Full Joint Research Articles

THREE CAST TECHNIQUES FOR THE TREATMENT OF EXTRA-ARTICULAR METACARPAL FRACTURES

Background: Most extra-articular metacarpal fractures can be managed nonoperatively. While the conventional wisdom is that the metacarpophalangeal joint should be immobilized in a position of flexion, alternative methods for cast immobilization have been described. The purpose of this study was to retrospectively evaluate three methods of closed treatment; specifically, we investigated whether the position of immobilization of the metacarpophalangeal joint or the absence of a range of motion of the interphalangeal joints affected the short-term outcome or fracture alignment. Methods: Between November 2000 and April 2004, extra-articular metacarpal fractures were immobilized for five weeks in one of three ways: with the metacarpophalangeal joints in flexion and full interphalangeal joint motion permitted (Group 1); with the metacarpophalangeal joints in extension and full interphalangeal joint motion permitted (Group 2); and with the metacarpophalangeal joints in flexion, the interphalangeal joints in extension, and no interphalangeal joint motion permitted (Group 3). Radiographs and the range of motion were evaluated at five weeks after application of the cast, and the range of motion and grip strength were assessed at nine weeks. Results: Two hundred and sixty-three patients met the inclusion criteria. At five weeks, there was no difference among the treatment methods with regard to the range of motion or the maintenance of fracture reduction. At nine weeks, there was no significant difference with regard to the range of motion or grip strength. Conclusions: When immobilization was discontinued by five weeks, the position of the metacarpophalangeal joints and the absence or presence of interphalangeal joint motion during the immobilization had little effect on motion, grip strength, or fracture alignment. This finding contradicts the conventional teaching that the metacarpophalangeal joint must be immobilized in flexion to prevent long-term loss of joint extension. Patient comfort, ease of application, and the surgeon's familiarity with the technique should influence the choice of immobilization. Level of Evidence: Therapeutic Level III. See Instructions to Authors for a complete description of levels of evidence.

Three Cast Techniques for the Treatment of Extra-Articular Metacarpal Fractures<sbt aid="961535">Comparison of Short-Term Outcomes and Final Fracture Alignments</sbt>

Most extra-articular metacarpal fractures can be managed nonoperatively. While the conventional wisdom is that the metacarpophalangeal joint should be immobilized in a position of flexion, alternative methods for cast immobilization have been described. The purpose of this study was to retrospectively evaluate three methods of closed treatment; specifically, we investigated whether the position of immobilization of the metacarpophalangeal joint or the absence of a range of motion of the interphalangeal joints affected the short-term outcome or fracture alignment. Between November 2000 and April 2004, extra-articular metacarpal fractures were immobilized for five weeks in one of three ways: with the metacarpophalangeal joints in flexion and full interphalangeal joint motion permitted (Group 1); with the metacarpophalangeal joints in extension and full interphalangeal joint motion permitted (Group 2); and with the metacarpophalangeal joints in flexion, the interphalangeal joints in extension, and no interphalangeal joint motion permitted (Group 3). Radiographs and the range of motion were evaluated at five weeks after application of the cast, and the range of motion and grip strength were assessed at nine weeks. Two hundred and sixty-three patients met the inclusion criteria. At five weeks, there was no difference among the treatment methods with regard to the range of motion or the maintenance of fracture reduction. At nine weeks, there was no significant difference with regard to the range of motion or grip strength. When immobilization was discontinued by five weeks, the position of the metacarpophalangeal joints and the absence or presence of interphalangeal joint motion during the immobilization had little effect on motion, grip strength, or fracture alignment. This finding contradicts the conventional teaching that the metacarpophalangeal joint must be immobilized in flexion to prevent long-term loss of joint extension. Patient comfort, ease of application, and the surgeon's familiarity with the technique should influence the choice of immobilization. Therapeutic Level III.

Modeling AC losses in the ITER NbTi poloidal field full size joint sample (PF-FSJS) using the THELMA code

A first validation of the full version of the thermal–hydraulic electromagnetic (THELMA) code, developed for the analysis of transients in the cable-in-conduit conductors and coils relevant for the International Thermonuclear Experimental Reactor (ITER) is presented here. THELMA includes electromagnetic models of the cable joints and terminations (lumped parameter) and of the conductor (distributed parameter), while for the thermal–hydraulics of the helium coolant it includes a compressible 1D flow model. The AC losses induced by a pulsed coil in the NbTi poloidal field full size joint sample (PF-FSJS) right leg conductor, tested in 2002 at the Sultan facility in Villigen (CH), are considered as test bed for this exercise. The computed energy deposition and evolution of the temperature downstream of the heated zone are in good agreement with the measured values. However, the inter-bundle electrical conductances needed in input by the code are compatible with measured values only when a sufficiently refined model is used in the cable cross-section.

Extended Correlation

What is the correlation between two variables? Traditional answers offer summary assessments such as Pearson’s r and regression coefficients. But new computing techniques make it possible to construct conceptually simple hypotheses that describe the full joint distribution of two variables, making it possible to “mine” the correlation for information that was previously unused. This article begins with evidence of systematic anomalies in the empirical joint distribution of height-weight data and follows with a hypothesis that explains these anomalies in terms of a theoretical joint distribution relative to a linear equation. The hypothesis has serious consequences because even in traditional examples, while it offers an improved fit to the data, its estimates of the linear center do not correspond to traditional least squares estimates of the linear relation for the same two variables.

Case studies in multivariate-to-anything transforms for partially specified random vector generation

This paper considers methods for sampling from random vectors characterized by marginal distributions and a correlation matrix, rather than a full joint distribution. The paper begins by describing the normal-to-anything (NORTA) transform for sampling from such random vectors. Limitations of the NORTA transformation motivate the development of a more general framework for partially specified random vector generation, and several alternatives to NORTA are described. NORTA and its alternatives are compared to a previous methodology for generating bivariate gamma random vectors; while each method considered generates random vectors with gamma marginals and appropriate correlations, both NORTA and its alternatives are shown to offer what could be considered to be more desirable joint distributional qualities. Finally, it is demonstrated that in the context of generating multivariate gamma random vectors some of the limitations of NORTA can in fact be overcome by considering its alternatives.

Design and Manufacture of a Full Size Joint Sample (FSJS) for the Qualification of the Poloidal Field (PF) Insert Coil

Within the framework of the European Fusion Programme a FSJS has been designed and manufactured by European Industry using PF coil NbTi superconductor manufactured and supplied by the Russian Federation as part of the R&D for the PF Conductor Insert (PFCI) coil. In addition to the superconductor, this sample contains a number of unique features. In contrast to other samples previously manufactured in Europe, the FSJS has used the Central Solenoid Model Coil (CSMC) joint design with NbTi conductor and a thick square jacket. One leg of the FSJS has had the conductor and sub-petal steel wraps removed before jacketing to assess the difference in the conductor performances between the two configurations. This paper will report on the development and manufacture of the FSJS, in particular the use of the Central Solenoid jacketing and swaging tools for compaction of the conductor and swaging of the joints, the preparation and qualification of the manufacturing route for the joint, the jacketing of a special length without conductor wraps and the high level of instrumentation required for the testing of the joint. The sample has been instrumented with more sensors than any other previous European sample, including temperature sensors, a large number of voltage taps for quench detection and Tcs measurements, quadrupoles to detect uneven voltage distribution, hall arrays for current distribution measurements and saddle coils.

Retrospective study of bacterial infective arthritis in 31 dogs

To characterise the presenting signs and pathological changes of canine bacterial infective arthritis in 31 dogs, and to document the response to different treatment regimens. Risk factors that may predispose joints to bacterial infective arthritis and influence the success of treatment were also investigated. A retrospective review of cases of bacterial infective arthritis that were presented to three university veterinary referral hospitals over a five-year period (January 1997 to January 2002) was performed. The elbow joint (38 per cent) and stifle joint (44 per cent) were most commonly affected. Radiographic changes consistent with pre-existing osteoarthritis were identified in 14 joints, which had no history of previous surgery (articular or periarticular) or penetrating wound. No significant difference (P = 0.78) was identified between the outcome of combined surgical and medical management, and medical management alone. There were trends for poorer outcomes with increased bodyweight of the dog, longer duration of lameness and a higher nucleated cell count of the affected joint fluid at presentation. The overall infection rate for articular surgical procedures at one institution was 1-3 per cent. Medical and/or surgical management were usually successful in resolving infection (94 per cent). However, they were frequently unsuccessful in restoring full joint function; this may in part have been due to the nature of the underlying joint

Confronting different models of community structure to species‐abundance data: a Bayesian model comparison

Species abundances are undoubtedly the most widely available macroecological data, but can we use them to distinguish among several models of community structure? Here we present a Bayesian analysis of species-abundance data that yields a full joint probability distribution of each model's parameters plus a relatively parameter-independent criterion, the posterior Bayes factor, to compare these models. We illustrate our approach by comparing three classical distributions: the zero-sum multinomial (ZSM) distribution, based on Hubbell's neutral model, the multivariate Poisson lognormal distribution (MPLN), based on niche arguments, and the discrete broken stick (DBS) distribution, based on MacArthur's broken stick model. We give explicit formulas for the probability of observing a particular species-abundance data set in each model, and argue that conditioning on both sample size and species count is needed to allow comparisons between the two distributions. We apply our approach to two neotropical communities (trees, fish). We find that DBS is largely inferior to ZSM and MPLN for both communities. The tree data do not allow discrimination between ZSM and MPLN, but for the fish data ZSM (neutral model) overwhelmingly outperforms MPLN (niche model), suggesting that dispersal plays a previously underestimated role in structuring tropical freshwater fish communities. We advocate this approach for identifying the relative importance of dispersal and niche-partitioning in determining diversity of different ecological groups of species under different environmental conditions.

多層溶接継手のクリープ変形挙動に及ぼす溶接金属部の不均一な高温強度特性の影響

Evaluation of creep properties of the welded joint through taking local fluctuation of the properties into consideration is experimentally or analytically seldom carried out. In this context, the purposes of the present study are to examine the surface strain distribution in the weld metal of a full thickness welded joint specimen and subsequently to investigate the local variation in the properties of the all-weld metal part of the joint using miniature specimens. A welded joint was prepared for 316FR steel plates by gas tungsten arc welding process using Mod. 316 filler wire. Creep tests were conducted at 823K in air using full thickness large welded joint specimens, HAZ and all-weld metal miniature specimens. By interrupting the creep test for the full thickness welded joint specimen, we observed the change in the uniaxial creep strain distribution in the weld metal in the thickness direction of the plate. The last layer of weld metal showed considerably larger creep strain than the central layers of the weld metal. The elastic-plastic creep analysis of the welded joint specimen by FEM was performed using these data. Finite element simulation performed for full-thickness welded joints provided creep strain distribution that is consistent with measured values. From the results above, it is concluded that the creep properties of weld metal in multi-pass, multi-layer welded joints strongly depend on the location of specimen sampling. It is necessary to take the fluctuation of material properties of a weld metal part into consideration when we perform simulation of creep deformation of a welded joint with sufficient accuracy.

Inequity Measures for Evaluations of Environmental Justice: A Case Study of Close Proximity to Highways in New York City

Assessments of environmental and territorial justice are similar in that both assess whether empirical relations between the spatial arrangement of undesirable hazards (or desirable public goods and services) and sociodemographic groups are consistent with notions of social justice, evaluating the spatial distribution of benefits and burdens (outcome equity) and the process that produces observed differences (process equity). Using proximity to major highways in New York City as a case study, we review methodological issues pertinent to both fields and discuss choice and computation of exposure measures, but focus primarily on measures of inequity. We present inequity measures computed from the empirically estimated joint distribution of exposure and demographics and compare them with traditional measures such as linear regression, logistic regression, and Theil's entropy index. We find that measures computed from the full joint distribution provide more unified, transparent, and intuitive operational definitions of inequity and show how the approach can be used to structure siting and decommissioning decisions.

Acromion-fixation of glenoid components in total shoulder arthroplasty

Successful design of components for total shoulder arthroplasty has proven to be challenging. This is because of the difficulties in maintaining fixation of the component that inserts into the scapula; i.e., the glenoid component. Glenoid components that are fixated to both the glenoid and acromion (a long process extending medially on the dorsal aspect of the scapula) have the possible advantage of greater stability over those that are fixated to the glenoid alone. In this study, a finite element analysis is used to investigate whether or not acromion fixation is advantageous for glenoid components. Full muscle loading and joint reaction forces are included in the finite element model. Reflective photoelasticity of five scapulae is used to obtain experimental data to compare with results from the finite element analysis, and it confirms the structural behaviour of the finite element model. When implanted with an acromion-fixated prosthesis, it is found that high unphysiological stresses occur in the scapula bone, and that stresses in the fixation are not reduced. Very high stresses are predicted in that part of the prosthesis which connects the acromion to the glenoid. It is found that the very high stresses are partly in response to the muscle and joint reaction forces acting at the acromion. It is concluded that, because of the relatively high forces acting at the acromion, fixation to it may not be the way forward in glenoid component design.

The large-sample distribution of the most fundamental of statistical summaries

We consider one of the most fundamental of statistical problems, namely that of inference for the mean, standard deviation and coefficients of skewness and kurtosis of an unknown univariate distribution. Assuming the distributional form of the parent population to be unknown, we focus our attention on moment-based inference. As is well-known, the method of moments estimates of the population measures under consideration are the sample mean, standard deviation and coefficients of skewness and kurtosis. Despite being some of the most frequently used of all statistical summaries, it comes as a surprise to find that their full joint distribution has not previously been studied in the literature. We derive a very general theoretical result for the large-sample asymptotic joint distribution of the four estimators and use simulation to explore the validity of the result as a means of approximating the biases, variances and covariances of the estimators for finite sample sizes. The theoretical result is then used to obtain asymptotically distribution-free inferential procedures for the population measures of original interest. Specifically, we propose and investigate the efficacy of bias-corrected and non-bias-corrected methods for point estimation and confidence set construction. We also discuss the relevance of the developed methodology both as an end in itself and as an aid to model formulation.

Characteristics of the gluteus medius muscle in an asymptomatic patient with radiographic signs of coxarthrosis.

This case study describes the micromorphology and some biochemical features of gluteus medius muscle in a 79-year-old woman with radiographic signs of coxarthrosis but with no clinical symptoms who initially was admitted in the orthopaedic emergency service with a non-displaced subcapital fracture of the femoral neck due to a domestic accident (fall). The X-ray of the hip showed some characteristic features of coxarthrosis, classified grade 2 of the Kellgren criteria. After informed consent, it was decided to carry out the functional evaluation according to the indexes of Lequesne and WOMAC (Western Ontario and McMaster Universities Osteoarthritis Index) and to take a biopsy of the gluteus medius muscle for microscopical examination and myosin heavy chain isoform identification during hip replacement surgery. For the Lequesne Index (score 0-24), the total score was 0, and for the WOMAC (score 0-96), the total score was also 0, both speaking in favour of full joint and muscle function. All the structural features observed in muscle were considered not to have any pathological relevance. The composition of the myosin heavy chains in the gluteus medius muscle was 48% MHC I, 41% MHC IIa, and 11% MHC IIx. The muscle characteristics do not support earlier concepts about muscle weakness as a predisposing factor for osteoarthritis. It is moreover concluded that the diagnosis should rather consider clinical symptoms than radiographic signs of osteoarthritis.

ミニチュア溶接金属および大形溶接継手試験片による３１６ＦＲ溶接金属のクリープ特性の評価

In order to examine the distribution of creep properties in a 316FR weld metal, a narrow gap welded joint was prepared from 50mm thick 316FR steel plates by gas tungsten arc welding (GTAW) process using type 316 filler wire, and constant-load creep rupture tests were conducted at 823K in air using full thickness large welded joint specimens and pure weld metal miniature specimens. The latter specimens were taken parallel to the weld line of 316FR weld metal in the welded joint. Specimen sampling locations were the plate surface, the 1/4 and the 1/2 plate thickness positions from the surface. By interrupting the creep test for the full thickness welded joint specimen, we observed the change in creep strain distribution in the weld metal in the thickness direction of the plate. The last layer of weld metal showed considerably larger creep strain than the central layers of the weld metal. Further, the creep strength of weld center is larger than that of the top of the weld. The cause of this difference in the creep strength in the weld metal is that due to large thermal expansion coefficient and small thermal conductivity of austenitic stainless steel strain introduced through thermal histories was larger in the central part than in the vicinity of the surface of the welded joint. Hardness variation in the weld metal and the results of transmission electron microscopic examination revealing dislocation configuration support this speculation. From the results above, it is concluded that the creep properties of weld metal in multi-pass, multi-layer welded joints strongly depend on the location of specimen sampling.

Problems and Techniques

With major elections in many countries during 2004, what could be more timely than the two papers in this SIAM Review issue about preferential voting---the Survey and Review paper by Roberto Serrano and our first Problems and Techniques article, "Single Transferable Votes with Tax Cuts," by Eivind Stensholt? In the Problems and Techniques paper, the author begins by explaining the philosophy and strategy of different ways to tally preferential votes, giving sometimes surprising illustrations of their strengths and weaknesses. Even using the "single transferable vote" (STV) systems described in the paper, which are designed to avoid certain defects of other systems, there will always be collections of individual preference relations that allow election manipulation---for example, under some conditions a voter can actually hurt candidate x by giving x the top rank. A further wrinkle is learning how a "tax cut" (not income tax...) can be included to address the "free ride" problem, in which some voters end up with more influence than others. The paper includes data from a real case of preference voting, analyzing (among several interesting insights) the situation of an "anti-establishment" voter. Moving from voting to fundamental numerical algorithms in scientific and engineering applications, our second paper, by Leslie Greengard and June-Yub Lee, concerns acceleration of the nonuniform fast Fourier transform (FFT). For applications with an irregular sampling of data in the frequency domain---for example, image reconstruction or radio astronomy---the standard FFT is inappropriate because it requires uniform sampling. Greengard and Lee stress that three separate issues arise in reconstructing functions from nonuniform data in the Fourier domain: acquisition of data, choice of a quadrature scheme, and existence of a fast algorithm for computing the discrete transform. Given that a quadrature approach has been chosen, the authors describe techniques for rapid and accurate computation of the needed discrete sums---in effect, combining an interpolation scheme with the standard FFT by replacing a Dirac delta function source with a sharply peaked Gaussian function, thereby "smearing" the source strength onto a regular grid. An especially interesting part of the paper is its characterization of fast Gaussian gridding, which relies on the fact that the values to be evaluated are negligible except at nearby grid points. Numerical examples are included that verify the speed and accuracy of the proposed method, illustrate the benefits of fast gridding, and display results on the ubiquitous Shepp--Logan phantom. The third paper, "Symplectic Rotational Geometry in Human Biomechanics," by V. Ivancevic, begins with informative background on the study of human motion, characterized by complex, multidimensional, highly nonlinear, and hierarchical dynamics---i.e., a very difficult problem! Classical biomechanics relies on vector geometry for the more than six hundred skeletal muscles, each generating forces and torques. With the widely used technique of inverse dynamics, segmental movements are measured using motion capture, often combined with other sensor data. For the more unusual forward dynamics approach, in which translational and rotational motion are simulated based on joint forces and torques, the author proposes the formalism of rotational symplectic geometry. A review of symplectic geometry in manifolds leads to an analysis of how different features of human motion (such as humanoid joint angles, "hinge" joints, and "ball-and-socket" joints) can be modeled in terms of constrained Lie groups, followed by a mathematical tour of (among other topics) segment dynamics, full body dynamics, joint dynamics, and muscular dynamics. We thank the authors of all three papers for proving by example the rich variety of the Problems and Techniques section.

Composite Conditional Likelihood for Sparse Clustered Data

SummarySparse clustered data arise in finely stratified genetic and epidemiologic studies and pose at least two challenges to inference. First, it is difficult to model and interpret the full joint probability of dependent discrete data, which limits the utility of full likelihood methods. Second, standard methods for clustered data, such as pairwise likelihood and the generalized estimating function approach, are unsuitable when the data are sparse owing to the presence of many nuisance parameters. We present a composite conditional likelihood for use with sparse clustered data that provides valid inferences about covariate effects on both the marginal response probabilities and the intracluster pairwise association. Our primary focus is on sparse clustered binary data, in which case the method proposed utilizes doubly discordant quadruplets drawn from each stratum to conduct inference about the intracluster pairwise odds ratios.

A cadaveric study examining acromioclavicular joint congruity after different methods of coracoclavicular loop repair

A basic principle in the treatment of joint injuries is to restore congruity with the hope that restoration may lessen the incidence of late arthritis. The acromioclavicular (AC) joint is frequently injured. Many AC joint injuries are treated nonoperatively; others are treated surgically. Coracoclavicular loop repair of the AC joint is believed to lead to anterior displacement of the clavicle relative to the acromion. This cadaveric study evaluated the effectiveness of three techniques of coracoclavicular loop repair in restoring AC joint congruity through measurement of anterior displacement. Fourteen shoulders were repaired by the three different techniques, all of which consisted of fixation through a drill hole in the clavicle and around the crook of the coracoid with a suture. The techniques only varied by the placement of the drill hole in the clavicle (ie, either posterior, middle, or anterior). The results of this study indicate that as the drill hole moved anteriorly on the clavicle, joint congruity was more closely approached and less anterior displacement of the clavicle occurred. However, none of the methods of coracoclavicular loop fixation restored full AC joint congruity.

The use of debrided human articular cartilage for autologous chondrocyte implantation: maintenance of chondrocyte differentiation and proliferation in type I collagen gels

Autologous chondrocyte implantation (ACI) is the most promising surgical treatment for large full thickness knee joint articular cartilage (AC) defects where cells from healthy non-weight bearing area AC are multiplied in vitro and implanted into such defects. In the routine surgical procedure for symptomatic knee full thickness AC defects, damaged AC surrounding the edge and the base of such defects is usually debrided and discarded. The purpose of this study was to examine if chondrocytes from this ‘debrided’ AC can proliferate, synthesize a cartilage specific matrix and thus can be used for ACI. Methods: Biopsies were retrieved from 12 patients (debrided articular cartilage: DAC, aged 35–61) and from two autopsies (normal articular cartilage: NAC, aged 21 and 25). Chondrocytes were isolated, seeded at low density in type I collagen gels and as monolayer cultures for 4 weeks without passage. Results: After 4 weeks cultures in type I collagen gels, cell proliferation from DAC (18.34 ± 1.95 fold) was similar to cells from NAC (11.24 ± 1.02 fold). Syntheses of proteoglycan and collagen in DAC were also similar to NAC. Newly synthesized matrices in gel cultures consisted predominantly of type II collagen as shown by immuno-labelling and SDS-PAGE followed by fluorography. Chondrocytes from ‘debrided human AC’ cultured at low density in type I collagen gels may be used for the ACI procedure as they provide sufficient viable cell numbers for ACI and maintain their chondrocyte phenotype as they synthesize a cartilage-like matrix.

Comparing Harm Done by Mobility and Class Absence: Missing Students and Missing Data

This article addresses the relationship between academic achievement and the student characteristics of absence and mobility. Mobility is a measure of how often a student changes schools. Absence is how often a student misses class. Standardized test scores are used as proxies for academic achievement. A model for the full joint distribution of the parameters and the data, both missing and observed, is postulated. After priors are elicited, a Metropolis-Hastings algorithm within a Gibbs sampler is used to evaluate the posterior distributions of the model parameters for the Pittsburgh Public Schools. Results are given in two stages. First, mobility and absence are shown to have, with high probability, negative relationships with academic achievement. Second, the posterior for mobility is viewed in terms of the equivalent harm done by absence: changing schools at least once in the three year period, 1998–2000, has an impact on standardized tests administered in the spring of 2000 equivalent to being absent about 14 days in 1999–2000 or 32 days in 1998–1999.

Hyaluronan Synthases in Normal and Regenerating Joint Cartilage

Repair of full thickness joint cartilage defects is within reach of routine clinical practice. The quality of regenerating hyaline cartilage, however, is difficult to assess. Synthesis of an extracellular matrix with high hyaluronan content is crucial for its metabolic and functional properties. We studied hyaluronan synthase (HAS) expression in knee joints of adult sheep as a novel cellular marker for chondrocyte function. Six house-bred Merino sheep (age 4–6 years) underwent two-stage surgery of their femoral condyles for autologous chondrocyte transplantation (ACT). First, cells were isolated from biopsies and expanded in vitro for 2 weeks using standard culture techniques. In a second session, three defects were made and either left untreated, covered with periosteal flap alone, or in combination with chondrocyte suspensions injected under the flaps. After 16 weeks, biopsies were taken from the operated knees at the defect sites and from the untreated condyle. Specimens were processed for safranin O and electron microscopy, and for immunofluorescence using three different polyclonal anti-HAS antibodies recognizing one or all of the three known mammalian HAS. Control and regenerating tissues were compared regarding their morphology and the expression of HAS, in relation to collagens type I and II, and adult cartilage proteoglycan core protein. In comparison with untreated defects or with periosteal flap alone, ACT provided a neocartilage with better-differentiated morphology. In healthy joint cartilage, about 50% of the chondrocytes expressed HAS, independent of antibody. Following ACT, a higher density of chondrocytes was observed, of which more than 75% expressed HAS, whereas the regenerates without ACT showed a lower density of HAS-expressing cells. We propose to use HAS immunofluorescence as an additional marker of matrix synthesis by chondrocytes and joint cartilage regeneration.