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- Elastic resistance of the spine: Why does motion preservation surgery almost fail? [JOURNAL ARTICLE]
- World J Clin Cases 2013 Jul 16; 1(4):134-139.
Single metamere motility should not be interpreted merely as a movement on the 3 planes but also, and above all, as elastic resistance to dynamic stress on these 3 planes. In the light of this consideration, the aim of motion preservation is to neutralize excessive movements while preserving the physiological biomechanical properties of the metamere involved to interrupt the progression of degenerative processes and to prevent adjacent segment disease. Despite the fact that a myriad of devices have been developed with the purpose of achieving dynamic neutralization of the spine, there are now some doubts regarding the true efficacy of these devices.
- Neuromuscular adaptations to 4 weeks of intensive drop jump training in well-trained athletes. [JOURNAL ARTICLE]
- Physiol Rep 2013 Oct; 1(5):e00099.
This study examined the effects of 4 weeks of intensive drop jump training in well-trained athletes on jumping performance and underlying changes in biomechanics and neuromuscular adaptations. Nine well-trained athletes at high national competition level within sprinting and jumping disciplines participated in the study. The training was supervised and augmented feedback on performance was used to ensure maximal training intensity. The drop jumps were performed with minimal contact time and maximal jumping height. Assessment of performance during training showed effects of motor learning. Before and after the training intervention maximal isometric muscle strength, the biomechanics, muscle activity pattern of the lower extremities and the soleus H-reflex and V-wave during drop jumping were measured. Maximal jump height and performance index (PI) defined as jumping height divided by contact time improved significantly by 11.9% (P = 0.024) and 16.2% (P = 0.009), respectively. Combined ankle and knee joint peak power was significantly increased by 7% after training (P = 0.047). The preactivity in the soleus muscle decreased 16% (P = 0.015). The soleus H-reflex was unchanged after training, while the soleus V-wave increased significantly at 45 msec after touchdown. This may indicate an increased drive to the α-motor neuron pool following training. Muscle strength parameters were unaffected by the training. The results demonstrate that 4 weeks of intensive drop jump training can improve jumping performance also in well-trained athletes without concomitant changes in muscle strength. It is suggested that the behavioral improvement is primarily due to neural factors regulating the activation pattern controlling the drop jump movement.
- The manipulation of strain, when stress is controlled, modulates in vivo tendon mechanical properties but not systemic TGF-β1 levels. [JOURNAL ARTICLE]
- Physiol Rep 2013 Oct; 1(5):e00091.
Modulators of loading-induced in vivo adaptations in muscle-tendon complex (MTC) mechanical properties remain unclear. Similarly contentious, is whether changes in MTC characteristics are associated with growth factor levels. Four groups were subjected to varying magnitudes of stress/strain: Group 1 trained with the MTC at a shortened position (MTCS; n = 10); Group 2 at a lengthened position (MTCL; n = 11; stress levels matched to MTCS); Group 3 over a wide range of motion (MTCX; n = 11); and Group 4 (n = 10) was the control population (no training). Patella tendon Stiffness (P < 0.001), Young's modulus, and quadriceps torque (P < 0.05) increments (only seen in the training groups), showed MTCL and MTCX groups responses to be superior to those of MTCS (P < 0.05). In addition, MTCL and MTCX better maintained adaptations compared to MTCS (P < 0.05) following detraining, with a pattern of slower loss of improvements at the early phase of detraining in all training groups. There were no significant changes (P > 0.05) in antagonist cocontraction, patella tendon dimensions or circulating transforming growth factor beta (TGF-β1) levels following training or detraining in any of the groups. We conclude that chronically loading the MTC in a relatively lengthened position (which involves greater strains) enhances its mechanical properties, more so than loading in a shortened position. This is true even after normalizing for internal stress. The underlying endocrine mechanisms do not appear to be mediated via TGF-β1, at least not at the systemic level. Our findings have implications with regard to the effectiveness of eccentric loading on improved tendon structural and mechanical properties.
- Application of Computational Lower Extremity Model to Investigate Different Muscle Activities and Joint Force Patterns in Knee Osteoarthritis Patients during Walking. [Journal Article]
- Comput Math Methods Med 2013.:314280.
Many experimental and computational studies have reported that osteoarthritis in the knee joint affects knee biomechanics, including joint kinematics, joint contact forces, and muscle activities, due to functional restriction and disability. In this study, differences in muscle activities and joint force patterns between knee osteoarthritis (OA) patients and normal subjects during walking were investigated using the inverse dynamic analysis with a lower extremity musculoskeletal model. Extensor/flexor muscle activations and torque ratios and the joint contact forces were compared between the OA and normal groups. The OA patients had higher extensor muscle forces and lateral component of the knee joint force than normal subjects as well as force and torque ratios of extensor and flexor muscles, while the other parameters had little differences. The results explained that OA patients increased the level of antagonistic cocontraction and the adduction moment on the knee joint. The presented findings and technologies provide insight into biomechanical changes in OA patients and can also be used to evaluate the postoperative functional outcomes of the OA treatments.
- Treatment of "Patellofemoral" Cartilage Lesions With Matrix-Assisted Autologous Chondrocyte Transplantation: A Comparison of Patellar and Trochlear Lesions. [JOURNAL ARTICLE]
- Am J Sports Med 2013 Dec 3.
BACKGROUND:Matrix-assisted autologous chondrocyte transplantation (MACT) has been shown to offer good outcomes at midterm follow-up, but results are heterogeneous among different patients and lesion types. Being part of the same joint, both patellar and trochlear cartilage lesions are commonly considered to be affected by the same treatment issues, and therefore, it is common practice to report results obtained treating these lesions together. PURPOSE:To determine, in a large cohort of patients prospectively followed at midterm follow-up for patellofemoral chondral defects, if patellar and trochlear defects actually represent different clinical conditions with different healing potentials after cartilage treatment. STUDY DESIGN:Cohort study; Level of evidence, 2. METHODS:A total of 49 consecutive patients with full-thickness patellofemoral chondral lesions of the knee were treated with MACT at the authors' institute and followed prospectively for a minimum follow-up of 5 years. Among these 49 patients, 28 were affected by patellar lesions, 17 were affected by trochlear lesions, and 4 had both patellar and trochlear defects. The clinical outcome was analyzed with International Knee Documentation Committee (IKDC) subjective, EuroQol visual analogue scale (EQ-VAS), Kujala, and Tegner scores. RESULTS:A statistically significant improvement in all scores was observed after treatment. Patellar lesions required more realignment procedures and were more common in women. The comparative analysis showed better results for trochlear lesions compared with patellar lesions at all follow-ups, with mean IKDC scores at 5-year follow-up of 89.6 ± 12.7 and 69.7 ± 17.6, respectively (P < .0005). Better results were also shown for the mean Kujala score (92.4 ± 14.7 vs 81.5 ± 12.7, respectively; P = .012) and mean EQ-VAS score (90.0 ± 10.8 vs 81.9 ± 11.7, respectively; P = .027). Finally, the sport activity level evaluated with the Tegner score confirmed the same trend; even though neither patellar nor trochlear lesion groups reached the preinjury level, both improved after treatment, with a significantly higher improvement in the trochlear lesion group (5.9 ± 1.8 vs 3.9 ± 1.7, respectively; P < .0005). CONCLUSION:Patient characteristics differ between patellar and trochlear cartilage defects, and moreover, the results obtained are significantly different, with a markedly good outcome in cases with trochlear lesions and less satisfactory results for patients affected by cartilage lesions of the patella. Thus, patellar and trochlear defects should be considered separately when evaluating the outcome of cartilage treatments in this anatomic region.
- Morphological and mechanical changes in juvenile red-eared slider turtle (Trachemys scripta elegans) shells during ontogeny. [JOURNAL ARTICLE]
- J Morphol 2013 Dec 3.
Turtles experience numerous modifications in the morphological, physiological, and mechanical characteristics of their shells through ontogeny. Although a general picture is available of the nature of these modifications, few quantitative studies have been conducted on changes in turtle shell shape through ontogeny, and none on changes in strength or rigidity. This study investigates the morphological and mechanical changes that juvenile Trachemys scripta elegans undergo as they increase in size. Morphology and shell rigidity were quantified in a sample of 36 alcohol-preserved juvenile Trachemys scripta elegans. Morphometric information was used to create finite element models of all specimens. These models were used to assess the mechanical behavior of the shells under various loading conditions. Overall, we find that turtles experience complementary changes in size, shape, deformability, and relative strength as they grow. As turtles age their shells become larger, more elongate, relatively flatter, and more rigid. These changes are associated with decreases in relative (size independent) strength, even though the shells of larger turtles are stronger in an absolute sense. Decreased deformability is primarily due to changes in the size of the animals. Residual variation in deformability cannot be explained by changes in shell shape. This variation is more likely due to changes in the degree of connectedness of the skeletal elements in the turtle's shells, along with changes in the thickness and degree of mineralization of shell bone. We suggest that the mechanical implications of shell size, shape, and deformability may have a large impact on survivorship and development in members of this species as they mature. J. Morphol., 2013. © 2013 Wiley Periodicals, Inc.
- Biomechanics of the Spine III. The Cranio-Cervical Junction. [Journal Article]
- Neuroradiol J 2007 Apr 30; 20(2):209-17.
By virtue of its unique anatomy and functions the cranial-cervical junction was excluded in previous reviews on the general biomechanics of the spine, being a world apart. The special design of the cranial-cervical (CCJ) junction responds to seemingly opposed necessities being at same time loose enough to allow a great variety of movements and strong enough to preserve the spinal cord and vertebral arteries and to resist the head weight and muscular action. The primary goal of the CCJ is to ensure the maximal mobility of the head for visual and auditory exploration of space. Like a cardan joint the CCJ allows simultaneous independent movements about three axes in order to repeat and extend eye movements under the control of vestibular receptors. Several muscular groups and a number of ligaments control the movements of the CCJ and ensure its stability. Although composed of two seemingly distinct joints the CCJ forms a unique functional complex whose stability is ensured by ligaments and bony restraints often operating on both joint components: the occipitoatlantal and atlantoaxial joints.
- Is the abdominal aortic aneurysm rupture rate decreasing? [Journal Article]
- Adv Surg 2013.:271-86.
Decreased smoking has likely had the most significant impact on reducing the prevalence of AAAs. In a review of public data in England and Wales, Anjum and colleagues illustrated a reduction of AAA rupture from 1997 to2009 across all ages attributed to a concurrent decrease in prevalence of smoking. This trend has also been noted in a meta-analysis from Sweeting and colleagues and attributed to a reduction in the prevalence of smoking since the mid-1970s along with an enhanced awareness of cardiovascular risk factor reduction and selective aneurysm screening. Along with an effort to reduce AAA progression and rupture, tools to predict patient-specific risk of AAA rupture are evolving with refined models that incorporate both aneurysm wall stress and wall strength likely to provide the most promising approach. Although the role of statins, ACE inhibitors, beta-blockers, and aspirin in preventing or slowing aneurysmal rupture remains unresolved, their proven benefit in reducing long-term cardiovascular mortality suggests that these medications should be considered in any patient with a small AAA. Currently, randomized trials do not show any survival benefit for open or endovascular repair for small aneurysms in the range of 4.0 to 5.4 cm. AAA repair, whether through an endovascular or open approach, is not without potential complication. Even at centers of excellence, the 30-day mortality rate for conventional AAA surgery is 3% to 5%, with rates of major morbidityranging from 15% to 40%. The Society for Vascular Surgery guidelines recommends surveillance for patients with a fusiform AAA of 4.0 to 5.4 cm. The risk of AAA rupture appears to be decreasing through heightened public awareness, advanced technology for AAA detection, screening and surveillance, improved understanding of biomechanics and natural progression in AAA rupture, along with the availability of a wide range of medical therapies for risk factor reduction and minimally invasive options for AAA repair.
- Biomechanics-Machine Learning System for Surgical Gesture Analysis and Development of Technologies for Minimal Access Surgery. [JOURNAL ARTICLE]
- Surg Innov 2013 Dec 2.
Background. The uptake of minimal access surgery (MAS) has by virtue of its clinical benefits become widespread across the surgical specialties. However, despite its advantages in reducing traumatic insult to the patient, it imposes significant ergonomic restriction on the operating surgeons who require training for the safe execution. Recent progress in manipulator technologies (robotic or mechanical) have certainly reduced the level of difficulty, however it requires information for a complete gesture analysis of surgical performance. This article reports on the development and evaluation of such a system capable of full biomechanical and machine learning. Methods. The system for gesture analysis comprises 5 principal modules, which permit synchronous acquisition of multimodal surgical gesture signals from different sources and settings. The acquired signals are used to perform a biomechanical analysis for investigation of kinematics, dynamics, and muscle parameters of surgical gestures and a machine learning model for segmentation and recognition of principal phases of surgical gesture. Results. The biomechanical system is able to estimate the level of expertise of subjects and the ergonomics in using different instruments. The machine learning approach is able to ascertain the level of expertise of subjects and has the potential for automatic recognition of surgical gesture for surgeon-robot interactions. Conclusions. Preliminary tests have confirmed the efficacy of the system for surgical gesture analysis, providing an objective evaluation of progress during training of surgeons in their acquisition of proficiency in MAS approach and highlighting useful information for the design and evaluation of master-slave manipulator systems.
- Posterior scleral biomechanics and the translaminar pressure difference. [Journal Article]
- Int Ophthalmol Clin 2014; 54(1):73-94.