Cartilage resurfacing at Tunbridge Wells Hospital

What is cartilage resurfacing?

Cartilage resurfacing covers a range of techniques to repair or replace damaged cartilage in a joint, most often the knee, where it's worn away by injury or general wear and tear. Depending on the size and depth of the damage, this can mean smoothing the surface, encouraging new tissue to grow, or replacing the area with a small implant.

What conditions does it treat?

Cartilage resurfacing treats damage to articular cartilage, the smooth tissue that lets your joint move with very little friction. Because this cartilage has no blood supply, it can't repair itself, so damage tends to get worse with time rather than better, and can eventually progress to exposed bone and arthritis.

Damage usually causes pain, swelling, stiffness and reduced movement, and is most often caused by a sporting injury or general wear and tear.

What are the benefits of cartilage resurfacing?

Resurfacing techniques aim to relieve pain, restore function and delay or prevent the onset of arthritis, without needing a full joint replacement.

Are there different types of surgical approaches?

• Arthroscopic radiofrequency chondroplasty: for unstable or rough cartilage flaps that aren't yet severely damaged, a probe is used to smooth and stabilise the surface through keyhole surgery.
• Microfracture or nano-drilling: for small, full-thickness defects under 2cm² in size, tiny holes are made in the bone beneath the cartilage, allowing blood and bone marrow to form a clot that matures into a repair tissue called fibrocartilage. Newer nano-drilling uses smaller, 0.9mm holes rather than the older 2mm technique, causing less damage to the bone underneath.
• Autologous chondrocyte implantation (ACI/MACI): a 2-stage technique in which cartilage cells are harvested by keyhole surgery, multiplied in a laboratory over about 6 weeks, then implanted in a second operation and held in place by a membrane.
• Autologous membrane-induced chondrogenesis (AMIC): a single-stage alternative to ACI, combining nano-drilling with a membrane that supports new tissue growth, giving similar results to ACI for less cost and only 1 operation.
• Focal resurfacing implants: the damaged cartilage and bone are removed and replaced with a small metal or polymer implant that restores a smooth surface.

Resurfacing is generally suitable for younger patients with a single, focal area of damage, rather than widespread arthritis, and the age cut-off for some cell-based procedures is currently 55. It isn't usually suitable if the shock-absorbing cartilage (the meniscus) is also badly damaged or missing, or if your knee is misaligned or unstable, though these problems can sometimes be treated at the same time.

What happens before the operation?

Your surgeon will assess the size, depth and location of your cartilage damage, often using an MRI scan, and may also examine the joint with a camera (arthroscopy) to plan your treatment. Detailed scans like these matter because hyaline cartilage doesn't show up on an X-ray.

If you also have a meniscus or ligament problem, such as an ACL tear, this is usually treated at the same time as your cartilage surgery, or beforehand.

What happens during the procedure?

1. Most procedures start with an arthroscopy: your surgeon makes 2 or 3 small puncture cuts around the joint and uses a camera to examine the cartilage damage closely.
2. Depending on what they find, they may smooth and stabilise the area there and then using a radiofrequency probe, or make tiny holes in the bone beneath the cartilage (nano-drilling) to trigger a natural healing response.
3. For larger defects, a sample of your cartilage may be taken during this first operation and sent to a laboratory to be grown and multiplied, ready for a second operation several weeks later.
4. In a second-stage operation, or straight away if the technique only needs 1 stage, the treated area is covered with a membrane or scaffold to protect and support new tissue growth.
5. For a focal resurfacing implant, your surgeon makes a cut to access the joint directly, removes the damaged cartilage and bone, and fits a small metal or polymer implant to restore a smooth surface.

Some procedures need more direct, open access to the joint rather than keyhole surgery; your surgeon will explain which applies to you.

What does recovery look like?

Recovery is generally quicker and less painful after keyhole procedures than after open surgery. Two-stage techniques such as ACI involve a longer overall process, since your cartilage cells need around 6 weeks in the laboratory between the first and second operations.

If you have a focal resurfacing implant, you'll have regular follow-up appointments afterwards, since there isn't yet enough long-term evidence about how this technique performs, so your care team will want to check how well it's working.

Whatever technique you have, returning to high-impact activities such as running or contact sport isn't usually advised afterwards, since cartilage surgery aims to protect the joint rather than fully restore it to its original state.

What are the risks and complications?

Some techniques carry their own specific drawbacks. The original microfracture technique can damage the bone beneath the cartilage and lead to unwanted bony overgrowths, though newer nano-drilling causes less of this problem. Early, first-generation ACI, which used a patch of the body's own periosteum tissue, could sometimes cause overgrowth of new tissue at the repair site; newer generations of ACI use collagen patches instead.

The repair tissue formed by microfracture or nano-drilling, called fibrocartilage, isn't as strong or durable as your original cartilage, and results can decline in the years after the 5-year mark.