Arthroscopy and Meniscus Surgery
The principal functions of the meniscus are load sharing and shock absorption.
What is it?
There are two types of cartilage within the knee. The first is called hyaline cartilage, and is the white, tightly adherent cartilage that is on the ends of bones within a joint. The second type is called fibrocartilage, which is rubbery and pliable. The meniscus is a crescent shaped structure that lies between the femur and the tibia on each side of the knee, and is made of fibrocartilage.
The principal functions of the meniscus are load sharing and shock absorption.
The intact fibrocartilage meniscus spreads load away from the hyaline cartilage of the bones, thereby protecting it. Damage to the hyaline cartilage leads to arthritis in the knee.The menisci transmit 50-90% of load over the knee joint, depending on knee flexion angle, femoral translation and rotation. The meniscus contributes to knee joint position sense, and also to joint stability.The outer third of the meniscus, known as the “red zone” is well supplied with blood, and has healing capacity. The inner two-thirds is known as the “white zone” and has no blood supply and has diminished ability to heal.
What’s involved?
An arthroscopy is an operation on the knee joint via “keyhole” surgery. A camera is inserted into the joint via a small 1cm incision (or “portal”), and the instruments via a second 1cm portal. Occasionally other arthroscopic portals may need to be used in addition to these.
Arthroscopy provides an unparalleled view of the knee joint, which could not be obtained without a large, invasive incision. The small incisions minimize post operative pain, allowing rapid return to function. It is usually a day-surgery operation.
Knee arthroscopy is performed under a general anaesthetic. A torniquet is inflated over the upper thigh to prevent any blood entering the knee joint space, which would hinder vision. A thin, long camera is inserted into the knee, and the image appears on a screen in the operating theatre. Instruments such as probes, shavers, scissors, and special sutures can be inserted to treat various problems within the knee.
The most common arthroscopic operation is to treat a torn meniscus. If the tear is not in a configuration amenable to repair, the torn edges must be stabilised so that they do not catch and pull, causing pain. This is done by trimming the edges of the tear to proved a smooth, round contour.
At the end of the operation, local anaesthetic is injected around the incisions, and they are each closed with a stitch or sticky strips.
Many different problems can be treated with the aid of arthroscopy. Some of treatments are listed below:
Diagnostic arthroscopy and biopsy
Meniscal trimming
Meniscal repair
ACL or PCL reconstruction
Chondroplasty (smoothing of the articular cartilage) Microfracture
Knee joint washout
Reduction of fractures of the tibial joint surface
Removal of loose bodies
Arthroscopy is not useful in treating arthritis
There are general risks associated with knee arthroscopy, as well as specific risks for meniscal trimming and repair.
General risks of surgery
These include adverse reaction to medications, pain, bleeding, infection, stiffness, blood clots in the calf (deep venous thrombosis or DVT), blood clots traveling from the calf to the lungs (pulmonary embolus).
Risks specfic to meniscal repair
There is a 20% incidence of mild pain around the repair site which may persist for several months.
The repair may not heal, requiring further surgery to either re- attempt repair, or to remove the meniscus if it is too damaged.
Risks specific to meniscal trimming
Tears may recur, particularly in degenerate menisci.
There is an increased risk of arthritis following removal of meniscal tissue.
Meniscal surgery in the presence of arthritis may not result in resolution of symptoms.
Arthroscopy provides an unparalleled view of the knee joint, which could not be obtained without a large, invasive incision. The small incisions minimize post operative pain, allowing rapid return to function. It is usually a day-surgery operation.
Post-Operative Information
Patients who have meniscal trimming only :
Most patients walk out of the hospital on the day of surgery, usually with crutches or a stick. The bulky dressing is then removed, leaving the sticky waterproof dressings intact. You may get these dressings wet in the shower. If the dressings come loose, please replace them.
The knee is allowed to bend as tolerated. Most patients can perform their usual activities after a few days. Office workers return to work after 3–5 days. Heavy manual workers may require 1–2 weeks to be able to resume work. Driving is usually possible within a week, when the knee is relatively pain free and bending easily.
There may be some knee swelling for up to 6 weeks, as well as some mild discomfort around the incisions.
Meniscal trimming is associated with a much faster return to function than meniscal suturing.The limb is usually fully recovered within 4 week.
Patients who have meniscal suturing:
Meniscal repairs must be protected for 3 months to minimise motion and stress while they heal. I generally don’t use a brace, but limit bending to 90° for 6 weeks, and don’t allow weight bearing. After 6 weeks, weight bearing is permitted, as is full bending of the knee, but loaded squatting past 90° is not allowed for another 6 weeks. Office workers will generally be able to work a week following surgery, but manual workers may be unable to work for up to 3 months. Driving is allowed when the limb which is operating a pedal is pain free and able to weight bear.