Axial rotation in the lumbar spine following axial force wrench

The report presents measurements of axial rotation of lumbar motion segments (L1/L2, L3/L4, L4/L5), particularly with small angles of rotation (in the range of +/-1 degrees) following axial force wrenches. The investigation focussed on determining the influence of geometrically varying configurations in axial wrench (consisting of axial torque and axial force) applied on the kinematics (as defined by the migrating instantaneous helical axis, IHA) of lumbar motion segments under constant resulting axial force, and relating IHA-migration to anatomical structures. In all segments, IHA migrated over several centimetres (up to 6 cm). The main portion of IHA-migration was linked to the angle of rotation interval of +/-1 degrees. 3. The shape of the IHA-migration was greatly dependent upon the position of the force line F(z). The-force-wrench-dependent wide IHA-migration found for the rotational angle interval of +/-1 degrees suggests that joint guidance predominates in segment kinematics. The segment kinematics can be adjusted by means of the geometrical configuration of the force wrenches. The design of non-fusion spine implants and FE calculations have to take into consideration joint guidance and muscular force distributions with small intervals of axial rotation.

Knee motion analysis of the non-loaded and loaded knee: a re-look at rolling and sliding

Many studies of knee motion have been reported in the literature over more than 100 years. Of particular interest to the analysis presented here is the work of the Freeman group, who elegantly measured tibio-femoral kinematics in studies made on cadavers and the knees of living individuals using MRI, anatomical dissection and RSA. We examined and re-evaluated the data collected by Freeman's group and suggest that their conclusion should be considered to be incorrect, since their methods of evaluation were oversimplified from the mathematical and physical perspectives. By applying appropriate methods, however, it is possible to show that the same data yield important insights into physiological knee kinematics and reveal that the rolling-sliding relationship depends on the degree of flexion and on joint load in the medial and lateral compartment, as well. In the initial range of flexion, a considerable amount of rolling was found to occur. Based on this analysis, it is possible to gain useful insights of value for the design of total knee replacements.

Changes in insulin like growth factors, myostatin and vascular endothelial growth factor in rat musculus latissimus dorsi by poly-3-hydroxybutyrate implants

The present study aimed at researching the synergistic effect between an ectopic bone substitute and surrounding muscle tissue. To describe this effect, changes of insulin like growth factors (IGF1, IGF2), myostatin (GDF8) and vascular endothelial growth factor (VEGF) mRNA content of 12 Wistar-King rats musculus latissimus dorsi with implanted poly-3-hydroxybutyrate (PHB) scaffold were examined after 6 and 12 weeks. At each time interval six rats were killed and implants and surrounding tissues prepared for genetic evaluation. Eight rats without any implants served as controls. RNA was extracted from homogenized muscle tissue and reverse transcribed. Changes in mRNA content were measured by Real-Time PCR using specific primers for IGF1, IGF2, GDF8 and VEGF. Comparing the level of VEGF mRNA in muscle after 6 and 12 weeks to the controls, we could assess a significant increase of VEGF gene expression (p<0.05) whereas the level of mRNA expression was higher after 6 than after 12 weeks of treatment. Expression of IGF1 gene was also significantly increased as compared to the controls over the observed period of time (p<0.05). In the case of the IGF2 gene, the expression was significantly elevated after 6 weeks (p<0.05), but not significantly increased after 12 weeks (p>0.05). We observed a significantly decreased GDF8 gene expression (p<0.05) both after retrieval of implants after 6 as well as after 12 weeks. Moreover, mRNA level of GDF8 after 6 and 12 weeks were comparable the same. Our results show that PHB implants in rat musculus latissimus dorsi interact with the surrounding muscle tissue. This interaction works itself on growth potential of the muscle.

Soft tissue integration in the neck area of titanium implants--an animal trial

Dental implant materials are required to enable good apposition of bone and soft tissues. They must show sufficient resistance to chemical, physical and biological stress in the oral cavity to achieve good long-term outcomes. A critical issue is the apposition of the soft tissues, as they have provided a quasi-physiological closure of oral cavity. The present experiment was performed to study the peri-implant tissue response to non-submerged (1-stage) implant installation procedures. Two different implants types (NobelBiocare, NobelReplace Tapered Groovy 4.3 x 10 mm and Replace Select Tapered TiU RP 4.3 x 10mm) were inserted into the right and left sides of 8 domestic pigs (Sus scrofa domestica) mandibles, between canines and premolars and immediately provided with a ceramic crown. Primary implant stability was determined using ressonance frequency analysis. Soft tissue parameters were assessed: sulcus depth (SDI) and junctional epithelium (JE). Following 70 days of healing, jaw sections were processed for histology and histomorphometric examination. Undecalcified histological sections demonstrated osseointegration with direct bone contact. The soft tissue parameters revealed no significant differences between the two implant types. The peri-implant soft tissues appear to behave similarly in both implant types.

Physiological functions of the human finger

Using morphological data describing the physiological curvature morphology of the corresponding articulating surfaces in each finger joint, it is shown that a) the flexion of each finger joint is described by two angles of flexion; b) in each finger joint, a "pump mechanism" for synovial fluid is present whose function is to lubricate and nourish the joint cartilage and c) finger posture has six kinematic degrees of freedom (DOF). Since six muscle forces control finger posture, the relationship between the muscle forces and finger posture is unambiguously described. The states of flexion of the interphalangeal joints restrict possible flexions in the metacarpophalangeal joint. Since the muscle forces act simultaneously on all three finger joints, the interdependence of the flexional states in the three finger joints can be attributed to the alignment of the lines of force and their sites of insertion, as a function of the corresponding flexion in the joints.

Different bone sesitivity to malformations induced by procarbazine in fetal rats

The study aimed at to induce cleft-lip-alveolus-palate (CLAP) applying procarbazine in rat fetuses at the 14(th) day of pregnancy, to supply thiocyanate and/or folic acid sufficient for preventive treatment and subsequently to investigate cleft extent in the palatal area as well as bone maturity. In this animal model, female primiparous inbred rats (LEW.1A) were used. The gravid animals were separated into treatment groups: group K (control), group P (procarbazine), group TP (thiocyanate and procarbazine) and group FTP (folic acid, thiocyanate, procarbazine). The results reveal that procarbazine may induce clefts in the palate area. Clefts occurred most frequently in group TP and mainly comprised subtotal clefts of the posterior secondary palate. As for palatal length, group FTP displayed the longest palate which was significantly different only from group K. A different picture was shown for the secondary palate with group TP displaying the shortest values which were significantly different from those in groups K, P, and FTP. Thus, group TP showed the most marked negative changes both for cleft frequency and palatal length as compared to group K and the other groups. The preventive application of either thiocyanate (TP) or thiocaynate and folic acid combined (group FTP) failed to completely prevent cleft formation in the palate area. In conclusion, a preventive effect on palatal clefts and growth inhibition could not be proved for the vitaminoid thiocyanate.

Mandible, maxilla and cervical spine--a functional unit?

The motion patterns of mandibular points were recorded in vivo in closed, free movements of the mandible parallel to the sagittal-vertical plane. The points ran along loops which were valued by their area and length. All points whose loops included the same area under regarding the sense of circulation formed a straight line. Lines belonging to different areas were parallel. When the absolute areas of the oops were plotted for particular points a hollow depression with two minima resulted. The point that showed the lowest minimum in the depression corresponded to the position of the neuromuscular mandibular axis of rotation. The points running along equal loop lengths formed elliptical lines with a minimum below the condyle. The lines of constant loop area and loop length were overlaid with lateral radiographs, to match the patterns of motion with anatomical structures. The mandibular axis of rotation lay mostly cranial anterior of the condyle whereas the point with the shortest path lay mainly below this axis point, inside the bony structures. The row of teeth in the maxilla was found to be located below the line of minimal loop lengths. The cervical spine was arranged along the depression of the minimal absolute areas.