The goal of total knee arthroplasty is to relieve the pain of the patient and restore joint function. Although total knee replacement, called arthroplasty, is an excellent option for patients with osteoarthritis of the knee, there are still other options. Patients with osteoarthritis confined to a single knee compartment may be candidates for unicompartmental knee arthroplasty (also called partial arthroplasty).
Unicompartmental knee arthroplasty is the right choice for a small proportion of patients with osteoarthritis. The orthopedic surgeon recommends unicompartmental knee arthroplasty if arthritic lesions are confined to a single knee compartment.
The knee is divided into 3 main compartments: the inner compartment, the outer compartment and the patella compartment (the front of the knee between the patella and the femur).
In unicompartmental knee arthroplasty, only the damaged knee compartment is replaced with an artificial implant – or prosthesis – of metal and plastic. The healthy cartilage of the remaining knee remains intact.
Advantages of unicompartmental knee arthroplasty
A large number of studies have shown that unicompartmental knee arthroplasty, with appropriate indications, has excellent results in the vast majority of eligible patients.
The advantages of unicompartmental knee arthroplasty over total knee arthroplasty include:
- Faster recovery period
- Mild (less) post-operative pain
- Less blood loss in the operating room
- In addition, due to the fact that bone, cartilage and ligaments in the healthy segment of the joint are maintained, many patients report that their knee joints feel more “normal” compared to a total knee arthroplasty.
Finally, in unicompartmental knee arthroplasty, patients exhibit a greater range of motion (flexion and extension).
Disadvantages of unicompartmental knee arthroplasty
The disadvantages of unicompartmental knee arthroplasty in relation to total knee arthroplasty include the less predictable results in pain relief and thus the possibility of a revision surgery to replace the other part of the joint is higher.
PROSPECTIVE PATIENTS FOR SURGERY / PATIENTS ELIGIBLE FOR SURGERY
The orthopedic surgeon has to suggest surgical treatment in case of advanced osteoarthritis and after he has exhausted all conservative – non-surgical – means of treatment. Surgical treatment should be recommended to the patient if the condition significantly affects their quality of life and impedes the performance of daily activities. In particular, for unicompartmental arthroplasty, arthritic lesions should be confined to a single knee compartment. Patients with inflammatory arthritis, significant knee stiffness or ligament injuries are not ideal candidates. It is up to the surgeon to determine if the procedure is most appropriate for the patient. With the right patient selection, modern methods of unicompartmental knee arthroplasty have provided great medium and long-term results in younger and older patients.
In order to determine if the patient can benefit from the unicompartmental knee arthroplasty, the Orthopedic Surgeon must carefully evaluate the patient and discuss with him all possible treatment options.
Questions about pain characteristics are important. In this way, the exact point of sensitivity can be identified. If pain is exclusively or primarily located in one of the knee compartments (inner or outer), then the patient may be a candidate for unicompartmental knee arthroplasty. In cases where the pain is extended to the entire knee joint or its anterior part (below the patella), the orthopedist may recommend total knee arthroplasty.
The orthopedist should carefully examine the knee and search for localized tenderness, edema or erythema (redness) of the joint. In addition, the physician shall assess the range of motion of the joint and the integrity and quality of the connecting elements. If the knee is stiff or unstable, due to the failure of the joints or rupture, then unicompartmental knee arthroplasty is not indicated. On the contrary, the patient may meet the criteria for total knee arthroplasty.
Imaging involves simple radiographs of both knees in anterior and posterior shots. The examination is performed with the patient standing up to charge the knee joint with his/her weight. In special cases, MRI can better describe the condition of cartilage and soft tissues of the knee.
Usually, the patient is admitted to the hospital on the day of surgery. Before surgery, the anesthesiologist conducts a careful preoperative evaluation and discusses the options for anesthesia with the patient. These are issues that have already been discussed with the Orthopedist before surgery. Anesthesia can be either general (the patient is asleep) or epidural (the patient’s body is unconscious from the waist down).
Unicompartmental knee arthroplasty surgery usually lasts one to two hours. Initially, the surgeon makes an incision in the anterior part of the knee. He then examines all 3 compartments of the knee to ensure that the cartilage damage is located in only one compartment and that the connecting elements are fixed and intact. If the surgeon deems that the patient’s knee is not suitable for unicompartmental knee arthroplasty, then he proceeds to total knee arthroplasty. All this has already been discussed and determined prior to surgery with the patient, by obtaining his/her consent.
If the knee is considered suitable for unicompartmental arthroplasty, a special saw is used to remove the damaged cartilage from the bone. The bone is then covered with metallic prostheses, which are held in place by special cement. A polyethylene plastic is placed between the metallic surfaces to facilitate smooth sliding between them. After surgery, the patient is transferred to the recovery room, where he is closely monitored until he returns to his room.
As with any surgery, unicompartmental knee arthroplasty may be associated with some complications. The orthopedic surgeon should discuss all possible risks with the patient and take all necessary precautionary measures to avoid all these potential complications.
Although rare, the most common complications are:
- Vein thrombosis is the most common complication after unicompartmental knee arthroplasty. It occurs postoperatively in the deep veins of the lower extremities or pelvis. Anticoagulants, such as warfarin, low molecular weight heparin or aspirin may prevent the occurrence of this complication.
- All patients receive antibiotics (antibiotics) preoperatively and continue for another 24 hours postoperatively.
- Damage to nerves or vessels. Although rare, the nerves or vessels may be dilated during surgery.
- Continuous pain with no relief.
- Complications associated with anesthesia.
Since unicompartmental knee arthroplasty is performed with relatively small incisions and generally with a slightly invasive technique, hospital stay and recovery period are shorter.
Postoperative pain is milder, while the joint presents less swelling. In general, patients undergoing unicompartmental arthroplasty exhibit faster recovery than patients undergoing total knee arthroplasty. In most cases, patients return home one to three days after surgery. Charging of the leg begins immediately after surgery. A walking cane, crutches or a stroller may be required for the first few days or even weeks until the patient is comfortable enough to walk unassisted.
During the postoperative period, the surgeon, in collaboration with the physiotherapist, instructs the patient on appropriate exercises to maintain range of motion and restore muscle strength.
Typically, the patient returns to his pre-operative activities within 6 weeks postoperatively.