Knee Arthroplasty

Total knee arthroplasty refers to the replacement of the worn-out surfaces of the knee joint and the correction of its deformity with implants that are fully biocompatible with the human body.

A successful outcome of total knee arthroplasty depends on the following factors:

• Proper patient selection: Indications for total knee arthroplasty include patients with severe and persistent pain, significant functional impairment of the joint, and radiographic evidence of advanced arthritis. The most common causes are rheumatoid arthritis and osteoarthritis, although post-traumatic arthritis and other conditions may also require surgery. The ideal candidate is an elderly, thin patient with limited mobility, no severe comorbidities, and one who has exhausted conservative treatment options. Absolute contraindications include failure of the extensor mechanism of the knee, active infection, neuropathic arthropathy, and ankylosed knee. Relative contraindications include a history of osteomyelitis, peripheral vascular disease, and medical conditions making anesthesia unsafe.
• Access: The incision is made either midline or parapatellar. The joint is opened via a medial parapatellar arthrotomy with proximal extension along the quadriceps fibers when needed.

• Axis correction: Preoperative varus or valgus deformity must be corrected, as persistent malalignment will lead to rapid loosening of the implant. This is achieved by cutting the tibia perpendicular to its longitudinal axis and the distal femur with a few degrees of valgus so that the mechanical axis passes through the intercondylar eminence of the tibia. Stability and good function require balanced tension of the collateral ligaments throughout the range of motion. This is achieved by creating equal flexion and extension gaps. If imbalance remains, soft tissue release is performed on the tighter side.

• Component orientation: In the coronal plane, implants should be aligned so that the mechanical axis passes through the intercondylar eminence. In the sagittal plane, the tibial component should be placed with a posterior slope of 3–7 degrees. The femoral component should not be placed in hyperextension, as this may cause a supracondylar fracture. Excessive internal or external rotation of the femoral or tibial component must be avoided to prevent extensor mechanism dysfunction. The joint line should be maintained close to the preoperative level.
• Patellar tracking: Intraoperatively, the patella must glide smoothly within the trochlear groove of the femoral component. If not, lateral retinacular release may be required.