Hip & Knee Replacement
MINIMALLY INVASIVE SURGERY – TOTAL KNEE ARTHROPLASTY (MIS – TKA)
We have been performing minimally invasive surgery-total knee replacement for a number of years and have performed several hundred total knee replacement using a minimally invasive approach. This is an excellent approach that gives excellent results in the properly chosen patient. In our opinion, this approach should not be utilized if the surgeon feels that it could increase complications as compared with a standard approach (i.e. fracture of the bone, disruption of the extensor mechanism, poor visibility resulting in misplacement of components, etc.). There are several situations that we feel are relative contraindications for MIS – TKA. These include a very large leg (muscular or fatty), severe genu valgus (knock knee), patella baja (a short patellar tendon), significant posterior tibial osteophytes, significant osteopenia/osteoporosis, or low insertion of the VMO, etc.
There are several different MIS-TKA approaches. Each approach has advantages/disadvantages and proponents/opponents. We use a sub vastus MIS-TKA approach. We recommend to patients that they choose an orthopedic surgeon that they are comfortable with, have confidence in, and who has significant experience in TKA procedures. We then encourage that the patient should let that surgeon perform the procedure in the manner that he/she is most comfortable with.
MINIMALLY INVASIVE SURGERY – TOTAL HIP ARTHROPLASTY
We have been performing minimally invasive surgical approach total hip arthroplasty for a number of years and have done greater than 1000 total hip arthroplasties through a minimally invasive surgical approach. This is a safe and reproducible procedure that can give excellent results with a low complication rate, reduce discomfort, and decrease time for recovery in the majority of patients. There are many different MIS-THA approaches. Each approach has its advantages and disadvantages and its proponents and opponents. We use a MIS posterior approach. Our recommendation to patients is to choose an orthopedic surgeon that they are comfortable with and have confidence in, and who has significant experience in total hip arthroplasty procedures. Then let him/her perform the operation in the manner that he/she is most comfortable with.
The major reason for long-term therapy of total hip arthroplasty has been biological loosening of the implants secondary to accumulation of poly debris and the body’s response to the debris. When Sir John Charnley began doing total hip arthroplasties in the late 1960s, he used a metal head and Teflon liner for the bearing surfaces. The Teflon wore at a 1-2 mm a year and the implants only lasted 1-2 years. Charnley then substituted high-density polyethylene for the Teflon surface. This resulted in a tenfold decrease (0.1-0.2 mm a year) in wear and resulted in a tenfold increase (10-20 years) in the duration that the implants lasted. Approximately 10 years ago, highly crosslink high-density polyethylene was commercially introduced. The wear on this bearing is typically reported at 0.01-0.04 mm a year. Once again, a five to tenfold decrease in wear debris. The results to date with highly crosslink high-density polyethylene has been excellent; however, we do not yet know how long we can expect these implants to last. In addition, we do not know if new problems will develop for a THA that is in place for a longer period of time.
Other bearings have been introduced. These include metal-on-metal articulation. The wear on metal-on-metal bearing typically is in 0.005 to 0.01 range. However, this produces metal debris (cobalt and chromium particles). To date, we know of no studies directly linking increase levels of cobalt and chromium iron secondary to metal-on-metal articulating surfaces in total hip arthroplasty to cancer. We do know that they level of cobalt and chromium in the blood and urine of patients with metal-on-metal articulations in total hip arthroplasty do show a five to tenfold increase. Therefore, we do not recommend a metal-on-metal articulation to patients with renal disease, liver disease, diabetes mellitus, or women who plan to have another child (these metal ions do cross the placental barrier). Ceramic-on-ceramic bearings have excellent wear characteristics with wear rates reported as approximately 0.001. However, there have been many incidences of ceramic fracture, disarticulation of the ceramic articular liner, and squeaking of the implants.
Which bearing is best for a patient is dependent on many variable including the patient’s age, weight, activity level, and overall general health. The bearing surface that is chosen for any particular patient is a decision that should be made between the patient and the operating surgeon.
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