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Fixation strength of biocomposite wedge interference screw in ACL reconstruction: effect of screw length and tunnel/screw ratio. A controlled laboratory study.

Herrera A, Martínez F, Iglesias D, Cegoñino J, Ibarz E, Gracia L - BMC Musculoskelet Disord (2010)

Bottom Line: The mean loads to failure for each group were 295,44 N (Group 1; 9 x 23 screw), 564,05 N (Group 2; 9 x 28), 614,95 N (Group 3; 9 x 35), 651,14 N (Group 4; 10 x 28) and 664,99 (Group 5; 10 x 35).No slippage of the graft was observed in groups 3, 4 and 5.There were significant differences in the load to failure among groups (ANOVA/P < 0.001).

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Orthopaedic Surgery and Traumatology, Miguel Servet University Hospital, Zaragoza, Aragón Health Science Institute, Spain. aherrera@salud.aragon.es

ABSTRACT

Background: Primary stability of the graft is essential in anterior cruciate ligament surgery. An optimal method of fixation should be easy to insert and provide great resistance against pull-out forces.A controlled laboratory study was designed to test the primary stability of ACL tendinous grafts in the tibial tunnel. The correlation between resistance to traction forces and the cross-section and length of the screw was studied.

Methods: The tibial phase of ACL reconstruction was performed in forty porcine tibias using digital flexor tendons of the same animal. An 8 mm tunnel was drilled in each specimen and two looped tendons placed as graft. Specimens were divided in five groups according to the diameter and length of the screw used for fixation. Wedge interference screws were used. Longitudinal traction was applied to the graft with a Servohydraulic Fatigue System. Load and displacement were controlled and analyzed.

Results: The mean loads to failure for each group were 295,44 N (Group 1; 9 x 23 screw), 564,05 N (Group 2; 9 x 28), 614,95 N (Group 3; 9 x 35), 651,14 N (Group 4; 10 x 28) and 664,99 (Group 5; 10 x 35). No slippage of the graft was observed in groups 3, 4 and 5. There were significant differences in the load to failure among groups (ANOVA/P < 0.001).

Conclusions: Longer and wider interference screws provide better fixation in tibial ACL graft fixation. Short screws (23 mm) do not achieve optimal fixation and should be implanted only with special requirements.

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Related in: MedlinePlus

Geometry of Biosteon® screw. A wedge tip cannulated screw. Distal diameter is smaller providing less contact with the graft and the tunnel. Inverted threads apply traction to the graft as the screw advances through the tunnel.
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Figure 6: Geometry of Biosteon® screw. A wedge tip cannulated screw. Distal diameter is smaller providing less contact with the graft and the tunnel. Inverted threads apply traction to the graft as the screw advances through the tunnel.

Mentions: Biosteon® is a biocomposite made out of Poly L-Lactic Acid and Hydroxyapatite which increases the biocompatibility of the implant and provides osteoconductive potential [35]. This wedge-tip interference screw design (Figure 6) facilitates its insertion even with screws of diameters 1 or 2 mm larger than the tunnel diameter. On the other hand, the wedge tip design makes the diameter of the distal third of the screw smaller than the diameter of rest of the screw. There is less contact between the screw and the bone walls in the proximal portion of the tibial tunnel. During the experimental testing it was obvious that the shortest screws (23 mm length) were the ones that obtained the worst pull-out values (slightly less than 300 N). This difference was significant (p < 0,0001) when comparing group 1 with any of the other groups (Table 2). These values wouldn't guarantee proper fixation during the postoperative usual exercises [36,37].


Fixation strength of biocomposite wedge interference screw in ACL reconstruction: effect of screw length and tunnel/screw ratio. A controlled laboratory study.

Herrera A, Martínez F, Iglesias D, Cegoñino J, Ibarz E, Gracia L - BMC Musculoskelet Disord (2010)

Geometry of Biosteon® screw. A wedge tip cannulated screw. Distal diameter is smaller providing less contact with the graft and the tunnel. Inverted threads apply traction to the graft as the screw advances through the tunnel.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2908564&req=5

Figure 6: Geometry of Biosteon® screw. A wedge tip cannulated screw. Distal diameter is smaller providing less contact with the graft and the tunnel. Inverted threads apply traction to the graft as the screw advances through the tunnel.
Mentions: Biosteon® is a biocomposite made out of Poly L-Lactic Acid and Hydroxyapatite which increases the biocompatibility of the implant and provides osteoconductive potential [35]. This wedge-tip interference screw design (Figure 6) facilitates its insertion even with screws of diameters 1 or 2 mm larger than the tunnel diameter. On the other hand, the wedge tip design makes the diameter of the distal third of the screw smaller than the diameter of rest of the screw. There is less contact between the screw and the bone walls in the proximal portion of the tibial tunnel. During the experimental testing it was obvious that the shortest screws (23 mm length) were the ones that obtained the worst pull-out values (slightly less than 300 N). This difference was significant (p < 0,0001) when comparing group 1 with any of the other groups (Table 2). These values wouldn't guarantee proper fixation during the postoperative usual exercises [36,37].

Bottom Line: The mean loads to failure for each group were 295,44 N (Group 1; 9 x 23 screw), 564,05 N (Group 2; 9 x 28), 614,95 N (Group 3; 9 x 35), 651,14 N (Group 4; 10 x 28) and 664,99 (Group 5; 10 x 35).No slippage of the graft was observed in groups 3, 4 and 5.There were significant differences in the load to failure among groups (ANOVA/P < 0.001).

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Orthopaedic Surgery and Traumatology, Miguel Servet University Hospital, Zaragoza, Aragón Health Science Institute, Spain. aherrera@salud.aragon.es

ABSTRACT

Background: Primary stability of the graft is essential in anterior cruciate ligament surgery. An optimal method of fixation should be easy to insert and provide great resistance against pull-out forces.A controlled laboratory study was designed to test the primary stability of ACL tendinous grafts in the tibial tunnel. The correlation between resistance to traction forces and the cross-section and length of the screw was studied.

Methods: The tibial phase of ACL reconstruction was performed in forty porcine tibias using digital flexor tendons of the same animal. An 8 mm tunnel was drilled in each specimen and two looped tendons placed as graft. Specimens were divided in five groups according to the diameter and length of the screw used for fixation. Wedge interference screws were used. Longitudinal traction was applied to the graft with a Servohydraulic Fatigue System. Load and displacement were controlled and analyzed.

Results: The mean loads to failure for each group were 295,44 N (Group 1; 9 x 23 screw), 564,05 N (Group 2; 9 x 28), 614,95 N (Group 3; 9 x 35), 651,14 N (Group 4; 10 x 28) and 664,99 (Group 5; 10 x 35). No slippage of the graft was observed in groups 3, 4 and 5. There were significant differences in the load to failure among groups (ANOVA/P < 0.001).

Conclusions: Longer and wider interference screws provide better fixation in tibial ACL graft fixation. Short screws (23 mm) do not achieve optimal fixation and should be implanted only with special requirements.

Show MeSH
Related in: MedlinePlus