Mobile and fixed bearing total knee prosthesis functional comparison during stair climbing.

OBJECTIVE: The purpose of this investigation is to determine the functional performance of the mobile bearing total knee replacement prosthesis as compared to the fixed bearing type total knee replacement prosthesis. DESIGN: Kinematics, kinetics, and electromyography data were gained from 10 patients with mobile bearing and 10 patients with a fixed bearing posterior stabilized Insall Burstein II total knee replacement during ascending and descending stairs. A control group of 10 normal subjects, matched by sex and age, was also analysed. BACKGROUND: No significant biomechanical differences in patients with different total knee replacement designs have been reported from level-walking studies. Slightly better performance of posterior retaining with respect to cruciate sacrificing total knee replacement designs have been claimed from stair climbing studies. Only one study has been conducted regarding mobile versus fixed bearing total knee replacement assessed by gait analysis. This study did not show any biomechanical differences between the two groups. METHODS: Motion analysis was used to quantify the knee kinematics, kinetics, and electromyography (right and left longissimus dorsi, gluteus medius, rectus femoris, biceps femoris, semitendinosus, gastrocnemius and tibialis anterior muscles) during stair ascent and descent. RESULTS: The mobile bearing group demonstrated a reduced knee extensor moment during stair climbing and descending, and a reduced knee adductor moment during stair climbing. When ascending stairs, most of the mobile bearing patients show a peak knee flexion and a peak knee flexion moment at the late stance phase during the double support period. This kinematic and kinetic pattern is absent in normal subject. Both mobile bearing and fixed bearing groups showed abnormal electromyography patterns in both descending and ascending. CONCLUSIONS: During stair climbing, the mobile bearing design demonstrates a different kinematic pattern to the fixed bearing total knee replacement. Lower limb compensatory mechanisms seemed to be adopted particularly by the mobile bearing patients during ascending stairs. RELEVANCE: Total knee replacement patient with mobile bearing design can feel excessive femoro-tibial motion during daily living activities such as stair climbing and descending. Proprioceptive control of this tibio-femoral translation is needed as demonstrated by the lower limb compensatory mechanism. This data suggest that antero-posterior constraint structures (ligamentous or mechanical) are important to obtain reproducible knee kinematics.

The Insall-Burstein total knee replacement in osteoarthritis: a 10-year minimum follow-up.

A total of 99 Insall-Burstein posterior stabilized (IBPS) knee replacements were implanted in 86 osteoarthritic patients. We reviewed 60 knees with a 10- to 15-year follow-up. Using the Knee Society score, 35 knees (58%) were excellent, 15 (25%) good, 4 (7%) fair, and 6 (10%) poor. Flexion at follow-up was 106 degrees on average. Moderate patellofemoral crepitation was present in 5 knees (9%), and 11 knee required excision of a synovial nodule proximal to the patella. Radiographic analysis showed 5 osteolytic lesions (8%) around well-fixed tibial and femoral components and minimal (1 mm) narrowing of the medial polyethylene thickness in 7 knees (12%). There were 6 (10%) failures requiring reoperation because of aseptic loosening (4 knees), deep infection (1 knee), and recurrent patellar dislocation (1 knee). Survivorship analysis using revision as the endpoint showed a cumulative success rate of 92% at 10 years. In this study, the IBPS knee has shown good long-term results with low rates of aseptic loosening and no failures attributable to polyethylene wear.

[The biocompatibility of temporary cements. Longitudinal in-vitro analyses of the pH values]. / Biocompatibilità dei cementi provvisori. Analisi longitudinali in vitro dei valori del pH.

In this longitudinal study the authors analyse the acid-basal characteristics in vitro of seven cements used in dentistry for a period of three weeks. The cements tested were subdivided into three groups based on their composition, whereas Life was presented separately since it is generally used as a sub-base for fillings in conservative treatment. All the materials studied alter the pH of the matter in which they are imbedded. Life and Tempbond present the highest and lowest pH values recorded during the study in vitro. The authors discuss the biological implications of these results.

Results of surgical treatment of arthrofibrosis after ACL reconstruction.

We prospectively studied 31 knee arthrolyses performed for loss of motion after intra-articular anterior cruciate ligament (ACL) reconstruction. The arthrolysis was performed on average 10.6 months after the reconstruction (range 4-25). Seven knees were localized forms. They were treated with arthroscopic removal of a fibrous nodule and scar tissue anterior to the ACL, which was preserved. Twenty-four knees were global forms and treated arthroscopically (14) or in open procedure (10). Suprapatellar, medial, and lateral gutter adhesions were sectioned, and fibrous tissue was removed from the anterior compartment. A posteromedial and/or posterolateral capsulotomy was necessary in 7 knees. The ACL graft was nonfunctional and/or malpositioned in 19 knees. The results were evaluated with the IKDC form with an average follow-up of 3.5 years (range 1.5-7). Preoperatively the localized forms had an average extension loss of 11 degrees and an average flexion loss of 14 degrees compared to the opposite knee. At follow-up all the knees were satisfactory for symptoms. All except one achieved a satisfactory motion (within 5 degrees of extension loss and 15 degrees of flexion loss) and a satisfactory final result. Global forms had a greater preoperative flexion loss (average 34 degrees) and extension loss (average 17 degrees). At follow-up 58% were satisfactory for symptoms and 71% for arc of motion. However, the final result was satisfactory in only 37%. In conclusion, local forms have a good prognosis. In global forms motion may be improved by surgery, but the final result is downgraded by symptoms. Arthrolyses performed within 8 months from index operation had a better outcome.