title: Effects of third fragment size and displacement on non-union of femoral shaft fractures after locking for intramedullary nailing.
abstract: BACKGROUND
  The femoral shaft fractures with large fragments makes anatomical reduction challenging and often results in non-union. In some studies, the degree of fragment displacement was reported to have affected non-union, but the association between the one fragment size and degree of displacement has not been fully clarified. Therefore we performed a retrospective study to assess: (1) the more influential factor of non-union: the degree of fragment displacement, or the fragment size? (2) the non-union rates according to different sizes and degrees of displacement.
  
  
  OBJECTIVE
  The degree of displacement is the more potent factor of non-union than the third fragment size in femoral shaft fractures.
  
  
  METHODS
  We assessed retrospectively 64 cases, which could be followed up for longer than one year. Fragments were divided according to the length of their long axis into three groups: group A (0-3.9cm), (n=21); group B (4-7.9cm), (n=22); group C (8cm or more), (n=21). Fragment displacement was also assessed in the proximal (P) or distal (D) end to the nearest cortex of the femoral shaft, and divided into the following groups: group P1 (n=44) or D1 (n=47), (0-9mm); group P2 (n=10) or D2 (n=11), (10-19mm); group P3 (n=7) or D3 (n=3), (20-29mm); and group P4 (n=3) or D4 (n=3), (30mm or more).
  
  
  RESULTS
  The bone union rate was 86% in the small (less than 8cm) fragment groups and 71% in the large (8cm or more) fragment group (P=0.046). With respect to the degree of displacement, the union rate was lower (P=0.001) and the average union time was longer (P=0.012) in the 20mm or more group for both the proximal fragment part and the distal fragment part (P=0.002, P=0.014). A logistic regression analysis underlined the displacement in the proximal site (OR: 0.298, 95% CI: 0.118-0.750) as in the distal site (OR: 0.359, 95% CI: 0.162-0.793) as a larger effect on union rate than the fragment size that as no effect in logistic regression (OR 3.8, 95% CI: 0.669-21.6).
  
  
  CONCLUSIONS
  Non-union develops significantly more frequently in femoral shaft fractures with fragments 8cm or longer or when the displacement in the proximal area is 20mm or greater and 10mm or greater in the distal area during the intramedullary nailing procedure. Regarding union rate, the degree of displacement has more influence than the third fragment size in femoral shaft fractures.
  
  
  METHODS
  IV, retrospective cohort study.
authors.affiliation: Department of Orthopedic Surgery, Research Institute of Clinical Medicine of Chonbuk National University-Biomedical Research Institute of Chonbuk National University Hospital Chonbuk National University Medical School, 634-18, Keum Am-dong, Dukjin-gu, Jeonju, Chonbuk, 561-712, Korea.
authors.forename: J R
authors.initials: JR
authors.lastname: Lee
authors.affiliation: Department of Orthopedic Surgery, Research Institute of Clinical Medicine of Chonbuk National University-Biomedical Research Institute of Chonbuk National University Hospital Chonbuk National University Medical School, 634-18, Keum Am-dong, Dukjin-gu, Jeonju, Chonbuk, 561-712, Korea.
authors.forename: H-J
authors.initials: HJ
authors.lastname: Kim
authors.affiliation: Department of Orthopedic Surgery, Research Institute of Clinical Medicine of Chonbuk National University-Biomedical Research Institute of Chonbuk National University Hospital Chonbuk National University Medical School, 634-18, Keum Am-dong, Dukjin-gu, Jeonju, Chonbuk, 561-712, Korea. Electronic address: osdr2815@naver.com.
authors.forename: K-B
authors.initials: KB
authors.lastname: Lee
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001858:Bone Nails; D018483:Diaphyses / Q000000981:diagnostic imaging / Q000293:injuries; D005260:Female; D005264:Femoral Fractures / Q000000981:diagnostic imaging* / Q000601:surgery; D005269:Femur / Q000000981:diagnostic imaging / Q000293:injuries*; D005594:Fracture Fixation, Intramedullary; D005599:Fractures, Ununited / Q000209:etiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D016896:Treatment Outcome; D055815:Young Adult
keywords: Displacement; Femoral shaft fracture; Fracture fragments; Union rate