TotalKneeWeb.com – Article Index

A

Knee Replacement Allergies – Nothing to Sneeze At?

Arthritis, Osteoarthritis and Osteoporosis….What’s the Difference anyway?

B

What’s the “Best” Total Knee Replacement?

C

Knee Replacement Clicking

Patellar Clunk Syndrome: Complication Following Knee Replacement Surgery

F

Female Knee Replacement

G

General

Interesting Items from Around the Web October 11th 2010

Knee Replacement – Items from around the web – January 8th 2011

K

Knee Replacement-General

L

How Are the Ligaments Affected in Total Knee Replacement?

To Retain or Sacrifice the PCL (Posterior Cruciate Ligament)…That is the Question

M

Manipulation

Minimally Invasive (MIS)

Mobile Bearing

O

Osteoarthritis

Osteoporosis

P

Press-Fit Knee Replacement

Patellar Clunk Syndrome: Complication Following Knee Replacement Surgery

V

Video Showing a Traditional Total Knee Replacement Surgery?

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Knee Replacement – Items from around the web – January 8th 2011

“Prehabilitation” and Knee Replacement.

In a recent article available at  LowerExtremityReview.com the concept of  “Prehabilitation” or exercise before Total Knee Replacement Surgery was reviewed.  It has been demonstrated that one of the predictors of post operative range of motion (ROM) is pre-operative ROM.  It stands to reason that exercises aimed at increasing pre-op ROM and knee function could positively impact post-op recovery and motion.  This article discusses this topic in detail and also includes a free-download for a recommended Pre-Op “Prehabilitation” regimen.

Click Here for the original article.

American Joint Replacement Registry becoming a reality

In countries like Sweden and Great Britain, hip and knee replacement procedures and outcomes are tracked in a national database or “registry.”  Such data is often useful in spotting trends and helping to reduce revision rates. Today, a similar set of data does not exist in the US, however a recent article in “Orthopedics Today”1 states that this is about to change. Beginning soon, data from 15 U.S.  “pilot” hospitals will begin to be collected and funneled into the registry.   Initially, things like the “mechanics” of the data collection and ensuring patient confidentially will be worked out.  An overview of the goals and anticipated impact of the registry can be found here

http://orthodoc.aaos.org/ajrr/AJRR%20Fact%20Sheet_AJRR.pdf at www.ajrr.net

1 “First Phase of U.S. Joint Replacement Registry Data Collection Set to Begin, Orthopedics Today, Nov 2010 online at: http://www.orthosupersite.com/view.aspx?rid=77205 ?

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TotalKneeWeb.Com – Interesting Items from Around the Web

Interesting Items from Around the Web October 11th 2010

Arthritis on the Rise

In a weekly report from the CDC, it was estimated that arthritis results in cost of $128 billion each year in the United States alone.  The prevalence of arthritis and associated costs is expected to increase dramatically given the aging population.  Data from the period of 2007-2009 was analyzed.   It was found that 22.2% of adults 18 and over reported arthritis, with 9.4% reporting a reduction in activity level due to arthritis.


For more information visit:   http://www.cdc.gov/mmwr/

Broccoli…Good for Your Aching Joints?

Researchers have found that a coumpound found in brocolli could help block the enzymes that cause the damage to joints in those with osteoarthritis …

Read More At: http://www.thenews.com.pk/latest-news/1506.htm

Knee Replacement in Less than a Minute..

Check out this quick 3D animation of a knee replacement:

http://mmhc.com/2010/06/09/3d-medical-animation-of-a-knee-replacement/.

Then visit our Surgery Overview page for a more detailed description.

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To Retain or Sacrifice the PCL…That is the Question

In the normal knee, the ligaments provide stability during movement of the joint. There are four major ligaments in the knee: the medial and lateral collateral ligaments (MCL and LCL), which provide “side to side” stability and the anterior and posterior cruciate ligaments (ACL and PCL) which provide “front to back” stability.

In total knee replacement surgery, the ACL is routinely removed, the MCL and LCL are preserved, but the PCL is either retained or sacrificed. This brings up the obvious question-is it better to retain or sacrifice the PCL in total knee replacement?

There are many reasons why the posterior cruciate ligament may be removed or retained. Both scenarios have been associated with certain advantages and disadvantages.1 In either case, the implants used have specific geometry to account for the presence or absence of the ligament.

Retaining the PCL is believed to aid in proprioception (the ability to sense where parts of the body are in relation to each other) and could make activities like climbing stairs feel more “stable” or “natural”. Also, when the ligament is maintained, it can promote more normal front to back knee motion, possible aiding in deep flexion.

The implant used in these cases (referred to as “cruciate retaining or ‘CR’) is specially designed to allow for the presence of the PCL. However, in order for the PCL to perform it’s intended function, it must be in relatively good, “healthy” condition. Also, it must be properly “balanced” after the have been oriented and implanted by the surgeon. This can sometimes be challenging and can result in less predictable results from patient to patient.

Also, just as the surgeon must balance the PCL if retained, the MCL and LCL must be properly balanced as well. This can be more difficult with the PCL intact. One can imagine that the tibia (shine bone) is like a swing rotating underneath the femur (thigh bone). The MCL and LCL are analogous to the chains or ropes holding the swing. The PCL is like a third chain coming down in the middle. It is easy to appreciate given this model, why the PCL makes creating the proper tension in the MCL and LCL more difficult since the tension in the PCL itself affects the tension in the other structures.

When the PCL is sacrificed, special geometry in the implant components substitutes for the function of the ligament. That is why these “PS” implants are sometimes referred to as PCL Substituting. When the surgeon removes the PCL, the joint space (the space between the prepared femur and tibia) becomes larger, making exposure easier. Also, the MCL and LCL tension can be more easily assessed.

Finally, since the ligament (whose function can be variable from patient to patient), is now replaced by very consistent implant geometry, results tend to be more repeatable (repeatable meaning less variation, not necessarily better overall).

So given all of this, how does long-term performance of these different types of implants and surgical approaches compare? In a recent study by Kolisek et. al., a group of patients receiving a CR implant was compared to a group with the posterior cruciate ligament removed.2 Two surgeons each did about half of the knee replacements in each group. Here is a summary of how the groups compared:

So as can be seen, and as the surgeons concluded, the study did not demonstrate a distinct advantage for one version over the other. Simply stated, PCL retention versus sacrifice is often a matter of surgeon preference and depends upon the “existing pathology of the posterior cruciate ligament” at the time of surgery. In short, the answer to the question on whether it is better to retain or sacrifice the PCL cannot be answered definitively.

References

1 Wheeles Textbook of Orthopaedics. “TKR – Posterior Cruciate Ligament Retaining Prosthesis.” http://www.wheelessonline.com/ortho/tkr_posterior_cruciate_ligament_retaining_prosthesis. Mar 2009

2. Kolisek FR, McGrath MS, Marker D, Jessup N, Seyler TM, Mont MA, Barnes CL. “Posterior-Stabilized vs. Posterior Cruciate Ligament-Retaining Total Knee Arthroplasty” The Iowa Orthopaedic Journal. Vol. 29. p 23-27.

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The Impact of “High-Risk” Sports in Knee Replacement Patients

At the recent meeting of the American Academy of Orthopaedic Surgeons, a study was presented where survivorship of total knee replacements in patients who participated in certain “high-risk” sports was compared to those who did not participate in such activities.1

In this study, a group of 1500 patients that received the identical prosthesis were asked if they participated in certain high-risk activities. These are activities which place excessive load on the implant such as basketball, soccer or football. Within this group, 218 were identified as having participated in such “high-risk” sports. These patients were then “matched” against a control group so other factors such as BMI, age and sex could be eliminated.

What the researchers discovered was somewhat contrary to conventional wisdom. At roughly 7.5 years after surgery, the high-risk group had slightly superior function and slightly lower rates of failure (loosening, wear of the implant etc) compared to the control group. As stated in the study, “At a mean follow-up time of 7.5 years after modern condylar TKA in 218 patients no significant differences in implant durability could be demonstrated between those involved in not-recommended sports activities compared to matched controls.” Only time will tell if differences in implant longevity over longer periods will become apparent, so further study is warranted. Nonetheless, as increasingly younger and more active patients elect to have total knee replacement surgery, the limits on total knee replacement design and longevity will be tested and questioned.

References
1 Parratte S, Lynn Dahm DL, Stuart MJ, Pagnano MW, Berry DJ, Does Participation in Not-recommended Sports Impact Total Knee Arthroplasty Durability, AAOS Annual Meeting Podium Presentation, 2010

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Press-Fit Total Knee Replacement: Working to Prevent Loosening and Bone Loss

In , the worn ends of the bones that make up the joint are replaced with metal and plastic implants. These implants are secured to the bone either with “bone cement” which the surgeon applies to the implant and bony surfaces or they are simply “press-fit” into place. In the press-fit scenario, the surface of the implant which contacts the bone is typically coated with a porous structure. This structure is designed to mimic the porous or sponge-like structure of the prepared bone in order to promote bony in-growth into the implant coating.

In addition to utilizing a bone-like porous structure for press-fit implant coatings, it is desirable that the “flexibility” or “elasticity” of the implant material also approach that of bone. This is because bone, which is a dynamic living tissue, actually responds and adjusts to the stresses placed upon it. If an implant is too stiff relative to the bone, then over time, the bone will become less and less dense, literally disappearing under the implant due to what the body perceives as lack of use (the old “use it or loose it” adage). This is known as “stress-shielding.” The resulting bone loss may eventually result in loosening of the implant.

It is possible that such bone loss and resulting implant failure can be avoided by using materials and coatings which better approximate the properties of real bone. This is because as the implant material properties approach that of normal bone, loads are better transferred through the implant to the bone, thus allowing the bone to perceive more normal use and encourage the continued maintenance of bone under the implant.

In a recent article in the Journal of Bone and Joint Surgery (American) Minoda et. al1. looked at how bone in the tibia (shin bone) responded to a particular type of press-fit implant. The implant utilized a tantalum porous coating. The property of the bone that was measured to gage how it responded to the implant was bone mineral density (BMD). In the study, a group of implanted knees (28) receiving the press-fit implant was followed and compared over a period of two years, two a group of knees (28) with a cemented implant. BMD scans taken were taken at various intervals.

The researchers found that BMD decreased in the tibia in both groups. However, in the press-fit (porous tantalum) group, the decrease was only 6.7% +/- 22.9% vs. 36.8% +/- 24.2% in the cemented group. So it appears that this particular porous coated implant may have been able to allow more natural loading of the tibia, thereby reducing bone loss compared to the cemented implant. Only time will tell if these apparent benefits continue long-term.

References:
1. Yukihide M, Kobayashi A, Iwaki H, Ikebuchi M,I nori F, Takaoka K. Comparison of Bone Mineral Density Between Porous Tantalum and Cemented Tibial Total Knee Arthroplasty Components. Journal of Bone and Joint Surgery (American). 2010;92:700-706

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Introductory Topics

Below are Introductory Topics for those who are interested in learning more about Total Knee Replacement:

Introduction

Total Knee Replacement FAQ’s (Frequently Asked Questions)

Normal Knee Anatomy

The Diseased Knee: Osteoarthritis

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Wait…So Running Isn’t Bad for My Knees?

In another “counterintuitive conclusion” researchers from some recently published studies are not finding a clear correlation between running and bad knees.  In fact, runners may actually be at lower risk for developing compared to non-runners.  Go figure.  Then go running….

Read more About This Story Here

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Weight Gain After Knee Replacement?

A recent study out of the University at Delaware found that patients actually gained weight following knee replacement surgery. Conventional wisdom was that after suffering years of debilitating pain, formerly sedentary arthritis sufferers would resume activity and exercise following their knee replacement. However, researchers found that patients actually gained an average of 14 pounds after a two year follow up period…

Follow this link for more information on this topic

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Knee Replacement Complications

(also known as total knee arthroplasty) is generally a highly successful procedure with excellent long-term results. In a recent study, 97% of patients remained “revision-free” at 10 years 1. Despite these favorable outcomes, complications may still occur. Listed below are some of the more common complications of total knee replacement surgery.

Infection

Several steps are taken to prevent infection. For example, antibiotics are often given before, during and after knee replacement surgery. Still, a small percentage of knee replacements become infected. In a recent study of over 3000 replacements, 2.9% experienced “superficial” infections while 0.8% of infections occurred within the joint. An increased rate of infection was observed in patients who experienced complex surgery or who had certain characteristics such as obesity or poor pre-operative health. 2

Loosening

Knee replacement components are affixed to the bone in two ways. In “press-fit” implants, long term fixation relies on the growth of bone into what is typically a porous surface or coating on the underside of the implant. Alternatively, the implants may be “cemented” into place with a strong polymer (PMMA) which is mixed and applied at the time of surgery. Both of these fixation methods can fail over time for a variety of reasons causing the implant to become loose and requiring revision (see Implant Poly Wear)

DVT

Deep Vein Thrombosis (DVT) is a rare but potentially very serious complication. Blood clots (thrombus) can sometimes form in the “deep” veins near the surgical site. This can cause pain, redness and swelling. Sometimes, the clot can become dislodged and travel through the bloodstream and into the lungs where it can become trapped. This is called a pulmonary embolism and can be fatal. Obviously, many, many precautions are taken to prevent this serious complication.

Patellar Clunk Syndrome

This complication involves interaction of the scar tissue at the top of the patella with the femoral component. See our article on Patellar Clunk Syndrome for more information.

Joint stiffness

Obviously, the joint will be soar and relatively stiff immediately after surgery, however, limited flexion after the immediate post-operative period is undesirable. To read more on stiffness following knee replacement surgery, visit our article joint stiffness following knee replacement surgery.

Allergic Reaction

A small number of patients may experience an allergic reaction or hypersensitivity to the metallic elements in the implants. A more detailed explanation of this complication can be found our article on this topic.

1 Barrington JW, SahA, Malchau H, Burke DW. Contemporary cruciate-retaining total knee arthroplasty with a pegged tibial baseplate. Results at a minimum of ten years. JBJS (Am.). 2009;91:874-878.

2. Jämsen E, Varonen M, Huhtala H, Lehto MU, Lumio J, Konttinen YT, Moilanen T. Incidence of Prosthetic Joint Infections After Primary Knee Arthroplasty.  J Arthroplasty.2008 Dec 3.

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