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Review Question - QID 5849

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QID 5849 (Type "5849" in App Search)
To be most effective at preventing post-operative sagittal plane deformity, poller blocking screws should be placed at which location labeled A-E in Figure A?
  • A
















  • A

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Figure A shows an extra-articular proximal tibial fracture demonstrating the most common sagittal deformity (procurvatum) observed with these fractures. The most appropriate position for blocking screws would be medial-lateral screws placed on the concave side of the deformity and posterior to the nail. This corresponds to Label C.

Poller blocking screws can be used during intramedullary nailing of proximal tibial fractures in an effort to prevent a procurvatum deformity. They are typically placed lateral and posterior relative to the nail trajectory in the proximal segment. Other modalities used to prevent this sagittal deformity includes a semiextended position of the knee for nail insertion, unicortical plating, and joystick manipulation of the proximal fracture segment.

Stedtfeld et al. describes the mechanical model for blocking screws. They state that two or more blocking screws can be placed in each plane (AP and lateral) alongside the nail to create a narrow canal for the nail. This allows for multiple points of fixation and realignment of the bone as the nail is passed.

Stinner et al. described the techniques for intramedullary nailing of proximal tibia fractures. They state in addition to the techniques described above, nail selection with distal Herzog bends may accentuate a sagittal plane deformity. This occurs because the the distal Herzog bend contacts the posterior cortex, which can create a wedge effect and translate the proximal segment anteriorly.

Illustration A shows the post-operative radiograph of an extra-articular proximal tibial fracture in Figure A, which was treated with IM nailing. Note the two posterior Poller blocking screws used in the proximal fragment to prevent procurvatum of the fracture. The positioning of these screws corresponds to Label C in Figure A.

Incorrect Answers:
Answer 1: This screw placement would be too proximal in the fracture fragment to act as an artificial cortex. This blocking screw is placed slightly posterior to the midline, from medial to lateral, in the proximal fragment.
Answers 2,4: These screws would either block the nail from passing down the canal, or significantly worsen the procurvatum deformity.
Answer 5: Position E may be used for the placement of a distal Schanz pin in the posterior malleolus. This would be used if a femoral distractor or an external fixation frame is being used as an adjunct for fracture reduction and fixation.

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