While the Stokes-Einstein ͑SE͒ equation predicts that the diffusion coefficient of a solute will be inversely proportional to the viscosity of the solvent, this relation is commonly known to fail for solutes, which are the same size or smaller than the solvent. Multiple researchers have reported that for small solutes, the diffusion coefficient is inversely proportional to the viscosity to a fractional power, and that solutes actually diffuse faster than SE predicts. For other solvent systems, attractive solute-solvent interactions, such as hydrogen bonding, are known to retard the diffusion of a solute. Some researchers have interpreted the slower diffusion due to hydrogen bonding as resulting from the effective diffusion of a larger complex of a solute and solvent molecules. We have developed and used a novel micropipette technique, which can form and hold a single microdroplet of water while it dissolves in a diffusion controlled environment into the solvent. This method has been used to examine the diffusion of water in both n-alkanes and n-alcohols. It was found that the polar solute water, diffusing in a solvent with which it cannot hydrogen bond, closely resembles small nonpolar solutes such as xenon and krypton diffusing in n-alkanes, with diffusion coefficients ranging from 12.5ϫ 10 −5 cm 2 / s for water in n-pentane to 1.15ϫ 10 −5 cm 2 / s for water in hexadecane. Diffusion coefficients were found to be inversely proportional to viscosity to a fractional power, and diffusion coefficients were faster than SE predicts. For water diffusing in a solvent ͑n-alcohols͒ with which it can hydrogen bond, diffusion coefficient values ranged from 1.75ϫ 10 −5 cm 2 / s in n-methanol to 0.364ϫ 10 −5 cm 2 / s in n-octanol, and diffusion was slower than an alkane of corresponding viscosity. We find no evidence for solute-solvent complex diffusion. Rather, it is possible that the small solute water may be retarded by relatively longer residence times ͑compared to non-H-bonding solvents͒ as it moves through the liquid.

Performance-enhancing substances (PESs) have unfortunately become ubiquitous in numerous sports, often tarnishing the spirit of competition. Reported rates of PES use among athletes are variable and range from 5 to 31%. More importantly, some of these substances pose a serious threat to the health and well-being of athletes. Common PESs include anabolic-androgenic steroids, human growth hormone, creatine, erythropoietin and blood doping, amphetamines and stimulants, and beta-hydroxy-beta-methylbutyrate. With recent advances in technology, gene doping is also becoming more conceivable. Sports medicine physicians are often unfamiliar with these substances and thus do not routinely broach the topic of PESs with their patients. However, to effect positive change in the sports community, physicians must educate themselves about the physiology, performance benefits, adverse effects, and testing methods. In turn, physicians can then educate athletes at all levels and prevent the use of potentially dangerous PESs.

Background: There is an ever-increasing demand for widespread implementation of patient-reported outcomes. However, adoption is slow owing to limitations in clinical infrastructure and resources within busy orthopaedic practices. Prior studies showed the single alpha-numeric evaluation (SANE) score to correlate at a single point in time with the American Shoulder and Elbow Surgeons (ASES) score. However, no study has validated the SANE in terms of test-retest reliability, responsiveness, or clinical utility. Purpose: To validate SANE with the ASES across a sample of patients with common orthopaedic shoulder diagnoses. Study Design: Cohort study (diagnosis); Level of evidence, 2. Methods: Patients undergoing rotator cuff repair (n = 77), total shoulder replacement (n = 55), or physical therapy (n = 80) for signs and symptoms of subacromial impingement syndrome (n = 61) or adhesive capsulitis (n = 19) were administered the SANE and ASES at baseline and again at their 3-month follow-up from initial care or surgery (N = 212, mean ± SD age = 52.6 ± 1.2 years, n = 145 women). Interclass correlation coefficient (ICC2,1) and standard error of the measurement (SEm) were used to evaluate the test-retest reliability of the SANE and the validity between the SANE and ASES scores. Analysis of variance (treatment group × time) was used to evaluate the responsiveness to treatment, and a receiver operating characteristic curve was used to establish the minimal clinically important difference (MCID) for the SANE as compared with the ASES (α = .05). Floor and ceiling effects were evaluated as the percentage of patients who scored the highest or lowest score on each tool. Results: The SANE demonstrated good pretreatment reliability (ICC2,1 = 0.84, SEM = 3.8), similar to the ASES (ICC2,1 = 0.82, SEM = 3.4). The SANE also showed good agreement with the ASES before and after treatment across all treatment groups (rotator cuff repair, ICC2,1 = 0.85, SEM = 3.4; total shoulder replacement, ICC2,1 = 0.72, SEM = 5.2; physical therapy: ICC2,1 = 0.82, SEM = 2.9). The SANE and ASES displayed similar responsiveness after treatment, with similar mean change and SD within each treatment group. The receiver operating characteristic curve revealed an area under the curve of 0.79 (SE, 0.62; P < .001) and a cutoff of 15% on the SANE, with a sensitivity of 85% to establish the MCID. Acceptable and similar floor and ceiling effects were observed for the ASES (4%) and SANE (9%). Conclusion: The study demonstrates that the SANE is valid for a range of common shoulder diagnoses to assess patient outcomes across operative and nonoperative treatment for shoulder complaints. The MCID of 15% is similar to that of the ASES (11%), suggesting that the SANE is a simple and efficient tool to assess treatment effects for shoulder disorders. Future studies are warranted to confirm these results and compare across other body parts and diagnoses.

ACL reconstruction is a cost-effective strategy for competitive athletes with an ACL injury.

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