title: Morphology of the posteromedial fragment in pertrochanteric fractures: A three-dimensional computed tomography analysis.
abstract: BACKGROUND
  In this study we describe the morphology of the posteromedial fragment in pertrochanteric fractures using 3D CT scans and answer two questions 1) Do differences exist between the 3D CT appearances of posteromedial fragments and the depictions made in the AO classification 2) Does the posteromedial fragment affect stability in pertrochanteric fractures, in terms of fracture collapse?
  
  
  METHODS
  Preoperative CT scans of eight 31-A1 and fifty 31-A2 fractures were analysed. The presence of PM fragment, its fragmentation, greater trochanter (GT) involvement, lesser trochanter (LT) fragment size (in terms of its posterior and medial extent as well as LT length), LT fragment displacement (in terms of medial displacement and rotation) were determined. All fractures were treated with a DHS. Fracture collapse was determined on postoperative radiographs. The relationship between fracture collapse and patient factors including age, gender, fracture type (A1 versus A2), characteristics of the posteromedial fragment, and the presence of a lateral wall fracture were determined.
  
  
  RESULTS
  Three out of eight 31-A1 fractures demonstrated a separate GT fragment (three part fracture). Out of the 50 31-A2 fractures, 12 had a single PM fragment, which included the LT and GT in continuity. The more common four part fractures seem to form by further fragmentation of this basic form. In A2 fractures, the GT was almost always broken and the broken fragment comprised a mean 56% of normal GT. The LT fragment involved an average of 74% of the posterior wall, and an average of 36% of the medial wall of the proximal femur. Larger LT fragments were less displaced as compared to smaller fragments. Univariate regression analyses revealed that fracture collapse was significantly correlated with fracture type (A1 versus A2, p 0.036), GT size (p 0.002) and the presence of a lateral wall fracture (p<0.001).
  
  
  CONCLUSIONS
  This study revealed some important differences between the 3D CT appearances and AO classification of pertrochanteric fractures. Further, neither fragmentation of the posteromedial fragment, nor the size of the lesser trochanter fragment was found to predict stability in pertrochanteric fractures. A perioperative lateral wall fracture is the main determinant of stability in these fractures.
authors.affiliation: Jai Prakash Narayan Apex Trauma Centre, All India Institute of Medical Sciences, India. Electronic address: sharmagaurav850@gmail.com.
authors.forename: Gaurav
authors.initials: G
authors.lastname: Sharma
authors.affiliation: Apollo BGS Hospital, Mysore, Karnataka, India.
authors.forename: Kiran Kumar
authors.initials: KK
authors.lastname: Gn
authors.affiliation: GGS Medical College, Faridkot, India.
authors.forename: Kavin
authors.initials: K
authors.lastname: Khatri
authors.affiliation: Jai Prakash Narayan Apex Trauma Centre, All India Institute of Medical Sciences, India.
authors.forename: Ravijot
authors.initials: R
authors.lastname: Singh
authors.affiliation: Jai Prakash Narayan Apex Trauma Centre, All India Institute of Medical Sciences, India.
authors.forename: Shivanand
authors.initials: S
authors.lastname: Gamanagatti
authors.affiliation: Jai Prakash Narayan Apex Trauma Centre, All India Institute of Medical Sciences, India.
authors.forename: Vijay
authors.initials: V
authors.lastname: Sharma
mesh_terms: D000077:Acetabulum / Q000000981:diagnostic imaging* / Q000293:injuries / Q000601:surgery; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001863:Bone Screws; D005260:Female; D005264:Femoral Fractures / Q000000981:diagnostic imaging* / Q000601:surgery; D005593:Fracture Fixation, Internal / Q000295:instrumentation / Q000379:methods*; D006620:Hip Fractures / Q000000981:diagnostic imaging* / Q000601:surgery; D006801:Humans; D021621:Imaging, Three-Dimensional; D007194:India; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed; D014193:Trauma Centers; D016896:Treatment Outcome; D055815:Young Adult
keywords: CT scan; Intertrochanteric; Lateral wall; Pertrochanteric; Posteromedial fragment