LETTER
The Broken Screw Dilemma To the Editor: The article entitled “Treatment of infantile Blount disease with lateral tension band plating” reported a favorable outcome in 89% of patients. Although this compares favorably with most osteotomy reports, figure 3 nicely illustrates an avoidable error
TO THE
EDITOR
that precludes an even higher success rate. If the distal (metaphyseal) end of the plate is not coapted to the bone, then the screw shank is exposed to 3point bending stresses. As a result, the tension band effect is lost and the screw is liable to fatigue and failure at the point where the shank enters the bone. Regardless of implant size, design (solid vs. cannulated), and material (titanium vs. stainless steel), screws are not well suited to resist
3-point bending and ultimate failure is inevitable. Although there is conjecture that the size of the patient (body mass index), activity level, and size of the implant may play a role, none of these factors have been proven. The common denominator seems to be technique related. Peter M. Stevens, MD Department of Orthopaedics University of Utah, Salt Lake City, UT
The 8-plate is licensed to Orthofix by P.M.S., in return for royalties.
J Pediatr Orthop
Volume 34, Number 3, April/May 2014
www.pedorthopaedics.com |
e5
The Broken Screw Dilemma To the Editor: The article entitled “Treatment of infantile Blount disease with lateral tension band plating” reported a favorable outcome in 89% of patients. Although this compares favorably with most osteotomy reports, figure 3 nicely illustrates an avoidable error
TO THE
EDITOR
that precludes an even higher success rate. If the distal (metaphyseal) end of the plate is not coapted to the bone, then the screw shank is exposed to 3point bending stresses. As a result, the tension band effect is lost and the screw is liable to fatigue and failure at the point where the shank enters the bone. Regardless of implant size, design (solid vs. cannulated), and material (titanium vs. stainless steel), screws are not well suited to resist
3-point bending and ultimate failure is inevitable. Although there is conjecture that the size of the patient (body mass index), activity level, and size of the implant may play a role, none of these factors have been proven. The common denominator seems to be technique related. Peter M. Stevens, MD Department of Orthopaedics University of Utah, Salt Lake City, UT
The 8-plate is licensed to Orthofix by P.M.S., in return for royalties.
J Pediatr Orthop
Volume 34, Number 3, April/May 2014
www.pedorthopaedics.com |
e5
