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Review of current Anterior Cruciate Ligament (ACL) anchor technologies indicates that many devices facilitate osteointegration but not soft tissue in-growth. The design and preliminary testing of a novel biomimetic in-situ dilating bioabsorbable ACL anchor for simultaneous soft and hard tissue attachment is the subject of this study. The anchor method for this concept has been developed to mimic the mechanical-key configuration observed in a hair root. Reviewed anchor devices are typically interference screw-based. Screw anchors can lead to unnecessary ligament pre-stress, tearing during deployment and poor graft-bone contact. This work demonstrates a new fixation concept specifically developed for use with devices consisting of temperature-sensitive glass-reinforced-glass (GRG) soft tissue conductive biomaterial. Ligament anchorage is accomplished by dilation of the device into the base of a hair-root shaped osteotomy where a ligament with a collar and self tightening knot is inserted beforehand. This method facilitates full ligament-to-bone contact at the osteotomy zone where critical physiological ligament anchorage develops. Ligament pull-out loads equivalent to published results for conventional anchors were achieved using graft analogue. Testing with porcine ligaments resulted in a substantial reduction in ligament pull-out loads. Tibia bone sample constraints combined with the unraveling of the ligament knot were identified as primary factors for low pull-out loads for the porcine ligament tests. Subsequent design iterations will employ a reduction in prototype dimensions in addition to the use of a suture to lock the ligament knot. The hair-root shaped osteotomy and ligament anchor knot elements of this approach may be translated to other fixation systems and methods. By improving macro-mechanical-key interaction between the anchor, bone and ligament, further increase in pull-out forces may be achieved without unnecessary ligament pre-stress and tear damage caused by conventional interference screw threads.

Intramedullary (IM) nails are routinely used to stabilize long bone fractures. They can however lead to stress shielding, pain, migration, obstruct hematopoietic tissue, become a loci for infection, and require subsequent surgical retrieval. Novel intra-osseous scaffold (IOS™) prototypes for fracture healing have been developed to function as a regenerative scaffold to enhance callous formation under mechanically stabilized conditions then resorb. Prototype fixation pins and rod systems were formed from glass-reinforced-glass. Flexion, torsion and shear tests were performed to evaluate the composite pins and rods. A modular rod design was successfully deployed and dilated while in a deformable state. When fitted and gripping the intramedullary canal then set in a rigid state. An obliquely sectioned ovine femur was used as a long bone fracture model for deployment and mechanical verification. Flexural support provided by the intramedullary scaffold was superior to multiple k-wire fixation, while the k-wire approach was more stabilizing under torsional loads. Glass reinforced glass samples were mechanically tested after soaking for up to 4 weeks in saline. Strength and modulus of the composite was reduced to approximately 25% of initial values after 2 weeks.