Johan Uvehammer

In vivo kinematics of total knee arthroplasty. Concave versus posterior-stabilised tibial joint surface.

We studied the kinetics of the knee in 20 patients (22 knees) 12 months after total knee arthroplasty (TKA), by using three-dimensional radiostereometry and film-exchanger techniques. Eleven knees had a concave (constrained) tibial implant and 11 a posterior-stabilised prosthesis. Eleven normal knees served as a control group. In the posterior-stabilised knees there was less proximal and posterior displacement of the centre of the tibial plateau during extension from 45 degrees to 15 degrees, with a decrease in the anterior translation of the femoral condyles of 4 mm at 45 degrees. There was less internal tibial rotation and increased distal positioning of the centre of the tibial plateau with both designs when compared with the normal knees, and in both the centre of the plateau was displaced posteriorly by more than 1 cm. Increased AP translation has been recorded in all prosthetic designs so far studied by radiostereometry. The use of a posterior-stabilised design of tibial insert could reduce this translation but not to that of the normal knee.

Changed gait pattern in patients with total knee arthroplasty but minimal influence of tibial insert design: gait analysis during level walking in 39 TKR patients and 18 healthy controls.

Introduction Previous radiostereometric studies have revealed abnormal anterior-posterior translation of the femur in patients operated with AMK (DePuy, Johnson and Johnson, Leeds, UK) total knee arthroplasty (TKA). Based on these observations, we hypothesized that patients with TKA have an abnormal gait pattern, and that there are differences in kinematics depending on the design of the tibial joint area. Method We used a gait analysis system to evaluate the influence of joint area design on the kinematics of the hip and knee during level walking. 39 TKA patients (42 knees) and 18 healthy age-matched controls were studied. Patients with 5° varus/valgus alignment or less were randomized to receive either a relatively flat or a concave tibial insert with retention of the posterior cruciate ligament. Patients who had more than 5° varus-valgus alignment and/or extension defect of 10° or more were randomized to receive the concave or a posterior-stabilized tibial component with resection of the posterior cruciate ligament. Results Patients with TKA tended to have less hip and knee extension and decreased knee and hip extension moment than controls. They also tended to walk more slowly. TKA altered the gait pattern, but choice of implant design had little influence. Interpretation In patients with a similar degree of degenerative joint disease and within the limits of the constraints offered by the prostheses under study, the choice of joint area constraint has little influence on the gait pattern.

Kinematics of three variations of the Freeman-Samuelson total knee prosthesis.

The effect of changes in the articulating surfaces on the kinematics of the Freeman-Samuelson total knee replacement was evaluated. Twenty-two patients (22 knees) (median age, 69 years) were randomized to a standard design with a fixed polyethylene bearing, a design with a mobile bearing, or a new design with a spherical medial femoral condyle with a fixed bearing. The patients were studied with radiostereometry and film-exchangers at 0° nonweightbearing and during active weightbearing extension from 45° to 15°. The center of the tibial tray with a mobile-bearing prosthesis occupied a more anterior position than observed in the designs with a fixed bearing. The medial femoral condyle center had a more posterior position in the standard design than in the design with a spherical medial condyle. From a distally displaced position at 45°, the medial condylar center displaced a mean of 1.8 mm proximally during extension in the standard design and had a constant position in the meniscal design. In the spherical design the medial condyle was displaced proximally at 45° and displaced a mean of 1.6 mm distally during extension. The reduced anteroposterior and proximodistal translations in the meniscal design are compatible with improved congruency between the components. The design with a spherical medial condyle stabilized anteroposterior motions, but showed more pronounced proximodistal displacement medially than did the other two designs.

Knee joint kinematics, fixation and function related to joint area design in total knee arthroplasty

The aim was to study the influence of different designs of the joint area on tibial component fixation, kinematics and clinical outcome after a cemented total knee arthroplasty (TKA). The HSS score and a special questionnaire were used at the clinical examination. Conventional radiography was done to record the positioning of the implants and development of radiolucencies. The migration and inducible displacement were evaluated using radiostereometry (RSA). The kinematics of the knee during active extension was studied using dynamic RSA. In randomised and prospective studies 87 knees in 83 patients (28 male, 55 female, age 69, range 50-83) received an AMK (DePuy, Johnson & Johnson) TKA. The patients were divided into two groups. In group 1 the patients had varus/valgus deformities of < or = 5 degrees and the PCL was retained. The PCL was resected in group 2 where the patients had deformities exceeding 5 degrees and/or fixed flexion deformities of more than 10 degrees. In group 1 a flat (F, n = 20) or a concave (C, n = 20) design was implanted (study 3). In group 2 (study 4) the patients received a concave (n = 25) or a posterior-stabilised (PS, n = 22) tibial plateau. The migration of the tibial component, positioning of the prosthesis, development of radiolucencies and the clinical outcome was evaluated after 1 and 2 years. Twenty-two patients (11 F, 11 C) in group 1 (study 1) and 22 knees in 20 patients in group 2 (study 2, 11 C, 11 PS) were examined 1 year post-operatively to evaluate the kinematics of the knee. Eleven normals served as controls. During active extension of the knee the inducible displacements of the tibial component were recorded in 16 knees (15 patients). Based on successful RSA examinations 5 knees (4 F, 1 C) from group 1 and 11 knees (5 C, 6 PS) from group 2 were selected (study 5). Abnormal kinematics and especially increased AP translations compared to normals (p < 0.0005) were recorded in all designs. The concave design showed the widest AP-translations in both studies. The clinical outcome in terms of HSS score did not differ between the flat versus the concave designs in study 1 and between the concave versus the PS implants in study 2. Up to two years the migration of the tibial component and the development of radiolucent lines were of the same magnitude for the flat versus the concave inserts in study 3 and the concave versus the PS design in study 4. Also did the positioning of the implant and the fulfillment of the patients expectations on the surgery preoperatively not differ. The AMK prosthesis migrated at about the same amount as have been reported for similar designs. In study 5 all implants showed a correlation between some of the inducible displacements (anterior-posterior tilting and maximum total point motion) and the corresponding migration 0-2 years. The more the anterior tilt the more the migration in the same direction. If the PCL was sacrificed during the knee replacement the change into increased anterior tilt occurred earlier (i.e. at more degree of flexion) if a concave insert was used compared to the PS design. When the active extension reached 25 degrees there were more anterior tilt of the tibial component in the concave design (p = 0.001) and if the tibial plateau centre had a medial position (p < 0.0005). Compared with normal knees all prosthetic designs showed abnormal pattern of motion. The extent of this abnormality was influenced by the design of the joint area. A corresponding influence on the fixation of the tibial component could not be verified. The choice of joint area and recorded kinematics had no or small influence on the clinical results. Feelings of instability could to some extent be related to the kinematics of the knee joint.

Total knee replacement influences both knee and hip joint kinematics during stair climbing

A gait analysis system was used to evaluate the kinematics of the hip and knee during stair ascending and descending after operation with total knee replacement. Patients with 5° varus/valgus alignment or less were selected randomly to receive either a flat or a concave tibial component with retention of the posterior cruciate ligament. Patients who had more than 5° varus/valgus alignment and/or an extension defect of 10° or more were selected randomly to receive the concave or posterior-stabilized tibial component with resection of the posterior cruciate ligament. Twenty patients and 17 controls were studied 1–2 years after the operation. Patients had abnormal kinematics during stair ascending and descending. Both knee extension and flexion were reduced. Hip extension tended to decrease, and decreased hip extension moment was noted.RésuméUn system d’analyse de la marche a été utilisé pour évaluer la cinématique de la hanche et du genou pendant la montée et la descente d’escalier après prothèse totale du genou. Les malades avec 5° ou moins de varus/valgus ou moins ont été randomisés pour recevoir un composant tibial plat ou concave avec conservation du ligament croisé postérieur. Les malades qui avaient plus de 5° de varus/valgus et/ou un défaut d’extension de 10° ou plus ont été randomisés pour recevoir un composant tibial concave ou un composant postéro-stabilisé avec résection du ligament croisé postérieur. Vingt et un malades et 17 contrôles ont été étudiés une à deux années après l’opération. Les malades avaient une cinématique anormale pendant la montée et la descente l’escalier. L’extension et flexion du genou étaient plus faibles. L’extension de la hanche avait tendance à diminuer et une augmentation du moment de flexion a été noté.

Cemented versus hydroxyapatite fixation of the femoral component of the Freeman-Samuelson total knee replacement: A RADIOSTEREOMETRIC ANALYSIS

We have carried out a radiostereometric study of 50 patients (54 knees) with osteoarthritis of the knee who were randomly allocated to receive a cemented or a hydroxyapatite-coated femoral component for total knee replacement. The patients were also stratified to receive one of three types of articulating surface (standard, rotating platform, Freeman-Samuelson (FS)1000) all based on the Freeman-Samuelson design. The tibial components were cemented in all cases. Radiostereometry was performed post-operatively and at 3, 12 and 24 months. The analysis was restricted to rotation of the femoral component over time. After two years, rotation of the femoral components in the transverse, longitudinal and sagittal planes did not differ between the cemented and the hydroxyapatite-coated implants (p = 0.2 to 0.9). In total knee replacements with a rotating platform, the femoral component tended to tilt more posteriorly than in the other two designs, regardless of the choice of fixation (cemented or hydroxyapatite-coated, p = 0.04). The standard version of the femoral component, whether cemented or hydroxyapatite-coated, rotated more into valgus than was observed with the rotating-platform and FS1000 designs (p = 0.005). The increased constraint provided by the FS1000 component did not appear to have any adverse effect on fixation of the femoral component.

Inducible displacements of cemented tibial components during weight-bearing and knee extension. Observations during dynamic radiostereometry related to joint positions and 2 years history of migration in 16 TKR

The inducible displacements of the tibial component caused by active extension were studied in 16 knees 1 yr after an AMK total knee arthroplasty with either flat, concave or posterior‐stabilised (PS) designs of the joint area. Continuous change of the position of the tibial component occurred with proceeding extension. Rocking, subsidence and lift‐off at different localisations were observed. In 3 of 4 knees with flat inserts the tibial component tilted anteriorly from 45° to 35° of flexion. A similar anterior tilt was seen in 2 of 6 with concave inserts and 5 of 6 with the PS design, but the tilting started later, when the knee had 5–20° more extension. From 45–15° of flexion most components tilted into valgus. Three knees (1 concave with, 1 concave without PCL and 1 PS) showed a sudden tilt into varus direction followed by a rocking motion in the opposite direction. The other types of displacements studied showed a more uniform pattern. The inducible maximum translation (MTPM) at 20° of extension tended to be associated with increased migration between 0 and 2 yr when measured with the same parameter (Spearmans rho = 0.54, P = 0.03). Increased medial displacement of the center of the proximal tibia at 25° was associated with increased anterior tilt. This type of motion was most commonly seen with the concave design. Our observations demonstrate that the forces acting on the tibial component vary during active extension, which results in rocking movements. This will influence the migration and the patttern of wear, factors of importance for the clinical longevity of a total knee replacement (TKR).