Roentgen stereophotogrammetric analysis (RSA) under stress conditions was used to investigate possible stress-inducible displacement of the tibial component of unicompartmental knee prostheses (UKR) ...in which the stability was previously assessed by radiographic evaluation and standard supine RSA examinations. Sixteen patients, implanted with Duracon UNI® prosthesis, were selected for this study. The RSA protocol included examinations in plain upright standing posture and during execution of stress-inducing tasks in weight-bearing stance. The first follow-up was performed at an average of 14 months, and the second one at 26 months. The results showed non-negligible stress-induced rotations of the prosthetic tibial component in all the patients in most of the stress tasks performed. Rotational stress tasks and squatting turned out to be the stress conditions in which induced displacement reached the most significant values (
p<0.05). These micromotions occurred mainly around the transverse axis of the knee joint and in one examination around the sagittal axis. Stress-induced translations were negligible in all the examinations.
Moreover, we focused our attention on two patients suffering from inexplicable pain, and we observed a significant difference in the inducible rotation around the
x-axis between these patients and the remaining fourteen.
Stress-inducible displacement is a common finding in knee prostheses, but we observed that in patients with inexplicable pain, these micromotions reached values greater than the median calculated on patients without any pain. This result suggests the introduction of the stress-inducible displacement as a new parameter to be taken into consideration when analyzing the outcome of patients treated by UKR.
Roentgen stereophotogrammetric analysis (RSA) was used to investigate the stability of the tibial component in unicompartmental knee arthroplasty. Twenty patients were implanted with a Howmedica ...Duracon UNI prosthesis (Limerick, Ireland) and studied for an average follow-up of 30 months. In most cases, the displacements detected at 1-year follow-up were small (ie, not exceeding 0.5 mm for translations and not exceeding 1.0° for rotations). Only 1 patient showed signs of mechanical loosening as the prosthesis continued to migrate, reaching 3.2 mm of total motion at 4-year follow-up. RSA did not show any deformation in the polyethylene except for the case of loosening. The clinical results were excellent and good according to the Hospital for Special Surgery scoring system. No correlation was found among demographic, clinical, and RSA data. Copyright 2002, Elsevier Science (USA). All rights reserved.
The aim of this study was to investigate the migration pattern of the Lubinus SP II prosthesis stem. Migration at the stem-cement and at the bone-cement interface was assessed. Twenty-five patients ...were studied by radiostereometry during a period of 2 years. The migration of the head, of 2 points on the collar, of the stem tip, and also of the cement restrictor, was measured. The collar and the head were found stable at 2 years' follow-up, whereas an anterior migration occurred at the stem tip (median, 0.3 mm; 25th percentile, 0.04 mm; 75th percentile, 1.27 mm). Virtually no subsidence or axial rotation of the stems was observed. An anterior migration of the restrictor marker was also observed, compatible with a rigid sagittal plane rotation of the stem and of the cement mantle about the collar. Therefore, stem tip migration occurred at the bone-cement interface.
Roentgen Stereophotogrammetric Analysis (RSA) is the most accurate technique to measure micromotion between rigid bodies and it has been widely used in the orthopedic field to investigate lower limb ...prostheses.
The aim of this paper was to investigate the factors affecting the accuracy of measurements performed on the knee joint by the biplanar RSA system. Errors were assessed by means of a test object. A particular goal was to verify the reliability of the system when the patient cannot stand in the ideal position during the examination, i.e. in the centre of the calibration space. Results showed that detection of micromotion is not correlated to the position of markers inside the calibration space.
The influence of different materials able to simulate human tissues, both hard and soft, on the data acquisition phase was also investigated. This additional exam was performed to assess whether the results obtained were similar also under as close as possible conditions to the clinical trials. Different experimental conditions were shown to not affect the acquisition phase of RSA procedure; markers were acquired with equal accuracy independently of tissues examined.
Since the acquisition procedure is often performed by different operators, the difference between acquisitions made by different operators was compared.
This study confirms the reliability of RSA and its accuracy, also in non-standard clinical setup and acquisition procedures.
We assessed the migration and movement between the half-bearings of the Interax prosthesis in 18 patients using roentgen stereophotogrammetric analysis (RSA). This study showed movements of the ...tibial component even in successful knee arthroplasty: 17 prostheses migrated only initially and remained stable after 1 year, whereas 1 prosthesis migrated consistently throughout 3-year follow-up. RSA revealed no or minimal displacement between the half-bearings until the 4-year follow-up, confirming that their fixation to the baseplate was adequate. In the case of loosening, a rotation about the longitudinal axis of 1.3° and a medial-lateral translation of 0.5 mm was observed between the half-bearings. Cold flow was revealed by RSA in the posterior region of the medial half-bearing.
In six cadaver specimens the mobility of the proximal fibula in relation to the tibia was investigated during plantar/dorsiflexion of the ankle, using Roentgen Stereophotogrammetric Analysis (RSA). ...The role of the ankle joint, and of the calcaneofibular and talofibular ligaments was also evaluated.
The greatest movements were observed along the medio-lateral and anterior-posterior axes, resulting in an anterolateral displacement of the fibula head during dorsiflexion and in a postero-medial displacement during plantarflexion.
This study demonstrated a limited mobility of the proximal tibiofibular joint. Moreover, the ligament cutting and the presence of constraints in the ankle region did not show any effect on the fibular movement.
PurposeWe compared two different strategies providing professional coaching to administer an exercise program for women with postmenopausal osteoporosis (POP): individual training (IT) at home with ...trainer's supervision provided by telephone contacts at regular time-intervals or group training (GT) with trainer's live supervision. Our working hypothesis was that IT is a valid alternative to GT when GT is not feasible. Patients and MethodsThis was a single-blind, randomized study. We recruited 52 women with POP, without significant comorbidity, and no participation in any structured exercise program within the previous 6 months. They were assigned randomly to IT or GT groups (n = 26 each). Distribution of age (IT: 68±4, GT: 67±8 years) and body mass index (IT: 23.0±2.5, GT: 21.4±5.1) was similar between groups. Each group performed the exercise program in two 1-hour sessions per week for 18 months. Primary outcome measure was Health-Related Quality of Life (HRQoL), as measured by the Short Osteoporosis Quality of Life Questionnaire. Secondary outcome measures focused on domains acknowledged to influence HRQoL (disability, fear of falling, weekly physical activity, physical function) or the effectiveness of the exercise program (retention, adherence, and safety). Significance level was set at p < 0.05. ResultsNo significant differences were observed between IT and GT groups for any domain. Retention, adherence, and safety were also similar. HRQoL, disability and fear of falling did not change between baseline and follow-up for either group. However, for both groups, physical function (knee flexion, shoulder mobility) and functional capacity (6-minute walking test) improved. Weekly physical activity levels increased from moderate range at baseline to intense at final assessment for both groups. ConclusionIT and GT supervised exercise programs for women with POP provide similar effectiveness, participation and safety. Hence, both modalities should be considered for future translation in clinical practice of exercise recommendations for POP.
