Comparison between a novel human cortical bone screw and bioabsorbable interference screw for graft fixation of ACL reconstruction

X.-Z. Shen, F. Qu, C.-B. Li, W. Qi, X. Lu, H.-L. Li, Q. Guo, J.-T. Wang, G. Zhao, Y.-J. Liu

Department of Orthopedics, Chinese PLA General Hospital, Beijing, China. liuyujie301@163.com

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• Orthopedics

OBJECTIVE: To compare the mechanical behavior of a novel bioabsorbable cortical interference screw (BCIS) with bioabsorbable interference screw (BIS; Polylactate hydroxyapatite) used for anterior cruciate ligament (ACL) reconstruction in femoral and tibial fixation with doubled Achilles tendon graft in vitro.

PATIENTS AND METHODS: 30 paired goat knee specimens were harvested from 15 male sheep aged 18 months. All soft tissues were stripped from the bones of 20 paired specimens, and the last 10 paired specimens were stripped all soft tissues besides ACL (femur-ACL-tibia complex). The Achilles tendon was harvested as graft for ACL reconstruction. The specimens were divided into several groups: BCIS femoral fixation (group A, n=10), BIS femoral fixation (group B, n=10), BCIS tibial fixation (group C, n=10), BIS tibial fixation (group D, n=10), Group E is femur-ACL-tibia complex (n=10). Cyclic loading test was performed from 50 to 250 N at 1 Hz for 1000 cycles and followed by a load-to-failure test at 25 mm/sec. A paired t-test was used to compare the biomechanical properties of group A, B, E and group C, D, E.

RESULTS: No fixation structures failed during the cyclic phase. Cyclic displacement for group B was superior to group A, and showed statistically significant difference after 30, 100, 500, 1000 cycles. Group E got minimum cyclic displacements compared with group A and group B, and showed statistically significant difference after 500, 1000 cycles compared with group A. Cyclic displacement for group D was superior to group C, and showed statistically significant difference after 100, 500, 1000 cycles. Group E got minimum cyclic displacements compared with group C and group D, and showed statistically significant difference after 500,1000 cycles compared with group C. Regarding MFL, group A was superior to group B (572.10±111.12 N vs. 413.96±34.56 N, p=0.118), group E was superior to group A (599.74±85.45N vs. 572.10±111.12 N, p=0.992), and group C was superior to group D (802.88±240.07 N vs. 415.63±51.9 N, p<0.001), group C was superior to group E (802.88±240.07 N vs. 599.74±85.45 N, p=0.024). Regarding YL, group A was superior to group B (521.57±93.96 N vs. 366.99±44.66 N, p=0.109), group E was superior to group A (565.37±66.05 N vs. 521.57±93.96 N, p=0.952), and group C was superior to group D (735.63±242.91 N vs. 394.49±31.90 N, p<0.001), group C was superior to group E (735.63±242.91 N vs. 565.37±66.05 N, p=0.063). Regarding stiffness, group A was superior to group B (157.36±34.31 N/mm vs. 91.98±25.57 N/mm, p=0.001), group E was superior to group A (181.35±25.42 N vs. 157.36±34.31 N/mm, p=0.529), and group C was superior to group D (175.28±43.19 N/mm vs. 128.24±18.92 N/mm, p=0.032), group E was superior to group C (181.35±25.42 N/mm vs. 175.28±43.19 N/mm, p=0.995).

CONCLUSIONS: In vitro, this experimental study suggested the biomechanical properties of novel bioabsorbable cortical interference screw (BCIS) were superior to bioabsorbable interference screw (BIS) used for femoral and tibial anterior cruciate ligament (ACL) reconstruction in a goat knee model.

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