World Arthritis Day on October 12 marks the beginning of a week to highlight the impact of arthritis. Dr. A.K. VENKATACHALAM writes about the benefits of articular cartilage surgery, which can halt the progress of limited cartilage damage to full-fledged osteo-arthritis.
High impact injury to the joint occurs in sports.
AT least 240 million people all over the world are living with one of the most under-rated incurable diseases arthritis. That's just the tip of the iceberg. Many countries including India have not been able to assess the number of people living with arthritis or the effects on their health economy. The pain and disability associated with this disease have far reaching consequences for families, employers, governments and society in general.
The past three decades have seen a rising number of joint replacements for end-stage arthritis. Articular cartilage damage is the hallmark of arthritis. The articular cartilage is a smooth, shining, plastic tissue that covers the mobile joints of the limbs and spine. Depreciation and degeneration of this tissue leads to the well-known condition, osteoarthritis. This commonly affects the joints of the knee, spine, ankle, shoulder and less commonly the hips in the Indian population. Articular cartilage is rich in water, proteo-glycans, proteins and collagen. It is avasuclar (lacking blood vessels) and aneural (lacking nerve endings). It derives its nutrition from the synovial fluid. Its constituents are hydrophilic and synovial fluid is driven in and trapped in its matrix on loading. This makes it turgid, which contributes to the shock absorber-like function of the cartilage. It is a precious tissue like the nervous tissue of the brain, spinal cord and heart muscle, as it cannot heal like the other tissues.
There is a balance between the synthesis and destruction of the articular cartilage. The capacity to regenerate reparative articular cartilage diminishes with age. When the articular cartilage is damaged, there is little chance for its repair. Focal areas of damaged cartilage set off a sequence of degenerative changes leading to osteo-arthritis of the joint and the need for a total joint replacement.
Mechanisms of damage
Injuries to the articular cartilage of the knee can be used as an example and knee injuries are very common. Also the same principles apply to the treatment of other joints like the hip, ankle, shoulder and elbow.
A high impact mechanical injury to the knee occurs in sports. This is usually in association with a ligament injury. Anterior cruciate ligament (ACL) injuries of the knee are the most common ligament injury. Bruising of the articular cartilage of the femur (thigh bone) is also seen on the MRI scans of these patients. Also repeated and excessive overloading of the joint can lead to articular cartilage damage. This could be due to joint deformities like bow legs and knock knees, which produce a misalignment and overload on one half of the joint. Another reason could be obesity.
Thermal injury is another mechanism responsible for cartilage injury and is inadvertently applied in the conservative treatment of joint pain. (Short wave diathermy is the main offender.) Lasers used in arthroscopic surgery can cause cartilage damage.
Chemical injury occurs due to infections like septic arthritis (pus) and inflammatory diseases like rheumatoid arthritis.
The only known physiological ways of maintaining health of the articular cartilage is regular exercise. This not only tones the surrounding muscles but also maintains its health by forcing the synovial fluid to the cartilage.
The articular cartilage can be evaluated surgically by arthroscopy or by imaging techniques like MRI, molecular imaging and optical coherence tomography (OCT).
Once articular cartilage damage has been diagnosed, the surgeon is confronted with two options to treat it or ignore it. Long-term studies show that it may be better to treat the larger lesions in active individuals. There are two surgical options reparative or restorative. The latter involves substitution of the lost tissue by the same tissue. This can be obtained from a cadaveric source (allograft) or be harvested from the patient's body (autograft). Cartilage cells from the patient's body are grown in a culture and reimplanted in the patient's joint in an open operation called autologous chondrocyte implantation (Acl). This technique is very expensive and is not yet available in India.
In the reparative technique, a reparative tissue is generated by surgery. There are many techniques involved and some can be done by keyhole incisions. Both techniques involve an extended recovery process. These operations are applicable to focal areas of cartilage damage in other joints like the hip, ankle and shoulder.
Autologous chondrocyte implant can be introduced in India with the help of companies or university departments who can provide cartilage cells grown in tissue culture.
Under gene therapy, genes that can code for cartilage enhancing growth factors can be used to synthesise them. These growth factors can be delivered to target cells and tissues.
Functional tissue engineering is an approach to enhance tissue regeneration and provides the possibility of producing tissue that is bio-mechanically, bio-chemically and histologically similar to the native articular cartilage.
Stem cell manipulation involves the differentiation of foetal umbilical cord cells into different tissue types like cartilage, tendon or bone.
Articular cartilage defects are precursors of osteo-arthritis. Early methods of detection should include an evaluative arthroscopy and special MRI scans. Current surgical techniques of repair and regeneration can be adapted to suit the patient's needs. The patient can continue to use his own joint and the need for a total joint replacement averted.
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