title: Side-to-side variation in normal femoral morphology: 3D CT analysis of 122 femurs.
abstract: BACKGROUND
  The contralateral femur is often used as reference for reconstruction in unilateral hip joint pathology. The objective of this study was to quantify the side-to-side variation in proximal femur. We hypothesized that significant side-to-side differences exist between left and right femur with implications for preoperative planning and leg length discrepancy following hip arthroplasty.
  
  
  METHODS
  CT-based 3D femoral models were reconstructed for 122 paired femurs in 61 young healthy subjects (46.9±6.8 years) with no history of hip pathology. Side-to-side differences of several femoral morphologic parameters, including femoral head diameter, femoral anteversion, horizontal offset and femoral head center location, were compared and correlated with demographic factors using multiple linear regression.
  
  
  RESULTS
  Significant side-to-side differences (P<0.01) were found in femoral anteversion (4.3±3.8°; range: 0.2° to 17.3°), horizontal offset (2.5±2.1mm; range: 0.1 to 10.3mm), and femoral head center location (7.1±3.8mm; range: 0.5 to 19.4mm). The difference in femoral anteversion was strongly correlated with the difference in neck diameter (R(2)=0.79), whereas the difference in horizontal femoral offset was highly correlated with the head diameter difference (R(2)=0.72). Femoral head center difference was correlated with the femoral anteversion, horizontal offset and neck-shaft-angle difference (R(2)=0.82).
  
  
  CONCLUSIONS
  Relying on the anatomic landmarks of the contralateral femur during hip arthroplasty may not necessarily result in restoration of native anatomy and leg-length. Knowledge of the baseline side-to-side asymmetry could provide a range of error that would be tolerable following hip reconstruction.
  
  
  METHODS
  Level IV.
  
  
  METHODS
  Retrospective observational study.
authors: Bioengineering laboratory, department of orthopaedic surgery, Massachusetts general hospital/Harvard medical school of Boston, 55, Fruit Street, GRJ 1215, Boston, Massachusetts MA 02114, USA.
authors: D
authors: D
authors: Dimitriou
authors: Bioengineering laboratory, department of orthopaedic surgery, Massachusetts general hospital/Harvard medical school of Boston, 55, Fruit Street, GRJ 1215, Boston, Massachusetts MA 02114, USA.
authors: T-Y
authors: TY
authors: Tsai
authors: Department of orthopedics, Ninth People's hospital, Shanghai Jiaotong university school of medicine, Shanghai, China.
authors: B
authors: B
authors: Yue
authors: Bioengineering laboratory, department of orthopaedic surgery, Massachusetts general hospital/Harvard medical school of Boston, 55, Fruit Street, GRJ 1215, Boston, Massachusetts MA 02114, USA.
authors: H E
authors: HE
authors: Rubash
authors: Bioengineering laboratory, department of orthopaedic surgery, Massachusetts general hospital/Harvard medical school of Boston, 55, Fruit Street, GRJ 1215, Boston, Massachusetts MA 02114, USA.
authors: Y-M
authors: YM
authors: Kwon
authors: Bioengineering laboratory, department of orthopaedic surgery, Massachusetts general hospital/Harvard medical school of Boston, 55, Fruit Street, GRJ 1215, Boston, Massachusetts MA 02114, USA. Electronic address: gli1@mgh.harvard.edu.
authors: G
authors: G
authors: Li
mesh_terms: D000328:Adult; D003198:Computer Simulation; D005260:Female; D005269:Femur / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D064368:Healthy Volunteers; D006621:Hip Joint / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D006801:Humans; D008297:Male; D008875:Middle Aged; D061330:Multidetector Computed Tomography; D012189:Retrospective Studies; D036542:Tomography, Spiral Computed; D014057:Tomography, X-Ray Computed
keywords: Anteversion; Asymmetry; Geommetric morphometrics; Hip joint center; Offset; Proximal femur; Total hip arthroplasty