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Notes: Abstract. Osteochondromas can be complicated by mechanical irritation, compression or injury of adjacent structures, fracture, malignant transformation, and postoperative recurrence. Magnetic resonance imaging represents the most valuable imaging modality in symptomatic cases, because it can demonstrate typical features of associated soft tissue pathology, which can be differentiated from malignant transformation. Reactive bursae formation presents as an overlying fluid collection with peripheral contrast enhancement. Dislocation, deformation, and signal alterations of adjacent soft tissue structures can be observed in different impingement syndromes caused by osteochondromas. Magnetic resonance imaging provides excellent demonstration of arterial and venous compromise and represents the method of choice in cases with compression of spinal cord, nerve roots, or peripheral nerves, depicting changes in size, position, and signal intensity of the affected neural structures. Malignant transformation as the most worrisome complication occurs in approximately 1 % of solitary and 5–25 % of multiple osteochondromas. Magnetic resonance imaging is the most accurate method in measuring cartilage cap thickness, which represents an important criterion for differentiation of osteochondromas and exostotic (low-grade) chondrosarcomas. Cartilage cap thickness exceeding 2 cm in adults and 3 cm in children should raise the suspicion for malignant transformation. Finally, MR imaging can detect postoperative recurrence by depiction of a recurrent mass presenting typical morphological features of a cartilage-forming lesion.

Notes: Abstract A study was conducted to find out whether in a rear-impact motor vehicle accident, velocity changes in the impact vehicle of between 10 and 15 km/h can cause so-called “whiplash injuries”. An assessment of the actual injury mechanism of such whiplash injuries and comparison of vehicle rear-end collisions with amusement park bumper car collisions was also carried out. The study was based on experimental biochemical, kinematic, and clinical analysis with volunteers. In Europe between DM 10 and 20 billion each year is paid out by insurance companies alone for whiplash injuries, although various studies show that the biodynamic stresses arising in the case of slight to moderate vehicle damage may not be high enough to cause such injuries. Most of these experimental studies with cadavers, dummies, and some with volunteers were performed with velocity changes below 10 km/h. About 65% of the insurance claims, however, take place in cases with velocity changes of up to 15 km/h. Fourteen male volunteers (aged 28–47 years; average 33.2 years) and five female volunteers (aged 26–37 years; average 32.8 years) participated in 17 vehicle rear-end collisions and 3 bumper car collisions. All cars were fitted with normal European bumper systems. Before, 1 day after and 4–5 weeks after each vehicle crash test and in two of the three bumper car crash tests a clinical examination, a computerized motion analysis, and an MRI examination with Gd-DTPA of the cervical spine of the test persons were performed. During each crash test, in which the test persons were completely screened-off visually and acoustically, the muscle tension of various neck muscles was recorded by surface eletromyography (EMG). The kinematic responses of the test persons and the forces occurring were measured by accelerometers. The kinematic analyses were performed with movement markers and a screening frequency of 700 Hz. To record the acceleration effects of the target vehicle and the bullet vehicle, vehicle accident data recorders were installed in both. The contact phase of the vehicle structures and the kinematics of the test persons were also recorded using high-speed cameras. The results showed that the range of velocity change (vehicle collisions) was 8.7–14.2 km/h (average 11.4 km/h) and the range of mean acceleration of the target vehicle was 2.1–3.6 g (average 2.7 g). The range of velocity change (bumper car collisions) was 8.3–10.6 km/h (average 9.9 km/h) and the range of mean acceleration of the target bumper car was 1.8–2.6 g (average 2.2 g). No injury signs were found at the physical examinations, computerized motion analyses, or at the MRI examinations. Only one of the male volunteers suffered a reduction of rotation of the cervical spine to the left of 10° for 10 weeks. The kinematic analysis very clearly showed that the whiplash mechanism consists of translation/extension (high energy) of the cervical spine with consecutive flexion (low energy) of the cervical spine: hyperextension of the cervical spine during the vehicle crashes was not observed. All the tests showed that the EMG signal of the neck muscles starts before the head movement takes place. The stresses recorded in the vehicle collisions were in the same range as those recorded in the bumper car crashes. From the extent of the damage to the vehicles after a collision it is possible to determine the level of the velocity change. The study concluded that, the “limit of harmlessness” for stresses arising from rear-end impacts with regard to the velocity changes lies between 10 and 15 km/h. For everyday practice, photographs of the damage to cars involved in a rear-end impact are essential to determine this velocity change. The stress occurring in vehicle rear-end collisions can be compared to the stress in bumper car collisions.

Notes: Summary Presently, the degree of the hemophilic arthropathy is estimated by the classification system of Pettersson, which is recommended by the Orthopedic Advisory Committee of the World Federation of Hemophilia. This classification system bases upon plain radiographs of the joints and analyses only those changes which represent the progression of the arthropathy. The value of this classification system has been established by interobserver studies. However, it shows drawbacks at the exact definition of some parameters. Presently, it is more valuable for longitudinal than for transversal studies. Due to the possibilities of an adequate substitution therapy, only minor degrees of an arthropathy are observed in children. The ankle joints are more severly affected than the elbow joints and they more than the knee joints. This distribution is explained by an increasing sports activity in children. If more than 3 joint bleedings occur within a year the invent of an arthropathy must be presumed. Because the classification system of Pettersson analyses only osseous changes representing late changes, important early changes like hypertrophy of the synovialis and focal destruction of the joint cartilage are overlooked. Magnetic resonance imaging is suitable to show these early changes reliably. MRI can be recommended for the investigation of recurrently bleeding joints without evidence of major osseous changes and for decision making to perform a synovectomy.

Notes: Zusammenfassung Ein Tumorthrombus in der V. cava beim Nierenzellkarzinom als Ausdruck einer fortgeschrittenen Tumorerkrankung ist nicht mit einer schlechten Prognose gleichbedeutend. Fortschritte auf dem Gebiet der operativen Medizin ermöglichen es heute, entsprechende Tumorstadien kurativ operieren zu können, sofern keine Metastasen nachgewiesen sind. Das operative Vorgehen wird durch die kraniale Ausdehnung des Tumorthrombus determiniert. Eine rationelle, an den therapeutischen Möglichkeiten und der Prognose orientierte Diagnostik sollte vorrangig dem Metastasenausschluß sowie der Evaluation der Ausdehnung des Tumorthrombus dienen. Bildgebende Untersuchungen müssen nicht nur eine Selektion derjenigen Patienten ermöglichen, die von einer Operation profitieren können, sondern auch die für die Operationsplanung relevanten Informationen liefern. Moderne sonographische und CT-Untersuchungsverfahren oder die MRT erlauben sowohl eine zuverlässige Beurteilung des Lokalbefunds, der regionären Lymphknoten und Prädilektionsstellen einer möglichen Fernmetastasierung als auch die exakte Bestimmung der Ausdehnung des Tumorthrombus. Beim Nierenzellkarzinom mit Beteiligung der V. cava kann daher heute auf invasive angiographische Untersuchungen weitestgehend verzichtet werden.

Notes: Summary Purpose: To investigate whether phase-contrast MRA is a clinically suited approach to examine arteries of the pelvis and lower extremities. Methods: The study was divided into two parts, a volunteer study and patient study. Three MRA techniques – 2D TOF with venous saturation, 3D magnitude contrast and 2D phase contrast with ECG triggering – were intraindividually compared in 15 volunteers and evaluated by three blinded readers. Subsequently, a total of 230 vessel segments of 45 MRA studies using ECG-triggered phase contrast were compared with intraarterial DSA. All vessel segments were scored by three blinded readers using a five-point scale with DSA serving as the gold standard. Results: ECG-triggered phase contrast provided better image quality than the other MRA techniques as assessed by the Friedman test. Clinical studies demonstrated a significant correlation of DSA and MRA as assessed by the Spearman correlation and kappa statistics for individual readers. Conclusion: MRA of the pelvis and lower extremities may be performed with 2D ECG-triggered phase-contrast MRA within a reasonable time frame ( 〈 30 min). MRA slabs provide orientation similar to that with DSA projections and good to very good correlation of vessel pathology as shown by kappa statistics.