Ex vivo mechanical properties of a 2.5-mm bone anchor for treatment of cranial cruciate ligament rupture in toy breed dogs.

Objective: To determine the mechanical pull-out properties of a 2.5-mm bone anchor implanted in ex vivo femurs of toy breed dogs and to determine whether there is a difference between knotted and knotless configurations.

Study Design: Experimental study.

Sample Population: Eight paired harvested femurs.

Methods: Femurs were assigned to knotted or knotless configuration. Equal numbers of right and left femurs were tested. The caudolateral femoral condyle at the distal pole of the lateral fabella (F2 site) was drilled. The assigned configuration with braided suture combined with the bone anchor was implanted into the F2 site. Each configuration was positioned into a mechanical testing machine to measure yield load, load at 3-mm displacement, ultimate load, stiffness, and mode of failure at the beginning of the canine standing phase angle (150°).

Results: Mean ultimate load was 100.14 and 88.69 N (P = .798), mean yield load was 59.72 and 55.85 N (P = .708), load at 3-mm displacement was 46.72 and 43.33 N (P = .656), and stiffness was calculated to be 43.06 and 47.09 N/mm (P = .548) for knotted and knotless configurations, respectively. Mode of failure occurred primarily by anchor pull-out.

Conclusion: The bone anchor withstood deformation at the estimated forces applied on the native cranial cruciate ligament (CCL) of toy breed dogs in both configurations.

Clinical Significance: This bone anchor may constitute a useful alternative for stabilization of the CCL deficient stifle in toy breed dogs. However, before it can be recommended for widespread use in dogs, closely monitored clinical trials must be conducted to assess outcome and complications associated with this implant.