Neck Axis Research Articles

Biomechanical analysis of recently released cephalomedullary nails for trochanteric femoral fracture fixation in a human cadaveric model.

Recently, two novel concepts for intramedullary nailing of trochanteric fractures using a helical blade or interlocking dualscrews have demonstrated advantages as compared to standard single-screw systems. However, these two concepts have not been subjected to a direct biomechanical comparison so far. The aims of this study were to investigate in a human cadaveric model with low bone quality (1) the biomechanical competence of nailing with the use of a helical blade versus interlocking screws, and (2) the effect of cement augmentation on the fixation strength of the helical blade. Twelve osteoporotic and osteopenic human cadaveric femoral pairs were assigned for pairwise implantation using either a short TFN-ADVANCED Proximal Femoral Nailing System (TFNA) with a helical blade head element or a short TRIGEN INTERTAN Intertrochanteric Antegrade Nail (InterTAN) with interlocking screws. Six osteoporotic femora, implanted with TFNA, were augmented with bone cement. Four groups were created: group 1 (TFNA) paired with group 2 (InterTAN), both consisting of osteopenic specimens, and group 3 (TFNA augmented) paired with group 4 (InterTAN), both consisting of osteoporotic specimens. An unstable trochanteric AO/OTA 31-A2.2 fracture was simulated and all specimens were tested until failure under progressively increasing cyclic loading. Stiffness in group 3 was significantly higher versus group 4, p = 0.03. Varus (°)and femoral head rotation around the femoral neck axis (°) after 10,000 cycles were 1.9 ± 1.0/0.3 ± 0.2 in group 1, 2.2 ± 0.7/0.7 ± 0.4 in group 2, 1.5 ± 1.3/0.3 ± 0.2 in group 3 and 3.5 ± 2.8/0.9 ± 0.6 in group 4, being significantly different between groups 3 and 4, p = 0.04. Cycles to failure and failure load (N) at 5° varus or10° femoral head rotation around the neck axisin groups 1-4 were 21,428 ± 6020/1571.4 ± 301.0, 20,611 ± 7453/1530.6 ± 372.7, 21,739 ± 4248/1587.0 ± 212.4 and 18,622 ± 6733/1431.1 ± 336.7, being significantly different between groups 3 and 4, p = 0.04. Nailing of trochanteric femoral fractures with use of helical blades is comparable to interlocking dualscrews fixation in femoral head fragments with low bone quality. Bone cement augmentation of helical blades provides significantly greater fixation strength compared to interlocking screws constructs.

Radiographic Assessment of the Proximal Femoral Anatomy in An Indigenous African Adult Population

Background: Hip surgeries such as fracture fixation, corrective osteotomy, hemiarthroplasty, or total hip arthroplasty require accurate preoperative templating for a successful outcome. Such templating is done using the proximal femur and the acetabulum radiographs, depending on the planned surgery. Understanding the normal radiographic anatomy of the proximal femur is crucial to differentiate a normal from pathological anatomy. Proximal femoral anatomic indices include the femoral head diameter, femoral neck diameter, femoral neck length, femoral offset, femoral neck axis length and the femoral neck-shaft angle. Aim: This study assesses and establishes the average values of the proximal femoral anatomy in an indigenous African adult population. Method: This cross-sectional study examined 190 normal anteroposterior (AP) radiographs of the pelvis. The mean age, weight and height of the subjects were obtained. The following proximal femoral anatomic parameters were measured: femoral neck length (FNL), femoral neck diameter (FND), femoral head diameter (FHD), femoral neck-shaft angle (FNSA), femoral offset (FO) and femoral neck axis length (FNAL). The authors compared the mean difference of the parameters between the genders and the age categories and assessed the parameter correlations with the patients’ weight and height. Results: Males constituted 63 (33.2%) of the study population. The mean age of the subjects was 51.46 years (SD = 16.37). The mean weight was 76.13 kg, while the mean height was 1.62 m. The mean values of the proximal femoral parameters were as follows: FNL 4.52cm, FND 3.42cm, FHD 4.76cm, FNSA 132.960, FO 4.09cm, and FNAL 10.34cm. Males have a significantly higher mean value in all the parameters except the FO. None of the parameters showed any significant difference among the age categories except the FNL. A post-hoc analysis showed that the difference in the FNL lies between the young and the elderly age groups. The subjects’ height correlated with all the parameters except FNSA, while the weight correlated with the FND, FNSA and FNAL. Conclusion: The proximal femoral anatomy in Africans differed from those published in foreign literature. This knowledge is crucial for implant manufacturing companies and preoperative templating for hip surgeries. KEY WORDS: Proximal femur, Anatomy, Black population.

Three dimensional CT analysis of the change in rotational alignment in double level osteotomy after double level osteotomy performed for varus osteoarthritic knees

PurposeTo analyze the change in rotational alignment caused by double level osteotomy (DLO) based on comparative three-dimensional image analysis of pre- and postoperative CT images. MethodsPre- and postoperative CT examination of the lower extremities were performed with informed consent for 39 consecutive knees undergoing DLO for varus knee deformity. The DLO procedure consisted of closed wedge distal femoral osteotomy (CWDFO) and open wedge high tibial osteotomy (OWHTO). Among those cases, 20 knees complicated with hinge fracture at the osteotomy site were excluded from the analysis to eliminate a confounding factor affecting the results. Consequently, data obtained from 19 knees were subjected to the study analysis while osteotomies with hinge fractures complications were excluded from the study. In the three-dimensional CT image analysis of axial plane images, femoral torsion (the angle between midline along the femoral neck axis and the tangent of the posterior edges of the medial/lateral femoral condyles) and tibial torsion (the angle between the tangent of the posterior edges of the medial/lateral tibial condyles and the transmalleolar axis) were measured. The torsion angle was measured in each of the femurs and the tibias on both pre- and postoperative CT axial images, and the change induced by the osteotomy was calculated and statistically(using Wilcoxon signed-rank test) compared. ResultsThe mean pre- and postoperative femoral torsion (anteversion) angles were 29.3° and 31.4° with a significant postoperative increase in internal rotation of the bony segment distal to the osteotomy(P = 0.002). On the tibial side, the mean pre- and postoperative torsion angles were 26.5° and 25.7°, indicating no significant postoperative change(P = 0.199)（NS）. ConclusionsThis study showed that the DLO procedure (combining CWDFO and OWHTO) increased torsion (anteversion) of the femur by 2.1° on average while inducing no significant rotational change on the tibial side.

English

BACKGROUND The peculiar waddling gait of a female attracts most of the anatomists to measure and compare the neck-shaft angle (NSA) of the femora. The femoral neck shaft angle is greater in women due to greater pelvic breadth and shorter femur. Neck-shaft angle was measured by the angle that the neck makes with the shaft of the femur and it is measured on the ventral surface of femur taking the long axis of femoral neck with the long axis of the proximal end of the femur. It gives information about the race it belongs to and normally measures 120° to 140°. The intention of this study was to establish the femoral neck shaft angle variations in adult male and female for medico-legal and anthropometric studies. METHODS This cross-sectional study was conducted on 84 adult human femora of unknown sex in the anatomy department, Sriram Chandra Bhanja (SCB) Medical College, Cuttack, Odisha, from May 2018 to April 2019. We included all the femora which were free of damage or deformity and fully ossified indicating adult bone. Femora with any pathological changes i.e., cortical bone deterioration, extreme osteophyte activity, osteoarthritis and fracture etc. were excluded from the study. The NSA was measured by protractor and goniometer. RESULTS In the present study the NSA range for the right femur of male was 108° - 135° and for the right femur of females 117° - 135°. The left male femur was 118° - 135° and the left female femur was 120° - 135°. The mean neck shaft angle of male femora was 125.9° and the female femora was 125.7°. These measurements show that the values were more in males than the females. The value of the present study was statistically significant between male and female i.e., P < 0.0001. CONCLUSIONS These measurements are important in the medico-legal cases, reconstructive orthopaedic surgeries, hip replacement surgeries and also while constructing suitable prosthesis. This will also be helpful in the detection of sex by anatomists and forensic experts. KEY WORDS Neck Shaft Angle, Medico-Legal, Anthropometry and Goniometer

Atraumatic femoral head necrosis: a biomechanical, histological and radiological examination compared to primary hip osteoarthritis

IntroductionAtraumatic necrosis of the femoral head (AFHN) is a common disease with an incidence of 5000–7000 middle-aged adults in Germany. There is no uniform consensus in the literature regarding the configuration of the bone in AFHN. The clinical picture of our patients varies from very hard bone, especially in idiopathic findings, and rather soft bone in cortisone-induced necrosis. A better understanding of the underlying process could be decisive for establishing a morphology-dependent approach. The aim of this study is the closer examination of the condition of the bone in the AFHN compared to the primary hip osteo arthritis (PHOA).Materials and methodsThe preparations were obtained as part of elective endoprosthetic treatment of the hip joint. Immediately after sample collection, thin-slice CT of the preserved femoral heads was performed to determine the exact density of the bone in the necrosis zone. Reconstruction was done in 0.8–1 mm layers in two directions, coronary and axial, starting from the femoral neck axis. Density of the femoral heads was determined by grey value analysis. The value in Hounsfield units per sample head was averaged from three individual measurements to minimize fluctuations. For biomechanical and histomorphological evaluation, the samples were extracted in the load bearing zone perpendicular to the surface of the femoral head. Group-dependent statistical evaluation was performed using single factor variance analysis (ANOVA).ResultsA total of 41 patients with a mean age of 64.44 years were included. The mean bone density of the AFHN samples, at 1.432 g/cm3, was about 7% higher than in the PHOA group with a mean value of 1.350 g/cm3 (p = 0.040). The biomechanical testing in the AFHN group showed a 22% higher—but not significant—mean compressive strength (20.397 MPa) than in the PHOA group (16.733 MPa). On the basis of histological analysis, no differentiation between AFHN and PHOA samples was possible.ConclusionsThe present study (NCT, evidence level II) shows that AFHN has a very well detectable higher bone density compared to PHOA. However, neither biomechanical stress tests nor histomorphological evaluation did show any significant difference between the groups. The results allow the conclusion that there is no “soft” necrosis at all in the AFHN group.

Quantification of assembly forces during creation of head-neck taper junction considering soft tissue bearing: a biomechanical study

BackgroundAll current total hip arthroplasty (THA) systems are modular in design. Only during the operation femoral head and stem get connected by a Morse taper junction. The junction is realized by hammer blows from the surgeon. Decisive for the junction strength is the maximum force acting once in the direction of the neck axis, which is mainly influenced by the applied impulse and surrounding soft tissues. This leads to large differences in assembly forces between the surgeries. This study aimed to quantify the assembly forces of different surgeons under influence of surrounding soft tissue.MethodsFirst, a measuring system, consisting of a prosthesis and a hammer, was developed. Both components are equipped with a piezoelectric force sensor. Initially, in situ experiments on human cadavers were carried out using this system in order to determine the actual assembly forces and to characterize the influence of human soft tissues. Afterwards, an in vitro model in the form of an artificial femur (Sawbones Europe AB, Malmo, Sweden) with implanted measuring stem embedded in gelatine was developed. The gelatine mixture was chosen in such a way that assembly forces applied to the model corresponded to those in situ. A study involving 31 surgeons was carried out on the aforementioned in vitro model, in which the assembly forces were determined.ResultsA model was developed, with the influence of human soft tissues being taken into account. The assembly forces measured on the in vitro model were, on average, 2037.2 N ± 724.9 N, ranging from 822.5 N to 3835.2 N. The comparison among the surgeons showed no significant differences in sex (P = 0.09), work experience (P = 0.71) and number of THAs performed per year (P = 0.69).ConclusionsAll measured assembly forces were below 4 kN, which is recommended in the literature. This could lead to increased corrosion following fretting in the head-neck interface. In addition, there was a very wide range of assembly forces among the surgeons, although other influencing factors such as different implant sizes or materials were not taken into account. To ensure optimal assembly force, the impaction should be standardized, e.g., by using an appropriate surgical instrument.

A morphometric analysis for investigation climate impact on settlement in Lengkiti, Ogan Komering Ulu Regency, Indonesia

The change in morphological patterns upstream of Ogan River were investigated to analyze land-use and climate change impact on the river meandering. This study aimed to investigate morphological changes of Ogan River in Lengkiti area between 1996 and 2019. Two sets of Landsat areal (1990 and 2016) were used to identify the morphological changes during flood periods. Data analysis used the maximum likelihood approach, t-test and Spearman correlation analysis. The morphometric indicators such as river width (W), meander neck length (L), axis length (A), curvature radius (R), water flow and sinuosity of meander (C) were extracted to identify the morphological pattern of river meandering. Analysis of land-use change used Support Vector Machine (SVM) and kernel function method to interpret the meander parameter change. Ogan River in Lengkiti, such as Batu Kuning and Marga Jaya segments, which have rice field and settlement cover from 1996 to 2019, had been cut off. Cut-off occurred due to landslides that entered river’s body and narrowed riverbed. This fasted river flow even though river discharge was same, caused intensive erosion and sedimentation. The increase in water velocity increased flow power, shortened flow distance and cut-off caused reduced meander’s sinuosity (C).

Decreased complications but a distinctive fixation loosening mechanism of fully threaded headless cannulated screw fixation for femoral neck fractures in young adults

BackgroundDespite being a commonly encountered injury in orthopedic practice, controversy surrounds the methods of optimal internal fixation for femoral neck fractures (FNF) in young patients. The objective of the present study is to compare complication rates and failure mechanisms for surgical fixation of FNF using fully threaded headless cannulated screws (FTHCS) versus partial threaded cannulated screws (PTS) in young adults.MethodsA total of 75 patients (18–65 years old) with FNF were prospectively treated with close reduction and internal fixation using three parallel FTHCS and compared to a historical control case-matched group (75 patients) with FNF treated by PTS fixation. After 2 years follow-up, rates of fixation failure (including varus collapse, fracture displacement, and femoral neck shortening), nonunion, and avascular necrosis of the femoral head (ANFH) were compared between the two cohorts. The demographic, follow-up information, and radiological images were assessed by independent blinded investigators.ResultsPatient demographics and fracture patterns were similar in the two patient groups. The overall fixation failure rates were 8% (6/75) in the FTHCS cohort, which was significantly lower than the 25.3% (19/75) seen in the PTS group. Rates of nonunion and ANFH were significantly lower in the FTHCS group when compared to the PTS control group. When stratified by injury severity (high-energy vs. low-energy fractures), the rate of fixation failure was significant lower with the use of FTHCS when compared with PTS for high-energy fractures while there was no difference in the rates of nonunion or ANFH for high or low-energy fracture patterns. Unique to the FTHCS cohort was an atypical screw migration pattern with varus collapse (6/75, 8%).ConclusionsThe results show that FTHCS fixation could significantly reduce the complication rate of young patients with FNF, especially in high-energy fracture patterns (Garden III–IV, Pauwels III, or vertical of the neck axis (VN) angle ≥ 15°). There was also confirmation that the modes of fixation loosening in the FTCHS group, including screw “medial migration” and superior cutout, were different from the screw withdrawal pattern seen in the PTS cohort.Trial registrationThe study was retrospectively registered at www.Chictr.org.cn (ChiCTR-IPR-1900025851) on September 11, 2019.

Femoral Head-Neck Translation Ratio Is a Measurement of the True Deformity of Slipped Capital Femoral Epiphysis.

A new method to quantify proximal femoral head-neck deformity in slipped capital femoral epiphysis (SCFE) is presented. In SCFE the femoral head slips posteriorly and inferiorly relative to the femoral neck. The distance of the femoral head center from the femoral neck axis (center-axis distance, CAD) represents the severity of the post-slip deformity. CAD is calculated on the anteroposterior and the frog-lateral pelvis views. It is shown that CAD is only a function of the femoral head-neck offset difference on both sides of the femoral neck. The percentage of CAD relative to the diameter of femoral neck is the femoral head-neck translation ratio (FHNTR) on the respective x-ray projection. Measurements on radiographs of 37 patients with history of unilateral SCFE were performed. The asymptomatic contralateral hips were used as controls. On the anteroposterior pelvis view, mean FHNTR was -12.2% and -4.3% for the affected and asymptomatic contralateral hips, respectively (paired t-test, p < .01), indicating inferior translation of the femoral head relative to the femoral neck. On the frog-lateral view, mean FHNTR was -21.1% and -6.5% for the affected and the contralateral hips, respectively (paired t-test, p < .01), indicating posterior translation of the femoral head relative to the femoral neck. There is a moderate inverse correlation between FHNTR on the frog-lateral pelvis view and Southwick's slip angle (Pearson correlation coefficient r = -0.679, p < .001). FHNTR on two radiological planes (anteroposterior and frog-lateral) is a simple measurement of the posteroinferior translation of the femoral head relative to the femoral neck in SCFE. It is a measurement of the true deformity of the proximal femur in SCFE. Calculation of FHNTR may be applicable to classify SCFE, to monitor femoral head-neck remodeling after slip stabilization, to describe the femoral head-neck relation in healthy individuals, and to monitor femoral head-neck changes secondary to other hip pathology, such as Perthes disease or developmental dysplasia of the hip.

Alterations in femoral neck strength following pelvic irradiation. A finite element analysis of simulated eccentric forces using bone density data derived from CT.

Radiotherapy is known to produce long-term skeletal complications. We aim to evaluate the biomechanical effect on femoral neck bone from hypothetical eccentric loads on pre- and post-radiotherapy CT-images for patients treated for rectal cancer. Pre- and post-radiotherapy CT-images of rectal cancer from 10 patients were selected randomly. The cortical and trabecular bone was segmented by hand. The biomechanical simulations of 4 eccentric loads and one load aligned with the femoral neck axis were completed using finite element analysis (FEA) in both pre- and post-patient models. A comparative statistical study was completed of pre- and post-radiotherapy patient models of stress and displacement factors. Significant differences were found in eccentric loads in both factors. Natural load has a significant difference in stress, but no differences were found for displacements. The absolute difference in eccentric load applied to the anterior area location on the same patient implies from 5.3% to 40.5% of the stress yield values reported in previous studies. Loads applied to the anterior area of the femoral head must be considered in fracture simulations because the percentage of yield stress of pre- and post-irradiated bones shows a significant biomechanical change.

Femoral Torsion in CT: Why We Should Add Some Trigonometry

Purpose: In our department, we routinely perform Computed Tomography (CT) or Magnetic Resonance Imaging (MRI) of the lower extremity to assess femoral torsion for preoperative planning prior correcting osteotomies. It might be difficult to assess the FA, because on axial images the depicted part of the femoral neck is too short to allow correct alignment of the axis of the femoral neck. Measurements can also be performed on oblique axial images with improvement of depiction of the femoral neck but are smaller than those of measurements on axial images, due to the fact that images depend on rules of trigonometry. The aim is to provide a trigonometrical formula to calculate the value for FA, allowing precise assessment of femoral anteversion on oblique axial images similar to those on axial images. Materials and Methods: Trigonometrical transformation is performed in three steps. Initial measurement of femoral anteversion on oblique images is transformed via a corresponding rectangular triangle from coronal images to calculated femoral anteversion on axial images. Results: The first triangle is labelled with a1, b1, c1 for the sides and alpha1, beta1for the angles. Second and third triangle is labelled correspondingly. Length of both cathetus a1 and b1 are calculated as follows: cathetus a1=sin alpha1*c1 and cathetus b1=cos alpha 1*c1. Cathetus b2 is calculated as follows: b2=cos alpha2*c2. alpha3=tan-1 (a3/b3). Initial calculation of angle alpha3=tan-1 (a3/b3)=tan-1 (a1/b2), with a3=a1=sin alpha1*c1 and b3=b2=cos alpha2*b1*c, with b1=cos alpha1*c1 and b3=cos alpha2*cos alpha1*c1². The final formula is then: alpha3=tan-1 ((sin alpha1*c1)/(cos alpha²*cos alpha1*c12)) = tan-1 ((sin alpha1/(alpha2*cos alpha1*c1)) Conclusion: In this study we can provide a formula: alpha3=tan-1 ((sin alpha1/(cos alpha2*cos alpha1*c1)), which allows to calculate the femoral anteversion for true axial reconstructed images with the increased accuracy of measurements on oblique images and the ability to use the already known reference values from the literature.

Multiple Regression Analysis of Hip Fracture Risk Assessment Via Finite Element Analysis

Abstract An accurate assessment of hip fracture risk requires a proper consideration of parameters affecting the fracture. In general, hip fracture is assessed based on bone mineral density (BMD) and load amount, but hip fracture is an outcome of the interaction of the parameters such as loading directions, bone density, which are often disregarded. Assessing the effect of the parameters individually may not correctly reflect the root cause of the hip fracture. Hence, this research aims at analyzing the significance of parameters and their interaction in assessing the fracture risk. A multiple regression analysis has been conducted considering bone density (ρash), different loading directions during sideways fall, represented by load angle (α) about femoral shaft on the coronal plane and angle (β) about femoral neck (FN) axis on the transverse plane as independent parameters and fracture risk index (FRI) as a dependent parameter. The statistical results showing the significant value of 0.7321 for α, and 0.0001 for β and ρash indicate that the effect of loading direction (α) does not have impact on fracture risk in comparison with the loading direction (β) and ρash. Furthermore, the analysis of the interaction of parameters shows that the impact of β on fracture risk may depends more on bone density.

Measuring 3D growth plate shape: Methodology and application tocam morphology.

Physeal changes corresponding to cam morphology are currently measured using two-dimensional (2D) methods. These methods are limited by definitions of the femoral neck axis and head center that are dependent on the radiographic plane of view. To address these limitations, we developed three-dimensional (3D) methods for analyzing continuous growth plate shape using magnetic resonance imaging scans. These new methods rely on a single definition of the femoral neck axis and head center that are both nondependent on the radiographic plane of view and allow for analysis of growth plate shape across the growth plate surface (performed using statistical parametric mapping). Using our 3D method, we analyzed the position of the growth plate in the femoral head (relative to a plane tangent to the femoral head) and the curvature of the growth plate (relative to a plane through the center of the growth plate) in 9-16-year-old males at risk for cam morphology and their recreationally active peers (n = 17/cohort). These two measurements provide an avenue to separately analyze the effects of these variables in the overall growth plate shape. We detected differences in growth plate shape with age in recreationally active adolescents but did not detect differences between at risk and recreationally adolescents.

Femur deformity correction planning in sagittal plane using mechanical axis

Recently, deformity correction planning using reference lines and angles is a standard procedure. At the same time, both anatomical and mechanical axes are used for the frontal plane. However, until nowadays, there was no algorithm for planning femoral deformity correction in the sagittal plane based on the mechanical axes of the bone fragments. The aim of this study was to develop a method of femur deformity correction planning in the sagittal plane based on mechanical axes. Materials and Methods: On the basis of computer tomography data of 23 adults with nondeformed femurs, we measured the angular relationships between the anatomical axis of the proximal femur in sagittal plane and mechanical axis (∠maj) and the angular relationships between the femoral neck axis and mechanical axis in sagittal plane (∠laj). Results: It was found that ∠maj was 16.0° ±7.6°, and ∠laj was 10.2° ±2.4°. Based on the data obtained, we developed a method for planning the correction of femoral deformities in the sagittal plane. According to this method, the mechanical axis of the proximal bone fragment can be determined using any of three options: (1) “Joint line based.” In this method, the proximal joint line of the femur is drawn, then from the center of the femur head with the angle 85° (mean value of mPPFA) to this line is drawn a line that is mechanical axis; (2) “Femoral neck based.” The neck axis is drawn first, then from the center of the femur head with the angle 16° (mean value ∠maj) to this line is drawn a line that is mechanical axis; and (3) “Anatomical axis based.” First, the anatomical axis of the proximal femur is drawn, then a line parallel to the anatomical axis from the center of the femoral head is drawn, then a line at an angle of 10° (mean value ∠laj) to it is drawn, that is the mechanical axis. Determination of the mechanical axis of the distal fragment in sagittal plane is made by the following: the distal joint line is drawn and divided into five equal segments. Then, the point located on the border of the front 2/5 and the rear 3/5 of the segment is found. From that point, at an angle of 81° (mean mPDFA), a mechanical axis of the distal femur fragment is drawn. The intersection of the mechanical axes of the proximal and distal fragments defines the apex of the deformity. Conclusion: The proposed method for planning deformity correction based on mechanical axes for the sagittal plane complements the existing planning methods for the frontal plane and improves the quality, namely the accuracy of preoperative planning.

The hip asphericity angle: a novel angle for measurement of Cam-FAI correction

Abstract The alpha angle is routinely used for the diagnosis and quantitative description of the Cam deformity of the hip. However, a reliable identification of the femoral neck axis as its reference line can be difficult. Moreover, most cam resections include a reduction of the femoral neck diameter with an automatic posteromedial angulation of the femoral neck axis. In consequence, the reference axes for the pre- and postoperative alpha angles are different, and a comparison of both angles underlies a systematic error to relatively higher postoperative alpha angles. In order to avoid this systemic error, we propose the hip asphericity (HA) angle with a reference axis independent of the amount of bony resection. Two retrospective groups were formed, a ‘femoroacetabular impingement (FAI) group’ that had hip arthroscopy for cam resection and a ‘Control group’ without cam deformity. The alpha and HA angles were measured by three examiners. The measurements were repeated 1 month later. In the FAI group, offset correction was calculated using both angles. Statistically significant differences for both the alpha and the HA angles were found between the control and the preoperative FAI group as well as between the preoperative and postoperative FAI groups. The HA angle-correction by a mean of 27.5° was significantly higher in comparison to the alpha angle correction by a mean of 25.4°. The intertester and intratester reliability of both angles were not significantly different. The HA angle is a new and reliable radiographic parameter for measuring cam deformity and proves superior in measuring cam correction.

Talar neck angle correlates with tibial torsion-Guidance for 3D and 2D measurements in total ankle replacement.

Axial plane alignment of the talar component in total ankle arthroplastyis poorly understood and remains a major issue, especially since malpositioning results in increased peak pressure and rotational torque. Further profound knowledge regarding individual anatomy of the talus and its relation to proximal and distal osseous structures is therefore needed. Therefore, three-dimensional (3D) surface models of 50 lower extremities were generated using computed tomographydata of patients without ankle osteoarthritis. The talus neck torsion was measured using a novel 3D measurement method. Then, tibial torsion and subtalar joint axis orientation were measured and correlated to the talus neck torsion. Moreover, a 2D measurement method of the talus neck torsion was developed. A statistically significant correlation was found between external tibia torsion and medial talus neck torsion, as well as talus neck axis and subtalar joint axis in the transversal and frontal plane. The novel defined 3D measurement methods indicated excellent inter-rater and intra-rater reliability. The 2D measurement method of the talus neck torsion was in good agreement with the 3D method. The results showed that the rotational profiles of the tibia, talus, and adjacent joints are interconnected, which should be considered in total ankle replacement (TAR). Clinical relevance: This study improves the overall understanding of the talar anatomy, as well as its relationship to adjacent osseous structures. The novel 2D measurement method of the talus neck torsion might improve talar component positioning in the axial plane corresponding to the patient's individual anatomy, and therefore improve the survival rate of TAR.

Characteristics of Femoral Torsion Angles and Relationships Between Femoral Torsion Angles and Hip Rotational Motion Variables in Adult Baseball Players

Background:Abnormalities in hip rotational motion (HRM) are risk factors for throwing injuries. To evaluate hip rotational motion, it is necessary to assess the torsion angle. However, no studies have investigated the femoral torsion angle (FTA) in baseball players.Purpose:To investigate differences in hip FTA of adult baseball players through use of ultrasonography to evaluate the relationship between the FTA and HRM.Study Design:Cross-sectional study; Level of evidence, 3.Methods:A total of 149 elite male baseball players (mean age, 20.0 ± 1.8 years; 64 pitchers, 85 position players) were enrolled in this study. Ultrasonographic assessment of FTA was performed based on the tilting angles of the anterior surface of the femoral neck and condylar axis. The hip internal rotation (HIR) and hip external rotation (HER) were assessed at 0° and 90° of flexion. Data related to FTA and HRM were compared between hips and between pitchers and position players.Results:No significant difference was observed in the FTAs between hips for any player (lead hip, 20.5° ± 9.2°; trail hip, 19.6° ± 9.8°; P = .276). No significant difference was observed in FTAs of both hips between pitchers and position players (lead hip, 20.1° ± 9.4° and 20.9° ± 9.0°, respectively, P = .957; trail hip, 19.5° ± 9.8° and 19.7° ± 9.8°, P = .999). In terms of HER in 90° of hip flexion in both hips, significant differences were observed in HRM variables between pitchers and position players (lead hip, 33.0° ± 8.9° and 37.5° ± 9.8°, respectively, P = .024; trail hip, 35.6° ± 9.6° and 40.4° ± 10.2°, P = .035). Linear regression analysis revealed a significant agreement between the FTA and HIR at both 0° (R = 0.298, P < .001) and 90° of hip flexion (R = 0.279, P < .001).Conclusion:Our findings indicated that FTAs were not different between the hips of elite baseball players. Abnormalities of the HRM are not caused by differences in the FTA but rather involve soft tissue tightness around the hip area or other bony morphologic factors in the hip joint.

Anatomic evaluation of the insertional footprints of the iliofemoral and ischiofemoral ligaments: a cadaveric study

BackgroundAn understanding of the insertional footprints of the capsular ligaments of the hip is important for preserving hip function and stability given the increasing number of minimally invasive hip surgeries being performed under a limited surgical view. However, it is difficult to detect these ligaments intraoperatively and many surgeons may not fully appreciate their complex anatomy. The aims of this study were to quantify the proximal and distal footprints of the iliofemoral ligament (ILFL) and ischiofemoral ligament (ISFL) and to estimate the location of the corresponding osseous landmarks on the proximal femur, which can be detected easily during surgery.MethodsTwelve hip joints from Japanese fresh frozen cadavers were used. All muscle, fascia, nerve tissue, and vessels were removed to expose the intact capsular ligaments of the hip. The length and width of the proximal and distal footprints of the ILFL and ISFL were measured and their relationship to osseous structures was evaluated, including the intertrochanteric line, femoral neck, and lesser trochanter.ResultsThe mean length of the distal medial arm of the ILFL footprint was 17.9 mm and the mean width was 9.0 mm. The mean length of the distal lateral arm of the ILFL footprint was 23.0 mm and the mean width was 9.7 mm. For the footprint of the medial arm, the insertion was in the distal third of the intertrochanteric line and that of the lateral arm was in the proximal 42% of this line. The mean distance from the lesser trochanter to the footprint of the medial arm was 24.6 mm. The mean length of the distal ISFL footprint was 11.3 mm and the mean width was 6.9 mm. The footprint of the distal ISFL was located forward of the femoral neck axis in all specimens.ConclusionsUnderstanding the size and location of each capsular ligament footprint in relation to an osseous landmark may help surgeons to manage the hip capsule intraoperatively even under a narrow surgical view. The findings of this study underscore the importance of recognizing that the distal ISFL footprint is located relatively forward and very close to the distal lateral arm footprint.

A multi-scale modelling framework combining musculoskeletal rigid-body simulations with adaptive finite element analyses, to evaluate the impact of femoral geometry on hip joint contact forces and femoral bone growth.

Multi-scale simulations, combining muscle and joint contact force (JCF) from musculoskeletal simulations with adaptive mechanobiological finite element analysis, allow to estimate musculoskeletal loading and predict femoral growth in children. Generic linearly scaled musculoskeletal models are commonly used. This approach, however, neglects subject- and age-specific musculoskeletal geometry, e.g. femoral neck-shaft angle (NSA) and anteversion angle (AVA). This study aimed to evaluate the impact of proximal femoral geometry, i.e. altered NSA and AVA, on hip JCF and femoral growth simulations. Musculoskeletal models with NSA ranging from 120° to 150° and AVA ranging from 20° to 50° were created and used to calculate muscle and hip JCF based on the gait analysis data of a typically developing child. A finite element model of a paediatric femur was created from magnetic resonance images. The finite element model was morphed to the geometries of the different musculoskeletal models and used for mechanobiological finite element analysis to predict femoral growth trends. Our findings showed that hip JCF increase with increasing NSA and AVA. Furthermore, the orientation of the hip JCF followed the orientation of the femoral neck axis. Consequently, the osteogenic index, which is a function of cartilage stresses and defines the growth rate, barely changed with altered NSA and AVA. Nevertheless, growth predictions were sensitive to the femoral geometry due to changes in the predicted growth directions. Altered NSA had a bigger impact on the growth results than altered AVA. Growth simulations based on mechanobiological principles were in agreement with reported changes in paediatric populations.

Higher stability and more predictive fixation with the Femoral Neck System versus Hansson Pins in femoral neck fractures Pauwels II.

SummaryObjectivesTo evaluate the biomechanical performance of the Femoral Neck System (FNS) versus the Hansson Pin System (Hansson Pins) with two parallel pins in a Pauwels II femoral neck fracture model with posterior comminution.MethodsForty-degree Pauwels II femoral neck fractures AO 31-B2.1 with 15° posterior wedge were simulated in fourteen paired fresh-frozen human femora, followed by instrumentation with either FNS or Hansson Pins in pair-matched fashion. Implant positioning was quantified by measuring shortest implant distances to inferior cortex (DI) and posterior cortex (DP) on anteroposterior and axial X-rays, respectively. Biomechanical testing was performed in 20° adduction and 10° flexion with simulated iliopsoas muscle tension. Progressively increasing cyclic loading was applied until construct failure. Interfragmentary femoral head-to-shaft movements were measured with optical motion tracking.ResultsCycles to 10° varus deformation were significantly higher for FNS (23007 ​± ​5496) versus Hansson Pins (17289 ​± ​4686), P ​= ​0.027. Cycles to 10° femoral head dorsal tilting (FNS: 12765 ​± ​3425; Hansson Pins: 13357 ​± ​6104) and cycles to 10° rotation around the femoral neck axis (FNS: 24453 ​± ​5073; Hansson Pins: 20185 ​± ​11065) were comparable between the implants, P ​≥ ​0.314. For Hansson Pins, the outcomes for varus deformation and dorsal tilting correlated significantly with DI and DP, respectively (P ​≤ ​0.047), whereas these correlations were not significant for FNS (P ​≥ ​0.310).ConclusionsFrom a biomechanical perspective, by providing superior resistance against varus deformation and performing in a less sensitive way to variations in implant placement, the angular stable Femoral Neck System can be considered as a valid alternative to the Hansson Pin System for the treatment of Pauwels II femoral neck fractures.Level of evidencetherapeutic, Level V.The Translational potential of this articleThe translational potential of this article is to compare the performance of the FNS with Hansson Pins in a AO 31-B2.1 fracture model featuring a 15 posterior wedge to show the implants behavior concerning the dorsal tilting tendency.