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Background: Primary hemiarthroplasty of the shoulder is used to treat complex proximal humeral fractures, although the reported functional results following this method of treatment have varied widely. The aim of this study was to prospectively assess the prosthetic survival and functional outcomes in a large series of patients treated with shoulder hemiarthroplasty for a proximal humeral fracture. By determining the factors that affected the outcome, we also aimed to produce models that could be used clinically to estimate the functional outcome at one year following surgery.Methods: A thirteen-year observational cohort study of 163 consecutive patients treated with hemiarthroplasty for a proximal humeral fracture was performed. Twenty-five patients died or were lost to follow-up in the first year after treatment, leaving 138 patients who had assessment of shoulder function with use of the modified Constant score at one year postinjury.Results: The overall rate of prosthetic survival was 96.9% at one year, 95.3% at five years, and 93.9% at ten years.The overall median modified Constant score was 64 points at one year, with a typically good score for pain relief (median, 15 points) and poorer scores, with a greater scatter of values, for function (median, 12 points), range of motion (median, 24 points), and muscle power (median, 14 points). Of the factors that were assessed immediately after the injury, only patient age, the presence of a neurological deficit, tobacco usage, and alcohol consumption were significantly predictive of the one-year Constant score (p < 0.05). Of the factors that were assessed at six weeks postinjury, those that predicted the one-year Constant score included the age of the patient, the presence of a persistent neurological deficit, the need for an early reoperation, the degree of displacement of the prosthetic head from the central axis of the glenoid seen radiographically, and the degree of displacement of the tuberosities seen radiographically.Conclusions: Primary shoulder hemiarthroplasty performed for the treatment of a proximal humeral fracture in medically fit and cooperative adults is associated with satisfactory prosthetic survival at an average of 6.3 years. Although the shoulder is usually free of pain following this procedure, the overall functional result, in terms of range of motion, function, and power, at one year varies. A good functional outcome can be anticipated for a younger individual who has no preoperative neurological deficit, no postoperative complications, and a satisfactory radiographic appearance of the shoulder at six weeks. The results are poorer in the larger group of elderly patients who undergo this procedure, especially if they have a neurological deficit, a postoperative complication requiring a reoperation, or an eccentrically located prosthesis with retracted tuberosities.Level of Evidence: Prognostic study, Level II-1 (retospective study). See Instructions to Authors for a complete description of levels of evidence.

The epidemiology of a consecutive unselected series of adult distal humeral fractures is defined in this study. The majority of these fractures are best treated surgically by rigid open reduction and internal fixation, except for "low" Type A and C fractures, which have a higher risk of union complications. The role of total elbow arthroplasty to treat these more complex injuries requires further evaluation.

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Measurements of the thickness of the pre-corneal tear film, pre-lens tear film, post-lens tear film, and the lipid layer on the surface of the tear film are summarized. Spatial and temporal variations in tear film thickness are described. Theoretical predictions of tear film thickness are discussed. Mechanisms involved in the upward drift of the tear film after a blink, and in the formation of dry spots, are considered.

Among the ganglion cells in the rabbit's retina there is a class that responds to movement of a stimulus in one direction, and does not respond to movement in the opposite direction. The same directional selectivity holds over the whole receptive field of one such cell, but the selected direction differs in different cells. The discharge is almost uninfluenced by the intensity of the stimulus spot, and the response occurs for the same direction of movement when a black spot is substituted for a light spot.

Summary. To any dynamical system equipped with a metric, we associate a class of "well approximable" sets. In the case of an expanding rational map of the Riemann sphere acting on its Julia set, we estimate and in some cases compute the Hausdorff dimension of the associated "well approximabie" sets. The methods used show a clear link between distortion properties and the type of results obtained in this paper, via ergodic theory and ubiquity. Motivation and statements of the resultsConsider a metric space J equipped with a Borel probability measure/t. If T : J ~ J is measure preserving and ergodic, one knows by the Ergodic Theorem that for any ball B C J of positive measure, the subset {z E J : Tn(z) E B for infinitely many n E IN} of J has full Ft-measure. This means that the trajectories of almost all points will go through the ball B infinitely often. In general one can ask the question what happens if the ball B shrinks with time. More precisely if at time n one has a ball B(n) = B(zo, r(n)) centred at a point Zo E J of radius r(n) (r(n) ~ 0 as n --~ oo), then what kind of properties does the set of points z have, whose images Tn(z) are in B(n) for infinitely many n?These points can be thought of as trajectories which hit a shrinking target infinitely often. We shall call such points "well approximable" in analogy with the classical theory of metric Diophantine approximation [4,18] and its more recent extensions to the theory of discrete hyperbolic groups (see for example [7,13,21]). In the classical theory, the projective real line, F, U {cx~} is identified with the unit tangent space at a point of the modular surface IH/SL~(Z) (the modular group SL2(77) acts on the upper half plane model

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