Stresses in cement mantles of hip replacements: effect of femoral implant sizes, body mass index and bone quality

The effects of femoral prosthetic heads of diameters 22 and 28 mm were investigated on the stability of reconstructed hemi-pelves with cement mantles of thicknesses 1-4 mm and different bone qualities. Materialise medical imaging package and I-Deas finite element (FE) software were used to create accurate geometry of a hemi-pelvis from CT-scan images. Our FE results show an increase in cement mantle stresses associated with the larger femoral head. When a 22 mm femoral head is used on acetabulae of diameters 56 mm and above, the probability of survivorship can be increased by creating a cement mantle of at least 1 mm thick. However, when a 28 mm femoral head is used, a cement mantle thickness of at least 4 mm is needed. Poor bone quality resulted in an average 45% increase in the tensile stresses of the cement mantles, indicating resulting poor survivorship rate

Factors predicting outcome after whiplash injury in subjects pursuing litigation

Records of 277 patients presenting for medicolegal reporting following isolated whiplash injury were studied retrospectively. A range of pre-accident, accident and response variables were recorded. Multivariate analysis was used to determine the main factors that predict physical and psychological outcome after whiplash injury. The factors that showed significant association with poor outcome on both physical and psychological outcome scales were pre-injury back pain, high frequency of General Practitioner attendance, evidence of pre-injury depression or anxiety symptoms, front position in the vehicle and pain radiating away from the neck after injury. The strongest associations were with factors that are present before impact. In this selected cohort of patients, there is a physical and a psychological vulnerability that may explain the widely varied response to low violence indirect neck injury