Isometric and isokinetic torques of bilateral quadriceps and hamstrings were measured with Isokinetic Rehabilitation and Testing System (Model No. Cybex 340) on 40 normal untrained subjects, 20 males and 20 females, ranging between the ages of 23 and 35 years. The mean peak isometric and isokinetic torque values of both muscle groups showed no significant differences between dominant (right) and nondominant (left) limbs in both sexes; however there were significant differences between the male and the female. As the angular velocity increased, the peak torque significantly decreased, and the point of peak torque output occurred significantly later in the range of motion for quadriceps and hamstrings (p less than 0.01). There were no significant changes in the hamstrings to quadriceps (H/Q) ratios as the angular velocity increased. However, there were significant differences of mean H/Q ratio between male and female (p less than 0.01). Height had significant positive correlation with peak isometric and isokinetic torques for both quadriceps and hamstrings (p less than 0.01). Weight was found to correlate significantly with peak isometric and isokinetic torques (p less than 0.01). The mean isometric torques were significantly higher than the mean isokinetic torques for any joint angles in both sexes (p less than .01).
Adult ; Biomechanics ; Female ; Human ; Knee Joint/*physiology ; Male ; Muscles/*physiology ; Sex Factors

The objectives of this investigation were to evaluate biomechanical factors in the atherosclerotic process using human in vivo hemodynamic parameters and computed numerical simulation qualitatively and quantitatively. The three-dimensional spatial patterns of steady and pulsatile flows in the left coronary artery were simulated, using a finite volume method. Coronary angiogram and Doppler ultrasound measurement of the proximal left coronary flow velocity were performed in humans. Inlet wave velocity distribution obtained from in vivo data of the intravascular Doppler study allowed for input of in vitro numerical simulation. Hemodynamic variables, such as flow velocity, pressure and shear stress of the left anterior descending coronary bifurcation site were calculated. We found that there were spatial fluctuation of flow-velocity and recirculation areas at the curved outer wall of the left anterior descending coronary artery, which were due to the differences of flow-velocity and shear stress, especially during the declaration phase of pulsatile flow. This study suggests that rheologic properties may be a part of the atherogenic process in the coronary bifurcated and curved areas.
Biomechanics ; Blood Flow Velocity/physiology ; Blood Pressure/physiology ; Coronary Arteriosclerosis/physiopathology* ; Coronary Arteriosclerosis/etiology* ; Coronary Vessels/physiopathology* ; Hemodynamics/physiology* ; Homeostasis/physiology ; Human ; Models, Cardiovascular* ; Pulsatile Flow ; Stress, Mechanical

The engineering of a functional blood vessel substitute has for a quarter of a century been a "holy grail" within the cardiovascular research community. Such a substitute must exhibit long term patency, and the critical issues in this area in many ways are influenced by biomechanics. One of the requirements is that it must be non-thrombogenic, which requires an "endothelial-like" inner lining. It also must have mechanical strength, i.e. a burst pressure, sufficient to operate at arterial pressures. Ideally, however, it must be more than this. It also must have viscoelastic properties that match those of the native vessel being replaced. Finally, if it is to be able to adapt to changing blood flow conditions, it must exhibit vasoactivity, a function which in and of itself can be viewed as biomechanical in nature. To achieve this requires having, as part of the construct, vascular smooth muscle cells, which are contractile in nature and oriented in a circumferential direction. Only if an engineered blood vessel substitute possesses all of these functional characteristics, can one say that the functionality exhibited by a native vessel is being mimicked.
Artificial Organs* ; Biomechanics ; Biomedical Engineering* ; Blood Vessels* ; Endothelium, Vascular/physiology ; Human ; Muscle, Smooth, Vascular/physiology ; Support, U.S. Gov't, Non-P.H.S. ; Thrombosis/etiology ; Vasomotor System/physiology

We performed biomechanical comparison of a xenograft bone plate-screw (XBPS) system for achieving cadaveric lumbar transpedicular stabilization (TS) in dogs. Twenty dogs' cadaveric L2-4 lumbar specimens were harvested and their muscles were removed, but the discs and ligaments were left intact. These specimens were separated to four groups: the L2-4 intact group as control (group I, n = 5), the L3 laminectomy and bilateral facetectomy group (LBF) (group II, n = 5), the LBF plus TS with metal plate-screw group (group III, n = 5) and the LBF plus TS with XBPS group (group IV, n = 5). Five kinds of biomechanical tests were applied to the specimens: flexion, extension, left-right bending and rotation. The averages of the 16 stiffness values were calculated and then these were statistically analyzed. The statistical results show that the XBPS system contributes spinal stability and this system can be a good choice for achieving TS.
Animals ; Biomechanics ; Bone Plates/*veterinary ; Bone Screws/*veterinary ; Cadaver ; Dogs ; Lumbar Vertebrae/physiology/*surgery ; Range of Motion, Articular/physiology ; Spinal Fusion/instrumentation/*methods ; Transplantation, Heterologous/instrumentation/*methods

BACKGROUND: The purpose of this study was to compare the initial stability of anatomical and non-anatomical single bundle anterior cruciate ligament (ACL) reconstruction and to determine which would better restore intact knee kinematics. Our hypothesis was that the initial stability of anatomical single bundle ACL reconstruction would be superior to that of non-anatomical single bundle ACL reconstruction. METHODS: Anterior tibial translation (ATT) and internal rotation of the tibia were measured with a computer navigation system in seven pairs of fresh-frozen cadaveric knees under two testing conditions (manual maximum anterior force, and a manual maximum anterior force combined with an internal rotational force). Tests were performed at 0, 30, 60, and 90 degrees of flexion with the ACL intact, the ACL transected, and after reconstruction of one side of a pair with either anatomical or non-anatomical single bundle ACL reconstruction. RESULTS: Under manual maximal anterior force, both reconstruction techniques showed no significant difference of ATT when compared to ACL intact knee state at 30degrees of knee flexion (p > 0.05). Under the combined anterior and internal rotatory force, non-anatomical single-bundle ACL reconstruction showed significant difference of ATT compared to those in ACL intact group (p < 0.05). In contrast, central anatomical single bundle ACL reconstruction showed no significant difference of ATT compared to those in ACL intact group (p > 0.05). Internal rotation of the tibia showed no significant difference in the ACL intact, the ACL transected, non-anatomical reconstructed and anatomical reconstructed knees. CONCLUSIONS: Anatomical single bundle ACL reconstruction restored the initial stability closer to the native ACL under combined anterior and internal rotational forces when compared to non-anatomical ACL single bundle reconstruction.
Aged ; Aged, 80 and over ; Anterior Cruciate Ligament/*anatomy & histology/physiology/*surgery ; Anterior Cruciate Ligament Reconstruction/*methods ; Biomechanics/physiology ; Cadaver ; Humans ; Knee Joint/*anatomy & histology/physiology/*surgery ; Middle Aged ; Random Allocation ; Range of Motion, Articular/physiology ; Tibia/anatomy & histology/physiology/surgery

The purpose of this study was to evaluate how soft tissue surgery for correcting equinus deformity affects the kinematic and kinetic parameters of the ankle and proximal joints. Sixteen children with spastic hemiplegic cerebral palsy and equinus deformities (age range 3-16 years) were included. Soft tissue surgeries were performed exclusively on the ankle joint area in all subjects. Using computerized gait analysis (Vicon 370 Motion Analysis System), the kinematic and kinetic parameters during barefoot ambulation were collected preoperatively and postoperatively. In all 16 children, the abnormally increased ankle plantar flexion and pelvis anterior tilting on the sagittal plane were significantly improved without a weakening of push-off (p < 0.05). In a group of 8 subjects with a recurvatum knee gait pattern before operation, the postoperative kinematic and kinetic parameters of the knee joint were significantly improved (p < 0.05). In a group of 8 subjects with ipsilateral pelvic external rotation before operation, the postoperative pelvic deviations on the transverse plane were significantly decreased (p < 0.05). These findings suggest that the soft tissue surgery for correcting equinus deformity improves not only the abnormal gait pattern of the ankle, but also that of the knee and pelvis.
Male ; Kinetics ; Joints/physiopathology/surgery ; Humans ; Hemiplegia/*surgery ; Gait/physiology ; Female ; Equinus Deformity/*surgery ; Child, Preschool ; Child ; Cerebral Palsy/*surgery ; Biomechanics ; Ankle Joint/physiopathology/surgery ; Adolescent

BACKGROUND: Despite the importance of soft tissue balancing during total knee arthroplasty (TKA), all estimating techniques are dependent on a surgeon's manual distraction force or subjective feeling based on experience. We developed a new device for dynamic gap balancing, which can offer constant load to the gap between the femur and tibia, using pneumatic pressure during range of motion. METHODS: To determine the amount of distraction force for the new device, 3 experienced surgeons' manual distraction force was measured using a conventional spreader. A new device called the consistent load pneumatic tensor was developed on the basis of the biomechanical tests. Reliability testing for the new device was performed using 5 cadaveric knees by the same surgeons. Intraclass correlation coefficients (ICCs) were calculated. RESULTS: The distraction force applied to the new pneumatic tensioning device was determined to be 150 N. The interobserver reliability was very good for the newly tested spreader device with ICCs between 0.828 and 0.881. CONCLUSIONS: The new pneumatic tensioning device can enable us to properly evaluate the soft tissue balance throughout the range of motion during TKA with acceptable reproducibility.
Arthroplasty, Replacement, Knee/*instrumentation/methods ; Biomechanics ; Equipment Design ; Femur/surgery ; Humans ; Knee Joint/physiology/*surgery ; Mechanical Processes ; Range of Motion, Articular ; Reproducibility of Results ; Tibia/surgery

Treatment of articular cartilage lesions remains a clinical challenge. The uses of prosthetic joint replace allograft and/or autograft transplant carry a risk of complications due to infection, loosening of its component, immunological rejection and morbidity at the donor site. There has been an increasing interest in the management of cartilage damages, owing to the introduction of new therapeutic options. Tissue engineering as a method for tissue restoration begins to provide a potential alternative therapy for autologous grafts transplantations. We aimed to evaluate how well a tissue engineered neocartilage implant, consist of human articular chondrocytes cultured with the presence of autologous serum and mixed in a fresh fibrin derived from patient, would perform in subcutaneous implantation in athymic mice.
Biomechanics ; Cartilage, Articular/injuries ; Cartilage, Articular/physiology ; Cartilage, Articular/*transplantation ; Chondrocytes/*cytology ; Culture Media ; Mice, Nude ; *Orthopedic Procedures ; Serum ; *Tissue Engineering