Effects of locally applied Insulin-like Growth Factor-I on osseointegration.

BACKGROUND: The aim of this study was to assess the effect of local application of IGF-I on osseointegration of dental implants placed in osteoporotic bones. MATERIAL AND METHODS: 16 rabbits were randomly distributed into two groups: eight animals were ovariectomized and fed a low-calcium diet for six weeks, in order to induce experimental osteoporosis, and the others were sham-operated and fed a standard diet. A titanium implant was inserted into the tibiae in both groups. In half of the rabbits, 4 µg of IGF-I was applied into the ostectomy, prior to the implant insertion. A total of 32 implants were placed. Animals were sacrificed two weeks after surgery and decalcified samples were processed for Bone-To-Implant Contact (BIC) and Bone Area Density (BAD) measurements. Analysis of variance (ANOVA) was used for statistical evaluation. P<0.05 was considered to be significant. RESULTS: Ovariectomy induced statistically significant lower BAD values (p=0.008) and a tendency towards lower BIC values when compared osteoporotic and healthy groups. The administration of 4 µg of IGF-I did not produce statistically significant differences neither on BIC nor on BAD values, neither in the osteoporotic animals nor in healthy. CONCLUSIONS: Within the limitations of this experimental study, local administration of 4 µg of IGF-I was not able to induce any changes in the osseointegration process two weeks after surgery, neither in healthy rabbits nor in the osteoporotic group.

Analysis of metallic traces from the biodegradation of endomedullary AZ31 alloy temporary implants in rat organs after long implantation times.

AZ31 alloy has been tested as a biodegradable material in the form of endomedullary implants in female Wistar rat femurs. In order to evaluate the accumulation of potentially toxic elements from the biodegradation of the implant, magnesium (Mg), aluminium (Al), zinc (Zn), manganese (Mn) and fluorine (F) levels have been measured in different organs such as kidneys, liver, lungs, spleen and brain. Several factors that may influence accumulation have been taken into account: how long the implant has been in place, whether or not the bone is fractured, and the presence of an MgF2 protective coating on the implant. The main conclusions and the clinical relevance of the study have been that AZ31 endomedullary implants have a degradation rate of about 60% after 13 months, which is fully compatible with fracture consolidation. Neither bone fracture nor an MgF2 coating seems to influence the accumulation of trace elements in the studied organs. Aluminium is the only alloying element in this study that requires special attention. The increase in Al recovered from the sampled organs represents 3.95% of the amount contained in the AZ31 implant. Al accumulates in a statistically significant way in all the organs except the brain. All of this suggests that in long-term tests AZ31 may be a suitable material for osteosynthesis.

Fracture bone healing and biodegradation of AZ31 implant in rats.

The ideal temporary implant should offer enough mechanical support to allow healing of the fracture and then biodegrade and be resorbed by metabolic mechanisms without causing any toxic effect. The aim of this research has been to simultaneously study in situ bone healing and the biodegradation of AZ31 Mg alloy as an osteosynthesis material. The in vivo study was carried out in AZ31 implants with and without Mg-fluoride coating inserted in un-fractured and fractured femurs of Wistar rats for long experimentation time, from 1 to 13 months, by means of computed tomography, histological and histomorphometric analysis. Tomography analysis showed the bone healing and biodegradation of AZ31 implants. The fracture is healed in 100% of the animals, and AZ31 maintains its mechanical integrity throughout the healing process. Biodegradation was monitored, quantifying the evolution of gas over time by 3D composition of tomography images. In all the studied groups, gas pockets disappear with time as a result of the diffusion process through soft tissues. Histomorphometric studies reveal that after 13 months the 46.32% of AZ31 alloy has been resorbed. The resorption of the coated and uncoated AZ31 implants inserted in fractured femurs after 1, 9 and 13 months does not have statistically significant differences. There is a balance between the biodegradation of AZ31 and bone healing which allows the use of AZ31 to be proposed as an osteosynthesis material.

Peripheral nerve grafts to the frog optic tectum: a morphological study of foreign axon regeneration in the central nervous system.

The proximal stump of a transected mandibular nerve was grafted onto the rostrodorsal surface of the optic tectum in adult Rana pipiens to investigate the morphologic characteristics of nonspecific axonal regeneration in a highly organized region of central nervous system (CNS). Within the first 3 weeks postgraft surgery (WPS), the nerve-tectum interface became firmly established. Concomitant with this was an invasion of the host tectum by a small number of fine "pioneerlike" axons from the nerve. By 6 WPS there developed a concerted instreaming of a large number of peripheral fibers. Once within the CNS, the foreign axons distributed themselves throughout the rostrocaudal extent of the tectum, but primarily its dorsal aspect within superficial layers 8 and 9. Presence of intact optic fibers at the time of mandibular fiber invasion served somewhat to restrict the regenerating aberrant axons in their course through layer 9. This restriction could be avoided by removal of the optic input either before or during peripheral ingrowth. However, once peripheral fibers had entered and established themselves in the host environment, no subsequent manipulation of the retinotectal projection had any effect. The aberrant growth pattern, which appeared remarkably stable after 6 WPS, consisted of a plexus of medium- and fine-caliber peripheral axons. Many of these fibers had numerous branches and "en passant" varicosities, the latter encompassing a variety of shapes and sizes. Terminal swellings and arborizations were also found. When comparing the regeneration of optic and mandibular nerve fibers in the tectum, two distinctions were made. Whereas optic axons revealed a fascicular and layered organization, mandibular axons showed a highly segregated and disordered growth pattern. These characteristic differences were maintained even when the two fiber systems were allowed to coregenerate into the same target tectum. Thus, each of the two groups of axons interacts with the tectal substrate in a distinct manner, apparently independent of the other.

[Multifactorial analysis of therapeutic outcome of pseudophakic retinal detachment surgery]. / Multifactoririelle Analyse des Therapieerfolges des Pseudoaphakieablatio.

BACKGROUND: Pseudophakic retinal detachment is one of the most severe complications after cataract surgery and is a common cause of permanently reduced visual acuity. We evaluated parameters predicting reduced functional outcome by a model of stepwise regression analysis. PATIENTS AND METHODS: A series of 102 consecutive patients with pseudophakic retinal detachment were analyzed for various parameters regarding cataract surgery, retinal surgery, and retinal detachment features. First, univariate analysis determined the correlations with reduced functional outcome. Secondly, a stepwise regression model analyzed statistically significant variables for their predictive value of a reduced visual outcome. RESULTS: The overall reattachment rate was 99%. In 69% of the patients there was an improvement of more than two lines at the end of the follow-up period. The most predictive factors for reduced functional outcome were the need for a silicone oil tamponade and the visual acuity prior to retinal detachment surgery. When silicone oil tamponade was not needed, the requirement of more than two retinal surgeries was the most predictive factor for reduced visual outcome. CONCLUSION: In our series the strongest predictive factors for a reduced functional outcome were the necessity of silicone oil, reduced visual acuity at the time of retinal detachment, and the requirement of more than two retinal surgeries. These findings suggest that first-line procedures should not be necessarily minimally invasive measurements but rather procedures that result in a stably attached retina in the first instance without permanent silicone oil tamponade, even if this first operation consists of an extended pars plana vitrectomy.

[A fixed dressing with a rubber sole for horses and cattle]. / Stützverband mit Gummisohle für Pferd und Rind.

A synthetic fixed dressing for great animals is described, which is worked up in such a manner that it is possible to fix on its soles a non-abrasive rubber plate.

Peripheral nerve grafts to the frog optic tectum: a morphological study of the axon reaction in trigeminal motor and sensory neurons.

The mandibular branch of the trigeminal nerve was severed and the proximal stump was grafted onto the optic tectum in adult Rana pipiens. The resultant changes occurring in the cell bodies of origin in the ipsilateral trigeminal motor and mesencephalic nuclei were studied qualitatively and quantitatively. Nucleolar, nuclear, and somal cross-sectional areas increased in size significantly approximately 3 days after surgery and peaked at 6 weeks postsurgery. This swelling, in which the nucleolus was most severely affected, gradually reversed itself and disappeared by 24 weeks after surgery. Despite the cell enlargement, cytoplasmic basophilia was maintained or even slightly increased. These morphologic changes suggest a strong anabolic reaction. Two differences were found between the motoneurons and the sensory neurons. First, the morphometric cell changes occurred at a faster rate in neurons of the trigeminal motor nucleus than in those of the mesencephalic nucleus. The time course of the motoneuron response correlated well with that of axonal regeneration from the nerve graft. Second, there was a delayed loss of mesencephalic nucleus cells between 12 and 24 weeks after surgery, whereas cells of the trigeminal motor nucleus were maintained at all survival times studied. Taken together with sensory cell loss in the trigeminal ganglion, this suggests a greater viability of regenerating motoneurons.