title: Influence of number and orientation of screws on stability in the internal fixation of unstable femoral neck fractures.
abstract: OBJECTIVE
  The aim of this study was to biomechanically compare 3 different cannulated screw configurations used in internal fixation of unstable femoral neck fractures.
  
  
  METHODS
  The study included 28 synthetic left femurs randomly divided into 4 equal groups. Samples in the first 3 groups were osteotomized in the basicervical region to create Pauwels Type 3 fractures. Fixation was carried out using cannulated screws. In Group 1, four screws were used including 3 in an inverted triangle configuration in parallel with the neck and the fourth screw transversely into the calcar. In Group 2, three screws were used including 2 in parallel with the neck and the third transversely into the calcar. In Group 3, three screws were used in an inverted triangle configuration in parallel with the neck. No osteotomy or fixation was carried out in Group 4. Load test was performed on all the groups and the strength of the screw fixations against axial load and their amount of relocation were measured.
  
  
  RESULTS
  Average maximum strength was 36.1 ± 3.2 N/mm2 in Group 1, 27.3 ± 4.1 N/mm2 in Group 2 and 21.9 ± 3.2 N/mm2 in Group 3. The average relocation in the line of osteotomy in the moment of average maximum stress (21.9 ± 3.2 N/mm2) was 11.5 ± 2.1 mm in Group 3, 6 ± 1.3 mm in Group 2 and 5.8 ± 1.1 mm in Group 1 (p<0.05). It was also observed that while the relocation in the moment of average maximum stress (27.3 ± 4.1 N/mm2) was 9.1 ± 1.7 mm in Group 2, the deformation under the same stress value was 9 ± 1.7 mm in Group 1 (p>0.05).
  
  
  CONCLUSIONS
  The use of a transverse screw in the calcar in addition to cannulated screws parallel to the neck appear to provide stability benefit in the treatment of unstable femoral neck fractures.
authors: Department of Orthopedics and Traumatology, Adıyaman University Training and Research Hospital, Adıyaman, Turkey.
authors: Seyit Ali
authors: SA
authors: Gümüştaş
authors: Department of Orthopedics and Traumatology, Adıyaman University Training and Research Hospital, Adıyaman, Turkey.
authors: Hacı Bayram
authors: HB
authors: Tosun
authors: Department of Orthopedics and Traumatology, Adıyaman University Training and Research Hospital, Adıyaman, Turkey.
authors: İsmail
authors: İ
authors: Ağır
authors: Department of Orthopedics and Traumatology, Fatih Sultan Mehmet Training and Research Hospital, İstanbul, Turkey.
authors: Mehmet Müfit
authors: MM
authors: Orak
authors: Department of Orthopedics and Traumatology, Marmara University Training and Research Hospital, İstanbul, Turkey.
authors: Tolga
authors: T
authors: Onay
authors: Department of Orthopedics and Traumatology, Hafsa Sultan Hospital, Faculty of Medicine, Celal Bayar University, Manisa, Turkey.
authors: Güvenir
authors: G
authors: Okçu
mesh_terms: D000704:Analysis of Variance; D001696:Biomechanical Phenomena; D001863:Bone Screws; D019245:Compressive Strength / Q000502:physiology*; D005265:Femoral Neck Fractures / Q000601:surgery*; D005269:Femur / Q000601:surgery; D005593:Fracture Fixation, Internal / Q000295:instrumentation* / Q000379:methods; D006801:Humans; D007593:Joint Instability / Q000601:surgery*; D008953:Models, Anatomic; D012680:Sensitivity and Specificity; D016474:Weight-Bearing / Q000502:physiology