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1. Fundamentals of Cartilage Repair
Dr. RAJATJANGIR
Professor, Mahatma Gandhi Hospital, Jaipur
Arthroscopy and Sports Injury

2. ARTICULAR CARTILAGE
STRUCTURE
FUNCTION
METABOLISM
BIOLOGY –SURGICAL REPAIR

3. INTRODUCTION
Load-bearing surfaces of all synovial joints
Highly organized structure
Biomechanical properties
to withstand multiple forces created during movement.

4. Articular cartilage
5 % cells – chondrocytes 65-85 water – more at surface
95% - matrix Collagen 10-20 % Type II Half Life 25 years
Proteoglycans- 10% weight Elastic compressive
Negatively Charged- Traps water – Mechanical properties
Karuppal R. Current concepts in the articular cartilage repair and regeneration. J Orthop. 2017 May 19;14(2):A1-A3. doi: 10.1016/j.jor.2017.05.001. PMID: 28559648; PMCID: PMC5440635.

5. ARTICULAR CARTILAGE
Lack of blood vessels and nerves
limited healing potential
cells have minimal mitotic activity & matrix lacks a vascular supply
Karuppal R. Current concepts in the articular cartilage repair and regeneration. J Orthop. 2017 May 19;14(2):A1-A3. doi: 10.1016/j.jor.2017.05.001. PMID: 28559648; PMCID: PMC5440635.

6. MOLECULAR STRUCTURE
Proteoglycans
Glycosaminoglycans
Chondroitin Sulphate
Keratin Sulphate
LINK to protein Core
Link Proteins - HA

7. CHONDROCYTES
5% of wet weight
Protein synthesis
PGs Collagen & Enzymes
Derived from C blast Cells – least active in calcified zone
Lacunae

8. FUNCTION
Friction Free Surface – Coefficient 0.002
Fluid Film, elastic deformation, efflux and influx of fluid and synovium
Lubrication- Elastohydrodynamic, Boundary, weeping, Hydrodynamic
Load Sharing, Deforming

9. Gilbert, S. J., & Blain, E. J. (2018). Cartilage mechanobiology: How chondrocytes respond to mechanical load. Mechanobiology in Health and Disease, 99-126.

11. UNIQUE PROPERTIES
Deform when loaded
Reform when unloaded
Thus distributes load and thereby minimizing stresses on subchondral bone
Compressibility
Low friction coefficient .002 a smooth SURFACE

12. Collagen reorganization in cartilage under strain probed by polarization sensitive second harmonic generation microscopy, Volume: 16, Issue: 150, DOI: (10.1098/rsif.2018.0611)
Most Collagen, Greatest Tensile strength,
PGs Low, Superficial cells- Lubrication
Increased Chondrocyte Volume
PGs Compression
Opposes Shear
HA crystals, Anchors

17. ROLE OF SUBCHONDRAL BONE
as a load- sharing structure and as a nutritional support has been heavily ignored in the
medical literature.
comprises of two major parts: the subchondral bone plate and the subchondral spongiosa
Important role in natural healing of the cartilage through its various properties like nutritional
properties, load-bearing properties and as a warehouse of cartilage cells and growth factors.

18. Marrow stimulation techniques like micro- fracture (MF) relied on the SC bone for recruitment of the autologous
stem cells and formation of a super clot. However implications of MF holes on the SC bone that lead to thickened
SC bone, SC cysts, and internal osteophyte post-MF.
Similarly for OCT the bone was merely used as a carrier and to provide a press-fit fixation. The technique stressed
on the importance of articular congruency but never stressed the importance of the SC bone congruency.
ACI continued to evolve in different generations but with a very little attention to SC reconstruction until recently
SC bone is important

19. ONE OSTEOCHONDRAL UNIT
• Cartilage gets its nutrition through diffusion from the synovial
fluid
• Substantial evidence to support the presence of a vascular supply
from SC bone to the cartilage
• Presence of canals penetrating the SC bone plate and reaching
into the calcified cartilage layer up to the tidemark.
• The SC bone actually allows a direct supply of nutrition to the
calcified cartilage through small vascular channels while it also
allows indirect supply of nutrition to the uncalcified cartilage by
permeable diffusion
•

20. An steochondral unit
calcified cartilage,
cement line
subchondral bone plate
the subarticular spongiosa
all the four layers having a superficial covering of
articular cartilage.

21. The soil-plant relationship vis-à-vis the subchondral bone-cartilage relationship.
As the different layers of the soil are being eroded, the plantation above is getting uprooted. Similarly, an unhealthy subchondral bone can cause damage to the
overlying cartilage. Also look at the more compact and closely woven layers of the soil near plantation; a similar relation exists between subchondral bone plate
and the calcified cartilage. (Photo courtsey: Dr Deepak Goyal)

22. SC bone provides a
• strong base for the overlying cartilage
• scaffold to the collagen fibers
• supplies necessary nutrition
• ability to withstand the shear and the compressive forces acting
on the cartilage
The cartilage, in turn, provides
• the necessary covering the articular bone,
• acts as a shock absorber
• maintaining the biomechanical & physical equilibrium.

23. SC bone - Warehouse of GF and Cells
• Chondrocytes are the main elements of cartilage; however, they originate from the
undifferentiated mesenchymal marrow stem cells.
• These cells convert into chondroblasts while passing through the calcified cartilage, and
then further convert into chondrocytes in the uncalcified layer and get isolated in the
lacunae.
• Chondrocytes in the lacunae are, in fact, prisoners in their own home. They can divide but
cannot proliferate. Hence the bone marrow stem cells continue to be the only source of
fresh chondrocytes.
• Without the ability of the SC bone to provide the undifferentiated stem cells, and their
further ability to differentiate into the chondroblasts, the natural healing of a day-to-day
wear cannot take place.

24. SC bone -growth factors
.
• Various growth factors like IGFs, BMPs, FGFs, and TGF B
• remodeling process and in the cartilage healing

25. • An unstable and probably unviable SC bone causes the overlying cartilage
to stop functioning in its normal capacity.
• Gradually, the whole OC unit separates with the overlying cartilage.

26. • Certain diseases of the cartilage are actually the diseases of
the subchondral bone rather than the disease of the
cartilage per se. It is akin to a bad soil causing loss of healthy
plantation on it.
• Osteochondritis dissecans (OCD) is one such disease where
the pathological process starts in the SC bone, gradually
causing the separation of the affected bone from the
surrounding healthy SC bone

27. • There is always an attempt by the SC bone to heal the damaged cartilage if it gets
damaged by the forces beyond the physiological limits; however, it may not
always succeed.
• A proper attention to the subchondral bone is thus important to maintain a healthy
cartilaginous tissue under the physiological stresses and to regenerate a healthy
cartilage in case of cartilage damage

28. GOALS – CARTILAGE REPAIR
• Mechanical Functional repair tissue – Ideal Hyaline Cartilage
• Durable
• Good Incorporation

29. Marrow
Stimulation
Cartilage
Transplant
Chondrocyte
Transplant
Allograft
• Availability
• Cost
• Disease
Transmission
Fibrocartilage
Type I
Short lasting
Hyaline Cartilage
Hyaline like
CARTILAGE REPAIR SC bone is important

31. THANKS