Self-locking button-like fixation devices for ACL reconstruction are attracting knee surgeons' attention due to promising technical advantages: complete filling of the tunnel with graft, anatomic reconstruction (AM portal), fixation achievement even when a short tunnel is reamed, opportunity of graft re-tensioning after tibial fixation and/or cyclic load. We compared two similar devices (TightRope vs ToggleLocZL)

20 fresh-frozen porcine femurs (mean age 2.1 years) were assigned to the two groups by randomization. Hamstrings with 9 mm of diameter were obtained using bovine tendons that show the same biomechanic behaviour of human hamstrings. Femoral tunnel was created by AM portal technique (anatomic position). Zwick-Roell z010 tension/compression device with bone and tendon clamps, was used for the study:

Cyclic test (1000 cycles, 0.5 Hz, 50–250 N/cycle, 50 cycles of preload at 10–80 N/cycle)

Final pull-out test (1 mm/s)

Failure analysis

CT scan and densitometry

Any implant didn't fail during cyclic test. The elongation average was 2.85±1.63 for ToggleLoc and 2.71±.85 for TightRope (P>0.05). Pull-out test showed different values in terms of Ultimate Strength Failure (USF), Stiffness at USF, and Stiffness:

The failure mode was:

The mean method of failure was the fracture of the cortical bone of the femoral condyle, for both groups. But if we extrapolate the USF the difference was favourable(P<0.05) for TightRope (707.83 N) than ToggleLoc (580.16).

The mean bone density of porcine femora was comparable to young human femora (1.12±0.31 BMD)

The reproducibility of surgical technique, the mechanical strength and endurance of the systems suggest two valid options for ACL reconstruction with hamstring. ToggleLoc showed worse results due to the sharp squared edges of the button.

Transverse pin femoral fixation of bone-patella tendon-bone (BPTB) in ACL reconstruction has been widely applied during the last decades. Aim of our study is to confront two different system of transverse femoral fixation for BPTB graft: Transfix BTB (Arthrex) and BioTransfix T3 (Arthrex). The main differences between these two system are the diameter (3.0 mm Transfix BTB and 3.5 mm BioTransfix T3), and section (Transfix BTB is cannulated). Surgical technique adopts the same transverse vectorial guide but different guide sleeves.

30 fresh-frozen porcine knees (mean age 2.2 years) were assigned to the two groups randomisedly. the patellar bone block and tendon were harvested using the same size in all specimens (10mm × 25 mm, 10 mm). Zwick-Roell z010 tension/compression device with bone clamps, was used for the study:

Cyclic test (1000 cycles, 0.5 Hz, 50–250 N/cycle, 100 cycles of preload)

Final pull-out test (1 mm/s)

Failure analysis

CT scan and densitometry

Any implant didn't fail during cyclic test. The elongation average was 1.85±0.63 for Transfix BTB and 1.69±0.87 for BioTransfix T3. Pull-out test showed very similar values in terms of Ultimate Strength Failure (USF), Stiffness at USF, and Stiffness:

The failure mode was bone plug fracture (12 for Transfix BTB and 13 for BioTransfix T3) and tendon failure (3 for Transfix BTB and 2 for BioTransfix T3).

The post-test CT scan showed any failure of the fixation devices and the correct position inside the femoral half-tunnel.

The mean bone density of porcine femora was comparable to young human femora (1.12±0.31 BMD)

Both systems showed a similar behaviour in terms of USF, Stiffness, Cyclic load, method of failure and other biomechanical parameters. The reproducibility of surgical technique, the mechanical strength and endurance of the systems suggest two valid options for ACL reconstruction with BPTB even if in-vivo studies are necessary to confirm the animal ex-vivo biomechanical data.

The purpose of this study is to biomechanically evaluate how four different fixation devices (two femoral and two tibial) associated in three different combinations, using cyclic loading with final pull-out test, affect the strength and the stiffness of the femur-graft-tibia complex.

We conducted a controlled laboratory study and tested, using cyclic loading with final pull-out, two femoral devices (Swing- bridge and Endobutton CL) and two tibial device (Evolgate and BioRCI screw) in three different combinations: Group A, EB-Bio RCI; Group B, EB-Evolgate; and Group C, SB- Evolgate.

We used porcine knees and bovine digital extensor tendons and evaluated the stiffness and strength at the final pull-out, and the displacement at the 1st, 100th, 300th, 500th and 1000th cycle.

A t-test was used for statistical evaluation.

There was a statistically significant difference in ultimate failure load between group A and group B (p=0.03) and group A and group C (p=0.0007) but no difference between group B and group C (p=0.72). There was a statistically significant difference in ultimate failure load between group A and group C (p=0.02) and group B and group C (p=0.01) but no difference between group A and group B (p=0.88).

Due to the biomechanical properties of the F-G-T complex the combination of Swing-Bridge and Evolgate seems to be a good alternative when an accelerated post-operative rehabilitation is planned after ACL reconstruction using DGST.

The purpose of this study is to biomechanically compare Evolgate and Intrafix using cyclic loading with final pull-out tests. Five pairs of double looped bovine digital extensor tendons and 10 porcine tibias were used. We evaluated the displacement at 1, 10, 100, 250, 500, 1000 and 1500 cycles. We used cyclic tests (1500 cycles between 50 and 200 N with final pull-out). Biomechanical tests were performed with use of a Zwick-Roell Z010 mechanical testing machine (Zwick-Roell, Germany), and the testing data were recorded with the accompanying software package (Testexpert 8.1, Zwick-Roell). A paired t-test was performed for statistical evaluation. There was no statistically significant difference in slippage between the two devices. The mean ultimate failure load at pull-out after 1500 cycles was 832±156 N for Intrafix and 1058±130 N for the Evolgate.The mean stiffness at pull-out was 269±86 for Intrafix and 247±44 for the Evolgate, and there were no statistically significant differences (p> 0.05). At statistical evaluation there was a difference in ultimate failure load between the IF and the EV (p< 0.05). Although further studies are needed to investigate bone growth into the tibia tunnel, Evolgate seems to be a good choice for tibial fixation of hamstring tendons. Moreover, Evolgate has higher values of strength than Intrafix.