What is a unicompartmental knee arthroplasty?
A unicompartmental knee arthroplasty (UKA) is a surgical procedure used to relieve disease in one of the knee compartments. In UKA, only the damaged parts of the knee are replaced. The UKA surgery may reduce postoperative pain and have a shorter recovery period than a total knee replacement procedure, especially in the elderly population.
Knee arthroplasty is also called a knee replacement surgery. The surgery involves removing the damaged parts of the knee joint and replacing them with parts constructed with metal, ceramic, and very hard plastic.
This artificial joint is also called a prosthesis or an implant. It reduces pain and improves the function of the knee joint. Knee arthroplasty is indicated when the knee joint is damaged. Arthritis is the most common cause of knee joint damage and, hence, one of the most common indications for knee arthroplasty.
The three compartments of the knee joint
The ends of the bones, where the bones in the knee joint move against each other the most, are most likely to suffer damage. These areas are known as compartments, and they are as follows:
- The medial or inside compartment
- The lateral or outside compartment
- The patellofemoral or behind-the-kneecap compartment
There are various surgical approaches to the surgery, including minimally invasive techniques. The choice of technique depends on the surgeon’s decision.
When is a unicompartmental knee arthroplasty done?
To undergo a unicompartmental knee arthroplasty (UKA), the damage to the joint should be confined to only one compartment. UKA may be indicated in the following conditions if it is limited to a single compartment:
- Osteoarthritis
- Osteonecrosis (tissue death)
- Malalignment
- Mild deformities
When is a unicompartmental knee arthroplasty not done?
Contraindications for a unicompartmental knee arthroplasty (UKA) include the following:
- Inflammation of the joint
- Previous surgery with overcorrection
- Septic arthritis (joint infection) and sepsis (systemic infection)
- Ligament tears leading to joint instabilities
- Tibial (shin bone) or femoral (thigh bone) shaft deformity
- Major joint deformities
- Damage in more than one compartment
How is a unicompartmental knee arthroplasty performed?
Prior to the surgery, the surgeon performs a complete physical assessment, X-ray and magnetic resonance imaging (MRI) of the joint.
The surgery is performed using general anesthesia. The concept behind a unicompartmental knee arthroplasty (UKA) is the replacement of only the damaged part of the knee and the preservation of as much normal tissue and bone as possible to allow the restoration of normal kinematics.
A conventional incision is usually around 12 inches in length, whereas the incision in UKA is around 7 cm. The damaged part of the joint is replaced with a prosthetic. The surgery can also be performed arthroscopically (minimally invasive). A small incision of around 3-4 inches in length is made over the area of the knee joint through which an arthroscope (a camera with a light source) and surgical instruments are inserted. The surgical wound is closed with sutures (stitches) and dressed.
SLIDESHOW
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After the surgery, painkillers and antibiotics are administered. Patients are usually discharged between one and three days after the surgery. Patients are encouraged to walk with support the same or next day to prevent the formation of blood clots.
Physical therapy may begin at the hospital, and the patient would be advised to continue the exercises at home. Pain, swelling, and bruising due to the surgery are reduced in two weeks. Most patients can resume their routine activities in less than 6-12 weeks.
Recovery and joint strength continue to improve. Complete recovery after the surgery may take around six months, after which patients can resume high impact exercises and sports.
What are the complications of a unicompartmental knee arthroplasty done?
Some complications encountered are as follows:
- Osteolysis (inflammation destroying the bone and causing the prosthesis to loosen)
- Infection
- Bleeding
- Formation of blood clots
- Bone necrosis (bone death)
- Different leg lengths leading to altered gait/limp
- Migration or failure of the prosthesis
- Dislocation or fracture of the joint
- Fractures around the joint
- Residual disease in the other compartments
- Reaction to anesthesia
Medscape Medical Reference
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