Muscle loaded stability reflects ligament-based stability in TKA: a cadaveric study

Abstract

Purpose This paper aims at evaluating the effects of muscle load on knee kinematics and stability after TKA and second at evaluating the effect of TKA surgery on knee kinematics and stability; and third, at correlating the stability in passive conditions and the stability in active, muscle loaded conditions. Methods Fourteen fresh frozen cadaveric knee specimens were tested under passive and active condition with and without external loads involving a varus/valgus and internal/external rotational torque before and after TKA surgery using two inhouse developed and previously validated test setups. Results Introduction of muscle force resulted in increased valgus (0.98°) and internal rotation of the femur (4.64°). TKA surgery also affected the neutral path kinematics, resulting in more varus (1.25°) and external rotation of the femur (5.22°). All laxities were significantly reduced by the introduction of the muscle load and after implantation of the TKA. The presence of the implant significantly affects the active varus/valgus laxity. This contrasts with the rotational laxity, in which case the passive laxity is the main determinant for the active laxity. For the varus/valgus laxity, the passive laxity is also a significant predictor of the active laxity. Conclusion Knee stability is clearly affected by the presence of muscle load. This points to the relevance of appropriate rehabilitation with focus on avoiding muscular atrophy. At the same time, the functional, muscle loaded stability strongly relates to the passive, ligament-based stability. It remains therefore important to assess knee stability at the time of surgery, since the passive laxity is the only predictor for functional stability in the operating theatre. Level of evidence Case series, Level IV.

Modified Lemaire tenodesis reduces anterior cruciate ligament graft forces during internal tibial torque loading

“…There was no muscle induced stabilisation or iliotibial band loading during the static investigations which resulted in high tibial translational and rotational values. As ligament-based stability strongly relates to muscle loaded stability and is a reliable predictor for functional stability [ 43 ], it was chosen to not load any muscle in order to limit influencing factors and analyse the true ligamentous behaviour. In addition, care needs to be taken in transferring the results to all anterolateral procedures, as they vary in the position of the femoral graft or take a different treatment approach in the case of an ALLR.…”

Knee kinematics during staircase descent

“…To assure the correct anatomical position of the bones in the test setup, dedicated guides were designed and printed based on the preoperative CT scan. 17 The foot of the specimen was inserted in an ankle holder which allowed for internal/external loads and varus/valgus loads in the knee joint as defined in Table I , similar to Arnout et al 18 A varus/valgus load is applied on the knee joint by adding a constant weight on the medial or lateral side of the fixed ankle. Similarly, internal/external loads are applied by providing a fixed torque on the ankle holder.…”

Effect of iliotibial band and gastrocnemius activation on knee kinematics

“…The foot of the specimen was inserted in an ankle-foot holder which allowed for a natural force direction of the gastrocnemius. The ankle-foot holder was designed to allow external varus/valgus load of 6.5 Nm constantly through the range of motion of the squat to test the knee stability under external loads, similar to the method used in Arnout et al [11].…”

“…A squat motion was simulated in the UGKR by keeping the hamstring forces constant while varying the quadriceps forces in accordance with a sinusoidal 75 pattern based on numerical simulation software AnyBody, similar to the procedure in Arnout et al [11]. By approximation, this resulted in a constant vertical ground reaction force, traditionally considered in Oxford test set-ups [12].…”

“…The three translations were independently calculated for both the medial and lateral compartments of the knee. The knee kinematics were assessed in real time to a 1.0 mm/1.2°of accuracy [11].…”