Biomedical subjects

Stephen J Ferguson

Publications and source records attributed to Stephen J Ferguson.

21 records · Page 2Linked to original sources

PubMed2002

Anterior fixation in the osteoporotic spine: cut-out and pullout characteristics of implants.

A new concept for the anchorage of anterior fixation implants in the osteoporotic thoracic and lumbar spine is presented. The SpiralBlade has been proposed as a suitable device for use in the osteoporotic spine, due to its broad, flat surface, which should provide resistance against cut-out of the implant through the vertebral body under dynamic loading. The cut-out and pullout characteristics of this implant were tested. The SpiralBlade was tested with and without a supplementary insertion guide screw. Two other commercial implants were tested for comparison: the VentroFix and the MACS-TL HMA (hollow monoaxial) screw. All implants were tested in osteoporotic human cadaveric vertebrae, using a modified in vitro testing protocol which simulated a full corpectomy model. Dynamic cyclic loading of 100 N, 200 N and 400 N was applied to the implant for 1000 cycles at each load level, and the subsidence of the vertebral body relative to the implant was measured. Following cyclic testing, the pullout strength of the implant was measured. No significant differences were found in the cut-out performance between the SpiralBlade with guide screw and the VentroFix. The SpiralBlade inserted without a guide screw was prone to cutting-out and a substantial loss of angular alignment of the vertebral body. Cut-out of the HMA screw was significantly greater than with the other implants. Two HMA screws fractured during testing. The VentroFix, with an average pullout force of 1166 N, has a significantly higher resistance to pullout than the SpiralBlade with guide screw (417 N), the SpiralBlade (332 N) and the Aesculap HMA screw (298 N). The SpiralBlade may be an alternative to anterior screw fixation in the osteoporotic spine, offering the same cut-out resistance with one implant rather than two screws.

Aged↗

PubMed2002

Biomechanical comparison of the sandblasted and acid-etched and the machined and acid-etched titanium surface for dental implants.

To make a direct biomechanical comparison between the sandblasted and acid-etched surface (SLA) and the machined and acid-etched surface (MA), a well-established animal model for implant removal torque testing was employed, using a split-mouth experimental design. All implants had an identical cylindrical solid-screw shape with the standard ITI thread configuration, without any macroscopic retentive structures. After 4, 8, and 12 weeks of bone healing, removal torque testing was performed to evaluate the interfacial shear strength of each surface type. Results showed that the SLA surface was more powerful in enhancing the interfacial shear strength of implants in comparison with the MA surface. Removal torque values of the SLA-surfaced implants were about 30% higher than those of the MA-surfaced implants (p = 0.002) except at 4 weeks, when the difference was at the threshold of statistical significance (p = 0.0519). The mean removal torque values for the SLA implants were 1.5074 Nm at 4 weeks, 1.8022 Nm at 8 weeks, and 1.7130 Nm at 12 weeks; and correspondingly, 1.1924 Nm, 1.3092 Nm, and 1.3226 Nm for the MA implants. It can be concluded that the SLA surface achieves a better bone anchorage than the MA surface, and that sandblasting before acid etching has a beneficial effect on the interfacial shear strength. As regards the bone-implant interfacial stiffness calculated from the torque-rotation curve, the SLA implants showed an overall more than 5% higher stiffness compared with the MA implants, although the difference did not reach the statistical significance level.

Acid Etching, Dental↗

PubMedDate not supplied

A new prosthetic design for proximal humeral fractures: reconstructing the glenohumeral unit.

A new shoulder prosthesis design for proximal humeral fractures has been developed. The rim of the articular component of this prosthesis has several holes to which the bone-tendon junction of the rotator cuff is fixed, to allow an anatomic reconstruction of the glenohumeral unit. The strength of the tuberosity fixation to this prosthesis is investigated in a cadaveric study. Artificial 4-part fractures were created in 18 human, fresh-frozen, paired shoulder joints with intact rotator cuffs. Two methods of tuberosity fixation were used in a matched-pair fashion. In group I the tuberosities were sutured to the rim of the prosthetic head, and in group II the tuberosities were circumferentially tension band-wired. Strength testing was performed on a material-testing machine, and displacement was recorded with an opto-electronic device. Both fixation methods proved to be equally reliable in the forces exerted during activities of daily living without significant displacement of the fracture fragments.

Aged↗