Krettek, J Orthop Trauma 1999 - The Mechanical Effect of Blocking Screws ("Poller Screws") in Stabilizing Tibia Fractures with Short Proximal or Distal Fragments after Insertion of Small-Diameter Intramedullary Nails
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The Mechanical Effect of Blocking Screws ("Poller Screws") in Stabilizing Tibia Fractures with Short Proximal or Distal Fragments after Insertion of Small-Diameter Intramedullary Nails
Krettek, Tscherne, et al.·J Orthop Trauma·1999·281 citations·Biomechanical study
Objectives and Hypothesis: To evaluate the mechanical effects of medial and lateral blocking screws in supplementing intramedullary nail fixation of high proximal and low distal tibial fractures treated with small-diameter intramedullary nails.
Methods
Study Design:
Intact fresh human cadaveric tibiae were sectioned to provide 10 distal segments measuring 70 millimeters and 10 proximal segments measuring 90 millimeters.
In the distal segments, stainless steel solid 8-millimeter tibial nails were advanced to 8 millimeters from the ankle joint.
2 transverse and one anterior-posterior (AP) locking screw were inserted using a custom-made jig.
The same jig was used for the placement of a medial and a lateral blocking screw (BS) in the AP direction, 9 millimeters above the superior most interlocking screw and 8 millimeters distal to the lower end of the segment.
In the proximal segments, 2 interlocking screws (both static and dynamic screws) were placed in a medial-lateral direction with the use of the insertion handle.
A jig was used for placement of a medial and a lateral BS in the AP direction, 9 millimeters below the lower transverse interlocking screw and 16 millimeters proximal to the lower end of the segment.
The bone-implant construct (BIC) was embedded and fixed in a materials testing machine.
The BICs were loaded in the medial-lateral direction at a distance of 185 millimeters from the nail ends with loads from -150 newtons to + 150 newtons.
Force-displacement curves were recorded before and after insertion of the BSs.
Results
In proximal BICs, the addition of BSs decreased the deformation of the BICs 25 percent, from 8.9 +/- 1.9 degrees [mean +/- standard deviation (SD)] in the control group to 6.8 +/-1.1 degrees in the BS group (mean +/- SD) (p < 0.0001).
In distal BICs, the addition of BSs decreased the deformation of the BICs 57 percent, from 9.5 +/- 1.4 degrees (mean +/- SD) in the control group to 4.0 +/- 1.0 degrees in the BS group (mean +/- SD) (p < 0.0001).
Conclusions
The study suggests that medial and lateral blocking screws can increase the primary stability of distal and proximal metaphyseal fractures after nailing and can be an effective tool for selected cases that exhibit malalignment and/or instability.
The Mechanical Effect of Blocking Screws ("Poller Screws") in Stabilizing Tibia Fractures with Short Proximal or Distal Fragments after Insertion of Small-Diameter Intramedullary Nails
Krettek, Tscherne, et al.·J Orthop Trauma·1999·281 citations·Biomechanical study
Objectives and Hypothesis: To evaluate the mechanical effects of medial and lateral blocking screws in supplementing intramedullary nail fixation of high proximal and low distal tibial fractures treated with small-diameter intramedullary nails.
Methods
Study Design:
Intact fresh human cadaveric tibiae were sectioned to provide 10 distal segments measuring 70 millimeters and 10 proximal segments measuring 90 millimeters.
In the distal segments, stainless steel solid 8-millimeter tibial nails were advanced to 8 millimeters from the ankle joint.
2 transverse and one anterior-posterior (AP) locking screw were inserted using a custom-made jig.
The same jig was used for the placement of a medial and a lateral blocking screw (BS) in the AP direction, 9 millimeters above the superior most interlocking screw and 8 millimeters distal to the lower end of the segment.
In the proximal segments, 2 interlocking screws (both static and dynamic screws) were placed in a medial-lateral direction with the use of the insertion handle.
A jig was used for placement of a medial and a lateral BS in the AP direction, 9 millimeters below the lower transverse interlocking screw and 16 millimeters proximal to the lower end of the segment.
The bone-implant construct (BIC) was embedded and fixed in a materials testing machine.
The BICs were loaded in the medial-lateral direction at a distance of 185 millimeters from the nail ends with loads from -150 newtons to + 150 newtons.
Force-displacement curves were recorded before and after insertion of the BSs.
Results
In proximal BICs, the addition of BSs decreased the deformation of the BICs 25 percent, from 8.9 +/- 1.9 degrees [mean +/- standard deviation (SD)] in the control group to 6.8 +/-1.1 degrees in the BS group (mean +/- SD) (p < 0.0001).
In distal BICs, the addition of BSs decreased the deformation of the BICs 57 percent, from 9.5 +/- 1.4 degrees (mean +/- SD) in the control group to 4.0 +/- 1.0 degrees in the BS group (mean +/- SD) (p < 0.0001).
Conclusions
The study suggests that medial and lateral blocking screws can increase the primary stability of distal and proximal metaphyseal fractures after nailing and can be an effective tool for selected cases that exhibit malalignment and/or instability.