Arthroscopy: The Journal of Arthroscopic and Related Surgery
Volume 25, Issue 12 , Pages 1427-1434.e1, December 2009

Influence of Hydroxyapatite-Coated and Growth Factor–Releasing Interference Screws on Tendon-Bone Healing in an Ovine Model

  • Yan Lu, M.D.

      Affiliations

    • Comparative Orthopaedic Research Laboratory, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, Wisconsin, U.S.A.
    • Department of Orthopedics and Rehabilitation, University of Wisconsin-Madison, Madison, Wisconsin, U.S.A.
    • Corresponding Author InformationAddress correspondence and reprint requests to Yan Lu, M.D., Comparative Orthopaedic Research Laboratory, Department of Medical Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, 2015 Linden Dr, Madison, WI 53706-1102, U.S.A.
    • ,
  • Mark D. Markel, D.V.M., Ph.D.

      Affiliations

    • Comparative Orthopaedic Research Laboratory, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, Wisconsin, U.S.A.
    • ,
  • Brett Nemke, B.S.

      Affiliations

    • Comparative Orthopaedic Research Laboratory, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, Wisconsin, U.S.A.
    • ,
  • J. Sam Lee, Ph.D.

      Affiliations

    • Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, Wisconsin, U.S.A.
    • ,
  • Ben K. Graf, M.D.

      Affiliations

    • Department of Orthopedics and Rehabilitation, University of Wisconsin-Madison, Madison, Wisconsin, U.S.A.
    • ,
  • William L. Murphy, Ph.D.

      Affiliations

    • Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, Wisconsin, U.S.A.
    • Department of Pharmacology, University of Wisconsin-Madison, Madison, Wisconsin, U.S.A.

Received 13 November 2008; accepted 10 June 2009. published online 09 November 2009.

Purpose

Our purpose was to determine whether a bioresorbable interference screw coated with a hydroxyapatite-based mineral layer designed to release an engineered peptide growth factor (linkBMP-2 [where “BMP-2” indicates bone morphogenetic protein 2]) improved tendon-bone healing compared with a screw without coating.

Methods

Tagged linkBMP-2 peptides were used to quantify binding efficiency and release kinetics on 9 mineral-coated BIORCI screws (Smith & Nephew, Andover, MA). Fourteen mature female sheep were used in this study. In each of the 14 sheep, each stifle was randomized to either receive a linkBMP-2–coated or uncoated interference screw (n = 14 per treatment). The sheep were euthanized at 6 weeks after surgery. Eight sheep were subjected to biomechanical testing for peak load at failure and stiffness, and six sheep were used for histologic analysis according to a semiquantitative scoring scale.

Results

The linkBMP-2 molecule bound efficiently to the surface of mineral-coated interference screws. Over 80% of the initially bound linkBMP-2 was released during a 6-week time frame in vitro. Peak load at failure in the linkBMP-2–coated interference screw group (mean ± SD, 449.3 ± 84.7 N) was not significantly different from that in the uncoated group (421.0 ± 61.8 N) (P = .22). Stiffness in the linkBMP-2–coated interference screw group (157.3 ± 39.6 N/mm) was not significantly different from that in the uncoated group (140.6 ± 20.3 N/mm) (P = .12). Histologic analysis showed that the tendons in the linkBMP-2–coated interference screw group had higher scores (better) than the uncoated group. In the linkBMP-2–coated interference screw group, mesenchymal cells were present at the interface between screw and tendon, whereas these cells were not present in the uncoated group.

Conclusions

We found that linkBMP-2 can be bound onto a mineral-coated BIORCI interference screw surface and subsequently released from the screw surface in a sustained manner. The histologic result of this study showed that the linkBMP-2–coated interference screw significantly improved the histologic scores of early tendon-bone healing in this sheep model.

Clinical Relevance

This linkBMP-2 coating material may improve early tendon/ligament fixation.

Key Words: rhBMP-2, ACL, Tendon-bone healing, Growth factors, Interference screw, Sheep

 

 Supported by the Wallace H. Coulter Foundation (Translational Research Partnership Grant) and the National Institutes of Health (R03AR052893). The authors report no conflict of interest.

 

Note: To access the supplementary tables accompanying this report, visit the December issue of Arthroscopy at www.arthroscopyjournal.org.

PII: S0749-8063(09)00520-9

doi:10.1016/j.arthro.2009.06.008

Arthroscopy: The Journal of Arthroscopic and Related Surgery
Volume 25, Issue 12 , Pages 1427-1434.e1, December 2009