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Despite recent advances in total hip arthroplasty, proximal femoral resorption and osteopenia remain problems. To analyze the proximal strain effects of three different loading conditions, strains produced in intact and postarthroplasty femora have been compared. Ten adult cadaveric femora of similar size, shape, and rigidity were tested. Ten strain-gauge rosettes were positioned on each femur. To simulate the "single leg support" phase of gait, fixtures were developed to load the femora under three different configuration: the VS (vertical shaft) configuration, with a vertically orientated femur having rotational freedom proximally and distally; the ITB (iliotibial band) configuration of a femur with rotational freedom positioned 11 degrees from the vertical, with a strain-gauge adjustable metallic simulation of the lateral muscles of the thigh; and the ABD (abductor) configuration of a femur with rotational freedom positioned 11 degrees from the vertical, with a strain-gauge adjustable metallic simulation of the abductor muscles. Each femur was loaded less than or equal to 600 N through the medial point, located at one sixth of the transcondylar distance. Strain patterns and magnitudes produced by the three loading configurations were quite different in both the intact and postarthroplasty femora. Both the ITB and the ABD configurations resulted in greater proximal medial compression and lateral tension than did the VS configuration. The magnitudes of the proximal strains were significantly greater in the ABD configuration (p less than 0.05). Postarthroplasty femora showed similar proximal results. It is proposed that meaningful strain data for the physiologically loaded femur can be obtained only with simulations that include the forces produced by the iliotibial band. To overcome the indeterminate nature and biological variation in these forces, the studies have to consider a range of forces.

Cortical bone from the bovinefemur has been studied to determine any changes in dimensions that might be caused by dehydration and subsequent rehydration of the samples. Nine control and ten embalmed axially oriented parallelepiped samples were produced with nominal dimensions of 5 x 5 x 30 mm. Sequences of oven drying and rehydration were studied, before dehydration in a vacuum desiccator prior to determining ash weights. Vacuum dehydration caused anisotropic shrinkage with statistically different ( p < 0.000 I S ) mean strains of 9200, 27000 and 40 200 microstrain in the axial, circumferential and radial directions respectively. The corresponding mean strains for the embalmed samples were 7200, 21 400 and 34 000 microstrain ( p < 0.000 15). These strains are notably greater than the typically quoted 3000 microstrain peak associated with normal physiological activities. Rehydration of either the control or embalmed samples in isotonic saline did not reproduce the original radial or circumferential dimensions. Due to the small range of ash weights from 69.8 to 75.2 per cent, no meaningfiul correlation between ash weight and shrinkage could be extracted from the data. These findings have a potentially dramatic impact upon the design and conduct of all in vitro studies that use bone, whether fresh or embalmed.

While improvement in voiding symptoms and Quality of Life scores were maintained without the need for adjuvant treatment in approximately one third of men 5 years after TUMT, a significant number had required salvage therapies for symptom relief.