title: Intraoperative navigation evaluation of tibial translation after resection of anterior cruciate ligament remnants.
abstract: OBJECTIVE
  This study aimed to assess knee laxity before and after resection of the anterior cruciate ligament (ACL) remnants, using a computer navigation system.
  
  
  METHODS
  This prospective study included 83 knees undergoing primary navigated ACL reconstruction. ACL remnants were classified into 4 morphologic types based on the arthroscopic findings: type 1, bridging between the posterior cruciate ligament and tibia; type 2, bridging between the roof of the intercondylar notch and tibia; type 3, bridging between the lateral wall of the intercondylar notch and tibia; and type 4, no substantial ACL remnants. Anterior tibial translation (ATT) and range of internal-external rotation of tibia (total rotation) at 15°, 30°, 45°, 60°, 75°, and 90° of knee flexion were measured before and after resection of the ACL remnants by use of the additional functions of the navigation system.
  
  
  RESULTS
  The different morphologic types of the ACL remnants were as follows: type 1, 12 knees; type 2, 16 knees; type 3, 51 knees; and type 4, 4 knees. There were no significant differences in the mean ATT before and after resection at any knee flexion angle in type 1, 2, or 4 knees. In type 3 knees the mean ATT at 15° of knee flexion before resection significantly increased after resection. There were no significant differences in the mean total rotation before and after resection at any knee flexion angle for each type. After resection of the ACL remnants, 12 knees (14.5%) in the type 3 showed an increased ATT by 3 mm or more.
  
  
  CONCLUSIONS
  This study suggests that the ACL remnant does not play a major role in stabilization of the knee. Although type 3 ACL remnants significantly decreased anterior knee laxity in the knee extension position, the knee stability provided by the ACL remnants was not adequate.
  
  
  METHODS
  Level II, prognostic study.
authors.affiliation: Department of Orthopaedic Surgery, Hirosaki University Graduate School of Medicine, Hirosaki, Japan. s-maeda@cc.hirosaki-u.ac.jp
authors.forename: Shugo
authors.initials: S
authors.lastname: Maeda
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Ishibashi
authors.forename: Eiichi
authors.initials: E
authors.lastname: Tsuda
authors.forename: Yuji
authors.initials: Y
authors.lastname: Yamamoto
authors.forename: Satoshi
authors.initials: S
authors.lastname: Toh
mesh_terms: D000293:Adolescent; D000328:Adult; D016118:Anterior Cruciate Ligament / Q000503:physiopathology* / Q000601:surgery; D000070598:Anterior Cruciate Ligament Injuries; D059549:Anterior Cruciate Ligament Reconstruction; D001182:Arthroscopy / Q000379:methods*; D001696:Biomechanical Phenomena; D002648:Child; D005260:Female; D006801:Humans; D007430:Intraoperative Care / Q000379:methods*; D007593:Joint Instability / Q000209:etiology / Q000503:physiopathology*; D008297:Male; D008592:Menisci, Tibial / Q000601:surgery; D008875:Middle Aged; D011183:Postoperative Complications / Q000209:etiology / Q000503:physiopathology; D011379:Prognosis; D011446:Prospective Studies; D016059:Range of Motion, Articular; D012399:Rotation; D025321:Surgery, Computer-Assisted / Q000295:instrumentation / Q000379:methods; D013977:Tibia / Q000473:pathology*; D000070600:Tibial Meniscus Injuries; D055815:Young Adult