Fig 1.
Biomechanical ex vivo sheep model of 3D joint mobility.
The distal portion of the gastrocnemius and its tendon are tightened by a Colson ring (A). A metallic wire (B) is connected, via a pulley (C), to a metallic bar to which weight plates are loaded (D). The stereo-photogrammetric system (Optitrack) is composed of 10 cameras and 2 optical references frames (rigidly attached to the tibia and the femur) to record and measure the kinematics of a knee joint (E).
Fig 2.
Analytical set-up of the ex-vivo biomechanical study.
The experimenter pulled the wire manually (passive test) to check the dispositive. Then the quadriceps was loaded with an initial weight of 0.5 kg and the motion of 3 flexion-extension cycles of the leg was recorded with increasing weight for up to 5 kg by 0.5 kg increment. Test item A = Hylan G-F 20 and test item B = KiOmedine® CM- chitosan.
Fig 3.
Procedure of creation of cartilage default.
(1) The distal and cutting part was sawed from a biopsy punch (B). (2) After incision of the subcutis and joint capsule, the medial condyle (C) of the femur was exposed. Fat (F) was removed from the joint cavity. (3) The biopsy punch (B) was deeply entered into three adjacent sites of cartilage in the axial aspect of the medial condyle of the femur. The Volkman curette (V) was used to remove cartilage. Then the joint capsule was sutured and tests were performed. (4) Picture 4 illustrates the three cartilage defects on the medial condyle (MC) at gross anatomy dissection. LC = lateral condyle.
Fig 4.
Schematic representation of force involved during the ex-vivo model.
Calculations were performed, with the assumption that the ovine hindlimb is a 2D hinge joint that is rotating around the O point, due to the quadriceps force (F), involving the following parameters:
- F = quadriceps force (in the experimental analysis obtained as the force of the weight);
- Fx = component of the force F along the direction X
- Fy = component of the force F along the direction Y
- m = mass of the limb;
- mg = weight of the limb (g is the gravity, 9.81 m/s2);
- F* = the contact force between the tibia and the femur;
- f = friction coefficient (or COF);
- fF* = the friction force;
- r = radius of the femoral condyle;
- a = distance between the tibial insertion point of the patellar tendon and the hinge centre;
- b = distance between the barycentre of the lower leg and the hinge centre;
- α (alpha) = flexion angle;
= the second derivative (angular acceleration) of α with respect to the time
- I0 = the mass moment of inertia
- β (beta) = angle from the patellar tendon and the tibial axis
Fig 5.
COF measurements of KiOmedine® in the p-HEMA tribological model.
The lubrication capacity of KiOmedine® (N = 4) to reduce COF between the disks in rotating friction was compared to two commercial VSs biomaterial references composed of crosslinked hyaluronic acid, Hylan G-F 20 (N = 4) and NASHA(N = 3), the buffer control (N = 4) and synovial fluids punctured from osteoarthritic patients (N = 10). KiOmedine® exhibited similar or higher lubricating capacity compared to Hylan G-F 20 and NASHA (ANOVA, ***p < 0.0001).
Fig 6.
Lubrication capacity of KiOmedine® CM-chitosan in the biomechanical ex-vivo sheep model of 3D joint mobility.
(A) A significant increase in COF is observed due to increased joint friction in damaged cartilage (paired T-test, **p<0.01); COF is then progressively significantly improved following the IA injection with KiOmedine® CM-chitosan in a volume-dependent manner (ANOVA, **p<0.01). (B) KiOmedine® CM-chitosan was compared to Hylan G-F 20 at 3 ml IA volume and showed significantly better recovery of joint motion loss on damaged cartilage (t-test, **p<0.01); the effect of the polymer-free buffer of KiOmedine® on the recovery of motion was low.
Fig 7.
Free radical scavenging capacity using the TEAC assay.
KiOmedine® CM-chitosan was compared to Hylan G-F 20, NASHA, negative and positive controls respectively, the polymer-free buffer of KiOmedine® CM-chitosan and vitamin C. KiOmedine® CM-chitosan showed high free radical scavenging capacity in vitro as compared to crosslinked HA biomaterials, Hylan G-F 20, and NASHA (ANOVA, ***p<0.0001).