Meniscal tears have a significant capacity for intrinsic repair.

The healing potential of meniscal tears mainly depends on the location of the tear. The vascularity of the periphery of the meniscus is a major factor contributing to meniscal healing but newer research highlights the importance of multiple other factors affecting meniscal healing. preservation and even restoration

Meniscal Healing
The understanding of meniscal healing has evolved since the description by King in 1936 of meniscal healing in dogs. The importance of meniscal preservation has also been better understood since Fairbank’s classic paper in 1948. It is essential to focus our attention in increasing the scope of meniscal repair and understanding meniscal healing in greater detail. Just suturing meniscus on its own does not increase the healing rate of a meniscus.

 

Enhancing factors for meniscal healing

  • Vascularity
  • Proliferating synovial membrane
  • Concomitant ACL reconstruction
  • Fibrin clot
  • Trephination
  • Meniscal rasping
  • Conduit
  • Hyaluran
  • Suturing?
  • Cell therapy?
  • Vascular endothelial growth factor?

Studies in rabbits show that the blood flow to the menisci was increased fivefold 4 weeks post injury; this increase was prevented by immobilization. The vascular index of the menisci was also increased threefold by injury, but not significantly reduced by immobilization. When the healing rates of menisci at the periphery, body, and rim were compared, incisions at the periphery healed significantly better than incisions at the meniscal body and central rim regions. Animal studies with explants from the avascular inner zone and vascular outer zone of the meniscus exhibit similar healing potential and repair strength in vitro

The difference in healing with regard to the type of incision, either longitudinal or transverse, was not statistically significant.

Repair seemed to be significantly influenced by the proliferating synovial membrane. Okuda (1999) in a bilateral rabbit meniscal study assessed the role of meniscal rasping. Two to 4 weeks after surgery, the hypertrophic synovium was observed invading from the parameniscal region to the injured portion. Eight to 16 weeks after surgery, the tear was almost completely healed. In contrast, neither hypertrophy of the synovium covering the tear nor healing was induced in the control meniscus. The mechanical test showed that there was a significant difference in the tensile strength and the stiffness of the injured portion between the rasped meniscus and the control meniscus.

Zhang showed that the addition of trephination to suturing improves meniscal repair potential due to improved vascularity.

  • Inhibiting factors
  • IL-1
  • TNF-alpha
  • Movement?
  • Weight bearing?

In a study where cylindrical explants were harvested from the outer one-third of medial porcine menisci, the presence of IL-1 or TNF-alpha inhibited repair despite the presence of abundant viable cells.

There is no proof that immobilisation or avoiding weight bearing improves healing rate, but studies testing healing strength at 6 weeks suggest that the mean scar strength was 19% (no therapy), 26% (suture), and 42.5% (fibrin glue) of the value measured in the equivalent region of the intact contralateral controls. Hence avoiding weight bearing and impact activities during early stages is likely to reduce gapping and failure due to incomplete healing.

Repair tissue
Fundamental elements of healing are fibroblasts, blood vessels and collagen. The fibrovascular scar tissue extends up to the synovium as shown by Arnoczky and is well established by 10 weeks.

Does age of tear affect healing
Henning suggests that repairs of tears of less than two months’ duration from the time of injury to surgery result in significantly higher healing rates than those of more chronic tears. More recently, Kotsovolos. (Arthroscopy 2006), in a study on 58 meniscal repairs using Fast-Fix showed that chronicity of injury does not affect outcome. He had a 90% success rate.

References

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  • Fairbank TJ: Knee joint changes after meniscectomy. J Bone Joint Surg Br 30:644-670, 1948
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  • Klompmaker J, Jansen HW, Veth RP, et al: Porous polymer implant for repair of meniscal lesions: A preliminary study in dogs. Biomaterials 12:810-816, 1991
  • Hennerbichler A, Moutos FT, Hennerbichler D et al. Interleukin-1 and tumor necrosis factor alpha inhibit repair of the porcine meniscus in vitro.Osteoarthritis Cartilage. 2007 Sep;15(9):1053-60.
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