Femoral Size Research Articles

Mitigating calcar fracture risk with automated impaction during total hip arthroplasty

BackgroundAutomated broaching has recently been introduced for total hip arthroplasty (THA), with the goal of improving surgical efficiency and reducing surgeon workload. While studies have suggested that this technique may improve femoral sizing and alignment, little has been published regarding its safety, particularly with regard to calcar fractures. The purpose of our study was to evaluate the risk of calcar fracture during automated broaching, and to determine if this risk can be mitigated. MethodsWe queried our prospective institutional database and identified 1596 unilateral THAs performed by the senior author using automated impaction between 2019 and 2023. We identified the incidence of calcar fracture with automated impaction, and whether the fracture occurred during broaching or stem insertion. We additionally determined calcar fracture incidence within two consecutive subgroups of patients using different stem insertion techniques; subgroup (1): automated broaching with automated stem insertion for all patients; versus subgroup (2): automated broaching with automated stem insertion ONLY if a cushion of cancellous bone separated the broach from the calcar, otherwise the stem was placed manually. Continuous and categorical variables were analyzed with Student's t-test and Fisher's exact test, respectively. ResultsSeventeen calcar fractures occurred intraoperatively (1.1 %). Only two fractures occurred during automated broaching (0.1 %), while fifteen occurred during final stem impaction (0.9 %) (p = 0.007). Four calcar fractures (1.4 %) occurred in subgroup 1, compared to two in subgroup 2 (0.6 %) (p = 0.28). ConclusionsOur study found a calcar fracture incidence of 1.1 % using automated impaction, consistent with historically reported rates of 0.4–3.7 %. We found that calcar fractures are more likely to occur during stem insertion than during femoral broaching. We recommend that if any part of the final broach is in direct contact with the calcar, the final stem should be impacted manually to minimize fracture risk.

Beyond head and wings: Unveiling influence of diet, body size, and phylogeny on the evolution of the femur in phyllostomid bats.

Phyllostomidae, the most diverse family of Neotropical bats, encompass 230 species with varied dietary habits and food acquisition methods. Their feeding niche diversification has shaped skull and wing morphologies through natural selection, reflecting food processing and flight strategies. Yet, evolution of bat hindlimbs, especially in phyllostomids, remains little understood. Previous studies highlighted the femur's morphology as a key to understanding the evolution of quadrupedalism in yangochiropteran bats, including the adept walking observed in vampire bats (Desmodontinae). Here, we aimed to describe the femoral morphological variation in Phyllostomidae, correlating this with body size and assessing the effects of phylogenetic history, dietary habits, and hindlimb usage. Analyzing 15 femoral traits from 45 species across 9 subfamilies through phylogenetically informed methods, we discovered a significant phylogenetic structure in femoral morphology. Allometric analysis indicated that body mass accounts for about 85% of the variance in phyllostomid femoral size and about 11% in femoral shape. Relatively smaller femurs showed to be typical in Stenodermatinae, Lonchophyllinae, and Glossophaginae, in contrast to the larger femurs of Phyllostominae, Desmodontinae, Micronycterinae, and Lonchorrhininae. Furthermore, extensive femur shape variation was detected, with the most distinct morphologies in vampire bats, followed by frugivorous species. Adaptive evolutionary models related to diet more effectively explained variations in femoral relative size and shape than stochastic models. Contrary to the conventional belief of limited functional demand on bat femurs, our findings suggest that femoral morphology is significantly influenced by functional demands associated with diet and food capture, in addition to being partially structured by body size and shared evolutionary history.

Femoral component size in total knee replacement: a retrospective study

Background: Osteoarthrosis is the most common articular disease in the developed world. The number of people affected by knee osteoarthrosis is exponentially increasing, and with total knee replacement (TKA) demand expected to continue growing. The study establishes the relationship between femoral size components used in TKA and patients’ demographics. Methods: A retrospective cohort study of 385 surgeries that underwent TKA at the tertiary hospital over the period between January 2018 and December 2021 was conducted. The patients’ demographics, including height, weight, body mass index, gender, and age, and the implanted component size and type of the component (gender or not) were collected. Results: A significant association was found between the gender of patients and the femoral component size (P<0.001). Furthermore, height and weight had a significant correlation with femoral component size (P=0.399, P<0.001 and P=0.114, P=0.025, respectively); however, body mass index and age were not statistically correlated with femoral component size (P=0.625, 0.138, respectively). Upon ordinal logistic regression analyses, height and gender were significant predictors of the implanted femur component size (P<0.001). However, age and weight were insignificant factors in the model (P=0.640 and P=0.211, respectively). Conclusion: The results described will help with the pre-operative predictions of the total knee replacement femoral component size, which will decrease the operating time and implant supply chain efficiency. Further advancement of the model could be achieved with future multicenter studies with a larger sample.

Can machine learning predict the accuracy of preoperative planning for total hip arthroplasty, basing on patient-related factors? An explorative investigation on Supervised machine learning classification models.

BackgroundThe success of Total Hip Arthroplasty (THA) is influenced by preoperative planning, with traditional 2D approaches displaying varied reliability as well. The present study investigates the use of Supervised Machine Learning (SML) models with patient-related features to improve accuracy. MethodsPreoperative and perioperative data, as well as planning and final implant information, were obtained from 800 consecutive cementless primary THA, which was performed uniformly by a specialized surgical team. Six Supervised Machine Learning models were trained and validated using patient characteristics and implant data: Logistic Regression (LR), Linear Discriminant Analysis (LDA), K-Nearest Neighbors (KNN), Decision Tree (CART), Gaussian Naive Bayes (GN), and Support Vector Classifier (SVC). The models' ability to predict planning reliability and leg length disparity was evaluated. ResultsKNN performed better on the cup model (97.9 %), femur model (96.7 %), and femur size (99.2 %). SVM emerged as the model with the highest accuracy for cup size (60.4 %) and head size (62.1 %). CART had the best accuracy (99 %) when determining leg length discrepancy. ConclusionThe study demonstrates the utility of Supervised Machine Learning models, specifically KNN, in predicting the accuracy of preoperative planning in THA. The accuracy of these models, which are driven by patient-related characteristics, provides useful information for optimizing patients’ selection and improving surgical outcome.

Surgeon's Experience and Accuracy of Preoperative Digital Templating in Primary Total Hip Arthroplasty.

Preoperative planning has become essential in performance of total hip arthroplasty (THA). However, data regarding the effect of the planner's experience on the accuracy of digital preoperative planning is limited. The objective of this study was to assess the accuracy of digital templating in THA based on the surgeon's experience. A retrospective study was conducted. An analysis of 98 anteroposterior pelvic radiographs, which were individually templated by four surgeons (two hip surgeons and two orthopaedic residents) using TraumaCad® digital planning, was performed. A comparison of preoperatively planned sizes with implanted sizes was performed to evaluate the accuracy of predicting component size. The results of preoperative planning performed by hip surgeons and orthopaedic residents were compared for testing of the planner's experience. Femoral stem was precisely predicted in 32.4% of cases, acetabular component in 40.3%, and femoral offset in 76.7%. Prediction of cup size showed greater accuracy than femoral size among all observers. No differences in any variable were observed among the four groups (acetabular cup P=0.07, femoral stem P=0.82, femoral offset P=0.06). All measurements showed good reliability (intraclass correlation coefficient [ICC] acetabular cup: 0.76, ICC femoral stem: 0.79). The results of this study might suggest that even though a surgeon's experience supports improved precision during the planning stage, it should not be restricted only to surgeons with a high level of experience. We consider preoperative planning an essential part of the surgery, which should be included in training for orthopaedics residents.

Who Are the Anatomic Outliers Undergoing Total Knee Arthroplasty? A Computed Tomography–Based Analysis of the Hip-Knee-Ankle Axis Across 1,352 Preoperative Computed Tomographies Using a Deep Learning and Computer Vision–Based Pipeline

BackgroundDissatisfaction after total knee arthroplasty (TKA) ranges from 15 to 30%. While patient selection may be partially responsible, morphological and reconstructive challenges may be determinants. Preoperative computed tomography (CT) scans for TKA planning allow us to evaluate the hip-knee-ankle axis and establish a baseline phenotypic distribution across anatomic parameters. The purpose of this cross-sectional analysis was to establish the distributions of 27 parameters in a pre-TKA cohort and perform threshold analysis to identify anatomic outliers. MethodsThere were 1,352 pre-TKA CTs that were processed. A 2-step deep learning pipeline of classification and segmentation models identified landmark images and then generated contour representations. We used an open-source computer vision library to compute measurements for 27 anatomic metrics along the hip-knee axis. Normative distribution plots were established, and thresholds for the 15th percentile at both extremes were calculated. Metrics falling outside the central 70th percentile were considered outlier indices. A threshold analysis of outlier indices against the proportion of the cohort was performed. ResultsSignificant variation exists in pre-TKA anatomy across 27 normally distributed metrics. Threshold analysis revealed a sigmoid function with a critical point at 9 outlier indices, representing 31.2% of subjects as anatomic outliers. Metrics with the greatest variation related to deformity (tibiofemoral angle, medial proximal tibial angle, lateral distal femoral angle), bony size (tibial width, anteroposterior femoral size, femoral head size, medial femoral condyle size), intraoperative landmarks (posterior tibial slope, transepicondylar and posterior condylar axes), and neglected rotational considerations (acetabular and femoral version, femoral torsion). ConclusionsIn the largest non-industry database of pre-TKA CTs using a fully automated 3-stage deep learning and computer vision-based pipeline, marked anatomic variation exists. In the pursuit of understanding the dissatisfaction rate after TKA, acknowledging that 31% of patients represent anatomic outliers may help us better achieve anatomically personalized TKA, with or without adjunctive technology.

An Evaluation of Anatomic Referencing for Femoral Component Sizing Using Computed Tomography-Based Computer Modeling.

One of the critical steps in total knee arthroplasty is femoral component positioning and sizing. Historically, there was wider variability between femoral component sizes, necessitating the concepts of anterior referencing (AR) and posterior referencing (PR). With the introduction of smaller increments between sizes, the concept of anatomic referencing has been introduced to replace AR and PR. The intent of this study was to validate the concept of anatomic referencing and show that with 2 mm increments in femoral sizes, the femoral component can be placed flush to the anterior cortex while maintaining posterior condylar offset (PCO). Digital surface models were created using 515 femurs from an established computed tomography database. Virtual bone resections, component sizing and placement were performed assuming neutral mechanical axis and a cartilage thickness of 2 mm. The appropriately sized femoral component, which had 2 mm incremental sizes, was placed flush with the anterior cortex with restoration of the PCO. The anterior-posterior distance from the posterior surface of the component to the medial and lateral surfaces of the posterior condylar cartilage were measured. The medial condyle was the limiting condyle in the majority of cases (73%). The average medial gap after appropriate femoral component matching was 0.6 mm (0.39-1.41 mm) across all sizes. The overall average condylar gap was 1.02 mm. The most common femoral component was a size 7 (57.2 mm) and the average femoral AP width was 55.9 mm. Anatomic referencing with an implant system that has 2-mm increments in femoral component sizing provides an alternative to AR and PR without compromise. Anatomic referencing allows for perfect alignment of the anterior flange of the femoral component to the anterior cortex of the femur while restoring the native PCO to within 1 mm. This avoids having to choose between AR or PR when in between femoral sizes.

Effects of a Diet Low in Vitamin and Mineral Complex and Darkness on the Growth Performance, Mineralization and Femur Histological Structure of Broiler Chickens

Background: The aim of this study was to investigate the effects of dietary vitamin and mineral deficiency and darkness on growth performance, femur size, mineralization and bone microstructure in broiler chickens. Methods: 120 male Cobb 500 chicks were randomly assigned to three groups, including a control group and two experimental groups (1st group on a vitamins and minerals deficient diet, 2nd group reared in total darkness), with 40 subjects per group from day 7. Daily calculations of average weight and weight gain were performed and morphological and histomorphometric measurements of the femur were performed on days 28, 35 and 42. Result: The results revealed that the experimental groups showed a significant decrease in growth performance, body weight and weight gain (P less than 0.05) compared to the control group. In addition, a reduction in bone mineralization (weight and ash percentage) and altered bone microarchitecture were observed in the experimental groups. These results indicated that vitamin and mineral complex deficiencies in feed and darkness negatively affected growth performance and trophic and morpho-histological aspects of long bones in broilers. The results of this study may have significant implications for the poultry industry, as they highlights the need to consider factors such as nutrition and lighting conditions when rearing broiler chickens for optimal growth and health. In conclusion, the present study provides valuable insights into the effects of dietary deficiencies of the vitamin-mineral complex and darkness on broiler growth and bone development.

KINEMATIC ALIGNMENT TECHNIQUE IN TOTAL KNEE ARTHROPLASTY CHANGES FEMORAL SIZING

Introduction: Kinematic alignment (KA) is an innovative approach designed to restore natural knee kinematics in Total Knee Arthroplasty (TKA). Unlike traditional mechanical alignment (MA), which focuses on aligning the femur and tibia along a mechanical axis, KA considers the three axes governing the movement of the patella and tibia relative to the femur. This difference leads to variations in femoral sizing between the two techniques. KA has shown to significantly reduce femoral size compared to MA in TKA patients. Material and Methods: This retrospective study analyzed the records of 323 patients who underwent TKA from 2017 to 2024. Patients were divided into two groups: 177 received KA, and 146 received MA. Data on femoral and tibial component sizes were collected. The primary objective was to compare differences in femoral and tibial sizing between the groups. The mean difference in femoral size was calculated. Demographic data were used to predict the expected femoral size for a subset of patients, comparing predicted to actual sizes. Discrepancies were analyzed between KA and MA groups. Results: Femoral sizing differed significantly between groups. In the KA group, 10.7% needed a smaller femoral size than tibial, 51.4% had equal sizes, and 37.9% needed a larger femoral size. In the MA group, 1.3% needed a smaller femoral size, 28.8% had equal sizes, and 69.9% needed a larger femoral size (p<0.001). The mean femoral size difference was significant: 0.29 for KA and 0.62 for MA (p<0.001). KA more often resulted in a smaller-than-predicted femoral size than MA (68.7% vs. 53.6%, p<0.05). Conclusions: This study highlights the significant impact of KA on femoral sizing in TKA. KA leads to a greater proportion of patients requiring smaller femoral components compared to MA. The substantial difference in femoral sizing distributions between the groups (p<0.001) underscores the importance of considering alignment techniques in preoperative planning and component selection for TKA.

A Comparative Study of Morphometric Parameters of Knee Using Magnetic Resonance Imaging in Different Population Groups

Abstract Background: The design of majority of commercially available knee implants has their basis on data obtained from the European population. Anthropometric research has demonstrated a difference in the shape and size of proximal tibia and distal femur between the genders and ethnic groups. Underfit or overhang of prosthetic components can result in poor clinical and functional outcomes with need for revision. This study compares the dimensions of the knee in multiple racial groups to observe if significant racial and gender differences occur. Methodology: Morphometric parameters of the knee of adult patients (>18 years) in four population groups (Native Emirati, East Asian, Indian, and Caucasian) were measured using magnetic resonance imaging. Knee parameters were obtained from 368 patients (179 females and 189 males). Results: Males have larger femoral and tibial parameters compared to females (P < 0.01). For any specified anteroposterior length of knee, females demonstrate narrower mediolateral widths compared to males. Significant differences exist in knee parameters between the racial groups in both genders (P < 0.01). Conclusion: Adult knee parameters show significant variation between the genders and racial groups showing strong evidence for a race- and gender-specific knee arthroplasty system.

Comparison of three-versus two-dimensional pre-operative planning for total hip arthroplasty

BackgroundA successful clinical outcome for total hip arthroplasty (THA) depends on accurate sizing and positioning of the implants. Using three-dimensional (3-D) pre-operative planning with a computerized tomography (CT) scan has many potential advantages over conventional 2-D planning using radiographs, including potentially more accurate assessments of the size and anteversion of the acetabulum, as well as lateral femoral offset. The purpose of this study was to compare the accuracy of 3-D to 2-D templating with respect to acetabular and femoral size, as well as lateral femoral offset. MethodsPre-operative templating data was collected prospectively from a consecutive series of 290 primary THAs (acetabulum on all, femoral component on 255 of the cases using one specific stem). All cases were initially templated on a digital imaging picture archiving and communication (PACS) system with calibrated images to estimate the acetabular size, femoral size, and lateral femoral offset. The 3-D templating was then performed with software based on a CT scan, and the results were compared to what was surgically implanted. ResultsThe 3-D templating for the acetabulum was accurate 99.7% of the time based on the final implanted component. The 2-D templating for the acetabulum was accurate 39% of the time, with 46% templating larger and 15% templating smaller than the final implanted component. The 3-D templating of the femoral component was accurate 63% of the time, and within one size of final implant in 96% of cases. The 2-D templating of the femoral component was accurate 53% of the time and within one size of final implant in 94% of cases. Lateral femoral offset consistently matched the 3-D plan, with a 100% match rate. The 2-D templated femoral offset was accurate 87% of the time and was changed in 13% of cases after 3-D templating. ConclusionThe CT-based 3-D preoperative planning was superior to 2-D planning for THA with respect to acetabular size, femoral size, and lateral femoral offset. Precise acetabular component sizing conserves bone and allows for a more predictable press fit, while facilitating efficient inventory management. Lateral femoral offset is often difficult to measure on 2-D images, and 3-D templating consistently allows for accurate offset restoration, which is important for normal hip function and stability.

Les ménisques mobiles peuvent se luxer avec des composants fémoraux plus petits et des composants méniscaux plus épais après arthroplastie unicompartimentale médiale du genou de type Oxford

BackgroundA mobile bearing can dislocate when joint laxity is larger than jumping height, the height difference between the bottom and the peak of the bearing (the highest point of the upper bearing surface on each side). Significant laxity due to improper gap balancing should therefore be avoided. However, once the bearing rotates vertically on the tibial component, the bearing can dislocate with smaller laxity than the jumping height. We mathematically calculated the required laxity for dislocation (RLD) and the required rotation of the bearing for dislocation (RRD). The current study addressed the question: 1) could the femoral component size and the bearing thickness affect the RLD and RRD? HypothesisThe femoral component size and the bearing thickness could affect the MLD and MRD. MethodsThe RLD and RRD were calculated using the bearing dimensions provided by the manufacturer with femoral component size, bearing thickness, and directions (anterior, posterior, and medial/lateral) as the variables on a two-dimensional basis. ResultsThe RLD was 3.4 to 5.5mm in the anterior, 2.3 to 3.8mm in the posterior, and 1.4 to 2.4mm in the medial or lateral directions. The RLD decreased with a smaller femoral size or a thinner bearing. Similarly, the RRD decreased with a smaller femoral size or a thinner bearing thickness in all directions. ConclusionsIncreased bearing thickness and decreased femoral component size deceased the RLD and RRD, which would relate to an increased risk of dislocation. Selecting the femoral component as large as possible and the bearing as thin as possible would therefore be helpful in the prevention of dislocation. Level of evidenceIII; comparative computer simulation study.

Lower Rates of Femoral Fracture and Subsidence with a Morphometric Stem in Cementless Total Hip Arthroplasty.

A "morphometric" tapered femoral stem with size-specific medial curvatures and proportional neck lengths was introduced, attempting to improve fixation and biomechanics in cementless total hip arthroplasty (THA) across a range of femoral sizes and morphotypes. We investigated whether this design reduced complications and better restored anatomy (e.g., limb length and offset) compared to a traditional tapered stem with consistent neck lengths across sizes. We reviewed 389 THAs (340 patients) performed using either of two cementless femoral implants. Records were reviewed for demographics, surgical details, complications, and reoperations. Radiographs were examined for subsidence, biologic fixation, leg lengths, offset, and proximal femoral morphology. The intraoperative fracture rate was lower with this morphometric stem compared to this traditional stem (0 vs. 3.4%), as was the incidence of postoperative subsidence ≥3mm (4.7 vs. 19.2%). With the numbers available, no differences were identified regarding rates of reoperation for periprosthetic femur fracture (0 vs. 1.0%) and femoral fixation failure without fracture (1.1 vs. 0%), or all-cause reoperations (2.7 vs. 2.4%). Limb length and offset restoration were similar with the two implants, but the shortest available femoral head was used less frequently with this morphometric stem compared to this traditional stem (22 vs. 54%). This morphometric stem was associated with decreased rates of intraoperative fracture and postoperative subsidence, along with decreased use of the shortest available head. Nevertheless, both implants demonstrated clinical success, allowing reconstruction of limb length and offset with low rates of femoral fixation failure.

MRI Analysis of Knee Bony Morphology Variations in Children and Adolescents With Lateral Discoid Meniscus Compared With Asymptomatic Healthy Controls

Background: Lateral discoid meniscus accounts for most meniscal tears in children 10 years of age and younger. The role of bony morphology in discoid meniscus has been previously studied in a limited capacity using radiographs. Purpose: To use magnetic resonance imaging to measure features of the femoral condyles and tibial plateaus in patients with discoid meniscus to assess potential determinants of symptoms and subsequent surgery and to compare with matched controls to investigate age-related changes in bony features. Study Design: Cross-sectional study; Level of evidence, 3. Methods: After institutional review board approval, detailed morphology of the femoral condyles and tibial plateau was measured in 177 patients (3-18 years of age; 56% female) with confirmed lateral discoid meniscus. Measurements from 269 participants (3-18 years of age; 55% female) with asymptomatic knees were used as controls. Two-way analysis of variance with Holm-Šídák post hoc was used to compare measurements between discoid menisci and matched controls. Independent t tests were used to compare aspects of bony morphology within the discoid meniscus cohort. Results: Compared with controls, patients with a lateral discoid meniscus had a larger bicondylar width and notch width (7- to 10-year-old and 15- to 18-year-old age groups; P < .05), larger tibial plateau width (11- to 14-year-old and 15- to 18-year-old age groups; P < .001), and smaller lateral (P < .02) and coronal (P < .02) tibial slopes across all age groups. Among patients with a discoid meniscus, larger bicondylar width, larger tibial plateau width, larger notch width, and a flatter lateral femoral condyle were associated with pain (P < .005) and lateral meniscal tears (P < .02). Larger notch width and notch width index were also associated with subsequent surgery (P < .05). Conclusion: There are clinically significant abnormalities in bony morphology in patients with a discoid meniscus, including larger femoral condyles and tibial plateaus and a flatter tibial plateau. Additionally, femoral size, femoral curvature, and tibial plateau size may influence the likelihood of knee pain, meniscal tear, and need for surgery. These findings highlight the importance of bony morphology in discoid meniscus pathophysiology in children and adolescents. Such measurements may also aid radiographic detection of discoid meniscus and guide decisions regarding the timing of potential surgical intervention.

The Relationship of Os. Femur with Height influenced by Gender, Race, and Nutrition for Medical Student In Faculty of Medicine University Wijaya Kusuma Surabaya

Height is an important identity in forensics. Several long bones are known to be used for size estimation, one of which is the femur (Os. Femur). Personal height growth is affected by many factors, including gender, breed, and diet. This study aimed to analyze the correlation of Os length. Thigh height in UWKS medical students is influenced by gender, ethnicity and diet. This study used an observational descriptive analysis approach to conduct a cross-sectional study. Forty-four students from the UWKS School of Medicine participated in the study. Height measurement using Microcotoise, Os. Femoral New Deland with sliding calipers and weights with scales. Data were analyzed using normality test, Pearson correlation test, and simple linear regression test. The results show that there is a positive and very strong correlation between the Os lengths. Femur size, non-Javanese ethnicity, and normal, obese, and obese dietary categories in a male sample. There is now a strong positive relationship between femur length and height in the female sample. Meanwhile, the Os length has no correlation. Keywords: l ength os femur, height, gender, e thnicity, nutrition

Small changes in thermoregulation influence cancellous bone turnover balance in distal femur metaphysis in growing female mice

Mice are typically housed at temperatures well below their thermoneutral zone. When individually housed at room temperature (~22 °C) mice experience cold stress which results in cancellous bone loss and has the potential to alter the skeletal response to treatment. It is not clear if there is a threshold temperature for cold stress-induced bone loss. It is also not clear if alternative strategies for attenuating cold stress, such as group housing, influence bone accrual and turnover. This study aimed to determine how small differences in temperature (4 °C) or heat loss (individual versus group housing with nestlets) influence bone in growing female C57BL/6 J mice. Five-week-old mice were randomized by weight to 1 of 4 treatment groups (N = 10/group): 1) baseline, 2) single housed at 22 °C, 3) single housed at 26 °C, or 4) group housed (n = 5/cage) with nestlets at 22 °C. Mice in the baseline group were sacrificed 1 week later, at 6 weeks of age. The other 3 groups of mice were maintained at their respective temperatures and housing conditions for 13 weeks until 18 weeks of age. Compared to baseline, mice single housed at room temperature had increased body weight and femur size, but dramatically decreased cancellous bone volume fraction in distal femur metaphysis. The cancellous bone loss was attenuated but not prevented in mice individually housed at 26 °C or group housed at 22 °C. In conclusion, by impacting thermogenesis or heat loss, modest differences in housing conditions could influence experimental results.

Bearings can dislocate with smaller femoral components and thicker bearings in Oxford™ medial unicompartmental knee arthroplasty

BackgroundA mobile bearing can dislocate when joint laxity is larger than jumping height, the height difference between the bottom and the peak of the bearing (the highest point of the upper bearing surface on each side). Significant laxity due to improper gap balancing should therefore be avoided. However, once the bearing rotates vertically on the tibial component, the bearing can dislocate with smaller laxity than the jumping height. We mathematically calculated the required laxity for dislocation (RLD) and the required rotation of the bearing for dislocation (RRD). The current study addressed the question: 1) could the femoral component size and the bearing thickness affect the RLD and RRD? HypothesisThe femoral component size and the bearing thickness could affect the MLD and MRD. MethodsThe RLD and RRD were calculated using the bearing dimensions provided by the manufacturer with femoral component size, bearing thickness, and directions (anterior, posterior, and medial/lateral) as the variables on a two-dimensional basis. ResultsThe RLD was 3.4 to 5.5mm in the anterior, 2.3 to 3.8mm in the posterior, and 1.4 to 2.4mm in the medial or lateral directions. The RLD decreased with a smaller femoral size or a thicker bearing. Similarly, the RRD decreased with a smaller femoral size or a thicker bearing thickness in all directions. ConclusionsIncreased bearing thickness and decreased femoral component size deceased the RLD and RRD, which would relate to an increased risk of dislocation. Selecting the femoral component as large as possible and the bearing as thin as possible would therefore be helpful in the prevention of dislocation. Level of evidenceIII; comparative computer simulation study.

CORR Insights®: Does Matching Femoral Size and Shape Improve Bone Fit and Patient-reported Outcomes in TKA? A Matched Controlled Study.

CORR Insights®: Does Matching Femoral Size and Shape Improve Bone Fit and Patient-reported Outcomes in TKA? A Matched Controlled Study.

Does Matching Femoral Size and Shape Improve Bone Fit and Patient-reported Outcomes in TKA? A Matched Controlled Study.

Some researchers have suggested that achieving good component coverage over the host bone during TKA (while avoiding implant overhang) may help achieve durable implant fixation and may be associated with better outcomes scores. However, the evidence about this is limited and contradictory. Contemporary morphometric TKA includes a wide array of components with various shapes and sizes, based on large anatomic databases and specific software that simulates bone cuts. Morphometric tibial components have shown improved bone coverage and better clinical outcomes than standardized implants, but the role of morphometric femoral components in bone coverage has not been studied precisely. In a retrospective, controlled study that used patient matching, we asked: (1) Does the use of a contemporary morphometric component with more available sizes provide better femoral component fit and bone coverage than an earlier design with fewer sizes? (2) Are component fit and the presence of component overhang or underhang associated with different Knee Society Score (KSS) or Knee Injury and Osteoarthritis Outcome Score (KOOS) for Joint Replacement? From 2012 to 2013, we performed 403 TKAs according to the following criteria: TKA performed for primary tricompartmental arthritis of the knee; varus, valgus, and flexion deformity less than 15°; and age between 18 and 85 years on the day of surgery. Among these 403 TKAs, 237 were performed using a morphometric implant and 166 with the earlier nonmorphometric implant. At 2 years of follow-up, 3% of patients in the morphometric group and 5% in the nonmorphometric group were lost to follow-up. Based on age, BMI, gender, and preoperative KSS and KOOS, two groups of 30 patients were matched in a 1:1 ratio from this longitudinally maintained database. Clinical outcomes were measured preoperatively and at a minimum follow-up of 2 years in both groups, using the KSS and KOOS. We evaluated postoperative CT images for each patient to analyze femoral implant rotation, bone coverage, and overhang and underhang status. The overhang status was similar between the two groups (23% had an overhang component in the morphometric knee group and 27% had an overhang component in the nonmorphometric knee group), and overhang was most frequently found in the lateral distal zone and medial anterior chamfer. Better cortical bone coverage was found in the morphometric knee group, with a thinner bone margin between the component edge and cortical border (morphometric group: 3 mm versus nonmorphometric knee group: 5 mm; p = 0.01). In general, there were few between-group differences in terms of patient-reported outcomes; of the seven metrics we analyzed, only the KSS favored the morphometric knee implant by a margin larger than the minimum clinically important difference (KSS mean difference: 21 points for the morphometric knee group; p < 0.05). Overhang of the femoral component of > 2 mm was associated with poorer KOOS, but not KSS, whereas a thinner bone margin had a beneficial impact on pain and global clinical scores (KOOS and KSS: p < 0.05). The use of a morphometric femoral component design showed slightly improved bone fit and pain score according to the KSS at midterm follow-up compared with earlier implants with fewer sizes. Overhang > 2 mm was associated with worse KOOS. The tendency toward better outcomes in morphometric implants warrants longer-term evaluation before any definite conclusions about the association between bone fit and clinical results can be drawn.Level of Evidence Level III, therapeutic study.

Image-based robotic unicompartmental knee arthroplasty allowed to match the rotation of the tibial implant with the native kinematic knee alignment.

Image-based robotic tools improve the accuracy of unicompartmental knee arthroplasty (UKA) positioning, but few studies have examined its effect on axial alignment. The aim of this study was to compare the characteristics of tibial and femoral implant positioning, mainly the tibial rotation, during medial or lateral UKA, performed with an image-based robotic assisted system. A total of 71 UKA performed between September 2021 and June 2022 (53 medial and 18 lateral) were analyzed. All data regarding implant positioning (rotation, coronal and sagittal alignment) for tibial and femoral components were obtained using MAKO® software (Stryker®, Mahwah, USA) intra-operatively. The lateral UKA had a mean internal tibial rotation of 15.4 ± 3°, a mean external femoral rotation of 0.96 ± 2.4°, and a mean tibial slope of 4.7 ± 1.3°. The medial UKA had a mean internal tibial rotation of 0.18 ± 2.7°, a mean internal femoral rotation of 0.35 ± 2.2°, and a mean tibial slope of 5.4 ± 1.3°. The tibial rotations, femoral valgus, tibial varus and tibial size significantly differed between medial and lateral UKA (p < 0.05). There was no significant difference in femoral rotation, flexion, femoral size, slope, and polyethylene thickness between medial and lateral UKA. Medial and lateral UKA had significantly different implantation characteristics related to the biomechanics of the knee compartments. Image-based robotic UKA allowed precise femorotibial positioning per-operatively to match native kinematic alignment.