Abstract:In the early days of artificial joint replacement, the choice of bearing material was a decisive factor for the long-term success of an artificial joint. Through intensive research and development over more than three decades, the materials and their processing and sterilisation have been continuously improved. The materials used today all offer a high degree of safety and durability. As a result - In combination with the strict approval guidelines - the choice of a specific material is no longer as important as it was when artificial joint replacement was first introduced.This article focuses on the results of primary hip arthroplasty in eight established registries. In all of the registries examined, ceramic-ceramic bearings and bearings with cross-linked polyethylene cups or liners in combination with heads made of all common head materials, show very good long-term results with a low revision risk. The choice of head size varies considerably in the individual registries. In America, large (36 mm diameter) or very large ceramic heads (over 36 mm) tend to be used, even though the country's own registry warns against very large heads. In Australia, also mainly large heads are used. However, recent analyses indicate that large heads (36 mm) have a higher risk of revision in the long term. In Scandinavian countries, the Netherlands, and New Zealand, smaller heads (32 mm diameter) tend to be predominantly used. The situation in the other countries whose registries were analysed lies somewhere in between, with each country having its own special features. In England, the results of surface replacement are being closely monitored. The results are inconspicuous for the recommended patient population. The further performance of the newly introduced ceramic surface replacement is being followed with great interest. In Germany, the proportion of heads with a diameter of 36 mm is growing continuously, which should be critically questioned when considering the results from Australia. Ceramic-ceramic bearings are being used less and less frequently, even though they perform similarly well overall to hard-soft bearings and even better in some settings. Switzerland is the only country where this bearing still accounts for more than 10 % of treatments. Sweden no longer differentiates between materials in its annual report, but instead provides a ranking of the 74 Swedish clinics in terms of revision risk. In the Netherlands, the 32 mm head diameter is still the most frequently chosen. The German registry has the highest granularity of all registries. The use of dual mobility systems in primary endoprosthetics varies greatly between registries.Despite the differences in head materials and diameters, the results for hip replacements using HXLPE or ceramic cup inlays, show a comparable overall survival rate of approximately 96 % to 98 % after 5 years. What is noteworthy is the approach taken by the Swedish mother of all endoprosthesis registries, which no longer reports results for the different bearing combinations or head sizes, but instead reports the individual results for each facility. The overall good results for all currently used bearing materials in combination with appropriate patient selection make this a comprehensible step. Consequently, the respective clinical care quality is becoming increasingly important.

BACKGROUND:Collared cementless hip stems have demonstrated a reduced incidence of periprosthetic femoral fractures compared to collarless counterparts. Many fractures occur during implantation, when collarless stems are seated to achieve press-fit, causing critical tensile strains in the femur. Collared stems can limit excessive seating and subsidence through calcar-collar contact. This study aimed to explain the clinically observed smaller fracture rates with collared stems by comparing strain distributions during implantation and loading between collared and collarless stems. It was hypothesized that collared stems distribute applied forces through both the collar and stem, increasing compressive axial and shear strains, allowing higher load tolerance. METHODS:Seven collared and seven collarless stems were implanted with constant velocity (0.1 mm/s) in porcine femurs until failure. Two human cadaveric femurs were tested as proof of concept. Shear, axial compressive and tangential tensile strains were compared alongside fracture patterns, subsidence and forces. FINDINGS:Collared stems in porcine femurs resisted approximately twice as much force until failure occurred (collared: 4187 N, collarless: 1980 N; p < 0.001), with similar tangential tensile strains (1 % to 1.4 % p = 0.805) and subsidence of 1.6 mm for collarless and 1.1 mm for collared stems at different failure forces (p = 0.288). Axial compressive strain was heavily increased by 1147 % with collared stems (collared: 1.2 %, collarless: 0.1 %; p = 0.026). Human femurs exhibited similar trends. INTERPRETATION:During loading, the collar prevents periprosthetic femoral fractures by increasing axial compressive strains instead of causing critical excessive tangential tensile strains (hoop strains) that can result in fractures.

Abstract:Hip joint replacement with total hip arthroplasty is a frequently performed and highly successful treatment option that is increasingly being offered to younger patients. Due to their longer life expectancy, the longevity expectations for the endoprosthesis have also increased. Physical activity and sports have a positive effect on the risk of loosening. There is no scientific evidence that participation in any specific sport adversely affects the longevity of a hip endoprosthesis. Nevertheless, recommendations to patients vary widely from surgeon to surgeon, and some types of sport are still generally discouraged. This article provides an overview of both recent and older studies addressing the question "What sports are still permissible with an artificial hip?" It attempts to clarify that high joint forces are not necessarily associated with high risk of damage, as the anatomy of muscles and bones, together with muscle function, is optimised to accomodate higher loads. High forces pose a risk only if they are applied in directions not physiologically intended or if the implant is poorly anchored in the bone. The principle that only sports which can be performed with sufficient coordination should be undertaken is therefore certainly correct. Overall, patients should be encouraged to engage in activities in which they feel comfortable and are aware of their own limitations and risks. Hip resurfacing represents an option for a carefully selected patient population, potentially allowing for a return to elite sports. However, the indication requires careful consideration of the local and systemic risks associated with metal-on-metal articulations, as well as the patient's age and athletic aspirations. The extent to which new developments without a metal-on-metal articulation may allow for an expanded indication must be carefully evaluated. Clear guidance from the surgeon to the patient regarding the timeline and postoperative activity following hip replacement with an H-TEP or hip resurfacing is necessary to support patient confidence.

BACKGROUND:In cementless total hip arthroplasty stems are inserted into the bone by mallet blows. Surgeons are not instructed to adjust the force of their blows to differences among patients especially with regard to weight. Whether this is linked to complications is yet unknown. This study investigated factors that could affect the mechanical behavior of the femur-tissue system. METHODS:Four cadavers were subject to two total hip arthroplasties by the same surgeon - one side via a lateral approach and the contralateral side via a direct anterior approach. A mass-spring-damper model was used to replicate the mechanical response of the femur-tissue system of the cadavers and make them comparable. FINDINGS:The mechanical response in terms of mass-spring-damper parameters differed between the approaches (lateral: 16.5 kg, 29.7 N/mm, 467.1 Ns/m; direct anterior: 11.5 kg, 41.7 N/mm, 553.0 Ns/m). INTERPRETATION:Common metal-on-metal mallet blows in surgery are very short and mostly excite high frequencies that are clearly above the natural frequency of the femur-tissue system. Those overcritical force impulses make the stem slide into the femur before the bone can even start moving. Hence, the individual mechanical behavior of the femur-tissue system can be disregarded provided that the force is applied with very short blows. This needs to be considered for any attempt to replace the mallet in the operation theater (e.g. automated surgical impaction tools) or to modify the mallet (e.g. alternative tip material). Furthermore, it may provide guidance on the fixation of femurs in in vitro testing to mimic surgical reality.

Aims:Modular revision stem fracture is a rare but difficult complication after hip arthroplasty revision. The purpose of this German Arthroplasty Registry (EPRD)-based study was to investigate whether the overall re-revision rate and the re-revision reasons of modular revision stems compared with monobloc stems are different. Methods:A total of 291 re-revisions occurring within five years after implantation of a revision stem (n = 2,039) documented in the EPRD were analyzed using Kaplan-Meier survival analysis and Cox regression. Stem type (modular: n = 1,026, monobloc: n = 1,013) and revision reason were investigated as independent variables, while BMI, sex, age, hospitals' annual revision volume, and Elixhauser score were treated as confounding variables. Cases with an infection at index surgery were analyzed separately. Results:Re-revision risk after five years was similar for either stem type (modular: 18.7% ( 95% CI 15.9 to 21.9); monobloc: 15.6% (95% CI 13.2 to 18.4); p = 0.200). One stem fracture of a modular revision stem was reported. The main reasons for re-revision were infection (modular/monobloc: 50%/60% of all revisions; p = 0.200), dislocation (19.8%/9.6%; p = 0.045), and loosening (12.2%/11.4%; p > 0.999). An Elixhauser score of 4 and above was associated with a higher hazard ratio (HR) for re-revision for either stem type (modular/monobloc: HR 2.01; p = 0.026/HR 2.44; p = 0.004), as well as a BMI category above 25/40 (modular/monobloc: HR 1.73 to 3.25; all p < 0.025/HR 3.61; p < 0.001). An infected index surgery increased the re-revision risk after one year to 26.0% (95% CI 22.2% to 30.3%) compared with 8.3% for noninfected cases (95% CI 7.0% to 9.8%) (p < 0.001) independent of stem type. Conclusion:A high BMI increases the HR for revision for either stem design but not due to mechanical implant failure. Infection at the index operation increases re-revision risk significantly, and is also the dominant reason for re-revision independent of stem type.

An evaluation of the stabbing intensity including the degree of force necessary to cause a particular injury is a common task for forensic pathologists in court. Biomechanical analyses are essential for collecting objective data, serving as a baseline comparison among the highly individual circumstances of each case. However, previous investigations have utilized instruments only resembling the murder weapons as well as tissues from individuals other than the victim, including animal tissues or substitutes, which limits their applicability to forensic casework. In this study, a homicidal head stab case is presented, in which the blade penetrated over its full width, crossing the midline and injuring the brainstem and the contralateral hemisphere. A skull sample from the victim’s contralateral side corresponding to the injured region was retrieved during the autopsy. For the stabbing experiments, a pendulum setup incorporating the original blade was employed. Three consecutive stabs were executed on the bone sample of the victim obtained at autopsy. Additionally, two other skull samples from different cadavers were each subjected to a single stab. The stabbings were performed at varying bone thicknesses (3–8 mm) and momenta (3.1–13.4 Ns) to account for mild, moderate, and strong impacts. High impact velocities resulted in either a blade entry across its full width, resembling the homicide case, or a multi-fragmental destruction of the bone. Mild and moderate impacts were insufficient to achieve full-thickness penetration of the skull. When stabbings were performed on a considerably thicker skull sample than that involved in the homicide case, only the blade tip penetrated the bone without achieving full-thickness perforation. By utilizing tissue from the victim and the real weapon for biomechanical analysis of the stabbing intensity including the minimum degree of force and momenta in homicidal stab cases, this experimental setup closely mimics the conditions of the actual case. Forensic investigators should proactively recommend such biomechanical analyses and secure appropriate tissue samples during autopsy to obtain objective experimental data relevant to legal questions.

[This corrects the article DOI: 10.1016/j.artd.2025.101622.].

[This corrects the article DOI: 10.1371/journal.pone.0303682.].

Aims:Sufficient primary implant stability with minimal bone damage is one of the challenges for uncemented implant fixation to prevent periprosthetic fractures and implant loosening. A pilot study on a non-viscoelastic material (polyurethane foam) showed a reduced impaction force when using vibratory implant insertion. This study assessed the effectiveness of vibratory implant insertion compared to an established implant insertion method in physiological viscoelastic bone from porcine hips. Methods:Acetabular components were impacted line-to-line and into 1 mm nominal undersized cavities in porcine acetabula (n = 24 in total, n = 6 acetabula per group of study) using vibration (60 Hz) and 1 Hz (established) impaction methods. The impaction force, remaining polar gap, and lever-out moment were measured and compared between the impaction methods and different press-fits. Results:The vibratory impaction method produced almost 40% lower impaction forces at both press-fit levels. However, complete seating at the nominal press-fit of 1 mm was not achieved, and primary stability was lower for the vibratory impaction for either press-fit. Conclusion:Bone fracture risk due to high impaction forces could be reduced by vibrational implant insertion at the cost of a reduction in primary stability. The outcome of the vibratory impaction method in porcine bone was similar to a previous study using polyurethane foams, suggesting that the viscoelasticity of bone may not play a crucial role during press-fit implant impaction.

Aims Periprosthetic fracture and implant loosening are two of the major reasons for revision surgery of cementless implants. Optimal implant fixation with minimal bone damage is challenging in this procedure. This pilot study investigates whether vibratory implant insertion is gentler compared to consecutive single blows for acetabular component implantation in a surrogate polyurethane (PU) model. Methods Acetabular components (cups) were implanted into 1 mm nominal under -sized cavities in PU foams (15 and 30 per cubic foot (PCF)) using a vibratory implant insertion device and an automated impaction device for single blows. The impaction force, remaining polar gap, and lever -out moment were measured and compared between the impaction methods. Results Impaction force was reduced by 89% and 53% for vibratory insertion in 15 and 30 PCF foams, respectively. Both methods positioned the component with polar gaps under 2 mm in 15 PCF foam. However, in 30 PCF foam, the vibratory insertion resulted in a clinically undesirable polar gap of over 2 mm. A higher lever -out moment was achieved with the consecutive single blow insertion by 42% in 15 PCF and 2.7 times higher in 30 PCF foam. Conclusion Vibratory implant insertion may lower periprosthetic fracture risk by reducing impaction forces, particularly in low -quality bone. Achieving implant seating using vibratory insertion requires adjustment of the nominal press -fit, especially in denser bone. Further preclinical testing on real bone tissue is necessary to assess whether its viscoelasticity in combination with an adjusted press -fit can compensate for the reduced primary stability after vibratory insertion observed in this study.

Increasing the stem size during surgery is associated with a higher incidence of intraoperative periprosthetic fractures in cementless total hip arthroplasty with fully coated tapered wedge stems, especially in femurs of Dorr type A. If in contrast a stem is implanted and sufficient primary stability is not achieved, such preventing successful osseointegration due to increased micromotions, it may also fail, especially if the stem is undersized. Stem loosening or periprosthetic fractures due to stem subsidence can be the consequence. The adaptation of an established stem design to femurs of Dorr type A by design modifications, which increase the stem width proximally combined with a smaller stem tip and an overall shorter stem, might reduce the risk of distal locking of a proximally inadequately fixed stem and provide increased stability. The aim of this study was to investigate whether such a modified stem design provides improved primary stability without increasing the periprosthetic fracture risk compared to the established stem design. The established (Corail, DePuy Synthes, Warsaw, IN, US) and modified stem designs (Emphasys, DePuy Synthes, Warsaw, IN, US) were implanted in cadaveric femur pairs (n = 6 pairs) using the respective instruments. Broaching and implantation forces were recorded and the contact areas between the prepared cavity and the stem determined. Implanted stems were subjected to two different cyclic loading conditions according to ISO 7206-4 using a material testing machine (1 Hz, 600 cycles @ 80 to 800 N, 600 cycles @ 80 to 1600 N). Translational and rotational relative motions between stem and femur were recorded using digital image correlation. Broaching and implantation forces for the modified stem were up to 40% higher (p = 0.024), achieving a 23% larger contact area between stem and bone (R2 = 0.694, p = 0.039) resulting in a four times lower subsidence during loading (p = 0.028). The slight design modifications showed the desired effect in this in-vitro study resulting in a higher primary stability suggesting a reduced risk of loosening. The higher forces required during the preparation of the cavity with the new broaches and during implantation of the stem could bare an increased risk for intraoperative periprosthetic fractures, which did not occur in this study.

The ideal stem size and stem position is important for the success of total hip arthroplasty, since it can affect early implant loosening and periprosthetic fractures (PPF). This study aimed to investigate how small deviations from the ideal stem size and position influences the PPF risk and primary stability. Six experienced surgeons performed preoperative templating based on which the benchmark size for each femur was determined. Consecutive implantations were performed in six cadaveric femur pairs-one side was implanted with an undersized stem followed by the benchmark size and the contralateral side with a benchmark size followed by an oversized stem (Corail, Depuy Synthes). Moreover, three different alignments (six varus, six neutral, six valgus-undersized) were compared using 18 femurs. Cortical strains during broaching and implantation were measured, and laser scans were used to determine final stem position. All specimens underwent dynamic loading. Primary stability was estimated from stem subsidence and pull-out forces. Templated stem size varied between surgeons (+/- 1 size; p = 0.005). Undersizing increased stem subsidence by 320% (p < 0.001). Oversized stems exhibited 52% higher pull-out forces (p = 0.001) and 240% higher cortical strains (p = 0.056). Cortex strains increased with varus alignment (R-2 = 0.356, p = 0.011) while primary stability decreased with valgus stem alignment (p = 0.043). Surgeons should be aware that small deviations from the ideal stem size and malalignments of the stem can significantly alter the mechanical situation and affect the success of their surgery.

Implant fracture of modular revision stems is a major complication after total hip arthroplasty revision (rTHA). Studies looking at specific modular designs report fracture rates of 0.3% to 0.66% whereas fractures of monobloc designs are only reported anecdotally. It is unclear whether the overall re-revision rate of modular designs is higher and if, whether stem fractures or other revision reasons are responsible for this elevation.All revisions within 5 years after implantation of a revision stems (n0=13,900; n5=2506) were analysed using Cox regression with design (modular: n=17, monobloc: n=27), BMI, Sex and Elixhauser Score as independent variables. One stage and two stage revisions were analysed separately (1-stage: modular n= 7,102; monobloc n= 4,542; 2-stage: 1,551 / 704). The revision volume of the hospitals was also considered (low: <20 revisions, medium: 21–50 revisions, high: >50 revisions).For the 1-stage revisions, the re-revision risk after 4 years was 14,3% [13.2%, 15.5%] for monobloc and 17.4% [16.40%, 18.40%] for modular stems (p< 0.001). Stem fracture was the reason for re-revision in 2.4% of the modular (fracture rate 0.42%) and 0.6% of the monobloc revisions. The difference in re-revision rates between the designs was mainly due to differences in dislocation and stem loosening. For the 2-stage revisions, the revision risks for either design were similar (21.7% [18,5%, 25.4%] vs. 23.0% [20.8%, 25.4%]; p=0.05). Patient characteristics influenced the comparison between the two designs in the 1-stage group but very little in the 2-stage group.Modular revision stem fractures only contribute very minor to re-revision risk. In 2-stage revisions, no difference in overall re-revision rates between designs was observed. This might indicate that the differences observed for 1-stage procedures are due to differences between the patient cohorts, not reflected by the parameters available or surgeon choice.

Compression pressure changes in dynamic conditions under textile compression devices have a critical impact on the success of compression therapy. Models exist to predict the level of compression pressure, but not the actual change in pressure. This paper aims to derive a formula to accurately determine the pressure change under textile compression devices, to investigate the factors influencing the pressure change and to verify their effects through theoretical analysis. Firstly, a formula based on Laplace's law is presented which mathematically describes the dependencies of pressure changes. Secondly, a simulation is carried out to demonstrate the effect of these dependencies on pressure changes using theoretical textile curve functions. Finally, the effect of these dependencies is demonstrated by testing short- and long-stretch bandages in a tensile testing machine and using the recorded material curves to simulate a theoretical application of these bandages to the lower limbs. The results show that the change in pressure is not solely determined by the intrinsic properties of the material, but is influenced by several variables, including the mechanical performance of the textile materials during stretching, the target pressures for application of the textile material, and the body geometries to which the material is applied. Pressure change cannot be a constant for textile compression devices such as bandages. The research increases the understanding of the factors that influence pressure changes in compression device materials. The findings may have implications for the design and selection of compression textiles in clinical applications.

The implantation of uncemented prostheses requires the application of sufficient forces to achieve a press-fit of the implant in the bone. Excessive forces have to be omitted to limit bone damage. Force measurements along the force transmission path between mallet and implant are frequently used to investigate this trade-off. Placing a load cell at a position of interest (PoI), which might be the implant bone interface or the head taper junction, is technically challenging or even impossible so that nearby positions are chosen. Thus, a certain inertia and stiffness remain between the PoI and the sensor, and consequently the measured dynamic forces differ from those at the PoI. This experimental and numerical study aimed to investigate the amount of force reduction along the transmission path while joining femoral heads to stem tapers. Forces were measured in vitro at the tip of the mallet, directly above the polymer tip of the impactor and below the stem taper. Springs and masses were used to represent the responding tissue of a patient. A semi-empirical numerical model of the force transmission path was developed and validated in order to simulate a larger range of responding tissue properties than experimentally possible and to investigate the influence of different surgical instruments. A distinct attenuation was observed since the peak forces at the impactor reached 35% of the applied peak forces and 21% at the stem taper, respectively. The force curves were replicated with a median root mean square error of 3.8% of the corresponding mallet blow for the impactor and 3.6% for the stem. The force measurement position and the used surgical instruments have a strong influence on the measured forces. Consequently, the exact measurement conditions with regard to sensor positioning and used surgical instruments have to be specified and hence only studies with similar setups should be compared to avoid misestimation of the forces at the PoI. The proposed dynamic numerical model is a useful tool to calculate the impact of the chosen or changed mechanical parameters prior to executing experiments and also to extrapolate the effect of changing the applied forces to the resulting forces at the PoI.

Aims:Despite higher rates of revision after total hip arthroplasty (THA) being reported for uncemented stems in patients aged > 75 years, they are frequently used in this age group. Increased mortality after cemented fixation is often used as a justification, but recent data do not confirm this association. The aim of this study was to investigate the influence of the design of the stem and the type of fixation on the rate of revision and immediate postoperative mortality, focusing on the age and sex of the patients. Methods:A total of 333,144 patients with primary osteoarthritis (OA) of the hip who underwent elective THA between November 2012 and September 2022, using uncemented acetabular components without reconstruction shells, from the German arthroplasty registry were included in the study. The revision rates three years postoperatively for four types of stem (uncemented, uncemented with collar, uncemented short, and cemented) were compared within four age groups: < 60 years (Young), between 61 and 70 years (Mid-I), between 71 and 80 years (Mid-II), and aged > 80 years (Old). A noninferiority analysis was performed on the most frequently used designs of stem. Results:The design of the stem was found to have no significant influence on the rate of revision for either sex in the Young group. Uncemented collared stems had a significantly lower rate of revision compared with the other types of stem for females in the Mid-I group. There was a significantly higher rate of revision for uncemented stems in females in the Mid-II group compared with all other types of stem, while in males the rate for uncemented stems was only significantly higher than the rate for cemented stems. Cemented stems had a significantly lower revision rate compared with uncemented and short stems for both sexes in the Old cohort, as did females with collared stems. The rate of immediate postoperative mortality was similar for all types of stem in the Old age group, as were the American Society of Anesthesiologists grades. Conclusion:In patients aged > 80 years, uncemented and short stems had significantly higher revision rates compared with cemented and collared stems, especially in females. The design of the stem and type of fixation have to be analyzed in more detail than only considering cemented and uncemented fixation, in order to further improve the success of THA.

Introduction: In revision surgery, modular implant components allow the surgeon to tailor the characteristics of the implant to the bone situation. Relative motion can occur at the tapered modular connection, leading to fretting corrosion and subsequent biological reactions, particularly due to poor assembly and contamination of the tapered connection. The aim of this study was to demonstrate whether incomplete assembly and inadvertent contamination of the modular taper causes a change in junction strength. Material and methods: Modular taper junctions between the neck and the stem (n = 48) were divided into seven groups that differed with respect to contamination (native, contaminated, cleaned) and assembly conditions (secured, pre-tensioned and secured). Contamination was achieved by a combination of porcine bone particles and bovine blood. For each group, the number of rotations of the torque limiter while securing the conical connection was recorded. The implants were subjected to cyclic loading. DIC was used to determine neck rotation, micromotion and axial subsidence. Loosening torque of the locking screw and pull-off forces were measured as an equivalent of residual taper junction strength. Results: Contamination of the taper junction, especially in combination with improper assembly of the components, significantly increased the rotation (35.3 +/- 13.7 degrees vs. 2.4 +/- 4.4 degrees; p <0.001), micromotion (67.8 +/- 16.9 mu m vs. 5.1 +/- 12.1 mu m, p <0.001) and axial subsidence (-34.1 +/- 16.9 mu m vs. 4.3 +/- 10.9 mu m; p <0.001) of the neck relative to the stem. Conclusion: Intra-operatively, contamination of the taper surface can be identified by the need for multiple turns when tightening the locking screw. Correct cleaning with the new taper cleaning instrument and complete assembly with pre-tensioning may reduce the risk of early failure and fatigue fracture of the modular taper connection.

Three-dimensional body scanners are attracting increasing interest in various application areas. To evaluate their accuracy, their 3D point clouds must be compared to a reference system by using a reference object. Since different scanning systems use different coordinate systems, an alignment is required for their evaluation. However, this process can result in translational and rotational misalignment. To understand the effects of alignment errors on the accuracy of measured circumferences of the human lower body, such misalignment is simulated in this paper and the resulting characteristic error patterns are analyzed. The results show that the total error consists of two components, namely translational and tilt. Linear correlations were found between the translational error (R2 = 0.90, … 0.97) and the change in circumferences as well as between the tilt error (R2 = 0.55, … 0.78) and the change in the body’s mean outline. Finally, by systematic analysis of the error patterns, recommendations were derived and applied to 3D body scans of human subjects resulting in a reduction of error by 67% and 84%.

Die Instabilität ist eine der Hauptursachen für Revisionen von Hüftendoprothesen. Durch spezielle Polyethyleninlays soll die Gelenkstabilität des Hüftgelenkersatzes verbessert werden. Im Juli 2022 wurde im The Bone & Joint Journal eine vergleichende Studie mit Daten des Endoprothesenregister Deutschland (EPRD) veröffentlicht. Dabei wurde die Häufigkeit von Revisionsoperationen unter Verwendung von Standardinlays gegenüber sogenannten Spezialinlays bei primären, zementfreien Hüfttotalendoprothesen untersucht. Aufgrund der Ergebnisse der Studie erfolgte anschließend eine deutschlandweite Umfrage, um die Indikation und Anwendung dieser speziellen Inlays zu verstehen. Eingeschlossen wurden 151.096 primäre, elektive, zementfreie Hüfttotalendoprothesen, die von November 2012 bis November 2020 im EPRD erfasst wurden. In einer „Competing-risk“-Analyse wurden die kumulativen Inzidenzen für den Endpunkt Revision aufgrund mechanischer Komplikation für Standard-Polyethyleninlays im Vergleich zu überhöhten („lipped“), angulierten („angulated“), lateralisierten („offset“) und kombiniert angulierten/lateralisierten („angulated/offset“) Polyethyleninlays berechnet. Einflussvariablen wurden mit einer multivariaten Cox-Regression identifiziert. In der nachfolgenden Online-Umfrage zum Nutzungsverhalten von überhöhten Inlays schlossen 237 von 789 angeschriebenen Kliniken einen Fragebogen ab. Nur lateralisierte Inlays waren in der Analyse den Standardinlays bezüglich mechanischer Komplikationen überlegen. Für die anderen analysierten Inlaytypen konnte dies nicht gezeigt werden. Auch wenn lateralisierte Inlays eine geringere kurz- bis mittelfristigere Wahrscheinlichkeit einer mechanischen Komplikation zeigen, sollte die durch die Lateralisierung des Drehzentrums resultierende erhöhte Hüftkontaktkraft berücksichtigt werden. Langzeitergebnisse sind daher abzuwarten. In der Umfrage zeigte sich, dass überhöhte Inlays überwiegend bei Anwendung eines hinteren Zugangs eingesetzt werden, jedoch überwiegend die biomechanisch ungünstigere Positionierung der Überhöhung im posterior-superioren Quadranten genutzt wird. Bei Verwendung eines überhöhten Inlays sollte die posterior-inferiore Position der Überhöhung beim hinteren Zugang genutzt werden.