No differences in in vivo kinematics between six different types of knee prostheses

Purpose: The aim of this study was to compare a broad range of total knee prostheses with different design parameters to determine whether in vivo kinematics was consistently related to design. The hypothesis was that there are no clear recognizable differences in in vivo kinematics between different design parameters or prostheses. Methods: At two sites, data were collected by a single observer on 52 knees (49 subjects with rheumatoid arthritis or osteoarthritis). Six different total knee prostheses were used: multi-radius, single-radius, fixed-bearing, mobilebearing, posterior-stabilized, cruciate retaining and cruciate sacrificing. Knee kinematics was recorded using fluoroscopy as the patients performed a step-up motion. Results: There was a significant effect of prosthetic design on all outcome parameters; however, post hoc tests showed that the NexGen group was responsible for 80% of the significant values. The range of knee flexion was much smaller in this group, resulting in smaller anterior-posterior translations and rotations. Conclusion: Despite kinematics being generally consistent with the kinematics intended by their design, there were no clear recognizable differences in in vivo kinematics between different design parameters or prostheses. Hence, the differences in design parameters or prostheses are not distinct enough to have an effect on clinical outcome of patients.Biomechanical EngineeringMechanical, Maritime and Materials Engineerin

Adherence of hip and knee arthroplasty studies to RSA standardization guidelines

Peer reviewe

Precision assessment of model-based RSA for a total knee prosthesis in a biplanar set-up.

Model-based Roentgen stereophotogrammetric Analysis (RSA) was recently developed for the measurement of prosthesis micromotion. Its main advantage is that markers do not need to be attached to the as traditional marker-based RSA requires. Model-based RSA has only been tested in uniplanar radiographic set-ups. A biplanar set-up would theoretically facilitate the pose estimation algorithm, since radiographic projections would show more different shape features of the implants than in uniplanar images. We tested the precision of model-based RSA and compared it with that of the traditional marker-based method in a biplanar set-up. Micromotions of both tibial and femoral components were measured with both the techniques from double examinations of patients participating in a clinical Study. The results showed that in the biplanar Set-up model-based RSA presents a homogeneous distribution of precision for all the translation directions, but an inhomogenous error for rotations, especially internal-external rotation presented higher errors than rotations about the transverse and sagittal axes. Model-based RSA was less precise than the marker-based method, although the difference were not significant for the translations and rotations of the tibial component, with the exception of the internal-external rotations. For both prosthesis components the precisions of model-based RSA were below 0.2 mm for all the translations, and below 0.3 degrees for rotations about transverse and sagittal axes. These values are still acceptable for clinical studies aimed at evaluating total knee prosthesis micromotion. In a biplanar set-tip model-based RSA is a valid alternative to traditional marker-based RSA where marking of the prosthesis is an enormous disadvantage

Kinematics of the distal tibiofibular syndesmosis - Radiostereometry in 11 normal ankles

In 11 healthy volunteers, the normal kinematics of the tibiofibular syndesmosis of the ankle during weight bearing and external rotation stress were compared to a nonweight-bearing neutral position by radiostereometry. We found very small rotations and displacements in this "normal" group, which indicated that the fibula is closely attached to the tibia, thereby preventing larger movements at the level of the ankle. We found no common kinematic pattern during weight bearing in the neutral position. Application of a 7.5 Nm external rotation moment on the foot caused external rotation of the fibula between 2 and 5 degrees, medial translation between 0 and 2.5 mm and posterior displacement between 1.0 and 3.1 mm. These data can be used as normal reference values for studies of patients with suspected syndesmotic injuries

External rotation stress imaging in syndesmotic injuries of the ankle - Comparison of lateral radiography and radiostereometry in a cadaveric model

We compared the value of 7.5 Nm external rotation stress in diagnosing tibiofibular syndesmotic injuries of the ankle on lateral radiographs with radiostereometric analysis (RSA) in 10 cadaveric legs. After sectioning 2 ligaments, RSA showed an increase in posterior translation and external rotation of the fibula. This increase in posterior translation was smaller than the posterior displacement of the fibula on the lateral radiograph, and RSA showed mainly an increase in external rotation of the fibula that can not be measured on conventional radiographs. We conclude that instability of the syndesmosis in cadaveric ankles can be detected with 7.5 Nm external rotation stress RSA, but that external rotation stress lateral radiography is unreliable