title: Improved divergence angles with femoral interference screw placement through the tibial tunnel as measured by multiplanar reconstruction computed tomography.
abstract: OBJECTIVE
  A modified technique for anterior cruciate ligament (ACL) reconstruction without graft injury by femoral interference screw insertion directly through the tibial tunnel is reported. This study evaluated femur bioabsorbable interference screw divergence and obliquity of the graft and tunnel positions as measured by multiplanar reconstruction computed tomography (MPR-CT) after endoscopic ACL reconstruction.
  
  
  METHODS
  Twenty-five patients who underwent single-incision arthroscopically assisted ACL reconstruction using hamstring tendon autografts were enrolled in this prospective study. All procedures were performed using the same technique: femoral bioabsorbable interference screw insertion directly through the tibial tunnel. Divergence angles of oblique sagittal and oblique axial views of the graft and tunnel positions using MPR-CT evaluation were obtained. CT images were evaluated in a blinded manner by 3 experienced radiologists.
  
  
  RESULTS
  The average divergence angles in oblique sagittal and oblique axial views were 0.88 +/- 1.06 and 1.44 +/- 1.17, respectively. Sagittal, axial, and coronal obliquity of the graft in reconstructed patients averaged 64 degrees (range, 46 degrees to 69 degrees ), 19 degrees (range, 17 degrees to 22.5 degrees ), and 73.6 degrees (range, 70 degrees to 77.6 degrees ), respectively. Radiologic analysis of the femoral insertion according to the quadrant technique showed that the femoral center of the anteromedial (grafted) bundle was 18.6% and 23.6% of the depth of Blumensaat's line and the height of the femoral condyle. At the tibia, the tibial ACL attachment at the center of the anteromedial bundle was at 41.1% of the maximal tibial diameter.
  
  
  CONCLUSIONS
  Our study showed that MPR-CT is a useful diagnostic tool for evaluation of the femoral interference screw divergence, obliquity of the graft, and the exact femoral and tibial insertion site of the graft. The screw will have little or no divergence using this novel technique as measured by the very accurate MPR-CT.
  
  
  METHODS
  Level IV, therapeutic case series.
authors.affiliation: Division of Sports Medicine, Department of Orthopaedic Surgery, Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Taoyuan, Taiwan, Republic of China. chan512@adm.cgmh.org.tw
authors.forename: Yi-Sheng
authors.initials: YS
authors.lastname: Chan
authors.forename: Yang-Pin
authors.initials: YP
authors.lastname: Lo
authors.forename: Li-Chang
authors.initials: LC
authors.lastname: Lien
authors.forename: Chen-Ju
authors.initials: CJ
authors.lastname: Fu
authors.forename: Yung-Liang
authors.initials: YL
authors.lastname: Wan
authors.forename: Kuo-Yao
authors.initials: KY
authors.lastname: Hsu
authors.forename: Ching-Jen
authors.initials: CJ
authors.lastname: Wang
authors.forename: Wen-Jer
authors.initials: WJ
authors.lastname: Chen
mesh_terms: D000328:Adult; D016118:Anterior Cruciate Ligament / Q000601:surgery*; D000070598:Anterior Cruciate Ligament Injuries; D001182:Arthroscopy / Q000379:methods; D001863:Bone Screws; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging / Q000601:surgery*; D005500:Follow-Up Studies; D006801:Humans; D007718:Knee Injuries / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D008297:Male; D011446:Prospective Studies; D016059:Range of Motion, Articular / Q000502:physiology; D019651:Plastic Surgery Procedures / Q000379:methods*; D012421:Rupture; D013977:Tibia / Q000000981:diagnostic imaging / Q000601:surgery*; D014057:Tomography, X-Ray Computed / Q000379:methods*; D016896:Treatment Outcome; D055815:Young Adult