[Review of 40 years AO/ASIF. The development of the Veterinary Surgical Working Group for Osteosynthesis Questions(AO) in Veterinary Medicine (AOVET) and a systematic operative fracture treatment in animals]. / Rückblick auf 40 Jahre AOVET. Die Entwicklung der veterinärchirurgischen Arbeitsgemeinschaft für Osteosynthesefragen (AOVET) und einer systematischen operativen Frakturbehandlung beim Tier.

With respect to the founding of the AOVET in 1969, the development of the systematic osteosynthesis in large and small animals is reviewed. With the introduction of the stable OS techniques corresponding to the principles and operative techniques developed by the organization of ASIF/AO (hum), the systematic operative fracture treatment in animals expanded remarkably. The application of the "absolutely" stable compression osteosynthesis was the basis for the successful fracture treatment in large animals. The systematic osteosynthesis in small animals was realized through the generation of a multitude of stabilization techniques for the different fracture types in the various anatomical areas and for special orthopaedic interventions. This was achieved through a specifically developed implant- instrument system and corresponding operation methods. This development was supported by instruction courses, published manuals and visiting fellowships. The extensive collaboration in research and development led to an increasing understanding of the diverse bone healing processes. The AOVET enjoyed a progressing integration into the AO/ASIF (hum) organization.

Mechanical properties of 18 different AO bone plates and the clamp-rod internal fixation system tested on a gap model construct.

OBJECTIVE: To compare the stiffness and strength of AO bone plates (DCP, LC-DCP, VCP, RCP, and LP) and the Clamp-Rod Internal Fixation System (CRIF). STUDY DESIGN: In vitro. SAMPLE SIZE: 12 individual implants of 18 plate dimensions and four sizes of CRIF, each corresponding to 2.0, 2.4/2.7, 3.5, or 4.5 mm screw sizes. METHODS: Implant-constructs of each plate and CRIF were created using Canevasit rods as a bone substitute in an unstable gap fracture model. Six implant-constructs of each type were tested under single cycle four-point bending loading, and six were tested under single cycle torsional loading until permanent plastic deformation occurred. RESULTS: Torsional stiffness and yield load of the DCP were always significantly greater than the CRIF within the same group. Bending properties of the 2.0 DCP were not significantly different to the 2.0 CRIF. The 2.7 DCP had significantly higher bending values than the 2.7 CRIF. The bending stiffness of the 3.5 DCP and 4.5 DCP was significantly less than their CRIF counterparts. While the bending yield load of the 3.5 DCP was significantly greater than the 3.5 CRIF, the bending yield load of the 4.5 DCP was significantly less than the 4.5 CRIF. CONCLUSION: A weakness was found in the torsional resistance of the CRIF constructs compared to the DCP constructs. CLINICAL SIGNIFICANCE: Bone holding power and applied screw torque should be considered when using the CRIF system in clinical application.

Unalloyed titanium for implants in bone surgery.

Commercially pure (c.p.) titanium has proven its suitability as an implant material in bone surgery over many years in the fields of osteosynthesis, oral implantology, and in certain applications in joint prosthetics. Excellent biocompatibility and corrosion resistance are outstanding features. Furthermore, c.p. titanium is known for not causing allergic reactions. The different grades of c.p. titanium and their minimum mechanical properties are specified in ISO and ASTM standards for implant materials. Typical mechanical properties are given for AO ASIF implant applications. The properties and clinical performance of c.p. titanium are discussed and compared to those of implant stainless steel and titanium alloys. In brief some specific features relating to c.p. titanium implant material are treated, including biocompatibility and soft tissue and bone response and taking into account the effects of implant surface configurations at the same time. In addition, issues are addressed which arise from frequent inquiries from clinics.

Evaluation of soft tissue reactions at the interface of titanium limited contact dynamic compression plate implants with different surface treatments: an experimental sheep study.

Five types of limited contact dynamic compression plates (LC-DCPs) of pure titanium with different surface treatments and an electropolished stainless steel LC-DCP were tested. The surface roughness parameters and chemical surface conditions were determined and checked for probable surface contamination. After an implantation period of 3 months on long bones of sheep, the soft tissue adjacent to the plates was evaluated histomorphometrically. The difference in roughness parameters was statistically significant for most surface conditions. A correlation was found between the surface roughness of the implants and the thickness of the adjacent soft tissue layer. The thinnest soft tissue reaction layer with a good adhesion to the implant surface was observed for the titanium anodized plates with coarse surface. Smooth implants, in particular the electropolished stainless steel plates, induced statistically significant thicker soft tissue layers. Profilometer roughness measurements combined with scanning electron microscopy techniques were useful methods to characterize the surface morphology.

Evaluation of the soft tissue interface at titanium implants with different surface treatments: experimental study on rabbits.

Recently, a dominant influence of the surface roughness parameters for the soft tissue reaction at the implant tissue interface was found in an experimental study on sheep. The purpose of the present study is to correlate the surface roughness parameters of different experimental bone plates to the results of the histomorphometric analyses of the adjacent soft tissues. Pure titanium plates (35 x 5 x 1 mm) with six different surface treatments and electropolished stainless steel plates were tested. Prior to implantation the surface roughness parameters were determined using a profilometer and a scanning electron microscope. The tibia of adult rabbits served as test sites. At least four plates of each type were implanted. Three months postoperatively the implants were harvested with an intact tissue envelope and were left in situ for the histological preparation. The difference in the roughness parameters is statistically significant for most surface conditions and has an effect on the soft tissue reaction. The histological evaluation shows a significant higher number of blood vessels for steel plates in comparison to titanium plates with handground and blasted surface conditions. For the rough type of anodized titanium surfaces a significantly thinner soft tissue capsule is found, compared to electropolished steel plates. For the steel plates a fluid film was found between the implant and the adjacent tissue layer. The material and the surface roughness of the implant, determine the tissue reaction at the interface. The rough type of anodized titanium implants seems to be preferable.

The limited contact dynamic compression plate (LC-DCP).

To realize the new concept of biological internal fixation the limited contact dynamic compression plate was developed. It minimizes vascular damage to the plated bone segment. It should lead to a more versatile and efficient application of internal fixation using plates.

Fracture-associated sarcoma in the dog.

Seven fracture-associated sarcomas developed in large-breed dogs after stabilization of comminuted long bone fractures with stainless steel plates and screws. In most cases, the healing pattern of the fractures was disturbed. The mean interval between fracture occurrence and tumor diagnosis was 5.5 years. Radiographically, the sarcomas were typified by smooth-bordered subperiosteal proliferation and soft tissue mineralization. Cortical destruction was variable. Several histologic subtypes of osteosarcoma were seen. Four sarcomas had a marked inflammatory cell component and 5 of the dogs had clinical evidence of chronic infection. These findings were similar to those in 35 previously reported fracture-associated sarcomas, even though many types of fixation devices in addition to plates, as well as no fixation at all, were represented in these cases. Fracture-associated sarcomas most frequently were found to be diaphyseal, and the femur accounted for almost half of the sarcomas reported.

[Corrosion behavior of different screws and posts in the root canal]. / Korrosionsverhalten verschiedener Schrauben und Stifte im Wurzelkanal.

A series of extracted teeth with failures in their restoration by root canal posts or screws was examined for corrosive processes on these posts and screws. The teeth were ground who make metallographic specimens. By structural analysis, measurements of hardness and by roentgenfluorescence analysis the fabricates were identified and grouped into known metal groups for such posts and screws. Corrosion was examined morphologically and discussed in connection with the type of material and the specific circumstances of its surrounding. Metal impregnation of the root was studied by microprobe. The material investigated could be classified into four groups and a characteristic behaviour of each material to corrosion could be identified. In conclusion, certain minimal properties were proposed as a guide to the use of root posts and screws.

[Dental reconstruction with non-precious metal screws and posts]. / Zahnaufbauten mit nichtedelmetallhaltigen Schrauben und Stiften.

A short review of the current methods for restoring destroyed dental crowns by mechanical retentive elements. The causes leading to failure in such restorations are mentioned in a short review of literature. Main causes are corrosive changes in posts and screws anchored in root canals. This is why a special chapter deals with the problem of corrosion. A systematic enumeration of various corrosions in posts and screws is illustrated by a choice of clinical and radiological illustrations. The author's own metallurgical analytic investigations of the posts and screws available commercially allow to divide them into 4 typical nonprecious metal groups: Inox steel, cromium nickel steel, cromium nickel molybdene steel and brass alloys. The reasons for resistance to corrosion lie in the different metallographic structures and processing methods. Further investigations are finished and will be published later in this journal.

[The dependence of the removal torque of a leg screw a screw surface and implantation time (author's transl)]. / Lösemomente von Corticaliszugschrauben in Abhängigkeit von Implantationszeit und Oberflächenbeschaffenheit

The experiment was performed on 17 sheep tibiae in vivo. 4.5 mm ASIF leg screws with a constant insertion torque (68.6 Ncm) but different surfaces (smooth or rough) were removed after 3 s, 7, 28, 56 and 112 days after insertion. The screws with a rough surface which were implanted for 28 days and longer exhibited a significantly greater removal torque. For instance rough screws which were implanted for 112 days displayed a removal torque eight times greater than after 3 s.

[Tissue reaction to an implant of a titanium hollow cylinder with a titanium surface spray layer]. / Gewebsreaktion auf ein Titan-Hohlzylinderimplantat mit Titan-Spritzschichtoberfläche

A new implant consisting of a hollow cylinder of titanium is described. It is well suited to investigate the tissue reaction to several surface textures in the animal experiment (Macaca speciosa). From a test series, for which the implants were surfaced with powdered titan (titan plasma), one was selected which had been worn for 7 months as a partial support. The solid incorporation observed radiologically presents itself, light microscopically, as an immediate growing in of the bone into the rough implant surface. There is no evidence of the formation of a soft tissue bed. Electron microscope pictures reveal that the bone closely anchored to the titan plasma surface.

[Titanium, steel and their combination in bone surgery]. / Titan, Stahl und deren Kombination in der Knochenchirurgie

The combined application of Titanium plates with stainless steel screws appeared interesting, making a more elastic plate available without the risk of screw fractures. 3 different combinations of Titanium und stainless steel implants were tested in the animal and on humans. A morphometric evaluation of the soft tissue (animal) gave similar good results for stainless steel implants as for the combination of Titanium and steel, while pure Titanium gave the best result. Atomic absorption tests (human) showed that in case of the Titanium/steel mixture only the stainless steel screws did corrode. Delayed fracture healing or mechanical instability always gave risk to more metal deposits in the soft tissue than primary bone healing. If the advantages of Titanium seem important and if the rigidity of stainless steel screws may not be missed, the combination of the two metals appears possible and without danger.