Case history: surgery to regrow torn knee pad

PUBLISHED : Tuesday, 11 December, 2012, 12:00am
UPDATED : Tuesday, 11 December, 2012, 12:06pm

William, 33, lived a high-octane life working in the advertising industry. In his leisure time, he got his thrills from sports such as wakeboarding, adventure racing, hockey and scuba diving.

In 2006, William (whose full name has been withheld for reasons of patient confidentiality) twisted his knee while wakeboarding, which caused a large tear in the meniscus of his left knee.

A human knee has two menisci, which are crescent-shaped pads made of fibro-gelatinous materials located between the thigh bone (femur) and shin bone (tibia). They are the shock absorbers of the knee joint and help keep it stable.

Meniscal tears are commonly known as torn cartilage in the knee. Moderate to severe tears might result in a "pop" sound when the injury occurs. Meniscal tears might cause pain, swelling and stiffness in the knee, which can also suffer limited range of motion or might even give way.

The tear on the inside of his left knee was severe enough that doctors had to trim the damaged portion, leaving him with only about half of the meniscus. Each meniscus is divided into a "red" zone and a "white" zone. The red zone is the portion closest to the outside of the knee and enjoys an abundant blood supply. Minor injuries to this part of the meniscus may not need treatment and will heal on their own with rest. Larger tears can be surgically sutured and repaired.

The white zone is the part of the meniscus closest to the centre of the knee joint and has no direct blood supply. Without a blood supply, the meniscus is unable to heal. Severe injuries to this part of the disc, such as the type of tear in William's case, typically require surgery - a partial menisectomy - to remove the damaged portions.

After the surgery, William was able to return to his high-impact sports. But six years later, he started feeling intermittent pain in the same knee. He consulted Dr Terence Chan Wai-kit, a specialist in orthopaedics and traumatology, about his discomfort.

Magnetic Resonance Imaging (MRI) scans showed that the cartilage covering the ends of William's femur and tibia inside the knee joint were starting to degenerate. The removal of half of one meniscus meant that the knee was less able to redistribute shock and impact, thereby transferring the stress to the cartilage and wearing it out prematurely.

In time, William will face increasing knee pain. There will also be an increased risk of early onset osteoarthritis, which is joint inflammation arising from cartilage wear. To extend the lifespan of the knee, Chan told William he'd have to give up high-impact sports and settle for activities such as walking, cycling and swimming. To a thrill-seeking athlete, this was devastating.

Chan says other treatment options when knee degeneration and pain become severe include corrective high-tibial osteotomy, an operation in which the top of the tibia is broken to realign the bone into a position that helps relieve pressure in the knee joint. Another option is to replace the weight-bearing surfaces of the knee joint.

In the US, transplants using menisci from cadavers are performed on patients. But this is not an option in Hong Kong, where law forbids the trading of organs.

In the past three to four years, European doctors have started using a new treatment where a synthetic scaffold is used to replace the damaged part of the meniscus. The scaffold is made of a special material that stimulates the regeneration of meniscal tissue into the scaffold.

The synthetic material slowly biodegrades over five to six years as more meniscal tissue grows and replaces the material. In William's case, it held the promise that he would be able to enjoy his lifestyle for many more years to come.

Chan roped in his fellow specialist in orthopaedics and traumatology, Dr Kong Chi-chung, to investigate the possibility of employing this method for William. Kong says this surgery is not for everyone. Candidates must be between 18 and 50 years old to ensure that the bones and joint are fully mature, and that the body still has optimal regenerative powers.

The post-surgical rehabilitation process is long and requires a firm commitment from the patient to endure the process. Patients will not be able to participate in sports for at least a year while the meniscal tissue regrows.

Finally, the patient's knee must also be in a stable condition, and the shape and alignment of the bones and joint must be normal. Any cartilage degeneration must not be too advanced.

William met all the criteria. Even so, he took six months to consider all the factors before he agreed to the surgery, which had never been performed in the Asia-Pacific region. The inventor of the surgery, Professor Rene Verdonk, flew in from Belgium to assist with the 90-minute keyhole surgery.

Small channels were made in William's remaining meniscus so that more nutrient-rich blood could reach the implant and promote tissue regeneration. Then, a piece of the scaffold was trimmed and shaped to replace the missing portion of his meniscus, and sutured to his own meniscus to hold it in place.

William now faces a year of physiotherapy. In the initial two weeks, he wore a special knee brace that only enables a 30-degree range of motion. This progressively increases to 90 degrees over six weeks. He also has to use crutches for the first three weeks after surgery.

Over the next five weeks, he will slowly increase the weight loading on his knee, before trying to walk normally at eight weeks after surgery. For the first three months, he has to see a physiotherapist once or twice a week. Depending on his progress, he will eventually see her once every two weeks.

After about six months, William will be able to start light exercises such as swimming and other aquatic exercises, and using a stationary bicycle or cross-trainer in the gym. At nine months, he will probably be able to start gentle jogging, and make a gradual return to his sports after a year.

Despite the long road to recovery, the success of this treatment will enable William to regain his active lifestyle and longevity of his knee joint.