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Purpose The primary objective of this study was to quantify the variations of the medial posterior tibial slope (MPTS) and the lateral posterior tibial slope (LPTS), as well as of the medial proximal tibial angle (MPTA), and to determine the fraction of patients for which standard techniques including different alignment techniques would result in alteration of the patient’s individual posterior tibial slope (PTS) and MPTA. Furthermore, it was of interest if a positive correlation between PTS and MPTA or between medial and lateral slope exists. Methods A retrospective study was performed on CT-scans of 234 consecutively selected European patients undergoing individual total knee replacement. All measurements were done on three-dimensional CAD models, which were generated on the basis of individual CT-scans, including the hip, knee, and ankle center. Measurements included the medial and lateral PTS and the MPTA. PTS was measured as the angle between the patient’s articular surface and a plane perpendicular to the mechanical axis of the tibia in the sagittal plane. MPTA was defined as the angle between the tibial mechanical axis and the proximal articular surface of the tibia in the coronal plane. Results Analysis revealed a wide variation of the MPTS, LPTS, and MPTA among the patients. MPTS and LPTS varied significantly both interindividually and intraindividually. The range of PTS was up to 20° for MPTS (from − 4.3° to 16.8°) and for LPTS (from − 2.9 to 17.2°). The mean intraindividual difference between MPTS and LPTS in the same knee was 2.6° (SD 2.0) with a maximum of 9.5°. MPTA ranged from 79.8 to 92.1° with a mean of 86.6° (SD ± 2.4). Statistical analysis revealed a weak positive correlation between MPTA and MPTS. Conclusion The study demonstrates a huge interindividual variability in PTS and MPTA as well as significant intraindividual differences in MPTS and LPTS. Therefore, the question arises, whether the use of standard techniques, including fixed PTSs and MPTAs, is sufficient to address every single patient’s individual anatomy. Level of evidence III.

It is well-known that secular trends affect human stature and constitution, and this fact should be taken into consideration in forensic anthropology, especially in stature estimation. Recently, stature-group-specific equations have been developed to take into account these variations. The aim of the present study is to estimate living stature according to tibial length in different stature groups in a sample of Spanish adult males in order to improve the accuracy of previous equations. A cross-sectional study was conducted on a sample of 495 Spanish Caucasian participants who were randomized into two groups, the study group with 249 participants and the cross-validation group with 246 participants. Specific equations were obtained according to stature groups using the 15th and 85th percentiles as cut off points. The results showed that the coefficient of determination (R2) and standard error of estimation (SEE) were lower with the specific equations based on stature groups (R2=0.22–0.57; SEE=2.12–2.66cm) than the equation with all participants of the study group (R2 = 0.77; SEE=3.29cm). The equations were tested in the cross-validation group, whose results showed more accuracy in the equations for a stature <185.9cm (i.e., in people with short and medium statures). In conclusion, the stature-group-specific equations based on tibial lengths of Spanish adult males are more accurate for stature estimation than other equations that have been formulated in the Spanish population. In forensic settings, it is recommended to use regression equations specific to stature groups when estimating stature.

The aim of this study was to image tibio-femoral movement during flexion in the living knee. Ten loaded male Caucasian knees were initially studied using MRI, and the relative tibio-femoral motions, through the full flexion arc in neutral tibial rotation, were measured. On knee flexion from hyperextension to 120°, the lateral femoral condyle moved posteriorly 22 mm. From 120° to full squatting there was another 10 mm of posterior translation, with the lateral femoral condyle appearing almost to sublux posteriorly. The medial femoral condyle demonstrated minimal posterior translation until 120°. Thereafter, it moved 9 mm posteriorly to lie on the superior surface of the medial meniscal posterior horn. Thus, during flexion of the knee to 120°, the femur rotated externally through an angle of 20°. However, on flexion beyond 120°, both femoral condyles moved posteriorly to a similar degree. The second part of this study investigated the effect of gender, side, load and longitudinal rotation. The pattern of relative tibio-femoral movement during knee flexion appears to be independent of gender and side. Femoral external rotation (or tibial internal rotation) occurs with knee flexion under loaded and unloaded conditions, but the magnitude of rotation is greater and occurs earlier on weight bearing. With flexion plus tibial internal rotation, the pattern of movement follows that in neutral. With flexion in tibial external rotation, the lateral femoral condyle adopts a more anterior position relative to the tibia and, particularly in the non-weight bearing knee, much of the femoral external rotation that occurs with flexion is reversed.

SummaryThe rate of change in bone density was not different between peri- and post-menopausal women. Differences in rate of change were observed in bone microarchitecture, specifically cortical porosity (Ct.Po), where peri-menopausal women increased +9% per year compared with the +6% per year for post-menopausal women.IntroductionThe purpose of this study was to compare changes in bone density and microarchitecture in peri- and post-menopausal women over 6 years.MethodsPeri- (n = 26) and post- (n = 65) menopausal women were selected from the Canadian Multicenter Osteoporosis Study. Caucasian women were scanned on dual x-ray absorptiometry (DXA) and high-resolution peripheral quantitative computed tomography (HR-pQCT) at baseline and follow-up, an average 6 years later. To compare repeat scans, automated 3D image registration was conducted. At the radius and tibia, total volumetric BMD (Tt.BMD), total bone area (Tt.Ar) and cortical porosity (Ct.Po) were assessed, and finite element analysis estimated apparent bone strength.ResultsAt the tibia, the rate of change for Ct.Po and Tt.Ar was different between groups. Peri-menopausal women had a + 9% per year increase in Ct.Po, but this increase was slower for post-menopausal women at +6% per year (p = 0.049). In addition, post-menopausal women had an increase in Tt.Ar of +0.13% per year compared with a slower increase of +0.06% per year for peri-menopausal women (p = 0.017). The rate of change of density between groups was not significantly different and was approximately −1% per year at the hip by DXA, and −1% per year at the radius and −0.5% per year tibia by HR-pQCT.ConclusionThis is a 6-year prospective HR-pQCT study exploring rate of change in Caucasian peri- and post-menopausal women. The microarchitectural features represented by Ct.Po and Tt.Ar changed at a significantly different rate between groups, but group differences were not detected by density measures.

Is there a correlation between increased posterior-inferior tibial slope angle and noncontact anterior cruciate ligament (ACL) injury? Does increasing the posterior-inferior tibial slope angle increase the risk of bilateral ACL injury? A computerized relational database (Access 2007; Microsoft Inc, Redmond, Washington) was used to conduct a retrospective review of patients undergoing bilateral or unilateral ACL reconstruction surgery or treatment by a single surgeon between 1995 and 2013. Included in the study were patients with bilateral and unilateral ACL injuries and patellofemoral pain syndrome with no associated ACL deficiency. Exclusion criteria included concomitant ligament injury, previous ACL reconstruction, and previous knee surgery. Also excluded were patients who did not have plain lateral radiographs. Fifty patients were randomly selected from each group. After controlling for age and Tegner activity level, the authors found that the posterior-inferior tibial slope angle was a significant predictor ( P =.002) of noncontact ACL injury. Mean posterior-inferior tibial slope angle for the bilateral, unilateral, and control groups was 11.8°±2.3°, 9.3°±2.4°, and 7.5°±2.3°, respectively. In the group with unilateral ACL injury vs the group without ACL deficiency, a 1° increase in posterior-inferior tibial slope angle ( P =.03) was associated with a 20% increase in unilateral ACL injury. In those with bilateral ACL injury vs those without ACL deficiency, a 1° increase in posterior-inferior tibial slope angle ( P =.001) increased bilateral knee injury by 34%. The difference between the mean angles of the control group without ACL deficiency and both the bilateral injury and unilateral injury cohorts was statistically significant ( P =.003). Increased posterior-inferior tibial slope angle is associated with an increased risk of noncontact bilateral and unilateral ACL injury. [ Orthopedics. 2017; 40(1):e136–e140.]

In forensic anthropology, generic equations are generally preferred for estimation of stature. However, recent studies have demonstrated that regression equations specific to stature groups yield more accurate predictions. Almost all previous studies have been conducted on male subjects, and it is not currently known how well such equations work for females. Therefore, this study aims to test whether regression equations specific to stature groups work for females as well. To this end, a cross-sectional study was conducted to estimate stature on a sample of 351 Spanish adult females. The participants were randomized into a calibration group (n = 185) and a validation group (n = 166). Equations for stature estimation based on tibial length were developed in the calibration group, which was categorized according to stature (short, medium, and tall) using the 15th and 85th percentiles as cut-off points. The standard errors of the estimations (SEEs) for the group-specific regression equations (SEE = 2.35–2.66 cm) were lower than for the general formula derived for all participants of the calibration group (SEE = 3.46 cm). The specific equations resulted in smaller differences between estimated and recorded statures than the generic equation when we tested the equations with the validation group. Additionally, the SEE values of the stature-specific equations are lower compared to generic equations applied to other human populations. In conclusion, the group-specific equations from tibial length have high accuracy compared with previously derived equations for Spanish females and other populations. This procedure for estimating stature thereby improves the tools available to forensic scientists.

Summary This randomized controlled trial evaluated the effect of resistance training frequency (0, 1, and 2 times/week) on cortical volumetric bone mineral density (vBMD) at the tibia in older women. There was no mean difference in change in tibial cortical vBMD in older women who engaged in resistance training (RT) one or two times/week compared with the control group over 12 months after adjusting for baseline values. Introduction National guidelines recommend RT two to three times/week to optimize bone health. Our objective was to determine the effect of a 12-month intervention of three different RT frequencies on tibial volumetric cortical density (CovBMD) in healthy older women. Methods We randomized participants to the following groups: (1) 2×/week balance and tone group (i.e., no resistance beyond body weight, BT), (2) 1×/week RT (RT1), and (3) 2×/week RT (RT2). Treatment allocation was concealed, and measurement team and the bone data analyst were blinded to group allocation. We used peripheral quantitative computed tomography to acquire one 2.3-mm scan at the 50 % tibia, and the primary outcome was CovBMD. Data were collected at baseline, 6 and 12 months, and we used linear mixed modeling to assess the effect at 12 months. Results We assessed 147 participants; 100 women provided data at all three points. Baseline unadjusted mean (SD) tibial CovBMD (in milligrams per cubic centimeter) at the 50 % site was 1,077.4 (43.0) (BT), 1,087.8 (42.0) (RT1), and 1,058.7 (60.4) (RT2). At 12 months, there were no statistically significant differences (−0.45 to −0.17 %) between BT and RT groups for mean difference in change in tibial CovBMD for exercise interventions (BT, RT1, RT2) after adjusting for baseline tibial CovBMD. Conclusion We note no mean difference in change in tibial CovBMD in older women who engaged in RT one or two times/week compared with the control group over 12 months. It is unknown if RT of 3× or 4×/week would be enough to promote a statistically significant difference in change of bone density.

Recent anatomical and radiological studies of the anterior cruciate ligament (ACL) suggest the ACL length and orientation change during knee flexion, and an open MRI sequencing during knee flexion enables a dynamic ACL analysis. This study’s goal is to describe a normal ACL using a 1T open MRI and, in particular, variations in length and insertion angles at different degrees of flexion. Twenty-one volunteers with clinically healthy knees received a dynamic MRI with their knees in hyperextension, neutral position, and flexed at 45° and 90° angles. For each position, two radiologists measured the ACL lengths and angles of the proximal insertion between the ACL’s anterior edge and the roof of the inter-condylar notch. Additionally, we measured the ACL’s and the tibial plateau’s distal angle insertion between their anterior edges and then compared these with the nonparametric Wilcoxon test. The ACL had a significant extension between the 90° flexion and all other positions (hyperextension: 31.75 ± 2.5 mm, neutral position: 32.5 ± 2.6 mm, 45°: 35.6 ± 1.6 mm, 90°: 35.6 ± 1.6 mm). There was also a significant increase of the angle insertion between the proximal 90° flexion and all other positions, as well as between hyperextension and bending to 45° (hyperextension: 2.45° ± 3.7°, neutral: 13.4° ± 9.7°, 45°: 33 25 ± 9.3, 90: 51.85° ± 9.3°). Additionally, there is a significant increase in the distal angle insertion for all positions (hyperextension: 133.2° ± 5.4°, neutral position: 134.95° ± 4.4°, 45°: 138.35° ± 5.9°, 90°: 149.15° ± 8.6°). Our study is the first to exhibit that a dynamic MRI has a significant ACL extension in vivo during bending. This concept opens the way for further studies to improve the diagnosis of traumatic ACL injuries using a dynamic MRI.

Purpose The anatomical landmark for the anteroposterior (AP) axis of the proximal tibia and its variability was investigated in order to determine whether a certain landmark could be employed as a reference axis for the proximal tibia after the rotating platform mobile bearing and fixed bearing total knee arthroplasties (TKAs). Methods Eighty primary osteoarthritic knees were randomized to undergo either rotating platform mobile bearing (Group A, n  = 40) or fixed bearing (Group B, n  = 40) TKAs, and were followed up for 31 and 30 months, respectively. The AP axes were defined for the distal femur, proximal tibia, ankle, and each TKA component on the reconstructed CT scan and the angles between the distal femoral AP axis and those of each bone or component were estimated. Clinical and radiographic outcomes were evaluated during the follow up. Results A significant difference was seen between the preoperative and postoperative rotational position of the proximal tibia relative to the distal femur following rotating platform mobile bearing TKA ( P  = 0.014) whereas no such difference was seen after fixed bearing TKA. The mean postoperative alignment of the tibia differed between the two groups (Group A:Group B = −2.9:0.2, P  = 0.010) and its variability was significantly greater in group A ( P  < 0.001). There were no differences in the clinical outcomes including range of motion, knee society score, function score, HSS, and WOMAC score as well as the mean postoperative coronal tibiofemoral alignment between the two groups. Conclusion The unpredictable change in the rotational axis of the tibia and its broad variability after rotating platform mobile bearing TKA may provide a warning against the use of a fixed landmark for establishing tibial rotational alignment. Level of evidence Prospective comparative study, Level II.

α-catulin is identified as a marker to locate functional haematopoiteic stem cells in deep imaging experiments of bone marrow, showing that α-catulin –GFP + c-kit + cells commonly reside in perisinusoidal niches throughout the bone marrow. A marker for bone marrow stem cells The location of haematopoietic stem cells (HSCs) in the bone marrow remains unclear. The absence of a single marker that can identify HSCs, the rarity of HSCs and the limitations in imaging techniques in the bone marrow have prevented the resolution of this question. Sean Morrison and colleagues have now identified α-catulin as marker of functional HSCs that can be used to visualize the cells in optically cleared bone marrow using deep confocal imaging and digital tissue reconstruction. They find that α-catulin GFP + c-kit + cells are more common in central marrow than near bone surfaces, and in the diaphysis region of the bone relative to the metaphysis. The cells identified in this fashion are found in perisinusoidal niches throughout bone marrow and in close proximity to leptin receptor positive and Cxcl12 high cells. Haematopoietic stem cells (HSCs) reside in a perivascular niche but the specific location of this niche remains controversial 1 . HSCs are rare and few can be found in thin tissue sections 2 , 3 or upon live imaging 4 , making it difficult to comprehensively localize dividing and non-dividing HSCs. Here, using a green fluorescent protein (GFP) knock-in for the gene Ctnnal1 in mice (hereafter denoted as α - catulin GFP ), we discover that α - catulin GFP is expressed by only 0.02% of bone marrow haematopoietic cells, including almost all HSCs. We find that approximately 30% of α - catulin −GFP + c-kit + cells give long-term multilineage reconstitution of irradiated mice, indicating that α - catulin −GFP + c-kit + cells are comparable in HSC purity to cells obtained using the best markers currently available. We optically cleared the bone marrow to perform deep confocal imaging, allowing us to image thousands of α - catulin –GFP + c-kit + cells and to digitally reconstruct large segments of bone marrow. The distribution of α - catulin –GFP + c-kit + cells indicated that HSCs were more common in central marrow than near bone surfaces, and in the diaphysis relative to the metaphysis. Nearly all HSCs contacted leptin receptor positive (Lepr + ) and Cxcl12 high niche cells, and approximately 85% of HSCs were within 10 μm of a sinusoidal blood vessel. Most HSCs, both dividing (Ki-67 + ) and non-dividing (Ki-67 − ), were distant from arterioles, transition zone vessels, and bone surfaces. Dividing and non-dividing HSCs thus reside mainly in perisinusoidal niches with Lepr + Cxcl12 high cells throughout the bone marrow.