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Biomedical subjects

M Bowditch

Publications and source records attributed to M Bowditch.

6 recordsLinked to original sources
PubMed2002

Bone mineral density after the removal of intramedullary nails: a cross-sectional and longitudinal study.

We measured bone mineral density (BMD) using dual X-ray absorptiometry (DXA) at several sites in both fractured and nonfractured limbs in eight patients with femoral shaft fracture and six with tibial shaft fracture at the time of the intramedullary (IM) nail removal. Seven patients were followed up for an average of 13 months. The BMD at the proximal part of the femur and tibia was from 3% to 11% lower in the fractured side as compared to the nonfractured side. The greatest bone loss (13%-21%) was found in the operated distal tibia of the patients with tibial shaft fractures. At the fracture site of the femur, BMD was 10.5% ( P < 0.05) higher, possibly owing to fracture callus formation, whereas tibial shaft BMD was not increased. However, a calculated apparent volumetric BMDvol at the fracture site was 15%-16% decreased. Although BMDs of the fractured side almost reached the baseline level of the nonfractured side (96.9%-102.1%) by the final follow-up (>12 months), the absolute deficit was still 3%-9%. Surprisingly, significant BMD increases (5%-6%) were also detected in all proximal femoral measurement sites of the contralateral limb, which indirectly suggests that the uninjured limb may also suffer from bone loss after lower-extremity trauma. We conclude that clinically important bone loss exists in the proximal femur and proximal and distal tibia of the fractured limb at the time of IM nail removal. Although areal BMD was higher at the femoral fracture site, the lower apparent volumetric BMDvol suggests decreased mineralization and reduced strength of the fracture site. Although the present results do not suggest special recommendations for restricted weight bearing after the removal of IM nails, the relationship between decreased bone density and increased risk of fractures should be borne in mind.

Adolescent↗
PubMed2001

Is titanium so bad? Medium-term outcome of cemented titanium stems.

Early failures have seen titanium fall from favour as a material for cemented femoral stems. Between 1989 and 1994, we performed a prospective review of a consecutive series of 122 cemented total hip replacements using the Ultima straight textured titanium stem, and report the five- to ten-year clinical and radiological outcomes. There were no revisions for loosening of the femoral stem. Revision surgery was undertaken for other reasons such as dislocation, infection and loosening of the cup in 7.3%. Of those patients without revision all but two were satisfied with their hip, with 74% graded good or excellent using a modified Harris hip score. Radiological assessment revealed probable loosening in two. Although slight vertical subsidence was found in one-third of patients it had not progressed to loosening. It is not clear whether this represents debonding. Non-progressive radiolucent lines (1 to 2 mm) were present in zone 1 at the cement-prosthesis interface in 14.7%. Calcar resorption and hypertrophy around the distal stem were not often seen. With 97% survival at a mean of 7.5 years, the medium-term results of this specific cemented titanium stem are reassuring so far, but we are concerned about debonding and future failure.

Adult↗
PubMed1987

Effects of MHz ultrasound on electrical pain threshold perception in humans.

An electrode system was developed consisting of two 8 mm long 0.2 mm diameter silver-coated copper wires arranged parallel to each other 8 mm apart and held in contact with the skin by means of an acoustically transparent plastic adhesive tape. This system was attached to the upper arms of young adult volunteers who increased the voltage of the rectangular electrical pulses supplied to the electrodes until a reproducible sharp prickling pain sensation was perceived. A one inch diameter physiotherapy transducer was positioned over the electrode site so that ultrasound could be administered throughout the measurement period. The experiments were performed single blind to eliminate any subjective bias on the part of the volunteers. Preliminary experiments established that highly reproducible (+/- 3 to 4%) pain threshold perception values could be obtained, and that these values were not affected by changes in (a) the duration of the "on" time of the electrical pulses between 1.5 and 48 ms, (b) the contact pressure between the transducer and the electrode site, (c) the time interval between successive threshold measurements (providing that an unacceptable level of oedema was not produced around the electrodes), and (d) whether or not a test measurement was preceded by a control. Ultrasound exposure via a direct contact technique consistently produced a statistically significant (p less than 0.05) decrease in the perception threshold for electrical pain. This effect usually developed within 30-60 s and its magnitude increased both with increasing intensity (rising to 20.7 +/- 0.57% at an SATA intensity of 0.43 W/cm2 at 1.1 MHz) and with increasing frequency at the same ultrasonic intensity. Delivering the same amount of ultrasonic energy in the form of 2 ms bursts at several different peak intensities produced exactly the same reduction in pain threshold perception. These results indicate a thermal interaction mechanism, and similar threshold changes could be obtained by heating or cooling the electrode site by nonacoustic means. The inclusion of a thermocouple junction between the electrode wires showed that temperature increases of up to 10 degrees C could be produced when the transducer was in direct contact with the tape over the electrodes. The volunteers were not aware of these temperature increases which were primarily caused by heating of the transducer face. If the temperature of the skin surface is kept constant by interposing a thermostatted water path between the transducer and the electrode system, then similar ultrasound exposures had no detectable effects upon the electrical pain perception threshold.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗