Wear and corrosion of sliding counterparts of stainless-steel hip screw-plates

Abstract

Wear of the lag screw and barrel of stainless-steel sliding hip screw-plates (SHSP) produces particles and corrosion that jam the sliding screw. This alters the mechanics of the SHSP causing failure and difficulty in removal. We examined 15 surgically-removed SHSP for the extent of wear and corrosion of metal, and damage to the surrounding tissue. SHSP implants were in place from 2 months to 11 years (average 38.9 months) and they were removed because of fracture non-union, implant fracture or pain. None was infected. Electron microscopy was used to examine the implant surfaces and to determine the chemistry of corrosion products both on the metal and in the tissue. The distal ends of all the lag screws and inside walls of the barrels showed wear and corrosion. The severity of corrosion increased with increasing duration of implant use. Surfaces of the inside walls of the barrels were rough from the manufacturing process. This had contributed to wear. Better manufacturing practice to improve surface smoothness of the lag screws and inside walls of the barrels is needed. Use of cobalt–chromium alloys would improve hardness and resistance to corrosion compared with the stainless steel presently used, which would be an advantage for sliding hip screw-plates in younger patients. Deliberate texturing of screws is counter productive and should be avoided.