T. Prietzel

DICOM for Implantations—Overview and Application

Surgeons have to deal with many devices from different vendors within the operating room during surgery. Independent communication standards are necessary for the system integration of these devices. For implantations, three new extensions of the Digital Imaging and Communications in Medicine (DICOM) standard make use of a common communication standard that may optimise one of the surgeons presently very time-consuming daily tasks. The paper provides a brief description of these DICOM Supplements and gives recommendations to their application in practice based on workflows that are proposed to be covered by the new standard extension. Two of the workflows are described in detail and separated into phases that are supported by the new data structures. Examples for the application of the standard within these phases give an impression of the potential usage. Even if the presented workflows are from different domains, we identified a generic core that may benefit from the surgical DICOM Supplements. In some steps of the workflows, the surgical DICOM Supplements are able to replace or optimise conventional methods. Standardisation can only be a means for integration and interoperability. Thus, it can be used as the basis for new applications and system architectures. The influence on current applications and communication processes is limited. Additionally, the supplements provide the basis for further applications, such as the support of surgical navigation systems. Given the support of all involved stakeholders, it is possible to provide a benefit for surgeons and patients.

Diagnostic work-up strategy for periprosthetic joint infections after total hip and knee arthroplasty: a 12-year experience on 320 consecutive cases

BackgroundElective knee and hip arthroplasty is followed by infections in currently about 0.5–2.0 % of cases – a figure which is on the increase due to the rise in primary implants. Correct diagnosis early on is essential so that appropriate therapy can be administered. This work presents a retrospective analysis of the diagnoses of patients suffering infections after total hip or knee arthroplasty.Methods320 patients with prosthetic joint infection (PJI) following knee or hip arthroplasty were identified. They comprised a) 172 patients with an infection after total hip arthroplasty (THA): 56 % females (n = 96) and 44 % males (n = 76) with a mean age of 70.9 (39–92) years; and 148 patients with an infection after total knee arthroplasty (TKA): 55 % females (n = 82) and 45 % males (n = 66) with a mean age of 70.7 (15–87) years.ResultsAlthough significantly more TKA than THA patients reported pain, erythema, a burning sensation and swelling, no differences between the two groups were observed with respect to dysfunction, fever or fatigue. However, significant differences were noted in the diagnosis of loosening (THA 55 %, TKA 31 %, p < 0.001) and suspected infection using conventional X-rays (THA 61 %, TKA 29 %, p < 0.001). FDG-PET-CT produced very good results in nearly 95 % of cases. There were no differences between THA and TKA patients regarding levels of inflammation markers. Histological evaluation proved to be significantly better than microbiological analysis.SummaryThe clinical picture may be non-specific and not show typical inflammatory symptoms for a long time, particularly in PJI of the hip. As imaging only provides reliable conclusions after the symptoms have persisted for a long time, morphological imaging is not suitable for the detection of early infections. FDG-PT-CT proved to be the most successful technique and is likely to be used more frequently in future. Nevertheless, there are currently no laboratory parameters which are suitable for the reliable primary diagnosis of PJI. Diagnosis requires arthrocentesis, and the fluid obtained should always be examined both microbiologically and histologically.

On the permanent hip-stabilizing effect of atmospheric pressure

Hip joint dislocations related to total hip arthroplasty (THA) are a common complication especially in the early postoperative course. The surgical approach, the alignment of the prosthetic components, the range of motion and the muscle tone are known factors influencing the risk of dislocation. A further factor that is discussed until today is atmospheric pressure which is not taken into account in the present THA concepts. The aim of this study was to investigate the impact of atmospheric pressure on hip joint stability. Five joint models (Ø 28-44 mm), consisting of THA components were hermetically sealed with a rubber capsule, filled with a defined amount of fluid and exposed to varying ambient pressure. Displacement and pressure sensors were used to record the extent of dislocation related to intraarticular and ambient pressure. In 200 experiments spontaneous dislocations of the different sized joint models were reliably observed once the ambient pressure was lower than 6.0 kPa. Increasing the ambient pressure above 6.0 kPa immediately and persistently reduced the joint models until the ambient pressure was lowered again. Displacement always exceeded half the diameter of the joint model and was independent of gravity effects. This experimental study gives strong evidence that the hip joint is permanently stabilized by atmospheric pressure, confirming the theories of Weber and Weber (1836). On basis of these findings the use of larger prosthetic heads, capsular repair and the deployment of an intracapsular Redon drain are proposed to substantially decrease the risk of dislocation after THA.

Acellularization-Induced Changes in Tensile Properties Are Organ Specific - An In-Vitro Mechanical and Structural Analysis of Porcine Soft Tissues.

Introduction Though xenogeneic acellular scaffolds are frequently used for surgical reconstruction, knowledge of their mechanical properties is lacking. This study compared the mechanical, histological and ultrastructural properties of various native and acellular specimens. Materials and Methods Porcine esophagi, ureters and skin were tested mechanically in a native or acellular condition, focusing on the elastic modulus, ultimate tensile stress and maximum strain. The testing protocol for soft tissues was standardized, including the adaption of the tissue’s water content and partial plastination to minimize material slippage as well as templates for normed sample dimensions and precise cross-section measurements. The native and acellular tissues were compared at the microscopic and ultrastructural level with a focus on type I collagens. Results Increased elastic modulus and ultimate tensile stress values were quantified in acellular esophagi and ureters compared to the native condition. In contrast, these values were strongly decreased in the skin after acellularization. Acellularization-related decreases in maximum strain were found in all tissues. Type I collagens were well-preserved in these samples; however, clotting and a loss of cross-linking type I collagens was observed ultrastructurally. Elastins and fibronectins were preserved in the esophagi and ureters. A loss of the epidermal layer and decreased fibronectin content was present in the skin. Discussion Acellularization induces changes in the tensile properties of soft tissues. Some of these changes appear to be organ specific. Loss of cross-linking type I collagen may indicate increased mechanical strength due to decreasing transverse forces acting upon the scaffolds, whereas fibronectin loss may be related to decreased load-bearing capacity. Potentially, the alterations in tissue mechanics are linked to organ function and to the interplay of cells and the extracellular matrix, which is different in hollow organs when compared to skin.

Die Weber'schen Versuche zur hüftstabilisierenden Wirkung des atmosphärischen Druckes – ein historischer und experimenteller Rückblick

BACKGROUND The stabilising effect of atmospheric pressure on the hip joint was first described by the brothers Eduard and Wilhelm Weber in 1836. Later in 1837, they conducted an experiment in which they examined a weight-bearing cadaveric hip joint in an evacuable container and could repeatedly demonstrate dislocation of the femur head due to the significant reduction of surrounding pressure and its repositioning by normalisation of the pressure. In our study we aimed to honour the contribution of the Weber brothers, to reflect on the historical argument about the hip stabilising effect of atmospheric pressure they initiated, to repeat the famous experiment they did in 1837 using advanced sensors and radiological equipment and to demonstrate the consequences of the effect on total hip arthroplasty. METHOD A weight-bearing human cadaveric hip joint was placed in a radiolucent evacuable container, in which the pressure was reduced with a vacuum pump and normalised by opening a valve. Pressure and dislocation distance were measured continuously by sensors. The state of the hip joint was documented both by X-ray as well as by permanent fluoroscopy with video recording. RESULTS Conforming to the experiments published in 1837 we demonstrated dislocation of the hip joint as a result of a significant reduction of pressure. Normalisation of the pressure caused joint reduction. The ability of the cadaveric hip to bear weight depended to a great extent on its quality. Reduction of the pressure harmed the cadaveric hip and reduced the number of possible experiments. CONCLUSION The stabilising effect of atmospheric pressure on the hip joint is a fact, which was proved in 1836/37 by the Weber brothers, who conducted convincing experiments with human cadaveric hip joints. Nevertheless, the investigation into this relationship continues until today. We repeated and reproduced their experiment published in 1837 which irrefutably proved the stabilising effect of atmospheric pressure on the hip joint. The surgical application is of the utmost importance in the field of hip arthroplasty. Careful handling and reconstruction of the capsula, the use of size-adapted large hip balls as well as the intra-articular drainage provide the basis for maintaining the optimal mechanical environment and avoiding postoperative dislocation. Due to the variation in quality and anatomic characteristics of cadaveric hip specimens, we decided to use standardised model joints for further experiments.

Sind höhere Preise für größere Kopfdurchmesser in der Hüftendoprothetik medizinökonomisch vertretbar? Eine Analyse der Kosten und Effekte in Deutschland

Background: In total hip arthroplasty (THA), femoral head diameter has not been regarded as a key parameter which should be restored when reconstructing joint biomechanics and geometry. Apart from the controversial discussion on the advantages and disadvantages of using larger diameter heads, their higher cost is another important reason that they have only been used to a limited extent. The goal of this study was to analyse the price structure of prosthetic heads in comparison to other components used in THA. A large group of patients with hip endoprostheses were evaluated with respect to the implanted socket diameter and thus the theoretically attainable head diameter. Materials and Methods: The relative prices of various THA components (cups, inserts, stems and ball heads) distributed by two leading German manufacturers were determined and analysed. Special attention was paid to different sizes and varieties in a series of components. A large patient population treated with THA was evaluated with respect to the implanted cup diameter and therefore the theoretically attainable head diameter. Results: The pricing analysis of the THA components of two manufacturers showed identical prices for cups, inserts and stems in a series. In contrast to this, the prices for prosthetic heads with a diameter of 36-44 mm were 11-50 % higher than for 28 mm heads. Identical prices for larger heads were the exception. The distribution of the head diameter in 2719 THA cases showed significant differences between the actually implanted and the theoretically attainable heads. Conclusion: There are proven advantages in using larger diameter ball heads in THA and the remaining problems can be solved. It is therefore desirable to correct the current pricing practice of charging higher prices for larger components. Instead, identical prices should be charged for all head diameters in a series, as is currently established practice for all other THA components. Thus when reconstructing biomechanics and joint geometry in THA, it should be possible to recover not only leg length, femoral offset and antetorsion of the femoral neck, but also to approximately restore the diameter of the femoral head and thereby optimise the functional outcome.

Größere Köpfe kompensieren erhöhte Hüft-TEP-Luxationsgefahr bei Hochrisikopatienten

BACKGROUND Dislocation is a devastating complication after total hip arthroplasty (THA) and occurs in 2-5% of primary THA cases and 5-10% of revision THA cases. Assuming correct implantation, dislocation risk can be reduced primarily by capsular repair and the use of larger prosthetic heads. However, larger heads are also associated with risks like accelerated wear or implant loosening, which is why heads with a maximum diameter of 36 mm are currently standard in primary THA. In cases with high dislocation risk, the use of 40 mm and 44 mm heads should be considered. OBJECTIVES This study aimed to quantify THA dislocation risk and retrospectively analyze the course of disease in high-risk patients treated with 40 mm or 44 mm femoral heads after primary or revision THA, concerning dislocation and other complications suffered. MATERIALS AND METHODS All patients with increased THA dislocation risk, treated from 2009-2014, were evaluated regarding dislocations. The cases with installation of 40 mm or 44 mm prosthetic heads were classified using a self-developed 5-level risk score and retrospectively analyzed. RESULTS During the observation period, 288 THA interventions with increased dislocation risk were performed. In 278 cases with ball diameters ≤ 36 mm the dislocation rate was 15.1% (n=42). In 10 high dislocation-risk cases (3A to 4B according to recommended scoring system), 40 mm and 44 mm heads were used. After a 22.8 month mean follow-up, no THA dislocations were reported. CONCLUSION Our results with 40 and 44 mm heads and the existing literature confirm much higher joint stability and, thus, significantly reduced dislocation risk with larger prosthetic heads in THA. Their use is, therefore, justified in high-risk patients and should be considered in future THA.

[Larger heads compensate for an increased risk of THA dislocation in high-risk patients].

BACKGROUND Dislocation is a devastating complication after total hip arthroplasty (THA) and occurs in 2-5% of primary THA cases and 5-10% of revision THA cases. Assuming correct implantation, dislocation risk can be reduced primarily by capsular repair and the use of larger prosthetic heads. However, larger heads are also associated with risks like accelerated wear or implant loosening, which is why heads with a maximum diameter of 36 mm are currently standard in primary THA. In cases with high dislocation risk, the use of 40 mm and 44 mm heads should be considered. OBJECTIVES This study aimed to quantify THA dislocation risk and retrospectively analyze the course of disease in high-risk patients treated with 40 mm or 44 mm femoral heads after primary or revision THA, concerning dislocation and other complications suffered. MATERIALS AND METHODS All patients with increased THA dislocation risk, treated from 2009-2014, were evaluated regarding dislocations. The cases with installation of 40 mm or 44 mm prosthetic heads were classified using a self-developed 5-level risk score and retrospectively analyzed. RESULTS During the observation period, 288 THA interventions with increased dislocation risk were performed. In 278 cases with ball diameters ≤ 36 mm the dislocation rate was 15.1% (n=42). In 10 high dislocation-risk cases (3A to 4B according to recommended scoring system), 40 mm and 44 mm heads were used. After a 22.8 month mean follow-up, no THA dislocations were reported. CONCLUSION Our results with 40 and 44 mm heads and the existing literature confirm much higher joint stability and, thus, significantly reduced dislocation risk with larger prosthetic heads in THA. Their use is, therefore, justified in high-risk patients and should be considered in future THA.

Schmerzhafte Hypertrophie der zweiten Zehe infolge Osteoidosteom des Endgliedes

The rare case of an osteoid osteoma in the distal phalanx of the 2nd toe resulting in painful enlargement and hypertrophy of the entire toe in a 12-year-old girl is discussed. The tumour was excised and the oversize of the toe was corrected by exarticulation of the distal phalanx. 18 months postoperatively the patient demonstrates normal function of her forefoot without complaints or signs of inflammation.

Diagnostisches Vorgehen bei Verdacht auf maligne Knochen- und Weichteiltumoren

ZusammenfassungDiagnostik und Therapie der muskuloskelettalen Malignome stellen eine große Herausforderung für alle beteiligten Ärzte dar. Im Sinne einer optimalen Versorgung dieser schwerkranken Patienten ist eine enge Kooperation zwischen allen beteiligten medizinischen Fachdisziplinen (u. a. diagnostische Radiologie, Pathologie, Nuklearmedizin, medizinische Onkologie, Strahlentherapie, Orthopädie, Chirurgie) unverzichtbar. Vor diesem Hintergrund stellen interdisziplinäre Tumorkonferenzen eine wertvolle Bereicherung der Zusammenarbeit dar, wobei gerade in den sogenannten Tumorzentren eine qualitätssichernde Dokumentation gewährleistet ist. Dabei sollten regionale oder überregionale Therapieprotokolle zur Behandlung verschiedener Tumorentitäten berücksichtigt werden.