Partial Knee Replacement Overview
Partial knee replacement is performed for advanced knee arthritis that affects primarily the inner half of the knee. The damaged half of the knee is resurfaced, leaving the outer half and back of the kneecap intact. In appropriate patients it can be an alternative to total knee replacement and has some associated advantages. It benefits from a smaller incision, quicker recovery, greater range of motion and a more “normal” feeling knee. Patients usually go home the same or following day and will typically need a walking aid for a week or two. They can usually resume most activities within the first month or two. A partial knee replacement is expected to last as long as a total knee replacement.
Partial Knee Replacement Details
Knee osteoarthritis can be a debilitating condition causing pain, stiffness, and decreased mobility. Non-operative treatment includes maintaining fitness and a normal weight, bracing, medication, injections, and sometimes a walking aid. If these are ineffective knee replacement surgery may be considered, and total knee replacement has traditionally been the procedure of choice. In some cases however, when arthritis affects the inner half of the knee only and spares the remainder of the joint, partial knee replacement may be an option.
As successful as total knee replacement is, partial knee replacement has a number of advantages. It is a less invasive operation, performed through a smaller incision, and preserves bone, cartilage, and ligaments that are not affected by the arthritis. It also carries a lower risk of infection and other complications. Patients can often go home the same or next day of the operation, usually recover their mobility more quickly, and achieve greater range of motion and a more normal gait than with a total replacement. A partial knee replacement is expected to last as long as a total knee replacement.
In Brandon we use a particular type of partial knee replacement, called the Oxford partial knee. This implant has uniquely designed metal components and a durable plastic mobile bearing that give it additional advantages. These include fewer residual symptoms, less wear of the components over time, and the longest proven track record of any partial knee replacement. It also has the highest percentage of excellent results of any knee replacement. It is the only mobile bearing partial knee available in North America, and has been in use worldwide for over 40 years. Studies show that it should be the only knee surgery the patient will need in over 90% of cases. We have had considerable success with the Oxford knee in Brandon since 2001, and are happy to offer it and its advantages to appropriate patients.
To determine whether a patient is suitable for an Oxford partial knee replacement, additional specific knee X-rays are taken and information from possible previous arthroscopic surgery is gathered. The operation requires bone on bone medial (inner half) arthritis with relatively intact cartilage in the rest of the knee. It also depends on intact ligaments and well maintained range of motion. Not all patients are therefore candidates for this procedure, in which case a total knee replacement is usually recommended. It is possible to perform partial knee replacements for both knees under the same anaesthetic in appropriate patients.
The wait time for partial knee replacement may be shorter than for a total knee. It is important that the patient attend the Prehab Clinic at the Brandon Regional Health Centre, which is scheduled to ensure all medical issues are dealt with, lab work is in order, necessary home supports are in place, a cooling cuff is arranged, and preoperative exercises are initiated. This will help optimize outcome and patient satisfaction.
The procedure takes place on the day of admission under spinal anaesthesia, and lasts less than an hour. Postoperative pain is controlled with local freezing, a cooling cuff, and medication. Following surgery X-rays are taken and full weight bearing commences immediately. Patients can usually go home the same or sometimes the following day, once they are comfortable and mobilizing well.
Many patients are suitable for same day, or outpatient knee replacement surgery. Most of these are partial knee replacement surgeries, although some total knee replacement surgeries can qualify. Patients often prefer to have their immediate post-op recovery in the familiarity and quiet of their own home, where they can follow their own daily schedule, eat their own food, and enjoy the comforts they are accustomed to. This can also reduce the exposure to hospital acquired infections, and usually reduces the wait time to surgery, as an inpatient bed is not required.
We have had considerable success accommodating outpatient knee replacement surgery with newer modalities of pain and bleeding control, reduced needs for narcotic medication which can cause nausea and vomiting, and accelerated mobilization protocols. This is a safe and well established option that many have taken advantage of. Next day outpatient follow-ups, 24 hour phone access for nursing advice, and outpatient physiotherapy are arranged, and it is extremely rare for patients to need readmission to hospital.
Careful selection of patients suitable for outpatient knee replacement is critical, and appropriate home supports, certain medical conditions, advanced age, risk of falling, and specific patient requirements are factors in making this decision. All patients selected for outpatient knee replacement surgery will receive the necessary information and support to facilitate this.
Walking aids are used for the first week or two. Blood thinners are prescribed to reduce the risk of blood clots. Followups with the surgeon and physiotherapist are arranged.
Any operation has potential complications, but these are rare.They can include anaesthetic complications, prolonged stiffness, infection, blood clots in the legs or lungs, implant failure, bearing dislocation, or bone fracture. In less than 10% of cases future revision surgery is required, especially if initially performed in younger patients, but even these revisions typically do as well as a traditional primary total knee replacement.
Each patient recovers at their own rate, but the procedure usually allows more rapid recovery than a total knee. Patients can usually drive after 2 weeks, garden after 3 to 4 weeks, and golf after 6 to 8 weeks. It is expected that the patient will be able to resume the activity level they enjoyed before being limited by the knee arthritis, assuming there are not additional health or mobility issues. The implant is designed for activities such as brisk walking, and patients can conceivably return to recreational involvement in golf, tennis, cycling, swimming, skating and cross-country skiing, for example. Running, jumping and other impact activities are discouraged.
Improvements in comfort and function can continue for up to a year following surgery. There may be some residual symptoms, and the knee can remain warm for a number of months. The implant is designed to achieve about 130 to 140 degrees of flexion, but may be less in some patients, especially if they have considerable stiffness before surgery. Kneeling is allowed, but some patients find this uncomfortable. There may be some numbness around the incision or clicking noises in the knee, but this is normal. Patients are typically followed up for 6 to 12 months after surgery.