Cell-free repair of small cartilage defects in the Goettinger minipig: which defect size is possible?

PURPOSE: Cartilage repair of full-thickness chondral defects in the knees of Goettinger minipigs was assessed by treatment with cell-free collagen type-I gel plugs of three different sizes. METHODS: In 6 adult Goettinger minipigs, three full-thickness chondral defects were created in the trochlear groove of one knee of the hind leg. These defects were treated with a cell-free collagen type-I gel plug of 8, 10, or 12 mm diameter. All animals were allowed unlimited weight bearing. After 1 year, the animals were killed. Immediately after recovery, a non-destructive biomechanical testing was performed. The repair tissue quality was evaluated immunohistologically, collagen type-II protein was quantified, and a semiquantitative score (O'Driscoll score) was calculated. RESULTS: After 1 year, a high number of cells migrated into the initially cell-free collagen gel plugs and a hyaline-like repair tissue had been created. The O'Driscoll scores were: 8 mm, 21.2 (SD, 2.8); 10 mm, 21.5 (SD, 1.6); and 12 mm, 22.3 (SD, 1.0). The determination of the e-modulus, creep and relaxation revealed that mechanical properties of the two smaller defects were closer to unaffected hyaline cartilage. CONCLUSIONS: As cell-free collagen type-I gel plugs of all three different sizes created hyaline-like repair tissue, this system seems suitable for the treatment of even larger defects.

[Analysis of 18F-FDG uptake pattern in PET for diagnosis of aseptic loosening versus prosthesis infection after total knee arthroplasty. A prospective pilot study]. / Analyse des 18F-FDG-Speichermusters in der PET zur Differenzierung zwischen aseptischer Prothesenlockerung und Protheseninfektion - Eine prospektive Pilotstudie.

UNLABELLED: The AIM of this prospective study was to identify a typical pattern for fluorodeoxyglucose (18F-FDG) uptake in positron emission tomography (PET) to differentiate aseptic loosening (tibial and / or femoral component) from prosthesis infection in painful knee prosthesis. PATIENTS, METHODS: 20 patients with painful knee prosthesis underwent PET imaging to evaluate aseptic loosening / prosthesis infection of their knee prosthesis. The interface between bone and surrounding soft tissue or bone was divided into 3 segments each for both the femur and the tibia and in addition for 4 segments reflecting the surrounding periprosthetic soft tissue. FDG uptake in each of the segments was scored (0-3) by two independent observers. The final diagnosis was based on operative findings with subsequent microbiological culture and histological examination. RESULTS: After surgical revision 6 femoral components and 5 tibial components were found to be loose and prosthetic infection was present in 9 prostheses. In 8 of 9 infected prostheses loosening of the femoral und tibial component occurred. There was no statistically significant correlation between the standardised uptake within each of the segments and the diagnosis of aseptic loosening or prosthesis infection. A differentiated qualitative and quantitative FDG-PET result interpretation divided into five categories was developed. Specificity / sensitivity / positive predictive value / negative predictive value were 93% / 83% / 83% / 93% for aseptic loosening of the femoral component, 87% / 80% / 67% / 93% for aseptic loosening of the tibial component and 82% / 89% / 80% / 90% for infection. CONCLUSION: This pilot study shows that FDG-PET is a promising diagnostic tool for patients with painful knee prostheses. There is a good correlation between PET images and the intraoperative and pathology findings. Its clinical value, however, warrants further evaluation in a larger patient population.

Trackerless ultrasound-integrated bone cement detection using a modular minirobot in revision total hip replacement.

Medical robots are superior to freehand manipulation if an accurate, precise, and time-efficient implementation of a preplanned intervention is required. In the first part of this contribution a new modular minirobot for automatic ultrasound-based bone cement detection followed by subsequent cement milling in revision total hip replacement is presented. A minirobot integrated ultrasound module eliminates the need for external position tracking (e.g. by an optical system) as well as patient registration since the scanned contours can be directly provided within the robot's coordinate system. Further, the modular minirobot concept allows kinematics, workspace, and mechanical parameters to be easily adapted to the requirements of related or even new surgical applications. In the experimental part, the impact of ultrasound module integration on the implementation of optimized scanning strategies is investigated and evaluated in a laboratory set-up. As wave mode conversion and refraction artefacts due to angular sound incidence influence the detection accuracy, the transducer alignment can be optimized with respect to the number of degrees of freedom (DOFs) provided by the minirobot. A model-based scanning approach using two degrees of freedom (2DOFs), three degrees of freedom (3DOFs), and four degrees of freedom (4DOFs) respectively is presented. For automated scanning path calculation, a 2DOF distal-proximal prescan has been performed to estimate the principal components of the cement cavity's geometry using either a model-based or a statistical approach. In a cadaver study, the model-based approach consistently outperformed the statistical approach. The 3DOFs and 4DOFs scanning strategies yielded a significantly higher scanning accuracy if compared with the 2DOFs approach whereas the 3DOFs approach represents a trade-off between system complexity and detection accuracy.

Evaluation of a new fluoroscopy-based navigation system in the placement of the femoral component in hip resurfacing.

Prosthesis-specific mechanical alignment instruments for the precise and reproducible positioning of the femoral component constitute one of the major improvements in modern hip resurfacing prostheses. However, mechanical failure of the femoral component is mostly attributable to the surgical technique, and in particular to notching of the femoral neck. In order to evaluate a novel computer-assisted fluoroscopy-based planning and navigation system, six DUROM hip resurfacing prostheses were implanted into artificial femurs by means of computer-assisted fluoroscopy-based navigation and prosthesis-specific mechanical alignment instruments. Subsequently, the planning and navigation system was tested within the scope of a cadaver study on three fixed whole-body preparations (six femurs). The average difference between planned and actual angle of the prosthesis was 0 +/- 0.7 degrees for fluoroscopy-based navigation versus 6.5 +/- 7.8 degrees for the in-vitro use of the prosthesis-specific mechanical alignment instruments, and 1 +/- 1.4 degrees for fluoroscopic navigation in the cadaver study. The average discrepancy between planned and actual anterior offset was -1.2 +/- 1.2 mm versus 0.8 +/- 4 mm, and 0.3 +/- 2.2 mm in the cadaver study, and the time required for the total of five planning and navigation steps was 17.2 +/- 1.5 min versus 14 +/- 0.8 min and 20.2 +/- 2.5 min respectively. No notching of the femoral neck occurred under fluoroscopy nor under conventional treatment. During in-vitro studies, use of the computer-assisted fluoroscopy-based planning and navigation system resulted in enhanced accuracy compared with conventional prosthesis-specific mechanical alignment instruments. The system has yielded initial promising results within the scope of the cadaver study.

In vitro interface and cement mantle analysis of different femur stem designs.

The aim of this study is to define stem design related factors causing both gaps in the metal-bone cement interface and cracks within the cement mantle. Six different stem designs (Exeter; Lubinus SP II; Ceraver Osteal; Mueller-straight stem; Centega; Spectron EF) (n=15 of each design) were cemented into artificial femur bones. Ten stems of each design were loaded, while five stems served as an unloaded control. Physiologically adapted cyclical loading (DIN ISO 7206-4) was performed with a hip simulator. After loading both interfaces and the bone cement itself were analysed regarding gaps and cracks in the cement mantle. Significant differences between the stem designs concerning gaps in the metal-bone cement interface and cracks in the cement mantle became apparent. Additionally, a high correlation between gaps in the metal-bone cement interface and cracks within the cement mantle could be proven. Gaps in the metal-bone cement interface but no cracks within the cement mantle were seen in the unloaded specimens. Differences between the unloaded control groups and the cyclical loaded stems regarding the longitudinal extension and width of gaps in the metal-bone cement interface were obvious. The designs of cemented femoral stems have an influence on both the quality of the metal-bone cement contact and the failure rate of the cement mantle. Less interface gaps and less cement defects were found with anatomically formed, collared, well-rounded stem designs without undercuttings.

A novel rat tail collagen type-I gel for the cultivation of human articular chondrocytes in low cell density.

Collagen type-I matrix systems have gained growing importance as a cartilage repair device. However, most of the established matrix systems use collagen type-I of bovine origin seeded in high cell densities. Here we present a novel collagen type-I gel system made of rat tail collagen for the cultivation of human chondrocytes in low cell densities. Rat tail collagen type-I gel (CaReS, Arthro Kinetics, Esslingen, Germany) was seeded with human passage 2 chondrocytes in different cell densities to evaluate the optimal cell number. In vitro, the proliferation factor of low density cultures was more than threefold higher compared with high density cultures. After 6 weeks of in vitro cultivation, freshly prepared chondrocytes with an initial cell density of 2x10(5) cells/mL showed a proliferation factor of 33. A cell density of 2x10(5) cells/mL was chosen for in vitro and in vivo cultivation using the common nude mouse model as an in vivo system. Chondrocytes stayed viable as a Live/Dead fluorescence assay and TUNEL staining revealed. During in vitro cultivation, passage 0 cells partly dedifferentiated morphologically. In vivo, passage 0 cells maintained the chondrocyte phenotype and demonstrated an increased synthesis of collagen type-II protein and gene expression compared to passage 2 cells. Passage 2 cells did not redifferentiate in vivo. Cultivating a cell-seeded collagen gel of bovine origin as a control (AtelocollagenTM, Koken, Tokyo, Japan) did not lead to superior results with regard to cell morphology, col-II protein production and col-II gene expression. With the CaReS collagen gel system the best quality of repair tissue was obtained by seeding freshly isolated chondrocytes.

Computer-assisted single- or double-cut oblique osteotomies for the correction of lower limb deformities.

Corrective osteotomy interventions on lower extremities are widely accepted procedures for restoring axial alignment of lower limbs. However, some studies reveal failure rates of up to 70 per cent in a 10 year time frame, which indicates that the success of corrective osteotomies depends on multiple factors. Based on a comprehensive review of error sources among conventional correction osteotomy interventions, a novel approach was developed in order to reduce these error sources among all clinical working steps (deformity determination, planning, and intra-operative realization). The article describes the implemented methodology for realizing optimal correction osteotomies based on a six-dimensional or 12-dimensional optimization module for single- and double-cut oblique osteotomies. The results show that the realized planning and navigation concept enables reduction in the error sources among the clinical working steps of correction osteotomy interventions.

In vivo cultivation of human articular chondrocytes in a nude mouse-based contained defect organ culture model.

The nude mouse model is an established method to cultivate and investigate tissue engineered cartilage analogues under in vivo conditions. One limitation of this common approach is the lack of appropriate surrounding articular tissues. Thus the bonding capacity of cartilage repair tissue cannot be evaluated. Widely applied surgical techniques in cartilage repair such as conventional and three-dimensional autologous chondrocyte implantation (ACI) based on a collagen gel matrix cannot be included into nude mouse studies, since their application require a contained defect. The aim of this study is to apply an organ culture defect model for the in vivo cultivation of different cell-matrix-constructs. Cartilage defects were created on osteochondral specimens which had been harvested from 10 human knee joints during total knee replacement. Autologous chondrocytes were isolated from the cartilage samples and cultivated in monolayer until passage 2. On each osteochondral block defects were treated either by conventional ACI or a collagen gel seeded with autologous chondrocytes, including a defect left empty as a control. The samples were implanted into the subcutaneous pouches of nude mice and cultivated for six weeks. After retrieval, the specimens were examined histologically, immunohistochemically and by cell morphology quantification. In both, ACI and collagen gel based defect treatment, a repair tissue was formed, which filled the defect and bonded to the adjacent tissues. The repair tissue was immature with low production of collagen type II. In both groups redifferentiation of chondrocytes remained incomplete. Different appearances of interface zones between the repair tissue and the adjacent cartilage were found. The presented contained defect organ culture model offers the possibility to directly compare different types of clinically applied biologic cartilage repair techniques using human articular tissues in a nude mouse model.

[The injury pattern following the introduction of the junior premier league in Germany compared to professional senior football (soccer)]. / Das Verletzungsmuster nach Einführung der A-Junioren-Fussball-Bundesliga in Deutschland im Vergleich zum Senioren-Profi-Fussball.

In 2003 the junior soccer premier league (U19) has been introduced in Germany to increase the competitive level in this group of age (16 - 18 years). It is the aim of this study to compare the injury pattern accompanying this new league of semi-professional junior soccer with a professional senior team. In a retrospective study all traumatic and overuse injuries, responsible for absence from practice or matches, which occurred in two seasons of one junior premier league team were recorded and analyzed. These data were compared to the injury pattern of a professional senior team based on a one-season survey. Overall, more traumatic than overuse injuries were seen. The lower extremity was predominantly affected by both. The ankle joint was the most injured joint. An injury rate of 2.89 per 1000 hours of soccer was calculated for the juniors and 2.35 for the seniors. Junior players missed 15.8 days and seniors 17.1 days of practice or match as result of an injury. Semi-professional junior and professional senior soccer share the same injury patterns with regard to injury rates and types of injuries. Therefore a professional medical care with special emphasis on prophylaxis is warranted in semi-professional junior soccer.

[Liver laceration following a kick in a soccer game]. / Leberruptur nach einem Fusstritt im Fussballspiel.

Severe intraabdominal injuries in soccer are very rare. We present the case of an 18 year old soccer player who suffered from a grad IV liver laceration following a kick during a soccer game. After primary explorative laparatomy and liver packing in a hospital nearby the patient was transferred to our clinic. Following CT scan the injury was treated by suture of liver parencym lacerations, argon laser coagulation and pile duct repair. In soccer severe intraabdominal injuries should be expected following players collision at high velocity or kicking with the foot or the knee.

Radionuclide imaging of the painful hip arthroplasty: positron-emission tomography versus triple-phase bone scanning.

Two major complications of hip replacement are loosening and infection. Reliable differentiation between these pathological processes is difficult since both may be accompanied by similar symptoms. Our aim was to assess the diagnostic ability of triple-phase bone scanning (TPBS) and positron-emission tomography (PET) to detect and differentiate these complications in patients with a hip arthroplasty. Both TPBS and PET were performed in 63 patients (92 prostheses). The radiotracer for PET imaging was (18)F-fluorodeoxyglucose (FDG). Image interpretation was performed according to qualitative and quantitative criteria although the final diagnosis was based upon either surgical findings or clinical follow-up. The sensitivity, specificity and accuracy of PET was 0.94, 0.95 and 0.95 respectively, compared with 0.68, 0.76 and 0.74 for TPBS. We found that an image interpretation based exclusively upon quantitative criteria was inappropriate because of its low selectivity. The histological examination indicated that increased periprosthetic uptake of FDG in patients with aseptic loosening was caused by wear-induced polyethylene particles and the subsequent growth of aggressive granulomatous tissue.

[Risk of injury in and adolescent and junior competitive karate]. / Das Verletzungsrisiko im Jugend- und Juniorenwettkampfkarate.

Increasing professionalism in competitive karate has led to a specific injury pattern. The aim of our study was to investigate the injury pattern in junior competitive karate and to evaluate the prophylactic effect of fist padding. During the 4 (th) Junior World Championships of the World Karate Confederation (WKC) 2004 235 karate fights were observed and injury-related data were recorded. Fist padding was used in 183 fights, 52 fights were carried out without. In 22 % of all fights we saw an injury. Most of them were mild injuries of the head and face: 32 bruises of the face (13 with epistaxis), 7 facial lacerations and 3 concussions (mild brain injury). 14 fights were stopped due to an injury. Only in the category male 18 - 20 years a higher rate of injuries was seen without fist padding (shobu ippon) compared to shobu sanbon (with fist padding). The injury pattern of junior competitive karate is comparable to senior karate. Fist padding does not generally reduce the incidence or severity of injuries.

[Analysis of (18)F-FDG uptake patterns in PET for diagnosis of septic and aseptic loosening after total hip arthroplasty]. / Analyses des (18)F-FDG Speichermusters in der PET zur Diagnostik von septischer und aseptischer Lockerung bei Totalendoprothesen des Hüftgelenks.

AIM: Identification of typical patterns for fluorodeoxy-glucose (FDG) uptake in positron emission tomography (PET) to detect aseptic loosening of hip prosthesis (ace-tabular and/or femoral component) and prosthetic infection. METHODS: 18 patients with painful hip prosthesis underwent PET using a dedicated full ring scanner after application of 200-300 MBq FDG. The interface between bone and surrounding soft tissue or bone as displayed on coronal slices was divided into 12 segments in accordance with the classifications of Delee and Gruen. FDG uptake in each of the segments was scored (0-3) by two independent observers. Intraoperative findings were regarded as the gold standard. RESULTS: After surgical revision 14 acetabular components and 9 femoral components were found to be loose and prosthetic infection was present in 7 prostheses. Loosening of the acetabular component was correlated to enhanced uptake in the middle of the acetabular interface, while loosening of the femoral component was correlated to enhanced uptake in the proximal and middle segment of the lateral femoral interface and the proximal segment of the medial femoral interface. A similar pattern was found in prosthetic infection with high uptake along the middle portion of the lateral femoral interface. In 6 of 7 infected prostheses loosening of the acetabular and of the femoral component was present. Taking the typical uptake patterns as criteria for loosening and grade 3 uptake as an additional criterion for septic loosening the accuracy of PET imaging in the detection of loosening of the acetabular or the femoral component and of prosthetic infection was 72, 78 and 89%, respectively. CONCLUSION: This pilot study presents FDG-PET as a promising diagnostic tool for patients with painful hip prostheses. Its clinical value should be evaluated in a larger patient population.

[Pancreatoblastoma: a rare malignant neoplasm in early adulthood]. / Das Pankreatoblastom: Eine seltene maligne Neoplasie im jüngeren Erwachsenenalter.

INTRODUCTION: Here we report the ninth case of pancreatoblastoma in an adult. PATIENT AND METHOD: At the time of diagnosis the female patient was 22 years old. She had a tumor in the left upper abdomen, measuring 9 cm in diameter. Preoperatively the diagnosis of a pancreatoblastoma was suspected and an explorative laparotomy was performed followed by radical tumor extirpation and intraoperative radiotherapy. After the diagnosis of a pancreatoblastoma was confirmed by definitive histopathological examination, combined Radiochemotherapy was performed. DISCUSSION: Special features in histomorphological characterization of the tumor and problems concerning diagnosis and differential diagnosis as well as the lack of a definitive therapy regime are discussed.

[Abdominal compartment syndrome: prevention and treatment]. / Abdominelles Kompartmentsyndrom: Vermeidung und Behandlung.

UNLABELLED: Abdominal compartment syndrome is defined by increased intraabdominal pressure above 20 mmHg with increased pulmonary peak pressure and oliguria. In primary abdominal compartment syndrome the increased intraabdominal pressure is caused directly by peritonitis, ileus or abdominal and pelvic trauma. Secondary compartment syndrome is a result of forced closure of the abdominal wall after abdominal surgery. The effects are decreased cardiac output, pulmonary atelectasis, oliguria to anuria and hepatic as well as intestinal reduction of perfusion. Effective monitoring is done by standardised measuring of urinary bladder pressure. Normal values are between 0 and 7 cm H2O, after elective laparotomies 5-12 cm H(2)0. Above 25 cm H(2)0 they are definitely pathological. For the prevention and therapy of manifested abdominal compartment syndrome the application of a laparostomy using a resorbable mesh is recommended. Between 1988 and 1999 we applied a laparostomy to lower the intraabdominal pressure in 377 patients. In 16% of the cases it was indicated by primary abdominal compartment syndrome with a bladder pressure of 31 +/- 4 cm H(2)0 preoperatively, which could be lowered to 17 +/- 4 cm H(2)0 by laparostomy. An early reconstruction of the abdominal wall could be performed in 18% of the cases. CONCLUSIONS: The abdominal compartment syndrome is an often underestimated problem in abdominal surgery involving multiple organ systems. The temporary laparostomy lowering intraabdominal pressure rather than a forced closure of the abdominal wall should be used in all circumstances.

[Competitive karate and the risk of HIV infection--review, risk analysis and risk minimizing strategies]. / Wettkampfkarate und die Gefahr einer HIV-Infektion--Ubersicht, Risikoanalyse und Strategien zur Risikominimierung.

Bleeding facial injuries are not uncommon in competitive karate. Nevertheless, the risk of an infection with HIV is extremely low. Guidelines about the prevention of HIV infections are presented. Especially in contact sports and martial arts the athletes, judges and staff have to recognize and employ these recommendations. Bleeding wounds of the hands due to contact with the opponents teeth can be minimized by fist padding.

[Metaphyseal fitting short-stem prosthesis - preliminary results of a prospective single-surgeon series]. / Metaphysär verankernde, zementfreie Kurzschaftprothese - klinisch-radiologische Ergebnisse einer prospektiven Single-Surgeon-Studie.

BACKGROUND: Conventional uncemented femoral stems provide good long-term fixation in patients with a wide range of clinical function. However, preservation of bone stock, and minimally invasive approaches have led to exploration into various other implant designs. Short-stem prosthesis focusing on a stable metaphyseal fit have emerged to address these challenges in total hip arthroplasty. The purpose of this study was to evaluate the clinical and radiological results of a newly developed short-stem hip prosthesis AIDA® in context of a single surgeon study. MATERIAL AND METHODS: From February 2009 to December 2013, 72 cementless "AIDA® short stems" (Fa. Implantcast) were implanted by a single surgeon in one study centre via the Watson Jones interval. All patients signed informed consent prior to screening and the study design was approved by the local ethics committee. 51 patients with 52 implants (35 female, 36 male) with a follow-up > 24 months were included in this prospective, controlled clinical trial. The patients were pre- and postoperatively examined clinically and radiological by a specified protocol. RESULTS: The average patient age at the time of THA was 61 ± 3.2 years (min.-max. 46-68 years). At the last follow-up, the average Harris Hip score increased from 41.4 ± 4.5 preoperatively to 96.8 ± 3.2 points postoperatively. The hospital stay was 9.1 days on average. The X-rays showed in all cases a stable fixation of the stems with full bony integration and no signs of loosening or migration. There were no specific complications relating to the less invasive approach. Postoperatively one periprosthetic fracture was evident. The revision operation into a cementless stem was done without any complications (revisions rate 1.9 %). CONCLUSION: The newly developed "AIDA short stem" is a promising hip implant for the young and active patient with osteoarthritis of the hip. The short-term results are encouraging, but nevertheless mid- and long-term results must be further observed on a prospective basis as part of this collective study.

[Perioperative management in outpatient arthroscopy of the knee joint]. / Perioperatives Management in der ambulanten arthroskopischen Chirurgie des Kniegelenks.

AIM: Nowadays, complex arthroscopic procedures of the knee joint, such as ACL reconstruction, are routinely carried out on an outpatient basis. The reduced time spent with the patient places high demands on the surgeon with regard to the management of such cases. The aim of this study was to evaluate the current standards of perioperative management following outpatient arthroscopic surgery of the knee in Germany. METHODS: A questionnaire consisting of 18 questions was sent to 215 members of the German Association of Outpatient Arthroscopy (BVASK e. V.), dealing with the following topics: antibiotic prophylaxis, DVT prophylaxis, use of a tourniquet and suction drain, physical therapy, physiotherapy, analgesia, anaesthesia and emergency management. More than 51% of the forms were returned and considered suitable for statistical analysis. RESULTS: A total of 62% of the surgeons reported the use of an antibiotic prophylaxis (i. v. single shot) in every arthroscopic case, while 19% administer antibiotics only occasionally, especially in ACL reconstruction. Postoperative antibiotic treatment was reserved for special situations, such as prior joint infection. Prophylaxis of DVT by means of low molecular weight heparin was carried out in 96% of the cases. 51% prescribed anticoagulant agents for 1 week, 39% for the duration of reduced weight bearing. Half of the surgeons used a tourniquet cuff, 22% exsanguinate the limb prior to cuff inflation. A suction drainage was applied by 36% of the surgeons regularly and by 45% occasionally. The drain is left for one day by 79% of the surgeons, while 11% reported a shortened use of only several hours. With regard to analgesia, 66% of all surgeons apply some kind of local anaesthetic into the knee joint post surgery. Systemic preoperative analgesics or anti-inflammatory agents are given regularly in 56 % of the cases. A total of 92% of the procedures are carried out under general anaesthesia. In 36% of the cases, some kind of additional regional peripheral anaesthesia is used. With regard to postoperative care, cryotherapy is considered standard (97%) and 64% of the surgeons recommend physiotherapy. Nearly all surgeons (97%) offer the patients the opportunity to reach them personally via mobile phone during the first night following arthroscopic surgery. CONCLUSIONS: DVT prophylaxis with LMWH, general anaesthesia, postoperative cryotherapy and personal availability by phone can be considered part of the standard perioperative management following outpatient knee arthroscopy in Germany. However, a wide variety of treatment options can be found regarding topics such as analgesia, antibiotic prophylaxis, tourniquet, knee drainage and physiotherapy.

[Periprosthetic bone cement allocation at the femoral durom hip prosthesis. a pilot study: artificial bone models versus ex-vivo femura]. / Periprothetische Zementverteilung bei femoralen Oberflächenersatzprothesen im Vergleich: Kunstknochen versus humaner Ex-vivo-Knochen. Eine Pilotstudie.

INTRODUCTION: Despite controversial discussions, hip resurfacing at the moment seems to be the most bone-sparing surgical procedure of the femoral bone when implanting hip endoprostheses. Main risks are septic and aseptic loosening and necroses of the coxal end of the femoral bone mainly influenced by the periprosthetic allocation of bone cement. Because of a lack of radiation transparency of the hip resurfacing implant, this cement allocation cannot be sufficiently evaluated by common radiological procedures. A pilot study was conducted to describe and validate the macromechanical interdigitation of bone cement with spongy bone of anatomic specimens compared to artificial bone models and to evaluate whether artificial bones may be used for further interdigitation studies of different implantation techniques. METHODS: Plastic models of polyoxymethylene (POM) according to the inside geometry of the Metasul Durom hip prosthesis were implanted on ex vivo femora (n = 14) versus artificial bone models (n = 24) (Sawbones) of three different spongy densities (0.16; 0.20; 0.32 g/cm(3)) (each n = 8) in a clinically standardised surgical procedure and reproduced by highly resolving computed tomography. Afterwards a computer-based analysis of the cement allocation was accomplished. RESULTS: It could be shown that the Sawbones of the lower spongy densities (0.16 and 0.20 g/cm(3)) were similar to the ex vivo femora regarding the bone penetration of cement. No significant differences could be shown regarding interdigitation. According to our data, both groups of Sawbones may be used for further studies.

[Evaluation of the efficiency of the zero-dose-C-arm navigation approach]. / Evaluation der Effizienz des Zero-Dose-C-Arm-Navigations-Ansatzes.

BACKGROUND: The efficiency and success of computer-assisted fluoroscopic navigation systems mainly depend on the quality of the process of image acquisition: obtaining the correct view of anatomic structures, relative orientation of multiplanar X-ray images and the necessary amount of radiation dose. These systems may be optimised by using a system called zero-dose c-arm navigation (ZDCAN). We investigate whether the available computer-assisted systems may be used to navigate the c-arm before image acquisition to obtain X-ray images with maximised accuracy and minimal radiation exposure. METHODS: Based on position data of an optical tracking system combined with statistical deformable bone models, ZDCAN is able to generate a real-time preview of expected X-ray images of the lower extremities without using radiation. We performed a cadaver study on six full-body specimens comparing the zero-dose approach to conventional positioning of the c-arm in order to evaluate efficiency and accuracy. Eight users acquired two perpendicular X-ray images of the hip, the knee and the femoral diaphysis. RESULTS: The number of X-ray images required to get a satisfying picture could be reduced to seven using the zero-dose approach; the conventional approach needed 11 images. The mean time did not differ significantly. Regarding the image quality, using ZDCAN quasi-orthogonality could be reached while the conventional approach showed a large variation of the relative orientation. CONCLUSION: Using ZDCAN, the amount of radiation can be reduced by requiring less X-ray images as well as reaching better accuracy.