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- Lower Limb Landing Biomechanics in Subjects with Chronic Ankle Instability. [JOURNAL ARTICLE]
- Med Sci Sports Exerc 2014 Sep 15.
Literature on lower limb kinematic deviations in subjects with chronic ankle instability (CAI) during landing tasks is limited and not consistent. Several studies only report joint angles at defined events rather than considering the whole kinematic curve which might obscure possibly relevant information. Therefore, the main goal of this study was to evaluate landing kinematics of the lower limb in subjects with CAI using curve analysis.Lower limb kinematics of 56 subjects (28 subjects with self-reported CAI and 28 matched healthy controls) were measured during a barefoot forward and side jump protocol. Kinematic data were collected in a laboratory setting using an eight-camera optoelectronic system. Ground reaction forces were registered by means of a force plate built into the landing zone. After completion of each task, difficulty level and subjective stability at the ankle joint were documented using a visual analogue scale. To compare between groups, Statistical Parametric Mapping was used to assess group differences between mean joint angles over the entire impact phase.SPM analysis of kinematical curves of the hip, knee, and ankle showed no significant differences between the subjects with CAI and the control group independent of jump direction. Subjects with CAI did report higher feelings of instability for both landing tasks and a higher difficulty level for the forward jump.Our results showed no altered lower limb kinematics in subjects with CAI compared to a healthy control group during a forward and side jump landing task. Therefore, these results question the hypothesis of kinematic deviations as part of an underlying mechanism of CAI.
- Use of a Fluoroscopic Overlay to Guide Femoral Tunnel Placement During Posterior Cruciate Ligament Reconstruction. [JOURNAL ARTICLE]
- Am J Sports Med 2014 Sep 15.
Intraoperative recognition of the local anatomy of the posterior cruciate ligament (PCL) is difficult for many surgeons, and correct positioning of the graft can be challenging.To investigate the efficacy of an overlay system based on fluoroscopic landmarks in guiding femoral tunnel placement during PCL reconstruction.Controlled laboratory study.Twenty cadaveric knees were arthroscopically prepared, and their PCL femoral insertion sites were digitized. The digitized images were co-registered to computed tomography-acquired 3-dimensional bone models. Twenty surgeons with diverse backgrounds performed simulated arthroscopic reconstruction of the anterolateral (AL) and posteromedial (PM) bundles of the PCL, first without and then with the aid of a lateral fluoroscopic image on which the position of a target insertion site based on literature data was displayed as an overlay. The surgeons were allowed to adjust tunnel placement in accordance with the displayed target position. A 3-way comparison was made of the tunnel positions placed by the surgeons, the native insertion site positions, and the literature-based positions.The overlay system was effective in helping surgeons to improve femoral tunnel placement toward the target and toward the anatomic insertion site (P < .05). For femoral AL tunnel placement, surgeons needed 2.35 ± 2.21 extra attempts, which added an extra 80.00 ± 67.95 seconds to the procedure. For PM tunnel placement, surgeons needed 1.80 ± 1.88 extra attempts, adding 66.00 ± 70.82 seconds to the simulated surgery. In their first attempts, more than half of the surgeons positioned either the AL or PM femoral tunnel >5 mm from the native insertion site. With the use of the overlay, 70% of the surgeons were <5 mm away from the PM and 75% from the AL native insertion site.The use of a fluoroscopic overlay to guide intraoperative placement of the femoral tunnel(s) during PCL reconstruction can result in more anatomic reconstructions and therefore assist in re-creating native knee kinematics after PCL reconstruction.Intraoperative fluoroscopy is an effective, easy, and safe method for improving femoral tunnel positioning during PCL reconstruction.
- The sustentaculum tali screw fixation for the treatment of Sanders type II calcaneal fracture: A finite element analysis. [Journal Article]
- Pak J Med Sci 2014 Sep; 30(5):1099-103.
In the surgery of calcaneal fracture, whether the sustentaculum tali screw should always be placed is widely controversial. The aim of this study was to explore the necessity and function of the sustentaculum tali screw placement for the treatment of Sanders type II calcaneal fracture.The finite element analysis was used in this study. After the establishment of the finite element model of Sanders type II calcaneal fracture, the two internal fixation simulations were designed. In one model, the AO calcaneal plate was simulated on the lateral side of the calcanues with 7 screws being fixated at different position of the plate. In the other model, the calcaneus was fixated with the same AO calcaneal plate together with an additional screw being infiltrated into the sustentaculum tali. The two models were simulated under the same loading and the displacement of the fracture line and the stress distribution in the two models were calculated respectively.The maximum principal stress focused on the cortical bone of sustentaculum tali in both the models under the same loading. The displacement of the fracture line, the maximum principal stress of calcaneus and internal fixation system in the model with sustentaculum screw fixation were smaller than that in the model without sustentaculum screw fixation. The stress in the model with sustentaculum screw fixation was more dispersed.The placement of sustentaculum tali screw is essential for fixation of type II calcaneal fracture to achieve the biomechanical stability.
- Potential pathogenic mechanism for stress fractures of the bowed femoral shaft in the elderly: Mechanical analysis by the CT-based finite element method. [JOURNAL ARTICLE]
- Injury 2014 Aug 30.
Stress fractures of the bowed femoral shaft (SBFs) may be one of the causes of atypical femoral fractures (AFFs). The CT-based finite element method (CT/FEM) can be used to structurally evaluate bone morphology and bone density based on patient DICOM data, thereby quantitatively and macroscopically assessing bone strength. Here, we clarify the pathogenic mechanism of SBFs and demonstrate this new understanding of AFFs through mechanical analysis by CT/FEM.A prospective clinical study was performed from April 2012 to February 2014. We assembled two study groups, the bowed AFF group (n=4 patients; mean age, 78.0 years) including those with a prior history of AFF associated with bowing deformity and the thigh pain group (n=14 patients; mean age, 78.6 years) comprising outpatients with complaints of thigh pain and tenderness. Stress concentration in the femoral shaft was analysed by CT/FEM, and the visual findings and extracted data were assessed to determine the maximum principal stress (MPS) and tensile stress-strength ratio (TSSR). In addition, we assessed femoral bowing, bone density, and bone metabolic markers. Wilcoxon's rank sum test was used for statistical analysis.All patients in the bowed AFF group showed a marked concentration of diffuse stress on the anterolateral surface. Thirteen patients in the thigh pain group had no significant findings. However, the remaining 1 patient had a finding similar to that observed in the bowed AFF group, with radiographic evidence of bowing deformity and a focally thickened lateral cortex. Patients were reclassified as having SBF (n=5) or non-SBF (n=13). Statistical analysis revealed significant differences in MPS (p=0.0031), TSSR (p=0.0022), and femoral bowing (lateral, p=0.0015; anterior, p=0.0022) between the SBF and non-SBF groups, with no significant differences in bone density or bone metabolic markers.Significant tensile stress due to bowing deformity can induce AFFs. SBFs should be considered a novel subtype of AFF, and patients with complaints of thigh pain and femoral shaft bowing deformity must be considered at high risk for AFFs. This project (Ref: AOTAP 13-13) was supported by AOTrauma Asia Pacific.
- The Dynamic, Six-Axis Stiffness Matrix Testing of Porcine Spinal Specimens. [JOURNAL ARTICLE]
- Spine J 2014 Sep 12.
Complex testing protocols are required to fully understand the biomechanics of the spine. There remains limited data concerning the mechanical properties of spinal specimens under dynamic loading conditions in six axes.To provide new data on the mechanical properties of functional spinal unit (FSU), and isolated disc (ISD) spinal specimens in six degrees of freedom.Dynamic, six-axis stiffness matrix testing of porcine lumbar spinal specimens.The stiffness matrix testing of lumbar porcine FSU (n=6) and ISD (n=6) specimens was completed in a custom six-axis spine simulator using triangle wave cycles at a frequency of 0.1 Hz. Specimens were first tested without an axial preload, and with an axial preload of 500 N with equilibration times of both 30 and 60 minutes. The study was supported through an institutional grant, and the authors are not aware of any conflicts of interest related to this research.The stiffness matrices were not symmetrical about the principal stiffness terms. The facets increased all the principal stiffness terms with the exception of axial compression-extension. Significant differences were detected in 15 stiffness terms due to the application of an axial preload in the ISD specimens, including an increase in all principal stiffness terms. There were limited differences in stiffness due to an equilibration time of 30 and 60 minutes.The assumption of stiffness matrix symmetry used in many previous studies is not valid. The biomechanical testing of spinal specimens should be completed in 6 degrees of freedom, at physiological loading rates, and incorporate the application of an axial preload. The present study has provided new data on the mechanical properties of spinal specimens, and demonstrates that the dynamic stiffness matrix method provides a means to more fully understand the natural spine, and quantitatively assess spinal instrumentation.
- The effect of running velocity on footstrike angle - A curve-clustering approach. [JOURNAL ARTICLE]
- Gait Posture 2014 Aug 18.
Despite a large number of studies that have considered footstrike pattern, relatively little is known about how runners alter their footstrike pattern with running velocity. The purpose of this study was to determine how footstrike pattern, defined by footstrike angle (FSA), is affected by running velocity in recreational athletes. One hundred and two recreational athletes ran on a treadmill at up to ten set velocities ranging from 2.2-6.1ms(-1). Footstrike angle (positive rearfoot strike, negative forefoot strike), as well as stride frequency, normalised stride length, ground contact time and duty factor, were obtained from sagittal plane high speed video captured at 240Hz. A probabilistic curve-clustering method was applied to the FSA data of all participants. The curve-clustering analysis identified three distinct and approximately equally sized groups of behaviour: (1) small/negative FSA throughout; (2) large positive FSA at low velocities (≤4ms(-1)) transitioning to a smaller FSA at higher velocities (≥5ms(-1)); (3) large positive FSA throughout. As expected, stride frequency was higher, while normalised stride length, ground contact time and duty factor were all lower for Cluster 1 compared to Cluster 3 across all velocities; Cluster 2 typically displayed intermediate values. These three clusters of FSA - velocity behaviour, and in particular the two differing trends observed in runners with a large positive FSAs at lower velocities, can provide a novel and relevant means of grouping athletes for further assessment of their running biomechanics.
- Analysis of the distance covered by Brazilian professional futsal players during official matches. [JOURNAL ARTICLE]
- Sports Biomech 2014 Sep 16.:1-11.
The purpose of this study was to measure and characterise the distances covered by Brazilian professional futsal players. The trajectories of 93 players during five matches were obtained using an automatic tracking method. The distances covered were analysed for different game conditions: over the entire game and during the times when the ball was out of play and in play separately. When the entire game was considered, the results showed that there was a reduction in the total distance covered per minute from the first [median ± IQR (interquartile range): 97.9 ± 16.2 m/min] to the second half (median = 90.3 m/min; IQR = 12.0), and when only the in-play time was considered (first half: 136.6 ± 17.2 m/min; second half: 129.2 ± 16.7 m/min). The percentage of distance covered in the standing and walking velocity range was higher in the second half than in the first when considering the entire game (30.8% and 28.0%, respectively) and during the in-play time (19.3% and 16.2%, respectively). In conclusion, this study verified that futsal players reduced the physical performance during the second half.
- Locomotor Sensory Organization Test: A Novel Paradigm for the Assessment of Sensory Contributions in Gait. [JOURNAL ARTICLE]
- Ann Biomed Eng 2014 Sep 16.
Feedback based balance control requires the integration of visual, proprioceptive and vestibular input to detect the body's movement within the environment. When the accuracy of sensory signals is compromised, the system reorganizes the relative contributions through a process of sensory recalibration, for upright postural stability to be maintained. Whereas this process has been studied extensively in standing using the Sensory Organization Test (SOT), less is known about these processes in more dynamic tasks such as locomotion. In the present study, ten healthy young adults performed the six conditions of the traditional SOT to quantify standing postural control when exposed to sensory conflict. The same subjects performed these six conditions using a novel experimental paradigm, the Locomotor SOT (LSOT), to study dynamic postural control during walking under similar types of sensory conflict. To quantify postural control during walking, the net Center of Pressure sway variability was used. This corresponds to the Performance Index of the center of pressure trajectory, which is used to quantify postural control during standing. Our results indicate that dynamic balance control during locomotion in healthy individuals is affected by the systematic manipulation of multisensory inputs. The sway variability patterns observed during locomotion reflect similar balance performance with standing posture, indicating that similar feedback processes may be involved. However, the contribution of visual input is significantly increased during locomotion, compared to standing in similar sensory conflict conditions. The increased visual gain in the LSOT conditions reflects the importance of visual input for the control of locomotion. Since balance perturbations tend to occur in dynamic tasks and in response to environmental constraints not present during the SOT, the LSOT may provide additional information for clinical evaluation on healthy and deficient sensory processing.
- Change in First Metatarsal Length After Proximal and Distal Chevron Osteotomies for Hallux Valgus Deformity. [JOURNAL ARTICLE]
- J Foot Ankle Surg 2014 Sep 12.
The present study assessed the changes in the length of the first metatarsal bone after performing proximal chevron metatarsal osteotomy (PCMO) or distal Chevron metatarsal osteotomy (DCMO) for patients with hallux valgus deformity. A total of 60 patients with moderate-to-severe hallux valgus deformity from July 2009 to July 2011 were randomly divided into the PCMO and DCMO groups, with 30 patients in each group. The distal soft tissue procedure was performed in the same method for both groups. Measurements were performed preoperatively, postoperatively, and at the last follow-up visit at 6.1 ± 0.8 months. The postoperative length change with respect to the preoperative length was 0.7 ± 2.5 mm and -0.7 ± 5.1 mm for the PCMO and DCMO groups, respectively, with a slight lengthening of the first metatarsal bone in the PCMO group and a shortening in the DCMO group (p < .01). The follow-up length change with respect to the preoperative length was -2.1 ± 3.0 mm and -4.4 ± 2.2 mm for the PCMO and DCMO groups, respectively, demonstrating a clear shortening of the first metatarsal length at the last follow-up point in the DCMO group (p < .01).When DCMO and the distal soft tissue procedure were performed, significant shortening was found at 6 months of follow-up.
- Biomechanics of Schlemm's canal endothelium and intraocular pressure reduction. [REVIEW]
- Prog Retin Eye Res 2014 Sep 12.
Ocular hypertension in glaucoma develops due to age-related cellular dysfunction in the conventional outflow tract, resulting in increased resistance to aqueous humor outflow. Two cell types, trabecular meshwork (TM) and Schlemm's canal (SC) endothelia, interact in the juxtacanalicular tissue (JCT) region of the conventional outflow tract to regulate outflow resistance. Unlike endothelial cells lining the systemic vasculature, endothelial cells lining the inner wall of SC support a transcellular pressure gradient in the basal to apical direction, thus acting to push the cells off their basal lamina. The resulting biomechanical strain in SC cells is quite large and is likely to be an important determinant of endothelial barrier function, outflow resistance and intraocular pressure. This review summarizes recent work demonstrating how biomechanical properties of SC cells impact glaucoma. SC cells are highly contractile, and such contraction greatly increases cell stiffness. Elevated cell stiffness in glaucoma may reduce the strain experienced by SC cells, decrease the propensity of SC cells to form pores, and thus impair the egress of aqueous humor from the eye. Furthermore, SC cells are sensitive to the stiffness of their local mechanical microenvironment, increasing their own cell stiffness and modulating gene expression in response. Significantly, glaucomatous SC cells appear to be hyper-responsive to substrate stiffness. Thus, evidence suggests that targeting the material properties of SC cells will have therapeutic benefits for lowering intraocular pressure in glaucoma.