What did the study look at?
In anterior cruciate ligament reconstruction (ACL reconstruction), the tendon graft that replaces the torn ligament has to stay in place and under tension until it heals into the bone. A common way to achieve this is a small metal button that sits on the outer surface of the thigh bone, attached to a suture loop (cortical suspensory fixation). The loop is either of fixed length or adjustable during surgery.
According to the authors, it is unclear how much adjustable-loop devices lengthen under load and how they fail. The study compared four adjustable-loop devices with different locking mechanisms against an industry-standard fixed-loop device.
How was it done?
This was a laboratory biomechanical study, not a study in patients, using pig thigh bones and doubled cow tendons that mimic a human hamstring graft.
- Five devices were tested: EndoButton (fixed loop), Infinity Button (button-locking), ProCinch and UltraButton (suture-locking) and TightRope (dual-locking).
- Eleven specimens were prepared per device, 55 constructs in total.
- To simulate early rehabilitation, each construct was loaded for 500 cycles between 10 and 250 N; to simulate late rehabilitation, a further 500 cycles between 10 and 400 N followed.
- The constructs were then pulled to failure at 50 mm per minute.
The main measurements were lengthening of the construct during cycling (excursion), maximum load, stiffness, energy absorbed up to maximum load, and the mode of failure.
What did it find?
- All specimens survived cyclic loading without failure.
- There was no difference in excursion between devices during the early rehabilitation protocol or across all 1,000 cycles.
- During the late rehabilitation protocol (10-400 N), the button-locking device (3.34 ± 1.71 mm) and the dual-locking device (3.63 ± 1.18 mm) lengthened more than the fixed-loop device (1.49 ± 0.36 mm).
- The two suture-locking devices (1270.5 ± 204.7 N and 1232.7 ± 185.2 N) withstood higher loads than the button-locking (1011.4 ± 95.8 N) and dual-locking (1018.4 ± 63.1 N) devices. There was no significant difference in maximum load between the fixed-loop device and the adjustable devices.
- The button-locking and dual-locking devices mostly failed by rupture of the suture loop, whereas the fixed-loop and suture-locking devices mostly failed at the button. No construct failed through release of the locking mechanism.
- Constructs that failed by suture rupture showed more late excursion, a lower maximum load and less energy absorption than those that failed at the button.
The authors' conclusion
The authors concluded that all constructs withstood forces above those expected during early and total rehabilitation after ACL reconstruction, confirming adequate initial strength for both fixed-loop and adjustable-loop devices. Differences in excursion and failure load were linked to the design of the locking mechanism and the resulting mode of failure. They stress that it is uncertain whether these differences translate into clinically meaningful outcomes for patients.
Limitations
- The devices tested may not represent the latest commercially available models; for example, the current version of the dual-locking device uses a different suture material.
- Although pig knees and cow tendons resemble human tissue, their material differences cannot be ignored.
- Variation in the bone density of the pig specimens may have influenced the failure modes.
- The study reflects the moment of surgery only (time zero) and does not account for healing after the operation. The authors state that clinical studies are needed to support these comparisons.
Reference
Vega TF, Espinosa JBV, Shewman E, Khan ZA, Singh H, Williams BT, Alter T, Gilat R, Gürsoy S, Bi AS, Chahla J. (2026). Full-Construct Biomechanical Evaluation of Femoral Cortical Suspensory Fixation for Anterior Cruciate Ligament Reconstruction in a Porcine Knee Model. Orthopaedic Journal of Sports Medicine, 14(9): 23259671261445909. Licence: CC BY-NC-ND 4.0.
DOI: 10.1177/23259671261445909
Free full text: PubMed Central (PMC13539019)
This article summarises a published scientific paper for general information; it does not replace an examination or a personal medical assessment. Please consult your doctor about your symptoms.
