[Endoprosthetic tumor replacement : Reconstruction of the extensor mechanism and complications]. / Tumorendoprothetik : Rekonstruktion des Streckapparates und Komplikationen.

BACKGROUND: The reconstruction of the extensor mechanism around the knee is an essential part of tumorresection and tumor arthroplasty in orthopaedic oncology for functional rehabilitation of quality of life and daily activities. OBJECTIVES: Operative procedures, treatment options and management of complications with reconstruction of the extensor mechanism after tumor resection around the knee depend on the type of arthroplasty. MATERIALS AND METHODS: Description of the different treatment option for extensor deficiency divided into infra- and suprapatellar modalities. RESULTS: The operative procedure is always an individual decision depending on the size of the tumor and its localisation. The extensor mechanism is reconstructed with autogenic, allogenic or synthetic material in combination with tumor arthroplasty. CONCLUSIONS: Extensor reconstruction (supra-/infrapatellar) is an essential part of tumor resection and tumor arthroplasty around the knee. Often, low functional results and high levels of complications (arthrofibrosis, rerupture extensor mechanism, periprosthetic joint infection) are seen in these highly demanding cases in orthopaedic oncology.

[Avascular necrosis of the hip - diagnosis and treatment]. / Hüftkopfnekrose - Diagnostik und Differenzialtherapie.

Femoral head necrosis is an ischaemic bone necrosis of traumatic or nontraumatic pathogenesis which can lead to hip joint destruction in young age. It is today the indication for 10 % of all the total hip joint replacements. Known aetiologies of nontraumatic femoral head necrosis are alcoholism, steroids, sickle cell anaemia, caisson, and Gaucher's disease. Further risk factors are chemotherapy, chronic inflammatory bowel disease, systemic lupus erythematosus, and multiple sclerosis, in which also steroids are involved. Gravidity is another risk factor, but still idiopathic pathogenesis is found. In diagnosis, the ARCO-classification of the Association for the Research of Osseous Circulation is essential. While stage 0 can only be found histologically, the reversible early stage 1 shows MR signal changes. In the irreversible early stage 2, first native x-ray changes are seen as lower radiolucency reflects new bone apposition on dead trabeculae. In stage 3, subchondral fracture follows, and in stage 4 secondary arthritis of the hip. Established therapy in stage 1 is core decompression, physiotherapy, and more and more also bisphosphonates. Sufficient data to support extracorporeal shock wave therapy are still lacking. Stem cell therapy seems to be a promising new therapy method in stage 2. In stage 2 and 3 mainly proximal femoral osteotomies and (non)vascularised bone transplantation are performed. In stage 4, depending on size and location of the necrotic zone and pathology of the adjacent bone, resurfacing or short stem hip arthroplasty can be performed. However, conventional THA is still golden standard. The problem and challenge, however, is the often young patient age in femoral head necrosis. Especially chemotherapy-associated osteonecrosis in leukaemia is found in patients in their second decade of life. Therefore, the hip should be preserved as long as possible.

High-resolution, selective water-excitation MRI-based cartilage thickness and volume measurements in upper extremity joints.

The objective if this study was to obtain quantitative data about cartilage thickness and volume in joints of the upper extremity by applying a high resolution MR imaging technique, and to validate these data by A-module ultrasound and CT arthrography.
10 elbow and 7 shoulder joints (age 20 to 69 yrs) were investigated with a 3D gradient echo sequence with selective water excitation (TR 18 ms; TE 9 ms; FA 250, resolution 1 x 0,25 x 0,25 mm2, imaging time 19 min.). After trilinear interpolation to a 0,125 x 0,125 mm2 in-plane resolution, snake-based segmentation, and 3D reconstruction, cartilage volume and thickness were determined with a 3D Euclidean distance transformation algorithm. For validation the cartilage volume and thickness values were compared with CT arthrography and A-mode ultrasound.
The mean cartilage thickness of the elbow joint ranged between 0,99 and 1,35 mm and that of the shoulder between 1,18 and 1,79 mm. The mean systematic difference between the elbow cartilage volume obtained from MR imaging and CT arthrography was -0,11% (-6,0 mm3) and the mean random difference 5,7% (314 mm3). Only in the distal humerus, the mean cartilage thickness (average = 1,35 mm) was overestimated relative to CT arthrography (+20,7%, 0,23 mm). In comparison to A-mode ultrasound a slight underestimation was found in the distal humerus (-6,0%, -0,05 mm) and in the shoulder joint surfaces (humeral head: -22%; -0,26 mm; glenoid cavity: -13%; -0,25 mm). With few exception, there were no significant differences between MRI, CT arthrography and ultrasound in the other joint surfaces of the upper extremity joints (random deviations between 0,08 and 0,39 mm).
This specific MR imaging and postprocessing technique can be used for non-invasive determination of cartilage volume and thickness in joints with thin cartilage layers such as the shoulder with a high degree of accuracy.