5 years. We compared our data to that published for the Corail cementless stem and a similar pattern of migration was noted, however greater rotational stability was achieved with the Paragon stem over a comparable follow-up period.The RSA results confirm that any minor motion of the Paragon cementless stem occurs in the first 6 weeks after which there is sustained stability for the next 5 years. The combination of a bi-planar wedge and transverse rectangular geometry provide excellent implant stability that is comparable to or better than other leading cementless stems.

Bone Remodelling of the Proximal Femur After Hip Revision with a Metaphyseal-Fixation Femoral Stem Component.

Whether hip revision with a metaphyseal-fixation femoral stem component can restore the bone mass of the proximal femur remains unclear. The aims of this study were to identify whether the bone mineral density (BMD) of the proximal femur increases following hip revision with a metaphyseal-fixation femoral stem and to identify the factors associated with BMD recovery. This was a retrospective study involving 36 patients who underwent hip arthroplasty with a metaphyseal-diaphyseal fixation stem (standard length stem) and had indications for hip revision, which was performed with a proximal press-fit short-stem prosthesis for each patient. Dual-energy X-ray absorptiometry (DEXA) was used to obtain, evaluate, and compare the BMD at baseline and one year and two years postoperatively. The proximal femur was divided into several independent areas according to the Gruen zone (Gruen 1 to Gruen 7 from the greater trochanter counterclockwise to the lesser trochanter). Logistic regression analyses were used to assess potential factors significantly associated with an increase in BMD. An increased BMD was obviously identified in the proximal femur. Two years after the surgery, the BMD of the Gruen 1, Gruen 2, Gruen 6, and Gruen 7 areas had increased by 22.6%, 12.6%, 16.2% and 24.2%, respectively, relative to baseline. Three independent risk factors associated with bone mineral density recovery were identified: age (OR=1.100, 95% CI=1.005-1.203, P=0.038), osteoporosis (OR=14.921, 95% CI=1.223-182.101, P=0.034) and fair to poor hip function (OR=13.142, 95% CI=1.024-168.582, P=0.048). This study confirms that metaphyseal-fixation stem hip revision can indeed help restore bone mass in the proximal femur, especially in the Gruen 1, Gruen 2, Gruen 6 and Gruen 7 zones. It was also found that advanced age, osteoporosis, and fair to poor hip joint function were three important risk factors affecting the recovery of proximal femur bone mass after surgery. Retrospectively registered.

A novel hybrid design and modelling of a customised graded Ti-6Al-4V porous hip implant to reduce stress-shielding: An experimental and numerical analysis.

Stress shielding secondary to bone resorption is one of the main causes of aseptic loosening, which limits the lifespan of hip prostheses and exacerbates revision surgery rates. In order to minimise post-hip replacement stress variations, this investigation proposes a low-stiffness, porous Ti6Al4V hip prosthesis, developed through selective laser melting (SLM). The stress shielding effect and potential bone resorption properties of the porous hip implant were investigated through both in vitro quasi-physiological experimental assays, together with finite element analysis. A solid hip implant was incorporated in this investigation for contrast, as a control group. The stiffness and fatigue properties of both the solid and the porous hip implants were measured through compression tests. The safety factor of the porous hip stem under both static and dynamic loading patterns was obtained through simulation. The porous hip implant was inserted into Sawbone/PMMA cement and was loaded to 2,300N (compression). The proposed porous hip implant demonstrated a more natural stress distribution, with reduced stress shielding (by 70%) and loss in bone mass (by 60%), when compared to a fully solid hip implant. Solid and porous hip stems had a stiffness of 2.76kN/mm and 2.15kN/mm respectively. Considering all daily activities, the porous hip stem had a factor of safety greater than 2. At the 2,300N load, maximum von Mises stresses on the hip stem were observed as 112MPa on the medial neck and 290MPa on the distal restriction point, whereby such values remained below the endurance limit of 3D printed Ti6Al4V (375MPa). Overall, through the strut thickness optimisation process for a Ti6Al4V porous hip stem, stress shielding and bone resorption can be reduced, therefore proposing a potential replacement for the generic solid implant.

Surface Analysis of Ti-Alloy Micro-Grooved 12/14 Tapers Assembled to Non-Sleeved and Sleeved Ceramic Heads: A Comparative Study of Retrieved Hip Prostheses.

Ti6Al4V titanium alloy (Ti-alloy) sleeved ceramic heads have become widely used in revision surgery when the hip stem is left in situ. This solution guarantees a new junction between the bore of the ceramic head and the Ti-alloy sleeve, regardless of any possible, slight surface damage to the Ti-alloy taper of the stem. However, this solution introduces an additional Ti-alloy/Ti-alloy interface pairing, which is potentially susceptible to mechanically assisted crevice corrosion. This study evaluated both qualitatively and quantitatively the damage that occurred in vivo on Ti-alloy micro-grooved 12/14 tapers of (i) primary implants with non-sleeved ceramic heads (Group 1), (ii) secondary implants with non-sleeved ceramic heads (Group 2), and (iii) secondary implants with sleeved ceramic heads (Group 3). A total of 45 explants-15 for each group, including short-, medium- and long-neck heads-underwent optical evaluation for surface damage (Goldberg scoring), surface roughness analysis, and SEM/EDX analysis. The Goldberg scores did not reveal different patterns in the tapers' surface damage; surface damage was classified as absent or mild (surface damage score ≤2) in 94%, another 94%, and 92% of the analysed regions for Group 1, Group 2, and Group 3, respectively. Small but significant differences in morphological changes occurred in the tapers of the three groups: reductions no greater than a few percentage points in median values of roughness parameters were found in Group 1 and Group 2, while negligible changes were found in Group 3. SEM/EDX analysis revealed little (i.e., a slight increase in the oxygen content) to undetectable changes in the chemical composition on the Ti-alloy surface independently of the group. These results suggest that the Ti-alloy/Ti-alloy sleeve/taper junction is only mildly susceptible to mechanically assisted crevice corrosion. Assembling a sleeved ceramic head, with variable neck lengths up to a "long-neck", to a Ti-alloy micro-grooved 12/14 taper of a stem left in situ does not seem to increase the risk of revision due to trunnionosis, as long as junction stability (i.e., the proper seating of the sleeved ceramic head on the 12/14 taper) is achieved intraoperatively.

Additive manufacturing of a cementless hip stem demonstrator with local drug delivery functionality

Periprosthetic joint infection from implant surface colonization by pathogenic bacteria and subsequent biofilm formation remains a serious complication following total hip arthroplasty. Local delivery of antimicrobial drugs is an effective approach to prevent and treat such infection. This paper presents a prototype development process chain for a cementless hip stem from which an antimicrobial drug can be delivered directly to the implant surface. A systematic approach was followed in which the external surface of the hip stem represents an area requiring antibacterial coverage. Individual features were tested first to determine the zone of inhibition, represented by the two-dimensional area surrounding the drug release source where the pathogen cannot survive. This zone, determined for the antibiotic vancomycin against strains of the pathogen Staphylococcus aureus to be 15 mm in diameter, was simplified geometrically to circles of uniform radius which should cover the necessary implant surface. A freeform internal channel layout was then designed with source points for drug delivery at the centre of each of these circles. The final cementless stem design was manufactured with laser powder bed fusion from Ti6Al4V ELI. Internal features were free from any blockages and ∼3 mL of 15 mg/mL aqueous vancomycin could be loaded into the demonstrator stem without obstruction. Antimicrobial efficacy of the demonstrator was qualitatively evaluated in a custom experimental setup against Staphylococcus aureus Xen 31 incubated for 24 hours with a commercial hip stem as negative control. Qualitative evaluation of the inoculum revealed that surface colonization was prevented, indicating that the effective released vancomycin concentration exceeded the minimum inhibitory concentration of ∼5 µg/mL. The results contribute evidence to the applicability of laser powder bed fusion for implants with local drug delivery functionality. Further development of the concept could increase the efficacy and resource efficiency of periprosthetic joint infection prophylaxis and treatment.

Advancement in total hip implant: a comprehensive review of mechanics and performance parameters across diverse novelties.

The UK's National Joint Registry (NJR) and the American Joint Replacement Registry (AJRR) of 2022 revealed that total hip replacement (THR) is the most common orthopaedic joint procedure. The NJR also noted that 10-20% of hip implants require revision within 1 to 10 years. Most of these revisions are a result of aseptic loosening, dislocation, implant wear, implant fracture, and joint incompatibility, which are all caused by implant geometry disparity. The primary purpose of this review article is to analyze and evaluate the mechanics and performance factors of advancement in hip implants with novel geometries. The existing hip implants can be categorized based on two parts: the hip stem and the joint of the implant. Insufficient stress distribution from implants to the femur can cause stress shielding, bone loss, excessive micromotion, and ultimately, implant aseptic loosening due to inflammation. Researchers are designing hip implants with a porous lattice and functionally graded material (FGM) stems, femur resurfacing, short-stem, and collared stems, all aimed at achieving uniform stress distribution and promoting adequate bone remodeling. Designing hip implants with a porous lattice FGM structure requires maintaining stiffness, strength, isotropy, and bone development potential. Mechanical stability is still an issue with hip implants, femur resurfacing, collared stems, and short stems. Hip implants are being developed with a variety of joint geometries to decrease wear, improve an angular range of motion, and strengthen mechanical stability at the joint interface. Dual mobility and reverse femoral head-liner hip implants reduce the hip joint's dislocation limits. In addition, researchers reveal that femoral headliner joints with unidirectional motion have a lower wear rate than traditional ball-and-socket joints. Based on research findings and gaps, a hypothesis is formulated by the authors proposing a hip implant with a collared stem and porous lattice FGM structure to address stress shielding and micromotion issues. A hypothesis is also formulated by the authors suggesting that the utilization of a spiral or gear-shaped thread with a matched contact point at the tapered joint of a hip implant could be a viable option for reducing wear and enhancing stability. The literature analysis underscores substantial research opportunities in developing a hip implant joint that addresses both dislocation and increased wear rates. Finally, this review explores potential solutions to existing obstacles in developing a better hip implant system.

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.

A Radiographic Evaluation of Short Monolithic Femoral Hip Stem (SMF) for Dysplastic Osteoarthritis: Does Stem Alignment Influence on the Stability?

Background: There have been a few reports of SMFTM stem for dysplastic hips. The aim of this study is to evaluate the influence of stem alignment in dysplastic femurs on the stability of the implants and on the bone reaction by means of consecutive radiographical analysis. Methods: The preoperative diagnosis is dysplastic osteoarthritis in all patients. Twenty-nine hips in 28 patients after MIS-THA were followed up for two or more years (3.5 years in average). The average age at the surgery was 60. Those who belonged to Crowe’s classification I were 19 and those of II were 10 hips. The shape of the femur was classified as Dorr’s Type A in 5, B in 21, and C in 3 hips. Results: The varus alignment of the stem was 21 hips and non-varus was 8 hips. Crowe’s Grade did not have influence on the stem alignment. The ratio of non-varus alignment was more with Dorr’s Type C than with others. Achieving rate of mediolateral fixation was significantly higher in the varus alignment than in non-varus. The significant subsidence occurred in 3 hips (10.3%) although all stems became stable within 6 months. No revision was necessary. Conclusion: The varus insertion of the stem seemed more secure also in dysplastic femurs, but even non-varus ones seemed acceptable as they brought about no severe problem. Comprehensively evaluating the result, careful selection of the patient is essential to take the advantage of and to overcome the disadvantage of this short stem for dysplastic hips.

Computational assessment of growth of connective tissues around textured hip stem subjected to daily activities after THA

Longer-term stability of uncemented femoral stem depends on ossification at bone-implant interface. Although attempts have been made to assess the amount of bone growth using finite element (FE) analysis in combination with a mechanoregulatory algorithm, there has been little research on tissue differentiation patterns on hip stems with proximal macro-textures. The primary goal of this investigation is to qualitatively compare the formation of connective tissues around a femoral implant with/without macro-textures on its proximal surfaces. This study also predicts formation of different tissue phenotypes and their spatio-temporal distribution around a macro-textured femoral stem under routine activities. Results from the study show that non-textured implants (80 to 94%) encourage fibroplasia compared to that in textured implants (71 to 85.38%) under similar routine activity, which might trigger aseptic loosening of implant. Formation of bone was more on medio-lateral sides and towards proximal regions of Gruen zones 2 and 6, which was found to be in line with clinical observations. Fibroplasia was higher under stair climbing (85 to 91%) compared to that under normal walking (71 to 85.38%). This study suggests that stair climbing, although falls under recommended activity, might be detrimental to patient compared to normal walking in the initial rehabilitation period.

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.

Finite Element Assessment of a Hybrid Proposal for Hip Stem, from a Standardized Base and Different Activities

Choosing a suitable prosthesis to restore the functionality of the hip joint is a complex problem. The stem geometries, materials, and type of hip damage are critical factors for avoiding potential issues (aseptic loosening, fracture, and natural wear and tear). Comparing the available stems to select the best option is not straightforward because of the various loads and boundary conditions used in the tests, making the process difficult to compare the advantages and disadvantages among them. This work proposes stem assessment using a standardized base (generated from a literature review and ISO standards) to compare the stem geometries and present a new hybrid design to improve performance using the best qualities of the implants reported in the literature review. Sixteen hip prostheses were evaluated with the finite element method (FEM) using the same boundary and loading conditions through multi-objective analysis (von Mises stress and strain). Consequently, a hybrid geometry proposal was obtained by assessing specific points through the stem length (medial and lateral region) to define the cross-section (trapezoidal) and the new profile. The new hybrid implant proposal presented a stress reduction of 9.6% when compared to the reference implant P2-T (the implant with the best behavior) in the most critical activity (activity 4) using a titanium alloy. A similar stress reduction of 9.98% was obtained using ASTM F2996-13 and ISO 7206–4:2010(E) standards.

Dual-Energy X-Ray Absorptiometry (DEXA) Evaluation of the Bone Remodeling Effects of a Low-Modulus Composite Hip Stem After 2 Decades of Follow-Up.

Background: The Epoch FullCoat Hip Stem (Zimmer) was an isoelastic composite femoral stem developed to address stem stiffness concerns. Purpose: We sought to evaluate the long-term bone mineral density (BMD) of a cohort of patients who underwent total hip arthroplasty (THA) using the Epoch isoelastic stem and having more than 2-decade follow-up. Methods: We conducted a retrospective chart review of all patients who were study subjects at our institution in a multicenter prospective trial for the Food and Drug Administration of the Epoch implant in the mid-1990s. Through this, we identified 16 patients who had dual-energy X-ray absorptiometry (DEXA) scans, with which we could determine BMD preoperatively and at 3 points postoperatively. Of these, 5 agreed to participate in the study (the others were deceased, unable or declined to participate, or were lost to follow-up) with mean follow-up of 22 years. These participants underwent clinical and radiographic evaluation consisting of a Harris hip score, anteroposterior (AP) pelvis and AP and lateral hip X-rays, and DEXA evaluation of both hips. BMD in the 7 Gruen zones at last follow-up was compared with immediate postoperative and 2-year follow-up. Results: At last follow-up, all stems were well-fixed with signs of extensive osteointegration. In proximal Gruen zones 1 and 7, patients underwent a decrease in BMD with more modest losses in Gruen zone 1. All patients demonstrated an increase in BMD in zones 2 through 6 at latest follow-up, except for 1 patient in Gruen zone 6. BMD changes were not limited to the first 2 years of follow-up. Conclusion: This small follow-up cohort study found excellent long-term clinical results, no plain radiographic signs of notable stress shielding, and general maintenance of BMD at a follow-up of over 20 years for this isoelastic stem. Long-term bone remodeling after implantation of the isoelastic stem resulted in increased BMD in Gruen zones 2 through 6, suggesting that composite implant designs may still have a role in THA.

Drilling the cement mantle in well-fixed periprosthetic femur fractures is not associated with arthroplasty-related complications.

To determine if screw fixation across a cement mantle is safe and effective during plate fixation of well-fixed periprosthetic femur fractures. Retrospective cohort study. Academic Level I Trauma Center. Twenty-eight patients with AO/OTA 32A[B1] or 32A[C] periprosthetic femur fractures treated with open reduction and internal plate and screw fixation after cemented or uncemented hip arthroplasty. Screw placement into the cement mantle during internal fixation. Primary outcome was revision arthroplasty for aseptic loosening. Secondary outcomes included radiographic evidence of aseptic loosening, infection, nonunion, implant failure, and overall reoperation rate. There were 28 patients who met inclusion criteria. A total of 9 patients had screws placed in the cement mantle while the remaining 19 patients had screws placed around an uncemented stem. At a mean of 3.7-year follow-up, there were no cases of revision arthroplasty or aseptic loosening in either group. There were no significant differences in rates of infection, nonunion, implant failure, or reoperation rate between patients who had screw placement into a cement mantle vs around an uncemented stem. Drilling into the cement mantle during fixation of a periprosthetic femur fracture around a well-fixed cemented hip stem appears safe and effective. When possible, surgeons can consider bicortical screws around a cemented stem, given the biomechanical advantages over unicortical screw or cerclage fixation. Larger prospective trials confirming the safety of this technique are warranted prior to routine implementation. III.

CO145 Two-Year Outcomes Following Total Hip Replacement with ACTIS - a Matched Comparative Analysis from a US Healthcare System

Total hip replacement (THR) procedures are generally successful. The medial collared, triple tapered (MCTT) ACTIS primary hip stem was shown in early research to be associated with lower revision rates following THR compared to other implants. This study evaluates 2-year survivorship of matched cohorts of patients treated with MCTT vs comparators.

Minimally Invasive Anterolateral Approach Total Hip Arthroplasty Using Bone Preserving Short Femoral Stem: Intermediate Term Clinical and Radiological Results

Aim: The objective of this study was to evaluate the intermediate term clinical and radiological results of a Bone preserving short stem hip implant being operated through a minimally invasive anterolateral hip approach. Methods: In 20 consecutive patients suffering from osteoarthritis with 25 affected hip joints (five cases were bilateral), the clinical and radiological results of 25 hip arthroplasties performed in one hospital between October 2009 and May 2014 through a minimally invasive anterolateral approach using a cementless short stem prosthesis type Aida and a cementless cup type Ecofit with a ceramic-on-ceramic pairing were evaluated prospectively. The median age of patients at time of surgery was 60 years (range, 42-71 years), 15 male (4 were bilateral) and 5 female patients (one was bilateral) were included in the study. The median clinical follow up was 30 months (range, 2-88 months) and the median radiological follow up was 30 months (range, 2-88 months). Results: Harris Hip Score improved from a median preoperative value of 53 to a median postoperative value of 96 (range, 73-100) at follow up. 22 hips (88%) showed an excellent postoperative Harris Hip Score, 2 hips (8%) a good postoperative Harris Hip Score and one hip (4%) a fair postoperative Harris Hip Score. Only two patients complained of postoperative thigh pain. Regarding patient satisfaction, 15 patients (60%) were very satisfied, 10 patients (40%) were satisfied. None was unsatisfied. Radiological analysis showed that 19 stems (76%) were with stable bony ingrowth, two cases (8%) showed stable fibrous ingrowth. Four cases need further follow up for proper evaluation of stem fixation. Conclusion: The intermediate term survival of the Aida short stem hip implant being operated through a minimally invasive anterolateral hip approach is very promising and achieving the goals of a standard hip arthroplasty.

Short-Term Functional Outcomes of Short Femoral Neck Stems Are the Same as Those of Conventional Stems in Primary Total Hip Arthroplasty.

(1) Background: In this study, two types of implants were compared—a conventional hip stem and a femoral neck prosthesis. (2) Methods: The femoral neck prosthesis study group included 21 patients, while the conventional hip stem control group was 40 patients. The first examination was the pre-op check, while the next ones were performed 6 weeks, 1 year, and 3 years after surgery. The Harris Hip Score (HHS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Oxford Hip Score (OHS), University of California at Los Angeles Activity Score (UCLA), and Visual Analog Scale EQ (VAS EQ) forms were completed at each clinical study visit. (3) Results: The HHS in the femoral neck prosthesis group and the conventional hip stem group 6 weeks after surgery was 68.8 ± 16.47 and 67.6 ± 8.92, respectively, and 1 year after surgery, this was 93 ± 5.58 vs. 90.6 ± 5.17, respectively. The OHS of the femoral neck prosthesis group was 34.8 points after 6 weeks, 45.5 points after 1 year, and 43.9 points after 3 years. The respective values in the conventional hip stem group were 35.5, 41.55, and 42.13 points. The WOMAC values for the femoral neck prosthesis group were 70.6, 92.7, and 86 points, respectively, while for the conventional hip stem group, they were 74, 88.1, and 86.1 points. The UCLA scores recorded in the conventional hip stem group ranged from 3.15 to 5.05 points, but a higher mean value of 5.33 points was obtained in the femoral neck prosthesis group. VAS EQ was equal to 84 points three years after the operation. (4) Conclusions: The study showed no significant differences in the functional scores of both groups, and the new type of cervical femoral stem could be the first choice in younger patients.

Computational prediction of the long-term behavior of the femoral density after THR using the Silent Hip stem

Aseptic loosening due to the progressive periprosthetic bone resorption following total hip replacement is a crucial concern, that causes complications and failure of the arthroplasty surgery. The mismatch in stiffness between the hip implant and the surrounding femoral bone is one of the key factors leading to bone density resorption. This paper aimed to investigate the long-term response of the femoral bone after THR using the Silent Hip stem. For this purpose, a validated thermodynamic-based computational model was used to compute the change in bone density before and after THR. This model incorporated essential factors involved in bone remodeling process, such as mechanical loading, and biochemical affinities. The results of the numerical simulations using 3D finite element analysis were analyzed in five zones of interest qualitatively and quantitatively. Bone density predictions showed notable bone resorption in cervical areas, specifically in zone 1 and zone 5 of −18.7% and −14%, respectively. Conversely, bone formation was observed in the greater trochanter area (zone 2) of +25%. Stress shielding seemed to occur at cervical area due to the reduction in the mechanical loading in this region. Based on the quantitative analysis of the bone density distribution throughout the femoral bone, it appears that the Silent Hip stem achieved less bone resorption compared to conventional hip stem designs reported in the literature, which could be used for active patients.