Influence of thermodisinfection and duration of cryopreservation at different temperatures on pull out strength of cancellous bone.

Thermodisinfection of human femoral heads from living donors harvested during hip joint replacement is an established processing procedure. This study was designed to examine the influence of heat sterilization on pull out strength of cancellous bone and storage at different temperatures up to 2 years since we had previously studied the storage of unprocessed cancellous bone. Porcine cancellous bone resembling human bone structure was obtained from 140 proximal humerus of 6-8 months old piglets. Pull out strength of screws after thermodisinfection was compared with unprocessed cancellous bone and tested immediately and after 6, 12 and 24 months of storage at -20 and -80 °C. A three-way ANOVA was performed and significance level was 5 %. The thermodisinfected bone showed a pull out force of 2729 N (1657-3568 N). The reduction of pull out strength compared with unprocessed bone over all periods of storage was 276 N on average with 95 % confidence interval ranging from 166 N to 389 N (p < 0.0001). Different freezing temperatures did not influence this mechanic property within 24 months storage and showed no difference compared with fresh frozen bone. Thermodisinfection of cancellous bone preserves tensile strength necessary for clinical purposes. The storage at -20 °C for at least 2 years did not show relevant decrease of pull out strength compared with -80 °C without difference between thermodisinfected and fresh frozen bone. The increase of the storage temperature to -20 °C for at least 2 years should be considered.

Effect of Storage Temperature on Allograft Bone.

BACKGROUND: The recommendations for storage temperature of allogeneic bone are varying between -20 °C and -70 °C and down to -80 °C. The necessary temperature of storage is not exactly defined by scientific data, and the effect of different storage temperatures onto the biomechanical and the biological behavior is discussed controversially. METHODS: The historical development of storage temperature of bone banks is described. A survey on literature concerning the biomechanical and biological properties of allograft bone depending on the procurement and storage temperature is given as well as on national and international regulations on storage conditions of bone banks (European Council, American Association of Tissue Banks (AATB), European Association of Tissue Banks (EATB)). RESULTS: Short-term storage up to 6 months is recommended with -20 °C and -40 °C for a longer period (AATB), and EATB recommends storage at -40 °C and even -80 °C while the regulations of the German German Medical Association (Bundesärztekammer) from 2001 recommend storage at -70 °C. Duration of storage at -20 °C can be maintained at least for 2 years. The potential risk of proteolysis with higher storage temperatures remains, but a definite impairment of bone ingrowth due to a storage at -20 °C was not shown in clinical use, and no adverse biomechanical effects of storage at -20 °C could be proven. CONCLUSION: Biomechanical studies showed no clinically relevant impairment of biomechanical properties of cancellous bone due to different storage temperatures. Sterilization procedures bear the advantage of inactivating enzymatic activity though reducing the risk of proteolysis. In those cases a storage temperature of -20 °C can be recommended for at least a period of 2 years, and the risk of undesired effects seems to be low for native unprocessed bone.

The sternal fracture: radiographic analysis of 200 fractures with special reference to concomitant injuries.

BACKGROUND: The assessment of the sternal fracture and concomitant injuries is discussed. METHODS: Two hundred sternal fractures were analyzed with respect to accident circumstances, fracture morphology and topography, and associated injuries. RESULTS: Traffic accidents were frequent; 89.2% of them were motor vehicle crashes of restrained passengers, 76.5% of fractures were localized in the corpus sterni, and 8.5% of the injuries resulted in fractures or complete disruptions of the synchondrosis manubriosternalis. Nondisplaced or slightly displaced fractures (75.5%) occurred more frequently compared with moderately and severely displaced fractures (24.5%). In 29.5% of the patients, concomitant thoracic injuries were diagnosed. Spinal fractures were evaluated in 13%. In displaced fractures of the corpus, thoracic and cardiac injuries were observed frequently. In fractures or disruptions of the synchondrosis manubriosternalis, concurrence of spinal fractures clearly increased. CONCLUSION: The observation of fracture morphology and topography, with reference to displacement, gives important information about the existence of serious concomitant injuries and can determine further diagnostic and therapeutic options in sternal fractures.

Validation of the 'Marburg bone bank system' for thermodisinfection of allogenic femoral head transplants using selected bacteria, fungi, and spores.

The Marburg Bone Bank System 'Lobator sd-2' is widely used to process human femoral heads removed during aseptic surgery by thermal disinfection. The inactivating capacity of the thermodisinfection system was validated in compliance with current standards using a newly developed femoral head model. The following micro-organisms, bacteria and fungi, taken from the American Type Culture Collection were investigated: Staphylococcus aureus, Staphyloccus epidermidis, Enterococcus faecium, Pseudomonas aeruginosa, Bacillus subtilis including spores, Clostridium sporogenes, Mycobacterium terrae, Candida albicans and Aspergillus niger spores. Highly enriched suspensions of these micro-organisms were applied to the centre of the femoral heads. The reduction in the number of micro-organisms was determined by counting the colony-forming units (cfu) before and after processing the spiked test device in the 'Lobator sd-2' system. Vegetative bacteria, fungi and fungal spores were completely inactivated (reduction factor >/=6 log(10)). The numbers of B. subtilis and C. sporogenes spores, both known to be heat-resistant, were reduced by one to two orders of magnitude. These bacteria serve as a model for spore forming pathogens which are not relevant in femoral heads from living donors. By processing human femoral heads from living donors by thermal disinfection using the Marburg Bone Banking system, a high level of safety is achieved regarding clinically relevant pathogens. To further increase the safety of the thermally treated femoral heads, we recommend that the medical history and present state of the donor, as well as the necessary serological tests should be taken into account.

Lavage of contaminated surfaces: an in vitro evaluation of the effectiveness of different systems.

INTRODUCTION: Lavage is an effective, additive therapeutic procedure with a broad application in surgery. In addition to irrigation with the conventional syringe, the pulsed jet lavage system is used. The effectiveness of bacterial reduction depends on, among other things, the irrigation pressure. Complications of high-irrigation pressure in bone and joint surgery are intramedullary seeding of bacteria, visible damage of the bone, or delayed healing of the fracture by lavage of the fracture zone. The purpose of this in vitro study was to evaluate the effectiveness of mechanical irrigation on several surfaces using different systems of irrigation. MATERIALS AND METHODS: Four different test surfaces (nonbiological surfaces: sterilized bone cement and titanium osteosynthesis plates; biological surfaces: gamma-irradiated bovine muscle and cancellous bone) were contaminated with a defined suspension of different bacterial species (Staphylococcus aureus, Enterococcus faecalis, Pseudomonas aeruginosa). The samples were irrigated with three different systems (conventional 50-ml plastic syringe, manual pump irrigator, jet lavage) in a standardized, randomized experimental setup. After irrigation of the sample the amount of residual bacteria (colony-forming units) was determined. RESULTS: An effective bacterial reduction was achieved with the use of irrigation regardless of the system that was used and surface that was cleaned. On average P. aeruginosa was reduced around log 1.907, E. faecalis around log 1.666 and S. aureus around log 1.506. On biological surfaces, a reduction around log 0.801 for muscle and around log 1.738 for bone samples was achieved independent of the system that was used for irrigation. For the titanium surface a reduction of log 1.652 compared with log 2.580 for the bone cement surface was demonstrated. Statistical analysis showed that mechanical lavage resulted in a significant reduction of all tested bacterial species on the surfaces. The best bacterial reduction was achieved with the manual pump irrigator (P = 0.06). The results demonstrate that the manual pump irrigator achieved significantly better bacterial reduction (P = 0.039) on "biological surfaces" (bone and muscle) compared with nonbiological surfaces (titanium and cement). CONCLUSION: The results show that irrigation is an effective technique for bacterial reduction on contaminated surfaces. A remarkable finding was the limited bacterial reduction of Staphylococcus aureus from gamma-sterilized muscle. The use of a continuous manual pump irrigator showed a greater reduction of bacteria contamination compared with the other means of irrigation investigated. In conclusion, the manual continuous irrigation system proved to be practical, economical and effective in reducing the bacterial load on various surfaces.

Virus inactivation in bone tissue transplants (femoral heads) by moist heat with the 'Marburg bone bank system'.

Several virus inactivation procedures like heat treatment, gamma irradiation and chemical sterilization are used to increase the safety of bone tissue transplants. In this study we present data on the virus-inactivating effect of heat disinfection on human femoral heads, using the Marburg bone bank system 'Lobator sd-2'. Three enveloped viruses (human immunodeficiency virus type 2 [HIV-2], bovine viral diarrhoea virus as a model for Hepatitis C virus [HCV], and the herpesvirus pseudorabies virus), and three non-enveloped viruses (hepatitis A virus, poliomyelitis virus, and bovine parvovirus) were investigated. In a model system the central part of human femoral heads was contaminated with the respective cell-free virus suspension, establishing a direct contact between virus and native bone tissue. The core temperature in the femoral heads during the sterilization process was determined in additional model experiments. A temperature of 82.5 degrees C, given by the manufacturer as the effective temperature for virus inactivation, was maintained for at least 15 min in decartilaged femoral heads with a diameter of < or = 56 mm. Heat treatment using the Lobator sd-2 inactivated all viruses in human femoral heads below the detection limit (at least by a factor of > or =4 log(10)). By combining a well-focussed anamnesis of the donors and serological testing for relevant infection markers (anti-HIV-1/2, HBsAg, anti-HBcore, anti-HCV, TPHA) with heat treatment of femoral heads in the Lobator sd-2 system, a high safety level is achieved. To further increase virus safety of cadaveric bone transplants, it is recommended that multi-organ donors are tested by nucleic acid testing (i.e. polymerase chain reaction) for HIV, HBV and HCV genome.