Structural Materials: Understanding Atomic-Scale Microstructures

International audienceBACKGROUND The influence of rehabilitation on the outcomes after arthroscopic rotator cuff repair remains unknown. The purpose of this study was to compare clinical results and tendon healing rates following arthroscopic rotator cuff repair utilizing two distinct rehabilitation protocols. METHODS Over a thirty-month period, 124 patients under the age of sixty-five years underwent arthroscopic repair of a full-thickness rotator cuff tear measuring \textless30 mm in width. Postoperatively, patients were randomized either to a traditional rehabilitation program with early range of motion or to an immobilization group with delayed range of motion for six weeks. Clinical outcomes assessment included visual analog pain scale score, American Shoulder and Elbow Surgeons (ASES) score, Simple Shoulder Test (SST), relative Constant score, and strength measurements at six, twelve, and twenty-four months. Tendon integrity was assessed with ultrasonography at a minimum of twelve months postoperatively. RESULTS There were no significant differences in patient age, tear size, or measures of preoperative function between groups at baseline. Final clinical follow-up was available for 114 subjects (92%). Active elevation and external rotation were better in the traditional rehabilitation group at three months. No significant differences were seen in functional scores, active motion, and shoulder strength between rehabilitation groups at later time points. Functional outcomes plateaued at six or twelve months except for the relative Constant score, which improved up to twenty-four months following surgery. Ninety-two percent of the tears were healed, with no difference between rehabilitation protocols (p = 0.46). CONCLUSIONS Arthroscopic repair of small and medium full-thickness rotator cuff tears results in reliable improvements in clinical outcomes and a high rate of tendon integrity using a double-row repair technique in patients under the age of sixty-five years. There is no apparent advantage or disadvantage of early passive range of motion compared with immobilization with regard to healing or functional outcome

Microstructural Evolution of a Transformation in Which There Is an Exclusion Zone Around Each Nucleus

Depending on the physical circumstances, two nuclei might not form very close to one another. That is, there might be an exclusion zone around each nucleus. Formal treatments of nucleation and growth transformations normally suppose that nuclei are located uniform randomly, i.e. according to a Poisson point process, within the matrix. In this work, we model nuclei location in space using the so-called Sequential point process. The Sequential point process can produce a range of nuclei arrangements in space in which each nucleus possesses an exclusion radius. Computer simulations of transformations with these nuclei arrangements are compared with a transformation nucleated according to the usual Poisson point process. The resulting microstructural evolution is characterized by usual stereological parameters as well as by the two-point correlation function. The results show that the effect of the exclusion zone relative to the usual uniform randomly nucleation can be significant