[Effect of lumbar hybrid instrumentation and rigid fusion on the treated and the adjacent segments. A biomechanical study]

BACKGROUND

Degeneration of the upper adjacent segment after operative treatment of degenerative spinal diseases of the lumbar spine (degenerative disc disease DDD) is an unsolved problem. There is also no consensus on whether a rigid or dynamic treatment of DDD should be carried out to protect the segments. This study was carried out to evaluate the effect of bisegmental rigid 360° fusion and bisegmental hybrid fusion on the treated segment as well as on the upper adjacent segment under the aspect of segment protection.

MATERIAL AND METHODS

A total of six human spinal column preparations (L2-5) were tested under native conditions (NAT), with bisegmental rigid fusion (RIG 360°) and with hybrid fusion (Hybrid) in all three movement directions under physical load and with an preload. The range of motion (ROM) and neutral zone (NZ) were evaluated. The intradiscal pressure (IDP) was measured in the upper adjacent segment (OAS).

RESULTS

The RIG 360° led to a significant reduction in movement in all directions compared to NAT but Hybrid only in lateral bending (LB). In the OAS the NZ was showed a much greater increase than the ROM. The RIG 360° showed an increase of the NZ in flexion-extension of 86.8% and in LB of 49.6% as well as a significant increase in axial rotation of 52.5%. The increase in the Hybrid was not significant compared to NAT in all directions. Pressure measurements in OAS showed no significant differences for RIG 360° and for Hybrid compared to NAT for both load scenarios.

DISCUSSION

The range of motion of the treated segments for Hybrid were close to NAT in comparison to RIG 360° indicating a segment-protective effect. The hypothesis that rigid fusion has a significant effect on intersegmental mobility and the increase in intradiscal pressure in the upper adjacent segment could not be confirmed. The data indicate that the primary effect of fusion on the adjacent segment is very low but the fusion-linked increased frequency of extreme loads of the OAS falling within the significance level leads to degeneration. Even if the NZ values for Hybrid and RIG 360° do not significantly differ from NAT, the NZ alterations between the instrumentations tend to be strongly shifted in favor of Hybrid.

CONCLUSIONS

The data confirm that the clear and sometimes significant alterations of the NZ can be an essential factor for development of adjacent segment degeneration. A dynamic conclusion of instrumentation in the sense of a topping-off would appear to be useful if pathoanatomical indications for an intervertebral disc prosthesis are present.

The effect of design parameters of dynamic pedicle screw systems on kinematics and load bearing: an in vitro study

As an alternative treatment for chronic back pain due to disc degeneration motion preserving techniques such as posterior dynamic stabilization (PDS) has been clinically introduced, with the intention to alter the load transfer and the kinematics at the affected level to delay degeneration. However, up to the present, it remains unclear when a PDS is clinically indicated and how the ideal PDS mechanism should be designed to achieve this goal. Therefore, the objective of this study was to compare different PDS devices against rigid fixation to investigate the biomechanical impact of PDS design on stabilization and load transfer in the treated and adjacent cranial segment. Six human lumbar spine specimens (L3-L5) were tested in a spine loading apparatus. In vitro flexibility testing was performed by applying pure bending moments of 7.5 Nm without and with additional preload of 400 N in the three principal motion planes. Four PDS devices, "DYN" (Dynesys(®), Zimmer GmbH, Switzerland), "DSS™" (Paradigm Spine, Wurmlingen, Germany), and two prototypes of dynamic rods, "LSC" with a leaf spring, and "STC" with a spring tube (Aesculap AG, Tuttlingen, Germany), were tested in comparison to a rigid fixation device S(4) (Aesculap AG, Tuttlingen, Germany) "RIG", to the native situation "NAT" and to a defect situation "DEF" of the specimens. The instrumented level was L4-L5. The tested PDS devices comprising a stiffness range for axial stiffness of 10 N/mm to 230 N/mm and for bending stiffness of 3 N/mm to 15 N/mm. Range of motion (ROM), neutral zone (NZ), and intradiscal pressure (IDP) were analyzed for all instrumentation steps and load cases of the instrumented and non-instrumented level. In flexion, extension, and lateral bending, all systems, except STC, showed a significant reduction of ROM and NZ compared to the native situation (p < 0.05). Furthermore, we found no significant difference between DYN and RIG (p > 0.1). In axial rotation, only DSS and STC reduced the ROM significantly (p < 0.005) compared to the native situation, whereas DYN and LSC stayed at the level of the native intersegmental rotation (p > 0.05). A correlation was found between axial stiffness and intersegmental stabilization in the sagittal and frontal plane, but not in the transversal plane where intersegmental stabilization is mainly governed by the systems' ability to withstand shear loads. Furthermore, we observed the systems' capacity to reduce IDP in the treated segment. The adjacent segment does not seem to be affected by the stiffness of the fixation device under the described loading conditions.

[Retrospective study--pregnancy after assisted medical reproduction from 2001 to 2009 at the Central Hospital of Luxembourg (first section)]

Retrospective study on a nine year ART practice focusing on pregnancy outcomes and multiple pregnancies, their complications, the gestational duration, delivery options, the new born weights and health statements til the age of two. Post ART pregnancies seem to have an increased complication rate; multiple births are more frequent than with spontaneous conception. The first chapter deals with the entire group. The second chapter analyses several sub-groups according to the ART method employed. The results are compared to publications in PubMed and Medline.

[Retrospective studies of pregnancies after assisted medical reproduction from 2001-2009 and Central Hospital in Luxembourg (part 2)]

The first chapter analyses the ART methods of the Centre Hospitalier of Luxembourg, in the department of reproductive medicine between 2001 and 2009. The second chapter examines the techniques individually, their influence on pregnancy outcomes, the complications on offsprings and their health. The results coincide with literature in that risks are acceptable as long as good medical and biological conditions are maintained. Multiple pregnancies remain the most frequent complication, particularly once out of IVF. These are analysed separately as well as the pregnancies after egg and semen donation.

Correlates of sexual functioning among mid-life women

OBJECTIVE

Studies have reported a decline in sexual functioning among women undergoing the menopausal transition. Few studies, however, have examined the associations between hormones and sexual dysfunction during this time period. Therefore, the purpose of this study was to examine the associations between participant characteristics and endogenous hormones with sexual functioning in mid-life women.

METHODS

Data were analyzed from a community-based sample of 441 women aged 45-54 years who stated that they were sexually active at the time of the study. Each participant completed a survey that included questions pertaining to sexual functioning and provided a blood sample that was used to measure estrogen and androgen concentrations.

RESULTS

Among women who reported being sexually active, poorer self-reported health and the experiencing of depressive symptoms were significantly associated with not being satisfied with sexual relations after adjustment for other covariates. None of the hormones examined were significantly associated with overall sexual satisfaction. However, statistically significant associations between both total testosterone levels and the free testosterone index with satisfaction with the frequency of sexual relations were observed.

CONCLUSIONS

Our findings indicate that the experiencing of depressive symptoms and the reporting of poor overall health are important correlates of sexual dysfunction. Further, our results suggest that higher total and free testosterone levels are significantly associated with a desire for increased frequency of sexual relations among mid-life women.

1.3 microm quantum dot laser in coupled-cavity-injection-grating design with bandwidth of 20 GHz under direct modulation

Using a multi section laser in coupled cavity injection grating design based on 1.3 microm InGaAs/GaAs quantum dot (QD) active region we were able to enhance the 3 dB modulation bandwidth well beyond the inherent material modulation bandwidth. The material bandwidth was determined by measurements on distributed feedback (DFB) devices to approximately 8 GHz. The special multisectional design allows interaction between the lasing mode and a second mode used as catalyst and enables a high resonance frequency of the device. Based on active QD material this approach allowed us to reach a cut off frequency of 20 GHz in the small signal response of the device.

[Biological parameters for evaluation of ovarian reserve and resultant antimullerian hormone]

No biological parameter allows a predictive result in ART for ovary stimulation. We studied the interest of dosing AMH in ovary stimulation in balance with the the clinical context.

Relation of body mass and sex steroid hormone levels to hot flushes in a sample of mid-life women

OBJECTIVE

Previous studies indicate that obesity is associated with a higher risk of experiencing hot flushes in mid-life women. The reasons for this association are unknown, although altered hormone levels have been associated with both hot flushes and obesity. Thus, this current study tested the hypothesis that obesity is associated with hot flushes in mid-life women through a mechanism involving levels of total and free androgen, free estrogen, progesterone, and sex hormone binding globulin (SHBG).

METHODS

Women aged 45-54 years were recruited from Baltimore and its surrounding counties. Each participant (n=628) was weighed, measured, completed a questionnaire, and provided a blood sample that was used to measure estradiol, estrone, testosterone, androstenedione, dehydroepiandrosterone sulfate, progesterone, and SHBG.

RESULTS

Obese mid-life women (body mass index (BMI)>or=30.0 kg/m2) had significantly higher testosterone, and lower estradiol, estrone, progesterone, and SHBG levels than normal-weight mid-life women (BMI<or=24.9 kg/m2) after adjustment for age, race, smoking, and number of days since last menstrual period. The association between obesity and hot flushes was no longer significant after adjustment for estrogens and progesterone, and/or SHBG.

CONCLUSION

These data suggest that obesity may be associated with hot flushes through a mechanism involving multiple hormones and SHBG.

Reproduction of wild Mongolian gerbils bred in the laboratory with respect to generation and season 1. Morphological changes and fertility lifespan

A new strain of wild Meriones unguiculatus (strain Ugoe:MU95, named WILD) with high genetic variability was recently established in Germany. A previous study showed that offspring (F-1) of WILD founders (F-0) showed reduced spermatogenesis and testosterone compared to domesticated gerbils (LAB) maintained under similar conditions. We investigated F-0 and subsequent generations in respect to sexual maturation, duration of fertility and gonadal weights of different seasons. Body and reproductive organ weights showed negligible seasonal fluctuations in both strains. Testis and epididymis weights in WILD covered a wide range, which indicates a high reproductive variability. Reproductive organ weights increased in F-3. Less variable and high reproductive organ weights (testis >900 mg, epididymis >200 mg) in almost all LAB illustrate their readiness to reproduce, even in small individuals. Prominent testis (T+) was found in 71% of adult males (F-1, F-2) reflecting the natural portion of T+(63%) found in wild gerbils investigated in Mongolia in 1995 and 2002. Testicular descent was accelerated and pronounced in WILD F-3 (T+, 88%) and LAB (T+, 91%). Time between mating and the first litter was significantly longer in wild F-0 than in their offspring or LAB. The average age in wild F-0 when the last litter was born was 27 months. Breeding went on for 2 to 32 months and was mostly terminated by the death of the females. Relative testis and epididymis weights correspond in young adults and in old males up to 6 years, the total life span of male wild Mongolian gerbils. In summary, the results suggest that laboratory conditions improve the reproductive fitness of wild gerbils.