Minimally Invasive Knee Surgery – Total Knee Replacement Surgery
Minimally Invasive Surgery (MIS) for Total Knee Replacement
Total Knee Replacement - Advanced arthritis of the knee symptoms (pain, stiffness, limited motion, decreased walking and standing tolerance) often times intensify to the point of interfering with daily activities and causing intolerable pain during some or all activities. For these people, surgical intervention using joint replacement implants often times returns patients back into their normal life style with markedly diminished or no knee pain.
Alternatives to total knee replacement includes self directed treatments such as weight loss, daily aerobic low impact exercise, and OTC pills such as ibuprofen, naproxen, or acetaminophen. Physician directed treatments include physical therapy, prescription anti inflammatory NSAID like Celebrex, Cortisone injections, Visco gel injections, arthritis unloader bracing, acupuncture, and if indicated for meniscal tear or loose body - knee arthroscopy.
Total Knee replacement is done when 2 or 3 of the knee compartments are worn out and accompanied by advanced deformity (varus- bow leg or valgus- knock knee) and/or limited knee motion.
Partial or Unicompartmental Knee replacement is done robotically using the Makoplasty technique when only one compartment is worn.
MIS – CAS Surgery Becoming Less Prevalent
At this writing (10/2011) the application of minimally invasive techniques for total knee replacement is decreasing. Medical reports proving substantial benefit with this technique are few. In some patients minimally invasive surgery with computer navigation leads to less pain and quicker return to normal activities. As time has passed it has become apparent that these benefits occur in some but not all of the patients that under go this procedure. Surprisingly, many traditional knee replacement patients are also recovering with less pain and faster return to normal function due to multimodal pain management, improved traditional surgical techniques and rapid rehabilitation protocols. Back in the early 2000's when MIS - CAS TKA came into being the expectations were that outcomes using these techniques would revolutionize Total Knee Replacement. Better surgical outcomes and functions due solely to these new techniques have not materialized. In certain patients with specific physical characteristics without markedly advanced arthritis MIS - CAS TKA will result in better early (1-2 month) recoveries. By 3 months post op there is not any improvement in knee replacement results due to MIS techniques. Medical studies published over the last several years fail to find any advantage for MIS - CAS techniques.
Research has not been convincing on MIS – CAS TKA resulting in better long-term function or better durability of minimally invasive knee replacements.
Advocates of minimally invasive knee replacement can show less surgical pain and faster recovery to early milestones that occur in the first 6 weeks. Computer Navigation advocates can show more accurate implant position due to precise bone cuts. However, bone cut accuracy is only one component of successful Total Knee Replacement surgery. Soft tissue balancing, correct patellar tracking, correct implant sizing and correct component rotation are also vital elements of successful knee replacement and are independent of computer navigation or MIS technique. Surgeons, including myself, postulated in the early 2000's that by combining the small incision with computer-guided instruments we could dramatically improve outcomes. However, the expected benefits have yet to be established. Again, over the past 5 years there are no convincing studies to support an advantage to performing MIS-CAS total knee replacement over traditional TKA.
What I see in my day-to-day practice is that hospital length of stay and return to work and recreational activities are similar in both MIS - CAS and traditional Total Knee patients. These good outcomes are not technique dependent.
I will continue to evolve surgical techniques and incorporate new technologies into the practice of orthopedic surgery. I will continue to perform MIS - CAS TKA in patients that meet specific physical and disease criteria that make the this technique safe, reproducible and relatively easy to perform with expectations of shorter hospital stay, less pain and faster return to activities. Factors that make MIS - CAS TKR possible are good soft tissue mobility (flexibility of knee tissue), good preoperative range of motion, mild knee deformity (bowed or knocked knee), and body mass index less than 35. Factors that increase the difficulty and select against using MIS - CAS technique are large quadriceps muscle, poor soft tissue mobility (stiffness of knee tissue), poor preoperative knee motion, large knee deformity, short patellar tendon, multiple previous knee surgeries and BMI greater than 35.
What is MIS surgery?
The deep incision is made from the patellar tendon insertion on the tibia (tubercle) to the upper pole of the knee cap. See green line on cartoon— however the green line is artificially short here— it should go farther down the lower leg away from the numbers just as far as the black line. No incision is made in the quadriceps tendon (the large muscle on the front of the thigh). However, a few of the muscle fibers of the VMO muscle are split to allow the knee cap to move laterally — extension #2 in the cartoon (so called mini mid vastus). The procedure is done through as small of skin incision as is possible (depending on individual patient factors) causing less traumas to the soft tissues. Dr. Tarlow first performed MIS Total Knee Replacement with Computer Navigation in August of 2004.
What is Traditional TKR?
In traditional total knee replacement the incision in the deep tissue (below the skin) continues 2-3 inches up the thigh toward the groin as compared to the MIS incision. See the black line in the cartoon — usually does not go as far up the thigh as is drawn here. This splits the Quad tendon and allows the knee cap to evert for easy access to the knee joint. Traditional Knee Replacement is now being done through a much shorter skin incision compared to a decade ago.
Patients often ask, "Am I a candidate for MIS (Minimally Invasive Surgery) Total Knee Replacement"? The experienced MIS surgeon can answer this question after evaluation/examine in the office. In some cases the decision is made in the operating room. Factors that make MIS TKR simpler are good soft tissue mobility (flexibility of knee tissue), good preoperative range of motion, mild knee deformity (bowed or knocked knee), and body mass index less than 35. Factors that increase the difficulty are increased muscle tissue, poor soft tissue mobility (stiffness of knee tissue), poor preoperative knee motion, large knee deformity, short patellar tendon, multiple previous knee surgeries and BMI greater than 35.
Computer-Assisted Surgery is one approach to reduce surgical errors and reliable reproduce bone cuts associated with knee and hip surgery. Computer Navigation utilizes an operating room based computer and transducers pinned to the thigh and shin bones. The patient's unique anatomy is mapped and displayed on the computer screen. This real time anatomic data is used to plan and verify bone cuts for precise implant placement. These computer based tools increase the repeatability and accuracy of surgical procedures. Studies have yet to show improvements in outcomes of total knee replacement done using Computer Navigation. Dr. Tarlow has been using computer assisted surgery since 2003.
The Current State of Affairs in Total Knee Replacement Surgery
Dr. Tarlow was an early adopter and proponent of Minimally Invasive Surgery (MIS) combined with the accuracy of Computer Navigation (CAS). Based on his 8 years of experience with this technique and his observations of his own patients he has revised his opinions related to Total Knee replacement techniques.
Only a minority of patients are suitable surgical candidates for the smaller incision technique. Only a minority of patients will experience the desired benefits of less pain and faster recovery. Outcome studies have yet to show improvement in MIS - CAS techniques. Insurance companies do not pay for or reimburse for fees associated with this technique. In some patients there is an early benefit to the MIS/CAS procedure including a quicker recovery over the first 6-8 weeks.
Traditional Knee Replacement, the time tested procedure, is used for most cases. All current information from experts in the field of knee replacement agree that long term outcomes are similar for both MIS/CAS and Traditional Knee Replacement. Traditional Knee replacement surgery uses standard instrumentation and does not require the use of computer navigation. Improvements over the last decade in traditional surgery techniques, multimodal pain management and rapid rehabilitation protocols have resulted in recovery after Traditional TKR similar or identical to MIS - CAS Total Knee replacement techniques.
Typical Recovery: Hospitalization 1-3 nights. Walker for 5-10 days. Driving within 2-4 weeks. Return to work in 1-3 months. Results vary depending on individual's physical condition, other constitutional characteristics. Some MIS/CAS patients do reach recovery milestones sooner during the first 8 week period. Recovery merges onto a similar course after 3 months. Many patients take a year to a completely healed state.
Typical Risks include infections, blood clots and knee stiffness. Antibiotics are used in the peri operative period to lower infection risk. Blood thinners and early mobilization are used to lower risk of blood clots. Aggressive, early Physical Therapy for 6-8 weeks is used to maximize range of motion and function.
Which procedure would be better for you, the individual patient ? To answer the question a full evaluation by your local orthopedic surgeon is required.
Total Knee Implants
Implants for MIS and Traditional Knee replacement are identical. Doctor Tarlow uses the Smith and Nephew Legion, the Zimmer Gender High Flex and Zimmer NexGen Knee components. He will be introducing the Aesculap Columbus Knee, a German company with an international presence. These implants are engineered for superior range of motion in knee flexion and rotation, while offering conforming fit on both the male and female knee.
The Zimmer Gender High Flex knee is designed specifically for a woman's knee. Zimmer has incorporated 3 specific design characteristics to closely match the shape and proportion of a woman's knee. These design features include smaller shape and modified proportions, a more angled knee cap groove, and a narrower and thinner anterior femoral flange.
Zimmer Nexgen High Flex knee incorporates advanced design to improve knee function, such as climbing stairs with minimal difficulty or pain and high-flexion activities like golf, working in your garden, and those activities that require bending deeply at the knee can be addressed.
The Smith and Nephew Legion is from the Genesis 2 family of proven performance implants. By virtue of the unique implant design features and materials the Legion Total Knee System is ideally suited to address the common patient factors including age, motion, anatomy, gender, pathology and metal sensitivity. The Legion Narrows are specifically designed for the female anatomy. This knee is available in an Oxinium (ceramic) femoral component. Recently introduced is the so called "30 Year Knee" with Verilast Technology.
The Aesculap Columbus Knee system offers surgeons intra-operative solutions for all total knee indications. There is High Resection Accuracy for Optimum Fixation and High Mediolateral Stability of the Femoro-Patellar and Femoro-Tibial Joints. The number and combination of sizes help ensure every patient is matched with the most optimal implant component sizing possible regardless of race, gender or stature.
Dr. Tarlow is not a paid consultant of any orthopedic device manufacturer or pharmaceutical corporation and does not receive payments for use of any orthopedic implants or pharmaceutical products.
Custom Cutting Block Knee Replacement
Cutting block for Custom PMI
Total Knee Replacement in
place on distal femur.
This method provides the surgeon with patient specific anatomic data to direct bone cuts for accurate positioning of standard total knee components. It is available commercially under the trade names Otis Med, Patient Matched Instrumentation and Signature. The technique utilizes preoperative Knee MRI to produce a Custom computer generated virtual knee model unique for each patient from which custom cutting blocks are fabricated in advance of the procedure and hold the "code" for implant sizing and bone cut placement for accurate implant alignment and rotation. This method can be considered an evolving technology and may or may not be the method of choice in the future. There are cost considerations with this technique (MRI and cost of cutting block fabrication — approx. $1000 per set at this time). Dr. Tarlow will consider use of this method on patient request.
Cost of Total Knee Replacement
The CPT billing code for TKR is 27447, for unicompartmental knee replacement 27446 and for patellofemoral arthroplasty 27438. These codes are useful to patients when discussing cost with insurance companies or surgeons. Surgeon fee varies between physicians but is typically several thousand dollars (Dr. Tarlow fees). Charges typically associated with TKR include surgeon fee for total knee (27447), surgeon fee for Computer Navigation (20985), surgical assistant fee (12-20 % of surgeon payment — not fee), anesthesiologist fee, hospital fee and physical therapy fee. If you would like to know more or have specific questions about medical costs, email me.
Guidelines for Antibiotics after total knee replacement
For routine dental prophylaxis, one dose Amoxicillin 2 grams orally one hour prior to dental work is standard.
Use Clindamyacin 600 mg if PCN allergic.
In 2009 this recommendation was extended from use only in the first 2 years after joint replacement to a lifetime recommendation.
Last Modified: November 9, 2011