title: The reversed gap technique produces anatomical alignment with less midflexion instability in total knee arthroplasty: a prospective randomized trial.
abstract: OBJECTIVE
  No surgical technique is capable of controlling the stability of the joint in midflexion. The purpose of the present study was to present and evaluate a surgical technique that aims to reduce the need for soft-tissue release and optimize stability in midflexion.
  
  
  METHODS
  Sixty knee joints were included in this prospective randomized study. Surgery was performed either according to a classical gap (GT) technique or using the reversed gap (RG) technique. In the RG, the femoral component was positioned parallel to the surgical transepicondylar axis using a preoperative MRI and a navigation system. The frontal alignment of the tibia was then selected to produce a symmetric flexion gap. Then, the frontal alignment of the femoral component was adjusted to produce a symmetric extension gap. Soft-tissue release was defined to be extensive if more than two steps or stabilizing structures were involved. Joint stability was measured at different flexion angles (-5° to 120°) using a gap tensioning device and the trial femoral implant.
  
  
  RESULTS
  In the GT group, 16 knee joints (53 %) showed an instability of more than 2 mm at 5°, 30° or 60°, compared with 8 knee joints (27 %) in the RG group (p = 0.035). The RG did not lead to a reduction in the number of soft-tissue releases, but they were less extensive.
  
  
  CONCLUSIONS
  RG reduced midflexion instability and the number of extensive soft-tissue releases. It may simplify the operation by reducing the extent of soft-tissue releases and avoid instability-related problems of knee arthroplasty. Nevertheless, it should only be performed under controlled conditions until long-term clinical data are available.
  
  
  METHODS
  I.
authors.affiliation: Orthopaedic Department, Friedrich-Schiller University Jena, Campus Eisenberg, Klosterlausnitzer Straße 81, 07607, Eisenberg, Germany. g.matziolis@krankenhaus-eisenberg.de.
authors.forename: Georg
authors.initials: G
authors.lastname: Matziolis
authors.affiliation: Orthopaedic Department, Friedrich-Schiller University Jena, Campus Eisenberg, Klosterlausnitzer Straße 81, 07607, Eisenberg, Germany.
authors.forename: Steffen
authors.initials: S
authors.lastname: Brodt
authors.affiliation: Orthopaedic Department, Friedrich-Schiller University Jena, Campus Eisenberg, Klosterlausnitzer Straße 81, 07607, Eisenberg, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Windisch
authors.affiliation: Orthopaedic Department, Friedrich-Schiller University Jena, Campus Eisenberg, Klosterlausnitzer Straße 81, 07607, Eisenberg, Germany.
authors.forename: Eric
authors.initials: E
authors.lastname: Roehner
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D017760:Bone Malalignment / Q000517:prevention & control*; D005260:Female; D005269:Femur / Q000601:surgery; D006801:Humans; D007719:Knee Joint / Q000601:surgery; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000601:surgery; D011446:Prospective Studies; D016059:Range of Motion, Articular; D013977:Tibia / Q000601:surgery
keywords: Anatomical alignment; Gap technique; Midflexion instability; Total knee arthroplasty