Der Unfallchirurg
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Comparative Study
[Biomechanical stability with a new artificial vertebral body implant. 3-dimensional movement analysis of instrumented human vertebral segments].
The authors present a new implant for vertebral body replacement in the thoracic and lumbar spine. The titanium implant is designated for reconstruction of the anterior column in injury, posttraumatic kyphosis or tumor of the thoracolumbar spine. The instrumentation has to be supplemented by a stabilizing implant. After positioning, the implant is distracted in situ, through which best contact to adjacent end-plates and 3-dimensional stability should be provided. The possibility of secondary dislocation or loss of correction should thereby be minimized. ⋯ The posterior fixation was found to offer superior stability compared to the anterior one. Synex was at least comparable to MOSS for suspensory replacement of the vertebral body in the thoracolumbar spine. The evidence of higher biomechanical stability with Synex leads to the probability of a higher rigidity in vivo. Due to the distractability of Synex, a better intervertebral compression was achieved. Therefore, an additional tightening of the posterior fixator after insertion of Synex was not necessary, in contrast to the Harms cage.
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The change of treatment modality in osteosynthesis is based on two principles. On one hand, one can exchange the implant as part of a two step procedure to reduce side effects of stabilizing fractures. On the other hand, a reosteosynthesis may be required for treatment of complications. ⋯ External fixator devices have been used for stabilization of long bone fractures with severe soft tissue damage using the two step procedure in the past decades; nowadays unreamed nailing is commonly preferred. Reosteosynthesis may be appropriate for the treatment of failing of osteosynthesis; they can also be used due to delayed union or nonunion of fractures, osseous deficiency or infection. In the case of failing osteosynthesis, the reasons for failing have to be studied thoroughly and a variety of subsequent procedures has to be taken into consideration for successful treatment.
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A patellar dislocation is usually understood to mean a lateral dislocation of the patella. Medial patellar dislocations have mainly been described after surgical treatment, such as release of the lateral retinaculum. Here a case of medial patellar dislocation is reported which did not occur subsequent to surgery. Wilberg-III patella, genu recurvatum with patella alta and a m. vastus medialis insertion widely distal to the patella were predisposing factors.