[Surgical treatment of ankle joint fractures with biodegradable screws and plates of poly-l-lactide]. / Operative Behandlung von Sprunggelenksfrakturen mit biodegradablen Schrauben und Platten aus Poly-L-Lactid.

In a first clinical protocol 19 ankle fractures have been fixed by plates and screws made of biodegradable polylactic acid. Fracture confirmation was achieved within 6 weeks. 52% of our patients demonstrated an aseptic soft tissue problem caused by delayed clearance of the degrading polylactide particles. In a 2nd protocol with 7 patients volume reduced plates and screws with flat heads were applied. None of these patients had any soft tissue reaction. These results emphasize that the application of plates and screws of polylactic acid is acceptable for fixation of ankle fractures. Soft tissue inflammatory reactions can be avoided by using volume reduced implants.

Mechanical and histological evaluation of hydroxyapatite-coated, titanium-coated and grit-blasted surfaces under weight-bearing conditions.

Cylindric titanium rods with different surfaces were axially implanted into the femora of sheep. The three surfaces were grit-blasted titanium, plasma-sprayed titanium and plasma-sprayed hydroxyapatite (HA). After 2 months, a 2-cm segment of the femoral shaft was completely resected to load the implant, and the animals were allowed full weight-bearing for 9 months. Biomechanical and histological evaluation of the implants was undertaken 2 months after implantation and 9 months after the segmental resection. The mechanical testings of well-fixed implants were performed 9 months after segmental resection. Loosening of 45% of the titanium-coated implants was observed in the first 3 weeks, but thereafter, no further loosening occurred. The HA-coated implants remained entirely fixed for 3 weeks, but thereafter, a progressively increasing incidence of loosening up to 55% after 9 months of loading was detected as subsidence on X-radiographs. The maximum push-out strength of the titanium-coated implants was 4.9 MPa compared with 2.3 MPa for HA-coated ones. No significant mechanical interlock between the grit-blasted surface and bone was observed. The HA coating was found to be delaminated in all unstable implants, whereas the titanium coating remained completely intact. Morphometric analyses of well-fixed rods showed complete bony ingrowth onto the HA surface, whereas the contact area between the bone and the two titanium surfaces was less than 40%. Concerning clinical significance bony ingrowth with long-term mechanical interlock between the implant surface and the bone cannot be achieved by grit-blasting or HA-coating.(ABSTRACT TRUNCATED AT 250 WORDS)

[Animal experiment study of tensile strength of hydroxylapatite-coated AO/ASIF Schanz screws for external fixators]. / Tierexperimentelle Untersuchung zur Haftfestigkeit von Hydroxylapatit-beschichteten AO/ASIF-Schanz-Schrauben für den Fixateur externe.

The removal torque and the loosening and infection rates of AO/ASIF 4.5 mm Schanz screws (MS) have been compared with those of hydroxyapatite-coated (HA) and hydroxyapatite/silver phosphate-coated (HA/P) AO/ASIF Schanz screws in vivo. In sheep, the left tibia was fixed after a midshaft osteotomy by means of unilateral fixator with 6 Schanz screws in an antero-lateral position. The osteotomy gap was filled with bone wax to avoid bony overgrowth. After operation, the animals were allowed to walk around immediately. The loosening rate was 2.8% at the site of the two HA-coated screws and 36% at the site of the metal screws. The removal torque after 2, 4 and 6 months was 6.2 +/- 2.8 MPa for HA/P, 4.7 +/- 2.7 MPa for HA screws and 1.2 +/- 1.1 MPa for metal screws. Histological and fluoroscopic evaluation revealed intimate bone-HA contact at the cortex near to the fixator, whereas at the site of the metal screws a fibrous tissue layer was constantly found. Only in the cortex opposite to the external fixator a direct bone-metal interface was observed. Fluoroscopic analyses confirmed new bone formation next to the HA surface especially in the cortex adjacent to the fixator, whereas such phenomena were not detected adjacent to the surface of the metal screws. Furthermore, bony resorption around the metal screws (21%) was significantly greater than around the two coated screws (2%). These experimental data suggest that pin loosening can be reduced in external fixators by coating the screws with hydroxyapatite, especially if a long-term fixation is indicated.

[Mechanical strength and chemical stability of biodegradable block-polymerized and injection molded poly-L-lactide in vitro]. / Mechanische Festigkeit und chemische Stabilität von biodegradablem blockpolymerisiertem und spritzgegossenem Poly-L-Lactid in vitro.

Biodegradable poly-L-lactic acid rods made of block-polymerized material (BP; molecular weight 550,000) and injection-moulded rods with high (SGI; molecular weight 121,000) and low (SGA, molecular weight 118,000) molecular orientation were compared 2, 4 and 6 weeks after incubation in enzyme solutions with high hydrolytic activity (esterase, alpha chymotrypsin and peptidase) and in buffer solution (TRIS buffer). The molecular weight, modulus of elasticity, bending strength (three-point bending test), and cyclic bending load to failure applied to the rods in a newly developed testing machine (1 Hz, maximum 100,000 cycles) were compared. The molecular weight of BP material decreased to 36% after 2 weeks, in contrast to the injection-moulded materials, in which it decreased only to 66% even after 6 weeks. The bending strength of all specimen decreased significantly faster in alpha chymotrypsin than in the other media (MANOVA, P < 0.001). SGI had a significantly higher bending strength than SGA, and SGA a higher strength than BP. There was no difference after incubation in the other two enzymatic solutions. BP lost 80% of its initial bending strength (140 N/mm2) after 6 weeks, and SGI and SGA (120 N/mm2) only 20%. Under permanent cyclic loading BP initially resisted 100,000 cycles with an applied cyclic load of 12.5 N/mm2, decreasing after 6 weeks to only 9,500 cycles, in contrast to SGI and SGA, which resisted to 46,000 cycles. There was, however, no relevant difference in the mechanical characteristics of the two injection-moulded rods. These results confirm that BP is degraded significantly faster than SGA and SGI.(ABSTRACT TRUNCATED AT 250 WORDS)

[The effect of hydroxylapatite coating of AO/ASIF screws on bonding strength in bones]. / Der Einfluss der Hydroxylapatit-Beschichtung von AO/ASIF-Schrauben auf die Haftfestigkeit im Knochen.

Bonding strength of hydroxyapatite-coated (HA) 4.5 mm AO/ASIF screws and of conventional AO/ASIF screws to bone has been compared in an animal experiment. A 5-hole AO/ASIF compression plate was fixed to the tibia in ten beagle dogs. The cortex beyond the central hole of the plate was resected up to the half of the diameter of the tibial shaft and over a length of 10 mm. In the holes immediately proximal and distal to the central hole either HA-coated or conventional screws were inserted with standardized force. Two conventional screws were inserted into the two holes at the ends of the plate. These screws were removed after 2 weeks. Four animals were sacrificed after 4 and 8 weeks and one animal after 16 and 26 weeks. The removal torque of HA-coated screws was 385.50 +/- 49.1 Ncm, compared with 29.50 +/- 7.62 Ncm for the conventional screws (P < 0.0001; T-test). The fluorescence and morphometric data confirmed new bone formation immediately under the HA surface without any bone resorption or intervening fibrous tissue. At the bone-implant interface of conventional screws, however, extensive bone resorption was observed and a thick intervening layer of fibrous tissue. Bone resorption of 13.6% was observed in the cortical areas under the thread of the AO/ASIF screws, in contrast to 1.9% under the surface of the HA-coated screws. These histological and biochemical data support the clinical use of HA-coated screws if early loosening of the screws is otherwise expected or removal of implants is not intended.

[Comparative studies on the ingrowth behavior and the bone adhesion of various implant materials. An animal experiment]. / Vergleichende Untersuchungen über das Anwachsverhalten und die Knochenhaftung verschiedener Implantatwerkstoffe. Eine tierexperimentelle Untersuchung.

Each of 36 mongrel dogs received implants of the following six materials: methyl methacrylate, carbon fibre composite, aluminium oxide-ceramic, titanium alloy, pure titanium and hydroxylapatite (HA). Test rods 7 mm in diameter were used to perform a push-out test, and discs with a diameter of 25 mm and a thickness of 5 mm were used for a plane traction test. The animals got a fluorochrome labelling and were harvested 8 weeks after operation. The results of the push-out test were a stability of 3.6 N/mm2 for HA and very low values for all the other materials, while the plane tension test showed a stability of 1.6 N/mm2 for the HA discs and values that were not even measurable for all the other materials. The interface of HA and the bone could not be separated by mechanical forces; usually the bone or the ceramic material fractured beneath the interface, so that the real stability of the interface must be rated very high. Light and fluorescence microscopy revealed a close bone connection for HA and only partial connections for the other materials. HA-coated materials may have a future in orthopaedics surgery.

[Semirigid plate osteosyntheses using absorbable polymers as temporary implants. II. Animal experiment studies]. / Semirigide Plattenosteosynthesen unter Verwendung absorbierbarer Polymere als temporäre Implantate. II. Tierexperimentelle Untersuchungen.

Polylactide-l test rods showed an initial stability of 130 N/mm2 in the three-point bending test; the stability decreased after implantation in the dorsal muscle of the rat within 5 weeks to about half the initial value. The copolymer materials showed less initial strength, and the stability decreased under the same conditions much earlier. All materials showed good tissue compatibility. After a transverse section of the beagle radius was stabilized with plates and screws out of polylactide-l, a delayed bony union with callus formation was observed.

[Semirigid plate osteosyntheses using absorbable polymers as temporary implants. I. Introduction, chemical composition and material-related studies]. / Semirigide Plattenosteosynthesen unter Verwendung absorbierbarer Polymere als temporäre Implantate.

Possible indications for the use of biodegradable implants are presented and the chemical compounds in question are briefly described. The results of a laboratory investigation to determine mechanical stability, tensile strength and molecular weight are reported, in order to characterize the polymers and co-polymers of the lactide under study.

[Significance of synthetic calcium phosphate ceramics as a bone replacement material]. / Die Bedeutung der synthetischen Kalzium-Phosphatkeramiken als Knochenersatzmaterial.

With reference to the chemical and crystallographic differences, the line is drawn against bone substitute material produced from biological material. Extensive animal experiments demonstrated the good healing properties when using calcium phosphate ceramics in bony defects. In the long term, there was more new bone formed after filling up the defect with calcium phosphate ceramics than when using autologous bone grafts. Clinically, there is an indication for using this material to fill up bone cysts and defects if there is enough time for biodegradation; in other cases, a mixture using an autologous spongoid graft is necessary.

Experimental and preliminary clinical experience with absorbable calcium phosphate granules containing an antibiotic or antiseptic for the local treatment of osteomyelitis.

Experimental studies on dogs with staphylococcal osteomyelitis showed that it is possible to reduce florid bone suppuration by the use of hydroxyapatite granules containing an antibiotic or antiseptic. In our series the use of flucloxacillin hydroxyapatite granules was superior to other treatment methods. Twelve patients were treated with thorough sequestrectomy, reliable wound closure and suitable stabilization supplemented with an implant of antibiotic or antiseptic hydroxyapatite granules, and an autologous spongiosa graft for large bone cavities or for discontinuity between the bone ends. The results of this preliminary study showed the treatment to be effective.

[Experience with the use of an external fixator in patients with multiple injuries]. / Erfahrungen mit der Verwendung des Fixateur externe bei polytraumatisierten Patienten.

The authors report on experiences with fixateur extern according to Raoul Hoffmann in 110 open fractures of second-degree and third-degree severity. The patient material comprised 90 patients, of which a total of 71 (79 per cent) had polytraumas. It was shown that good results can be expected if fixateur extern is applied immediately. The advantages of good positioning and care of soft parts are emphasized. A detailed discussion is devoted to the specific problems of polytraumatized patients with second-degree and third-degree open fractures.

The endoscopic multiple-diameter bougie--clinical results are after one year of application.

A new technique for dilation of the upper gastrointestinal tract permits complete endoscopic control of the whole procedure for the first time. 113 dilations have been carried out in 37 patients within a period of 15 months. The endoscopic guidance of the multiple diameter bougie positively excludes perforation resulting from the bougie's going the wrong way. With the steerable tip of the endoscope, kinking can be overcome and stenoses down to the duodenum can be dilated.

[Release delay of various antibiotics from resorbable tricalcium phosphate ceramic granules with soluble coating for local treatment of osteomyelitis. An animal experiment study]. / Die Freisetzungsverzögerung verschiedener Antibiotica aus resorbierbarem Tricalciumphosphat-Keramikgranulat durch die Verwendung löslicher Uberzüge zur lokalen Behandlung der Osteomyelitis. Eine tierexperimentelle Untersuchung.

The releasing kinetic of antibiotics from tricalcium phosphate beads was studied in animal experiments. The porous TCP-beads were filled with antibiotics and coated with biodegradable substances for delaying the release of the antibiotics. There were high tissue levels of antibiotics in the surrounding bone for many days. This method gains an increase in therapeutic safety in treatment of osteomyelitis. The coated TCP-antibiotic beads are used simultaneously as bone graft and for treatment of the bone infection. There is no need for further operation.

[Outcome of sphincter-preserving stapled colorectal anastomoses]. / Ergebnisse Sphinkter-erhaltender kolorektaler Klammernaht-Anastomosen.

Anterior colorectal end-to-end anastomosis by stapler was achieved in 61 patients between 1979 and 1981. The clinical occurrence of anastomotic leakage was 8,2%. The main advantage of the stapler is in anastomosis low in the pelvis where it allows easier access to the extraperitoneal part of the rectum. In patients with colorectal carcinoma in the middle part of the rectum the number of abdomino-perineal excisions decreased from 10,2% in 1979/80 to 3% in 1981. Recurrence of carcinoma took place in three cases after radical resection of rectosigmoidal tumor. Therefore repeated follow-up examinations with endoscopy in these cases are imperative.

Problems of dissolution after long-term placement of a Celestin oesophageal tube.

The reported cases of Latex material dissolution after longterm placement of Celestin oesophageal tubes, and the ensuing complications are discussed. Also discussed is a case of ours with adenocarcinoma of the distal oesophagus in which dissolution of the Celestin tube was found 8 months after placement. What is needed is a stable substance to replace Latex. So far, no problems have been reported with the Latex-Silicone Haering tube.

[Indications for the various surgical procedures in hepatic echinococcosis]. / Zur Indikation der verschiedenen Operationsverfahren bei Leberechinococcus.

This report deals with 38 patients suffering from hydatid disease of the liver. The most frequently performed operative procedures were hepatic resection (n = 16), filling the cavity with normal saline solution (n = 16), filling the cavity with normal saline solution (n = 8), and total cystectomy (n = 6). Hepatic resection is mainly indicated in patients with alveolar echinococcosis of the liver lobe have to be removed. In patients with only one hydatid cyst of the liver the simple method of saline filling should be preferred. The prerequisite of saline filling is that no biliary fistula exists. If the remaining cavity of the hydatid cyst fills with bile, it can be easily drained under local anaesthesia with computertomographic control. Mebendazole was given in two cases with alveolar echinococcosis of the liver that could not be treated surgically. In both cases this treatment proved to be effective.