What is Total Knee Arthroplasty?
Total Knee Arthroplasty is a popular surgical method used to replace damaged and degenerated knee surfaces. Replacing these surfaces with an implant or “prosthesis” will relieve the patient’s pain. It increases the range of motion of the joint and thus the patient is allowed to return to their daily activities.
The standard and more widely used approach is based on a large vertical incision of the skin at the center of the knee. On the contrary, a minimally invasive total knee arthroplasty (M.I.S.) uses a smaller incision in the skin and a less invasive technique. The goal is to reduce post-operative pain and the patient’s recovery time.
However, unlike the traditional method, the minimally invasive technique is not suitable for all patients. The treating physician must adequately present and explain all possible surgical options.
In Total Knee Arthroplasty, the degenerated surfaces of cartilage and bone, along with some soft tissues are removed. The goal of the procedure is to provide the patient with a relatively painless knee that will allow him/her to return to daily activities for as long as possible.
The minimally invasive Total Knee Arthroplasty (M.I.S.) differs. The difference is that it uses an incision that is less than half the classic one.
Classic Total Knee Arthroplasty
Initially, the surgeon makes a vertical incision 15-20 cm in the anterior and central area of the knee revealing the joint. The next steps are:
Bone Preparation: Degenerated (damaged) cartilage and bone surfaces at the lower femur and upper tibia are removed.
Metallic prosthesis placement: The removed cartilage and bone are replaced with metallic prostheses that mimic the surface of the joint.
Patella replacement: The damaged articular surface of the knee is removed and replaced with a plastic insert (polyethylene). Many times this step is omitted by the surgeon as appropriate.
Spacer Insertion: Between the femoral and the tibial metallic prostheses a very durable plastic insert (polyethylene) is also placed. This creates a smooth sliding surface.
Minimally Invasive Total Knee Arthroplasty (M.I.S)
In Minimally Invasive Total Knee Arthroplasty, although surgery is based on the same principles, the incision and excision of soft tissues are smaller. The artificial prostheses used are the same as those of the classic Total Knee Arthroplasty. However, the surgical tools, which are used to prepare the femur and tibia, are specifically designed, so that the prostheses are properly fitted.
As mentioned above, the operation uses a smaller incision about 10 cm. A smaller incision leads to less detachments and injuries to the patient’s soft tissues.
Beyond the minor incision, the technique used to reveal the joint is less invasive. In general, the techniques used are “quadriceps sparing”. This means that they avoid injury to the quadriceps tendon and other muscles of the anterior femoral surfaces. In the minimally invasive knee arthroplasty other approaches or techniques may also be used.
Small incisions made in the vastus medialis muscle (“midvastus” and “subvastus” approaches) expose the joint in a less invasive way. All of the aforementioned variations used in the non-invasive technique are designed to minimize knee injury and disruption. This results in less post-operative pain and reduces recovery time for the patient.
Hospital stay after surgery is similar to classic knee arthroplasty surgery and lasts from one to four days. Postoperative rehabilitation is crucial for optimal outcome. The surgeon and the physiotherapist assist the patient with a specific exercise program. The goal is to regain the strength and range of motion of the joint in a short period of time.
Candidates for Minimally Invasive Total Knee Arthroplasty
The Minimally Invasive Total Knee Arthroplasty is not suitable for all patients. The orthopedic surgeon performs a thorough preoperative evaluation to examine the various factors that will determine whether the procedure is appropriate for the patient or not.
In general, the candidates for the minimally invasive procedure are younger and thinner patients without concomitant health problems, willing to actively participate in the rehabilitation process. On the contrary, the minimally invasive procedure is contraindicated for overweight patients who have already undergone other knee surgery.
In addition, in patients who have significant knee deformity and muscular body structure or other concomitant health problems, the minimally invasive procedure increases the risk of complications.
The Minimally Invasive Total Knee Arthroplasty (M.I.S.) is a constantly evolving new technique. However, further research on the long-term survival of the results is required.
The benefits of the minimally invasive procedure include fewer detachments and fewer intraoperative soft-tissue injuries. Recovery is thus faster and more painless. Current experience has proven that the long-term benefits of the minimally invasive procedure are no different from those of the classic knee arthroplasty.