Introduction

Anterior cruciate ligament (ACL) ruptures are commonly associated with articular cartilage injuries, and the presence of these defects influences both short- and long-term outcomes. Multiple variables are predictive of this pathology including time from injury, age, and sex. Revision ACL reconstructions demonstrate higher rates of chondral injury than primary reconstructions. Successful outcomes with multiple treatment options for chondral injuries in conjunction with ACL reconstruction have been reported. On the other hand, high-grade chondral defects have the most consistent and potentially largest negative effect on long-term patient-reported outcomes; however, some natural healing response of chondral injuries following ACL reconstruction. Optimal treatment has been also controversial to expect successful results with several modalities including benign neglect. Recent studies suggest that achieving anatomic graft placement is critical to restoring native ACL function and normal knee kinematics. Knees with grafts that more closely restored normal ACL function, and thus knee motion, experienced less focal cartilage deterioration than did those that experienced abnormal knee motion. Thus, achieving anatomic graft placement is a critical factor in restoring normal knee motion and potentially slowing the development of degenerative changes after ACL reconstruction.

For evaluation of cartilage morphology, Magnetic resonance imaging (MRI) has become the preferred modality for imaging the pathology. Due to the diverse pathology, complex anatomy, and various injury mechanisms of the knee, the MRI knee protocol and sequences should ensure detection of both soft tissue and osseous structures in detail and with accuracy. Recent advances in MRI techniques allow for improved imaging in the postoperative knee changes including cartilage. As treatment and operative management techniques evolve, understanding the correct application of these advancements in MRI of the knee will prove to be valuable to clinical practice.

Content

This presentation will provide latest topics on ACL and Cartilage, which could lead to better strategic planning to prevent osteoarthritis.

The main topic are as follows:

1. How chondral lesions affect the symptoms and outcomes of patients with ACL injury.

2. Natural healing course of chondral lesions in patients with ACL injury.

3. Imaging of cartilage condition following ACL injury and reconstruction

4. How ACL reconstruction affects articular surface and the progression of osteoarthritis.

5. Emerging technologies to treat patients with the combined pathologies.

6. Future perspective.

References

1. The protective effect of anterior cruciate ligament reconstruction on articular cartilage: a systematic review of animal studies. Deckers C, Stephan P, Wever KE, Hooijmans CR, Hannink G. Osteoarthritis Cartilage. 2019 Feb;27(2):219-229.

2. Knee Imaging Following Anterior Cruciate Ligament Reconstruction: The Surgeon's and Radiologist's Perspectives. Srinivasan R, Wan J, Allen CR, Steinbach LS.Semin Musculoskelet Radiol. 2018 Sep;22(4):386-397.

3. Recurrent Instability Episodes and Meniscal or Cartilage Damage After Anterior Cruciate Ligament Injury: A Systematic Review. Sommerfeldt M, Raheem A, Whittaker J, Hui C, Otto D. Orthop J Sports Med. 2018 Jul 24;6(7):2325967118786507.

4. Factors that affect patient reported outcome after anterior cruciate ligament reconstruction-a systematic review of the Scandinavian knee ligament registers. Hamrin Senorski E, Svantesson E, Baldari A, Ayeni OR, Engebretsen L, Franceschi F, Karlsson J, Samuelsson K. Br J Sports Med. 2019 Apr;53(7):410-417.

5. Risk factors for radiographic joint space narrowing and patient reported outcomes of post-traumatic osteoarthritis after ACL reconstruction: Data from the MOON cohort. Jones MH, Spindler KP. J Orthop Res. 2017 Jul;35(7):1366-1374.

6. Effects of ACL graft placement on in vivo knee function and cartilage thickness distributions. DeFrate LE. J Orthop Res. 2017 Jun;35(6):1160-1170.

7. Surgical Indications and Technique for Anterior Cruciate Ligament Reconstruction Combined with Lateral Extra-articular Tenodesis or Anterolateral Ligament Reconstruction. Vundelinckx B, Herman B, Getgood A, Litchfield R. Clin Sports Med. 2017 Jan;36(1):135-153.

8. Outcomes and Risk Factors of Rerevision Anterior Cruciate Ligament Reconstruction: A Systematic Review. Liechti DJ, Chahla J, Dean CS, Mitchell JJ, Slette E, Menge TJ, LaPrade RF. Arthroscopy. 2016 Oct;32(10):2151-2159.

Acknowledgments

We thank Dr. Christian Latterman, Takashi Nishii and Shuji Horibe for substantial discussion in preparation.

Purpose

There have been many reports mentioned about tissue regeneration efficacy of mesenchymal stem cells (MSCs) for treatment of osteoarthritis (OA). One of the main mechanism of transplanted MSCs is the trophic effect by secretome, which is represented to exosome. The aim of this study is to evaluate the suppression effect of tissue degenerating of exosome secreted by MSCs on the treatment of OA.

Methods and Materials

Exosomes (Exos) secreted by adipose tissue derived MSCs were extracted using an ultracentrifuge method from conditioned medium (serum-free medium). Nano tracking analysis and western blots were used to identify exosomes. Exosomes were injected in the collagenase-induced OA (CIOA) mouse model and histomorphometric analyses of joints were performed by μCT and Osteoarthritis Research Society International (OARSI) score.

Results

The majority of Exos were approximately 50–150 nm in diameter and expressed CD9, CD81. Macroscopically the structure of cartilage was degenerated and subchondral bone was exposed partially in untreated group (CIOA without Exos). In contrast, much of cartilage were remain in treated group (CIOA with Exos). The area of bone resorption at the distal site of femoral epiphyseal line evaluated by μCT was suppressed 65% in treated group compared with untreated (Figure 1). Moreover histological analysis of tibias sections indicated that cartilage tissues of treated mice presented almost typical hyaline features although with a little bit superficial fibrillation. However, untreated group showed typical degenerative OA changes including superficial zone delamination and proteoglycan depletion. OARSI score of treated mice improved compared to untreated (Figure 2).

Figure 1. The area of bone resorption at the distal site of femoral epiphyseal line evaluated by μCT.

Figure 2. Histological (OARSI) score at the section of tibial plateau.

Conclusion

These results were confirmed that exosome could protect cartilage degradation. Exosome may be the next generation therapeutics for OA instead of MSC therapy.