There may be new hope for people suffering from debilitating, slow-healing rotator cuff injuries. Chinese scientists have created an implantable 3D-printed material that both restores shoulder motion and boosts the regrowth of torn tendons.
In a typical rotator cuff injury, one or more of the tendons which connect the shoulder muscles to the head of the humerus (upper arm bone) get partially or fully torn.
If the damage is relatively minor, the injury frequently heals on its own. More severe tears, however, often require surgery to repair. Even then, the recently rejoined tendons may not be able to stand up to the loads placed on them by full use of the shoulder, ultimately resulting in a recurrence of the injury.
Seeking a better-performing alternative to traditional surgical treatments, researchers from The Chinese University of Hong Kong developed the new material.
It's a flexible, stretchable, biocompatible polythiourethane (PHT) elastomer which can be 3D-printed to the exact size and shape required to cover each patient's injury. The printing process is easily conducted at room temperature, using visible light to convert gelatinous PHT resin into solid elastomer form.
Upon being sutured directly over the tear site on the injured tendon, the material proceeds to mimic the mechanical properties of natural tendon tissue, immediately bringing a full range of motion back to the affected shoulder. In lab experiments, it was able to be stretched at least 10,000 times without failing.
Importantly, though, the material also contains two tendon-promoting growth factor proteins. These encourage cells from the adjacent tendon tissue to grow into the material, which has a scaffolding-like microstructure. Over time, as the elastomer gradually and harmlessly degrades, it's replaced by tendon tissue until nothing but that tissue remains.
When tested on rabbits with rotator cuff injuries, the material was able to regrow tendons across a 1-cm (0.4-inch) gap within a period of eight weeks.
"Our work has achieved the goal of developing an easily manufactured, mechanically robust, pro-regenerative tendon biomaterial that addresses mechanical and biological deficits in rotator cuff injuries while avoiding a complex and laborious production process," says the lead scientist, Prof. Elmer Ker. ""We will continue to prove the significant potential of this newly developed material for the repair of large-to-massive rotator cuff injuries, as well as other soft tissue injuries, in a clinical setting."
A paper on the research was recently published in the journal Bioactive Materials.
Scientists at the University of Connecticut have previously also had success at treating torn rotator cuffs, using implantable meshes containing stem cells and graphene nanoplatelets.
