Influencing factors for difficult removal of locking head screws and locking compression plate

Abstract

Objective To analyze the factors that may lead to difficult removal of locking compression plate (LCP) and locking head screws (LHS). Methods We retrospectively reviewed medical records of the 308 patients with extremity fracture who underwent implant removal at our institution from September 2004 to November 2013. They were 190 males and 118 females, with an average age of 36.8 years (from 12 to 82 years). The mean interval from hardware implantation to removal was 16.3 months (from 2 to 56 months). Their fractures involved humerus, ulna, radius, clavicle, femur, tibia and ankle joint. We extracted the following data: difficulty in removal; duration of implant stay in the body; size, position, insertion technique and cortical purchase of LHS; positional relationship between LHS and LCP (orthogonal or non-orthogonal). After we identified potential factors that might have been associated with difficult removal of LHS and LCP in fractures of upper and lower limb respectively using Mann Whitney U test and Chi-square test, we used multiple logistic regression analysis to determine the independent influencing factors. Results Of the 308 patients we analyzed, difficult removal occurred in 37. Fractures at distal humerus had the highest incidence of difficult removal (41.7%), followed by fractures at proximal forearm (33.3%), proximal femur (33.3%) and femur shaft (33.3%). The incidence in malleolar fractures was low (4.0%). Logistic regression analysis suggested the following independent risk factors: long implant stay in the body, young age, and bicortical purchase of LHS for patients with upper extremity fracture (P < 0.05); long implant stay in the body, LHS of a small diameter and percutaneous insertion of LHS for patients with lower extremity fracture (P < 0.05). Conclusions If implant removal is indicated, surgery should be performed as soon as radiographs show fracture healing. To reduce the incidence of difficult removal of LHS and LCP, surgeons should in their preoperative plan and actual procedures take into account different fracture locations and different factors that may lead to difficulty in removal. Key words: Bone plates; Bone nails; Device removal; Factor analysis, statistical