title: A critical analysis of the eccentric starting point for trochanteric intramedullary femoral nailing.
abstract: OBJECTIVE
  Antegrade femoral intramedullary nailing through a greater trochanteric insertion site has been proposed for the treatment of subtrochanteric fractures. The currently available trochanteric nails have dissimilar characteristics, and the most appropriate insertion site for satisfactory subtrochanteric fracture alignment has not been determined. This study is an analysis of 5 different trochanteric femoral nails and 3 different insertion sites using a cadaveric model of a reverse obliquity subtrochanteric femur fracture to determine the optimal trochanteric entry site.
  
  
  METHODS
  OSHA-approved cadaveric laboratory with an OEC 9800 (General Electric Company, Fairfield, CT) fluoroscopic C-arm.
  
  
  METHODS
  Twenty-one embalmed human cadaveric femurs were stripped of soft tissues. Three different starting points on the anteroposterior radiograph were used: at the tip of the greater trochanter, and 2 to 3 mm medial and lateral to the tip. A reverse obliquity subtrochanteric fracture was created. The Trochanteric Antegrade Nail (TAN), Gamma nail (2nd and 3rd generations), Trochanteric Fixation Nail (TFN), and the Holland Nail were then inserted. The proximal bend and radius of curvature were calculated for each nail. Varus and valgus angulation as well as lateral gapping were measured on radiographs; also calculated were the mean, range, and standard deviation. Statistical analysis was performed on angulation and gapping at the fracture site by using Fisher least significant differences analysis, based on a 2-way ANOVA test.
  
  
  RESULTS
  The Holland nail had a proximal bend of 10 degrees and a radius of 300 cm. TAN was 5 degrees and 350 cm, TFN was 6 degrees and 150 cm, Gamma 2 was 4 degrees and 300 cm, and Gamma 3 was 4 degrees and 200 cm. The tip starting point led to the most neutral alignment regardless of nail. The lateral starting point led to varus with all nails. The medial starting point led to valgus of >6 degrees with the Holland and TFN; Gamma and TAN had better alignment with <4 degrees of valgus. Gapping of the lateral cortex was greatest with a lateral starting point.
  
  
  CONCLUSIONS
  An analysis of 5 trochanteric intramedullary nails with different proximal bends and 3 different starting points in the greater trochanter showed that the tip of the trochanter is close to the "universal" starting point. In this cadaveric subtrochanteric fracture model, the tip starting point led to the most neutral alignment regardless of nail used. The lateral starting point led to varus and gapping of the lateral cortex with all nails.
  
  
  CONCLUSIONS
  Subtrochanteric fractures treated with a trochanteric antegrade nail should have an acceptable reduction before nail insertion. The tip of the trochanter, or even slightly medial, on anteroposterior fluoroscopy is recommended as the universal starting point for these nails. However, slight deviations from this point and nail geometry can cause fracture site malalignment. A lateral starting point led to varus alignment and should be avoided.
authors.affiliation: Cooper University Hospital, Camden, NJ 08103, USA. ostrum-robert@cooperhealth.edu
authors.forename: Robert F
authors.initials: RF
authors.lastname: Ostrum
authors.forename: Andrew
authors.initials: A
authors.lastname: Marcantonio
authors.forename: Robert
authors.initials: R
authors.lastname: Marburger
mesh_terms: D001858:Bone Nails; D002102:Cadaver; D019544:Equipment Failure Analysis; D005264:Femoral Fractures / Q000000981:diagnostic imaging* / Q000601:surgery*; D005269:Femur / Q000601:surgery*; D005594:Fracture Fixation, Intramedullary / Q000295:instrumentation* / Q000379:methods*; D006801:Humans; D066298:In Vitro Techniques; D019919:Prosthesis Implantation / Q000379:methods*; D011859:Radiography