When Polyethylene Exchange Is Appropriate for Prosthetic Knee Instability PMC

This study is a descriptive, cross section of a series of revision knee patients. After approval from an Institutional Review Board, two centers queried patient registries and practice management how to buy polymath systems and identified 1606 patients who underwent revision TKA between 2004 and 2015. Of the 1606 revision TKA patients, 71 (4%) underwent an isolated PE for prosthetic knee instability.

When Polyethylene Exchange Is Appropriate for Prosthetic Knee Instability : JAAOS Global Research & Reviews

Implant-specific instrumentations have to be used in systems with a screw or interlocking parts. Destruction of the plastic liner with saws or osteotomes trough sagittal cuts should be considered if specific instruments are missing. Removal of the space-occupying insert reduces the tension in the patellar and femoro-tibial structures, increasing the level of exposure. A reciprocating sawblade is used to undermine the femur from the medial and lateral side. It is advanced below the component’s surface as much as possible until the pegs or the box area is reached. Posterior chamfer and posterior condyle are undermined with osteotomes to avoid damage to the surrounding soft tissues.

• However, early failures with fractures and oxidation damage have been reported with this design affecting mainly the posteromedial and lateral borders [17].
• The use of a porous metal cones or sleeves revision system is mandatory in the presence of central defects in this area.
• However, such radiation doses generate more free radicals that promote long-term oxidative degradation of PE.
• Of 1606 revision TKA patients, 4% underwent an isolated PE for prosthetic knee instability.
• VitE-coated blocks are placed into an inert oven and homogenized (baked) at 120°C until the vitamin diffuses through the block’s thickness.
• In literature, fracture of VitE poly has been reported in THR but not in TKR [27].
• A few unsuccessful attempts are carbon-fiber-reinforced poly (CFR-UHMWPE) marketed as Poly II (Zimmer) and Hylamer (Depuy).

IPE for wear and osteolysis

Since there has been no consensus to determine the best plastic production process in the orthopedic industry, the implant companies have sought their own strategies for processing UHMWPE. This article focuses on 1) processing of PE, 2) packaging and sterilization techniques, 3) mechanical and wear properties of the final product, and 4) product options available from different implant manufacturers. After the minimally invasive era in knee arthroplasty, patellar eversion has become unpopular and inconvenient in primary and especially in rTKA. Consequently the usefulness of a snip in non-everted patella has become very negligible. Regardless, we have learned that this procedure is infrequently used at two tertiary referral centers to manage prosthetic knee instability. Isolated PE was only used in 2.5% of more than 1600 revision knee cases over a 10-year period.

IPE for peri-prosthetic joint infection

There are several ways to process PE and manipulate their mechanical properties, wear characteristics, and oxidative resistance. An ideal PE’s properties include strong resistance to wear, oxidation, and FCP and should retain these properties in-vivo https://www.tokenexus.com/ for the long-term. Wear resistance is improved by crosslinking the PE, which is accomplished by higher doses of radiation (Gamma or E-beam). However, such radiation doses generate more free radicals that promote long-term oxidative degradation of PE.

The role of isolated polyethylene exchange in total knee arthroplasty

This type of instability is caused by unrecognized incompetence or iatrogenic injury at the time of primary surgery. On rare occasions, this type of instability pattern can be caused by a traumatic event. Management of this type of instability pattern usually requires conversion to a constrained condylar femoral implant and polyethylene. The reinforced post in this construct provides varus-valgus stability to compensate for the incompetent collateral ligaments.

Notably, the wear particles from irradiated HXLPE are smaller and biologically more active than from non-irradiated ones. However, periprosthetic osteolysis is not commonly observed because of an overall reduction in the quantity of wear production in HXPLE compared to CPE [34,39]. Please note that both the paper and electronic transcripts are considered official, but you should confirm that your intended transcript recipient accepts electronic transcripts. Some recipients may only accept transcripts that are sent directly to their offices. In this case, you would NOT want your transcript sent to yourself first to forward on to the intended recipient.

When Polyethylene Exchange Is Appropriate for Prosthetic Knee Instability

Successful management can be obtained without major component removal if an anterior constrained polyethylene implant is available. If this is not available, conversion to a posterior cruciate substituting femoral implant and polyethylene must be used. Prosthetic knee instability is a common cause of patient dissatisfaction and early failure after total knee arthroplasty (TKA).1,2 Technical considerations account for most of these problems. The symptoms of prosthetic knee instability include catching, giving way, anterior knee pain, pes bursitis, and the inability to trust the knee in daily activities. Some instability patterns require full revision, whereas others can be managed by polyethylene exchange (PE) only. Despite the use of this technique when indicated, the results of PE only with regard to pain and instability are unpredictable.

• In vitro studies showed that VitE poly has five times greater ultimate strength after four weeks of accelerated aging test and up to an 86% lower wear rate than CPE [24].
• Successful management can be obtained without major component removal if an anterior constrained polyethylene implant is available.
• More commonly, one can increase the extension gap through further distal femoral resection.
• Therefore, these less than optimal results may be related to the inappropriate use of this treatment alternative rather than the treatment alternative itself.

Polyethylene Exchange Only for Prosthetic Knee Instability

• Prosthetic knee instability is a common cause of patient dissatisfaction and early failure after total knee arthroplasty (TKA).1,2 Technical considerations account for most of these problems.
• This is caused by reluctance to either remove more distal femoral bone or strip the posterior capsule off the posterior femur at the time of primary surgery.
• Instead of thermal treatment, incorporating antioxidants or sequential irradiation constitutes a balanced environment to create oxidation- and fatigue-resistant PE while maintaining its wear characteristics.
• Strategies to manage such instability are dependent on the recognition of the presenting instability pattern because some require full revision, whereas others can be managed by polyethylene exchange (PE) only.
• The Poly II was introduced in 1970 but was discontinued due to the rupture of the surface fibers and reduced crack resistance than the virgin UHMWPE [35].