title: Is the lag screw sliding effective in the intramedullary nailing in A1 and A2 AO-OTA intertrochanteric fractures? A prospective study of Sliding and None-sliding lag screw in Gamma-III nail.
abstract: OBJECTIVE
  To compare the Sliding with Non-sliding lag screw of a gamma nail in the treatment of A1 and A2 AO-OTA intertrochanteric fractures.
  
  
  METHODS
  80 patients were prospectively collected. In each group, AO/OTA 31-A were classified into group A. AO/OTA 31-A2.1 was classified as group B. We classified the A2.2 and A2.3 as group C. According to the set-screw locking formation of Gamma-III, the cases were randomly allocated to Sliding subgroup and Non-sliding subgroup in A, B and C groups. Follow-ups were performed 1, 3, 6 and 12 months postoperatively.
  
  
  RESULTS
  In the Sliding group, the bone healing rate 3, 6, 12 months postoperatively reached 85.00%, 97.50%, 100% in group A, B and C. Meanwhile, in Non-sliding group, postoperatively, bone healing rate were 90.00%, 95.00% and 97.50% in group A, B and C, respectively. Both differences were not significant. Lower limb discrepancy between Sliding and Non-sliding pattern was significantly different in group C which represent fracture types of AO/OTA 31-A2.2 and A2.3 (0.573 ± 0.019 mm in Non-sliding group, 0.955 mm ± 0.024 mm in Sliding group, P < 0.001 ). Difference of sliding distance among the three groups was significant among group A, B and C: 0.48 mm ± 0.04 mm, 0.62 mm ± 0.07 mm and 0.92 mm ± 0.04 mm (P < 0.001). Differences in average healing time and Harris scores also presented no significance in the three groups.
  
  
  CONCLUSIONS
  As a result, we can conclude that the sliding distance is minimal in Gamma nails and it is related to the comminuted extent of the intertrochanteric area in A1 and A2 AO-OTA intertrochanteric fractures. For treating these kinds of fractures, the sliding of the lag screw of an Gamma nail does not improve any clinical results and in certain cases, such as highly comminuted A1 and A2 fractures, can therefore even benefit from a locked lag screw by tightening the set-screw.
authors.affiliation: Department of Orthopaedics, Shanghai Sixth People's Hospital, Shanghai Jiaotong University, No,600, YiShan Road, Xuhui District, Shanghai, 200233, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhu
authors.forename: Severin
authors.initials: S
authors.lastname: Meili
authors.forename: Changqing
authors.initials: C
authors.lastname: Zhang
authors.forename: Congfeng
authors.initials: C
authors.lastname: Luo
authors.forename: Bing-fang
authors.initials: BF
authors.lastname: Zeng
mesh_terms: D001858:Bone Nails; D001863:Bone Screws; D016009:Chi-Square Distribution; D002681:China; D005594:Fracture Fixation, Intramedullary / Q000295:instrumentation* / Q000379:methods*; D006620:Hip Fractures / Q000145:classification / Q000601:surgery*; D006801:Humans; D017063:Outcome Assessment, Health Care; D011446:Prospective Studies; D018709:Statistics, Nonparametric