Effect of synthetic bone replacement material of different size on shear stress resistance within impacted native and thermodisinfected cancellous bone: an in vitro femoral impaction bone grafting model.

Antibiotic carrier particles of variable size might influence mechanic properties within impacted thermodisinfected and native cancellous bone different. Herafill®G containing calciumsulfate and calciumcarbonate provides high local concentrations of gentamicin being important for revision surgery in infected joint replacements. Native and thermodisinfected cancellous bone derived from 6 to 7 months old piglets was used for in vitro impaction bone grafting and supplemented each with Herafill®G granules of two different sizes. Micromovement of implants related to shear force was measured in 29 specimens distributed in 6 groups. Thermodisinfected cancellous bone revealed a significant higher shear force resistance than native bone with a mean difference of 423.8 mdeg/Nm (p < 0.001) ranging within 95% confidence interval from 181.5 to 666.0 mdeg/Nm. Adding small granules to thermodisinfected bone did not reduce shear force resistance significantly since adding large granules to native bone improved it by 344.0 mdeg/Nm (p < 0.003). Shear force resistance was found higher at the distal region of the implant compared to a proximal point of measurement throughout all specimens. Less impaction impulses were necessary for thermodisinfected bone. Thermodisinfected cancellous bone might achieve a higher degree of impaction compared with native bone resulting in increased resistance against shear force since impaction was found increased distally. Supplementation of thermodisinfected bone with small granules of Herafill®G might be considered for application of local antibiotics. Large granules appeared more beneficial for supplementation of native bone. Heterogeneity of bone graft and technical aspects of the impaction procedure have to be considered regarding the reproducibility of femoral impaction bone grafting.

[Allogeneic bone transplantation in hip revision surgery : Indications and potential for reconstruction]. / Allogene Knochentransplantation in der Hüftrevisionsendoprothetik : Indikationen und Rekonstruktionsmöglichkeiten.

The increasing number of people having joint replacements will lead to increasing numbers of revision operations. The transplantation of allogeneic bones might reconstruct bone defects and improve long-term anchorage of the implant. A sufficient primary stability of the implanted construct is necessary to achieve osseous incorporation as well as tight contact between the implanted allogeneic and host bones. Transplantation of bone can contribute to downgrading acetabular defects and so avoid bigger reinforcement implants. An improvement of bone stock due to reconstruction of femoral bony defects might also reduce the size of the stem necessary since the indication might be limited in case of extensive bone defects. According to good longterm results of modular revision stems the Impaction-Bone-Grafting has not yet generally been established.

[Influence of thermodisinfection on impaction of cancellous bone : An in vitro model of femoral impaction bone grafting]. / Einfluss der Thermodesinfektion auf die Impaktion spongiöser Knochen : Ein In-vitro-Modell für das femorale Impaction-Bone-Grafting.

BACKGROUND: The reconstruction of bony defects during endoprosthesis revision surgery using "impaction bone grafting" leads to the possibility of a longstanding osseous integration to achieve good clinical results. Native allogeneic cancellous bone is often used for the procedure. This study examines the influence of thermodisinfection on the impaction behaviour of cancellous bone of different geometries and on the cement distribution. METHODS: The cancellous bone was obtained from the femoral heads of 7­month old pigs. One half of the head was thermodisinfected while the other remained native. Bone chips with sizes of 3-5, 5-8 and 8-10 mm were produced. The impaction was performed in a cylinder model with an internal diameter of 30 mm and with standardized impaction force using an impactor with a weight of 1450 g. The best particle combination was used for the subsequent computer tomography examination of the cement distribution and the contact surface to the bone in different parts of the shaft in seven investigations. For statistic measurements two-dimensional variance analysis including repetitions of measurement and Bonferroni correction, the LSD post-hoc-zest and the Mann Whitney U Test were used. The error probability was set at α = 5%. The SPSS® for Windows software was used for the statistical analysis. RESULTS: The distribution of the cancellous and compacted bone also along the shaft revealed no significant difference between thermodisinfected and native cancellous bone at different levels (p > 0.05). Impacted native cancellous bone showed less inclusion of air, which resulted in a better distribution of density compared with thermodisinfected bone overall (p < 0.001). In the distal shaft area the cement volume was significantly larger in conjunction with the native bone. The overall area of cement penetration appeared to be significantly larger for native cancellous bone (p < 0.001). CONCLUSIONS: The impaction of thermodisinfected and native cancellous bone showed greater deformation of the processed bone without any significant difference in the maximum density reached at different levels. Cement volume and cement penetration were pronounced proximally in native and processed cancellous bone. The cement distribution was significantly more distal for the native bone. Distally, the stabilization of the shaft appears to be increasingly dependent on the density of the impacted spongiosa, while proximally, the penetration of the cement into cancellous bone seems to correlate with porosity.

[Surgical treatment of acetabulum fractures in the elderly. Osteosynthesis or endoprosthesis]. / Operative Therapie der Acetabulumfraktur beim älteren Patienten. Osteosynthese oder Endoprothese.

BACKGROUND: Anatomical reconstruction of acetabulum fractures and rigid osteosynthesis are required to achieve good postoperative results. In the 7(th) decade of life changes of bone quality impair stability of fixation devices in bone. PATIENTS AND METHODS: This retrospective study evaluates and compares results of osteosynthesis and implantation of total hip arthroplasty in patients with acetabulum fractures. A total of 24 patients older than 65 years who sustained acetabular fractures type A, B and C according to AO classification were examined using several clinical measurements. Different scores for physical function, pain, general health and subjective assessment including psychosocial aspects were used. The outcome criteria were evaluated 1.5-10 years after surgery. RESULTS: Good reconstruction of the acetabulum was only achieved in 40 % of patients which corresponded with radiological long-term results. Pain relief and mobility were slightly better in patients who received primary alloarthroplasty of the hip joint, and periarticular ossification was observed more frequently following osteosynthesis. Surgical revisions were necessary more often after osteosynthesis of the acetabulum. The small number of cases showed no significant differences. The functional outcome did not show significant differences between primary alloarthroplasty and reconstruction of the acetabulum. CONCLUSION: Primary implantation with alloarthroplasty of the hip joint in case of a complex fracture of the acetabulum can be recommended for elderly patients if an anatomic or good reconstruction of the hip joint cannot be achieved.

[Biocompatibility of polymer-bioglass cement Cortoss®: in vitro test with the MG63 cell model]. / Biokompatibilität von Polymer-Glaskeramik-Zement Cortoss®: In-vitro-Testung mit dem MG63-Zell-Modell.

BACKGROUND: Polymethylmethacrylate (PMMA) cement has been used for fixation of joint replacements for more than 50 years and cement augmentation of vertebrae has become a popular procedure since the first description in 1987. New cements have now been developed which are better suited to the requirements of minimally invasive application techniques for vertebral bodies. The combination of good mechanical properties and biocompatibility is the concern of present research. This study compared the features of a polymer-bioglass cement with a calcium phosphate cement used for vertebral augmentation. METHODS: The human osteoblast-like cell culture MG63 was used to study the polymer-glass ceramic cement Cortoss® and the hydroxyapatite cement Kyphos®. Every 24 h for 5-6 days a defined volume of the culture medium was harvested in the presence of the bone cements and added to 16 cell cultures for each time period. The viability of cells was determined photometrically at 550 nm with the MTT assay and cell morphology was studied using light and electron microscopy. RESULTS: In the presence of the calcium phosphate cement an early and small reduction of cell activity was found compared with the controls. At the end of 1 week the viability parameter improved nearly reaching the control level. Electron microscopy showed crystals with a 3-dimensional shape. The cell cultures with Cortoss® showed no cellular activity and the microscopic examinations were negative. This effect was not different at days 1-5 after polymerization of the cement. CONCLUSIONS: The calcium phosphate cement studied showed a good biocompatibility and allowed morphological signs of apatite formation. At least within the first 5 days the polymer-glass ceramic cement showed a reasonable cytotoxic effect. There was no sign of recovery of cell function within that period. The biocompatibility of the polymer-glass ceramic cement appeared significantly worse compared with the calcium phosphate cement. An ideal composition of biomechanical properties and biocompatibility has not been achieved so far.

Palmitic acid coating of allogeneic cancellous bone for local antibiotic treatment: A porcine impaction bone grafting model.

Introduction: The worldwide rising number of joint replacements results in increasing revision surgery including a relevant portion of septic loosening accompanied by bone deficiencies. Loading of allogeneic bone with antibiotics provides high local antibiotic concentrations and might eradicate bacteria which appear resistant to systemic antibiotic application. Hydrophobic palmitic acid was shown to be a suitable carrier for antibiotics and prevents biofilm. Methods: Cancellous bone derived from 6 to 7 months old piglets was used for a standardized in vitro impaction bone grafting model according to previous studies. The specimens were either thermodisinfected or remained native and palmitic acid with one third and two third partial weight were added and compared with control. Shear force at the interface prosthesis to cement and between cement and bone was measured. The relative micromovements were measured with 6 inductive sensors with a resolution of 0.1 µm at three different measuring heights up to a maximum movement of 150 µm between cement and bone. Taking into account the corresponding applied torque the measured values were normalized in µm/Nm. Statistical analysis was done with SPSS Statistics® Version 26.0 IBM. Results: Smallest movement was measured for thermodisinfected cancellous bone and a not significant decrease of shear force resistance with addition of palmitic acid was found since supplementing native cancellous bone reduced shear force resistance significantly depending on the weight percentage of palmitic acid. Conclusion: Supplementation of porcine cancellous bone with palmitic acid did not significantly reduce shear force resistance of thermodisinfected bone since adding palmitic acid to native bone decreased it significantly depending on the volume added. Palmitic acid seems to be a suitable coating for allogeneic cancellous bone to deliver high local antibiotic concentrations and thermodisinfected cancellous bone might be able to store larger volumes of palmitic acid than native bone without relevant influence on shear force resistance.

Influence of antibiotic pellets on pore size and shear stress resistance of impacted native and thermodisinfected cancellous bone: An in vitro femoral impaction bone grafting model.

INTRODUCTION: Morphology and mechanic properties of impacted cancellous bone are affected by carrier substances which provide high local concentrations of antibiotics. METHODS: Bone chips were taken from the femoral head of 6-7 months old piglets. One half was thermodisinfected and the other remained native. Ten specimens each were mixed with Herafill® antibiotic pellets and a control group of each 10 specimens respectively was examined. The cancellous bone was impacted according to Exeter technique and the implants were cemented. The distribution of the particles and the pores were defined with three dimensional computertomographic scan and shear force resistance was measured until failure. RESULTS: Shear force resistance was not measured significantly less for thermodisinfected (2.7 Nm) compared with native bone (3.5 Nm) and addition of antibiotic pellets reduced shear force resistance in both groups since this was significant for the native group. The average pore volume of the native bone specimens appeared significant smaller compared to the thermodisinfected group (p = 0.011) and the pore volume showed a negative correlation with shear force resistance (p = 0.044). Pore volume around the pellets was found significantly increased and it appeared smaller for native bone. The number of pellets located next to the implant showed a negative correlation with shear force resistance (p = 0.034) and the negative correlation increased for pellets below the tip of the shaft model (p = 0.024). CONCLUSION: Adding antibiotic pellets to native and thermodisinfected impacted cancellous bone increased pore volume since the area around the pellets showed increased porosity which correlated with reduced shear force resistance. Computertomographic three dimensional measurement of porosity might predict shear force resistance of impacted cancellous bone and improve impaction of bone grafting intraoperatively.

[Arteriovenous fistula after endoscopic dissection of the perforant vein of the lower leg with the neodymium:YAG laser in chronic venous stasis syndrome]. / Arterio-venöse Fistel nach endoskopischer Dissektion der Venae perforantes des Unterschenkels mit dem Neodym: YAG-Laser bei chronischem venösem Stauungssyndrom.

The endoscopic dissection of the perforating veins has been invented by Hauer in the last decade. He introduced the videoendoscopy to this surgical procedure. The avoidance of operative access through areas of trophic changes is very beneficial for reducing postoperative complications. Although postoperative thermic lesion have been reported on. Following an endoscopic laser coagulation of a Cockett perforating vein an arterio-venous fistula between the posterior tibial artery and vein developed by the mechanism mentioned. Persisting pain and the persistence of the ulcer led to several diagnostic measures including phlebography, digital subtraction angiography and CT-scan. After the fistula had been closed successfully by percutaneous embolization with four platin wires the ulcer disappeared.

[Sonographic screening of the newborn hip at the university hospital Marburg--a long-run analysis]. / Sonografisches Screening der Neugeborenenhüfte am Universitätsklinikum Marburg--eine Langzeitanalyse.

BACKGROUND: Since 1985 the hips of the newborns have been sonographically screened at the University Hospital Marburg by staff of the Orthopaedic Department. This study was conducted to collect data on the local incidence of DDH (developmental dysplasia of the hip). Moreover, the diagnostic findings were checked critically to detect weak points. Another aim was to analyse the influence of investigators' experience on the treatment recommendation. MATERIAL AND METHODS: In a retrospective study, 18 247 hip sonograms in a treatment period from 1985 to 2009 were analysed. The following parameters were evaluated: perinatal incidents (e.g., breech presentation, Caesarean section, premature delivery), orthopaedic findings (e.g., club foot, limitation of hip abduction). Bony roof, superior bony rim and cartilaginous roof were analysed; α- and ß-angles and hip type according to Graf were documented. Comparisons between variables were calculated by means of adequate statistic tests. χ(2)-values and coefficients of correlation were used to detect significance. RESULTS: All in all 55 physicians of our Orthopaedic Department conducted 350 measurements on average (min. 1; max. 1993). Accuracy of documentation improved over time. In particular in the beginning of the screening, the hip angles according to Graf were not completely determined and sonograms were classified by "visual diagnosis". The ß-angle was not measured at the outset. In the course of time we measured a decrease of the diagnosis hip type II a according to Graf. In the years 1985-1989 more than 40 % of the hips were described as physiologically immature. We evaluated a numerical regression of hip type II a to 16 % in time period 1990-1994 and 9 % in time period 2005-2009. There was a significant correlation between breech presentation and decentering and eccentric hips. Inexperienced physicians recommend more often therapeutic interventions (p ≤ 0.01). Treatment of hip type II a according to Graf was inconsistent over time. CONCLUSION: This study demonstrates the necessity of standardised hip sonography. Treatment according to measured hip type should be concise. Training programmes both for instructors and medical assistant staff is mandatory. "Bedside teaching" is not constructive.

PMMA-augmentation of incompletely cannulated pedicle screws: a cadaver study to determine the benefits in the osteoporotic spine.

BACKGROUND: Pedicle screw pullout due to poor bone quality, mainly caused by osteoporosis, is a common problem in spine surgery. Special implants and techniques, especially PMMA augmentation, were developed to improve the fixation of pedicle screws. PMMA injection into a pilot hole or through a screw involves the same risks as vertebroplasty or kyphoplasty, regardless of the technique used. Especially when using fully cannulated screws anterior leakage is possible. OBJECTIVE: To prove PMMA injection is safe and possible without leakage through an incompletely cannulated screw and also increases pullout forces in the osteoporotic vertebra. METHODS: Incompletely cannulated pedicle screws were tested by axial pullout in human cadavers, divided into osteoporotic and non-osteoporotic groups. Non-augmented and PMMA-augmented pedicle screws were compared. Twenty-five human vertebrae were measured by DEXA and divided into osteoporotic and non-osteoporotic groups. In each vertebra both pedicles were instrumented with the new screw (WSI-Expertise 6×45 mm, Peter Brehm Inc. Germany); the right screw was augmented with a 3 mL PMMA injection through the screw. On each screw axial pullout was performed after X-ray and CT scan. RESULTS: Radiographs and CT scans excluded PMMA leakage. Cement was distributed in the middle and posterior third of the vertebrae. Pullout forces were significantly higher after pedicle screw augmentation, especially in the osteoporotic bone. All augmented pedicle screws showed higher pullout forces compared with the unaugmented screws. CONCLUSIONS: We minimized the risk of leakage by using a screw with a closed tip. On the whole, PMMA augmentation through an incompletely cannulated pedicle screw is safe and increases pullout forces in osteoporotic bone to the level of healthy bone. Therefore the new incompletely cannulated screw can be used for pedicle screw augmentation.

[Cross sectional study of structural quality of German intensive care units. A reevaluation of the DIVI register]. / Querschnittstudie der Strukturqualität deutscher Intensivstationen. Eine Reevaluation der Strukturdaten des DIVI-Registers.

BACKGROUND: Effectiveness of intensive care treatment is essential to cope with increasing costs. The German national register of intensive care established by the German Interdisciplinary Association for Intensive Care Medicine (DIVI) contains basic data on the structure of intensive care units in Germany. A repeat analysis of data of the DIVI register within 8 years provides information for the development of intensive care units under different economic circumstances. METHODS: The recent data on the structure of intensive care units were obtained in 2008 and compared with the primary multicenter study from 2000. The hospitals selected were a representative sample for the whole of Germany. Data on the status of the hospital, staff and technical facilities, foundation of the hospital and the statistics of mechanically ventilated patients were analyzed. RESULTS: The technical facilities and the number of staff have improved from 2000 to 2008. A smaller availability of diagnostic procedures and staff remain in hospitals for basic treatment outside normal working hours. The average utilization of intensive care unit beds was not altered. The existence of intermediate care units did not significantly change the proportion of patients with artificial ventilation or ventilation times. The number of beds in intensive care units was unchanged as was the average number of beds in units and the number of patients treated. A relevant number of beds of intensive care units shifted towards hospitals with private foundation without changes in the overall numbers. The structure of the hospitals was comparable at both time points. CONCLUSIONS: The introduction of intermediate care units did not alter ventilation parameters of patients in 2008 compared with 2000. There is no obvious medical reason for the shift of intensive care beds towards private hospitals. The number of staff and patients varied considerably between the intensive care units. The average number of patients treated per bed was not different between the periods or between hospitals with different structures. Overall availability of medical staff and diagnostic procedures increased during the study period. An increase of availability of fully trained medical staff in intensive care medicine is desirable to increase the quality of treatment.

[PMMA augmentation of pedicle screws: results of a survey in Germany]. / PMMA-Augmentation von Pedikelschrauben: Ergebnisse einer Umfrage in Deutschland.

BACKGROUND: The anchorage of pedicle screws can be challenging in the osteoporotic spine. A promising technique are cement augumented pedicle screws. The goal of this study was to gain more information regarding application of pedicle screw augmentation in Germany. MATERIALS AND METHODS: Participants of the National German Spine Congress 2009 were invited to participate in an internet-based anonymous survey regarding application of pedicle screw augmentation. The questionnaire was related to different aspects of materials and procedures for pedicle screw augmentation. The frequency of answers was divided according to the specialty state of the surgeons: orthopaedic and trauma surgeons vs. neurosurgeons. The Mantel-Haenszel test was applied to evaluate the differences between the groups. RESULTS AND CONCLUSION: 69 (64 %) orthopaedic and trauma surgeons and 39 (36 %) neurosurgeons participated (n = 108). Nearly 80 % of the participants use cement-augmented pedicle screws in their daily practice. Almost 2/3 of the specialists apply cannulated screws or other special screws. The Expedium (Company) screws are particularly preferred. The insertion of screws is combined with kyphoplasty or vertebroplasty in 20 % of the cases. The balloon kyphoplasty was applied most commonly. There was no statistical difference between the surgeon groups regarding the different techniques. The main indications for pedicle screw augmentation were osteoporosis, intraoperative findings as well as loosening of screws, and revision. The most frequently observed complication is cement extravasation into the spinal canal (28 %). The cost issue is considered as being important but unknown to most of the participants. It can be assumed that the use of pedicle screws in Germany is well established in spine surgery, without as yet a standard technique being established.

[Osteosynthesis of subtrochanteric femoral fractures with the dynamic condyle screw]. / Die Osteosynthese subtrochanterer Femurfrakturen mit der Dynamischen Kondylenschraube.

The dynamic condyle screw was originally designed for osteosynthesis of distal femoral fractures. Because of more favourable biomechanical facilities compared with the condyle plate we have been used the implant since 1987. This investigation is based on 40 patients with pertrochanteric, subtrochanteric as well as proximal diaphyseal fractures. The majority of the patients were mobilized early and reached full weight bearing latest after 3 months according to the fracture type. The most severe complications appeared with subtrochanteric fractures with lack of medial cortical support. There was a broken plate in 2 cases and a secondary spongiosa plastic was necessary in 3 cases to ensure bony consolidation. As the point of this investigation we will see a wider indication for primary spongiosa plastic and early secondary spongiosa plastic.