High Flex Knee and Minimal Invasive Surgery
Abstract
During the past three decades total knee arthroplasty has evolved to a well-defined technical procedure with excellent long-term results.1–3 It is the overall accepted standard that the primary goals of total knee arthroplasty are correct ligament balancing, proper joint alignment according to the mechanical axis and stable anchorage of the implant.
The concept of exposure is, in principle, similar with medial, parapatellar or oblique incision of the skin. The length of skin incision and the total exposure of the joint are mainly very extensive including joint dislocation, eversion of the patella, disturbance of the quadriceps mechanism, dislocation of the tibia femoral capsule and often extensive soft tissue disruptions. In recent years, therefore, both patients and surgeons have expressed a wish for improving this type of surgery.
In addition to the standards of total knee arthroplasty, major goals for minimal invasive surgery are:
- no lesion of the extensor mechanism (the tendon of the quadriceps has to remain undamaged);
- early mobilisation with the possibility of reducing hospital stay and costs; and
- small skin incisions resulting in a better cosmetic outcome.4–8
The range of motion after total knee arthroplasty is important for functional outcome and the satisfaction of the patient. New total knee systems were introduced to enhance post-operative flexion of the implant. This additional flexion–up to 150 degrees–allows activities such as sitting on the floor and squatting. For patients demanding high flexion in their daily lives, these new implants can improve the quality of life.
Minimal Invasive Techniques
For soft tissue exposure, three different medial approaches are recommended: mini-medial arthrotomy (also known as quad-sparing procedure), mini mid-vastus approach and mini sub-vastus approach. The mini-medial arthrotomy causes only very limited exposure of the quadriceps tendon and permits only a lateral subluxation of the patella without eversion. As access to the joint is limited with this incision it can only be used for smaller sized implants. If there is a need for a more extensive exposure of the joint, one can switch to the mid-vastus approach by splitting the vastus medialis obliquus approximately 2cm. Another option would be the sub-vastus approach, which provides excellent exposure while preserving all four attachments of the quadriceps to the patella. This approach does not require eversion of the patella, minimises the disruption of the suprapatellar pouch and allows easy closure of the knee joint.
