Shrinkage Procedure Research Articles

Application of bipolar radiofrequency energy in the treatmemt of elongated anterior cruciate ligament reconstruction

To introduce the application of bipolar radiofrequency energy in the treatment of elongated anterior cruciate ligament (ACL) reconstruction during arthroscopy. From January 2002 to June 2003, 12 cases whose anterior cruciate ligament reconstruction were elongated accepted the therapy of bipolar radiofrequency energy during arthroscopy. The 12 patients included 11 men and 1 woman with an average age of 30 years ranging from 18 to 45 years old. The ACL grafts were composed of 5 patellar tendons and 7 semitendinosus tendons. The elongated reconstruction were treated by bipolar radiofrequency energy with an output of 284W. This was continued until the elongated reconstruction were tight. After the operation, the patients received unlimited orthosis and were conducted to do functional exercise of the knees. All the patients were followed up. The Lysholm-Tegner score and clinical examination of the knees were recorded and analyzed statistically with paired t text. The elongated ACL reconstruction became shrinkage and tighten after treated by bipolar radiofrequency energy. The palpation by hook and Lachman test showed negative results. The follow-up time was 5-13 months, averaged 8 months. The postoperative mean Lysholm-Tegner score of the knee was 88.5, which was significantly higher than that of preoperative score of 45.5 (P < 0.01). All the patients had no postoperative complications. By application of bipolar radiofrequency energy, the elongated ACL reconstruction can be shrunk and tightened to make the knees stabilize. The shrinkage procedure is simple, convenient and effective.

Multivariate Bayes Wavelet shrinkage and applications

In recent years, wavelet shrinkage has become a very appealing method for data de-noising and density function estimation. In particular, Bayesian modelling via hierarchical priors has introduced novel approaches for Wavelet analysis that had become very popular, and are very competitive with standard hard or soft thresholding rules. In this sense, this paper proposes a hierarchical prior that is elicited on the model parameters describing the wavelet coefficients after applying a Discrete Wavelet Transformation (DWT). In difference to other approaches, the prior proposes a multivariate Normal distribution with a covariance matrix that allows for correlations among Wavelet coefficients corresponding to the same level of detail. In addition, an extra scale parameter is incorporated that permits an additional shrinkage level over the coefficients. The posterior distribution for this shrinkage procedure is not available in closed form but it is easily sampled through Markov chain Monte Carlo (MCMC) methods. Applications on a set of test signals and two noisy signals are presented.

A Study of Blockwise Wavelet Estimates Via Lower Bounds for a Spike Function

Abstract. A blockwise shrinkage is a popular adaptive procedure for non-parametric series estimates. It possesses an impressive range of asymptotic properties, and there is a vast pool of blocks and shrinkage procedures used. Traditionally these estimates are studied via upper bounds on their risks. This article suggests the study of these adaptive estimates via non-asymptotic lower bounds established for a spike underlying function that plays a pivotal role in the wavelet and minimax statistics. While upper-bound inequalities help the statistician to find sufficient conditions for a desirable estimation, the non-asymptotic lower bounds yield necessary conditions and shed a new light on the popular method of adaptation. The suggested method complements and knits together two traditional techniques used in the analysis of adaptive estimates: a numerical study and an asymptotic minimax inference.

Improved estimation of the mean in one-parameter exponential families with known coefficient of variation

The value for which the mean square error of a biased estimatoraT for the mean μ is less than the variance of an unbiased estimatorT is derived by minimizingMSE(aT). The resulting optimal value is 1/[1+c(n)v 2], wherev=σ/μ, is the coefficient of variation. WhenT is the UMVUE\(\bar X\), thenc(n)=1/n, and the optimal value becomes 1/(n+v 2) (Searls, 1964). Whenever prior information about the size ofv is available the shrinkage procedure is useful. In fact for some members of the one-parameter exponential families it is known that the variance is at most a quadratic function of the mean. If we identify the pertinent coefficients in the quadratic function, it becomes easy to determinev.

만성 외상성 견관절 전방 불안정성의 치료에서 병행한 관절낭 열 수축술

Purpose: In the traumatic anterior shoulder instability, the laxity of joint capsule and ligament is frequently demonstrated. Although a arthroscopic procedure to address anterior instability with joint capsular redundancy have generally provided good results, its recurrence rate is higher than open procedure. By reducing the capsular redundancy, thermal shrinkage is likely to improve the outcome of arthroscopic anterior stabilization. The objective of this study was to evaluate additional thermal capsular shrinkage as a treatment of joint capsular redundancy in anterior shoulder instability. Materials and Methods: From March 1999 to June 2000, 25 shoulders of 23 patients of recurrent anterior shoulder dislocation underwent arthroscopic Bankart repair with shrinkage procedure. The mean follow up was 29 months and average age at the time of operation was 26 years. Of these patients, 20 were male and 3 were female who had been experienced the average 8 times of dislocation before operation. Thermal shrinkage alone without Bankart repair was performed in two cases who did not have Bankart lesion. The clinical result was evaluated in according to Modified Rowe Score. Results: The Modified Rowe Score was improved from preoperative 35 points to postoperative 88 points. None of cases showed recurrence of dislocation. But, in two cases, temporary sensory hypesthesia of the axillary nerve was developed and in two cases of postoperative stiffness, arthroscopic capsular release and brisement were performed. Conclusion: Additional capsular shrinkage in arthroscopic technique to address recurrent anterior shoulder instability could treat effectively the capsular redundancy.

Analysis of blockwise shrinkage wavelet estimates via lower bounds for no-signal setting

A blockwise shrinkage is a popular procedure of adaptation that has allowed the statisticians to establish an impressive bouquet of asymptotic mathematical results and develop softwares for solving practical problems. Traditionally risks of the estimates are studied via upper bounds that imply sufficient conditions for a blockwise shrinkage procedure to be minimax. This article suggests to analyze the estimates via exact (non-asymptotic) lower bounds established for a no-signal setting. The approach complements the familiar minimax, Bayesian and numerical analysis, it allows to find necessary conditions for a procedure to attain desired rates, and it sheds a new light on popular choices of blocks and thresholds recommended in the literature. Mathematical results are complemented by a numerical study.

Confidence intervals for the effect of a prognostic factor after selection of an 'optimal' cutpoint.

When investigating the effects of potential prognostic or risk factors that have been measured on a quantitative scale, values of these factors are often categorized into two groups. Sometimes an 'optimal' cutpoint is chosen that gives the best separation in terms of a two-sample test statistic. It is well known that this approach leads to a serious inflation of the type I error and to an overestimation of the effect of the prognostic or risk factor in absolute terms. In this paper, we illustrate that the resulting confidence intervals are similarly affected. We show that the application of a shrinkage procedure to correct for bias, together with bootstrap resampling for estimating the variance, yields confidence intervals for the effect of a potential prognostic or risk factor with the desired coverage.

Volumetric change in the shoulder capsule after open inferior capsular shift versus arthroscopic thermal capsular shrinkage: a cadaveric model

The purpose of this study was to compare the percentage of glenohumeral intracapsular volume reduction after open inferior capsular shift and arthroscopic thermal capsulorrhaphy. Twelve matched, fresh-frozen cadaveric shoulders were used for the study. Intraarticular glenohumeral volume measurements were obtained by injecting a viscous fatty acid sulfate solution into the joint. In the 6 right shoulders, a standard anterior-inferior capsular shift was performed, and in the 6 matching left shoulders, an arthroscopic thermal capsular shrinkage was performed. After the procedures, the capsular volumes were re-measured. The open inferior shift procedure resulted in a mean decrease in glenohumeral volume of 50.2% (range, 43%-56%). Arthroscopic thermal capsulorrhaphy decreased shoulder intraarticular volume by a mean of 29.7% (range, 26%-36%). Both the open capsular shift and arthroscopic thermal shrinkage procedures produced well-documented volumetric reductions in the shoulder capsules. The open shift reduced intraarticular shoulder volume significantly more than arthroscopic thermal capsular shrinkage.

The posterior branch of the axillary nerve: an anatomic study.

Surgery on the posterior aspect of the shoulder has become accepted practice for a number of pathological conditions affecting the scapula and the glenohumeral joint. Despite this trend, the anatomy of the posterior branch of the axillary nerve has not been well characterized. The purpose of the present study was to determine the innervation pattern and surgical relationships of the posterior branch of the axillary nerve. Nineteen fresh-frozen human cadaveric forequarter amputation specimens were dissected through a posterior approach. The location of the posterior branch of the axillary nerve and its anatomical relationships with surrounding structures were documented and measured with use of digital calipers. The posterior branch separated from the main anterior circumflex branch of the axillary nerve immediately anterior to the origin of the long head of the triceps muscle at the six o'clock position on the glenoid. It coursed posteriorly, adjacent to the inferior aspect of the glenoid rim for an average distance of 10 mm (range, 2 to 17 mm) before dividing into the superior-lateral brachial cutaneous nerve and the nerve to the teres minor. The nerve to the teres minor coursed medially along the posterior aspect of the inferior part of the glenoid rim for an average distance of 18 mm (range, 11 to 25 mm) before entering the muscle at its inferior border. The superior-lateral brachial cutaneous nerve coursed inferiorly, deep to the posterior aspect of the deltoid. It became superficial by passing around the medial border of the muscle at an average of 8.7 cm (range, 6.3 to 10.9 cm) inferior to the posterolateral corner of the acromion. The posterior branch of the axillary nerve has an intimate association with the inferior aspects of the glenoid and shoulder joint capsule, which may place it at particular risk during capsular plication or thermal shrinkage procedures. The superior-lateral brachial cutaneous nerve and the nerve to the teres minor always arise from the posterior branch. Thus, loss of sensation over the deltoid may indicate loss of teres minor function. The posterior aspect of the deltoid has a more consistent supply from the anterior branch of the axillary nerve, necessitating caution when performing a posterior deltoid-splitting approach to the shoulder.

Failure of heat shrinkage for treatment of a posterior cruciate ligament tear

Incomplete tears or traumatic elongations of either the native cruciate ligaments or cruciate ligament reconstructions represent a therapeutic dilemma for orthopaedic surgeons. We report a case of a partially torn posterior cruciate ligament that was treated unsuccessfully with an electrothermal shrinkage procedure. Although the use of thermal energy to selectively shrink tissues may ultimately prove to be an invaluable tool, the lack of well-designed, randomized controlled studies to firmly establish its efficacy in the treatment of partial cruciate injuries mandates cautious use of this technique at this time.

Quantum-gravity analysis of gamma-ray bursts using wavelets

In some models of quantum gravity, space-time is thought to have a foamy structure with non-trivial optical prop- erties. We probe the possibility that photons propagating in vacuum may exhibit a non-trivial refractive index, by analyzing the times of flight of radiation from gamma-ray bursters (GRBs) with known redshifts. We use a wavelet shrinkage procedure for noise removal and a wavelet zoom technique to define with high accuracy the timings of sharp transitions in GRB light curves, thereby optimizing the sensitivity of experimental probes of any energy dependence of the velocity of light. We apply these wavelet techniques to 64 ms and TTE data from BATSE, and also to OSSE data. A search for time lags between sharp transients in GRB light curves in dierent energy bands yields the lower limit M 6:9 10 15 GeV on the quantum-gravity scale in any model with a linear dependence of the velocity of light/ E=M. We also present a limit on any quadratic dependence.

Narrowband acoustic Doppler volume backscattering signal .II. Spectral centroid estimation

For pt.I see ibid., vol.50, p.2644-2655 (2002). This paper proposes a novel algorithm to estimate the time-varying spectral centroid of the narrowband Doppler volume backscattering signal. It is constructed in a semi-parametric way, that is, modeling parametrically the local narrowband evolutionary spectrum using an AR(2) and nonparametrically adapting its time-varying coefficients using the wavelet shrinkage. The improved performance is gained by the underlying linear prediction function of the AR(2) and the minimax optimality of the unknown smoothness adaptation of the wavelet shrinkage procedure.

Inferior capsular shift for multidirectional instability following failed laser-assisted capsular shrinkage

This report is a prospective study of 10 consecutive patients treated by open inferior capsular shift following failed laser-assisted capsular shrinkage. Six patients had true multidirectional instability, 2 had anteroinferior instability with multidirectional laxity, and 2 had posteroinferior instability with multidirectional laxity. An anterior approach was used and a humeral-side capsular shift performed. The mean period of follow-up was 33 months (range, 18-47 months). On the basis of the Rowe system,9 patients had excellent results and 1 had a poor result at final follow-up. The mean score improved from 37.5 to 94 points on the Rowe scale, from 73 to 90.4 points on the Constant scale, and from 1.6 to 7.7 points on a numeric satisfaction scale (P <.001 for all). The one poor result was in the only patient who underwent multiple attempts at open stabilization prior to laser-assisted capsular shrinkage. There were no complications. We conclude that the results of an inferior capsular shift for multidirectional instability are not necessarily adversely affected by a previous failed laser-assisted capsular shrinkage procedure. (J Shoulder Elbow Surg 2002;11:305-8)

Births after vitrification at morula and blastocyst stages: effect of artificial reduction of the blastocoelic cavity before vitrification.

In 1996, with the introduction of sequential media, we set up a programme of cryopreservation of supernumerary morulae (day 4) and blastocysts (day 5) using a vitrification procedure. Our results showed that the efficiency of the vitrification method was dependent on the stage of embryo development and was negatively correlated with the expansion of the blastocoele. We postulated that a large blastocoele might disturb cryopreservative potential due to ice crystal formation during the cooling step. We analysed therefore the effectiveness of reducing before vitrification the volume of the blastocoelic cavity. Day 4 and day 5 embryos were vitrified in 40% ethylene glycol-18% Ficoll and 0.3 mol/l sucrose before plunging the straws directly into liquid nitrogen. Artificial shrinkage of the blastocyst was achieved after pushing a needle into the blastocoele cavity until it contracted. The survival rate post-thawing of day 4 and intact day 5 embryos was correlated with the volume of the blastocoele. In the control group only 20.3% blastocysts or expanded blastocysts survived as compared with 54.5 and 58.5% with morulae and early blastocyst respectively. After puncturing the blastocoelic cavity, an increase in the survival rate of up to 70.6% was noted. The pregnancy rates were improved after the artificial shrinkage procedure (20.5%) compared with the control intact blastocyst group (4.5%) (not significant). After reduction of the blastocoelic cavity, a significant increase in the implantation rate per vitrified blastocyst was observed (12.0 versus 1.4% P < 0.01). Our results showed that survival rates in cryopreserved expanded blastocysts could be improved by reducing the fluid content. This was presumably because mechanical damage caused by ice crystal formation was avoided. These observations should be considered when establishing a strategy and a protocol for cryopreservation of day 5 embryos.

Hyperopic refractive surgery.

Although the first attempts at hyperopia correction were made more than 100 years ago, it is only in the past several years that the success of hyperopic refractive surgery has begun to approach the efficacy of myopia surgery. Corneal surgery for the correction of hyperopia includes older lamellar techniques such as automated lamellar keratoplasty and epikeratophakia, and more recently photorefractive keratectomy and laser in situ keratomileusis. The latter two procedures have shown the most success. Using large diameter laser ablations and improved keratomes, laser in situ keratomileusis has become a realistic alternative for corrections of up to 4 or 5 diopters with astigmatic corrections. Laser thermal keratoplasty using the Holmium or diode laser and contact techniques also have gained popularity and shown some potential. Collagen shrinkage procedures are easy to perform and have relatively few complications, but over correction and regression are problems. Crystalline lens surgery and phakic intraocular lenses are being investigated actively and are promising; however, safety issues persist. The surgical treatments of hyperopia present a significant challenge and reward for the ophthalmic surgeon.

Variable Selection and Shrinkage: Comparison of Some Approaches

A common strategy within the framework of regression models is the selection of variables with possible predictive value, which are incorporated in the regression model. Two recently proposed methods, Breiman's Garotte (Breiman, 1995) and Tibshirani's Lasso (Tibshirani, 1996) try to combine variable selection and shrinkage. We compare these with pure variable selection and shrinkage procedures. We consider the backward elimination procedure as a typical variable selection procedure and as an example of a shrinkage procedure an approach of Van Houwelingen and Le Cessie (1990). Additionally an extension of van Houwelingens and le Cessies approach proposed by Sauerbrei (1999) is considered. The ordinary least squares method is used as a reference.With the help of a simulation study we compare these approaches with respect to the distribution of the complexity of the selected model, the distribution of the shrinkage factors, selection bias, the bias and variance of the effect estimates and the average prediction error.

Multiquadrant digital analysis of shoulder capsular thickness

Purpose: Nonablative thermal capsular shrinkage has been developed in an attempt to address the plastic capsule deformation thought to cause increased rates of recurrent instability following arthroscopic stabilization procedures. Although the temperature required to optimize collagen shrinkage is known, a safe depth of thermal penetration, in various locations about the shoulder capsule, has not been defined. The purpose of this study was to measure shoulder capsule thickness by quadrant and circumferentially from the glenoid to the humerus so that thermal energy in shoulder procedures can be more precisely applied to limit possible injury to pericapsular structures. Type of Study: This is an anatomic study using a cadaveric shoulder specimens. Materials and Methods: Soft tissue was dissected from 8 fresh cadaveric shoulders to isolate intact glenohumeral joint capsules. The humeral insertion was released and the capsule was cut into 6 longitudinal quadrants around the glenoid. The capsule specimens were then flash frozen and stored at −80°C. Quadrant tissue was cut into longitudinal sections 14 to 16 μm wide and stained with hematoxylin and eosin. The specimens were then digitized under a dissecting microscope and measured using computer imaging software at approximately 4-mm intervals. Two-way analysis of variance (ANOVA) was performed on the measurements of the intact capsule specimens 2.5 cm off the glenoid. Humeral insertion data were recorded separately. Results: A total of 248 separate measurements were made throughout the capsule in 8 specimens. Capsular thickness increased from an average of 2.42 mm anteriorly to 2.80 mm in the inferior capsular pouch and again thinned to 2.22 mm posteriorly. Global shoulder capsule thickness ranged from 1.32 to 4.47 mm. When analyzed by position, from glenoid to humerus, a general thinning was noted with a mean thickness of 3.03 mm at the glenoid to 2.17 mm at the humeral insertion. Two-way ANOVA showed a significant thickness variation along the specimen (P <.05), a nearly significant thickness variation with regard to quadrant (P <.03), and no significant interaction (P >.07) when applied to specimen measurements approximately 2.5 cm off the glenoid. Conclusions: The thickness of the shoulder capsule ranges from 1.32 to 4.47 mm, with a significant thinning laterally from the glenoid to the humerus. Further, capsule thickness ranges from 2.76 to 3.18 mm in the regions in closest proximity to the axillary nerve. These data may help determine the proper amount of thermal penetration necessary when performing shrinkage procedures and provide safety guidelines to limit the depth of thermal penetration to avoid possible injury to pericapsular structures.Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 16, No 5 (July), 2000: pp 457–461

Wavelet shrinkage for nonequispaced samples

Standard wavelet shrinkage procedures for nonparametric regression are restricted to equispaced samples. There, data are transformed into empirical wavelet coefficients and threshold rules are applied to the coefficients. The estimators are obtained via the inverse transform of the denoised wavelet coefficients. In many applications, however, the samples are nonequispaced. It can be shown that these procedures would produce suboptimal estimators if they were applied directly to nonequispaced samples. We propose a wavelet shrinkage procedure for nonequispaced samples. We show that the estimate is adaptive and near optimal. For global estimation, the estimate is within a logarithmic factor of the minimax risk over a wide range of piecewise Hölder classes, indeed with a number of discontinuities that grows polynomially fast with the sample size. For estimating a target function at a point, the estimate is optimally adaptive to unknown degree of smoothness within a constant. In addition, the estimate enjoys a smoothness property: if the target function is the zero function, then with probability tending to 1 the estimate is also the zero function.

Holmium:YAG Laser Thermokeratoplasty for Hyperopia and Astigmatism: An Overview

The holmium:YAG laser can be used to perform corneal collagen shrinkage and treat refractive errors. Studies are underway for the treatment of hyperopia by shrinking collagen in the peripheral cornea, which produces central and paracentral steepening. There is initial overcorrection followed by a regression of effect postoperatively, which appears to stabilize 4 to 6 months postoperatively. Refinement of current nomograms and definition of the amount of expected regression will enhance its accuracy. The holmium:YAG laser may be superior to radial thermokeratoplasty with a hot needle. Nearly 100 years ago, Lans was the first to report that heating of the cornea could induce collagen shrinkage with resultant corneal curvature changes. Various collagen shrinkage procedures have evolved since then. To date, the most well-known form of collagen shrinkage involves the hot needle and a technique developed by Fyodorov to do radial thermokeratoplasty for hyperopia. This article will review the current state of holmium:YAG laser technology and the advantages it may provide over radial thermokeratoplasty.

Collagen shrinkage procedures for keratoconus and corneal astigmatism.

Collagen shrinkage procedures for keratoconus and corneal astigmatism.