Why is there no washer for the smallest size Fragment Fixator System?
Because it is used only for extremely small fragments in hand surgery. If a washer could be used with a small size Fragment Fixator System implant this would mean that the fragment would be large enough for fixation with a medium size implant.
What types of bone can the Fragment Fixator System be used in?
It has been designed for use in cancellous bone and this is the position for most of the indications. However, it can also be used in cortical bone, especially in the middle of metacarpal or metatarsal bones.
How does this device achieve compression?
If, for example, a bone fragment at the base of a phalanx has to be reattached, the Fragment Fixator System implant is inserted in an oblique direction starting at the cancellous base of the bone with the tip directed towards the contralateral cortex …When the implant enters the bone it produces a thread. The implant is then progressively inserted until its tip meets the contralateral cortex. At this point the implant meets the resistance of the hard cortical bone. The thread makes several revolutions without advancing initially, leading to a stripping of the thread in the cancellous bone. The result is a gliding hole proximally and a threaded hole distally. A similar situation occurs if the near cortex of the fragment reaches the washer at the end of the Fragment Fixator System implant before the fracture gap is firmly closed. From chapter 34, by T. Gausepohl and D. Pennig, in Orthofix External Fixation in Trauma and Orthopaedics (Springer (is this Springer or Spring?) 2000).
When is it best to remove the implant?
Over time, the torque needed to extract Fragment Fixator System implants becomes greater than the torque needed to extract conventional screws, which have been in place for an equivalent treatment period. For this reason, it is best to remove Fragment Fixator System implants sooner than conventional screws, but not before the part being fixed has united.
How close to the shoulder should the implant be cut?
If the subcutaneous layer is sufficiently deep, the end of the implant should be covered with skin, to minimize the risk of infection. If it is planned not to remove the implant it is best to cut it as close to the bone surface as possible. If, however, removal is anticipated, 2-3 mm of shank should be left above the bone surface, to achieve a good grip for extraction. If the subcutaneous layer is not deep enough and the end of the implant is left proud of the skin, it should be draped with a sterile dressing.
How can the length of thread required be determined?
By overlaying the bone with an implant under the image intensifier or by measurement in the preoperative radiograph (but remember that this will be magnified).
How long is the compressive effect maintained for?
Extensive clinical use suggests that it lasts longer than with conventional small fragment screws, because these tend to back out at an earlier stage.