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

Albanska som modersmål - En kartläggning med hjälp av interjuver av albanska personers svårigheter vid inlärning av svenska som andraspråk

Jag har i den här uppsatsen undersökt vilka svårigheter personer med albanska som modersmål möter när de ska lära sig svenska som andraspråk. Anledningen till att jag valt detta ämne för min uppsats är att albanska är ett indoeuropeiskt språk som utgör en egen gren i det indoeuropeiska språkträdet och svenska är ett nordgermanskt språk. Därför är en jämförelse mellan svenska och albanska intressant. Utgångspunkten för min uppsats är att det måste innebära en särskild utmaning för personer med albanska som modersmål att lära sig ett andraspråk som svenska. Mitt syfte med uppsatsen är att undersöka vilka problem som personer med albanska som förstaspråk möter när de lär sig svenska. De forskningsfrågor jag använt mig av i uppsatsen har tillämpats praktiskt i en kartläggning med hjälp intervjuer där jag forskat kring vad personer med albanska som förstaspråk upplevt som svårt när de lär sig svenska. De intervjufrågor som jag använt mig av i denna kartläggning finns redovisade i uppsatsen under rubriken bilaga. Min uppsats innehåller tre delar: en redovisning av skillnaderna mellan svenska och albanska samt en kort historik över det albanska språkets uppkomst, ett intervjuavsnitt med tre deltagare som har albanska som modersmål där de berättar hur de lärt sig svenska som andraspråk och en diskussion där jag redovisar vad jag kommit fram till samt resonerar kring detta. Jag avslutar mitt arbete med en slutsatsdel där resultatet av min diskussion sammanfattas. Resultatet av min uppsats är att många av de antaganden som mina forskningsfrågor som baseras på tidigare forskning inte går att bevisa eftersom deltagarnas svar skiljer sig åt

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 £ 5° and the PCL was retained. The PCL was resected in group 2 where the patients had deformities exceeding 5° and/or fixed flexion deformities of more than 10°. 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 were evaluated after one and two years. Twenty-two patients (11F, 11C) in group 1 (study 1) and 22 knees in 20 patients in group 2 (study 2; 11C, 11PS) were examined one year postoperatively 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 (4F, 1C) from group 1 and 11 knees (5C, 6PS) 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 designs in study 4. The positioning of the implant and the fulfilment of the patients expectations on the surgery preoperatively did not differ. The AMK prosthesis migrated at about the same amount as reported earlier 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 up to 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 with the PS design. When the active extension reached 25 degrees there was more anterior tilt of the tibial component in the concave design (p=0.001, r2=0.62) and if the tibial plateau centre had a medial position (p<0.0005, r2=0.78).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