Development of Precipitation Hardening Parameters for High Strength Alloy AA 7068.

The mechanical properties after age hardening heat treatment and the kinetics of related phase transformations of high strength AlZnMgCu alloy AA 7068 were investigated. The experimental work includes differential scanning calorimetry (DSC), differential fast scanning calorimetry (DFSC), sophisticated differential dilatometry (DIL), scanning electron microscopy (SEM), as well as hardness and tensile tests. For the kinetic analysis of quench induced precipitation by dilatometry new metrological methods and evaluation procedures were established. Using DSC, dissolution behaviour during heating to solution annealing temperature was investigated. These experiments allowed for identification of the appropriate temperature and duration for the solution heat treatment. Continuous cooling experiments in DSC, DFSC, and DIL determined the kinetics of quench induced precipitation. DSC and DIL revealed several overlapping precipitation reactions. The critical cooling rate for a complete supersaturation of the solid solution has been identified to be 600 to 800 K/s. At slightly subcritical cooling rates quench induced precipitation results in a direct hardening effect resulting in a technological critical cooling rate of about 100 K/s, i.e., the hardness after ageing reaches a saturation level for cooling rates faster than 100 K/s. Maximum yield strength of above 600 MPa and tensile strength of up to 650 MPa were attained.

Obstetric outcomes of pre-induction of labor with a 200 µg misoprostol vaginal insert.

OBJECTIVES: Labor induction is indicated in 20% to 40% of pregnancies. Over half of pregnancies qualified for the induction of labor require stimulation of the cervix to ripen. The drug used increasingly more often in pre-induction is the PGE-1 pros-taglandin analog - misoprostol 200 µg. MATERIAL AND METHODS: The study includes a total of 100 patients qualified for labor pre-induction with Misodel® (miso-prostol 200 µg vaginal insert). The study group comprises two subgroups: primigravidas and multiparas. Assessments included: indications for labor pre-induction, time from Misodel application to delivery, caesarean section rate and indica-tions, duration of first and second stage of labor, rate of vaginal deliveries, need for oxytocin or fenoterol administration side effects and newborn condition. RESULTS: The most common indication for labor induction was gestational diabetes and pregnancy past term. The average time to vaginal delivery was 14 h 45 min, time to the onset of active phase of labor - 11 h 45 min, time to membranes' rupture - 15 h, time to vaginal delivery - 14 h 18 min. The times of multiparas were significantly shorter. The rate of vaginal deliveries within 12 hours amounted to 42.42%, while within 24 hours it reached 83.33%. The overall caesarean section rate was 33%. The most common indication for caesarean section was the risk of intrauterine hypoxia. Tachysystole and hyperstimulation was observed in 4% of cases, while abnormalities in the cardiotocographic tracing in 43%. CONCLUSIONS: Misodel is an effective method for labor pre-induction, without affecting the caesarean section rate and has no adverse effect on the newborn condition.

Kinematic gait parameters changes in patients after total knee arthroplasty. Comparison between cruciate-retaining and posterior-substituting design.

PURPOSE: The patients expect optimal knee function after Total Knee Arthroplasty. It is necessary to apply appropriate surgical technique and supervised physical therapy. The optimal management of posterior cruciate ligament remains controversial. Both implant designs, i.e., cruciate retaining and posterior substituting, allow the orthopedic surgeon to achieve excellent clinical outcomes, as measured by commonly used questionnaires. Such methods of assessment may poorly reflect the functional status of patients. Therefore, three-dimensional gait analysis is recommended to evaluate the outcomes of surgical intervention. This study sought to determine differences in kinematic gait parameters and Knee Society Score between cruciate-retaining and posterior-substituting patients. METHODS: 23 individuals after cruciate-retaining total knee arthroplasty and 19 individuals after posterior-substituting total knee arthroplasty were subjected to gait analysis using three-dimensional motion capture system BTS Smart DX 7000. In addition, gait was assessed in 21 patients with knee osteoarthritis and in 30 healthy individuals. RESULTS: The study did not reveal differences between cruciate-retaining and posterior-substituting groups, both in terms of Knee Society Score and kinematic gait parameters. There were also no differences in kinematic gait parameters between patients from the knee osteoarthritis group and total knee arthroplasty groups. The analyzed parameters in all of the groups differed significantly from those found in healthy individuals. CONCLUSIONS: Surgical technique and implant design do not affect values of kinematic gait parameters evaluated under natural walking speed. Several months after surgery the patients still demonstrated alterations in gait pattern, similar to those recorded in patients with knee osteoarthritis.

Gait analysis in patients after unilateral hip arthroplasty.

BACKGROUND: Osteoarthritis (OA) is the most common joint pathology and the main cause of disability in elderly persons. Arthroplasty still remains the most effective treatment of OA. Routine post-operative patient assessment does not include an objective functional examination leading to conclusions regarding the need of further rehabilitation. This role is played by gait analysis performed in patients after arthroplasty. The aim of the study was to conduct a quantitative and qualitative analysis of selected gait parameters in patients after unilateral cementless hip arthroplasty. MATERIAL AND METHODS: The study involved a group of 16 patients who were examined before and after hip arthroplasty. Gait analysis was conducted before surgery and at least 6 months after the procedure. The Smart DX BTS system for spatial gait analysis was used. RESULTS: The duration of the stance phase on the affected side was 63.8 [% gait cycle] and was significantly shorter (p<0.05) than the phase on the unaffected side, with a duration of 69.4 [% gait cycle]. After surgery, the duration of swing phase on the unaffected side increased (p<0.05) from 30.6 to 35.1 [% gait cycle]. A statistically significant change was also found in the double support phase (the arthrotic limb as the front limb), which was markedly shortened. The average length of a single and double step, cadence, average gait velocity, and the velocity of leg swing in the swing phase increased. The range of hip mobility increased in all planes, especially in the sagittal plane. CONCLUSION: The space and time gait parameters with regard to the operated leg after hip arthroplasty indicate an improvement as compared with the baseline results; however, they do not reach the values found in healthy persons.

The dependence between clinical condition and value of the maximum force in the quadriceps femoris muscle during MVC test in patients with knee osteoarthritis.

The aim of this study was to check whether there was a correlation between the value of the maximum developed torque of the quadriceps femoris muscle and subjective evaluation of a patient's pain which is measured by the VAS. Also evaluated were changes in the muscle torque value and KSS scale over time. For examining patient's condition use was made of a KSS scale (knee score: pain, range of motion, stability of joint and limb axis) before the surgery and in weeks 6 and 12, as well as 6 months after surgery. It was found to be constantly improving in comparison with the condition before the surgery. This is confirmed by a significant statistical value difference of KSS scale. The surgery substantially increases the quality of live and function recurrence.