Biomedical subjects

Valentin Antoci

Publications and source records attributed to Valentin Antoci.

11 recordsLinked to original sources

PubMed2007

Selfprotective smart orthopedic implants.

In this review, we discuss current advances leading to an exciting change in implant design for orthopedic surgery. The initial biomaterial approaches in implant design are being replaced by cellular-molecular interactions and nanoscale chemistry. New designs address implant complications, particularly loosening and infection. For infection, local delivery systems are an important first step in the process. Selfprotective 'smart' devices are an example of the next generation of orthopedic implants. If proven to be effective, antibiotics or other active molecules that are tethered to the implant surface through a permanent covalent bond and tethering of antibiotics or other biofactors are likely to transform the practice of orthopedic surgery and other medical specialties. This new technology has the potential to eliminate periprosthetic infection, a major and growing problem in orthopedic practice.

Antibiotic Prophylaxis↗

PubMed2006

Axial deformity correction in children via distraction osteogenesis.

We performed a retrospective analysis of the results of 62 tibial and 54 femoral lengthenings in 88 consecutive patients. The patients mean age was 13.5 years and mean follow-up was four years. There was a significant difference between metaphyseal (27+/-1.2 days/cm) and diaphyseal (39.4+/-1.7 days/cm), tibial (34+/-1.7 days/cm) and femoral (31+/-1.4 days/cm) lengthening (P<0.05), but no significant difference among the lengthening indexes when treating one-, two-, or three-dimensional deformities, congenital (34+/-2.4 days/cm) and acquired (32+/-1.0 days/cm) limb length discrepancy (LLD) (P>0.05). The lengthening index was 33+/-1.1 days/cm, distraction regenerate length 6+/-0.4 cm, and lengthening percentage 21+/-2.1. The scatter plots of new regenerate length against time and the scatter plots of neurological complication, residual deformities, broken pins, joint contractures, and hypertension rate against lengthening percentage showed a positive linear relationship (r=0.8). We found the correlations between quantitative and qualitative parameters that should help to predict the treatment outcomes. Lengthening index depends on the amount of length gained. Higher length of new bone regenerate leads to a decrease in lengthening index. Expected gain in bone length can aid in estimating the duration of treatment. The lengthening percentage correlates very well with the complication rate and can be used to predict the complication rate.

Adolescent↗

PubMed2005

Vancomycin covalently bonded to titanium beads kills Staphylococcus aureus.

Periprosthetic infections are life-threatening complications that occur in about 6% of medical device insertions. Stringent sterile techniques have reduced the incidence of infections, but many implant patients are at high risk for infection, especially the elderly, diabetic, and immune compromised. Moreover, because of low vascularity at the site of the new implant, antibiotic prophylaxis is often not effective. To address this problem, we designed a covalent modification to titanium implant surfaces to render them bactericidal. Specifically, we aminopropylated titanium, a widely used implant material and extended a tether by solid phase coupling of ethylene glycol linkers, followed by solid phase coupling of vancomycin. Vancomycin covalently attached to titanium still bound soluble bacterial peptidoglycan, reduced Staphylococcus aureus colony-forming units by 88% +/- 16% over 2 hr, and retained antibacterial activity upon a repeated challenge.

Anti-Bacterial Agents↗

PubMed2005

The effect of transfixion wire crossing angle on the stiffness of fine wire external fixation: a biomechanical study.

To analyse the effect of transfixion wire-crossing angle on the stiffness of fine wire external fixation, a laboratory investigation using a fibreglass tibia fixed into an idealised fixator was performed with a servohydraulic test frame. Load-deformation behaviour was compared at the different wire-crossing angles (30 degrees -90 degrees ) under identical conditions of central axial compression, medial compression-bending, posterior compression-bending, posteromedial compression-bending, and torsion. Stiffness values were calculated from the load-deformation and torque-angle curves. The increase in wire-crossing angle led to an overall increase in the stiffness, except medial bending stiffness. The wire-crossing angle of 90 degrees provided significantly greater stiffness than all other angles in all load configurations (p<0.05) except medial bending. In medial bending, the wire-crossing angle of 30 degrees provided significantly greater stiffness than all the other angles (p<0.05). Increasing wire-crossing angle from 30 degrees to 90 degrees contributed to an overall increase of 75% in external fixation stiffness, which included axial, torsional, and bending stiffness, but bending stiffness was a function of the wire positioning with respect to the loading axis. Therefore, using the widest possible wire-crossing angle and placing wires as close to the loading plane as possible can increase the stiffness of external fixation.

Biomechanical Phenomena↗

PubMed2005

The effect of wire plane tilt and olive wires on proximal tibia fracture fragment stability and fracture site motion.

To analyze the effect of the tilt angle relationship between the crossed wire plane and the bone axis on the stiffness of fine wire external fixation, load-deformation behavior was compared across different tilt angles (0 degree, 10 degrees, and 20 degrees) of the plane containing crossed smooth or olive wires under identical conditions of central axial compression, medial compression-bending, posterior compression-bending, posteromedial compression-bending, and torsion. Stiffness values were calculated from the load-deformation and torque-angle curves. A tilt angle of 20 degrees with olive wires provided significantly greater stiffness compared to smooth wires at any angle in any loading condition (p < 0.05). A tilt angle of 20 degrees with olive wires was also significantly more stiff than a tilt angle of 0 degree with olive wires in any loading condition. In torsion, olive wires with 10 degrees and 20 degrees tilt were not significantly different, while in posterior bending olive wires with 10 degrees tilt were significantly stiffer than olive wires with 0 degree or 20 degrees tilt. With smooth wires, tilting the wire plane caused a decrease in stiffness in posterior bending, posteromedial bending, and torsion. Overall, the use of olive wires in conjunction with tilting the wire plane enhances the fixation stiffness for proximal tibia fractures while allowing more options for wire configurations that avoid neurovascular and musculotendinous structures, and wounds.

External Fixators↗

PubMed2005

The effect of transfixion wire number and spacing between two levels of fixation on the stiffness of proximal tibial external fixation.

OBJECTIVES: Anatomic constraints about the proximal tibia limit the ability to insert wires at the biomechanically optimum angle of 90 degrees, thus diminishing the potential stability of external fixators used for proximal tibial fractures. To overcome this problem, surgeons use more than 2 wires at a single level of fixation or a second level of fixation. This study evaluated the effect of transfixion wire number and placement of a second level of fixation on the stiffness of proximal tibial external fixation. METHODS: A fiberglass tibia fixed into an idealized ring external frame was tested. Load-deformation behavior was compared among the different wire numbers (1 level with 2, 3, 4, and 5 wires) and placement of a second level of fixation (2 wires first level and 1 wire second level, and 2 wires first level and 2 wires second level) at 2, 3, 4, 5, 6, 7, 8, 9, and 10 cm distance from the first level of fixation. Identical loading conditions of central axial compression, medial compression-bending, posterior compression-bending, posteromedial compression-bending, and torsion were used. Stiffness values were calculated from the load-displacement and the torque-angle curves. RESULTS: An increase in wire number at 1 level led to an overall increase in stiffness, whereas the addition of a second level of fixation and increased spread between these 2 levels increased bending stiffness. CONCLUSIONS: The addition of a second level of external fixation of the proximal tibia fragment with maximum possible distance between the 2 levels increases bending stiffness, whereas increasing the number of transfixion wires increases overall stiffness. Axial and torsional stiffness is proportional to the total number of wires regardless of the number of levels of fixation.

Biomechanical Phenomena↗

PubMed2004

The accuracy of fine wire tensioners: a comparison of five tensioners used in hybrid and ring external fixation.

OBJECTIVES: To compare the accuracy of 5 commonly available fine wire tensioners used in hybrid and ring external fixation. DESIGN: A laboratory investigation. SETTING: The testing of 5 commonly available tensioners was performed with a servohydraulic test frame (MTS Bionix 858, Minneapolis, MN). MAIN OUTCOME MEASUREMENT: The real wire tension data of each tensioner provided by the MTS were compared with corresponding nominal values. The percent error for each tensioner was calculated. Clinical ease of usage of the wire tensioners was also evaluated. RESULTS: The EBI tensioner was the most accurate (-0.17% to 0.09% error). The Smith and Nephew tensioner had a -13.97% to -8.61% error, the How medica tensioner a -12.48% to -10.86% error, and the Synthes tensioner a -0.2% to 24.28% error. The DePuyACE tensioner was the least accurate, with errors ranging from -36.76% to -30.92%. The Howmedica tensioner was the easiest to use, followed by the Smith and Nephew tensioner, the DePuyACE tensioner, the Synthes tensioner, and the EBI tensioner. CONCLUSIONS: Most commonly available tensioners tend to undertension. Future efforts should focus on the development of wire tensioners that combine accuracy and ease of usage.

Bone Wires↗

PubMedDate not supplied

Biomechanics of external fixation of distal tibial extra-articular fractures: is spanning the ankle with a foot plate desirable?

OBJECTIVES: To compare the mechanical stability of external fixation with and without spanning of the ankle joint with a foot plate in an in vitro model of extra-articular distal tibia fractures. DESIGN: A laboratory investigation was performed to evaluate the mechanical behavior of external fixation of extra-articular distal tibia fractures using a fixator with and without a foot plate. Ten fresh-frozen lower extremities (5 pairs) with a simulated OTA 43-A3.3 fracture were stabilized with an Ilizarov hybrid fixator with and without a foot plate. SETTING: All mechanical testing was performed with a servohydraulic test frame (MTS Bionix 858, Minneapolis, MN). MAIN OUTCOME MEASUREMENT: Deformation characteristics as a function of load were compared for an Ilizarov fixator with and without a foot plate under identical conditions of forefoot loading from 0 to 100 N. Relative interfragmentary motions (vertical and horizontal translations and rotation) were measured. RESULTS: There was significantly more vertical translation (2.57 +/- 0.97 mm vs. -0.83 +/- 0.64 mm) and angular displacement (4.49 +/- 0.45 degrees vs. -1.15 +/- 0.61 degrees ) of the distal fragment in the arrangement without a foot plate compared with the construct with a foot plate. The anterior translation of the distal fragment was similar with (1.12 +/- 0.98 mm) and without a foot plate (1.19 +/- 1.23 mm). CONCLUSIONS: This study supports the mechanical importance of spanning of the ankle with a foot plate in most cases of external fixation for unstable extra-articular and periarticular distal tibia fractures. Further studies are needed to validate these results before widespread changes in clinical treatment can be recommended.

Aged↗

PubMedDate not supplied

Biomechanics of olive wire positioning and tensioning characteristics.

The effect of the olive wire on the stiffness of external fixation has been studied previously, but there are limited data on the effect of the olive wire positioning and tensioning characteristics on the stiffness of external fixation. This study evaluated the influence of olive wire positioning (medially, laterally, posteriorly, and anteriorly) and tensioning characteristics (tensioning one end or both ends) on the stiffness of ring external fixation. A fiberglass composite tibia fixed into an idealized ring external frame was tested. All mechanical testing was performed with a servohydraulic test frame (MTS Bionix 858, Minneapolis, MN). Load-deformation behavior was compared among different wire design and olive wire positioning and tensioning characteristics under central axial compression, medial compression-bending, posterior compression-bending, posteromedial compression-bending, and torsion. The differences between tension values on opposite ends of the wire during different modalities of olive wire tensioning were also investigated. Olive wires tensioned on both ends provided significantly greater bending stiffness compared with smooth wires and olive wires tensioned only on the end opposite to the olive (P < 0.05). There was a significant difference between the tension values on opposite ends of the olive wire during tensioning (P < 0.05). Tensioning both ends of the olive wires and positioning the olives on the side of bending significantly increase the bending stiffness of ring external fixation. This work provides a rationale for clinical decision-making about the use of tensioned olive wires opposed to smooth wires in ring external fixation.

Biomechanical Phenomena↗

PubMedDate not supplied

Transfixion wire positioning within the bone: an option to control proximal tibia external fixation stiffness.

PURPOSE: The greatest angle that can be formed by the crossing wires at the proximal tibia level without altering safe corridors approaches only 60 degrees. Consequently, the wires are positioned more in the coronal than the sagittal plane. Looking for an increase in sagittal bending stiffness, we evaluated different wire positioning within the proximal tibia and their effect on the stiffness of external fixation of proximal tibia. STUDY DESIGN: A fiberglass composite tibia fixed into an idealized ring external frame was tested with a servohydraulic test frame. Load-deformation behavior was compared among the different wire positioning within the proximal tibia under identical conditions of central axial compression, medial compression-bending, posterior compression-bending, posteromedial compression-bending, and torsion. Stiffness values were calculated from the load-deformation and the torque-angle curves. RESULTS: The sample with 3 wires positioned within the bone-2 wires crossed 1 cm posteriorly from the center of the tibia and the third wire placed in coronal plane 1 cm anteriorly from the center of the tibia-was significantly (P < 0.05) stiffer in posterior, posteromedial, and torsional loading configurations compared with all other wire positions within the bone. CONCLUSIONS: This new wire positioning within the proximal tibia-2 wires crossed 1 cm posteriorly from the center of the tibia and the third wire placed in coronal plane 1 cm anteriorly from the center of the tibia-increased overall stiffness of external fixation, predominantly in sagittal plane. CLINICAL RELEVANCE: This work provides a rationale to control proximal tibia external fixation stiffness in sagittal plane.

Bone Wires↗

PubMedDate not supplied

Bone lengthening in children: how to predict the complications rate and complexity?

PURPOSE: Complications arising from limb-lengthening procedures are often severe leading to long-term residuals. The aim of this study was to determine whether the complication rate and complexity could be predicted using a distraction index for bone lengthening in children. STUDY DESIGN: This study retrospectively reviewed a series of 116 lower limbs lengthening in 88 consecutive patients (mean age 13.5). Mean follow-up 3.8 years. Lengthening percentage, lengthening index, distraction regenerate length, additional surgeries, and complications rate were used to evaluate the results of limb lengthening. The correlation between lengthening percentage and complication rate was particularly analyzed and its practicability illustrated. Scatter plots of complication rate (%) against lengthening percentage were constructed, and linear regression was used to investigate mathematical relationship between the variables. RESULTS: The lengthening index was 33 +/- 12.1 days/cm. The length of distraction regenerate was 6 +/- 3.2 cm. The lengthening percentage was 21 +/- 16.5. The scatter plots of neurological complication rate, residual deformities rate, broken pins rate, joint contractures rate, and hypertension rate against lengthening percentage showed a positive linear relationship with r = 0.8. CONCLUSIONS: The number of complications increased considerably with the increase in lengthening percentage. The lengthening percentage correlates very well with the complication rate and can be used to predict the complication rate. CLINICAL RELEVANCE: During planning a lengthening procedure, the lengthening percentage should be a useful tool to predict the complications rate and to discuss the risks and benefits with patients and their families. The knowledge about predictable complications should help prevent and early detect expected complications.

Adolescent↗