Hip arthroscopy is associated with high patient satisfaction and good short-term outcomes, but there is a learning curve that we estimate to be approximately thirty cases.

Level I, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Recurrent patellofemoral instability is a disabling condition, attributed to a variety of anatomical aetiologies. Trochlear dysplasia, patella alta, an increased tibial tubercle trochlear groove distance of greater than 20 mm and soft tissue abnormalities such as a torn medial patellofemoral ligament and inadequate vastus medialis obliquus are all factors to be considered. Management of this condition remains difficult and controversial and knowledge of the functional anatomy and biomechanics of the patellofemoral joint, a detailed history and clinical examination, and an accurate patient assessment are all imperative to formulate an appropriate management plan. Surgical treatment is based on the underlying anatomical pathology with an aim to restore normal patellofemoral kinematics. We summarise aspects of assessment, treatment and outcome of patellofemoral instability and propose an algorithm of treatment.

No abstract

Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Experimental observations of the onset of convective motion in beds of inductively heated particles have been made. Data for the heat transfer coefficient were obtained from water-cooled beds of steel particles. The particulate beds were formed in a 10.4 cm dia glass jar, insulated at the bottom and on the sides. The free surface of a layer of water overlying the bed was maintained at a constant temperature by a copper plate cooled with tap water. In the experiments, the depths of the particulate bed and the overlying layer were varied. The observations showed that increasing the depth of the liquid layer over the bed tended to lower the critical internal Rayleigh number at which the onset of convection occurred. For overlying liquid layer-to-bed depth ratios of one or more, natural convection was observed to begin at R1 ≃ 11.5. The heat transfer data for RI > 11.5 are correlated with Nu = 0.190 RI0.69 However, with no liquid layer on top of the bed, natural convection was observed to occur at RI ≃ 46, which is slightly higher than observed in earlier studies made with Joule heating.

No abstract

IntroductionPlaster of Paris (PoP) impregnated bandages have been used to maintain the position of bones and joints for over a century. Classically, wool dressing is applied to the limb before the PoP, which can then be moulded to the desired shape. A modification of this practice is to wrap the PoP bandages circumferentially in cotton before wetting and applying to the patient in an attempt to reduce inhalation of plaster dust and reduce mess. However, this may affect the water content of the cast and therefore also its setting properties and strength. This study compared the setting properties of PoP casts when used with and without cotton wrapping.MethodsSixty specimens, compliant with the American Society for Testing and Materials standards for three-point bending tests, were prepared, with thirty wrapped in cotton. All were weighed before and after water immersion, and wrapped around a plastic cylinder to mimic limb application. Bending stiffness and yield strength was measured on a servohydraulic materials testing machine at 2, 6, 12, 24, 48 and 72 hours.ResultsThe water content of cotton-wrapped plaster was significantly higher (50%) than that of standard plaster. It had significantly lower strength up to 24 hours and significantly lower stiffness up to 72 hours.ConclusionsThe initial decrease in strength and stiffness of the cast wrapped in cotton may comprise the ability of the backslab to hold the joint or bone in an optimal position. Any modification of the standard plaster slab application technique should allow for the potential adverse effects on the plaster setting properties.