[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.

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.

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.

[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 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.

[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.

[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.

[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.

[Silicate coating of cemented titanium-based shafts in hip prosthetics reduces high aseptic loosening]. / Silikatbeschichtung zementierter Titanschäfte für die Reduzierung aseptischer Lockerungsraten.

AIM: For cemented hip prostheses, all requirements can be fulfilled by using forged Co/Cr/Mo stems. Co/Cr/Mo alloys, however, are contraindicated for allergy sufferers. For these patients, a cemented prosthesis made of titanium (alloy) would be indicated. Cemented stems from titanium (alloy), depending on the geometry of the prosthesis and its specific surface texture, however, may have loosening rates which are clinically not tolerable. In comparison to Co/Cr/Mo alloys, the greater roughness in conjunction with lesser abrasion resistance of titanium-based alloys leads to high loosening rates caused by abrasion. On the other hand, the greater surface roughness permits good mechanical retention of bone cement to the surface. Good mechanical retention enhances migration behaviour and reduces micromotions. However, there is no stable hydrolytic bond between bone cement and metallic surface; intermediate-term debonding between metal and bone cement is predictable. This debonding results in relative movements, consequently in wear particles which have their origin both from the rough metallic surface and from the PMMA cement. The roughness of the metallic surface operates as emery and with that, a rubbing wear from the PMMA. METHOD: For the above reasons, a low or moderate roughness is essential for easily abradable implants such as shafts made of titanium (alloy) because low roughness provides a fail-safe running function in case of debonding. Thus, one must allow for inappropriate migration behaviour accompanied by greater micromotions due to insufficient mechanical retention in the case of low roughness. This can be accomplished by a silicate layer coating applied to the metal shaft surface via electrochemical "ECD" or physical vapour deposition "PVD". For analysis, specimens (screws for pull-out, cones for push-out tests) were sand-blasted, so that roughnesses between Ra = 0.8 microm (Rz = 4 microm) and Ra = 2.0 microm (Rz = 9 microm) were generated. RESULTS: The bond strengths observed in tensile tests for roughnesses of Ra = 1.7 mm were always well above 25 MPa for all periods of hydrolytic load. Therefore, the investigation shows that surfaces of moderate roughness (Ra = 1.7 microm), however coated, provide a steady retention. Cave-in and micromotions should widely be prevented. CONCLUSION: The abrasion, which is a consequence of and reason for debonding and loosening at the same time, should be avoidable if the bonding of cement on the metallic shaft is stabilised with the help of a suitable chemical bond system.

[Perineural cysts causing severe back pain and pathological fracture of the massa lateralis of the sacrum]. / Perineurale sakrale Zysten als Ursache von Ischialgie und pathologischer Massa-lateralis-Fraktur des Os sacrum.

We report on the case of an 81-year-old woman who was hospitalised because of severe pain at the sacro-iliacal joint radiating into the left leg without any accompanying neurological defect. X-rays demonstrated a step in the left massa lateralis of the sacrum, thus CT scans and MRI were performed, and multiple perineural cysts (Tarlov's cysts) were found. The patient underwent microsurgical treatment by fenestration of the cyst wall and evacuation of the fluid content in order to avoid further expansion of the cysts. Under consequent treatment with pain killers, complete mobilisation of the patient could be achieved. Ambulant follow-up by clinical controls and X-rays demonstrated a substantial resolution of the patient's preoperative symptoms. Symptomatic perineural cysts should be included into differential diagnosis of severe low back pain, thus CT or MRI scans should be performed in case of long-lasting or intrackable pain.

[Intravertebral pressure during vertebroplasty - an in-vitro study]. / Intravertebrale Druckentwicklung bei der Vertebroplastie - Eine anatomische In-vitro-Untersuchung.

INTRODUCTION: Extravasation of bone cement into the vertebral venous system during cement injection has been reported to be a major complication of percutaneous vertebroplasty. Therefore, high injection pressures during cement application into the fractured vertebral body are considered as one possible cause of cement leakage or extravasation. The aim of the current study was to measure the increase in intravertebral pressure caused by cement injection during vertebroplasty compared to the baseline venous pressure for the ascending lumbar vene. MATERIAL AND METHODS: In context of a cadaver study of 19 unfixed lumbar cadaver spines (L2-L5) [9 female, 10 male, 72 +/- 4.1 years] 19 vertebroplasties have been performed under operative conditions through a transpedicular approach. A manometer was placed in the lateral corticalis of each vertebral body for dynamic pressure measurement during 4 cement application cycles. Average and maximal intravertebral pressures as well as the average intravertebral pressure over the time of cement application ["area under the curve" (AUC)] were calculated. RESULTS: Average intravertebral pressure (10.9 +/- 12.6 kPa [min.: - 15.2 +/- 24.7 kPa; max.: 56.1 +/- 70.1 kPa]) showed a 13.6-fold increase compared to the baseline venous pressure for the ascending lumbar vein and a 70-fold increase compared to maximal pressure. During the 4 cement application cycles a continuous increase of the average intravertebral pressure over the application cycle (AUC) occurred. CONCLUSION: The 13.6-fold increase in intravertebral body pressure caused by cement injection during percutaneous vertebroplasty in comparison to the baseline venous pressure for the ascending lumbar vein might be one possible cause of the high rate of extravasation of bone cement reported in the current literature.

[Optical coherence tomography (OCT) to evaluate cartilage tissue engineering]. / Die optische Kohärenztomografie (OCT) zur Darstellung der Regenerateigenschaften im Tissue Engineering von Knorpelgewebe.

AIM: The aim of this study was to investigate hyaline cartilage defects treated with cell-seeded artificial matrix systems (two different collagen type I gels) with the method of optical coherence tomography (OCT) and to correlate the results with conventional histological and immunocytochemical staining. METHOD: Osteochondral blocks were harvested from 20 patients undergoing total knee replacement and trimmed to 2 x 2 cm. Under sterile conditions, chondral defects of 8 mm diameter were either filled with a collagen type I gel plug seeded with autologous chondrocytes (2 x 10 (5)/mL gel), or with a corresponding gel plug which was stabilised by a 20-fold compression. Of each group, 5 specimens were cultivated for 6 weeks under standardised in vitro conditions (37 degrees C, 5 % CO (2), humidified atmosphere), while the remaining 5 specimens were implanted subcutaneously in nude mice (BALBc -/-). Immediately after recovery, the repair tissue and bonding zones were investigated by OCT. Subsequently, specimens were decalcified and investigated by H&E staining and collagen type II immunostaining. The results of OCT and conventional staining were correlated. RESULTS: By OCT, repair tissue could be investigated up to 1.6 mm in depth, physically limited by the utilised OCT system. In the denser hyaline cartilage regions, OCT resolution was reduced. Regardless of cultivation (in vitro or nude mouse), ultrastructural features of the repair tissue could be demonstrated. In particular, ultrastructural differences between the two investigated collagen gels could be detected. Moreover, the bonding region between repair tissue and hyaline cartilage could be evaluated by OCT investigation. The results of the OCT measurements were confirmed by H&E and collagen type II immunostaining. CONCLUSION: By OCT, repair tissue generated by the treatment of cartilage defects with tissue-engineered matrix systems could be evaluated in vitro. Future studies may show if repair tissue quality may be monitored in situ by OCT.

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.

[Functionality and accuracy of a fluoroscopic navigation system in the placement of the femoral component for hip resurfacing - a cadaver study]. / Funktionalität und Genauigkeit eines fluoroskopischen Navigationssystems zur Implantation von Hüftkopf-Oberflächenersatzprothesen: Eine Anatomiestudie.

INTRODUCTION: Resurfacing arthroplasty represents an alternative method to total hip replacement especially for the young and active patient. The main reasons for early implant failure are mal-positioning of the femoral component and notching of the femoral neck during femoral head preparation. MATERIAL AND METHODS: In the context of a cadaver study of formalin-fixed cadaveric full body specimens 6 DUROM -Hip-Resurfacing prosthesis have been implanted under navigation control. The aim of the study was an evaluation of the functionality and accuracy of the computer-assisted planning and navigation system on the basis of a navigation module library from Surgitaix AG Aachen, Germany. RESULTS: The main angulation error between planning (135.2 +/- 3.6 degrees ) and navigation (136.2 +/- 2.8 degrees ) was 1.9 +/- 1.1 degrees , the main anterior offset error between planning (2.2 +/- 1.3 mm) and navigation (2.7 +/- 2.3 mm) was 1.2 +/- 1.9 mm. The main distance error between planning and navigation was 2.7 +/- 1.3 mm. The mean time for all five planning and navigation steps was 20.2 +/- 2.5 min. Against the background of a acetabular bone-saving approach in all 6 cases the smallest possible femoral component could be implanted. CONCLUSION: The computer-assisted fluoroscopic planning and navigation system for hip resurfacing showed within the scope of this cadaver study first promising results. The system approaches a practicable intraoperative planning with a high accuracy in operative implementation. Nevertheless, the potential benefit has to be evaluated in further clinical studies, especially from the perspective of a possible integration of this navigation system into the clinical work-flow. Further studies should consider a fluoroscopic-assisted range of motion assessment under consideration of an additional cup-module to enhance the postoperative range of motion after hip resurfacing procedures.

[Clinical results after three years use of matrix-associated ACT for the treatment of osteochondral defects of the knee]. / Klinische Drei-Jahres-Ergebnisse der matrixgekoppelten ACT zur Behandlung osteochondraler Defekte am Kniegelenk.

AIM: The aim of this study was to examine the clinical results after the treatment of osteochondral defects of the knee with autologous bone grafting and matrix-supported autologous chondrocyte transplantation (ACT). METHOD: In this study 13 patients with osteochondral defects of the knee (12 femoral, 1 tibial) with OCD ICRS grade IV or ICRS grade IV B were included. The osteochondral defects were reconstructed simultaneously with autologous monocortical cancellous bone cylinders or chips from cancellous bone and matrix-supported autologous chondrocyte transplantation (CaReS). Data were analysed in accordance with the ICRS criteria and the Brittberg score. Patients were followed up to 36 months after the operation. RESULTS: The average age of the patients was 34.9 (16 - 47) years at the time of surgery. The size of the defect was 8.1 (3.8 - 13.5) cm(2). The subjective and objective IKDC scores, the Brittberg and the ICRS function score were statistically significantly improved during the observation time. In one patient the transplantation failed and another patient was not available for the follow-up at 36 months. The objective IKDC score and the ICRS function score increased from 0/13 (0 %) to 11/12 (91.7 %) in categories A and B, or I and II, respectively, after 3 years. At this point of time 83.4 % (10/12) of the patients voted the treatment as excellent or good. The subjective IKDC score improved from 38.4 (+/- 12.7) preoperatively to 66.1 (+/- 17.0) after 3 years. CONCLUSION: The treatment of osteochondral defects of the knee with autologous bone grafting and matrix-supported autologous chondrocyte transplantation shows promising results even for larger defects. But for a final decision about this therapy the present sample size was too small. There is a need for further long-term investigation with a larger number of patients.

[Mechanical bending strength of explanted ex vivo bone cements compared with in vitro samples]. / Mechanische Biegefestigkeiten von explantierten Ex-vivo-Knochenzementen verglichen mit In-vitro-Proben.

INTRODUCTION: The mechanical properties of acrylic bone cements are an important factor in determining an efficient load transmission between prosthesis and bone to guarantee the long-term stability in cemented hip arthroplasty. MATERIAL AND METHODS: Palacos and Refobacin Palacos specimens from 21 aseptically loosened femoral compoments of cemented hip arthroplasties manufactured by the first to third generation cementing technique have been mechanically tested in a standardised four-point bending test (ISO 5833). In vitro manufactured Palacos and Refobacin Palacos specimens served as a control group. The fatigue fracture surfaces were morphologically analysed with light microscopy. RESULTS: Under in vitro conditions manufactured specimens had higher values of bending strength, with the exception of blood contaminated ones, compared to ex vivo specimens. Ex vivo specimens of the second and third generation cementing technique had higher values than specimens of the first generation. CONCLUSIONS: Acrylic bone cements are subjected to a multifactorial material fatigue in vivo. Here, the art and quality of cementing technique is of eminent importance in determining the long-term stability of cemented hip arthroplasty.

[Surface pretreatment of endoprostheses by silica/silane to optimise the hydrolytic stability between bone cement and metal. Total hip and knee arthroplasty]. / Silikatisierte/silanisierte Implantatoberflächen zur optimierten hydrolysestabilen Verbundfestigkeit zwischen Knochenzement und Metall. Zementierte Hüft- und Knieendoprothetik.

BACKGROUND: The aseptic loosening of cemented total hip and knee arthroplasties is still an unsolved problem. In this regard, the hydrolytic resistance in the metal-to-bone cement interface is of major importance. METHODS: Cemented pretreated femur stems and tibia components coated by means of a silica/silane interlayer system were dynamically loaded with the help of a hip and knee simulator similar to DIN ISO Norm. After loading, the components were microscopically analysed concerning both debonding in the metal-to-bone cement interface and cement mantle defects. These data were matched with uncoated components. Unloaded coated and uncoated femur and tibia components acted as controls. RESULTS: Compared with uncoated components, the pretreated and coated ones yielded a significant reduction in cement defects as well as of debonding in the metal-to-bone cement interface. CONCLUSION: Using the silica/silane interlayer system for cemented femur and tibia components, hydrolytic debonding in the metal-to-bone cement interface with following cement mantle failure can be reduced. This could help increase the long-term stability of the metal-to-bone cement compound, with decreased aseptic loosening.

Surface coating to improve the metal-cement bonding in cemented femur stems.

INTRODUCTION: Hydrolytic debonding of the metal-cement interface is one of the main reasons for aseptic loosening in cemented hip arthroplasty. MATERIALS AND METHODS: BiContact femur stems (CoCrMo-/TiAl6V4-alloy) were coated by a silica/silane interlayer coating system. The stems were cemented into artificial femurs. The cyclical loading (DIN ISO 7206-4) was performed within a hip-simulator. Uncoated stems (CoCrMo-/TiAl6V4-alloy) were prepared and loaded the same way. After loading, the metal-cement and the bone-cement interfaces were analysed. Unloaded uncoated and unloaded coated BiContact stems served as a control. RESULTS: The coated loaded stems showed a significant reduction in debonding and cement failure (P < or = 0.05). A high correlation was documented between debonding and cement failure (rSpear> or = 0.9). There was no significant difference between CoCrMo- and TiAl6V4-stems (P > or = 0.05). CONCLUSION: The silica/silane coating significantly decreased hydrolytic debonding at the metal-bone cement interface with consecutively less cement failure.

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.