Enhancing Rotator Cuff Repair in Rabbit Osteoporosis With Chitosan Quaternary Ammonium Salt–Coated Nickel-Titanium Memory Alloy Anchors

Background: For patients with osteoporosis and rotator cuff tears, there is still no consensus on current treatment methods. The material, structure, and number of anchors have important effects on the repair outcome. Purpose: To investigate the use of chitosan quaternary ammonium salt–coated nickel-titanium memory alloy (NTMA) anchors to treat rotator cuff injury in shoulders with osteoporosis in a rabbit osteoporosis model. Study Design: Controlled laboratory study. Methods: A novel winged NTMA anchor was designed to test in normal and osteoporotic bone models in vitro. These models were assessed for maximum failure load and bone damage in various traction directions. A chitosan–sodium alginate composite was coated onto NTMA anchor surfaces using glutaraldehyde cross-linking and electrostatic layering techniques. An osteoporotic rabbit model was created using ovariectomy combined with glucocorticoid treatment. A rabbit model with acute injury to the supraspinatus muscle was established and repaired using titanium alloy anchors, NTMA anchors, and coated NTMA (CNTMA) anchors. To evaluate the efficacy of the anchors, biomechanical testing and staining with hematoxylin and eosin were performed 6 and 12 weeks after surgery. A micro–computed tomography scan was performed 12 weeks after surgery. Results: In the osteoporotic bone model, NTMA anchors exhibited greater failure loads than titanium anchors under 45° and 90° traction forces ( P < .05). The surface-modified material showed a lower contact angle compared with unmodified material. Cell Counting Kit-8 (CCK-8) assays showed that the composite coating promoted osteoblast proliferation. The CNTMA anchor group exhibited the greatest maximum failure load at each time point. Hematoxylin and eosin staining revealed greater trabecular thickness in the CNTMA anchor group than in the other groups at 6 and 12 weeks after surgery. At 12 weeks after surgery, micro–computed tomography revealed an increased number and thickness of bone trabeculae in the NTMA anchor group, along with a widened trabecular gap ( P < .05). After the NTMA anchor biplane unfolded, the gap between the biplane and anchor showed bone tissue growth. Conclusion: Chitosan quaternary ammonium salt–coated NTMA anchors enhanced fixation strength and promoted local osteogenesis during osteoporotic rotator cuff repair, suggesting that the use of these anchors facilitates the repair of osteoporotic rotator cuff injuries in osteoporotic bones. Clinical Relevance: Innovations in anchor nailing may be effective in reducing rates of repair failure for rotator cuff tears combined with osteoporosis.