Femoral Size Research Articles

Potential for femoral size optimization for off-the-shelf implants: A CT derived implant database analysis.

In total knee arthroplasty, the femoral implant size is chosen mainly based on the femoral anteroposterior (AP) height and mediolateral (ML) width. This choice often is a compromise, due to limited size availability. Inadequate AP fit is expected to alter flexion laxity and thus knee function. Inadequate ML fit entails underhang or overhang, which is linked to worse clinical outcomes. Hence, we aimed to find implant size distributions, which maximize population coverage, and to evaluate the sensitivity regarding error bounds and the number of implant sizes for a database of 85,143 cases. All patients in the database have been provided with a patient-specific implant in the past. For a subset of 1049 cases, three-dimensional preoperative bone surface models were available. These were used to validate whether the implant dimensions were representative of the bone dimensions. Particle Swarm Optimization was used for optimizing the implant size distribution. The deviations between implant and bone measures in the subset were found to be clinically irrelevant. Therefore, the full database of 85,143 cases was used for further analyses. A higher sensitivity of the population coverage regarding the error bounds compared to the number of implant sizes was found. For an exemplary setup of 12 optimized implant sizes and error bounds of ±1.5 mm for AP and ±3 mm for ML, a population coverage of almost 85% was achieved. In contrast, even with 30 implant sizes, a full population coverage could not be reached. Hence, remaining cases should be provided with patient-specific implants.

Registration of Bony Landmarks and Soft Tissue Laxity during Robotic Total Knee Arthroplasty is Highly Reproducible.

There is growing interest and enthusiasm for robotic total knee arthroplasty (TKA). Many robotic systems require registration of bony landmarks as well as a dynamic soft tissue evaluation to plan femoral and tibial resections. Variability in this user-driven registration can introduce error and undermine the purported precision and accuracy offered by robotics. The purpose of this study was to evaluate inter- and intrarater reliability in robotic registration with a new robotic system (ROSA®; Zimmer-Biomet, Warsaw, IN). Two unpaired cadaveric knee specimens were exposed, and optical arrays were placed into the femur and tibia. Three separate evaluators conducted repeated trials of anatomic registration and assessment of soft tissue laxity, as well as coronal alignment, sagittal alignment, femoral size, and maximum opening in the medial and lateral compartments in both flexion and extension. Repeated trials were conducted using these specimens with and without preoperative imaging for landmarking (image-based and image-free workflows). An Intraclass Correlation Coefficient (ICC) was calculated for each observer and across observers to determine intra-and interrater reliability, respectively, in robotic registration. There was good to excellent reliability for all conditions, and all correlation coefficients were >0.767. On average, ICCs for intrarater reliability were excellent for Doctor 1 (0.952), Doctor 2 (0.975), and Doctor 3 (0.925). On average, the ICCs for interrater reliability were excellent for both the "Registration + Gap Assessment" condition (0.961) and the "Gap Assessment" condition (0.994). Our results show a high repeatability of registration of anatomic landmarks and gap assessment among observers using this robotic system for both image-based and image-free software.

The Reliability of Preoperative Total Knee Arthroplasty Planning -a Comparison of Two Calibration Markers.

Preoperative templating is the gold standard in planning elective total knee arthroplasty. This retrospective study analyses preoperative templating by using two different calibration devices. Preoperative radiographic templating with TraumaCad using two different calibration devices was performed in 231 patients. Overall, 60.6% (n=140) did not match and 39.4% (n=91) matched for tibial as well as femoral size. Group I showed significantly more combined matches as well as for just the size of the femoral component. In this study, the KingMark calibration should be preferred to standardised ball markers.

A comparison of osteoarticular allografts and allograft-prosthesis composites for reconstruction of the distal femur after resection of a bone tumour in childhood : a retrospective study.

Osteoarticular reconstruction of the distal femur in childhood has the advantage of preserving the tibial physis. However, due to the small size of the distal femur, matching the host bone with an osteoarticular allograft is challenging. In this study, we compared the outcomes and complications of a resurfaced allograft-prosthesis composite (rAPC) with those of an osteoarticular allograft to reconstruct the distal femur in children. A retrospective analysis of 33 skeletally immature children with a malignant tumour of the distal femur, who underwent resection and reconstruction with a rAPC (n = 15) or osteoarticular allograft (n = 18), was conducted. The median age of the patients was ten years (interquartile range (IQR) 9 to 11) in the osteoarticular allograft group and nine years (IQR 8 to 10) in the rAPC group (p = 0.781). The median follow-up of the patients was seven years (IQR 4 to 8) in the osteoarticular allograft group and six years (IQR 3 to 7) in the rAPC group (p = 0.483). Limb function was evaluated using the Musculoskeletal Tumor Society (MSTS) score. At final follow-up, the knee was unstable in 9/18 patients (50%) in the osteoarticular allograft group and 2/15 patients (13%) in the rAPC group (p = 0.026). The median range of motion (ROM) of the knee was 117° (IQR 115° to 120°) in the osteoarticular allograft group and 100° (IQR 95° to 105°) in the rAPC group (p < 0.001). The median MSTS score was 25 (IQR 23 to 26) in the osteoarticular allograft group and 28 (IQR 26 to 29) in the rAPC group (p = 0.007). Osteoarthritic change was detected in 11/18 patients (61%) in the osteoarticular allograft group and in 4/15 (26%) patients in the rAPC group (p = 0.048). In our series, a resurfaced allograft-prosthesis composite provided better knee stability and function, with a lower rate of osteoarthritis; an osteoarticular allograft was associated with better knee ROM.Cite this article: Bone Joint J2022;104-B(10):1174-1179.

Validation of an MRI Technique for the 6-DOF Knee Kinematics Measurement.

Background: For total knee arthroplasty (TKA), the optimal rotational position of the femoral component is felt to be critically important. The current knee joint kinematics measurement technology is unable to identify the exact rotation axis of the knee joint, the main reasons being low measurement accuracy and insufficient three-dimensional data (2D-3D image matching technology). In order to improve the effect of TKA surgery, we proposed a knee joint kinematics measurement method, based on the MRI technology, and verified its measurement accuracy. We then employed this method to identify the personalized optimal rotation axis of the knee joint for TKA patients. Purposes: The purpose of the study was 1) to propose a method for measuring knee joint kinematics and verify its accuracy and 2) to propose a method for determining the optimal rotation axis of knee joint for TKA surgery, based on accurate kinematic measurement results. Materials and Methods: The experiment was divided into two parts: in vitro and in vivo. The purpose of the in vitro experiment was to verify the measurement accuracy of our method. We fixed two aquarium stones (approximately 10cm * 10cm * 10cm in size, close to the size of the distal femur and proximal tibia) firmly on the fixed and moving arms of the goniometer/vernier caliper with glue and immersed the aquarium stones in the water to capture MRI images. The MRI images were then processed with MATLAB software, and the relative motion of the two aquarium stones was measured. The measurement accuracy of our method was verified via the scale reading of the moving arm on the goniometer/vernier caliper. In vivo, 36 healthy elderly participants (22 females, 14 males) were recruited from the local community; our method was then employed to measure the relative motion of the tibia and femur and to observe the rollback and screw home motion of the medial/lateral condyle of the femur, which was identified as specific kinematic features of the knee joint. Results: In vitro, all measurements were accurate to <1mm and <1°. In vivo, all knee measurements showed rollback motion (the rollback distance of the medial femoral condyle was 18.1 ± 3.7mm and that of the lateral condyle was 31.1 ± 7.3mm) and screw home motion. Conclusion: In the application scenario of knee joint kinematics measurement, our method has an accuracy of <1° of rotation angle and <1mm of translation for all reference points, and it can be employed to identify the most stable axis of the knee joint. Significance: Using our method to accumulate data on the knee rotation axis of more subjects to establish an average rotation axis of a given population may help in knee prosthesis design and reduce the patient dissatisfaction rate. Individually measuring the patient's rotation axis before TKA surgery and adjusting the prosthesis installation in TKA may further reduce the patient dissatisfaction rate, and automatic computer measurement may be realized in the future, but it is still time-consuming for now.

Cortical bone relationships are maintained regardless of sex and diet in a large population of LGXSM advanced intercross mice

IntroductionKnowledge of bone structure-function relationships in mice has been based on relatively small sample sets that limit generalizability. We sought to investigate structure-function relationships of long bones from a large population of genetically diverse mice. Therefore, we analyzed previously published data from the femur and radius of male and female mice from the F34 generation of the Large-by-Small advanced intercross line (LGXSM AI), which have over a two-fold continuous spread of bone and body sizes (Silva et al. 2019 JBMR). MethodsMorphological traits, mechanical properties, and estimated material properties were collected from the femur and radius from 1113 LGXSM AI adult mice (avg. age 25 wks). Males and females fed a low-fat or high-fat diet were evaluated to increase population variation. The data were analyzed using principal component analysis (PCA), Pearson's correlation, and multivariate linear regression. ResultsUsing PCA groupings and hierarchical clustering, we identified a reduced set of traits that span the population variation and are relatively independent of each other. These include three morphometry parameters (cortical area, medullary area, and length), two mechanical properties (ultimate force and post-yield displacement), and one material property (ultimate stress). When comparing traits of the femur to the radius, morphological traits are moderately well correlated (r2: 0.18–0.44) and independent of sex and diet. However, mechanical and material properties are weakly correlated or uncorrelated between the long bones. Ultimate force can be predicted from morphology with moderate accuracy for both long bones independent of variations due to genetics, sex, or diet; however, predictions miss up to 50 % of the variation in the population. Estimated material properties in the femur are moderately to strongly correlated with bone size parameters, while these correlations are very weak in the radius. DiscussionOur results indicate that variation in cortical bone phenotype in the F34 LGXSM AI mouse population can be adequately described by a reduced set of bone traits. These traits include cortical area, medullary area, bone length, ultimate force, post-yield displacement, and ultimate stress. The weak correlation of mechanical and material properties between the femur and radius indicates that the results from routine three-point bending tests of one long bone (e.g., femur) may not be generalizable to another long bone (e.g., radius). Additionally, these properties could not be fully predicted from bone morphology alone, confirming the importance of mechanical testing. Finally, material properties of the femur estimated based on beam theory equations showed a strong dependence on geometry that was not seen in the radius, suggesting that differences in femur size within a study may confound interpretation of estimated material properties.

Relative skull size evolution in Mesozoic archosauromorphs: potential drivers and morphological uniqueness of erythrosuchid archosauriforms

AbstractLittle is known about the large‐scale evolutionary patterns of skull size relative to body size, and the possible drivers behind these patterns, in Archosauromorpha. For example, the large skulls of erythrosuchids, a group of non‐archosaurian archosauromorphs from the Early and Middle Triassic, and of theropod dinosaurs are regarded as convergent adaptations for hypercarnivory. However, few investigations have explicitly tested whether erythrosuchid and theropod skulls are indeed disproportionately large for their body size, and whether this trend is driven by hypercarnivory. Here, we investigate archosauromorph relative skull size evolution, examining the scaling relationships between skull and body size of Palaeozoic and Mesozoic archosauromorphs using a robust phylogenetic framework and assessing the influence of potential drivers, such as taxonomy, diet, locomotory mode and inhabited biotope. Our results show that archosauromorph relative skull sizes are largely determined by phylogeny and that the other drivers have much weaker levels of influence. We find negative allometric scaling of skull size with respect to body size when all studied archosauromorphs are analysed. Within specific groups, skull size scales with positive allometry in non‐archosaurian archosauromorphs and, interestingly, scales isometrically in theropods. Ancestral reconstructions of skull–femur size ratio reveal a disproportionately large skull at the base of Erythrosuchidae and proportionately sized skulls at the bases of Theropoda, Carnosauria and Tyrannosauroidea. Relative skull sizes of erythrosuchids and theropods are therefore distinct from each other, indicating that disproportionately large skulls are not a prerequisite for hypercarnivory in archosauromorphs, and that erythrosuchids exhibit a bauplan unique among terrestrial Mesozoic carnivores.

Increased Accuracy in Templating for Total Knee Arthroplasty Using 3D Models Generated from Radiographs.

Templating prior to total hip arthroplasty is a widely adopted practice that aims to improve operative efficiency and reduce clinical outliers. Predicting implant size before total knee arthroplasty (TKA), although less common, could increase operating room efficiency by reducing necessary equipment needed for the procedure. This study compared templating accuracy in TKA using two-dimensional (2D) digital radiographs to a novel imaging technology that generates a three-dimensional (3D) model from these 2D radiographs. Two hundred and two robotic-assisted primary TKA surgical cases using Persona Knee System (Zimmer Biomet, Warsaw, IN) were retrospectively analyzed. For all cases, 3D templating was completed preoperatively using a novel radiographic image acquisition protocol. Using the same radiographs, the knee was templated using a 2D digital templating program. All surgeons were blinded to the final implant sizes, and all templating was done independently. The accuracy of predictions within ± 1 from the final implant size was determined for the femoral and tibial components. The accuracy (within 1 size) of tibial size predictions was comparable between attending surgeons and residents (87 vs. 82%, p = 0.08), but attending surgeons more accurately predicted the femoral size (77 vs. 60%, p < 0.05). The 2D to 3D imaging technology more accurately predicted both tibial and femoral sizes compared with the attending surgeons (99.5 vs. 87%, p < 0.05; 84% vs. 77%, p < 0.05). However, the imaging technology, attending surgeons, and residents were all more likely to overestimate femur size (p < 0.05). Moreover, the 3D imaging technology predicted the exact tibial component size in 93.1% of cases, which was significantly greater compared with residents (40%, p < 0.01) and attending surgeons (53%, p < 0.01). The 2D to 3D imaging technology more accurately predicted tibial and femoral component sizes compared with 2D digital templating done by surgeons. All templating predictions were more accurate for the tibial implant size than for the femoral size. The increased accuracy of implant size predictions from this 3D templating technology has the potential to improve intraoperative efficiency and minimize costs and surgical time.

Intermediate to Long-Term Outcomes and Causes of Aseptic Failure of an At-Risk Femoral Stem.

The Accolade TMZF is a tapered-wedge cementless metaphyseal-coated femoral stem that was widely utilized from 2002 to 2012. In recent years, there have been reports of early catastrophic failure of this implant. The purposes of the present study were to establish the long-term survival of this stem and to analyze patients who underwent aseptic revision to understand the causes and risk factors for failure. We retrospectively reviewed the records of all patients who had undergone primary total hip arthroplasty with use of an Accolade TMZF stem at a high-volume arthroplasty center. The causes and timing of revision surgery were documented. Survivorship analysis was performed with use of Kaplan-Meier curves to determine the overall and aseptic survival rates at the time of the latest follow-up. Patient and implant factors commonly associated with aseptic failure were extracted, and a Cox proportional hazards model was used. A consecutive series of 2,609 patients who had undergone unilateral primary total hip arthroplasty with use of an Accolade TMZF femoral stem were included. The mean time from the primary procedure was 11.3 years (range, 0 days to 19.4 years). The cumulative survival rate was 95.5% ± 0.1% at the time of the latest follow-up. One hundred and seven patients underwent revision surgery, with aseptic loosening of the femoral component being the most common cause of aseptic failure in this cohort (33 of 2,609; 1.3%). Smaller femoral size and larger femoral head offset were independent risk factors for aseptic failure. To our knowledge, this is the largest series representing the longest follow-up of this tapered-wedge cementless femoral implant. Despite early concerns, the Accolade TMZF stem had excellent survivorship in this cohort. Trunnionosis as the cause for revision surgery was rare. Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Long-Term Results of Kyocera Modular Limb Salvage System after Resection of Tumors in the Distal Part of the Femur: Report from Japanese Musculoskeletal Oncology Group Study.

Simple SummaryWe aimed to elucidate the long-term outcomes of a distal femur reconstruction system in 125 patients with bone and soft tissue tumors. Implant survival rates at 10 and 15 years were 58.5% and 39.4%. Stem breakage should be considered in patients with cementless and/or smaller femoral stem sizes. Aseptic loosening should be considered in patients with a cement system after 10 years.Background: The distal femur is a common site of bone tumors. After surgical resection, prosthetic replacement is a major reconstruction method. We aimed to elucidate the long-term outcomes of the Kyocera Modular Limb Salvage (KMLS) systems after resection of tumors in the distal part of the femur. Methods: Between 1998 and 2014, 125 patients were treated at 14 institutions. There were 59 males and 66 females, with a mean age of 35 years. The mean follow-up period was 132 months. Results: There had been 65 additional surgeries, including 56 revisions and 9 amputations: 15 for aseptic loosening, 14 for stem breakage, 13 for deep infection, 13 for rotator-hinge bushing failure, 5 for local recurrence, and 5 for others. Implant survival rates at 10 and 15 years were 58.5% and 39.4%. The cumulative incidence of 15-year revision for femoral stem breakage was 31.7% in patients with cementless fixation. The 15-year cumulative incidence of revision for aseptic loosening was 19.8% in patients with cement fixation. Conclusions: KMLS systems represent a reliable system with long-term results. Stem breakage should be considered in patients with cementless and/or smaller femoral stem sizes. Aseptic loosening should be considered in patients with cement systems after 10 years.

Late Access Site Complications Following Transfemoral Aortic Valve Implantation

Few data exist on late vascular complications (VCs) after transfemoral (TF) transcatheter aortic valve implantation (TAVI). The objective of this study was to evaluate the incidence and predictors of late access site VC after TF TAVI. A total of 128 patients (mean age: 80 ± 8 years, women: 52%) who underwent TF TAVI without major VC were included. A femoral US-Doppler evaluation was performed in all patients at a median of 5 (3 to 15) months after the procedure, and 76 patients (59.4%) also had a preprocedural ultrasound (US)-Doppler examination. The impact of baseline and procedural factors (including the use of simple 2 Proglides or complex additional Proglide or Angioseal device on top of the 2 Proglide technique, hemostasis techniques, and the use of balloon dilation for optimizing femoral hemostasis) were evaluated. The follow-up US-Doppler evaluation detected 2 asymptomatic VCs (1.6%), and 5 (3.9%) patients exhibited significant femoral stenosis (peak systolic velocity [PSV] ≥300 cm/s). Female gender (p <0.001) and smaller femoral diameter (p=0.045) were associated with higher femoral PSV values. In those patients who underwent a pre-TAVI femoral US-Doppler, the median PSV values after TAVI were higher compared with those obtained pre-TAVI (p <0.001), but similar results were found for the contralateral femoral arteries. A complex hemostasis technique or the use of balloon optimization at the puncture site was not associated with any increase in PSV values. In conclusion, percutaneous femoral hemostasis after TAVI was associated with a low rate of late VC. The results were similar irrespective of the hemostasis technique and the use of balloon dilation at the puncture site, but women and a smaller femoral size were associated with increased PSV values. Further studies are needed to determine the optimal femoral hemostasis technique in TAVI procedures.

Investigation of Novel, Internally Hollowed Structured Stainless Steel to Reduce Stress Shielding

There are many aspects that have direct effects on total hip replacement performance (THR), such as material properties, applied loads, surgical approach, femur size and quality, prosthesis design, bone-implant interface etc. One of the purposes to study different structures in THR is reducing the stress shielding. For the current study, an innovative hollow spherical structure is developed for femoral hip stems. The aim is to extract volume in the spherical shape from the stainless-steel hip implant stems, in order to focus solely on correlating with titanium behavior. Internal geometry for the femoral stem is optimized in order to transfer more stress onto the bone. Moreover, the approach involves extracting volume in the spherical shape from the internal structure to reduce stress shielding. A new novel implant is proposed that demonstrated a reduction in stress shielding. The sphered models have a smaller young’s modulus and strength than the solid stainless-steel sample. The spheres in hollowed structures reduce the stress shielding and they transfer more stress onto the bone when compared to the solid stainless-steel models. This approach also involves restructuring a hard material, such as stainless steel, to enhance osseointegration. The reduction of the young’s modulus and stress directly depends on the volume of the hollow spheres in the models; however, there is a certain volume that can be extracted from solid

Residency Diary: Fourth Year-Milestones.

Residency Diary: Fourth Year-Milestones.

Postnatal ontogeny of the femur in fossorial and semiaquatic water voles in the 3D-shape space.

Water voles of the genus Arvicola constitute an excellent subject to investigate to which extent function affects postnatal developmental growth of limb structures in phylogenetically close species. We performed a comparative analysis of postweaning femur form changes between Arvicola sapidus (semiaquatic) and Arvicola scherman (fossorial) using three-dimensional landmark-based geometric morphometrics. In both species, we observed greater femur robustness in juvenile individuals than in adult ones, probably due to the accommodation of high loads on the bone during initial locomotor efforts. Significant interspecific differences were also found in the femur size and shape of adult specimens, as well as in the postnatal allometric and phenotypic trajectories. In terms of phenotypic variation, fossorial water voles show relatively wider third and lesser trochanters, and greater femur robustness than A. sapidus, characters associated to the digging activity. In contrast, A. sapidus displays a slight increase of the greater trochanter in comparison with A. scherman, which is seemingly an adaptive response for enhancing propulsion through the water. Results evidence that certain morphological traits and differences between A. sapidus and A. scherman in the allometric and phenotypic trajectories of the femur are associated with their different locomotor mode.

Using MRI Measurement to Improve Accuracy of Femoral Component Sizing in Oxford Unicompartmental Knee Arthroplasty.

Unicompartmental knee arthroplasty (UKA) can achieve better kinematics and faster recovery than total knee arthroplasty. The Phase III Oxford UKA system has five sizes of femoral components to approximate the normal knee geometry. However, these different sizes may also induce problems, such as the misselection of component size. Different criteria have been proposed to predict the ideal size preoperatively. However, no single method can be applied universally. Therefore, this study aimed to develop a preoperative measurement using knee magnetic resonance imaging (MRI) to predict femoral component size. A total of 68 patients who underwent UKA were investigated from June 2019 to April 2020. 16 knees using a different MRI protocol were excluded. We developed an MRI measurement method to determine femoral size instead of gender- and height-based methods. The accuracy of different methods was compared using postoperative true lateral view radiographs. Three different kinds of gender- and height-based criteria, preoperative templating and intraoperative spoon measurement were compared. The accuracy of MRI measurement was 90.3%. Therefore, a significant difference was found between MRI measurements and all other methods, such as templating or gender- and height-based methods. In conclusion, the MRI measurement method can be concluded to accurately predict femoral component size in UKA. This method could be used regardless of different ethnic groups, individual knee geometry, or soft tissue tension.

Changes in anterior femoral articular cartilage structure in collegiate rugby athletes with and without a history of traumatic knee joint injury following a five-month competitive season

This study aimed to examine anterior femoral cartilage morphology before (pre-season) and after (post-season) a 5-month competitive season in collegiate ruby players with and without a previous history of traumatic injury to ligamentous, meniscus, and/or cartilage structures at the knee joint. Using a prospective cohort design, 42 male collegiate rugby players with a previous history of traumatic intracapsular knee joint injury and 124 players without knee injury history were included in this study. Ultrasonography assessments of anterior femoral cartilage were performed before (pre-season) and following a 5-month athletic season (post-season). Rugby players with a history of traumatic knee joint injury had greater lateral condylar thickness (2.37 ± 0.35 mm, p = 0.03), intercondylar thickness (2.51 ± 0.47 mm, p = 0.03), and partial area (44.67 ± 7.28mm2, p = 0.02) compared to control players (lateral = 2.23 ± 0.35 mm, intercondylar = 2.32 ± 0.47 mm, partial area = 41.60 ± 7.26 mm2), regardless of pre-and post-season assessment time points. Pre-season ultrasonography assessment of lateral condylar thickness (2.34 ± 0.47 mm, p = 0.02), medial condylar thickness (2.05 ± 0.43 mm, p = 0.03), and partial area (44.10 ± 9.23 mm2, p = 0.001) were significantly greater than the post-season ultrasonography assessment time point (lateral = 2.26 ± 0.43 mm, medial = 1.98 ± 0.43 mm, partial area = 42.17 ± 8.82 mm2), regardless of group membership. Rugby players with a history of intracapsular knee joint injury displayed altered anterior femoral cartilage size via ultrasonography assessments. Regardless of a presence of injury history, collegiate rugby players showed a decrease in cartilage thickness and partial area following a 5-month competitive season.

Radiographic and Clinical Evolution of the Oxford Unicompartmental Knee Arthroplasty.

The aim of the study is to evaluate whether the use of the new instrumentation Microplasty (MP) improves component positioning and the reliability of the surgical technique, reducing the implant outliers from the recommended range and providing a more accurate resection, while avoiding insufficient or excessive tibial resection and clinical scores. We prospectively analyzed clinical and radiographic outcomes of three consecutive cohorts for a total of 227 implants at a minimum follow-up of 36 months. The first cohort consisted of 67 Oxford unicompartmental knee arthroplasty (OUKA), using the phase III (Ph-III). The second cohort consisted of 136 OUKA, with the MP instrumentation. The third cohort consisted of 24 hypoallergenic OUKA, using the MP instrumentation (TiNbN). Postoperative alignment of the knee in the coronal and sagittal plane was measured using radiographs. No clinical differences were found among the three groups (p > 0.05). A significant difference was found on the slope between Ph-III and MP (p = 0.0005). Moreover, a significant difference was found in tibial angle and in tibial slope in arthroplasty with femoral size small (S), compared with size medium (M) or large (Ly) (tibia varus/valugs angle: p = 0.0484; tibial slope: p = 0.04). Similar results were found between small (AA, A, B) tibial size and large (C, D, E, F) tibial size for tibial varus/valgus (p = 0.03) angle and tibial slope (p = 0.003). A significant difference was found between Ph-III and MP in tibial slope in patients with body mass index (BMI) ≥25 kg/m2 (p = 0.0003). A positive correlation was noted between the femoral and tibial sizes and the tibial angle and the slope, and a negative correlation between weight and the tibial slope; furthermore, a positive correlation was found between Oxford knee score and radiographic angles. The MP instrumentation seems to be effective in determining the tibial cut and, particularly, improving the tibial slope, compared with Ph-III. The tibial slope is directly affected by the weight and measurements of the components, regardless of the instruments or the number of pegs, while clinical outcomes are correlated with implant position. This prospective comparative study reflects level of evidence II.

The Accuracy and Ability of Preoperative Templating to Restore Femoral Offset in Calcar-Guided Short-Stem Total Hip Prosthesis through Direct Anterior Approach

AbstractThe aim of this study was to assess the applicability and ability of preoperative templating to restore femoral offset and hip length with a calcar-guided short-stem implant design in total hip arthroplasty through the direct anterior approach. Preoperative measurements were performed of femoral offset, hip length, and stem size and compared with the perioperative placed prosthesis in 100 patients undergoing primary total hip replacement through direct anterior approach. Additionally, the pre- and postoperative femoral offset and hip length were compared to evaluate the ability to restore the offset and hip length with this kind of femoral short stem. With an acceptance of 1 size difference pre- and postoperatively, a 94% accuracy of predicting the size of the calcar-guided short stem was achieved with templating. Femoral offset was within means of 5 mm in 82.2% of the patients. Postoperative hip length was within 6 mm in 90% of the patients compared with the preoperative length.The use of preoperative templating for total hip arthroplasty with calcar-guided short-stem implants was proven to be a useful tool to predict the definite implanted size of the femoral prosthesis. Our results show that this new stem design does not significantly differ from previous reported outcomes with other stem designs and is competent to restore the femoral offset and hip length within clinical acceptable range. Level of evidence Level 3 retrospective case study.

Does Patient Specific Factors or Alignment Influence Total Knee Arthroplasty Clinical and Functional Outcomes?

Objectives:Knee alignment following total knee arthroplasty (TKA) may be the most important factor determining the long-term survival of the prosthesis. Despite proper alignment of implants being strongly associated with greater stability and a lower rate of loosening, literature still finds conflicting results regarding the influence of TKA alignment in patients clinical scores. The present study sought to address what is the optimal postoperative TKA alignment.Methods:We retrospectively selected 100 consecutive primary knee replacements performed for primary knee osteoarthritis. Pre-operative full length weight bearing x-rays were used to evaluate native knee anatomic alignment, as well as proximal tibial and distal femoral coronal alignment. Pos-operative full length weight bearing x-rays were also used to evaluate TKA alignment, tibial and femoral components coronal alignment, tibial position, tibial slope and femoral flexion angle. Extension anteroposterior (AP) and profile at 30º of flexion x-rays were used. Functional assessment was conducted including the VAS, the Oxford Knee and the Kujala scores, as well as range of motion (ROM).Results:Regarding ROM, only 8 patients didn’t presented full range of motion. Regarding the native knee, the average anatomical angle was 174 ± 4º. The average femoral distal coronal angle was 88±4º and the average tibial proximal coronal angle was 89±6º. The average post-operative angles were: 175±3º for the TKA tibia-femoral coronal angle, 88±6º for the coronal femoral angle and 89±3º for the coronal tibial angle. Regarding tibial tray position, when referring to the medial cortex of the proximal tibia, our sample had a tray in average 1±1mm more lateral than the medial cortex, with the worst positioned tibial components being 3,2mm medial or lateral to the medial cortex. When considering the proximal tibia lateral cortex, our patients had in average a tibial tray 1±2mm more medial than the lateral cortex, with the worst positioned tibial components being 4,2mm medial or 2,2mm lateral to the lateral cortex. Regarding the TKA sagittal alignment, the average TKA tibial slope was of 3±4º, and the average femoral flexion angle was 10±3º. Gender, IMC or age didn’t seem to influence TKA clinical results, either regarding pain (VAS) or function (Kujala or Osxford Scores).Comparing patients with post-operative alignment within of 5º of the native knee anatomical alignment, with patients with greater differences, no significant differences were obtained regarding pain or function.Also comparing patients with pos-operative coronal femoral or tibial angle within 85-95º, with patients with greater differences, no significant differences were reached regarding clinical outcomes. Besides that, tibial tray coronal position also didn’t seem to influence patient results.In regard to sagittal alignment, neither the femoral flexion angle or the tibial slope showed and correlation to post-operative outcomes. Regarding TKA size, the tibial tray or polytene size didn’t seem to influence clinical outcomes, however the femoral component size showed correlation with the functional scores, with smaller femoral sizes associated with greater Oxford scores (p=0,0029).Conclusion:Most patients of our sample seem to have well aligned TKA, with an difference of only 1º between the native knee anatomic angle and the TKA alignment. Regarding tibial tray position, most surgeons opted for a tibial tray smaller than the tibial plateau, however these differences were of 1 millimeter medially and laterally, which probably is not clinically significant. The tibial slope is also within the desired values of 0-7º. We verified that most errors in tibial tray regard positioning it more medially than laterally, however we can assume that the tibial tray is, in most patients, correctly sized and positioned. Regarding femoral sagittal alignment, our sample showed a greater femoral flexion than previously described, however the clinical relevance of this measurement is sill controverse. Despite some papers describing an association between greater femoral flexion angle and patellofemoral instability, in our sample this angle didn’t seem to influence the Kujala score. No differences in pain or functional results were obtain in regard to TKA alignment, however this can be explained by the fact that most patients presented well aligned TKAs.

Prosthesis size distribution in Oxford phase III unicompartmental knee arthroplasty - Based on more than 1900 Chinese patients

IntroductionIt is difficult to determine the optimal size of unicompartmental knee arthroplasty (UKA) prosthesis both pre-operatively and intra-operatively. Inappropriate femoral and tibial components are still the leading cause of failure. Several guidelines based on the Western population may not apply to the Chinese patients. We consequently try to investigate distributions of Oxford-UKA prosthesis in Chinese patients in order to provide a good reference for surgeons preoperatively. MethodsFrom January 2010 to December 2019, 1909 patients (2307 knees) with primary anteromedial osteoarthritis accepted Oxford phase III UKA. Statistical analyses were performed on the distributions of the femoral, tibial, and matching of the femoral-tibial prosthesis. The possible factors affecting the sizes of femoral components, including gender, height based on gender were investigated. Results1. The distributions of femoral size components include extra-large (XL) 0, large (L) 1.08%, medium (M) 26.09%, small (S) 59.64%, extra-small (XS) 13.18%; the tibial sizes components were F 0, E 0.69%, D 7.80%, C 19.59%, B 24.79%, A 34.16%, AA 12.96%. 2. The matching of femur-tibia components were L-E 0.52%,L-D 0.52%,M-E 0.17%, M-D 7.28%,M − C 16.60%,M − B 1.95%,M-A 0.13%, M-AA 0.04%, S-C 2.99%, S-B 22.67%, S-A 31.12%, S-AA 2.82%, XS-B 0.17%, XS-A 2.90% and XS-AA 10.10%. The optimal matches between femoral and tibial components were: XL with F; L with E; M with C and D; S with A and B. 3. The patient's gender and height based on gender are necessary considerations for selection of femoral components (P＜0.01). ConclusionIn Chinese patients, the size of femoral components is mainly small (S) for women, medium (M) for men. The tibial components of female patients are mainly A and B, whereas C is predominant for male patients. The more commonly used matching forms are S-A and S-B.