Employing Indirect Adenosine 2A Receptors (A2AR) to Enhance Osseointegration of Titanium Devices: A Pre-Clinical Study.

The present study aimed to evaluate the effect of dipyridamole, an indirect adenosine 2A receptors (A2AR), on the osseointegration of titanium implants in a large, translational pre-clinical model. Sixty tapered, acid-etched titanium implants, treated with four different coatings ((i) Type I Bovine Collagen (control), (ii) 10 µM dipyridamole (DIPY), (iii) 100 µM DIPY, and (iv) 1000 µM DIPY), were inserted in the vertebral bodies of 15 female sheep (weight ~65 kg). Qualitative and quantitative analysis were performed after 3, 6, and 12 weeks in vivo to assess histological features, and percentages of bone-to-implant contact (%BIC) and bone area fraction occupancy (%BAFO). Data was analyzed using a general linear mixed model analysis with time in vivo and coating as fixed factors. Histomorphometric analysis after 3 weeks in vivo revealed higher BIC for DIPY coated implant groups (10 µM (30.42% ± 10.62), 100 µM (36.41% ± 10.62), and 1000 µM (32.46% ± 10.62)) in comparison to the control group (17.99% ± 5.82). Further, significantly higher BAFO was observed for implants augmented with 1000 µM of DIPY (43.84% ± 9.97) compared to the control group (31.89% ± 5.46). At 6 and 12 weeks, no significant differences were observed among groups. Histological analysis evidenced similar osseointegration features and an intramembranous-type healing pattern for all groups. Qualitative observation corroborated the increased presence of woven bone formation in intimate contact with the surface of the implant and within the threads at 3 weeks with increased concentrations of DIPY. Coating the implant surface with dipyridamole yielded a favorable effect with regard to BIC and BAFO at 3 weeks in vivo. These findings suggest a positive effect of DIPY on the early stages of osseointegration.

Fixation of the Anterior Ligament Graft at the Tibial Pole: Biomechanical Analysis of Three Methods.

Objective Comparative biomechanical analysis of tibial fixation strength for ligament reconstruction with interference screw compared with screw post and washer, and compared with the associated fixation of both methods (hybrid fixation). Method A total of 54 specimens were used (porcine tibias and bovine flexor digital tendons), which were divided into three groups with fixation types similar to those used in anterior cruciate ligament (ACL) reconstruction: 1) fixation with interference screw; 2) fixation with screw post and toothed washer over knot and suture strand; and )- fixation with screw post and washer combined with interference screw (hybrid fixation). The analyses were performed through pull-out biomechanical tensile tests to determine the stiffness and load to system failure (yield load). Results The hybrid fixation group presented a significantly higher final stiffness (59.10 ± 3.45 N/mm) in comparison to the other groups ( p < 0.05) and a higher yield load (581.34 ± 33.48 N) compared to the interference screw group ( p < 0.05). Conclusion Hybrid fixation had biomechanical advantages over the bovine digital flexor graft fixation system in swine tibia during tensile tests.

Fixation of the Anterior Ligament Graft at the Tibial Pole: Biomechanical Analysis of Three Methods / Fixação do enxerto do ligamento cruzado anterior no polo tibial: Análise biomecânica de três métodos

Abstract Objective Comparative biomechanical analysis of tibial fixation strength for ligament reconstruction with interference screw compared with screw post and washer, and compared with the associated fixation of both methods (hybrid fixation). Method A total of 54 specimens were used (porcine tibias and bovine flexor digital tendons), which were divided into three groups with fixation types similar to those used in anterior cruciate ligament (ACL) reconstruction: 1) fixation with interference screw; 2) fixation with screw post and toothed washer over knot and suture strand; and )- fixation with screw post and washer combined with interference screw (hybrid fixation). The analyses were performed through pull-out biomechanical tensile tests to determine the stiffness and load to system failure (yield load). Results The hybrid fixation group presented a significantly higher final stiffness (59.10 ± 3.45 N/mm) in comparison to the other groups (p < 0.05) and a higher yield load (581.34 ± 33.48 N) compared to the interference screw group (p < 0.05). Conclusion Hybrid fixation had biomechanical advantages over the bovine digital flexor graft fixation system in swine tibia during tensile tests.

Resumo Objetivo Análise biomecânica comparativa da resistência da fixação tibial para reconstrução ligamentar com parafuso de interferência, comparada com parafuso do tipo poste com arruela, e com fixação associada entre os métodos (fixação híbrida). Métodos Foram utilizados 54 corpos de prova (tíbia suína e tendão digital bovino), que foram divididos em 3 grupos com tipos de fixação semelhantes àqueles utilizados na reconstrução do ligamento cruzado anterior: 1) fixação com parafuso de interferência; 2) fixação com parafuso do tipo poste com arruela dentada sobre nó e fios de sutura; e 3) fixação com parafuso do tipo poste com arruela combinada com parafuso de interferência (fixação híbrida). Os testes foram realizados por meio de ensaios biomecânicos de tração tipo pull-out para determinação da rigidez e carga para falha (yield load) do sistema. Resultados O grupo com fixação híbrida apresentou maior rigidez final (59,10 ± 3,45 N/mm) do que os demais grupos (p < 0,05), e carga superior para falha (581,34 ± 33,48 N) em relação ao grupo com parafuso de interferência (p < 0,05). Conclusão A fixação híbrida apresentou vantagens biomecânicas com relação ao sistema de fixação do enxerto de flexor digital bovino em tíbia suína durante os ensaios de tração.