Arthroscopy: The Journal of Arthroscopic & Related Surgery
Original articleCyclic Loading Comparison Between Biodegradable Interference Screw Fixation and Biodegradable Double Cross-Pin Fixation of Human Bone-Patellar Tendon-Bone Grafts
Section snippets
Biomechanical Model
In this study, 60 fresh bovine knees were used to simulate young human femoral density as described by Weiler’s group.10, 16 In their model, the screw insertion site is located in the center of the bovine tibia. This location represents a trabecular bone density of 0.8 g/cm3, similar to what is expected in young human femora.7, 14, 24
The mean age of the animals was 28 ± 2 weeks. The material was obtained from a local butcher, fresh frozen at −20°C and thawed for 12 hours at room temperature
Results
None of the 8-mm BPTB grafts that were fixed using the cross-pin technique survived the 1,000 cycles of load. All grafts failed rapidly after a mean number of 124 ± 34 cycles. In all specimens, the failure mode was fracture of the bone block at the pin, which was inserted at the “articular” side of the bone block.
In the 9-mm and 10-mm cross-pin groups and in all interference screw groups, the fixations did not fail before 1,000 cycles. The displacement data of the cyclic loading test are listed
Discussion
The aim of the present study was to evaluate whether bone block size has an impact on the stability of the cross-pin technique for BPTB graft fixation. The results of this study clearly show that the bone block diameter is an important factor for the primary stability of a BPTB graft fixation using the cross-pin technique. None of the 8-mm grafts fixed with the cross-pin method survived 1,000 cycles of load between 50 and 250 N and all specimens failed by bone-block fracture. The bone-block
Conclusions
Femoral fixation of a 10-mm and a 9-mm BPTB graft using 2.7-mm RigidFix biodegradable pins leads to primary stability that is comparable to fixation with biodegradable interference screws. Since cross-pin fixation of large bone blocks had a significantly lower displacement than interference screw fixation, we prefer this method over interference screw fixation. However, we do not recommend the use of the RigidFix cross-pin technique for bone blocks smaller than 9 mm. Future studies have to
Acknowledgment
The authors thank M. Vogiatzis, S. Zander, and A. Studt for their expert technical assistance. The implants used in this study were kindly provided by Ethicon, Mitek Division, Norderstedt, Germany.
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2013, KneeCitation Excerpt :A fast and stable integration of the graft in the bone tunnel is a prerequisite for accelerated rehabilitation [6]. Currently-available graft fixation devices demonstrate large variation in mechanical properties [7–14]. Tsuda et al. found in their biomechanical study that EndoButton fixation of a soft-tissue graft resulted in significantly larger graft-tunnel motion, and consequently, greater anterior knee laxity compared with an interference screw closer to the intra-articular entrance of the bone tunnel [12].