title: Experimental loss of menisci, cartilage and subchondral bone gradually increases anteroposterior knee laxity.
abstract: OBJECTIVE
  Anteroposterior knee stability is a relevant factor for the decision-making process of various surgical procedures. In degenerative joints when the implantation of unicompartimental prostheses or corrective osteotomies of the limb are planned, the integrity of the anteroposterior stability with an intact ACL has been regarded as a necessary prerequisite. We hypothesise that joint degeneration, however, may influence the anteroposterior knee laxity. Therefore, we set out to test this hypothesis simulating a progressively 'degenerated' joint in an experimental cadaveric setting.
  
  
  METHODS
  Twelve intact transfemorally resected Thiel-fixated cadaver knee joints were divided into 2 groups for manipulation in the medial or lateral compartment. In each knee, we performed (1) unilateral total meniscectomy; (2) simulation of advanced osteoarthritis, by unilateral total cartilage debridement; (3) simulation of a unilateral tibial impression fracture, by resection of 5 mm of the tibial plateau; (4) transection of the ACL. The KT-1000 arthrometer was used to measure the extent of anteroposterior translation at 30° of knee flexion.
  
  
  RESULTS
  The mean value for tibial anteroposterior translation before intervention was 3.2 mm (SD: ± 0.8). The mean translation after each intervention was 4.6 mm (SD: ± 0.9; +44%; n.s.) after meniscectomy, 5.9 mm (SD: ± 1.5; +84%; P < 0.05) after cartilage debridement, 8 mm (SD: ± 1.5; +150%; P < 0.01) after bone debridement, and finally 9.7 mm (SD: ± 2.2; +203%; P < 0.05) after resection of the ACL. There were no significant differences between the medial and lateral compartment.
  
  
  CONCLUSIONS
  In absence of massive osteophytes or capsular shrinkage, rapid loss of meniscus, cartilage and particularly loss of subchondral bone may result in a massive increase in anteroposterior translation, mimicking a tear of the ACL. In such a situation, a false positive impression of a ligamentous injury may arise, and decision making is falsely directed away from totally or partially knee joint-preserving procedures. Therefore, in degenerate joints, clinical evaluation of anteroposterior stability should rather rely on the presence of a firm stop than an overall increased joint translation.
authors: Orthopedic Department, Balgrist University Hospital, University of Zurich, Zurich, Switzerland. karl.wieser@balgrist.ch
authors: Karl
authors: K
authors: Wieser
authors: Michael
authors: M
authors: Betz
authors: Mazda
authors: M
authors: Farshad
authors: Magdalena
authors: M
authors: Vich
authors: Sandro F
authors: SF
authors: Fucentese
authors: Dominik C
authors: DC
authors: Meyer
mesh_terms: D053587:Arthrometry, Articular; D001182:Arthroscopy; D002358:Cartilage, Articular / Q000293:injuries*; D006801:Humans; D066298:In Vitro Techniques; D007593:Joint Instability / Q000209:etiology*; D007718:Knee Injuries / Q000503:physiopathology*; D007719:Knee Joint / Q000503:physiopathology*; D008954:Models, Biological; D020370:Osteoarthritis, Knee / Q000503:physiopathology*; D013978:Tibial Fractures / Q000503:physiopathology*; D000070600:Tibial Meniscus Injuries