Thesis

98 Part I Chapter 4 are followed by SPECT/CT. For SPECT/CT of the wrist and hand patients are placed in “superman” positionwith arms outstretched. Alternatively, in patients with obstructive shoulder conditions, the wrists can be positioned in pronation, lying on a X-rays transparent flat pillow set on anterior face of patient`s pelvis, while patient is lying supine. Typical SPECT parameters are: matrix 128x128, 128 angles, 20s/angle, step-andshoot mode. For CT we recommend to performdiagnostic CT (40-335mA, 80-130 keV, 0.33-2.0mm slice thickness) in order to provide exact anatomic details. To increase the diagnostic performance especially if evaluation of cartilage or ligaments (scapholunate [SL] and lunotriquetral [LT] ligaments) is requested - additional intraarticular contrast can be administered before late phase SPECT/CT images are acquired, in order to obtain so-called SPECT/CT arthrography images (Figure 1) [5, 6]. Assessment of osteosynthesis/non union Fracture of the distal radius is a very common osteoporotic fracture. The majority of hand fractures affect the digits (60%) followed by the metacarpals (30%) and the carpal bones (10%) [7]. Of all carpal bones, the scaphoid is by far most frequently involved in fractures, accounting for approximately 89%, followed by the triquetrum (7%) and others [7]. Examples of fractures usually requiring osteosynthesis are dislocated joint fractures, open fractures, fractures accompanied by nerve/vessel injury or compartment syndrome and pathologic fractures. The aimof osteosynthesis is always to achieve exact anatomic reposition of the bony fragments. Different materials like plates, screws and wires are used to fix wrist and hand fractures. Many factors influence the likelihood of successful bone healing like perfusion of bony fragments, soft tissue coverage and successful fixation. Smoking and osteoporosis are typical risk factors for developing nonunion. The definition of nonunion or pseudarthrosis depends on the site and “age” of the fracture: in general, if a fracture is not healed after 6 months and no evidence of healing is assessable during the last months, a nonunion can be diagnosed. In cases of nonunion different surgical procedures are used: re-osteosynthesis, bone grafting and sometimes even stem cell injection [8]. Assessment of viability of nonunion is crucial for therapy planning since non-viable nonunions require resection of necrotic bone tissue and more complex reconstructions. SPECT/CT helps to diagnose non-viable nonunions with a relatively poor sensitivity of 50% but very good specificity (100%) in a small study of Liodakis, et al. [9]. Missing radionuclide uptake (cold defect) often corresponding with free or sclerosed bone fragments are typical signs for non-viable bone fragments (Figure 2). Due to physiologic bone turnover increased tracer uptake can persist many months after bone surgery expressing bone remodeling after trauma. Thus, CT morphology and time of surgery should always be considered to avoidmisinterpretation of SPECT/ CT following osteosynthesis.

RkJQdWJsaXNoZXIy MjY0ODMw