Surface polishing positively influences ease of plate and screw removal

Abstract

Difficulties removing temporary fracture fixation devices due to excessive bony on-growth results in extended surgical time leading to excessive blood loss, debris contamination and potentially refracture. Commercially available locking plates and screws are manufactured for clinics with a micro-rough surface, which contributes to the excessive bony on-growth reported. We have applied polishing technology to commercially pure titanium locking compression plates (LCP) and titanium-6%aluminium-7%niobium (TAN) plates and screws to assess if it can alleviate problems with strong bony overgrowth. Samples were implanted for 6, 12 and 18 months in a bilateral sheep tibia non fracture model and assessed for screw removal torque, percentage of bone contact and tissue-material response. Both electropolishing (p=0.001) and paste polishing (p=0.010) of TAN screws significantly reduced the mean torque required for removal compared to their micro-rough counterparts. This was accompanied by a trend for a lower percentage of bone contact for polished screws. This difference in bone contact was significant for paste polished TAN screws (p<0.001) but not electropolished TAN screws (p=0.066). Ex vivo, soft tissue removal was much easier (~five minutes) for polished constructs, which was difficult and at least four times longer for standard micro-rough constructs. We suggest that polishing of locked plate/screw systems will improve ease of removal and reduce implant related removal complications encountered due to excessive strong bony on-growth while maintaining biocompatibility and implant stability. Future studies aim to assess the potential of this technology in the next level of complication, a fracture model.

Titanium and steel fracture fixation plates with different surface topographies: Influence on infection rate in a rabbit fracture model

“…It was necessary to modify the screw entry procedure for polished screws, which would be an easily overcome manufacturing issue should such screws become clinically available. Overall, these findings support earlier results that surface polishing titanium implants offer eased implant removal, without compromising stability, or infection risk [15,26,32,34].…”

“…Titanium and stainless steel both offer acceptable mechanical properties and biocompatibility; however, there are certain differences that may contribute to our observation. One explanation for the higher bacterial count in EPSS group may be the fibrous capsule that surrounds these implants [26]. Steel is usually electropolished to a smooth surface, whereas titanium in its standard form has a microrough surface [7].…”

“…Polishing of titanium and its alloys has been investigated as a potential approach for easing implant removal in fracture care [26,32,33]. It has already been clinically implemented.…”

Indications for implant removal after fracture healing: a review of the literature

“…Removal of TAN implants can be extremely difficult due to screwhead locking into the plate or bone overgrowth at the implant surface. Richards et al described that not only the composition of the alloy, but also its surface structure matters in these cases [22][23][24][25][26].…”

Case Report: A Technique to Remove a Jammed Locking Screw from a Locking Plate

“…A locking screw that cannot be removed with a torque-limiting screw is technically jammed whether it is attributable to cold welding or cross-threading or just over-tightened. Bony overgrowth is a substantial problem in titanium implants [4,7]. As the screws were so tightly jammed that the conical extraction screw failed to remove the screw, the technique of using a foil [9] in the stripped screw head recess before the conical extraction screw would have failed.…”