Citations

A fracture healing monitoring system with external fixators was analysed using the finite element method. Pin displacement and side bar strain under axial and side loading were evaluated at various stages of simulated fracture healing. In general, a recovery of rigidity at the fracture site of up of 25 percent of intact bone could be sensitively predicted. Effects of cross-sectional distribution and length of callus at the fracture site on pin displacement and side bar strain were studied. Alterations of fixation configuration, such as component failure during the healing process, were found to have relatively little effect on pin displacement but a rather larger effect on side bar strain. In general, the assessment of fracture healing by monitoring the deformation of external fixation devices is a useful idea. However, in practice, great care must be taken to fully understand the implication of the monitoring system before drawing conclusions on such measurements.

Increasing application of expensive medical technologies, including joint replacement, is of concern in the current economic climate. Successful upper limb joint replacements (ULJRs) are being performed, but few detailed data about their utilization are available. To explore the resource implications of such surgery, the utilization of total shoulder replacement (TSR), total elbow replacement (TER) and total wrist replacement (TWR) were examined from the time these procedures first became available at the Mayo Clinic up to 1990. The age- and sex-adjusted utilization rate for TSR among Olmsted County, Minnesota, residents was 1.8 per 100000 person-years (p-y), 0.8 per 100000 p-y for TER and 1.1 per 100000 p-y for TWR. Overall utilization of primary ULJR among Olmsted County residents during the 19-year study period was 3.8 per 100000 p-y. The commonest indication for TSR was osteoarthritis (46 per cent) and for TER and TWR was rheumatoid arthritis (50 and 81 per cent respectively). There was no consistent trend in the utilization of these procedures among Olmsted County residents, but the number of referral patients receiving a ULJR at the Mayo Clinic increased steadily during the study period. The Mayo Clinic experience suggests an increasing demand for ULJR, particularly TSR and TER. With continued advances in, and diffusion of, the technology this demand may increase further.