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PubMedDate not supplied

Influence of the visual environment on the postural stability in healthy older women.

BACKGROUND: A poor postural stability in older people is associated with an increased risk of falling. It is recognized that visual environment factors (such as poor lighting and repeating patterns on escalators) may contribute to falls, but little is known about the effects of the visual environment on postural stability in the elderly. OBJECTIVE: To determine whether the postural stability of older women (using body sway as a measure) differed under five different visual environment conditions. METHODS: Subjects were 33 healthy women aged 65-76 years. Body sway was measured using an electronic force platform which identified the location of their centre of gravity every 0.05 s. Maximal lateral sway and anteroposterior sway were determined and the sway velocity calculated over 1-min trial periods. Body sway was measured under each of the following conditions: (1) normal laboratory lighting (186 lx); (2) moderate lighting (10 lx); (3) dim lighting (1 lx); (4) eyes closed, and (5) repeating pattern projected onto a wall. RESULTS: Each measure of the postural stability was significantly poorer in condition 4 (eyes closed) than in all other conditions. Anteroposterior sway was greater in condition 3 than in conditions 1 and 2, whilst the sway velocity was greater in condition 3 than in condition 2. Lateral sway did not differ significantly between different lighting levels (conditions 1-3). A projected repeating pattern (condition 5) did not significantly influence the postural stability relative to condition 1. CONCLUSIONS: The substantially greater body sway with eyes closed than with eyes open confirms the importance of vision in maintaining the postural stability. At the lowest light level, the body sway was significantly increased as compared with the other light levels, but was still substantially smaller than on closing the eyes. A projected repeating pattern did not influence the postural stability. Dim lighting levels and removing visual input appear to be associated with a poorer postural stability in older people and hence might be associated with an increased risk of falls.

Accidental Falls↗

PubMed1994

Improving detection of coronary morphological features from digital angiograms. Effect of stenosis-stabilized display.

BACKGROUND: We have developed a digital display method that stabilizes the motion of a stenosis in sequential frames of a coronary angiogram, allowing it to be scrutinized at high display frame rates. The purpose of this study was to determine whether this technique improves visual detection of low-contrast luminal morphological features. METHODS AND RESULTS: An observer detection study was conducted using computer-simulated arterial segments containing known target features, inserted into clinical digital coronary angiograms. Four observers performed a forced-choice detection of a simulated filling defect in each of 320 angiograms using the conventional and stenosis-stabilized dynamic displays (at 7.5, 15, and 32 frames per second) and a single-frame static display (total of 8960 detections). In a second simulated clinical task, three observers detected a bridging stenotic lumen in 600 angiograms using the two displays (3600 detections). In a third experiment, two angiographers rated the likelihood of intraluminal thrombus in 89 right coronary digital angiograms by consensus reading with both dynamic displays. Detectability of the simulated filling defect was similar for both dynamic display methods at 7.5 frames per second (averaging twice that for static images). As display rate was increased to 32 frames per second, detectability for the conventional display declined, whereas the stabilized display detectability increased for all observers (P < .05). On average, stabilization allowed detection of filling defects equivalent to a 71% increase in feature contrast. Response time for the conventional display averaged 12.9 +/- 4.7 seconds. For the stenosis-stabilized display, response time fell with increased frame rate (P < .05) to 4.9 +/- 1.2 seconds at 32 Hz, similar to the time for static images (4.6 +/- 0.8 seconds). The detectability of the bridging stenotic lumen was increased by 62% with the stabilization compared with conventional dynamic display (P < .00001). Consensus reading of coronary angiograms showed differences between the two dynamic display methods (kappa = 0.11) that may be explained by an improvement in observer uncertainty. A rating of definite for thrombus present or absent was more frequent with the stabilized display (39% versus 15%, P < .0001). CONCLUSIONS: These data suggest that stabilized display of coronary angiograms significantly increases detectability, reduces the time required for detection, and improves observer uncertainty for the presence of small luminal morphological features. The method of angiographic display may thus have an impact on clinical coronary angiographic interpretation.

Coronary Angiography↗

PubMed2006

Anterior shoulder stabilization in collision athletes: arthroscopic versus open Bankart repair.

BACKGROUND: Collision athletes are reported to be at high risk for redislocation after anterior stabilization of shoulder instability. Some authors have suggested that arthroscopic stabilization produces results similar to those of open stabilization. PURPOSE: To evaluate the results of anterior shoulder stabilization in collision athletes and to compare the clinical results between the arthroscopic and open methods. HYPOTHESIS: Open stabilization might produce better results than does arthroscopic stabilization in collision athletes. STUDY DESIGN: Cohort study; Level of evidence, 4. METHODS: Forty-eight shoulders of 46 collision athletes were enrolled for this study. The mean age of the patients at the time of surgery was 20 years, and the mean follow-up period was 72 months (range, 30-136 months). Sixteen shoulders underwent arthroscopic stabilization; 32 shoulders had open repairs. RESULTS: Visual analog scale, Rowe, and Constant scores improved after surgery, but no statistically significant difference was found between the arthroscopic and open repair groups. Thirty-seven athletes (83%) returned to near-preinjury sports activity levels (>/= 90% recovery) after operation. Two patients (4%) had subluxation and 6 (12.5%) had redislocation after surgery. The number of shoulders with postoperative subluxation or dislocation was 4 (25%) in the arthroscopic group and 4 (12.5%) in the open group (P = .041). Revision surgery was performed on 5 shoulders (10.4%). CONCLUSIONS: There were 8 (16.5%) instances of postoperative instability among the collision athletes studied. The arthroscopic group yielded a higher failure rate than did the open group. The authors believe open stabilization to be a more reliable method for anterior shoulder instability in collision athletes.

Adolescent↗

PubMed2004

Mechanical effect of posterior wire or half-pin configuration on stabilization utilizing a model of circular external fixation of the foot.

BACKGROUND: Numerous studies have addressed biomechanical characteristics of circular external fixation of long bones. The objective of the present study was to evaluate stabilization of a simulated foot model using external fixation with either calcaneal tensioned stopper wires or half-pins. METHODS: Fixation configurations of the calcaneus included two parallel wires, two wires crossing at either 30 degrees or 45 degrees, a 4-mm- and 5-mm-diameter single half-pin, or two half-pins inserted at a cross-angle of either 45 degrees or 90 degrees. All frames were tested in axial compression, anteroposterior (AP) bending, and mediolateral (ML) bending. RESULTS: An increase in wire cross-angle improved the axial and AP bending stabilization but had no influence on ML bending. Utilization of a single calcaneal half-pin instead of two cross-wires resulted in a considerable reduction in ML bending stabilization. Frame configurations with two half-pins substantially improved axial and ML bending stabilization. Due to the medial location of the metatarsal wire stopper, an increase in half-pin cross-angle significantly improved ML bending stiffness under lateral foot loading. Under the medial foot loading, however, the half-pin cross-angle had no effect on ML bending stabilization. Replacement of cross-wires with two half-pins significantly improved the AP bending stiffness only when the half-pin cross-angle was reduced to 45 degrees. In all modes of two half-pin frame loading, the half-pin diameter had a substantial effect on foot stabilization. CONCLUSIONS: Although the wire cross-angle, half-pin cross-angle, and half-pin diameter affect the stability of foot circular external fixation, the influence of these mechanical parameters on foot stabilization is dependent on the mode and location of loading. CLINICAL RELEVANCE: The results of the present mechanical testing can be utilized as a useful guideline for the optimization of circular external fixation of the foot.

Biomechanical Phenomena↗

PubMed2002

Modelling developmental instability as the joint action of noise and stability: a Bayesian approach.

BACKGROUND: Fluctuating asymmetry is assumed to measure individual and population level developmental stability. The latter may in turn show an association with stress, which can be observed through asymmetry-stress correlations. However, the recent literature does not support an ubiquitous relationship. Very little is known why some studies show relatively strong associations while others completely fail to find such a correlation. We propose a new Bayesian statistical framework to examine these associations RESULTS: We are considering developmental stability - i.e. the individual buffering capacity - as the biologically relevant trait and show that (i) little variation in developmental stability can explain observed variation in fluctuating asymmetry when the distribution of developmental stability is highly skewed, and (ii) that a previously developed tool (i.e. the hypothetical repeatability of fluctuating asymmetry) contains only limited information about variation in developmental stability, which stands in sharp contrast to the earlier established close association between the repeatability and developmental instability. CONCLUSION: We provide tools to generate valuable information about the distribution of between-individual variation in developmental stability. A simple linear transformation of a previous model lead to completely different conclusions. Thus, theoretical modelling of asymmetry and stability appears to be very sensitive to the scale of inference. More research is urgently needed to get better insights in the developmental mechanisms of noise and stability. In spite of the fact that the model is likely to represent an oversimplification of reality, the accumulation of new insights could be incorporated in the Bayesian statistical approach to obtain more reliable estimation.

Bayes Theorem↗

PubMed2006

Simulation of pediatric trauma stabilization in 35 North Carolina emergency departments: identification of targets for performance improvement.

OBJECTIVE: Trauma is the leading cause of death in children. Most children present to community hospital emergency departments (EDs) for initial stabilization. Thus, all EDs must be prepared to care for injured children. The objectives of this study were to (1) characterize the quality of trauma stabilization efforts in EDs and (2) identify targets for educational interventions. METHODS: This was a prospective observational study of simulated trauma stabilizations, that is, "mock codes," at 35 North Carolina EDs. An evaluation tool was created to score each mock code on 44 stabilization tasks. Primary outcomes were (1) interrater reliability of tool, (2) overall performance by each ED, and (3) performance per stabilization task. RESULTS: Evaluation-tool interrater reliability was excellent. The median number of stabilization tasks that needed improvement by the EDs was 25 (57%) of 44 tasks. Although problems were numerous and varied, many EDs need improvement in tasks uniquely important and/or complicated in pediatric resuscitations, including (1) estimating a child's weight (17 of 35 EDs [49%]), (2) preparing for intraosseous needle placement (24 of 35 [69%]), (3) ordering intravenous fluid boluses (31 of 35 [89%]), (4) applying warming measures (34 of 35 [97%]), and (5) ordering dextrose for hypoglycemia (34 of 35 [97%]). CONCLUSIONS: This study used simulation to identify deficiencies in stabilization of children presenting to EDs, revealing that mistakes are ubiquitous. ED personnel were universally receptive to feedback. Future research should investigate whether interventions aimed at improving identified deficiencies can improve trauma stabilization performance and, ultimately, the outcomes of children who present to EDs.

Child, Preschool↗

PubMed2000

Stability of the bone-implant complex. Results of longitudinal testing to 60 months with the Periotest device on endosseous dental implants.

BACKGROUND: Maintenance of the health and integrity of the bone-implant complex (osseointegration) has been shown to be essential for long term success of root-form, endosseous dental implants. If reliable clinical indicators of adequacy of the bone-implant complex existed, they could stimulate new and innovative early intervention research to arrest of reverse early deterioration of the bone-implant complex. In the absence of such indicators, this has been problematic. The Periotest may have the potential to provide this information by indirectly assessing the status of the bone-implant complex. However, little information is available that documents either the capability of the Periotest to reliably assess changes of the bone-implant complex or the "normal variations" in Periotest values (PTVs) for both HA-coated and non-coated implants. METHODS: The purpose of this paper was to document changes in PTVs as influenced by various implant surfaces, implant designs, and bone densities. The mean PTVs recorded for each visit, for all implant types and bone densities, were combined to provide an overall average PTV (A-PTV). The changes in stability (PTVs) were analyzed using a generalized linear model (GLM) with repeated measures (Hotelling's Trace). RESULTS: The A-PTV for all implants over all visits was -3.5. The mean PTVs ranged from -4.2 (SD = 2.4) at uncovering to -3.9 (SD = 2.9) at 60 months. All implants in bone qualities 1 and 2 (BQ-1 and BQ-2) became more stable over time, while those in bone quality 3 or 4 (BQ-3 and BQ-4) showed a slight decrease in stability. In BQ-1, the mean PTVs increased from -4.7 at uncovering to -4.9 at 60 months. A similar increase in stability occurred in BQ-2 (-4.1 at uncovering to -4.4 at 60 months). In BQ-3, the stability of the implants decreased over time (-3.6 at uncovering to -2.9 at 60 months), with similar changes recorded for BQ-4 (-2.5 at uncovering to -1.0 at 60 months). When comparing the stability of all HA-coated with all non-coated implants, the HA implants became less stable (-4.4 to -3.4) over time, while non-coated implants showed an improvement in stability (-3.5 to -4.5). The changes in stability found in BQ-1, BQ-2, and BQ-3 were similar, with HA implants becoming less stable and non-coated more stable. HA- and non-coated comparisons were not possible in BQ-4 since there were too few non-coated implants placed in this type of bone. The HA-coated screw showed a decrease in stability when compared to the non-coated screw. CONCLUSIONS: Conclusions of the study are as follows: 1) PTVs are influenced by bone quality and surface coating of the implant; 2) the PTVs at the time of uncovering provide the best estimate of a clinically acceptable PTV for that bone-implant complex; 3) while the PTVs for any bone-implant complex may fluctuate +/- 1.0 around the uncovering PTV during routine healing and loading of the implant, a consistent shift toward a positive PTV that approaches "0" should be cause for concern that the bone-implant complex may be at risk of failure; 4) HA-coated implants became slightly less stable (more positive PTVs) over time, while the non-coated implants became more stable (more negative PTVs); and 5) until a "critical PTV" can be accurately identified, it is suggested that a consistent shift in recorded PTVs that exceeds the +3.0 value on the PTV scale should be viewed with concern for possible deterioration at the bone-implant complex.

Alloys↗

PubMedDate not supplied

An integrated chemical, thermal, and microbiological approach to compost stability evaluation.

The evaluation of compost stability is of the utmost importance for the reliability of composting as a recycling strategy. To date there is no single parameter that can give a sure indication of the stability of composts from different starting materials. This paper investigates different methods of evaluating the dynamics of transformation of materials and the stability level of the end products in a composting process. The following parameters were determined on compost samples of different ages from cotton (Gossypium herbaceum L.) cardings and yard wastes: humification index (HI), degree of humification (DH), thermogravimetry (TG) microbial biomass C (B(C)), and ninhydrin-reactive N (B(NIN)). Finally, from TG, derivative thermogravimetry (DTG) and differential scanning calorimetry (DSC) thermal stability parameters were deduced. Humification parameters in the end products (0.2 and 81% for HI and DH, respectively) showed the effective stability reached by the organic matter (OM). Thermal analysis evidenced the presence of two main organic pools with different thermal stability. During composting a relative increase in the more stable organic pool was indicated by the variation of the thermostability index R1 from 0.41 to 0.74. The parameter R1 was significantly correlated with both HI (r = -0.94; P < 0.05) and DH (r = 0.97; P < 0.05). Microbial biomass content dynamics reflected the availability of readily decomposable substrates. The ratio between B(NIN) and total N in the end product was 0.96%, indicating a good stability level. The simultaneous application of different approaches, considering different properties of composting materials, provides a more complete description of the stability and quality reached by the organic materials.

Biodegradation, Environmental↗

PubMed1999

Lower limb stability with ACL impairment.

STUDY DESIGN: Repeated measures (3 separate day sessions) to determine test reliability; single-session repeated measures to compare stability between limbs. OBJECTIVES: To develop a functional test measuring dynamic stability that is capable of differentiating between the injured and uninjured lower limb in 2 populations: (1) people with anterior cruciate ligament deficiency (ACLd) and (2) people with anterior cruciate ligament reconstruction (ACLr), and to establish the reliability of this test. BACKGROUND: Many functional tests of the lower limb used by clinicians, such as the 1-legged hop for distance, the 1-legged hop for time, the vertical jump, the triple hop for distance, shuttle run, and single-limb standing, do not allow the clinician to discern differences between function in the injured and uninjured limbs. METHODS AND MEASURES: Twenty-five nonimpaired subjects (14 men, 11 women, aged 31.2 +/- 9.1 years), 11 subjects with ACLr (9 men, 2 women, aged 26.3 +/- 10.4 years), and 13 subjects with ACLd (5 men, 8 women, aged 40.4 +/- 12.6 years) were tested. Twelve nonimpaired subjects participated in 3 testing sessions to determine the reliability of the force plate measures. Ground reaction forces (vertical, medial-lateral, and anterior-posterior) were measured while the subjects performed 1-legged hop and step-down tests onto a force plate. Stability was defined as the ability to transfer the vertical projection of the center of gravity to the supporting base and keep the knee still. A repeated-measures analysis of variance (2-factor; limbs by trials) was used to compare the stability between limbs. RESULTS: The majority of the measures used to calculate dynamic stability were reliable. Moreover, the data provide normal standards of functional knee stability for step-down and hop tests. In the step-down test, changes in vertical force did identify dysfunction in the injured limb (stabilization time = 1527 +/- 216 ms) compared to the uninjured limb (stabilization time = 892 +/- 498 ms) for subjects with ACLr. CONCLUSIONS: The normal standards may serve as a reference for comparing functional differences in ACLr or ACLd populations. The vertical force parameter during a step-down may be useful as an outcome measure to monitor progress during rehabilitation.

Adolescent↗

PubMed1984

Temporal stability of multichannel, multimodal ERP recordings.

Personnel assessment applications of event related brain potentials (ERP) require temporal stability. Visual, auditory and bimodal ERP records were obtained about two hours apart for a group of young adult males. Similar records were obtained from a group of older adults about two months apart. No ERP amplitude or temporal stability differences were found between the two groups. Age was positively correlated with visual stability measures and negatively correlated with auditory stability measures. No correlation of age with bimodal stability measures was found. Large individual subject differences were found for the ERP analog waveform and temporal stability. The ERPs were highly stable within subjects from session to session, whether recorded hours or months apart. Greatest stability was obtained for bimodal presentation, less for visual and least for the auditory records. Differences in patterns of waveform stability were found for site and modality conditions across individuals.

Adolescent↗

PubMed2000

Beta 57-Asp plays an essential role in the unique SDS stability of HLA-DQA10102/DQB10602 alpha beta protein dimer, the class II MHC allele associated with protection from insulin-dependent diabetes mellitus.

Studies of the stability of HLA-DQ have revealed a correlation between SDS stability of MHC class II alphabeta dimers and insulin-dependent diabetes mellitus (IDDM) susceptibility. The MHC class II alphabeta dimer encoded by HLA-DQA1*0102/DQB1*0602 (DQ0602), which is a dominant protective allele in IDDM, exhibits the greatest SDS stability among HLA-DQ molecules in EBV-transformed B-lymphoblastoid cells and PBLs. DQ0602 is also uniquely SDS stable in the HLA-DM-deficient cell line, BLS-1. We addressed the molecular mechanism of the stability of DQ0602 in BLS-1. A panel of mutants based on the polymorphic differences between HLA-DQA1*0102/DQB1*0602 and HLA-DQA1*0102/DQB1*0604 were generated and expressed in BLS-1. An Asp at beta57 was found to be critical for SDS stability, whereas Tyr at beta30, Gly at beta70, and Ala at beta86 played secondary roles. Furthermore, the level of class II-associated invariant chain peptide bound to HLA-DQ did not correlate with SDS stability, suggesting that class II-associated invariant chain peptide does not play a direct role in the unique SDS stability of DQ0602. These results support a role for DQB1 codon 57 in HLA-DQ alphabeta dimer stability and IDDM susceptibility.

Alleles↗

PubMed2001

Comparative efficacy of typical and atypical antipsychotics as add-on therapy to mood stabilizers in the treatment of acute mania.

BACKGROUND: Typical antipsychotics are commonly used in combination with mood stabilizers for acute mania. Although typical antipsychotics are effective, they have undesirable side effects such as induction of depressive symptoms and tardive dyskinesia. Atypical antipsychotics have more favorable side effect profiles, and recent evidence shows their efficacy in treating mania. Apart from a previous small study that compared risperidone with typical neuroleptics as add-on therapy to mood stabilizers, no studies to date have directly compared atypical antipsychotics with typical antipsychotics as add-on therapy to mood stabilizers in a clinically relevant, naturalistic setting. METHOD: This study is a chart review of all patients with DSM-IV-defined bipolar disorder, current episode mania (N = 204), admitted to the University of British Columbia Hospital during a 30-month period. Patients were separated into 3 groups according to the medications used: (1) mood stabilizer and typical antipsychotic, (2) mood stabilizer and atypical antipsychotic, and (3) combination: mood stabilizer plus a typical antipsychotic, then switched to mood stabilizer plus risperidone or olanzapine within I week. The atypical group was further subdivided into risperidone and olanzapine subgroups. Outcome was measured using Clinical Global Impressions-Severity of Illness (CGI-S) and -Improvement (CGI-I) ratings generated by review of clinical information in the chart. RESULTS: Patients treated with typical antipsychotics were more severely ill at admission and at discharge than those treated with atypical antipsychotics. Patients in the atypical (p < .005) and combination (p < .05) groups showed significantly greater clinical improvement at discharge than patients treated with typical antipsychotics. This difference was also significant in the subset of patients with psychotic features (p < .03). Risperidone and olanzapine were associated with fewer extrapyramidal side effects than were typical antipsychotics (risperidone vs. typical antipsychotics, chi2 = 8.72, p < .01; olanzapine vs. typical antipsychotics, chi2 = 16.9, p < .001). CONCLUSION: Due to their superior effectiveness and side effect profile when compared with typical antipsychotics. atypical antipsychotics are an excellent choice as add-on therapy to mood stabilizers for the treatment of patients with mania.

Acute Disease↗

PubMed2026

Associations of Trajectories of Loneliness and Neighborhood Stability with Depression, Alcohol and Substance Use, and Quality of Life among Women Living with HIV.

Social relationships are an important social determinant of health. Loneliness, the perceived gap between one's actual and desired relationships, has emerged as an important mechanism through which social relationships impact health. Like other intrapersonal-level factors associated with health, loneliness is influenced by broader social and structural factors, including characteristics of one's neighborhood social environment. Although neighborhood-level protective and risk factors for loneliness and for mental health have been identified, prior studies have often focused solely on self-reported perceptions of the neighborhood environment. Further, few have considered aspects of the neighborhood social environments, such as neighborhood stability (i.e., stability of the community with long or short-term residents), independent of neighborhood socioeconomic conditions. In the current analysis, we explored longitudinal patterns of loneliness in conjunction with neighborhood stability among women with HIV (WWH) enrolled into the MACS/WIHS Combined Cohort Study (MWCCS) from 2014-2019 (N 2019=1,394) to examine whether trajectories of loneliness and neighborhood stability were associated with depressive symptoms, non-prescription substance use, past-year cannabis use, number of alcoholic drinks per week, and several domains of quality of life. Loneliness at baseline (Betas = 0.24 - 0.54) and changes in loneliness over time (Betas = 0.11 - 0.26) were associated with each outcome, except for the association between changes in loneliness over time and drinks per week (Beta=0.13, p = 4.14x10-2), which did not persist after correcting for multiple comparisons. Neighborhood stability at baseline was associated with past year cannabis use (Beta=0.26, p = 1.00x10-2), depressive symptoms (Beta=-0.12, p = 1.54x10-3), and overall self-reported health (Beta=-0.08, p = 2.05x10-2). Changes in neighborhood stability across time were not associated with any outcome. Neighborhood stability moderated the association between changes in loneliness and general health perceptions. Our results demonstrate both overall loneliness and changes in loneliness over time have implications for current mental health in WWH, while changes in neighborhood stability did not.

Journal Article↗

PubMed2002

Characterization and dewaterability of raw and stabilized sludge using different treatment methods.

A comparison of the characteristics and stabilization potential of the four most used sludge treatment systems in Mexico was made. A pilot plant constituted by separate systems for anaerobic and aerobic digestion, lime stabilization, conditioning and dewatering, was built and operated during four months in one of the biological wastewater treatment plants in Acapulco, Mexico. Composting of sludge was also made. An aerobic static pile was built using bulking materials available in the region. A turbine centrifuge was used for dewatering the stabilized sludge and results showed good performance of the device. The main problem for the beneficial use of treated sludge was its pathogenicity. The composting process allowed us to obtain a product with approximately 20 fecal coliform density (MPN/g); with lime stabilization, the sludge produced had a fecal coliform density of 2 MPN/g. From these results, it is concluded that both the composting process and the alkaline stabilization with lime produce a well stabilized sludge, bacteriologically safe that accomplishes the requirements for its use on soil without restrictions. Related to parasitological removal, the best helminth egg removals were obtained also using these two processes. Ascaris sp. densities in raw sludge (309-430 eggs/g) were reduced to a final density of 3-14 eggs/g in the aerobic composting process and to 4-18 eggs/g in the lime stabilized sludge. Removal is not high enough to reach the recommended level for unrestricted use of stabilized sludge.

Animals↗

PubMed2004

[Post-traumatic anterior shoulder instability--arthroscopic stabilization method using bone anchors].

PURPOSE OF THE STUDY: To evaluate the short-term results of re-insertion of the ventral labrum associated with plication of the capsular structures in anterior post-traumatic instability of the shoulder. MATERIAL: The patients treated in our institution between April 2000 and December 2002 and followed up for periods ranging from 3 to 20 months were included. A total of 65 patients were treated for post-traumatic ventral instability. Open capsular shift, after a final evaluation of preoperative examination under total anesthesia and arthroscopic inspection of the labroligamentous complex affected, was used in four patients. Arthroscopic stabilization was carried out in 49 men and 12 women, aged 18 to 49 years (average, 28.5). These patients were allocated to groups according to the number of previous dislocations as follows: group 1 (24 patients), one to five dislocations; group 2 (27 patients) six to ten dislocations; and group 3 (10 patients) 11 and more dislocations. The glenohumeral joint was inspected arthroscopically to find out potential lesions and evaluate them in relation to the number of previous dislocations. METHODS: Stabilization was carried out by means of non-absorbable anchors. It involved re-insertion of the ventral labrum and plication of the ventral capsular structures. The patients were evaluated on the basis of a modified system of Rowe and Zarins. RESULTS: In group 1, the anterior labrum or capsule showed only isolated lesions; most injury-related lesions were found in group 3. With the increasing number of dislocations, there was an increase in associated findings and severity of injury to the labroligamentous complex. The average score before the operation was 37.87 points (range, 20 to 60). After rehabilitation was completed, 57 (93.44%) patients scored good or excellent (70 or more points), with 29 (47.54%) having over 90 points; only four (6.56%) patients scored less than 70 points. Fifty-seven patients resumed their previous sports and four patients carried on with recreational sports activities. DISCUSSION: Open stabilization has been reported as being slightly more effective in maintaining stability, as compared with arthroscopic procedures. The major advantages of arthroscopy include a good view of the intra-articular structures, minimal invasiveness and less restricted range of postoperative motion. However, the arthroscopic stabilization technique becomes more difficult with an increasing number of dislocations sustained before this procedure. The ventral structures of the shoulder joint, known as labroligamentous complex, should be regarded in their complexity and anterior stability should be achieved both by re-insertion or adaptation of the glenoid labrum and by stretching the capsular structures, particularly the inferior glenohumeral ligament. Studies reporting a high degree of recurrence after the initial dislocation in subjects aged 20 to 30 years are discussed. In top, active sportsmen and sportswomen, stabilization after the first dislocation followed by instability appears to be a very effective therapy. CONCLUSIONS: Arthroscopic stabilization with the use of non-absorbable anchors for the treatment of anterior post-traumatic instability of the humeral joint is a method that, in indicated cases assessed mainly by mobility of the labrum and laxity of the anterior capsule, shows a high success rate. Indications are based on medical histories, clinical and radiographic findings and, most importantly, clinical tests under total anesthesia and arthroscopic confirmation of lesions of the ventral structures of the joint.

Adolescent↗

PubMed2005

[Arthroscopic stabilization of the fractured intercondylar eminence].

PURPOSE OF THE STUDY: The authors present the results of arthroscopic reduction of a displaced fracture of the intercondylar eminence and stabilization of the fracture with a tension band wire and absorbable, double PDS sutures. MATERIAL: In the years 1998 to 2002, a fracture of the intercondylar eminence was arthroscopically diagnosed in 34 patients, 21 women and 13 men in the age range of 17 to 46 years. Five patients had type I fracture, 13 had type II fracture and 16 had type III fracture, as classified by the Meyers and McKeever system. Arthroscopic stabilization was used for all type II and type III fractures in a total of 29 patients. Double PDS sutures no. 1 were always applied. One double PDS loop was used in eight patients and, in the rest, two or three double PDS loops were employed. METHODS: PDS no. 1 sutures were inserted, by means of wire loops, through bone tunnels. These were drilled with 2-mm Kirschner's wires, using an anterior cruciate ligament (ACL) reamer, medial to the tibial tuberosity. Double PDS sutures were applied to the distal portion of the ACL, which permits good stabilization even in comminuted fractures of the eminence. The strength of a double PDS loop is sufficient and facilitates speedy recovery. Before terminating surgery it is necessary to check joint mobility and fixation stability. Only good stability allows for early mobilization of the joint. The postoperative treatment involved immobilization of the knee joint with a rigid brace in a semi-flexed position at 20 degrees for 6 weeks. However, from the second postoperative day, the brace was removed during targeted rehabilitation. Exercise on a continuous passive motion device, strengthening of the thigh muscles, patellar mobilization, walking with the use of crutches, while wearing the brace, with partial weight bearing until pain were practised. A treadmill without loading was used from the fifth postoperative week. RESULTS: Twenty-nine patients in whom stabilization with PDS sutures was used were evaluated. Of them 26 were completely free from any complaints and fully healed, always without findings of displacement on X-ray. In one patient, a fragment of the comminuted fracture was loosened and interfered with full extension. It was removed by arthroscopy and full recovery without consequences ensued. One patient underwent repeat surgery for hematoma in the wound; after wound healing and rehabilitation, he achieved a full range of motion. One patient showed signs of fibrosis of Hoffa's fat pad. All patients returned to the style of life as before injury. At follow-up of 1 to 4 years, Lysholm scores were excellent in 23 patients, very good in four patients, satisfactory in one patient (repeat surgery) and one patient was not examined. DISCUSSION: Fracture of the intercondylar eminence is caused by a mechanism similar to that causing rupture of the anterior cruciate ligament but, in addition, the margin of the intercondylar fossa is pressed against the eminence which breaks off. Displaced fractures (types II and III according to the Meyers and McKeever classification) are indicated for surgical stabilization. Fixation of the fractured eminence by means of absorbable material is sufficient, and insertion of metal material and its subsequent removal thus can be avoided. Arthroscopic inspection permits exact reduction; this procedure is minimally invasive. CONCLUSIONS: Arthroscopic stabilization of a fractured eminence by means of PDS sutures is a gentle surgical procedure that provides good mechanical support, facilitates early rehabilitation and achieves good outcomes. The use of absorbable sutures allows us to avoid further surgery in order to remove fixation material.

Adolescent↗

PubMed1991

Glycosylation of the Mr 46,000 mannose 6-phosphate receptor. Effect on ligand binding, stability, and conformation.

Using site-directed mutagenesis the N-glycosylation sites of the Mr 46,000 mannose 6-phosphate receptor (MPR 46) were identified as asparagine residues 57, 83, 107, and 113. The two outer asparagines carry high mannose-type and the two inner asparagines carry complex-type oligosaccharides. The glycosylation mutants were analyzed for stability, binding activity, and subcellular distribution. Replacing asparagine 57, 83, or 107 by threonine decreased only the stability of the receptor. Replacing asparagine 113 by threonine decreased the stability and binding activity. Deletion of three or all four N-glycosylation sites led in addition to an accumulation of the mutant receptors in endoplasmic reticulum-like structures. Nonglycosylated MPR 46 synthesized in the presence of tunicamycin, thus preserving the asparagine residues, had a normal stability and high affinity binding. The decreased stability and binding activity of the receptor mutants is therefore due to the exchange of asparagine residues rather than to the loss of N-linked oligosaccharides. The nonglycosylated receptor, however, displayed a decreased conformational stability after solubilization as a single cycle of freezing and thawing reduced the binding activity to one-third of the control. Simultaneously, the receptor lost its quaternary structure. It is concluded from these results that the N-glycosylation of the receptor is required for the stability of a high affinity conformation, but not for the binding itself or the intracellular stability.

Cell Compartmentation↗

PubMed1990

The enhanced ATPase activity of glutathione-substituted actin provides a quantitative approach to filament stabilization.

[Cys374]glutathionyl-actin was prepared by isolation of the reaction product of G-actin with Ellman's reagent (5,5'-dithiobis-(2-nitrobenzoic acid], followed by reaction with glutathione. Filaments of this actin disulfide are susceptible to even weak shearing stress as exerted, for example, by heating to 37 degrees C. This treatment produces a 25-fold enhanced steady-state ATPase activity as compared to unsubstituted F-actin at room temperature. Monitoring the reduction of this enhanced ATPase activity is a reliable method for quantifying the effectiveness of filament-stabilizing agents and for determining their apparent dissociation constants. A detailed comparative study of filament-stabilizing agents was performed, and some hitherto unknown filament-protecting effects were revealed. Inorganic phosphate provides stabilization only to a maximum of 45% ATPase inhibition, but reaches this effect already at cytoplasmic Pi concentrations (approximately 4 mM). Arsenate seems to bind with similar affinity, but with distinctly less protective activity (maximum of 16%). High concentrations of alkali ions provide a more effective protection (maximum of 95%), Li+ being more efficient than Na+ and K+. Divalent cations (Ca2+, Mg2+) had a strong stabilizing effect on KCl-polymerized actin; we confirmed the presence of two distinct classes of binding sites for divalent metal ions with moderate and low affinities, apparent in a strong stabilizing effect on KCl-polymerized actin. The stabilizing effects of KCl and Pi are independent and additive. Correspondingly, at K2HPO4 concentrations greater than 4 mM, K+ ions contribute considerably to stabilization. In the presence of 100 mM KCl plus 4 mM Pi, conditions which mimic the physiological environment, filament protection is nearly as effective as with the mushroom toxin phalloidin. The strong stabilizing effect of phalloidin occurred at concentrations far below stoichiometric, suggesting a very high degree of cooperativity in its interaction with actin filaments.

Actin Cytoskeleton↗