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Purpose: To evaluate the effects of different stitching methods and suture diameters on the graft fixation of soft tissue human quadriceps tendon grafts for anterior cruciate ligament (ACL) reconstruction., Methods: The Krackow locking stitch (K), whipstitch (W), and baseball stitch (B) were combined with either a 2× no. 2 (#2) or a 1× no. 5 (#5) braided composite suture for graft fixation of 36 human quadriceps tendons in 6 groups. Biomechanical testing was performed using a cyclic protocol with loads between 0 and 100 N. The maximum load until failure, cyclic elongation, and failure mode were recorded., Results: The highest mean maximum load to failure was observed in the 2 Krackow stitch groups. The K#2 group had significantly higher load to failure values compared with those of the W#2 and B#2 groups (K#2, 553 ± 82 N vs W#2, 392 ± 107 N, P = .0349; K#2 vs B#2 366 ± 118 N, P = .0129). The mean cyclic elongation was lowest in the Krackow groups (K#2, 10.59 ± 2.63 mm; K#5, 13.66 ± 2.3 mm). The regular failure mode was the rupture of the suture for the Krackow stitch (8 of 12) and suture pullout for the whipstitch (11 of 12) and baseball stitch groups (12 of 12)., Conclusions: The double Krackow stitch with no. 2 braided composite suture exhibits a high maximum load to failure combined with a low amount of elongation in a biomechanical study for human quadriceps tendon soft tissue graft fixation. Unlike the whipstitch and the baseball stitch, it can solidly prevent suture pullout., Clinical Relevance: A safe soft tissue graft fixation technique is especially important for quadriceps tendon grafts with their laminar anatomical structure and physiologically varying diameter. Unlike other grafts for ACL replacement, it fully relies on the soft tissue suture fixation to resist the pullout force., (Copyright © 2019 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: The structural properties of hamstring tendon grafts were evaluated in a porcine model, after processing it to a flat shape, to better replace or augment anatomic flat structures (e.g. ACL, MPFL or MCL)., Methods: In this biomechanical study, porcine flexor tendons were used which have a comparable shape to semitendinosus and gracilis tendons. One part of the tendon was prepared to a flat tendon construct by splitting the tendon longitudinally with a knife to half of the diameter of the tendon. The semi-split tendon was scratched out to a flat shape. The other matched part was tested in its original round shape. The tendons (n = 40) have been fixed in a uniaxial testing machine (Zwick/Roell) by cryo-clamps after preparing the fixed ends by 2-0 polyester sutures (2-0 Ethibond ® EXCEL, Ethicon, Somerville, NJ). In every specimen, there was a free 60-mm tendon part between both clamps. The tendons have been loaded to failure to evaluate typical biomechanical parameters such as stiffness, yield load and maximum load., Results: No statistically significant differences (n.s.) regarding stiffness, yield load and maximum load between natively round and processed flat tendons could be detected., Conclusion: A prepared flat-shaped tendon does not show any different structural properties compared with an original round tendon. Therefore, a flat tendon seems to be a biomechanical stable graft option for anatomic reconstruction or augmentation of injured natively flat-shaped structures such as MCL, MPFL or ACL.

Introduction: Porcine flexor tendons, bovine extensor tendons, and human (semitendinosus) tendons are frequently used as substitutes for human ACL grafts in biomechanical in vitro studies. This study compares the biomechanical properties and structural differences of these tendons., Materials and Methods: In this biomechanical study, fresh-frozen porcine flexor tendons, bovine extensor tendons, and human semitendinosus tendons were used (n = 36). The tendons were mounted in a uniaxial testing machine (Zwick/Roell) with cryo-clamps, leaving a 60 mm tendon part free between the two clamps. Specimens have been loaded to failure to evaluate the biomechanical parameters stiffness, yield load, and maximum load. A Total Collagen Assay Kit was used to detect differences in the total collagen type I concentration (n = 30). A one-way ANOVA was performed to detect differences in the means. The significance level was set at p < 0.05., Results: There were no significant differences in the stiffness between the groups (bovine 194 ± 43 N/mm, porcine 211 ± 63 N/mm, and human cadaveric 208 ± 58 N/mm). The yield and maximum loads were high (>1000 N) in all groups, but they were significantly increased in both animal specimens (means of 1681-1795 N) compared with human cadaveric specimen (means of 1289-1406 N; p < 0.01). No difference in the collagen type I concentration was detected (N.S.)., Conclusion: Porcine flexor and bovine extensor tendons are eligible substitutes with similar stiffness and high failure loads compared with human cadaveric semitendinosus tendons in in vitro studies.

Background: The aim of this study was to analyze the structural properties of the original MPFL and to compare it to a MPFL-reconstruction-technique using a strip of quadriceps tendon., Methods: In 13 human cadaver knees the MPFLs were dissected protecting their insertion at the patellar border. The MPFL was loaded to failure after preconditioning with 10 cycles in a uniaxial testing machine evaluating stiffness, yield load and maximum load to failure. In the second part Quadriceps-MPFL-reconstruction was performed and tested in a uniaxial testing machine. Following preconditioning, the constructs were cyclically loaded 1000 times between 5 and 50 N measuring the maximum elongation. After cyclic testing, the constructs have been loaded to failure measuring stiffness, yield load and maximum load. For statistical analysis a repeated measures (RM) one-way ANOVA for multiple comparisons was used. The significance was set at P<0.05., Results: During the load to failure tests of the original MPFL the following results were measured: stiffness 29.4 N/mm (+9.8), yield load 167.8 N (+80) and maximum load to failure 190.7 N (+82.8). The results in the QT-technique group were as follows: maximum elongation after 1000 cycles 2.1 mm (+0.8), stiffness 33.6 N/mm (+6.8), yield load 147.1 N (+65.1) and maximum load to failure 205 N (+77.8). There were no significant differences in all tested parameters., Conclusions: In a human cadaveric model using a strip of quadriceps-tendon 10 mm wide and 3mm deep, the biomechanical properties match those of the original MPFL when tested as a reconstruction., Clinical Relevance: The tested QT-technique shows sufficient primary stability with comparable biomechanical parameters to the intact MPFL., (Copyright © 2014. Published by Elsevier B.V.)