title: The isometry of two different paths for remnant-preserving posterior cruciate ligament reconstruction.
abstract: OBJECTIVE
  It is reported that the length of the posterior cruciate ligament (PCL) fibres increases as the knee flexes, and the magnitude of the length change reaches up to 9.8 mm throughout the range of motion, which exceeds the range of failure strain. Therefore, we postulated that a compensatory mechanism must be recruited to overcome this large strain in order to maintain physiologic function as a key component of joint kinematics. Our main objective was to compare the length change pattern for the linear distance between the femoral and tibial tunnels with the length change patterns derived from a real isometer test of different curvatures.
  
  
  METHODS
  We utilized ten intact cadaveric knees and created a vertical femoral tunnel (5 mm medial to the roof of the intercondylar notch and 5 mm proximal from the articular margin) and lateral tibial tunnels (5 mm proximal to the posterior bony ridge on the lateral side of the PCL fibre) and performed a 3D-CT scan at 0º, 30º, 60º, 90º, and 120º. The distances between the femoral and tibial tunnels were calculated from the 3D coordinates. Real isometry was checked both (1) over the PCL and (2) under the PCL using an isometer with an accuracy of 0.1 mm.
  
  
  RESULTS
  The path over the PCL had the longest intra-articular length, followed by the path under the PCL, and the lengths measured by CT, respectively. The path over the PCL had a more curved path compared with the path under the PCL and the lengths measured by CT. The lengths measured by CT showed significantly larger excursion than the real isometer test. The path over the PCL showed the least excursion through the range of motion, followed by the path under the PCL, and the lengths measured by CT, respectively.
  
  
  CONCLUSIONS
  Our findings suggested that a more curved PCL path has better isometry because the curvature of the PCL compensates for the length change between 0º and 60º flexion. In remnant preservation PCL reconstruction, the passage of graft over the PCL would have increased intra-articular length and better isometry compared with straight under the PCL path.
  
  
  METHODS
  Basic science study.
authors: Department of Orthopedic Surgery, College of Medicine, Chung-Ang University, Seoul, Korea.
authors: Ho-Joong
authors: HJ
authors: Jung
authors: Jin Hong
authors: JH
authors: Kim
authors: Han Jun
authors: HJ
authors: Lee
authors: Seungbum
authors: S
authors: Koo
authors: Seung-Hwan
authors: SH
authors: Chang
authors: Young Bok
authors: YB
authors: Jung
authors: Sang Hak
authors: SH
authors: Lee
mesh_terms: D000368:Aged; D001696:Biomechanical Phenomena; D002102:Cadaver; D005269:Femur / Q000000981:diagnostic imaging / Q000601:surgery; D006801:Humans; D021621:Imaging, Three-Dimensional; D007719:Knee Joint / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000601:surgery; D008875:Middle Aged; D016119:Posterior Cruciate Ligament / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000601:surgery; D016059:Range of Motion, Articular; D019651:Plastic Surgery Procedures; D013977:Tibia / Q000000981:diagnostic imaging / Q000601:surgery; D014057:Tomography, X-Ray Computed