Surgical Techniques - Total Knee Replacement
You need help for the knee pain from arthritis that has gotten so bad you can no longer function well or tolerate the pain with even simple daily activities. The evaluation of your knee by physical exam and X-ray review; and the failure to respond to more conservative measures has left you wondering about your next step. What can be done now? …..
The answer may well be a total knee replacement or a unicompartmental knee done with the most advanced minimally invasive surgical techniques and rapid rehabilitation program available anywhere in the world. As a recognized leader, teacher and innovator in minimally invasive surgical techniques for total knee arthroplasty surgery, Dr. Robert Zehr of the Zehr Center for Orthopaedics has had the opportunity to refine the various aspects of the surgical experience for his patients both in the operating room and in the care postoperatively. He is constantly seeking ways to improve patient outcomes, whether it is better methods to educate a patient, pain management techniques or new highly technical advancements in his surgical technique or choice of implants!
Knee Replacements Are in Demand
You should know that knee replacement surgery is really quite common. In fact, last year it is estimated that over 700,000 Americans underwent this highly successful operation to relieve the pain of an arthritic knee joint. Even more impressive is that number is expected to jump to nearly 3.4 million knee replacements annually within the next 20 years . This will be driven by the combination of a dramatic increase in aging Americans and an ever more demanding younger population who are unwilling to live with debilitating knee pain.
Although it has been commonly and mistakenly thought that knee replacement is only for the older, Medicare aged population; it may surprise many people to know that ~50% of all total knee replacements are being done in patients under the age of 65 years . Returning a working age member of society back to a productive and contributing level has made total knee replacement surgery one of the most highly valued surgical procedures of the past several decades.
In fact a recent study by Ruiz, et al.  assessing the direct and indirect costs of lost work and wages, disability payments and lower earnings; the lifetime cost savings to society for the 600,000 total knees done in the US in 2009 is over $12 billion…..that’s just for patients done in one year!
With this astounding estimate of patient need for total knee replacement surgery and its recognized value to society, it becomes increasingly vital that each knee replacement implant survive for as long as possible; hopefully for the remainder of the patient's life. It has been generally accepted that of the knees done 20 years ago, over 90% of them are still functioning today. With an improvement in materials and techniques, it is expected that the survival rate will continue to improve.
Can Knee Replacements Last Forever?
Unfortunately, even with a 90% survival rate at 20 years, there is still going to be a large number of implants that fail for some reason each year. Given the expected increase in demand noted above, the sheer volume of knee replacements being done will result in a significant number that will need to be revised or completely redone.
Currently, ~9% of knee replacement surgeries done each year are performed for revision of previously done surgery (see http://www.zehrcenter.com/practice/revision-total-knee ). The number of revisions is expected to show a six-fold increase over the next 25 years . Over the past 3 decades surgeons have discovered several important causes that lead to persistent pain or early failure of knee implants.
Two of the most critical causes of failure have been malalignment of the components and poor balance of the knee ligaments. It is estimated that nearly half of all knee revisions could be prevented with correct ligament balancing . If the various parts of the knee replacement cannot be aligned and rotated to follow the patient’s natural movement dictated by the knee’s ligamentous structure and / or the knee’s ligaments cannot be balanced to allow equal pressure to be generated in all compartments of the knee….. quite simply, it will not feel right to the patient; and it will have a higher chance of early failure than in those knee replacements where these elements can be optimized!
Soft tissues, composed of tendons, ligaments and muscles, exert forces on the joint, enabling its movement. Proper balance of the soft tissues is critical for a joint implant to function correctly. If soft tissues are too tight, the joint cannot regain its full range of motion; if too loose, the joint may become unstable; if loaded excessively on one area, and implant will fail prematurely. The importance of obtaining soft-tissue and ligament balance and appropriate bony alignment of the knee are high priorities for all knee replacement specialists each and every time the procedure is performed.
Unfortunately with current instrumentation, even the most experienced surgeon can find this balancing process quite challenging at times. Until recently, determining the degree of joint balance intraoperatively has been the subjective assessment and skill of each surgeon, making critical soft tissue kinematic adjustments more of an art than an exact science. There has been no method with which to quantify the relative feel of the patient's joint when performing soft tissue releases….. UNTIL NOW!
Computer Assisted / Intelligent Orthopaedic Surgery
Fortunately, there is new and exciting technology that can help the surgeon in the operating room while he is making judgments on the alignment and balance of your knee. What is now being referred to as “Intelligent Orthopaedics” is a new field that harnesses the latest innovations in sensors, accelerometers, microelectronics and wireless communications with the goal of improving healthcare outcomes and reducing the costs of treating musculoskeletal disease.
OrthoSensorTM, the leader in “intelligent orthopedics”, has a computer integrated knee system, VerasenseTM, which is used to ensure proper soft tissue balance and limb alignment during total knee arthroplasty. This intelligent instrument replaces the standard plastic tibial tray spacer the surgeon uses to position an implant during total knee arthroplasty. It is used to quantify load and contact position of the femur on the tibia before final implants are selected and implanted permanently.
These highly sophisticated components contain micro sensors, accelerometers, microelectronics and communications technologies that provide surgeon with actionable data to make real time adjustments. The temporarily implanted device quantifies and wirelessly transmits key, real-time information to a graphic display, enabling surgeons to visualize and quantify joint balance, alignment and load throughout a full range of motion. Connected to a computer via wireless link, the sensors provide a quantitative assessment of intercompartmental loads, center of load and kinetic tracking during the trialing of the knee implants. With this evidence, surgeons can make informed adjustments to optimize implant placement and enhance both clinical outcomes and patient's satisfaction.
Watch how the Verasense Tibial Implant
provides real time data to surgeon
The “Intelligent Orthopaedic” sensor, VerasenseTM, is relatively new to surgeons having first been released for use in 2009 by the surgeon developers. Since that time this high technology device has shown great promise and more surgeons are finding this style of ligament balancing more precise and reproducible than with more standard instrumentation. Early study results have shown knee function scores (used to measure before and after results) improved markedly. Not only did postoperative patient activity levels exceed that of preoperative levels, but patients became more active in a shorter amount of time following surgery then in traditional total knee arthroplasty without sensors . In addition, a more recent study of the VerasenseTM implant reveals that patients with balanced knees are 2.5 times more likely to achieve significant improvement in Knee Society Scores between pre- and post- operative intervals than are patients with unbalanced knees .
Stryker Triathlon® Total Knee Replacement
The “Get Around Knee™”
Knee Implants That Promote Easier Motion
Knee Implants Designed to Last Longer
Better Results in Knee Replacement
Let's take a look at how Stryker's Triathlon Knee with X3 technology compares to other knee implants when measuring revision rates in the National Joint Registry of England and Wales.
Men’s Knees vs. Women’s Knees--- Reality vs. Hype
When investigating knee replacement surgery a patient must be careful what they read and a word of caution is in order. There are many fine knee implants available to you and your surgeon. Typically your surgeon will choose an implant based on his extensive experience, scientific evidence and past patient outcomes. If there was one design of knee that worked far better in a woman or a man, most certainly all surgeons would use that implant. As it is, no such "Excalibur" implant exists but, there are many implants by several reputable manufacturers that will work very well for you.
Unfortunately, there continues to be heavy marketing by one manufacturer that there is a "Woman's Knee" or a "Gender Specific Knee" that works better for woman. This marketing implies that all of the other knee implants are really men's knees that are being forced to fit a woman's unique anatomy. What you should know is that in this country more than 60% of knee replacements are done in women and to that extent it makes sense for a manufacturer of implants to focus on this part of the market.
The truth is that a woman's knee anatomy IS slightly different from a man's knee, but with the current implant designs virtually every manufacturer makes its implants in multiple sizes. Results supported by the majority of scientific studies indicate that the "unisex" approach of implants works equally well in women as they do in men. It would be worth your time to review one of the award winning studies among many which investigate the misleading claims of superiority of the "gender-specific knee". This study emphatically concludes that... "the data refute the hypothesis of inferior clinical outcome for women following total knee arthroplasty when using standard components"(http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2565048/ ).
The fact remains that knee replacement surgery is not perfected as yet and the outcome studies indicate a small yet reproducible number of dissatisfied patients --both men and woman--with their outcome. It does not seem to make any difference which implants are used. Surgeons, manufacturers and therapists are all working hard to improve these outcomes even further, but for now total knee replacement surgery remains one of the best options for a patient whose knee has deteriorated to the point they can no longer do the things they enjoy. Fortunately, the vast majority of patients who undergo knee replacement each year --some 700,000-- are extremely pleased with their results and are able to get back the lives that were in slow gear because of their arthritic knee.
Pain Control after Knee Replacement Surgery
Quad-Sparing/Minimally Invasive Approach for Total Knee Replacement
Demonstration Videos & X-rays
Animation of Stryker Triathlon Total Knee Replacement
Watch Dr. Zehr Perform Minimally Invasive Total Knee Replacement Surgery
Below are pre-op and post-op X-rays of an arthritic knee which underwent a total knee replacement and is doing very well.
- Kurtz S, et al., Projections of primary and revision hip and knee arthroplasty in the United States from 2005 to 2030. J Bone Joint Surg. 2007; 89:780-5.
- Kurtz S, et al., Future Young Patient Demand for Primary and Revision Joint Replacement: National Projections from 2010 to 2030. Clin Orthop Relat Res 2009; 467(10): 2606-12.
- Ruiz D, et al. The Direct and Indirect Costs to Society of Treatment for End-Stage Knee Osteoarthritis. J Bone Joint Surg. 2013; 95: 1473-80.
- Sheng PY, et al. Revision Total Knee arthroplasty: 1990 through 2002. A review of the Finnish arthroplasty registry. J Bone Joint Surg. Am. 2006; 88:1425-30.
- deGroot IB, et al. Small increase of actual physical activity 6 months after total hip and knee arthroplasty. Clin Orthop Relat Res. 2008; 466:2201-2208.
- Gustke K, et al. New Method for Defining Balance: Promising Short-Term Clinical Outcomes of Sensor-Guided TKA. J Arthroplasty 2014; 29(5): 955-960.
- Jacobs CA, et al. Factors Influencing Patient Satisfaction Two to Five Years After Primary Total Knee Arthroplasty. J Arthroplasty 2014; 29(6): 1189-1191.
- Ostermeier, S; Stukenborg-Colsman, C, Hannover Medical School (MHH) Hannover, Germany "Quadriceps force after TKA – a comparison between single and multiple radius designs", Poster No. 2060 • 56th Annual Meeting of the Orthopaedic Research Society.
- Harwin, S.F., Hitt, K, Greene, K.A. Early Experience with a New Total Knee Implant: Maximizing Range of Motion and Function with Gender-Specific Sizing Orthopedic Surgery, Surgical Technology International, XVI. pgs 1-7.
- Greene, K.A. Range of Motion: Early Results from the Triathlon® Knee System, Stryker Literature Ref # LSA56., 2005.
- Wang, H., Simpson, K.J., Ferrary M.S., Chamnongkich, S., Kinsey, T, Mahoney, O.M., Biomechanical Differences Exhibited During Sit-To-Stand Between Total Knee Arthroplasty Designs of Varying Radii, JOA, Vol. 21, No. 8, 2006.
- Stryker Orthopaedics Test Report: RD-06-013.
- The National Joint Registry of England and Wales. Annual Report 2010. Table 3.11 Based on mean Revision Rates at three years according to brands for knee replacement procedures undertaken between 1st April 2003 and 31st December 2009, which were linked to a HES/PEDW episode.
- The effect of total knee arthroplasty design on extensor mechanism function, JOA, Vol. 17, Issue 4, June 2002, pp. 416-421.
- US Patent #7,714,036