With Knee Replacement Rehabilitation, the Sooner the Better New Study Shows.

In a recent study 1 published in the journal Clinical Rehabilitation, a group of Spanish researchers looked to determine if there was any benefit to beginning exercises within the first 24 hours following Knee Replacement versus waiting an additional 1-2 days to begin therapy.

The researchers compared two groups, each consisting of 153 total knee replacement patients. All patients underwent knee replacement for the treatment of advanced osteoarthritis. Following their knee replacement, the experimental group began rehabilitation within 24 hours after surgery. The other group (control) began their rehabilitation between 48 and 72 hours post-op.

When comparing the two groups, the researchers looked at several factors in order to gauge performance of each group. They looked at things such as range of motion, muscle strength and pain

What the scientists found was that the group of patients that stared their rehabilitation within 24 hours of their surgery performed significantly better. This group enjoyed a shorter hospital stay, fewer rehabilitation sessions while in the hospital and less pain. In addition the quicker rehab group also experienced greater range of motion (ROM) in flexion and extension, improved strength in the quads and hamstring muscles as well as better gait and balance. The table below summarizes the major results.

Measure	Result
Hospital Length of Stay	24 Hr. group in hospital 2.09 days less (on average) than 48-72 Hr. group
Rehab Sessions	24 Hr. group had 4.95 fewer rehab sessions (on average) before discharge that the 48-72 hr. group
ROM-Flexion	24 Hr. group could flex knee on average 16.29 degrees further than 48-72 hr. group
ROM-Extension	24 Hr. group could extend knee on average 2.12 degrees further than 48-72 hr. group

This interesting article is available online in full text format at the Clinical Rehabilitation Journal website.
1 Labraca NS, Castro-Sanchez AM, Mataran-Penarrocha GA, Arroyo-Morales M, del Mar Sanchez-Joy M, Moreno-Lorenzo C. Benefits of starting rehabilitation within 24 hours of primary total knee arthroplasty: randomized clinical trial. Clinical Rehabilitation, March 2011

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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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Follow up on Female Knee Replacement

In one of our first posts, we discussed what was at the time a new type of knee replacement implant specifically designed for female anatomy. These “gender specific” knee replacement implants have a shape tailored to fit the narrower distal femur or thigh bone in women. (see New Total Knee Replacements Specially Designed for Female Anatomy). In that original post it was stated that “It will be interesting to see how these new implants fair clinically and whether the potential advantages are realized.” Well, in a recent study published in the Journal of Bone and Joint Surgery1, these exact issues were investigated.

In the study, a group of female patients who received gender specific knee replacements were observed. Eighty five (85) women received a “gender specific” implant in one knee and a “standard” implant design in the other knee. The group was followed for two years. The results showed virtually no difference in outcome. Knee scores, range of motion and patient satisfaction were similar. Interestingly, the only significant difference noted between the two types of implants was that at the time of surgery, the surgeons observed a better implant fit for the standard implant group vs. the gender specific group. This is not what one would have assumed since the gender specific knee replacements are specifically designed to better-fit female anatomy. Although there are several different brands of gender specific knee replacements available and only one particular brand was studied, the results do suggest that the proposed advantages of gender specific or female knee replacement implants may be overstated. However, the authors acknowledge that the 2 year follow up period may not be indicative of more long term results.. Stay tuned as more information becomes available on this controversial topic in total knee replacement.

1 Young-Hoo Kim, Yoowang Choi, and Jun-Shik Kim. “Comparison of a Standard and a Gender-Specific Posterior Cruciate-Substituting High-Flexion Knee Prosthesis: A Prospective, Randomized, Short-Term Outcome Study”. JBJS, 2010; 92: 1911-1920

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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 knee replacement 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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Video Showing a Traditional Total Knee Replacement Surgery

So you are searching for a video showing a traditional total knee replacement surgery (also known as Total Knee Arthroplasty) ? You have found what you are looking for here. Below is a three part video education series narrated by Dr. Kirby Turnage of Pensacola, Florida and http://www.gcortho.com/.

These videos have everything you will need if you are considering total knee replacement surgery. The first video talks about preoperative issues, the second video shows an actual surgery being performed, and the last video talks about postoperative issues that all patients who undergo this operation should be aware of.

Total Knee Replacement Part 1: Preoperative Considerations

Total Knee Replacement Part 2: The Surgical Procedure

Total Knee Replacement Part 3: Postoperative Issues Following TKR

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Mobile Bearing Knee Replacement Offers no Benefits vs. Fixed Bearing

In a previous posting 1, the question was raised as to which is better, fixed or mobile bearing knee replacement. In the end, the answer was not very clear. But in the view of one implant manufacture, the choice is simple: fixed bearing.

In a recent press release, a major U.S. Orthopedic implant company (Stryker Corporation) has decided not to offer their mobile bearing knee replacement in the U.S. market. Although the company has executed a clinical trial in an effort to gain FDA approval for the device, data gathered during the study has demonstrated no clinical advantages for the mobile bearing knee compared to a comparable fixed bearing design.

The company also cited higher costs and higher revision rates for mobile bearings as further reasons why the mobile bearing design will not be pursued in the U.S. market.

The original press release can be found here:
http://www.prnewswire.com/news-releases/us-ide-study-indicates-mobile-bearing-knees-offer-no-clinical-advantages-over-fixed-bearing-knees-86866577.html

More on Stryker can be found here:
http://www.stryker.com/en-us/products/Orthopaedics/KneeReplacement/index.htm

1 Is One Really Better? Fixed vs. Mobile Bearing Knee replacement

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

In total knee replacement, 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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How Are the Ligaments Affected in Total Knee Replacement?

A common question regarding total knee replacement (also known as total knee arthroplasty) is what happens to the ligaments in the knee as a result of knee replacement?

First, it is helpful to understand the location and function of these important soft-tissue structures. There are four major ligaments in the knee joint. Two of these ligaments act as “side-to-side” stabilizers in the knee: the medial collateral ligament (MCL) and the lateral collateral ligament (LCL). These ligaments connect the femur (thigh-bone) to the tibia (shin-bone). They are located on the inside (medial) and outside (lateral) parts of the knee.

The other two ligaments, the anterior cruciate ligament and the posterior cruciate ligament (ACL and PCL) limit “front-to-back” or anterior-to-posterior movement of the knee. These ligaments are named based on their attachment site on the tibia and are found roughly in the middle of the joint. The PCL runs from the back or posterior part of the tibia to the front of the femur. The ACL runs in the opposite way. These ligament cross, hence the name “cruciate”.

So what happens to these ligaments as a result of total knee replacement? The collateral ligaments (LCL and MCL) are left intact as they are important for proper function and longevity of a total knee replacement since the function of these ligaments is, for the most part, not replaced by the prosthetic components.

The ACL is removed since the portions of the bone where it typically attaches are removed and replaced by the implant components. Often this structure is severely compromised in patients requiring total knee replacement.

What is done with the PCL is not as straightforward. Depending on the particular patient as well as surgeon preference, the PCL may either be retained or sacrificed. Implants specific to either scenario are available for the surgeon’s use.

For more on types of implants see our section on this topic.

So in summary, in a standard total knee replacement..

The collateral ligaments (LCL and MCL) are preserved
The ACL is removed
The PCL is either retained or sacrificed.