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Biomedical subjects

Victor Valderrabano

Publications and source records attributed to Victor Valderrabano.

2 recordsLinked to original sources

Total ankle replacement.

Total ankle replacement is emerging as a viable treatment for symptomatic ankle arthritis that has not responded to nonoperative treatment. Most modern implant designs involve the use of a three-component, mobile-bearing implant. Although the results of the different design approaches are encouraging in limited clinical series, there is still the need for careful, long-term analyses to estimate to what extent the current designs are mimicking the biomechanics of the ankle joint. More attention must be paid to more accurate implantation techniques that result in a well-balanced ligament and allow the ligaments to act together with the replaced surfaces in a most physiologic manner. To improve the stability of the bone-implant interface over time, specific efforts should be made to better understand the extrinsic and intrinsic forces of the ankle joint, including the forces that are created by the prosthesis itself.

Ankle Joint↗

Influence of screw type on obtained contact area and contact force in a cadaveric subtalar arthrodesis model.

The purpose of this study was to compare the compression effect of the 7.0-AO screw and the 6.5 mm Ideal Compression Screw (I.CO.S.) screw in an in vitro subtalar arthodesis model. Six fresh-frozen, human cadaver foot specimens were obtained for analysis. The subtalar joint was opened laterally without affecting the articular surfaces. ATekscan 5051 sensor with a maximum pressure of 250 PSI and a sensel-density of 62 sensel/sq-cm was placed into the joint, which allowed for continuous measurement of the contact area and contact forces achieved by one 7.0 AO-screw, and thereafter by one 6.5 I.CO.S.-screw. When tightening the screw, mean contact area increased by 0.21 cm2 for the AO-screw (p<0.05), and by 0.27 cm2 for the I.CO.S.-screw (p>0.05). When comparing the tightened AO-screw and I.CO.S.-screw, mean contact area increased from 1.40 cm2 to 1.97 cm2 (p<0.05). The mean contact force also increased when tightening the screws. This increase was 7.6 N for the AO-screw (p<0.05) and 14.8 N for the I.CO.S.-screw (p>0.05). When comparing the tightened AO-screw and I.CO.S.-screw, mean contact force increased from 54.9 N to 81.7 N (p<0.05). The obtained results have shown that the design of the screw influences the achieved compression force. The superior compression of the I.CO.S.-screw might be explained by the better gripping and additional compression mechanism of its head. The shape of the head of the cannulated AO-screw, in contrast, may be critical to resist against the weak cortical bone of the calcaneus, i.e. it can sink into soft bone resulting in a loss of compression force.

Aged↗