Subchondroplasty

The knee is a complex joint which consists of bone, cartilage, ligaments and tendons that make joint movements easy.  The joint surface is covered by a smooth articular surface that allows pain free movement in the joint. This surface can wear out for a number of reasons; often the definite cause is not known. 

When the articular cartilage wears out the bone ends rub on one another and cause pain. This condition is referred to as Osteoarthritis or “wear and tear” arthritis as it occurs with aging and use.

Osteoarthritis and other problems like micro fractures in the knee can lead to bone marrow lesions (BMLs). BMLs are sites of chronic inflammation just below the bone surface within the marrow and are accompanied by swelling and fluid collection (edema).  BMLs are associated with subchondral defects, insufficiency fractures and stress fractures.

Subchondroplasty is a minimally invasive procedure that is performed to repair chronic bone marrow lesions by filling them with a bone substitute material (BSM). The artificial substitute is then slowly resorbed and replaced with healthy bone, repairing the bone defect.

Subchondroplasty may be performed alone or with other arthroscopic procedures.

Indications and contraindications:

Patients diagnosed with bone marrow lesions as the primary source of knee pain may benefit from a subchondroplasty procedure.

Conservative treatments for bone marrow lesions include pain medications, crutches, knee braces, and physical therapy. However, chronic lesions that do not heal with first-line therapy treatments may require a total knee replacement surgery.  Subchondroplasty is a minimally invasive alternative treatment for chronic bone marrow lesions.

Subchondroplasty is, however, contraindicated in patients with a BMI (body mass index) greater than 40 or those with severe misalignment of the knee joint.

Symptoms

Symptoms of bone marrow lesions include the following:

1. Long-lasting knee pain
2. Stiffness of the knee joint
3. Discomfort when standing or walking
4. Faster cartilage destruction

Diagnosis

The diagnosis of bone marrow lesions is based on clinical examination and diagnosis of chronic pain. BMLs are visible on an MRI but not on an X-ray. Advanced imaging studies such as Fat saturated T2-weighted MRIs may be recommended to view bone marrow edema. 

Surgical procedure

The subchondroplasty procedure is performed under fluoroscopy to accurately target the chronic BMLs. Fluoroscopy provides the surgeon with intraoperative real time X-ray images of the surgical area to guide the surgeon.

1. The procedure is usually carried out under general anesthesia.
2. A semi-circular reference frame is placed relative to the patient’s tibia or shin bone. This allows your surgeon to target the location of the lesions from a range of trajectories. A pin is inserted into the skin to the bone under fluoroscopic imaging using the frame.
3. A cannulated drill is then used to advance the pin to the desired depth in the bone.
4. The frame is then removed leaving only the pin.
5. A cannula is placed over the pin and is slid into the bone until it is firmly placed.
6. A delivery syringe filled with the bone substitute is attached to the back of the cannula and injected into the bone
7. A trocar (a sharp pointed instrument) is inserted into the cannula to push the left behind bone substitute into the bone.
8. The cannula is then removed.
9. Finally, proper placing of the bone substitute is confirmed using the fluoroscopic imaging and the incisions are closed.

Post-operative care

After surgery, you will experience some pain and discomfort in the operated area for 1-2 days. Your doctor will prescribe pain medications to help relieve pain and make you feel comfortable.

You will be instructed to strictly adhere to the following post-operative guidelines for faster recovery:

1. Keep the incision area clean and dry.
2. Use crutches for 1-2 weeks after the surgery to reduce weight bearing on the operated leg.
3. Start physical therapy to regain strength and mobility of the knee.

Call your doctor if you have fever of 101 degrees or higher, redness, swelling, or intolerable pain.

Advantages

Subchondroplasty is a minimally invasive procedure with the following advantages:

1. Patients usually go home the same day.
2. Fast recovery and quick return to normal activities.
3. The procedure does not hinder other future treatment options.