Subchondroplasty (Zimmer) – Delaying Joint Replacement
Subchondroplasty is the procedure in which the bone adjacent to the cartilage is drilled for decompression and filled with bone cement or paste with osteoconductive properties. It is done in patients who present with pain around the knee and are found to have a stress reaction (sometimes called a fracture) underneath the articular cartilage. These patients may or may not have a history of fall, accident, injury or twisting of the knee. They may also have joint line tenderness secondary to pathology inside the knee like a meniscal tear.
These patients are initially treated conservatively with antiinflammatory medications, ice, elevation and compression. If they are not relieved with conservative means, advance imaging including x-ray and MRI may be needed. If the patients show evidence of a bone marrow lesion (BML) or bone marrow edema (BME) on an MRI, then these patients may be a candidate for subchondroplasty.
A bone marrow lesion or a bone marrow edema adjacent to the cartilage of the knee joint is typically seen as a cloudy white area on the T2 and STIR sequence of the MRI. It represents stress reaction and edema in the area. It is symbolic for stress fracture localized to the bone underlying the cartilage. When these stress fracture type lesions are not able to heal with conservative means then invasive procedure like subchondroplasty may be needed.
The reason for nonhealing of these lesions may be increased pressure in the area due to the edema, which is taken care by drilling a hole and letting it to decompress. The hole is filled up with bone cement or paste to support and allow healing. Research and evidence have shown that these bone marrow lesions are the strong predictor of knee arthroplasty within three years of presentation.
Further research has also shown that subchondroplasty was able to delay and defer knee replacement in such patients. The procedure hence not only takes care of the pain and disability due to the pathology, but also helps in delaying or preventing the need for a knee replacement surgery in the future.
This surgery is done in an outpatient setting. It is usually combined with arthroscopic examination of the knee, which helps to look inside the knee and take care of any pathologies, which may or may not be diagnosed on the MRI which include meniscal tear or cartilage lesions. It also helps in preventing complications of subchondroplasty, that is extravasation of the material into the joint.
Subchondroplasty is done under x-ray imaging control in the operating room. The patients usually will have two to four stitches after the procedure. The patients are sent home the same day within a couple of hours after procedure. They will require the need for assistive device like crutches for ambulation for 3-4 weeks.
They are sent home with pain medications and asked to follow within a week with the surgeon. They are asked to elevate and ice and use pain medications as directed to take care of the pain and swelling in the knee joint. The patients are allowed to ambulate as well as do activities of daily living as tolerated.
They are usually seen in one week and physical therapy for the knee is started at that time. It may take up to 8-10 weeks to heal completely.
IntraOsseous Bioplasty (Arthrex)
Bioplasty is a variation in which a wider decompression is done and the drill hole is filled with biologic material in the form of Platelet rich Plasma (PRP) mixed with Demineralized Bone Matrix (DBM). Both procedures have shown good results in carefully selected patients and help in preventing rapid deterioration of the joint and delay or prevent joint replacement surgery.
Subchondroplasty or IntraOsseous Bioplasty is a viable and evidence-based procedure which helps not only giving pain relief, but also in delaying or preventing knee replacement.