Ex vivo biomechanical evaluation of the XXXX cranial cruciate ligament-deficient stifle with varying angles of stifle joint flexion and axial loads after tibial tuberosity advancement.

@entity235 @entity865 @entity942
OBJECTIVE: To evaluate the effect of tibial tuberosity advancement (TTA) on cranial tibial thrust (CrTT), retropatellar force (RPF), patellar tendon load (PTL), and patellar tendon angle determined by the tibial plateau angle ( @entity865 ( @entity865 ) ) method or common tangent ( @entity865 (CT) ) method in the @entity235 cranial cruciate ligament (CrCL)-deficient stifle joint. STUDY DESIGN: Ex vivo cadaver study. SAMPLE POPULATION: Cadaveric @entity235 hind limbs (n=30). METHODS: Stifle joints were subjected to 3 differing loading conditions using a constrained limb press model (Group 1: 30% body weight axial load at stifle and talocrural joint angles of 135    5   and 145    5  , respectively; Group 2: 30% body weight axial load at stifle and talocrural angles of 145    5   and 135    5  , respectively; and Group 3: 50% body weight axial load at stifle and talocrural joint angles of 135    5   and 145    5  , respectively). The CrCL was transected in situ under load; sensors allowed direct measurement of CrTT, RPF, and PTL. Lateral radiographic projections were used to assess @entity865 ( @entity865 ) and @entity865 (CT) . Descriptive statistics were used to report CrTT (by design this force returned to 0-point values, defined as the neutral point of advancement [NPA]). At the NPA, RPF was compared with baseline using a 2-tailed sign test. PTL within groups were compared using a paired t-test; pair-wise comparisons of @entity865 ( @entity865 ) and @entity865 (CT) were performed using a paired t-test. Comparisons between loading conditions were made with a 1-way ANOVA and Tukey's post hoc test. Equivalence tests were used to test mean @entity865 ( @entity865 ) and @entity865 (CT) for equivalence to 90  . Significance was set at a P-value of .05. RESULTS: CrTT returned to baseline values, and RPF and PTL at NPA were reduced below baseline values in all specimens in a near linear fashion with TTA. At the NPA, @entity865 ( @entity865 ) > @entity865 (CT) in 2 of the 3 loading conditions, but insufficient evidence to suggest they differed in the third. Mean @entity865 ( @entity865 ) and @entity865 (CT) varied between loading conditions. The threshold for each of the groups evaluated, at which the @entity865 could be significantly different from 90  , was larger for @entity865 ( @entity865 ) than @entity865 (CT) in all groups, as greater variation was observed with @entity865 ( @entity865 ) versus @entity865 (CT) . CONCLUSION: This study further supports the claim that reduction of CrTT occurs after TTA in the @entity942 stifle joint through an alteration of @entity865 . Additionally, RPF and PTL also decrease after TTA. The @entity865 (CT) may be a more precise method of determining @entity865 .
