title: Possible predictors for difficult removal of locking plates: A case-control study.
abstract: BACKGROUND
  Difficult removal of locking plates including less invasive stabilisation systems (LISSs) and locking compression plates (LCPs) sometimes occur. However, investigations of the mechanisms and correlated factors of complicated removal remain scant. This study aims to identify correlated factors for the difficult removal of locking plates and to propose suggestions for decision making regarding implant removal and the prevention of complicated removal.
  
  
  METHODS
  In total, 308 consecutive patients who underwent LCP/LISS removal from Sep. 2004 to Nov. 2013 were assessed. Using the Mann-Whitney U test, we analysed the correlation between difficult removal and the duration between open reduction and internal fixation (ORIF) and implant removal as well as the correlation between difficult removal and the patients' age. Using Chi Square test, we assessed the correlations between complicated removal and the size, location, insertion technique and cortical purchase of the locking head screw (LHS). Correlated factors were separately determined in upper and lower extremities. Rates of difficult removal in different fracture locations were evaluated, and postoperative complications were documented.
  
  
  RESULTS
  Of the total 308 patients, thirty-seven had intra-operative difficulties, and six patients experienced postoperative complications. Six out of fifteen patients with peri-elbow fractures and five out of seventeen patients with femur fractures suffered difficult removal, while four out of one hundred patients with malleolar fractures had intra-operative difficulties. Difficulties were experienced with 30 of 338 LCPs, 7 of 32 LISSs, 67 of 1533 small-diameter (≤ 3.5-mm) LHSs, and 12 of 442 large-diameter (≥ 4.5-mm) LHSs. Three LCPs and seventeen small-diameter LHSs were retained. A longer interval between ORIF and removal, younger age and bicortical screws correlated with difficult removal in the upper extremities, and a longer duration before removal, small-diameter LHS and minimally invasive insertion of LHS were predictors in the lower extremities.
  
  
  CONCLUSIONS
  Complications occur with LCP/LISS removal, and it should not be a routine procedure. If removal is indicated, performing surgery as soon as radiographs show fracture healing is recommended. Different considerations should apply when making decisions and removing implants from patients with different fracture sites.
authors.affiliation: Orthopedic Trauma, Peking University Third Hospital, No. 49, North Garden Rd, HaiDian District, Beijing 100191, China. Electronic address: houyf@bjmu.edu.cn.
authors.forename: Yun Fei
authors.initials: YF
authors.lastname: Hou
authors.affiliation: Orthopedic Trauma, Peking University Third Hospital, No. 49, North Garden Rd, HaiDian District, Beijing 100191, China. Electronic address: zhouf@bjmu.edu.cn.
authors.forename: Fang
authors.initials: F
authors.lastname: Zhou
authors.affiliation: Orthopedic Trauma, Peking University Third Hospital, No. 49, North Garden Rd, HaiDian District, Beijing 100191, China. Electronic address: tiany@bjmu.edu.cn.
authors.forename: Yun
authors.initials: Y
authors.lastname: Tian
authors.affiliation: Orthopedic Trauma, Peking University Third Hospital, No. 49, North Garden Rd, HaiDian District, Beijing 100191, China. Electronic address: jihq@bjmu.edu.cn.
authors.forename: Hong Quan
authors.initials: HQ
authors.lastname: Ji
authors.affiliation: Orthopedic Trauma, Peking University Third Hospital, No. 49, North Garden Rd, HaiDian District, Beijing 100191, China. Electronic address: zhangzs@bjmu.edu.cn.
authors.forename: Zhi Shan
authors.initials: ZS
authors.lastname: Zhang
authors.affiliation: Orthopedic Trauma, Peking University Third Hospital, No. 49, North Garden Rd, HaiDian District, Beijing 100191, China. Electronic address: drguoy@bjmu.edu.cn.
authors.forename: Yan
authors.initials: Y
authors.lastname: Guo
authors.affiliation: Orthopedic Trauma, Peking University Third Hospital, No. 49, North Garden Rd, HaiDian District, Beijing 100191, China. Electronic address: lvy@bjmu.edu.cn.
authors.forename: Yang
authors.initials: Y
authors.lastname: Lv
mesh_terms: D000328:Adult; D001860:Bone Plates; D001863:Bone Screws; D016022:Case-Control Studies; D020878:Device Removal / Q000379:methods; D005260:Female; D005264:Femoral Fractures / Q000601:surgery*; D005593:Fracture Fixation, Internal / Q000295:instrumentation*; D006801:Humans; D058430:Humeral Head / Q000601:surgery*; D008297:Male; D011183:Postoperative Complications / Q000601:surgery*; D011475:Prosthesis Failure; D011885:Radius Fractures / Q000601:surgery*; D012307:Risk Factors; D013997:Time Factors
keywords: Correlated factors; Difficult removal; LCP; LISS; Prevention