Risk Stratification for Varus Stem Positioning in Cementless THA: A Dual-Parameter Diagnostic Tool Based on Proximal Femoral Morphology

IntroductionPatients with hemophilia (PWH) constantly suffer hemarthrosis, which leads to deformity of the hip joint. Therefore, PWH who are going to receive total hip arthroplasty (THA) should be exclusively treated before the surgery with careful measurement of their proximal femur. Hence, we conducted a retrospective study to explore the anatomical parameters of and differences in the proximal femur in hemophilic patients who underwent THA.MethodsThe retrospective study comprised data of adult patients who received total hip arthroplasty from 2020 to 2022 in the research center. Patients having a diagnosis of hemophilic arthritis and received THA were included in experimental group, and patients with hip arthritis or femoral head necrosis were taken as control group. Parameters including femoral offset, neck‐shaft angle (NSA), medullary cavity of 20 mm above mid‐lesser trochanter level (T+20), mid‐lesser trochanter level (T), and 20 mm blow it (T−20), and canal flare index (CFI), femoral cortical index (FCI) were measured on X‐ray and CT images with PACS by two independent doctors. Data was analyzed by SPSS 20. Kolmogorov–Smirnov test was used to test data normality. Student's t‐test was performed between PWH and control group. p < 0.05 was considered statistically significant.ResultsAmong the 94 hips, 39 (41.5%) were included in group hemophilia and 55(58.5%) in control group. The mean age of the patients was 49.36 ± 12.92 years. All cases were male patients. Data demonstrated significantly smaller femoral cortical index (FCI), femoral offset, medullary cavity of 20 mm above mid‐lesser trochanter level, mid‐lesser trochanter level, and 20 mm below it, and neck‐shaft angle (NSA) was obviously larger in PWH than control group (p < 0.05). No significant difference was found in canal flare index (CFI).ConclusionHemophilic patients undergoing THA were prone to longer and thinner proximal femur. Preoperative morphological analysis of femur is recommended.

Leg-length changes at total hip arthroplasty (THA) may result from too proximal position of the femoral component, i.e. not being sunk deep enough into the femoral canal due to the size and shape of both medullary canal and implant. Some femoral implants are designed to achieve such fixation in the mediolateral dimension, while others also engage the bone anteroposteriorly. Our aim was to examine the relationship between proximal femoral morphology, osseointegration and leg-length equalization at THA. We asked whether the Dorr classification, femoral cortical index and canal flare index on preoperative radiographs had significant impact on THA aseptic loosening rates and post-operative leg-length discrepancy (LLD). Literature review included original articles on proximal femoral morphology with post-operative LLD and other clinical outcomes of THA, published in the last decade. Case reports and biomechanical studies without clinical data were excluded. Higher femoral cortical index and/or canal flare index (corresponding to the Dorr type A) increases the risk of leg lengthening at THA. This is particularly notable in femoral stems with metaphyseal fixation, where high canal flare index has also been linked to osseointegration failure and implant loosening. On the other hand, lower canal flare index (corresponding to the Dorr type C) is more prevalent in the elderly population and increases late periprosthetic fracture rates and stress shielding. Even the most commonly used cementless femoral stems cannot offer optimal fit to intra-/extramedullary geometry or offset restoration in up to 30% of clinical cases. Femoral morphology can have significant impact on post-operative LLD and osseointegration of cementless THA. Quantitative measurements of the proximal femoral canal may improve the choice of a particular implant and fixation method.

BackgroundThe pelvic and femoral morphology are associated with the occurrence of early periprosthetic femoral fractures (PFFs) in cementless total hip arthroplasty (THA). Differences exist depending on the performed approach and implanted stem design. Therefore, this study was conducted to analyze the pelvic and femoral morphology in cementless short stem THA via a minimally-invasive (MIS) anterolateral approach.MethodsA retrospective, single-center, multi-surgeon, comparative propensity-score matched study of a cohort of 1826 short stem THAs was conducted. A total of 39 PFFs within the first 90 days after surgery was matched on a 2:1 ratio to non-fracture patients. The morphology of the proximal femur was analyzed with canal flare index (CFI), canal-calcar ratio (CCR), canal-bone ratio (CBR), morphological cortical index (MCI), and femoral cortical index (CI). The pelvic morphology was analyzed with ilium–ischial ratio (IR), distance anterior superior iliac spine to the tip of the greater trochanter (AGT). Both groups were analyzed regarding several parameters for femoral and pelvic morphology in non-parametric testing and univariate regression analysis.ResultsA significantly higher AGT was detected in the fracture group (104.5 mm ± 18 versus 97.4 mm ± 9.8; p = 0.016). All other femoral and pelvic parameters did not differ between both groups, also when compared depending on the Vancouver type of the PFF.ConclusionsThe morphology of the proximal femur and the pelvis do not differ in several radiological parameters in patients sustaining a PFF in cementless short stem THA via an anterolateral approach compared with matched non-fracture group. The findings are controversial to other studies with different stem types and approaches. Future studies should focus on analyzing the influence of the pelvic geometry and the shape of the proximal femur in the occurrence of PFFs in different approaches with the same stem type and vice versa.Level of Evidence Level III case-controlled study

Does Femoral Morphology Predict the Risk of Periprosthetic Fracture After Cementless Total Hip Arthroplasty?

BackgroundThe occurrence of periprosthetic femoral fractures (PFFs) in cementless total hip arthroplasty (THA) might be associated with the proximal femoral morphology and the pelvis. PFFs in short stem THA are associated with an increased Canal Flare Index. PFFs in straight stem THA show a decreased Canal Flare Index. Therefore, this study aims to compare the femoral and pelvic geometry in PFFs between short stem and straight stem THA.MethodsA retrospective comparative propensity-score matched study was performed. An institutional database of 5358 THAs was screened for early PFFs within the first 90 days after surgery. All cases of 136 PFFs in primary cementless THA were collected and matched, resulting in 67 PFFs in the straight stem and 37 PFFs in the short stem group. Both groups were analyzed regarding several parameters for femoral and pelvic morphology.ResultsA significantly lower distance from the anterior superior iliac spine to the greater trochanter (AGT) was detected in the straight stem group (96.4 vs. 104.8 mm, p = 0.024). All other femoral and pelvic parameters did not differ between both groups. Postoperative Vancouver A PFFs were significantly higher in straight stem THA, while postoperative Vancouver B PFFs were significantly higher in short stem THA.ConclusionThe morphology of the proximal femur and the pelvis do not differ in several radiological parameters in patients sustaining a PFF between cementless short stem implanted via an anterolateral approach and straight stem THA implanted via a transgluteal approach. While there are differences in the Vancouver types of PFFs, these differences do not reflect any difference in the morphology of the proximal femur and the pelvis.

Introduction: Accurate preoperative planning for cementless total hip arthroplasty (THA) requires precise assessment of proximal femoral morphology to ensure implant stability and long-term survival. This study aimed to evaluate the variability of proximal femoral morphology using computed tomography (CT)-based morphometry and to determine its clinical relevance in selecting the appropriate type of femoral prosthesis. Materials and methods: A retrospective analysis was performed on 99 patients (58 men, 41 women; mean age 61 ±6.6 years) who underwent lower-limb CT angiography between 2017–2019. Patients with a history of trauma, congenital or degenerative deformities were excluded. Radiological parameters assessed included: femoral length (relative and absolute), neck-shaft angle, canal flare index (CFI), Dorr classification, and femoral torsion angles (angle of varus deformity of the femur, angle of posterior convexity of the proximal femur and angle of anterior convexity of the middle part of the femur). Statistical analysis was conducted using Statistica 13.0 with significance set at p ≤ 0.05. Results: No statistically significant differences were found between right and left femur across all parameters. The mean relative femoral length was 44.6 ±3.0 cm, neck-shaft angle 127.3 ±5.0°, and mean CFI 4.53 ±0.59. Dorr type B morphology predominated (68%), followed by types A (19%) and C (13%). Males had significantly longer femur (p &lt; 0.001), while CFI correlated positively with age (r = 0.38; p &lt; 0.05). Conclusions: Proximal femoral morphology demonstrates high interindividual variability but no relevant side-to-side asymmetry. Computed tomography-based 3D assessment enhances the accuracy of preoperative planning and may help in selecting the optimal prosthesis for cementless hip arthroplasty.

To investigate the effect of different proximal femoral shapes on leg length discrepancy(LLD) after total hip arthroplasty(THA). Total 131 patients with osteoarthritis or osteonecrosis received unilateral biological total hip arthroplasty from June 2013 to June 2019. All patients' age, sex, side and pelvis anteroposterior digital radiography were retraspectively analyzed. There were 69 males and 62 females, 57 cases of left hip and 74 cases of right hip. The age ranges from 25 to 89 with an average age of 62 years. There were 48 cases of osteoarthritis and 83 cases of osteonecrosis. In this study, femoral cortical index (FCI) was used as the classification of proximal femoral shape, and bilateral lower limb length differences were measured by preoperative and postoperative pelvis anteroposterior digital radiography. Grouping according to FCI:> 0.6 was Dorr A group, 0.5 to 0.6 was Dorr B group, <0.5 was the Dorr C group, and the relationship between proximal femur morphology and the leg length discrepancy after total hip arthroplasty was determined. The postoperative average FCI was(0.56±0.08) mm and the median LLD was 5.10 mm (IQR -1.00 to 8.80 mm). Three groups were divided according to the level of FCI, and there were no statistically significant differences in gender, age, side, diagnosis and intraoperative fracture rate distribution among three groups. FCI>0.6, the postoperative LLD was 6.30 mm (IQR 1.00 to 10.95 mm). When FCI was 0.5 to 0.6, the postoperative LLD was 5.85 mm(IQR-0.55 to 8.90 mm). FCI<0.5, the postoperative LLD was 1.95 mm(IQR -2.50 to 6.68 mm). LLD comparison of different proximal femoral shape was statistically significant (P<0.05). High FCI increases the risk of lower extremity prolongation after surgery on the affectedside, while low FCI reduces the risk of lower extremity prolongation after surgery on the affected side. The surgeon can assess the shape of the proximal femur of the patient preoperatively and inform the patient in advance of possible changes in leg length of both lower extremities after total hip replacement.

To explore the related factors of femoral stem anteversion (FSA) after total hip arthroplasty (THA), so as to provide reference for clinical design of FSA before operation and reduce the risk of hip dislocation after arthroplasty. Ninty-three patients (103 hips) who underwent THA between October 2021 and September 2022 and met the selection criteria were selected as the study subjects. Among them, there were 48 males and 45 females with an average age of 58.5 years (range, 25-88 years). Body mass index was 18.00-37.84 kg/m 2, with an average of 24.92 kg/m 2. There were 51 cases (57 hips) of osteonecrosis of femoral head, 35 cases (39 hips) of hip osteoarthritis, and 7 cases (7 hips) of congenital hip dysplasia. Based on CT images, the following indicators were measured: preoperative femoral neck anteversion (FNA), preoperative femoral rotation angle (FRA), preoperative acetabular anteversion (AA), and preoperative combined anteversion (CA; the sum of preoperative FNA and AA); postoperative FSA and the change in femoral anteversion angle (the difference between postoperative FSA and preoperative FNA). Based on preoperative X-ray films, the following indicators were measured: femoral cortical thickness index (CTI) and canal flare index (CFI), the proximal femoral medullary cavity was classified according to Noble classification (champagne cup type, normal type, chimney type), neck-shaft angle (NSA), and femoral offset (FO). Pearson correlation analysis, one-way ANOVA, and Point-biserial correlation analysis were used to investigate the correlation between postoperative FSA, postoperative change in femoral anteversion angle, and patient diagnosis, proximal femoral medullary cavity anatomy type, gender, age, as well as preoperative FNA, FRA, AA, CA, NSA, FO, CTI, and CFI. FSA was used as the dependent variable and the independent variables that may be related to it were included for multiple linear regression analysis. Based on CT image measurement, preoperative FNA was (15.96±10.01)°, FRA (3.36±10.87)°, AA (12.94±8.83)°, CA (28.9±12.6)°, postoperative FSA (16.18±11.01)°, and postoperative change in femoral anteversion angle was (0.22±9.98)°. Based on preoperative X-ray films measurements, the CTI was 0.586±0.081; the CFI was 4.135±1.125, with 23 hips classified as champagne cup type, 68 hips as normal type, and 12 hips as chimney type in the proximal femoral medullary cavity anatomy; NSA was (132.87±7.83)°; FO was (40.53±10.11) mm. There was no significant difference between preoperative FNA and postoperative FSA ( t=-0.227, P=0.821). Pearson correlation analysis showed that postoperative FSA was positively correlated with preoperative FNA, preoperative CA, postoperative change in femoral anteversion angle, and age ( P<0.05), while negatively correlated with preoperative FRA ( P<0.05). The postoperative change in femoral anteversion angle were positively correlated with preoperative FRA and postoperative FSA ( P<0.05), and negatively correlated with preoperative CA and FNA ( P<0.05). One-way ANOVA analysis showed that the above two indicators were not correlated with diagnosis and the proximal femoral medullary cavity anatomy type ( P>0.05). Multiple linear regression analysis showed a linear correlation between FSA and FNA, CA, age, and FRA ( F=10.998, P<0.001), and the best fit model was FSA=0.48×FNA-2.551. The factors related to FSA after THA include patient's age, preoperative FNA, CA, FRA and postoperative femoral anteversion, of which preoperative FNA is the most closely related. When designing a surgical plan before surgery, attention should be paid to the patient's preoperative FNA, and if necessary, CT around the hip joint should be scanned to gain a detailed understanding of the proximal femoral anatomical structure.

Objective To analyze the conditions of hip prosthesis reconstruction and to probe into the relationship of the life quality and the safe range of the prosthesis position parameters. Methods Based on a prospective study design, from March 2013 to March 2015, 52 eligible patients (52 hips) who had had total hip arthroplasty were interviewed and measured by the short form 36-item health survey (SF-36) before and two years after the operation. The anteroposterior pelvis, anteroposterior and lateral hip joint X-rays were taken at the third day after the operation to analyze the prosthesis position parameters of acetabulum and the femoral prosthesis, including acetabulum abducent and anteversion angles, femoral head rotation center position, femoral eccentricity, femoral vertical setover, length of abductor and gravity lever arm, femoral prosthesis varus and valgus, neck shaft angle. SF-36 was used to evaluate the patient′s quality of life before and two years after the operation. SPSS 17.0 was applied to analyze the reliability and validity of SF-36 and evaluate the relationship between quality of life and prosthesis position parameters after cementless total hip arthroplasty by Pearson analysis and t test. Results All the patients (52 hips) completed the follow-up, and prosthesis position parameters were obtained from X-ray after THA. Except role emotional (RE), the internal consistency of before and after opration of SF-36 determined by Cronbach's alpha coefficient were greater than 0.7. Test-retest reliability of SF-36 expressed by intraclass corre-lation coefficient(ICC) were greater than 0.80. The half-split reliability expressed by Pearson correlation coefficient(CC) was greater than 0.874. The validity was good at showing the life quality changes of patients before and after the surgery. Except vitality(VT), content validity evaluated by Pearson CC were higher than 0.7 between most dimensions and items of SF-36. CC between the prosthesis position parameters and the items of SF-36 were positive value. Except general health(GH), CC between the items of SF-36 and acetabulum prosthesis position parameters were greater than 0.6, and highly relevant between the items of SF-36 and femoral head rotation center position; CC were greater than 0.7 between femoral vertical setvover and VT, social function(SF), RE and mental healt(MH), the same to femoral eccentricity; CC were larger than 0.8 between length of abductor and gravity lever arm and SF and MH, the left data were greater than 0.7; CC between femoral prosthesis and items of SF-36 ranged from 0.329 to 0.757; CC between the items of SF-36 and neck shaft angle were greater than 0.7. Conclusions SF-36 has good reliability and validity so that they can be used to evaluate the quality of life for THA patient. The life quality of patients with femoral neck fracture is lower than normal, while it can get much better after the operation. SF-36 can reflect the patient's psychological, physiological and social life of quality of life. The suitable range of acetabulum abducent and anteversion angles are (45±5)° and (15±5)°. The neck shaft angle should be kept in (125±10)°. Acetabulum prosthesis should be placed in the acetabulum anatomy, and the contralateral normal side as reference to rebuild femoral head rotation center position. The length of the operated hip joint is shorter than the contralateral side, which should not be more than 10 mm. Shortening of femoral eccentricity, length of abductor and gravity lever arm should be avoided, and femoral prosthesis shall be kept at neutral position. Key words: Bioprosthesis; Arthroplasty, replacement, hip; Quality of life

BackgroundLittle scientific evidence exists on blood loss and transfusion rates depending on the fixation technique. The hypothesis of this study was that the blood loss and transfusion rate are lower in cemented and hybrid total hip arthroplasty (THA) compared to cementless THA.MethodsWe retrospectively compared a total of 1500 patients who received either cementless, cemented, hybrid or reverse hybrid THA. All patients underwent THA in 2021 at a single orthopedic center in Germany.ResultsThe lowest blood loss was found in patients who received a fully cemented THA (695 ± 74 ml). Hybrid THA with a cemented stem showed a blood loss of 845 ± 30 ml and reverse hybrid THA showed the highest blood loss with an average of 994 ± 74 ml. Cementless THA caused an average blood loss of 957 ± 16 ml. There was a significant difference between cementless THA, hybrid THA (cemented stem), and fully cemented THA (p < 0.05). Transfusion rates ranged from 1.3% (cementless THA) to 7.9% (cemented THA) between the groups with a transfusion rate of 2.5% overall.ConclusionWe found significantly lower blood loss in cemented THA and hybrid THA compared to cementless THA. Although blood loss was lower in cemented and hybrid THA, this did not result in lower transfusion rates. This could be due to other confounders such as age, comorbidities, and preoperative anemia.

Risk Factors for Periprosthetic Femoral Fractures After Cementless Total Hip Arthroplasty

BackgroundThis study aimed to 1) assess the effect of total hip arthroplasty (THA) on coronal limb alignment, namely, the hip–knee–ankle angle (HKA), 2) identify factors that determine changes in the HKA, and 3) determine whether alignment changes influence the knee joint space width.MethodsWe retrospectively evaluated 266 limbs of patients who underwent THA. Three types of prostheses with neck shaft angles (NSAs) of 132°, 135°, and 138° were used. Several radiographic parameters were measured in the preoperative and final radiographs (at least 5 years after THA). A paired t-test was used to confirm the effect of THA on HKA change. Multiple regression analysis was performed to identify radiographic parameters related to HKA changes following THA and changes in knee joint space width. Subgroup analyses were performed to reveal the effect of NSA change on the HKA change, and the proportion of total knee arthroplasty usage and changes in radiographic parameters between maintained joint space and narrowed joint space groups were compared.ResultsThe preoperative mean HKA was 1.4° varus and increased to 2.7° varus after THA. This change was related to changes in the NSA, lateral distal femoral angle, and femoral bowing angle. In particular, in the group with a decrease in NSA of > 5°, the preoperative mean HKA was largely changed from 1.4° varus to 4.6° varus after THA. The prostheses with NSA of 132° and 135° also led to greater varus HKA changes than those with an NSA of 138°. Narrowing of the medial knee joint space was related to changes in the varus direction of the HKA, decrease in NSA, increase in femoral offset.ConclusionA large reduction in NSA can lead to considerable varus limb alignment after THA, which can have adverse effects on the medial compartment of the ipsilateral knee.

Introduction. The population of the very elderly (i.e. ≥80 years of age) is growing rapidly due to demographic changes, an increased life expectancy, in particular. As a consequence, a 170% increase in the number of performed total hip arthroplasties (THAs) is projected for the next decades. Previous studies described the age-related changes in the morphology of the proximal femur, however, almost exclusively in subjects <80 years of age and using 2D X-rays. In THA the emphasis lies on reconstruction of the center of rotation (CoR) in order to preserve leg length, leg rotation and muscle tension (more precise: lever arm). The present study focuses on the reconstruction of the center of rotation (CoR) in the very elderly, with emphasis on the neck-shaft angle (NSA), the femoral neck anteversion angle (FNAA) and the mediolateral offset (ML offset). Furthermore, the effect of patient demographics such as gender, length and weight on the internal and external morphology of the proximal femur, the relationships between dimensions and angles on the proximal femur, and the effect of the internal morphology of the femoral canal on parameters describing the external geometry of the proximal femur were investigated. Methods. Ninety very elderly subjects (avg. 84.2 ± 3.6 years, range 80-105 years, 50M/40F) got a high-resolution CT-scan of their right femur (voxel size 1x1x1mm). Cortical bone models were derived from these scans using a specialized threshold algorithm in Materialise Mimics v10 and were further processed in Inus Technology Rapidform 2006. In order to classify the proximal femoral canal shape in stovepipe, normal or champagne flute the canal flare index (CFI) was measured according to Noble et al. Results. Compared to previous studies, the mean NSA (125.1 ± 5.5) and FNAA (10.0 ± 5.6) values found in the present study did not show notable differences. Based on the coronal CFI, the studied femora can be divided into stovepipe (23.3%) and non-stovepipe (76.7%). This percentage of stovepipe shaped proximal femoral canals is high compared to literature about younger populations. There are no differences in the external geometry between femora with a stovepipe or a non-stovepipe shaped canal. Furthermore, the FHD and the CoR-LTabsolute proved to be positively correlated (r=0.449) in the current study, the CoR-LTabsolute/FHD-ratio showed to be 1.17. The distance between the lesser trochanter and the center of rotation was both absolute (59.54 ± 5.76mm vs. 54.85 ± 6.31mm) and vertical (44.37 ± 6.77mm vs. 38.95 ± 7.41mm) larger in males than in females. Discussion. Based on the current study, no alternations in the external geometry of the current hip stem have to be made for an optimal elderly hip stem. However, due to advanced osteoporosis, this population of very elderly subjects contained more stovepipe shaped proximal canals based on their CFI, than younger populations. This has implications for hip stem design in the elderly. Namely, the proximal canal in which the hip stem is fixated is widened, while the external morphology remains the same. A hip stem with a thicker part for fixating in the shaft and the same external features as the currently used hip stem seems thus optimal in the very elderly (≥80yrs). Furthermore, a new equation for determining the head height, based on the diameter of the femoral head is suggested, which may be useful in hemiarthroplasty.

What's New in Hip Replacement.

Total hip arthroplasty (THA) is the most effective surgical intervention for end-stage hip diseases, yet approximately 10-15% of patients require revision surgery due to biomechanical complications such as stress shielding and aseptic loosening. These complications stem from mechanical environment mismatch between implants and host bone, while patients exhibit substantial inter-individual variations in skeletal geometry and bone quality that standard implants cannot accommodate. This study proposes an innovative "3D Printing-Neural Network Co-modelling" (3PNN) framework to enable patient-specific preoperative biomechanical prediction and implant design optimization. First, we developed a biomimetic bone matrix material with tunable mechanical properties, achieving elastic modulus spanning the complete range from cancellous to cortical bone (0.1-20 GPa). Second, based on five key geometric descriptors (neck-shaft angle, acetabular inclination, femoral anteversion, canal flare index, and cortical thickness index), we established a parametric pelvis-femur model and generated 95 models covering patient diversity through Latin hypercube sampling. Subsequently, we fabricated this biomimetic bone model library using multi-material 3D printing and measured stress distributions after standard prosthesis implantation via digital image correlation (DIC), acquiring 120 high-quality experimental datasets. Based on these data, we trained a bidirectional 3PNN machine learning framework: Forward-3PNN rapidly predicts stress distribution from geometric parameters (R²=0.89, MAPE=9.2%), while Inverse-3PNN inversely infers bone quality from mechanical response (r=0.87 vs DXA). Parametric sensitivity analysis revealed that neck-shaft angle and canal flare index are the most critical factors influencing stress distribution. In validation with 42 retrospective clinical cases, this framework successfully guided personalized implant selection and identified high-risk patients. By integrating the fidelity of physical models with the efficiency of machine learning, this study provides a novel paradigm for personalized medical device design and digital twin healthcare systems, demonstrating significant clinical translational value and design innovation insights.