[Premature wear of total knee arthroplasty in sports shown in a golfer]. / Vorzeitiger Verschleiß von Knieendoprothesen im Sport am Beispiel eines Golfers.

Sport with an endoprosthesis is controversially discussed, whereas golf with a knee endoprosthesis is usually allowed. This case shows that playing golf can lead to severe wear of the prosthesis. The wear pattern of the components of the prosthesis suggests increased rotational loads. A change to a constrained prosthesis was made because of metal-to-metal contact. It is important to inform the patient before surgery about sports with endoprosthesis. Athletic loads are not part of prosthesis testing according to ISO.

[Handling of retrieved implants in orthopedic surgery : Results of a survey within the framework of the EndoCert initiative]. / Bestandsaufnahme zum Umgang mit ausgebauten Implantaten in der orthopädischen Chirurgie : Ergebnisse einer Umfrage im Rahmen der EndoCert-Initiative.

BACKGROUND: Although investigations of retrieved medical implants can provide valuable information about the cause of the revision, there is a lack of information, which could be avoided by consequent failure analyses. In the framework of the EndoCert certification system it is obligatory to record and report incidents. OBJECTIVES: The present work examines how the willingness to report has developed in certified arthroplasty centers and which method of handling retrievals is preferred and actually used. MATERIALS AND METHODS: On the basis of a questionnaire for handling retrievals, all 508 arthroplasty centers that were certified till June 1, 2016, were included (return rate = 97.2%). RESULTS: A total of 93.3% of the centers have established an algorithm for handling of retrievals and 83.0% of the centers prefer to hand out the retrieval to the patient, while only 25.7% wish to store it in the center for research purposes. In the case of a potential incident as the cause of revision, centers prefer to forward the retrieval to damage analysis, whereby the centers act in different ways, depending on the case. An implant fracture is, e.g., considered a reportable event in most cases without temporal limitation. On the other hand, breakage or failure of surgical instruments is considered not to be reported in the case of more than half of the centers. In 2014 and 2015, approximately 71% of EPZs reported no incidents. CONCLUSIONS: According to our survey, many certified arthroplasty centers are sensitized to careful handling of retrievals. The treatment of the explanted components is conducted in different ways. The assessment of whether an incident is to be reported shows large differences. In view of the relatively high number of revision surgeries, the number of reports to the authorities appears to be low.

Investigation of the inverse piezoelectric effect of trabecular bone on a micrometer length scale using synchrotron radiation.

In the present paper we have investigated the impact of electro stimulation on microstructural parameters of the major constituents of bone, hydroxyapatite and collagen. Therapeutic approaches exhibit an improved healing rate under electric fields. However, the underlying mechanism is not fully understood so far. In this context one possible effect which could be responsible is the inverse piezo electric effect at bone structures. Therefore, we have carried out scanning X-ray microdiffraction experiments, i.e. we recorded X-ray diffraction data with micrometer resolution using synchrotron radiation from trabecular bone samples in order to investigate how the bone matrix reacts to an applied electric field. Different samples were investigated, where the orientation of the collagen matrix differed with respect to the applied electric field. Our experiments aimed to determine whether the inverse piezo electric effect could have a significant impact on the improved bone regeneration owing to electrostimulative therapy. Our data suggest that strain is in fact induced in bone by the collagen matrix via the inverse piezo electric effect which occurs in the presence of an adequately oriented electric field. The magnitude of the underlying strain is in a range where bone cells are able to detect it. STATEMENT OF SIGNIFICANCE: In our study we report on the piezoelectric effect in bone which was already discovered and explored on a macro scale in the 1950. Clinical approaches utilize successfully electro stimulation to enhance bone healing but the exact mechanisms taking place are still a matter of debate. We have measured the stress distribution with micron resolution in trabecular bone to determine the piezo electric induced stress. Our results show that the magnitude of the induced stress is big enough to be sensed by cells and therefore, could be a trigger for bone remodeling and growth.

[Reportable incidents with surgical instruments in orthopedic surgery]. / Meldepflichtige Vorkommnisse mit Operationsinstrumenten in der Orthopädischen Chirurgie.

BACKGROUND: Breakage of instruments in orthopedic surgery is rarely reported but the consequences can be serious for both patients and surgeons. The medical device directive classifies instruments, such as drills and saws into risk class 1 with low approval requirements. Also the number of applications of reusable instruments is not currently limited. OBJECTIVES: The aim of this study was determine to what extent instrument failure can lead to reportable incidents and how these incidents should be processed. METHODS: The study involved an evaluation of clinical cases from our institution with a selective literature review and discussion of the medical device directive. RESULTS: The experience in our clinic showed that especially breakage of rasps in total hip and knee replacement surgery is associated with a major time extension of the operational procedure, a wider surgical access opening as well as complicated procedures to recover the fragments from the incident site. In individual cases a fenestration of the bone had to be conducted in order to collect the broken piece of the rasp. In one case a revision hip stem had to be used instead of the planned primary stem in order to bridge the fenestration site. CONCLUSION: Such consequences of instrument failure were considered to be a reportable incident. A thorough documentation as well as incident reporting to the manufacturer and the Federal authorities are required for a sufficient processing and risk assessment of the incident.

[Influence of surgeon experience in total hip arthroplasty. Dependence on operating time and complication risk]. / Einfluss der Erfahrung des Operateurs in der Hüftendoprothetik. Abhängigkeit von Operationsdauer und Komplikationsrisiko.

BACKGROUND: As a consequence of limited personnel and financial resources, the increase in total hip arthroplasties places higher demands on orthopedic surgeons. OBJECTIVES: In order to maintain high quality treatment, the correlation between surgical experience, duration of surgery and risk of complications was examined. MATERIAL AND METHODS: The surgery time and, if applicable, complications (until discharge from hospital) of 1129 total hip arthroplasties over a period of 4 years were evaluated retrospectively. RESULTS: The group of most experienced surgeons needed an average time of 53.2 ± 17.6 min for each implantation, followed by moderately experienced surgeons (74.5 ± 25.5 min) and less experienced surgeons (80.8 ± 21.9 min). Of all included cases, a total of 41 complications until discharge from hospital occurred. The number of complications increased with duration of surgery, whereby the risk of complications was significantly lower for shorter surgery times conducted by the most experienced surgeons as well as moderately experienced surgeons. The complication risk of less experienced surgeons remained constant independent of surgery duration. CONCLUSION: These results underline the recommendations of the German Endocert system, which determine a minimum number of total joint arthroplasties as a quality indicator not only for hospitals but also for individual surgeons.

[Applications of numerical simulation in musculoskeletal research and its impact on orthopedic surgery]. / Einsatzgebiete der numerischen Simulation in der muskuloskelettalen Forschung und ihre Bedeutung für die Orthopädische Chirurgie.

Finite element analyses (FEA) as well as multibody system dynamics (MSD) are the main tools used for numerical simulation in the field of musculoskeletal research. While FEA is utilized for field problems, such as calculation of stress and strain distribution, MSD is applied for solving kinematic analyses, such as calculation of muscle and joint forces. Depending on the focus of investigation, modelling of biological tissue may vary from simple homogeneous behavior to modelling biochemical processes on the microscale and nanoscale. An important milestone in biomechanical research was the analysis of stress shielding, which led to further research on bone remodelling. Various models of implant-bone fixation used for the prediction of micromotion have been published. New possibilities for biomechanical analyses are achieved by consideration of complex muscle forces which are generated by MSD simulation and imported into FEA models as limiting conditions. A numerical model always requires experimental validation. If the results are confirmed experimentally, various advantages of numerical simulation apply and problems can be analysed isolated from many influencing factors. Therefore, straightforward parameter variation is possible, enabling studies which would be impossible in an experimental or clinical setup.

[Recommendations for documentation of incidents with medical devices in orthopaedic surgery]. / Empfehlungen zur Dokumentation von Vorkommnissen mit Medizinprodukten in der Orthopädischen Chirurgie.

The growing number of revisions in orthopaedic surgery as well as the multifactorial reasons for implant failure give cause for taking a closer look at the clinical documentation of adverse events. Based on our long-term experience it is our goal to present recommendations for an adequate documentation and filing. In the framework of the introduction of a quality management system (ISO 9001:2008) in our hospital, a process was developed for reportable incidents with medical devices regulating adequate documentation. Therefore, specific forms were developed. The retrievals are stored for subsequent damage analyses and are available for possible legal claims and tracking. A file should be opened for each reportable incident containing information about the event, a copy of the obligatory BfArM report, surgery report, medical device labels, radiographs and photographs. Declarations of agreement as well as handover certificates should be maintained in order to keep record of the retrievals. In order to assure consistent documentation, we recommend use of specific forms as presented in this paper. Identification of risk factors for implant failure and a long-term reduction of damage cases will only be possible under consequent incident reporting and responsible documentation of adverse events. Processing of cases of damage is accelerated and simplified by the presented recommendations and forms. Together with the newly established joint replacement registry, a higher quality of patient treatment and implant safety should be obtained.