Femoral Stem Design Research Articles

Influence of proximal femoral morphology on osteointegration of the AMIS uncemented femoral stem in modern hip arthroplasty

BackgroundIndications for total hip arthroplasty (THA) have evolved over recent decades, with a growing trend toward operating on younger and more active patients. With this shift in patient demographics, there has been a change in femoral stem designs and proximal femoral morphology encountered. This study aimed to evaluate the potential correlation between femoral stem osteointegration and proximal femoral morphology using the Dorr and Noble classifications.Materials and methodsWe conducted a retrospective review of 122 uncemented femoral stems (AMIstem Medacta, triple tapered). The demographic data analyzed included sex, age, stem size, and surgical indications. Preoperative radiographs were reviewed to determine the Dorr classification as well as the canal-to-calcar isthmus ratio, cortical index, and canal flare index. Postoperative radiographs were carefully reviewed to identify the presence of potential postoperative radiolucencies. Inter- and intra-observer agreements for these parameters were also analyzed.ResultsSignificant radiolucencies (> 2 mm) were found in 19.5% of the patients. Of all the variables analyzed, the cortical index was the only parameter significantly associated with the appearance of clinically significant radiolucency, with a threshold value of 0.62.ConclusionsThe appearance of radiolucencies is multi-factorial. Nevertheless, in this study, a high cortical index (> 0.62), representing the champagne flute morphology, was found to be associated with the development of significant radiolucencies.

Optimization Design and SLM Manufacturing of Porous Titanium Alloy Femoral Stem.

In order to solve the loosening problem caused by stress shielding of femoral stem prostheses in clinical practice, an optimization design method of a personalized porous titanium alloy femoral stem is proposed. According to the stress characteristics of the femur, the porous unit cell structures (TO-C, TO-T, TO-B) under three different loads of compression, torsion, and bending were designed by topology optimization. The mechanical properties and permeability of different structures were studied. Combined with the porous structure optimization, a personalized radial gradient porous titanium alloy femoral stem was designed and manufactured by selective laser melting (SLM) technology. The results show that the TO-B structure has the best comprehensive performance among the three topologically optimized porous types, which is suitable for the porous filling structure of the femoral stem, and the SLM-formed porous femoral stem has good quality. The feasibility of the personalized design and manufacture of porous titanium alloy implants is verified, which can provide a theoretical basis for the optimal design of implants in different parts.

Does Femoral Stem Design Influence Periprosthetic Fracture Incidence and Morphology in Total Hip Arthroplasty?

BackgroundAs the incidence of total hip arthroplasty (THA) increases, the number of periprosthetic femur fractures (PFF) will also rise. The surgical approach and stem design have been shown to influence the rate of PFF. This study evaluated PFF in cementless THA done through the posterior approach and described how stem design influences intraoperative and early postoperative fracture incidence and morphology. MethodsA retrospective review of 3,183 primary THAs for osteoarthritis from 2013 to 2021 was performed. Demographics, comorbidities, femoral stem designs, intraoperative and early postoperative PFFs (< 90 days), and aseptic femoral revisions were recorded. Stems were classified as single-wedge taper (Type 1), double-wedge taper (Type 2), or ream and broach (Type 3). There were 1,192 Type 1, 240 Type 2, and 1,726 Type 3 femoral stems. The PFF and aseptic femoral revisions were compared with univariable and multivariable analyses. Cox regression and Kaplan-Meier analyses evaluated survival to femoral revision. ResultsIn this population, 25 patients (0.8%) had an intraoperative or early postoperative PFF. Patients who had PFFs were older (68 versus 63; P = 0.03) and more likely to be women (76 versus 24%; P = 0.02). Type 2 stems had a significantly higher incidence of all-cause PFFs when compared to Type 1 (3.6 versus 0.7%; P < 0.01) and Type 3 (3.6 versus 0.4%; P < 0.01) stems. Type 2 stems also had a higher incidence of Vancouver B2 PFFs when compared to Type 3 stems (0.8 versus 0.05%; P = 0.04). Stem design was not associated with PFF or all-cause femoral revision. There were no differences in survival to femoral revision. ConclusionDouble-wedge taper stems may be associated with increased intraoperative and early postoperative PFFs, including those requiring femoral stem revision. However, there was no statistically significant difference in late PFF, aseptic loosening, or femoral revision.

Biomechanical Comparison of Impaction Techniques and Cross-Sectional Femoral Stem Shapes for Cementless Total Hip Arthroplasty.

Traditional mallet broaching and stem seating in cementless total hip arthroplasty (THA) can result in femoral stem misalignment, potentially reducing implant longevity. This study aimed to compare the pullout strength of cementless THA femoral stems with different cross-sectional designs achieved through the powered impactor method versus the traditional mallet method. The authors utilized 24 polyurethane foam femurs and two femoral bone preservation stems with different proximal cross-sectional shapes (double taper: ACTIS®, size 5; flat taper: TRI-LOCK®, size 5). A single orthopedic surgeon broached each femur from size 0 to size 5 using either the powered impactor or mallet impaction methods. Broaching time and component implantation times were recorded. A load-to-failure pullout strength test was conducted, and the ultimate pullout load was recorded. The broaching time for the TRI-LOCK® stem showed a statistically significant difference between the two impaction methods (powered: 37±7 seconds, mallet: 75±29 seconds, F[3, 20] = 4.56, p = 0.002), but no statistically significant difference was detected for the ACTIS® stem between the two impaction methods (powered: 47±22 seconds, mallet: 59±9 seconds, F[3, 20] = 4.56, p = 0.304). There was a statistically significant difference in pullout strength between the two impaction groups, and this strength was influenced by the implant cross-sectional shape (ACTIS®: 774±75N versus 679±22N, F(3,20) = 16.38, p = 0.018; TRI-LOCK®: 616±57N versus 859±85N, F(3, 20) = 16.38, p <0.001). The technique used for femoral bone preparation (powered impactor versus mallet) and the cross-sectional design of the cementless femoral stem are crucial factors that affect initial stem stability and operation time.

Cemented Stem Design in Total Hip Arthroplasty: Fixation Philosophies, Biomechanics, and an Updated Classification System.

There is renewed interest in cemented femoral fixation in total hip arthroplasty in the United States, and to fully appreciate the evolution of cemented femoral stem designs, an understanding of their history and design rationale is essential. To adequately study the outcomes of modern-day designs, a comprehensive classification system is also necessary. The biomechanical principles, failure mechanisms, and clinical outcomes associated with various cemented femoral stems are described in this comprehensive review. In addition, an updated version of an existing classification system is described that incorporates the primary design characteristics which differentiate implants currently in use. In this classification, implants are categorized as taper-slip (Type I), which are subdivided by Anatomic (IA), Double-Taper (IB), and Triple-Taper (IC) with subclassification for Traditional and Line-to-Line implants. Composite beam (Type II) implants are similarly divided into Anatomic (IIA), Straight (IIB), and Wedge (IIC) with subclassification for Polished, Satin, or Roughened finish. This classification system provides a basis for comparing cemented femoral stems, thereby improving our understanding of the effect of design characteristics on survivorship to guide future advancements and improve clinical outcomes.

Do all short stem types restore biomechanical parameters of the hip? Comparison according to femoral neck osteotomy levels.

There is no consensus on ideal short femoral stem design. A classification system proposed by Feyen and Shimmin divides short stems in two types according to femoral neck osteotomy levels: subcapital (IIIA) and standard (IIIB). The study aims to determine which design type is more successful in restoring native biomechanical parameters and whether stem type has an impact on clinical results. In this retrospective comparative study, patients that have undergone short stem hip arthroplasty were evaluated according to stem types: type IIIA (n = 52, 66.7%) (Mathys Optimys) and IIIB (n = 26, 33.3%) (Implantcast Aida and Smith & Nephew SMF). Pelvis X-rays were assessed in terms of femoral neck length, horizontal and vertical hip centres of rotation, horizontal and vertical femoral offsets, abductor lever arm lengths, leg lengths, and stem-shaft angles. Improvement in Harris hip scores, differences between post-operative and pre-operative measurements, and stem-shaft angles were evaluated and compared between two groups. Mean femoral neck resection (8.27 ± 6.68mm in IIIA and 15 ± 6.33mm in IIIB) was significantly different between both groups (p < 0.001). Harris hip scores were increased at post-operative six months in both groups with no difference (84.4 ± 6.4 and 84.6 ± 5.5, p = 0.4). The absolute values of differences between pre-operative and post-operative horizontal centres of rotation (p = 0.63), vertical centers of rotation (p = 0.75), horizontal femoral offsets (p = 0.78), vertical femoral offsets (p = 0.83), abductor lever arm distances (p = 0.63), and leg length (p = 0.21) measurements were not different between both groups. Stem positions were both varus with no statistically significant difference between groups (p = 0.14). We found no difference regarding restoration of biomechanical parameters between short stem designs with different levels of neck osteotomy. Additionally, short stem can mostly result in varus component positioning regardless of the level of neck osteotomy.

Cemented femoral stem design and postoperative periprosthetic fracture risk following total hip arthroplasty.

Polished taper-slip (PTS) cemented stems have an excellent clinical track record and are the most common stem type used in primary total hip arthroplasty (THA) in the UK. Due to low rates of aseptic loosening, they have largely replaced more traditional composite beam (CB) cemented stems. However, there is now emerging evidence from multiple joint registries that PTS stems are associated with higher rates of postoperative periprosthetic femoral fracture (PFF) compared to their CB stem counterparts. The risk of both intraoperative and postoperative PFF remains greater with uncemented stems compared to either of these cemented stem subtypes. PFF continues to be a devastating complication following primary THA and is associated with high complication and mortality rates. Recent efforts have focused on identifying implant-related risk factors for PFF in order to guide preventative strategies, and therefore the purpose of this article is to present the current evidence on the effect of cemented femoral stem design on the risk of PFF.

Biomechanical analysis of different THA cementless femoral stem designs in physiological and osteoporotic bone during static loading conditions.

The influence of THA stem design on periprosthetic femoral fractures (PFFs) risk is subject of debate. This study aims to compare the effects of different cementless stem designs on stress-strain distributions in both physiological and osteoporotic femur under various loading conditions. A biomechanical study using finite-element analysis was conducted. Four models were developed: three with implanted femurs and a native one chosen as control. Each model was analyzed for both healthy and osteoporotic bone. The following stem designs were examined: short anatomical stem with femoral neck preservation, double-wedge stem, and anatomical standard stem. Three loading conditions were assessed: gait, sideways falling, and four-point bending. During gait in physiological bone, the anatomical stem and the short anatomical stem with femoral neck preservation showed stress distribution similar to the native model. The double-wedge stem reduced stress in the proximal area but concentrated it in the meta-diaphysis. In osteoporotic bone, the double-wedge stem design increased average stress by up to 10%. During sideways falling, the double-wedge stem exhibited higher stresses in osteoporotic bone. No significant differences in average stress were found in any of the studied models during four-point bending. In physiological bone, anatomical stems demonstrated stress distribution comparable to the native model. The double-wedge stem showed uneven stress distribution, which may contribute to long-term stress shielding. In the case of osteoporotic bone, the double-wedge stem design resulted in a significant increase in average stress during both gait and sideways falling, potentially indicating a higher theoretical risk of PFF.

Pre-clinical characterization of a novel flexible surface stem design for total knee replacements.

Primary stability is crucial for implant osseointegration and the long-term stability of cementless total joint replacements. Biomechanical studies have shown the potential of femoral stems for total knee replacements to reduce micromotions at the bone-implant interface. However, approaches such as focusing on the structural elasticity of the femoral stems are rarely described. Three groups with different femoral stem designs were investigated: group 1: flexible surface stem, group 2: flexible surface stem with open-porous structured lamellas, and group 3: solid stem (reference). The stems were implanted into bone substitute material and dynamically loaded for 1000 cycles. Relative movement and subsidence were measured optically, and axial pull-out forces were determined after dynamic testing. Relative movements increased to 0.10 mm (groups 1 and 2) compared to 0.03 mm (group 3). Subsidence increased to 0.08 mm (group 1) and 0.11 mm (group 2) compared to 0.06 mm (group 3). For each group, subsidence mainly occurred during the first 500 cycles. A similar convergence was observed in the further course. Pull-out forces increased to 1815.0 N (group 1) and 1347.1 N (group 2) compared to 1306.4 N (group 3). The flexible surface stem design resulted in higher relative movements and subsidence, but also exhibited increased pull-out forces. The relative movements were below the critical limit of 0.15 mm and represent a superposition of the elastic deformations of the interacting implant components as well as the micromotion at the bone-implant interface. Therefore, the novel flexible surface stem design appears to offer promising primary implant fixation.

Impact of Zweymüller Stem Modification on Clinical and Radiological Outcomes

Background. According to the analysis of large arthroplasty registers we have noted the increase in the use of non-cemented implants, because the latter shows the same results of implant survival as well as cemented implants. On the other hand, they can affect the quality of the bone around the implant in different ways. These components differ in shape, length, and surface properties. According to the analysis of the arthroplasty register of the Vreden National Medical Research Center of Traumatology and Orthopedics, a significant decrease of the Alloclassic femoral stem using can be noted. In parallel the use of its SL-PLUS MIA modification has increased significantly.&#x0D; Aims of the study: 1) to determine the influence of changes in the design of the Zweymller-type femoral stem on midterm and long-term outcomes and its survival; 2) to identify the characteristics of adaptive remodeling of periprosthetic bone tissue around these femoral stems; 3) to determine risk factors for aseptic loosening of these femoral stems.&#x0D; Methods. 492 cases of hip arthroplasty using the Alloclassic and SL-PLUS MIA femoral stems were observed, with an average follow-up 78.6 months. The patients were divided into 2 groups according to the type of femoral stem. The assessment the hip articulation condition was carried out using the HHS and OHS. The intensity of the pain syndrome was assessed by VAS, and the level of patients satisfaction. The dynamic analysis of X-rays was also performed visually.&#x0D; Results. A significant improvement in clinical and functional results was observed according to the HHS and OHS in both groups of patients, regardless of the type of femoral stem. Analysis of X-rays over time showed differences in the behavior of these two femoral component models. The radiolucent lines around the femoral stem are absent in SL-PLUS MIA group, in Alloclassic stem group radiolucent lines are present even at a minimal period (12 months). We also found that a tight fit of Zweymller femoral stems in the distal shaft is a risk factor for severe stress-shielding syndrome, especially in the funnel channels. But ceteris paribus, a distal tight fit of SL-PLUS MIA stems despite similar geometry of the distal part does not lead to such frequent manifestation of severe stress shielding.&#x0D; Conclusion. The change in Zweymller stem design from Alloclassic to SL-PLUS MIA improved the nature of adaptive remodeling in the periprosthetic area of the femur. It may improve the long-term results of primary hip arthroplasty, but these differences require closer observation.

EVALUATION OF PROXIMAL FEMORAL BONE MINERAL DENSITY IN CEMENTLESS TOTAL HIP ARTHROPLASTY: A THREE-ARM PROSPECTIVE RANDOMIZED CONTROLLED TRIAL

Femoral stem design affects periprosthetic bone mineral density (BMD), which may impact long term survival of cementless implants in total hip arthroplasty (THA). The aim of this study was to examine proximal femoral BMD in three morphologically different uncemented femoral stems designs to investigate whether one particular design resulted in improved preservation of BMD.119 patients were randomized to receive either a proximally coated dual taper wedge stem, a proximally coated anatomic stem or a fully coated collarless triple tapered stem. Dual energy x-ray absorptiometry scans (Lunar iDXA, GE Healthcare, Madison, WI) assessed BMD across the seven Gruen zones pre-operatively, and post-operatively at 6-weeks, 1-year, and 2-years comparing the unoperated contralateral femur as a control.BMD increased in zones one (2.5%), two (17.1%), three (13.0%), five (10%) and six (17.9%) for all stems. Greater preservation of BMD was measured on the lateral cortex (zone 2) for both the dual taper wedge and anatomic stems (p = 0.019). The dual taper wedge stem also demonstrated preservation of BMD in the medial calcar (zone 7) whilst the anatomic and triple taper stem declined in this region, however this was not statistically significant (p = 0.059). BMD decreased on average by 2.1% in the mid-diaphysis region, distal to the stem tip (zone 4) for all implants. All stems performed equivalently at final follow-up in all patient reported outcome measures.Implant design was shown to impact BMD changes. All stems preserved bone at the metaphyseal level in early follow-up, which theoretically indicates favorable implant fixation. There was no significant stress shielding observed, however longer follow-up is required to elucidate the impact of this finding on implant survivorship.

PERIPROSTHETIC FRACTURE RATES USING COLLARED STEMS IN UNCEMENTED PRIMARY TOTAL HIP ARTHROPLASTY WITH A POSTERIOR APPROACH

Periprosthetic femur fracture (PFF) is a major complication following total hip arthroplasty (THA) that carries significant morbidity, mortality, and economic burden. Currently, uncemented stems are highly preferred in primary THA, but have been associated with higher risk of PFF compared to cemented stems. The use of collared stems in uncemented primary THA has shown promise in reducing PFF rates postoperatively.This retrospective study included 2,294 uncemented primary THAs using the posterior approach performed by two attending surgeons from January 2016 to December 2022. Both surgeons switched from a collarless femoral stem design to a collared design in May 2020. Data was collected regarding stem design, frequency of PFF, and requirement for revision surgery. Periprosthetic fractures were identified and confirmed using medical records and/or radiographic imaging. Fracture rates and percentages between collared and collarless stems were then analyzed. A Fisher's Exact Test was performed to determine if there was a significant association between collared and collarless stem use on PFF rates.A total of 2,294 uncemented primary THAs performed by 2 surgeons were eligible for analysis. 903 (39.4%) patients received a collared stem, and 1,391 (60.6%) patients received a collarless stem. In total, 14 (0.6%) PFFs occurred over the study period. There was 1 fracture (0.1%) out of 903 collared stems, and 13 fractures (0.9%) out of 1,391 collarless stems (p = 0.012).Collared stems were associated with a significant decrease in PFF rate when compared to collarless stems in uncemented primary THA. Future studies are encouraged to continue to investigate PFF and other complication rates with the use of a collared stem design.

Design of titanium uncemented femoral stems for hip prosthesis suitable for the Colombian young adult population

The increase of revision surgeries in hip replacement procedure in Colombian young adult population can be addressed by a new design of femoral stem that reduces stress shielding. A new femoral stem was designed using topology optimization as a design aid to reduce the mass in the femoral stem and its overall stiffness, combined with the theoretical, computational, and experimental assessment of the new design that complies with a static and fatigue safety factor greater than one. The new femoral stem design can be used as a design tool to reduce the number of revision surgeries caused by stress shielding.

Experiences and results with a cementless femoral stem design: SL-PLUS MIA

Experiences and results with a cementless femoral stem design: SL-PLUS MIA

EVALUATION OF PROXIMAL FEMORAL BONE MINERAL DENSITY IN CEMENTLESS TOTAL HIP ARTHROPLASTY: A THREE-ARM PROSPECTIVE RANDOMIZED CONTROL TRIAL

Femoral stem design affects periprosthetic bone mineral density (BMD), which may impact long term survival of cementless implants in total hip arthroplasty (THA). The aim of this study was to examine proximal femoral BMD in three morphologically different uncemented femoral stems designs to investigate whether one particular design resulted in improved preservation of BMDMethods: 119 patients were randomised to receive either a proximally coated dual taper wedge stem, a proximally coated anatomic stem or a fully coated collarless triple tapered stem. All surgeries were performed via the posterior approach with mobilization on the day of surgery. Dual energy x-ray absorptiometry scans (Lunar iDXA, GE Healthcare, Madison, WI) assessed BMD across the seven Gruen zones pre-operatively, and post-operatively at 6-weeks, 1-year, and 2-years and compared to the unoperated contralateral femur as a control. Patient reported outcome measures of pain, function and health were also included at these corresponding follow-ups.BMD increased in zones one (2.5%), two (17.1%), three (13.0%), five (10%) and six (17.9%) for all stems. Greater preservation of BMD was measured on the lateral cortex (zone 2) for both the dual taper wedge and anatomic stems (p = 0.019). The dual taper wedge stem also demonstrated preservation of BMD in the medial calcar (zone 7) whilst the anatomic and triple taper stem declined in this region, however this was not statistically significant (p = 0.059). BMD decreased on average by 2.1% inthe mid-diaphysis region, distal to the stem tip (zone 4) for all implants. All stems performed equivalently at final follow-up in all patient reported outcome measures.This study demonstrated maintenance of femoral BMD in three different cementless femoral stem designs, with all achieving excellent improvements in patient reported outcomes. There was no significant stress shielding observed, however longer follow-up is required to elucidate the impact of this finding on implant survivorship.

Capability of auxetic femoral stems to reduce stress shielding after total hip arthroplasty.

Stress shielding​(SS) is considered the main mechanical cause of femoral stem loosening after total hip arthroplasty (THA). This study introduces an auxetic lattice femoral stem structure with negative Poisson's ratio that can expand laterally, with the intent of transferring more load to surrounding bone and thereby reducing SS. This study aims to evaluate how the geometry profile of different femoral stems with auxetic structures affects the level of SS. Different re-entrant angles for the auxetic unit cells were also evaluated. This study assessed three commercial femoral stem designs (Mayo, CLS and Fitmore) and three re-entrant angles for the auxetic structures (60°, 70° and 80°). Nine auxetic femoral stems (three M-type, three C-type and three F-type) and three solid femoral stems (control group) were designed. All femoral stems were implanted into a finite element model of the human femur to compare levels of SS between the auxetic stems and their traditional solid counterparts. The results showed that incorporating an auxetic structure into the stem design caused less SS of the surrounding bone than the control models. The M-type stems had the lowest level of SS, followed by the C-type and F-type stems. A re-entrant angle of 70° for the M-type stem, 80° for the C-type stem and 60° for the F-type stem were the designs most capable of reducing SS. This study found that femoral stems with an auxetic lattice structure caused less SS after THA than comparable solid femoral stems. A femoral stem based on the M-type geometry profile is recommended when designing auxetic femoral stems to minimize SS of surrounding bone. The novel solution provided in this study may serve to increase the survival rate of femoral stems by reducing SS after THA.

Corrélation entre l’utilisation d’une tige remplissante et le syndrome d’implantation du ciment chez les personnes âgées ostéoporotiques souffrant d’une fracture du col du fémur traitée par arthroplastie de hanche cimentée : une étude cas-témoin rétrospective chez 128 patients

BackgroundBone cement implantation syndrome (BCIS) is a serious and potentially fatal complication especially in patients with osteoporotic femoral neck fracture (OFNF) undergoing cemented hip arthroplasty (CHA). Recent studies showed that the shape-closed femoral stem profile could lead to a significant increase of the intramedullary pressure during cementation and prosthesis insertion. This study aimed to 1) correlate the use of shaped-closed femoral stem and other perioperative risk factors with severe grade of BCIS (grade 2 or 3: BCIS gr2/3, and 2) identify the prevalence of BCIS in the elderly patients with OFNF and treated with CHA. HypothesisLarge wedge-shaped (or “shape-closed”) femoral stem design would significantly associate with BCIS gr2/3 in the elderly patients who sustained OFNF and underwent CHA. Patients and methodsA total of 128 OFNF patients, who aged over 75 years and underwent CHA were retrospectively reviewed and then allocated into 2 groups: SC Group (use shape-closed femoral stem, n=40) and FC Group (use force-closed femoral stem, n=88). BCIS was grading in all patients according to Donaldson classification. Perioperative data between the patients with BCIS-gr2/3 and those with BCIS grade 0 or 1 (BCIS-gr0/1) were compared. Multiple logistic regression analysis was used to identify predictive factors for BCIS-gr2/3. ResultsThe prevalence of overall BCIS and BCIS-gr2/3 was 32.8 % (n=42) and 6.2 % (n=8), respectively. The total in-hospital and 1-year mortality rates were 2.3 % and 4.7 %, respectively. The major perioperative complication in patients with BCIS-gr2/3 was significantly higher compared to those in patients with BCIS-gr0/1 (62.5 % vs. 10.0 %, p=0.001). Multivariate analysis showed that age >90 years (OR 9.4, 95 % CI: 1.4-62.9, p=0.02), preinjury Parker mobility score <4 (OR=48.8; 95 % 2.7-897.2, p=0.008) and shape-closed femoral stem used (OR=19.1; 95 %CI, 1.8–204.5, p=0.01) were the significant independent predictors for BCIS-gr2/3 in these patients. ConclusionBCIS in OFNF patients undergoing CHA is common and associates with a high major perioperative complication rate. Our initial hypothesis is validated as the patients at risk for BCIS-gr2/3 are those whose CHA procedures use a shape-closed femoral stem design and with extreme age, and having poor preinjury ambulatory status. Therefore, we recommended using cementless stem as the first option in OFNF. However, if CHA is needed, strict guideline for cement insertion should be followed with force-closed stem application to avoid the risk of BCIS-gr2/3. Level of evidenceIII; Retrospective case-control study.

Single Wedge Femoral Stem Designs are Associated With a Higher Risk for Revision After Cementless Primary Total Hip Arthroplasty

BackgroundCementless total hip arthroplasty (THA) femoral stems are the most commonly selected prostheses in the United States. Optimal stem geometry remains controversial with excellent survivorship reported for many designs. We compared cause-specific stem revision of single-wedge versus double-wedge designs from a multicenter US cohort. MethodsData from an integrated healthcare network’s total joint replacement registry were used to conduct a cohort study. Primary elective cementless THAs were identified (2001 to 2018). Implant exposure groups were classified by design geometry using the system proposed by Khanuja et al. Type 1 single-wedge (n = 11,082) and type 2 double-wedge (n = 32,380) designs were compared, and other design types were excluded; the final study cohort comprised 43,462 THAs. Cause-specific multivariable Cox regressions were used to evaluate risk for revision due to infection or aseptic reasons, including loosening, instability, periprosthetic fracture, or other reasons. ResultsAfter adjustment for covariates, a higher aseptic revision risk was observed for type 1 when compared to type 2 designs (hazard ratio = 1.91, 95% confidence interval = 1.33-2.75). When looking at specific revision reasons, revision for aseptic loosening (hazard ratio = 3.46, 95% confidence interval = 2.24-5.34) was higher for type 1 versus type 2 designs. No differences were found for septic revision, instability, periprosthetic fracture, or revisions for other reasons. ConclusionsType 1 single-wedge designs were found to have a higher risk of revision due to aseptic loosening relative to type 2 double-wedge designs. Femoral stem geometry should be considered when selecting a cementless femoral implant. Level of EvidenceLevel III.

Hip Arthroplasty Femoral Stem Designs and Their Association With Early Postoperative Periprosthetic Femoral Fractures

BackgroundPeriprosthetic femoral fractures (PFFs) in total hip arthroplasty (THA), especially those in contact with the diaphyseal stem, carry high morbidity. This study evaluated how stem design influences the risk of early Vancouver B PFF or other PFF requiring operative intervention after THA. MethodsA multicenter, retrospective study of 3,433 primary cementless THAs performed from 2014 to 2021 included 2,302 single-taper (micro M/L [n = 1,169]; M/L [n = 1,133]) and 1,131 double-taper (fit-and-fill [n = 420]; compaction-collared [n = 711]) stems. Mean follow-up was 2.2 years (range, 0.3 to 6.5 years). Primary outcomes were Vancouver B and surgically treated postoperative PFFs among differing femoral stems. Secondary outcomes included rates of intraoperative and postoperative Vancouver A and C PFFs. ResultsForty five postoperative PFFs (1.3%) occurred within 8.8 weeks (median), 25 of which were Vancouver B (0.7%) and 20 total PFFs that required operative intervention (0.6%). Compaction-collared stems had a decreased risk of Vancouver B (hazard ratio 0.18, 95% confidence interval: 0.03-0.97 P = .044) and any surgically treated PFF (hazard ratio 0.10, 95% confidence interval: 0.01-0.95; P = .037). Intraoperative PFFs were most common with fit-and-fill stems (3.6%, P < .001) and Vancouver A with compaction-collared stems (1.8%, P < .001). The cohort with PFF had a higher Charlson comorbidity index (P = .004), more women (P = .001), more Dorr A or C femora (P = .013), and more posterior or lateral surgical approaches compared to those without PFF (P ≤ .001). ConclusionAfter controlling for confounding variables, compaction-collared stems had a significantly lower risk of postoperative Vancouver B and PFF requiring operative treatment than single-taper and double-taper stems.

Digital Templating of THA Using PACS and an iPhone or iPad is as Accurate as Commercial Digital Templating Software.

Digital templating is a standard preoperative planning method in THA. Unfortunately, many hospitals cannot afford the software or have accessibility barriers owing to a limited number of installed computer workstations. We created a templating method using a picture archiving and communication system and the Keynote program on a mobile phone. The method's accuracy and reliability have not been compared with those of commercial digital templating software. (1) How accurate is this novel method on iPhone and iPad mobile devices compared with a commercially available digital templating software program? (2) Is the method reproducible among users with different levels of experience? (3) Are the results similar for different types of femoral prostheses? Between January 2017 and May 2020, we treated 209 patients for hip disease or trauma with primary cementless THA. We considered patients with a normal contralateral hip as potentially eligible for this retrospective study. Thus, 91% (191 of 209 hips) were eligible; a further 13% (27 hips) were excluded because of postoperative leg length discrepancy > 5 mm, femoral offset discrepancy > 5 mm (9% [18 hips]), intraoperative periprosthetic fracture (4% [eight hips]), and proximal femoral deformity (0.5% [one hip]), leaving 78% (164 hips) for analysis here. Their preoperative radiographs were evaluated by three independent assessors, including one senior orthopaedic surgeon, one senior resident, and one junior resident, using three methods. The first was digital templating using OrthoView software, which is a commercially available digital templating software program used worldwide and known to possess high accuracy. The other two methods were technically similar to one another, with the only difference being the interface: iPhone versus iPad. In both of those approaches, using the picture archiving and communication system measurement tool, we drew a circle on an acetabular radiograph to depict the cup. We took a photograph of the computer display and imported the photograph into slides of the Keynote program, a presentation software application for Mac computers, on both devices. It was then underlaid on transparent digital templates of the femoral stem, which were scanned from plastic templates and positioned at the center of each slide. We scaled the image to the template by adjusting the image size until a 15-cm straight line on the hip photograph was equal to the 15-cm scale markers of the template. All templating results were compared with the actual implanted cementless THA components to assess accuracy. All assessors were blinded to the information about the actual implants, and they were not involved in performing the surgical procedures. The intrarater and interrater reliabilities were analyzed using intraclass correlation coefficients and kappa values. The accuracy for predicting stem size for each type of the four stem designs was compared among the three methods. We were able to predict the acetabular cup size within one size in 92% of hips (151 of 164) using OrthoView and in 92% (150 of 164) using the novel method (p > 0.99). The accuracies of the three methods were comparable for predicting a femoral stem size within one size (OrthoView: 90% [148 hips], iPhone: 93% [152 hips], and iPad: 91% [149 hips]; p = 0.78), and neck length (OrthoView: 96% [157 hips], iPhone: 96% [158 hips], and iPad: 97% [159 hips]; p = 0.95). Using OrthoView, the neck offset was correctly predicted in 80% (132 hips), compared to 85% (139 hips) when using the iPhone and 82% (134 hips) when using the iPad (p = 0.57). All methods showed substantial or excellent agreement regarding intrarater and interrater reliability. There was no difference in accuracy regarding any of the four femoral stem designs we evaluated (Avenir, Excia, ML taper, and Metha). The digital templating technique for THA using an iPhone or iPad combined with a picture archiving and communication system demonstrated high accuracy, comparable to that of commercial digital templating software. This technique is reliable and reproducible for predicting a cementless prosthesis size, neck length, and offset in different types of femoral stems. It may be useful as an alternative in resource-constrained centers where commercial software programs are too expensive to be used in practice. Level IV, diagnostic study.