Tuuli Saari

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.

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.

Simultaneous measurements of knee motion using an optical tracking system and radiostereometric analysis (RSA)

Background and purpose Invasive methods are more reproducible and accurate than non-invasive ones when it comes to recording knee kinematics, but they are usually less accessible and less safe, mainly due to risk of infection. For this reason, non-invasive methods with passive markers are widely used. With these methods, varying marker sets based on a number of single markers, or sets of markers, known as clusters, are used to track body segments. We compared one invasive method—radiostereometric analysis—with a non-invasive method, an optical tracking system with 15 skin-mounted markers. Methods 9 subjects (10 knees) were investigated simultaneously with a dynamic RSA system and a motion-capture system while performing an active knee extension. Results For flexion/extension, there was good agreement on an individual basis and at the group level. For internal/external rotation, the group mean was fairly similar, up to 25 degrees of flexion. Recordings of abductions and/or adductions revealed a systematic mean difference of 2–4 degrees during the range of flexion measured. The correlation between the 2 methods in the horizontal and frontal planes was poor. Interpretation Our skin-marker model provided reliable data for flexion/extension. Recordings of internal/external rotation and abduction/adduction were less accurate on an individual basis than at the group level, most probably due to soft-tissue motion and the presence of small true motion in these planes.

Risedronate does not enhance fixation or BMD in revision cups: randomised study with three years follow-up

Background Bisphosphonates may improve implant fixation by inhibition of bone resorption and stimulation of osteoblasts by up regulation of BMP-2. However, there are few clinical studies in this area. Questions/purpose Does treatment with oral bisphosphonates improve implant fixation and bone remodelling around the acetabular component after revision arthroplasty with or without use of morselised allograft? Patients and methods Fifty-three patients received university pharmacy blinded medication for three months: 5 mg risedronate or placebo one dosage and 1 g calcium carbonate and 800IE cholecalciferol per day. Forty-one patients were operated upon with revision of the cup. The revisions were performed with an uncemented (Trilogy, Zimmer, Warsaw, USA) or a cemented (Ogee, Depuy Int, England) cup. Radiostereometric analysis was obtained within one week after the operation, at three and six months, and after one, two and three years to study cup migration. Bone mineral density was measured postoperatively, at six months, one and two years, using DEXA. The presence and extension of radiolucent lines and graft remodelling were studied on conventional radiography. Results The risendronate group revealed less anterior-posterior rotation at 6 months. We found no significant differences in migration at three years, change in bone mineral density, or graft remodelling and radiolucent lines formation between groups. Conclusions We could not demonstrate any beneficial effects of oral administration of risedronate on the fixation, bone mineral density or bone remodelling of revision cups using various amount of bone graft.

Abnormal motion of the medial femoral condyle in lateral knee osteoarthritis.

The pattern of knee motion in patients with lateral osteoarthritis may be associated with the pathogenesis of this disease. Based on previous findings of decreased anteroposterior femoral condylar translation in knees with medial knee osteoarthritis, we asked whether a similar pattern of knee kinematics in lateral osteoarthritis could be related to the wear pattern on the tibial plateau. We used sequential radiostereometric images to study kinematics during active weightbearing extension in five knees with lateral osteoarthritis and 11 control knees. At 45° of flexion, the posterior circular center of the lateral femoral condyle displaced posteriorly at 45° and moved anteriorly during extension in both groups. There was also a proximal displacement with extension, but from a more distal position in the osteoarthritis group. We could only partly relate the kinematics of knees with lateral osteoarthritis to the wear pattern on the tibial plateau. Contrary to our hypothesis of normal anterior displacement of the medial and increased posterior displacement of the lateral femoral condyle, we observed no change of anterior-posterior displacements of the lateral condyle.