Model of calf muscle tear during a simulated eccentric contraction, comparison between ex-vivo experiments and discrete element model.

The tearing of the muscle-tendon complex (MTC) is one of the common sports-related injuries. A better understanding of the mechanisms of rupture and its location could help clinicians improve the way they manage the rehabilitation period of patients. A new numerical approach using the discrete element method (DEM) may be an appropriate approach, as it considers the architecture and the complex behavior of the MTC. The aims of this study were therefore: first, to model and investigate the mechanical elongation response of the MTC until rupture with muscular activation. Secondly, to compare results with experimental data, ex vivo tensile tests until rupture were done on human cadavers {triceps surae muscle + Achilles tendon}. Force/displacement curves and patterns of rupture were analyzed. A numerical model of the MTC was completed in DEM. In both numerical and experimental data, rupture appeared at the myotendinous junction (MTJ). Moreover, force/displacement curves and global rupture strain were in agreement between both studies. The order of magnitude of rupture force was close between numerical (858 N for passive rupture and 996 N-1032 N for rupture with muscular activation) and experimental tests (622 N ± 273 N) as for the displacement of the beginning of rupture (numerical: 28-29 mm, experimental: 31.9 mm ± 3.6 mm). These differences could be explained by choices of DEM model and mechanical properties of MTC's components or their rupture strain values. Here we show that he MTC was broken by fibers' delamination at the distal MTJ and by tendon disinsertion at the proximal MTJ in agreement with experimental data and literature.

Biplanar stereoradiography predicts pulmonary function tests in adolescent idiopathic scoliosis: a cross-sectional study.

PURPOSE: Various spinal and rib cage parameters measured from complex examinations were found to be correlated with preoperative pulmonary function tests (PFT). The aim was to investigate the relationship between preoperative rib cage parameters and PFT using biplanar stereoradiography in patients with severe adolescent idiopathic scoliosis. METHODS: Fifty-four patients, 45 girls and nine boys, aged 13.8 ± 1.2 years, with Lenke 1 or 2 thoracic scoliosis (> 50°) requiring surgical correction were prospectively included. All patients underwent preoperative PFT and low-dose biplanar X-rays. The following data were collected: forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), FEV1/FVC ratio, residual volume, slow vital capacity (SVC), total lung capacity (TLC), rib cage volume (RCV), maximum rib hump, maximum width, mean thoracic index, spinal penetration index, apical vertebral rotation, main curve Cobb angle (MCCA), T4-T12 kyphosis. The primary outcome was the relationship between rib cage parameters and PFT. The secondary outcome was the relationship between rib cage parameters and spine parameters. Data were analyzed using Spearman's rank test. A multivariable regression analysis was performed to compare PFTs and structural parameters. Significance was set at α = 0.05. RESULTS: The mean MCCA was 68.7° ± 16.7°. RCV was highly correlated with all pulmonary capacities: TLC (r = 0.76, p < 0.0001), SVC (r = 0.78, p < 0.0001) and FVC (r = 0.77, p < 0.0001). RCV had a low correlation with FEV1/FVC (r = - 0.34, p = 0.014). SPI was not correlated with any pulmonary parameters. CONCLUSION: Rib cage volume measured by biplanar stereoradiography may represent a prediction tool for PFTs. LEVEL OF EVIDENCE: Non-randomized cross-sectional study among consecutive patients, Level 2. These slides can be retrieved under Electronic Supplementary Material.

Meniscal sizing before allograft: Comparison of three imaging techniques.

BACKGROUND: Accuracy of meniscal sizing is an important issue before allograft transplantation. To date, there is no consensus on the best imaging method. The purpose of this study was to compare plain radiographs, magnetic resonance imaging (MRI) and computed tomography (CT) arthrography in the assessment of meniscal size. We hypothesized that MRI and CT arthrography had better correlations than plain radiographs. METHODS: All patients operated on by meniscal allograft between January 2005 and May 2015 were screened. Among them, 32 patients had both preoperative radiographs, MRI and CT arthrography of the affected knee. The meniscal dimensions were evaluated, blindly and randomly, using three imaging methods. A correlation analysis between each technique was made. For radiographic methods, an additional comparison was made between original Pollard's method and the modified method (Yoon). Bone dimensions (tibial metaphysis) were also collected, using radiographs and MRI, in order to build new equations allowing determination of meniscal dimensions from those bone measurements. RESULTS: The radiographic methods offered satisfying evaluations of the meniscal dimensions in the sagittal plane, without significant difference when compared with CT arthrography or MRI. In the frontal plane, the radiograph methods were less effective. With new equations, allowing determination of meniscal dimensions from tibial plateau dimensions, the mean correlation coefficient was 0.39 (0.14-0.71). CONCLUSIONS: The correlation between radiographic methods and MRI depended on which parameter (frontal or sagittal) was measured. Thus, we proposed a new method for sizing of meniscus, easily measurable from bony landmarks, aiming to improve the accuracy of graft selection.

Shear waves elastography for assessment of human Achilles tendon's biomechanical properties: an experimental study.

INTRODUCTION: Achilles tendon is the most frequently ruptured tendon, but its optimal treatment is increasingly controversial. The mechanical properties of the healing tendon should be studied further. Shear waves elastography (SWE) measures the shear modulus, which is proven to be correlated to elastic modulus in animal tendons. The aim of our study was to study whether the shear moduli of human cadaveric Achilles tendon, given by SWE, were correlated with the apparent elastic moduli of those tendons given by tensile tests. MATERIALS AND METHODS: Fourteen cadaveric lower-limbs were studied. An elastographic study of the Achilles tendon (AT) was first done in clinical-like conditions. SWE was performed at three successive levels (0, 3 and 6cm from tendon insertion) with elastographic probe oriented parallel to tendon fibers, blindly, for three standardized ankle positions (25° plantar flexion, neutral position, and maximal dorsal flexion). The mean shear moduli were collected through blind offline data-analysis. Then, AT with triceps were harvested. They were subjected to tensile tests. A continuous SWE of the Achilles tendon was performed simultaneously. The apparent elastic modulus was obtained from the experimental stress-strain curve, and correlation with shear modulus (given by SWE) was studied. RESULTS: Average shear moduli of harvested AT, given by SWE made an instant before the tensile tests, were significantly correlated with shear moduli of the same AT made at the same level, previously in clinical-like condition (p<0.05), only in neutral position. There was a statistical correlation (p<0.005) and a correlation coefficient R² equal to 0.95±0.05, between shear moduli (SWE) and apparent elastic moduli (tensile tests), for 11 tendons (3 tendons were inoperable due to technical error), before a constant disruption in the correlation curves. DISCUSSION: We demonstrated a significant correlation between SWE of Achilles tendon performed in clinical-like conditions (in neutral position) and SWE performed in harvested tendon. We also found a correlation between SWE performed on harvested tendon and apparent elastic moduli obtained with tensile tests (for 11 specimens). As a consequence, we can suppose that SWE of AT in clinical-like conditions is related to tensile tests. To our knowledge, the ability of SWE to reliably assess biomechanical properties of a tendon or muscle was, so far, only demonstrated in animal models. CONCLUSION: SWE can provide biomechanical information of the human AT non-invasively.

Can cemented dual-mobility cups be used without a reinforcement device in cases of mild acetabular bone stock alteration in total hip arthroplasty?

INTRODUCTION: Cemented versions of dual-mobility cups (DMCs), helpful in cases of bone stock alteration, are usually used in association with a reinforcement device. To simplify the intervention in elderly subjects or those with a poor bone stock, the cups can be cemented directly into the bone, but the long-term result remains uncertain. We conducted a retrospective study in this population so as to: (1) assess whether cemented fixation of a DMC without a reinforcement device leads to a higher loosening rate, (2) confirm its efficacy in preventing dislocations in subjects at high risk of instability, and (3) measure the functional results. HYPOTHESIS: Cemented fixation of a DMC is reliable in cases of moderate alteration of bone stock. MATERIAL AND METHODS: Sixty-four patients (66 hips) undergoing implantation of a cemented DMC (Saturne™) without a reinforcement device were included in this single-center retrospective study. Their mean age was 79.8 years (range, 40-95 years). The indications varied: hip osteoarthritis (30.3%), prosthesis revision (44.0%), and trauma (25.8%). The patients were evaluated radiologically and clinically at follow-up. The main evaluation criterion was the revision rate for aseptic loosening. Dislocations, the infection rate, and the Postel Merle d'Aubigné (PMA) score were noted. RESULTS: At the mean follow-up of 4.2 years, three (4.6%) patients had been lost to follow-up and 22 (33.3%) had died. There was one case of aseptic loosening (1.5%). Cup survival was 98% at 5 years (95%CI [94-100]). There were no dislocations. There was one revision for infection. The mean PMA score was 15.5 (range, 9-18). DISCUSSION: The frequency of acetabular loosening was comparable to the frequency in cemented DMCs with a reinforcement device. A cemented DMC without a reinforcement device is possible and is a simple and viable option when there is moderate bone stock alteration. LEVEL OF EVIDENCE: IV, retrospective cohort study.