Annelie-Martina Weinberg

Bone-implant interface strength and osseointegration: Biodegradable magnesium alloy versus standard titanium control.

Previous research on the feasibility of using biodegradable magnesium alloys for bone implant applications mainly focused on biocompatibility and corrosion resistance. However, successful clinical employment of endosseous implants is largely dependent on biological fixation and anchorage in host bone to withstand functional loading. In the present study, we therefore aimed to investigate whether bone-implant interface strength and osseointegration of a novel biodegradable magnesium alloy (Mg-Y-Nd-HRE, based on WE43) is comparable to that of a titanium control (Ti-6Al-7Nb) currently in clinical use. Biomechanical push-out testing, microfocus computed tomography and scanning electron microscopy were performed in 72 Sprague-Dawley rats 4, 12 and 24 weeks after implantation to address this question. Additionally, blood smears were obtained from each rat at sacrifice to detect potential systemic inflammatory reactions. Push-out testing revealed highly significantly greater maximum push-out force, ultimate shear strength and energy absorption to failure in magnesium alloy rods than in titanium controls after each implantation period. Microfocus computed tomography showed significantly higher bone-implant contact and bone volume per tissue volume in magnesium alloy implants as well. Direct bone-implant contact was verified by histological examination. In addition, no systemic inflammatory reactions were observed in any of the animals. We conclude that the tested biodegradable implant is superior to the titanium control with respect to both bone-implant interface strength and osseointegration. These results suggest that the investigated biodegradable magnesium alloy not only achieves enhanced bone response but also excellent interfacial strength and thus fulfils two critical requirements for bone implant applications.

Aquaporin 1 (AQP1) expression in experimentally induced osteoarthritic knee menisci: An in vivo and in vitro study

Osteoarthritis (OA) of the knee is a major problem in our society. The development of new treatment options for OA is limited, because the pathophysiological mechanisms are not clearly understood, especially on the molecular level. Aquaporin 1 (AQP1) is a specific protein channels for water transport; it is expressed in articular chondrocytes, human synovitis, in chondrocytes of patients with rheumatoid arthritis or OA and in chondrocyte-like cells of human intervertebral disc. The aim of this study was to investigate the expression of AQP1, through immunohistochemistry, immunocytochemistry and Western blot, in experimentally induced OA knee menisci. AQP1 was studied in vivo in knee OA menisci from 36 rats that underwent medial or lateral meniscectomy, and in vitro on fibrochondrocytes derived from knee OA menisci rats. OA in rats was experimentally induced and tested by histomorphometric analysis. Histological results demonstrated structural alterations in OA menisci accompanied by a very strong AQP1 immunohistochemical and immunocytochemical staining. The Western blot analysis confirmed a strong expression of AQP1 in OA fibrochondrocytes cells. The results of the present research suggest that an activation of AQP1, induced by the OA process, may represent an endogenous mechanism, which can be used to control the tissue degeneration within OA articular joints.

Nonoperative treatment of tibial spine fractures in children-38 patients with a minimum follow-up of 1 year.

Objectives: The aim of this study was to determine if nonoperative treatment of fractures of the tibial spine (intercondylar eminence) in pediatric patients is the treatment of choice for these injuries. Design/Setting: Retrospective clinical analysis in a single department. Patients: All patients younger than 17 years presenting with a fracture of the intercondylar eminence between January 1, 1995 and December 31, 2004 were included in this retrospective study. Patients with ossification of the growth plate (physis) at the time of accident were excluded by protocol. Intervention: Nonoperative treatment with knee aspiration, reduction, and immobilization in a long leg cast. Main Outcome Measurements: History-taking and follow-up examinations were performed using the Cincinnati Knee Score and International Knee Documentation Committee Guidelines of 2000. In addition, a magnetic resonance imaging scan of the injured knee was offered to all patients. SPSS 12.0 and Microsoft Excel 2000 were used for data processing and statistical analysis. Results: Forty-three patients have been included in the study. Twenty-three were female and 20 male. The mean age at trauma was 11.5 years (6-16 years). Only 1 patient required a change of therapy and needed open reduction. Thirty-eight patients were available for follow-up at an interval of 1-7.5 years after trauma (mean 3.5 years). None of the patients reported pain, swelling, disability or giving-way, or was handicapped in their daily life. Of 26 magnetic resonance imaging examinations, we found a missing anterior cruciate ligament in 1 and a partial rupture in another patient. Conclusion: Based on our results, nonoperative management can still be recommended as the primary treatment for tibial spine fractures in children.

The influence of ultrasound guidance in the rate of success of acromioclavicular joint injection: an experimental study on human cadavers

BACKGROUND Injections of the acromioclavicular joint (ACJ) are performed routinely in patients with ACJ arthritis, both diagnostically and therapeutically. The aim of this prospective controlled study was to estimate the frequency of successful intra-articular ACJ injections with the aid of sonographic guidance versus non-guided ACJ injections. MATERIALS AND METHODS A total of 80 cadaveric ACJs were injected with a solution containing methylene blue and subsequently dissected to distinguish intra- from peri-articular injections. In 40 cases the joint was punctured with sonographic guidance, whereas 40 joints were injected in the control group without the aid of ultrasound. RESULTS The rate of successful intra-articular ACJ injection was 90% (36 of 40) in the guided group and 70% (28 of 40) in the non-guided group. Ultrasound was significantly more accurate for correct intra-articular needle placement (P = .025). DISCUSSION The use of ultrasound significantly improves the accuracy of ACJ injection.

Intra-articular injection of the acromioclavicular joint

Intra-articular punctures and injections are performed routinely on patients with injuries to and chronic diseases of joints, to release an effusion or haemarthrosis, or to inject drugs. The purpose of this study was to investigate the accuracy of placement of the needle during this procedure. A total of 76 cadaver acromioclavicular joints were injected with a solution containing methyl blue and subsequently dissected to distinguish intra- from peri-articular injection. In order to assess the importance of experience in achieving accurate placement, half of the injections were performed by an inexperienced resident and half by a skilled specialist. The specialist injected a further 20 cadaver acromioclavicular joints with the aid of an image intensifier. The overall frequency of peri-articular injection was much higher than expected at 43% (33 of 76) overall, with 42% (16 of 38) by the specialist and 45% (17 of 38) by the resident. The specialist entered the joint in all 20 cases when using the image intensifier. Correct positioning of the needle in the joint should be facilitated by fluoroscopy, thereby guaranteeing an intra-articular injection.

Reference ranges for neuroprotein S-100B: from infants to adolescents

Abstract Background: Diagnosis and treatment of mild traumatic brain injuries in children are especially problematic. At present, computed tomography (CT) is the standard method to identify if patients with intracranial lesions require inpatient monitoring. CT, however, involves exposure to high doses of X-rays, which should be avoided if possible. In adults, the serum level of neuroprotein S-100B has already been proven to be effective for the selection of patients requiring CT. The aim of the present study was to determine reference ranges for serum S-100B in a large number of healthy children. Methods: All patients younger than 18 years with no recent history of head injuries presenting for routine operations were included in the study. Results: A total of 394 patients were evaluated. In children from 3 to 18 years an upper reference level of 0.16 μg/L was determined. There was a strong inverse relation between age and S-100B in patients younger than 3 years. As the values in this age group were scattered and the number of cases limited (n=65), no reference range could be calculated. Conclusions: This study provides S-100B reference ranges for pediatric patients based on the largest group of healthy pediatric patients yet analyzed. Clin Chem Lab Med 2008;46:1296–9.

Does the anteromedial or anterolateral approach alter the rate of joint puncture in injection of the ankle?: A CADAVER STUDY

Injection or aspiration of the ankle may be performed through either an anteromedial or an anterolateral approach for diagnostic or therapeutic reasons. We evaluated the success of an intra-articular puncture in relation to its site in 76 ankles from 38 cadavers. Two orthopaedic surgical trainees each injected methylene blue dye into 18 of 38 ankles through an anterolateral approach and into 20 of 38 through an anteromedial. An arthrotomy was then performed to confirm the placement of the dye within the joint. Of the anteromedial injections 31 of 40 (77.5%, 95% confidence interval (CI) 64.6 to 90.4) were successful as were 31 of 36 (86.1%, 95% CI 74.8 to 97.4) anterolateral injections. In total 62 of 76 (81.6%, 95% CI 72.9 to 90.3) of the injections were intra-articular with a trend towards greater accuracy with the anterolateral approach, but this difference was not statistically significant (p = 0.25). In the case of trainee A, 16 of 20 anteromedial injections and 14 of 18 anterolateral punctures were intra-articular. Trainee B made successful intra-articular punctures in 15 of 20 anteromedial and 17 of 18 anterolateral approaches. There was no significant difference between them (p = 0.5 and p = 0.16 for the anteromedial and anterolateral approaches, respectively). These results were similar to those of other reported studies. Unintended peri-articular injection can cause complications and an unsuccessful aspiration can delay diagnosis. Placement of the needle may be aided by the use of ultrasonographic scanning or fluoroscopy which may be required in certain instances.

Adhesive strength of bone-implant interfaces and in-vivo degradation of PHB composites for load-bearing applications.

Aim of this study was to evaluate the response of bone to novel biodegradable polymeric composite implants in the femora of growing rats. Longitudinal observation of bone reaction at the implant site (BV/TV) as well as resorption of the implanted pins were monitored using in vivo micro-focus computed tomography (µCT). After 12, 24 and 36 weeks femora containing the implants were explanted, scanned with high resolution ex vivo µCT, and the surface roughness of the implants was measured to conclude on the ingrowth capability for bone tissue. Scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX) were used to observe changes on the surface of Polyhydroxybutyrate (PHB) during degradation and cell ingrowth. Four different composites with zirconium dioxide (ZrO2) and Herafill(®) were compared. After 36 weeks in vivo, none of the implants did show significant degradation. The PHB composite with ZrO2 and a high percentage (30%) of Herafill® as well as the Mg-alloy WZ21 showed the highest values of bone accumulation (increased BV/TV) around the implant. The lowest value was measured in PHB with 3% ZrO2 containing no Herafill®. Roughness measurements as well as EDX and SEM imaging could not reveal any changes on the PHB composites׳ surfaces. Biomechanical parameters, such as the adhesion strength between bone and implant were determined by measuring the shear strength as well as push-out energy of the bone-implant interface. The results showed that improvement of these mechanical properties of the studied PHBs P3Z, P3Z10H and P3Z30H is necessary in order to obtain appropriate load-bearing material. The moduli of elasticity, tensile strength and strain properties of the PHB composites are close to that of bone and thus promising. Compared to clinically used PLGA, PGA and PLA materials, their additional benefit is an unchanged local pH value during degradation, which makes them well tolerated by cells and immune system. They might be used successfully for personalized 3D printed implants or as coatings of rapidly dissolving implants.

Comparative biomechanical and radiological characterization of osseointegration of a biodegradable magnesium alloy pin and a copolymeric control for osteosynthesis

Magnesium alloys offer great advantages as degradable implant material for pediatric fracture fixation and hold the potential to overcome certain critical shortcomings inherent to currently used degradable (co)polymers. Besides good biocompatibility and appropriate degradation kinetics, sufficient implant anchorage in host bone is critical to prevent implant failure. Bone-implant anchorage of biodegradable magnesium alloys, however, has not yet been related and compared to that of copolymers, their degradable counterparts currently in clinical use. The aim of this study, therefore, was to comparatively assess bone-implant interface strength and the amount of peri-implant bone of a biodegradable magnesium alloy pin (Mg-Y-Nd-HRE) and a self-reinforced copolymeric control (85/15 poly(l-lactic-co-glycolic acid)). To this purpose, push-out testing, microfocus computed tomography (μCT), histological and scanning electron microscopic examination was performed after 4, 12 and 24 weeks of transcortical implantation in 72 rats. Biomechanical testing revealed significantly higher ultimate shear strength for the magnesium alloy pins than for the copolymeric controls at all 3 timepoints (P≤0.001 for all comparisons). As evaluated by μCT, the amount of bone present near the interface and in a wider radius (up to 0.5mm) around it was higher in the magnesium alloy implants at 4 weeks, without significant differences at 12 and 24 weeks. Histological examination confirmed direct bone-to-implant contact for both implant types. In vivo degradation of implants did not induce any noticeable local or systemic inflammation. This data suggests that the investigated degradable magnesium alloy rod exhibits markedly superior bone-implant interface strength and a greater amount of peri-implant bone than a self-reinforced copolymeric control currently in use; thus it fulfills a crucial prerequisite for its successful clinical deployment as an alternative degradable orthopedic implant material. Further studies, however, are warranted to evaluate the long-term degradation behavior and biocompatibility of the investigated degradable magnesium-based alloy.

The risk of iatrogenic injury to the deep peroneal nerve in minimally invasive osteosynthesis of the tibia with the less invasive stabilisation system A CADAVER STUDY

Percutaneous stabilisation of tibial fractures by locking plates has become an accepted form of osteosynthesis. A potential disadvantage of this technique is the risk of damage to the neurovascular bundles in the anterior and peroneal compartments. Our aim in this anatomical study was to examine the relationship of the deep peroneal nerve to a percutaneously-inserted Less Invasive Stabilisation System tibial plate in the lower limbs of 18 cadavers. Screws were inserted through stab incisions. The neurovascular bundle was dissected to reveal its relationship to the plate and screws. In all cases, the deep peroneal nerve was in direct contact with the plate between the 11th and the 13th holes. In ten specimens the nerve crossed superficial to the plate, in six it was interposed between the plate and the bone and in the remaining two specimens it coursed at the edge of the plate. Percutaneous insertion of plates with more than ten holes is not recommended because of the risk of injury to the neurovascular structures. When longer plates are required we suggest distal exposure so that the neurovascular bundle may be displayed and protected.