1,721,013 research outputs found
Analisi morfologica dei fallimenti della ricostruzione a doppio fascio del legamento crociato anteriore.
No full textObiettivo: Obiettivo dello studio è valutare il processo di rimodellamento degli innesti utilizzati per ricostruzione del legamento crociato anteriore (LCA), con tecnica a doppio fascio (anteromediale, AM; posterolaterale PL), in 4 fallimenti di tipo traumatico. L’ipotesi dello studio è che dopo ricostruzione del LCA si realizzi un differente processo di maturazione tra i due fasci. Materiali e metodi: 6 innesti sono stati prelevati da 4 diversi pazienti sottoposti ad intervento di revisione del LCA. In 2 pazienti entrambi i fasci erano lesionati, mentre nei rimanenti 2 solo il fascio AM. In tutti i casi, la lesione è avvenuta durante attività sportiva ad un distanza media di 11 mesi (range, 9-14) dal primo intervento. Tre differenti LCA (controllo positivo) sono stati prelevati durante procedure di artroplastica di ginocchio. Tre differenti tibiali anteriori (allograft), lo stesso tipo di innesto utilizzato per le ricostruzioni del LCA, sono stati utilizzati come gruppo di controllo negativo. Ogni biopsia è stata analizzata mediante metodiche di microscopia luce ed elettronica a scansione per contare il numero di cellule e misurare il diametro, la densità e la percentuale dell’area delle fibrille collageniche. Risultati: Per tutte le variabili considerate è stata registrata una differenza significativa tra i gruppi AM e quelli PL e tra AM ed allograft (p < 0.05). Non è stata osservata nessuna differenza tra i gruppi AM ed LCA con l’eccezione della densità dell’area delle fibrille collageniche (p < 0.05). Sono state riscontrate differenze tra la densità e l’area delle fibrille collageniche tra i gruppi PL ed allograft e diametro, densità ed area delle fibrille collageniche tra i gruppi PL e LCA. Conclusioni: La presenza di cellule, la densità e la percentuale dell’area occupata dalle fibrille collageniche dei gruppi AM e PL quando confrontate con i gruppi di controllo dimostrano un’evoluzione degli innesti da tendine a legamento. Il gruppo AM appare più maturo del PL. I dati ottenuti suggeriscono che gli innesti sono ancora immaturi ad una media di 11 mesi dall’intervento. Solo studi prospettici randomizzati a lungo termine potranno dimostrare se una ricostruzione anatomica riproduce una struttura ed una ultrastruttura normale del LCA
Clinical relevance of static and dynamic tests after anatomical double-bundle ACL reconstruction.
No full textcomputer navigation system was used to collect kinematic data of 18 subjects undergoing ACL reconstruction. Surgical procedure was an anatomical four-tunnel hamstring double-bundle reconstruction. Static laxity and dynamic laxity were analyzed before and after graft passage and fixation. Correlations between static and dynamic laxities as well as with the preoperative IKDC score were determined. Static and dynamic laxities were significantly reduced after anatomic double-bundle ACL reconstruction (P 0.05). The preoperative IKDC score was only related to preoperative dynamic laxity (P < 0.01). The dynamic evaluation of pivot shift is able to better describe knee laxity, in particular rotational laxities and has no correlation with static laxity
Morphological analysis of failed double bundle ACL grafts.
No full textIntroduction
Recent clinical and biomechanical studies have demonstrated better results with double-bundle anterior cruciate ligament (ACL) reconstruction compared to single-bundle reconstruction. Little is known about the healing process after double bundle ACL reconstruction and nothing in case of failure. The purpose of this study was to analyze ACL double bundle graft remodeling process by evaluation of cell population and quantification of collagen fibril profiles in four traumatic failed grafts. These morphological appearances were then correlated to normal tendon allograft and ACL. The hypothesis of the study was that a different maturation process occurs between the two bundles.
Materials and Methods
Four ruptured ACL reconstructed remnants were obtained from 4 patients undergoing revision of the ACL surgery. In all cases the graft used for the primary reconstruction was tibialis anterior allograft. In 2 cases, both bundles were torn, with only the AM bundle in the remaining 2 cases. The average time between the primary surgery and the second trauma was 11 (9-14) months. Three intact ligaments (positive control group) was obtained from 3 patients (average age 64.3 years; 62-66) undergoing total knee arthroplasty. Biopsy specimens of 3 tibialis anterior tendon allografts were used as negative control group. Each biopsy was sheared longitudinally in two identical parts. The first sample was stained with Masson Trichrome and the cellular density of each specimen was estimated with light microscopy by counting the number of cells per mm2. The second sample was analyzed using transmission electron microscopy to measure the diameter of the collagen fibrils, the density (number of collagen fibrils per square micrometer), and the percentage area of collagen fibrils (% area occupied by total collagen fibrils relative to the cross-sectional area).
Results
There was a statistical difference between AM and PL groups and AM and allografts groups for all the variables analyzed (p < 0.05). No difference was observed between AM and ACL groups with exception of collagen fibrils density (p < 0.05). There were differences between PL and allograft groups exclusively for density and area of collagen fibrils and between PL and ACL groups for diameter, density and area of the collagen fibrils (p < 0.05).
Discussion
The presence of cells, the density and the percentage of area occupied by the fibrils of the two bundles when compared to control groups demonstrate an evolution of the grafts from tendon to ligament. The different maturation stage of the two bundles is suggested by the differences in all the variables considered. The AM portion appears more mature than the PL one. Our results suggest that the grafts are still immature at an average of 11 month postoperatively. This study has two limitations: we used as positive control group ACL from elderly patients and we didn’t compare our results to a single-bundle control group. Age-related changes occur on collagen fibrils, especially diameter size. It’s difficult to compare our results to single-bundle control group due to different variables such as surgical technique, fixation device, rehabilitation protocol and follow-up. Long term prospective randomized studies between single and double bundle reconstruction will likely demonstrate if an anatomic reconstruction is able to restore the normal structure and ultrastructure of the native AM and PL bundles
Double-bundle anterior cruciate ligament reconstruction: a comparative cadaver study of femoral tunnels performed with in-out and out-in techniques.
No full textIntroduction: Double bundle (DB) anterior cruciate ligament (ACL) reconstruction is nowadays a common procedure to manage ACL rupture. Many authors have reported in several short term follow-up prospective randomized studies a greater knee stability in DB reconstruction compared to single bundle. Despite several techniques reported in literature, as yet no study has demonstrated which DB technique has better outcomes. There are several factors that can influence biological integration of grafts and the bundle’s (anteromedial AM; posterolateral PL) mechanical behavior. The difference in diameter between tunnels on the intra-articular femoral side and graft is one of the most important. The aim of this study is to compare the diameter at the femoral tunnel entrance between two different techniques of DB ACL reconstruction in a cadaver model: the inside-out and the outside-in techniques.
Hypothesis: The hypothesis is that a difference exists, in terms of diameter at the femoral tunnel entrance, between the abovementioned techniques.
Materials and Methods: The study included 8 knees from 8 different cadavers divided into 2 groups. Group A: femoral tunnels were performed using an in-out technique: the PL tunnel from the AM portal and the AM tunnel from the transtibial PL tunnel. Group B: both tunnels were performed using an out-in technique with an out-in anatomical ACL guide system. All tunnels were drilled with a 7 mm acorn reamer. Upon cadaver dissection, the samples were evaluated by CT-scan on coronal and axial planes. The diameters of the two tunnels were measured on both planes.
Results: Tunnel convergence was never observed in the two planes. In group A, AM tunnel measured 7.07 mm (range 7 – 7.1) on axial plane and 7.02 mm (range 7 – 7.1) on coronal plane. In group B, AM tunnel measured 7.1 mm (range 7 – 7.2) on axial plane, and 7.15 mm (range 7 – 7.3) on coronal plane (p>0.05). In group A, PL tunnel measured 8.32 mm (range 8.2 – 8.4) on axial plane and 8.45 mm (range 8.4 – 8.5) on coronal plane. In group B, PL tunnel measured 7.15 mm (range 7 – 7.3) on axial plane and 7.02 mm (range 7 – 7.1) on coronal plane. (p<0.05).
Conclusions: Double bundle ACL reconstruction is a promising technique in terms of clinical results and knee stability. However, there has been some criticism concerning the procedure. Indeed, tunnel enlargement and tunnel communication could jeopardize a revision ACL surgery. Our study showed that the PL femoral tunnel entrance diameter is significantly larger in the inside-out than outside-in technique. Theoretically, the out-in technique should determine an inferior PL tunnel enlargement after ACL reconstruction. Several other variables such as type of graft, fixation and rehabilitation program should also be considered. Biomechanical and prospective randomized control studies between in-out and out-in techniques could confirm this hypothesis
The pivot shift: a global user guide
No full textPURPOSE: The use of several different maneuvers for the pivot shift test has resulted in inconsistent quantitative measurements. The purpose of this study was to describe, analyze, and group several surgeon-specific techniques for the pivot shift test and to propose a standardized pivot shift test. METHODS: Twelve expert surgeons examined a whole lower cadaveric extremity with their preferred technique and assigned a clinical grade, I-III. Anterior tibial translation and acceleration were measured using an electromagnetic system. The test was repeated after watching an instructional video focused on a standardized pivot shift technique. Measurements were repeated and compared with the preferred technique.
RESULTS: The expert surgeons utilized valgus stress unanimously in addition to fixed internal rotation (n = 5), fixed external rotation (n = 1), a motion-allowing technique (n = 3), a dislocation-type maneuver (n = 2), and a fixed anterior drawer type of maneuver in extension (n = 1). Anterior tibial translation measured was on average 15.9 ± 3.7 mm. Average tibial acceleration was 3.3 ± 2.1 mm/s(2). Average clinical grading was 2.3 ± 0.5. There were no differences in average clinical grading when using high stress (2.5 ± 0.6) versus low stress (2.3 ± 0.5, n.s.), or using fixed rotation (2.2 ± 0.5) versus a motion-allowing technique (2.3 ± 0.6; n.s.).CONCLUSIONS: Clinical grading, tibial translation, and acceleration vary between examiners performing the pivot shift test. High forces and extremes of rotation are not necessary to produce a clinical detectable pivot shift. In the future, a standardized pivot shift test-which can be performed universally and utilizes only gentle forces allowing motion to occur-may be beneficial when assessing differences in outcome following ACL reconstruction
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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