The origins of the thenar and hypothenar muscles.
This paper presents an anatomical study of the origins of the thenar and hypothenar muscles and postulates the causes of weakness and pillar pain following carpal tunnel release.
Cadaver↗
Biomedical subjects
Z P Luo
Publications and source records attributed to Z P Luo.
Effect of pregnancy on joint contracture in the rat knee.
As there is evidence that ligamentous laxity is affected by the female hormones, we hypothesized that hormonal changes occurring during pregnancy could have a therapeutic role in preventing the development of a joint contracture. Knee joint contractures were created in pregnant and nonpregnant rats. After 2 wk of immobilization, the degree of contracture was measured with structural properties of the medial collateral and anterior cruciate ligaments and the pubic symphysis. Although not statistically significant, there was a general trend toward reduced contracture in pregnant compared with nonpregnant rats. Cutting the posterior capsule significantly decreased contracture for both the pregnant and nonpregnant groups, confirming the contribution of capsular structures to contracture. Ultimate loads of the medial collateral and anterior cruciate ligaments significantly decreased after immobilization compared with control, but there was no significant effect due to pregnancy. Stiffness and ultimate load of the pubic symphysis were not significantly different between pregnant and nonpregnant groups. The trend toward reduced contracture with pregnancy points toward a possible therapeutic role for female hormones in the prevention of postoperative and/or posttraumatic joint contracture.
Animals↗
Stretching short biopolymers using optical tweezers.
Optical tweezers is a useful technique to study single molecules. It has been applied to stretch biopolymers in several approaches. However, these approaches may not be appropriate to measure short biopolymers. In the present study, the optical signals of beads in different situations were studied. A new method was developed for stretching short biopolymers, as short as 300 nm in length. This new method was successfully applied to determine the stiffness of procollagen I molecules.
Biopolymers↗
Mechanical behavior of the Lisfranc and dorsal cuneometatarsal ligaments: in vitro biomechanical study.
OBJECTIVES: To define the anatomy and mechanical properties of two ligaments stabilizing the medial tarsometatarsal joints: the Lisfranc ligament and the dorsal cuneometatarsal ligament. DESIGN: Cadaveric study in normal feet. SETTING: Biomechanics laboratory. PATIENTS OR PARTICIPANTS: Twelve fresh-frozen cadaveric feet were studied. INTERVENTION: The Lisfranc and dorsal cuneometatarsal ligaments were dissected, dimensions measured, and material properties determined with a servohydraulic MTS machine on bone-ligament-bone preparations. MAIN OUTCOME MEASUREMENTS: Stiffness, strain, stress, modulus, failure load, ligament length, width, thickness, and cross-sectional area were determined. RESULTS: Dorsal ligament stiffness was 66.3+/-18.3 newtons per millimeter and the Lisfranc ligament stiffness was 189.7+/-57.2 newtons per millimeter. The failure load of the dorsal ligament averaged 150.7+/-33.1 newtons and for the Lisfranc ligament, 368.8+/-126.8 newtons. CONCLUSIONS: The stiffness and load to failure of the dorsal cuneometatarsal ligament were much higher than anticipated, which indicates that it contributes significantly to stabilizing the second metatarsal to the first cuneiform.
Aged↗
Determination of the compressive material properties of the supraspinatus tendon.
A methodology was developed for determining the compressive properties of the supraspinatus tendon, based on finite element principles. Simplified three-dimensional models ure re reated based on anatomical thickness measurements of unloaded supraspinatus tendons over 15 points. The tendon material was characterized as a composite structure of' longitudinally arranged collagen fibers within an extrafibrillar matrix. The matrix was formulated as a hyperelastic material described by the Ogden form of the strain energy potential. The hyperelastic material parameters were parametrically manipulated until the analytical load-displacement results were similar to the results obtaizned from indentation testinrg. In the geometrically averaged tendon, the average ratio of experimental to theoretical maximum indentation displacement was 1.00 (SD: 0.01). The average normalization of residuals was 2.1 g (SD: 0.9 g). Therefjore, the compressive material properties of the supraspinatus tendo'n extrafibrillar matrix were adequately derived with a first-order hyperelastic formulation. The initial comnpressive elastic modulus ranged from 0.024 to 0.090 MPa over the tendon surface and increased nonlinearly with additional compression. Using these material properties, the stresses induced during acromional impingement can be analyzed.
Cadaver↗
Antistress effect of oligosaccharides extracted from Morinda officinalis in mice and rats.
AIM: To explore the antistress effect of Morinda officinalis (Chinese medicine "Bajitian") oligosaccharides (MW-97) in mice. METHODS: Male mice and rats were subjected to a variety of unpredictable stressors on a daily basis over 15 d period and then the Vidiomex-V image pattern analytic system was used to observe the spontaneous motor activity. Meanwhile, regular method was used to prepare pathologic section of adrenal gland and blood cells analytic system was used to detect white blood cell (WBC) count (including relative WBC percentages) in peripheral blood. On the end, the serum level of stress hormone was detected using radioimmunoassay. RESULTS: Chronic stress resulted in diffuse hyperplasia of the adrenal cortex and atrophy of the adrenal medulla in mice, which suggested that stress-adaption failure of the adrenal gland occurred, while adrenal gland of the mice pretreated with MW-97 (100 mg/kg, ip) prior to each stressor for 15 d did not occur any pathologic changes. In addition, chronic stress also significantly reduced the WBC count and relative WBC percentages in the peripheral blood, including the percentage of lymphocytes, monocytes, neutrophils, however, MW-97 (25 and 100 mg/kg) reversed these changes and raised WBC count, along with relative WBC percentages significantly. Furthermore, the serum concentration of testosterone was decreased and corticosterone was increased significantly in chronically stressed animals. MW-97 also declined the serum level of corticosterone and raised level of testosterone. MW-97 had no effects on the spontaneous motor activity in the stressed mice. CONCLUSION: MW-97 had antistress effect against chronic stress, moreover, MW-97 had no excitatory or inhibitory effects on the CNS, which suggested that MW-97 might become a new kind of antistress agent.
Adrenal Glands↗
Tendon-Defect and muscle-unloaded models for relating a rotator cuff tear to glenohumeral stability.
Rotator cuff tear and glenohumeral instability are closely related. Any tear may disturb muscle force generation due to pain inhibition. In addition, a full-thickness tear may foster instability by removing a structural element constraining the joint. It was hypothesized that the loss of both dynamic force and static constraint with a rotator cuff tear will affect glenohumeral stability. In a tendon-defect model, dynamic and static elements of the joint were sacrificed. In a muscle-unloaded model, only the dynamic element was removed. The location and size of the defect were also investigated. The effect on instability of a small tendon defect was less than that of muscle unloading, implying that a patient with a small tear would have less instability than a patient with weak or nonfunctioning supraspinatus and infraspinatus muscles. On the other hand, with a larger tear the defect had a greater effect than muscle-unloading because sectioning of the glenohumeral and coracohumeral ligaments was included in the model. Clinically, such a defect in the front is critical for anterior stability because it might insult the important anterior capsule ligamentous complex. Orthopaedic surgeons should pay attention, therefore, to the effect of possible associated lesions of static constraints based on the size and location of the tear in addition to the dynamic stabilizer.
Aged↗
The manual stress test may not be sufficient to differentiate ankle ligament injuries.
OBJECTIVE: To assess the accuracy of stress tests (anterior drawer, talar tilt) in the diagnosis of lateral ligament injuries.Design. Stress tests were performed in vitro, and rotation and displacement of the calcaneus relative to the tibia were measured. BACKGROUND: Stress tests are commonly used to diagnose ankle injuries. However, it is controversial as to whether stress tests can accurately differentiate between isolated anterior talofibular ligament injuries and combined anterior talofibular and calcaneofibular ligament injuries. METHODS: Stress tests were performed in vitro under three conditions with both ligaments intact, after sectioning the anterior talofibular ligament, and after sectioning the anterior talofibular and calcaneofibular ligament. Motion of the calcaneus relative to the tibia was measured in neutral and in 20 degrees of plantarflexion at the ankle. RESULTS: There were statistically significant differences among cadavers, examiners and positions. There was a difference between isolated anterior talofibular ligament sectioning and combined anterior talofibular and calcaneofibular ligament sectioning in lateral tilt but not in anterior displacement. In contrast, a difference was found between intact and anterior talofibular ligament sectioned specimens in anterior displacement but not in lateral tilt. However the differences were not great enough to differentiate between the two conditions. CONCLUSIONS: Each of the stress tests provides reasonable hindfoot displacement but neither is sufficient for accurate diagnosis of specific ligament involvement due to the large amount of individual variation. RELEVANCE: Many clinicians rely on stress tests to diagnose lateral ligament injuries and to assess the extent of anatomic disruption. This in vitro study has demonstrated poor correlation between clinical stress tests and the degree of ligamentous disruption.
Aged↗
The bursal and articular sides of the supraspinatus tendon have a different compressive stiffness.
OBJECTIVE: To measure the compressive stiffness of the supraspinatus tendon and to determine whether regional difference exists in the bursal and articular side of the tendon. DESIGN: Indentation testing was performed on both the bursal and articular sides of the supraspinatus tendon, focused on the 'critical area', where rotator cuff tears often occur. BACKGROUND: When the supraspinatus tendon wraps around the humeral head or is under impingement condition, compressive force on the tendon surface is expected. Therefore, compressive stress has been recently considered to be one of the important factors associated with the cuff tear. The mechanical properties would be essential for analytic modeling of stress distribution. METHODS: Indentation tests were performed at 15 locations on the bursal and articular surfaces of the supraspinatus tendon. A mathematical model with exponential relationship was used to describe the measured force-deformation relationship and to calculate the compressive stiffness of the supraspinatus tendon. RESULTS: The over-all initial stiffness on the bursal and articular sides of the tendon was significantly different. On the bursal side, the anterior third had a significantly higher initial stiffness than the other thirds on average. On the articular side, initial stiffness at location 10 mm proximal to the greater tuberosity was significantly higher than the rest on average. CONCLUSIONS: The compressive stiffness of the supraspinatus tendon was found to be non-homogenous throughout the structure.RelevanceNon-homogenous compressive stiffness of the supraspinatus tendon would affect the load transmission within the tendon, which might be associated with the potential mechanism of tear. Such characteristics needs to be considered when performing finite element modeling of stress fields in the tendon.
Aged↗
The influence of weakness in the vastus medialis oblique muscle on the patellofemoral joint: an in vitro biomechanical study.
OBJECTIVE: Investigation of the influence of weakness in the vastus medialis oblique muscle on patellar tracking. DESIGN: In vitro biomechanical study. BACKGROUND: Currently, the influence of weakness in the vastus medialis oblique muscle on patellar tracking has not been well understood. METHODS: Seven human cadaveric knees were used. The direction of loading forces in the rectus femoris/vastus intermedius, vastus medialis oblique, and the vastus lateralis muscles was decided by the muscle alignment of each cadaver knee measured at the time of dissection. The loads used were 60 N in the rectus femoris, 50 N in the vastus lateralis, and 40 N in the vastus medialis oblique, according to the ratio calculated from the cross-sectional study. The weakness of vastus medialis oblique was simulated at 30 N (75%), 20 N (50%), 10 N (25%), and 0 N (0%), and the patellar position was measured for each condition using a magnetic 3 Space Tracker System. The influence of weakness in the vastus medialis oblique muscle on patellar position was investigated with seven cadaver knees using a magnetic 3 Space Tracker System. RESULTS: At 0 degrees and 15 degrees of knee flexion, 75%, 50%, 25% and 0% of the normal vastus medialis oblique muscle led to a significant difference in lateral patellar shift compared to the normal (P<0.05). CONCLUSIONS: Weakness of the vastus medialis caused the patellar lateral shift at 0 degrees and 15 degrees of knee flexion. RELEVANCE: Weakness of the vastus medialis is thought to be an important factor causing patellar subluxation and dislocation. Understanding the relationship between the vastus medialis weakness and patellar tracking will be useful in diagnosis, treatment and prevention of patellar subluxation and dislocation.
Analysis of Variance↗
Calcaneocuboid distraction arthrodesis for posterior tibial tendon dysfunction and flatfoot: a cadaveric study.
Nine fresh-frozen foot specimens were studied to determine the mechanical behavior of the foot using calcaneocuboid distraction arthrodesis, an operation designed for treatment of posterior tibial tendon dysfunction with flatfoot deformity. Flatfoot deformity was created in cadaveric specimens, and to simulate toe-off phase of gait, loads were applied to the plantar surface of the foot and six tendons. Three-dimensional tarsal bone positions were determined with a magnetic tracking system. With ligament sectioning, flatfoot deformity was observed and average arch height decreased 53 +/- 3.5 mm. Height arch increased after calcaneocuboid distraction arthrodesis an average of 3.2 +/- 3.6 mm and was less than normal arch at an average of 2.1 +/- 2.4 mm. Metatarsotalar alignment compared with flatfoot improved after calcaneocuboid distraction arthrodesis in adduction and inversion to the extent that these were not significantly different from intact foot positions. Calcaneotalar position improved after calcaneocuboid distraction arthrodesis in adduction and inversion. Calcaneocuboid alignment compared with flatfoot improved after calcaneocuboid distraction arthrodesis in adduction, plantar flexion, and eversion, but compared with an intact foot was overcorrected in all three planes of motion. Arch alignment in simulated toe-off phase of gait in cadaveric feet was improved significantly with calcaneocuboid distraction arthrodesis but was not reduced anatomically.
Aged↗
Effects of mechanical stress/strain and estrogen on cancellous bone structure predicted by fuzzy decision.
A theoretical model was developed on the basis of fuzzy decision to predict cancellous bone structure following changes in mechanical stress/strain and estrogen. The model was validated experimentally by simulation of the normal structure of a rat distal femur, and further used to predict the structural alterations following ovarian hormone deficiency. The results show that net bone resorption after ovariectomy occurs in the metaphysis at locations where trabecula were subjected to the lowest mechanical stress/strain. These findings, consistent with experimental results, suggest that estrogen deficiency increase the mechanostat set point at which bone cells perceive mechanical stress/strain. Additionally, the results show that changes in bone architecture which are due to alterations in bone remodeling can be simulated by fuzzy decision without precise mathematical description, and multiple factors can also be readily incorporated into the model.
Animals↗
[Protective effect of bajitian oligosaccharide on PC12 cells lesioned by corticosterone].
OBJECTIVE: To study the possible mechanism of antidepressant effect of Bajitian oligosaccharide (MW-97). METHODS AND RESULTS: After incubating with the PC12 cells in the presence of corticosterone(2 x 10(-4) mol.L-1) for 48 h, it was found that MW-97 could protect PC12 cells from the lesion done by corticosterone in a concentration-dependent manner. Furthermore, using RT-PCR mediated cross-species partial cDNA cloning, it was found that MW-97 and desipramine(DIM) increased NGF, BDNF mRNA in the frontal cortex after chronic administration for 21 days, meanwhile, BDNF mRNA in hippocampus was also increased. CONCLUSION: The cytoprotective effect of MW-97 consists in the possible mechanism of its antidepressant action, while the increasing expression of neurotrophic factors (NGF, BDNF mRNA) may be contributes to the cytoprotective effect.
Animals↗
Desipramine and fluoxetine antagonized 5,7-dihydroxytryptamine-induced lesion on rat hippocampal and cortical neurons.
AIM: To assess the protective effect of desipramine (Des) and fluoxetine (Flu) on the neurons against the lesion induced by a selective serotonergic neurotoxin in vitro. METHODS: The 10-day cultured primary neurons of hippocampus and cortex of rat was exposed to 5,7-dihydroxytryptamine (5,7-DHT) to determine the optimal lesion concentration and duration. Before exposing to 5,7-DHT, Des and Flu was added to the medium for 30 min to observe the protective effects. RESULTS: The optimal concentration and duration for 5,7-DHT was 600 micromol.L-1 and 4 h, respectively. Both Des and Flu showed a protective effect in the dose range of 0.8 micromol.L-1 to 10 micromol.L-1 and 0.04 micromol.L-1 to 0.6 micromol.L-1, respectively, when the neurons were injured by 5,7-DHT 600 micromol.L-1 for 4 h. Flu showed a higher efficacy than Des. Both exhibited a more powerful protective effect on the hippocampal neuron than on the cortical neuron. CONCLUSION: The antidepressant effect of Des and Flu was attributed to their protective effect on the injured serotonergic neuron of the hippocampus and the cortex.
5,7-Dihydroxytryptamine↗
A theoretical model to predict distribution of the fabric tensor and apparent density in cancellous bone.
The adaptation of cancellous bone to mechanical forces is well recognized. Theoretical models for predicting cancellous bone architecture have been developed and have mainly focused on the distribution of trabecular mass or the apparent density. The purpose of this study was to develop a theoretical model which can simultaneously predict the distribution of trabecular orthotropy/orientation, as represented by the fabric tensor, along with apparent density. Two sets of equations were derived under the assumption that cancellous bone is a biological self-optimizing material which tends to minimize strain energy. The first set of equations provide the relationship between the fabric tensor and stress tensor, and have been verified to be consistent with Wolff's law of trabecular architecture, that is, the principal directions of the fabric tensor coincide with the principal stress trajectories. The second set of equations yield the apparent density from the stress tensor, which was shown to be identical to those obtained based on local optimization with strain energy density of true bone tissue as the objective function. These two sets of equations, together with elasticity field equations, provide a complete mathematical formulation for the adaptation of cancellous bone.
Bone Density↗
Development and validation of a nanometer manipulation and measurement system for biomechanical testing of single macro-molecules.
A biomechanical testing system for single macro-molecules has been developed using optical tweezers. To achieve nanometer manipulation and measurement, a piezo-stage and an interferometer were adopted. A systematic calibration was then performed on the displacement resolution. The piezo-stage has a noise level around 1 nm standard deviation, and the interferometer has a noise level of less than 5 nm standard deviation. The results revealed that the system has a nanometer resolution which is sufficient for the measurement of deformation and stiffness of single macro-molecules.
Biomechanical Phenomena↗
Role of medical capsule and transverse metatarsal ligament in hallux valgus deformity.
The role of the medial capsule and transverse metatarsal ligament in hallux valgus deformity including stability of the first metatarsophalangeal and adjacent joints was investigated in vitro. The three-dimensional positions of the proximal phalanx, first metatarsal, and second metatarsal before and after sectioning the medial capsule and metatarsal ligament were measured using a magnetic tracking system. Valgus deformity of the hallux increased with medial capsule sectioning an average of 22.3 degrees +/- 6 degrees. Valgus deformity of the hallux increased with medial capsule and metatarsal ligament sectioning an average of 27.4 degrees +/- 9.1 degrees. Valgus deformity of the hallux did not change significantly after sectioning the metatarsal ligament only. No significant changes were found in varus and eversion of the first metatarsal, in valgus of the second metatarsal, in the distance between first and second metatarsal heads after sectioning the medial capsule, or in the metatarsal ligament. This study shows the importance of the medial capsule in hallux valgus deformity. The transverse ligament did not contribute substantially to cause the deformity.
Aged↗
Reconstruction operations for acquired flatfoot: biomechanical evaluation.
A major limitation of operations commonly performed for acquired flatfoot is inadequate correction of alignment. The authors defined the efficacy of two operations, deltoid ligament reconstruction and flexor digitorum longus tendon transfer, for treatment of posterior tibial tendon dysfunction with flatfoot deformity. Twelve fresh-frozen foot specimens were used. A flatfoot deformity was created, and, to simulate the midstance phase of gait, loads were applied axially to the plantar surface of the foot and to appropriate tendons. Foot position improved substantially after deltoid ligament reconstruction but not after flexor digitorum longus tendon transfer. The average increase in arch height after deltoid ligament reconstruction was 10.3 +/- 8.9 mm and after flexor digitorum longus tendon transfer, -0.6 +/- 2.0 mm. Mean arch height after deltoid ligament reconstruction was 2.2 +/- 1.7 mm less than intact arch height and, after flexor digitorum longus tendon transfer, 13.2 +/- 9.0 mm less than intact arch height. Improvement in metatarsal-talar, calcaneal-talar, and talar-tibial positions was significantly greater after deltoid ligament reconstruction than after flexor digitorum longus tendon transfer. Although the authors do not advocate clinical use, the deltoid ligament reconstruction was more effective than flexor digitorum longus tendon transfer in restoring arch alignment in flatfoot.
Adult↗