Knee Kinematics in Biomechanics

May 15, 2018 Studying Tips

Kinematic assay of knee joints alludes to the designation of tibiofemoral bonds conduct due to the feasible spans of motion for knee joint arrangements. This form of inquisition principally demands accurate estimation of the movement of part bones in the knee joint and helps to understand physiological and injured joint paths, which ensure the efficient exploitation of rehabilitation joint components.

Anatomical and Tracking Markers in Defining Knee Kinematics

Knee joint kinematics is a complex system which includes trajectories of flexion, extension as well as internal and external rotation (Bonnin 2012).

The use of anatomical markers provides implant performance and implant bearing under the Roentgen Stereo Analysis. This ingress involves implanting tantalum landmarks in the osseous tissue and then capturing roentgenogram. Radiogram is performed through the joint region in two different slopes with a purpose to estimate the three-dimensional movement volume (Weidow 2006).

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The computer tomography dissection provides a detailed static image of the structural bones in the knee articulation showing the placement of the positioned implants in the tibia and femoral bones (Catani 2013). The knowledge of axis and coordinates of the beads allows determining the precise site of the component bones in the knee joint.

Researchers found out the movement segments of the body using surface markers. Appropriate gesture information is transmuted from skeletal movements using basic canons of analytical geometry and planimetry. Relative scorer shapes and coordinates the cluster on the skin placement which depicts the vector of knee junction. Video tracing is based on the use of a number of synchronistic registrators placed over the researched area (Catani 2013). The person has repulsive spheres fastened to the skin at operational points. Using cameras registering the sites of each marker from separate perusal corner, the siting of the notes in the video sequence from each of the cameras can be used to admeasure the 3D locus of each notch on the skin.

Therefore, anatomical markers can show a real picture and trajectories of relevant bone movements by implanting nodes in the bone tissues; on the other hand, tracking markers are placed on the skin but not implanted in inner tissues.

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Inaccuracies and Assumptions of the Motion Analysis Technique

While the accuracy of anatomical markers is regarded to be permissible, there are some principal hindrances of the method. First of all, the process can only be the assumption for the post-operative conditions of synthetic knee prostheses due to placing tantalum implants into the bone during knee substitution operations (Schreiber 1998). The exposure to the X-rays during the procedure of computer tomography has an associated risk of initiating mutation of cells that leads to cancer. The x-ray images of the knee articulation seized while a person is positioned horizontally, so the analysis of tomography results does not permit registration of the knee joint so that the patient carries out his/her usual practice (Ramsey 1999).

Visual tracking allows sub-millimeter kinematic investigation using skin assembled scorekeepers and is very prompt for tracking numerous objects. However, the key impediment of this procedure is that the markers on the skin can move independently from the basal bone structures due to the pliability of the friable muscle strip between the hard bone structure and moving skin-fixed indicator (Gushue 2005). This irrespective motion causes soft tissue artifacts and inaccuracies. Imprecisions in kinematic records due to skin shift artifact are intrinsic with motion analysis.

The joint kinematics quantified in three dimensional vision is a better source of information to comprehend the interactions between knee joint components. During flexion, the two main bones in a knee joint, the tibia and femur, rotate around several specific axes in differently positioned planes. This type of motion requires that the joint kinematics should be evaluated through computer tomography based on the same principal. There are several kinematic analysis techniques whose workability differs in terms of invasiveness, diapason of movement rectification, exactness, and ease of use (Masum et al. 2014).

The Biomechanical Features of the Knee for Osteoarthritic and Post Total Knee Replacement

The physiological movements of the knee have been registered and extensively characterized using the goniometry kinematic data gathered from gait analysis involving anatomical or tracing skin markers. As Scuderi 2010 reported, “Inert domain of stir in the knee articulation has been narrated to be from 162° in condition of full extension to 42° in features of full flexion”. Allen and Mann (2012) stated that “during physiological walking, the femorotibial angle turnes from 155° at paw-strike to 135° at the end of the stance phase and 90° in the mid-swing phase; at the trot, the total sagittal plane angular excursion is around 60-75°.” Spins in uninjured knee are accounted to range from 8° of external rotation to 5° of internal rotation during the swing stage and from 2° of external rotation to 2° of internal rotation during the stance milestone (Weidow 2006).

Angular disfigurements of the knee lead to varus and valgus deformities and flexion contractures during osteoarthritis. Varus malformations cause overwhelment of the medial knee compartment. From the biomechanical point of view, the knee articulation is comparatively outstretched in the sagittal plane, adducted in the frontal plane, and outwardly rotated in the transverse plane (Alfonso 2011). Adversely, valgus deformities overburden the lateral knee compartment. Biomechanically, the knee undertakes a site of flexion in the sagittal plane, abduction in the frontal plane, and internal rotation in the transverse plane (Bashaw & Tingstad n.d.). Some researches illustrate that less serious injured man with osteoarthritis of knee joint walks with lower peak adduction moments compared to healthy subjects (Henriksen et al. n.d.). Hard-injured sick man with osteoarthritis of a knee joint behaves with larger edge adduction moments than less severe patients or viable persons (Scott 2012). The comparatively sumptuous adduction moments in difficult patients compared with less severe patients could be summoned by divergences in mechanical axis interrelation, which corresponds to both examined disease severity and adduction moments (Weidow 2006).

The structure of the contemporary total knee replacement implants is designed with the aim of restorating physiological movements at the knee articulation, chiefly flexion-extension and internal-external rotation. The implants should also be resistant to varus-valgus angulation and cranial-caudal translation.

Spike knee adduction angle during pacing diminishes to 37% (in 6 months), but rises to 53% during preoperative stages ayear after TKR treatment. At 1-year propulsive phase, knee adduction moment and impulse usually reduce (64% and 78% of preoperative levels, accordingly) (Cassidy 2009). In the conventional curves of adduction moment for the preoperative period, 6-month and 1-year computations after endoprotheses placement into knee joint, peak braking moment forgathered at nearly 30% of the stance phase, whereas peak propulsive moment strikes at approximately 65 – 70% of the stance phase (Scott 2012).

Some investigation found out the long-term effects of total knee replacement on the biomechanics stating that most patients still evict insolvent step samplers that are similar to their gait patterns preoperatively. In the frontal plane, examiners state that adduction moment is ameliorated 6 months after surgery, but protractedly retrogresses back to higher preoperative levels after 1 year (Jones 2004).

In the transversal plane, changes occur when intramedullary insert point positioned to lateral or medial hole during the surgery of total knee replacement. A more valgus distal femoral cut can be made if the entry hole is too lateral, while a more varus distal femoral cut can be made if the hole is too medial (Pickering & Armstrong 2012).

Analysis of Appendix 1

In accordance with Appendix 1, it could be suggested that indicators meet physiological standards in patient B. The patient C is diagnosed with osteoarthritis; accordingly, patient A has a knee implant after total knee replacement. Such a proposition is proved by graphs of patient B that correspond to the norm. Therefore, the schedule of knee flexion for patient B corresponds to the physiological parameters and the schedule of patient C complies with those with osteoarthritis. Patients with osteoarthritis of knee junction had a significantly lower knee flexion (nearly 10.3°) while a healthy human should have nearly 18.0° (Alfonso 2011). Patient C with osteoarthritis of knee articulation also had significant lower knee flexion of 54.8°±5.5°. Patient A has apparently endoimplant of knee joint in the form of rotary prosthesis. It simulates the natural movement of the knee hinge with rotational moves. It allows increasing the degree of rotation of the lower leg outwards or inwards in flexion. This ensures a natural gait and secure management of the joint during movements. Prosthesis is fixed to the femur and tibia by means of femoral stems. This assertion is substantiated by the following indicator: kinematics of the knee joint goes beyond the norm and acquires negative values (flexion, abduction, rotation, etc.).

Conclusion

In conclusion, on the basis of this brief excursion into biomechanics, it is possible to imagine the complexity of the knee joint as a biomechanical system. Basic knowledge of the biomechanics of the knee joint is necessary for the correct formulation of the indications for reconstructive operations, adequate prosthesis implantation, and proper conduct of the rehabilitation program after surgery.

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