Plastics in Total Knee Replacement: Processing to Performance PMC

Management usually requires revision to a constrained condylar design or a hinge. It is our practice to put in a polyethylene insert during the index total knee replacement that would allow downsizing in subsequent operations. Our institutional algorithm for the use of IPE for arthrofibrosis can be seen in Figure 3. The implant’s cost is not standardized and therefore varies significantly among different hospitals, geographic regions, and manufacturers. Given these constraints, it is not easy to pinpoint the exact cost difference between HXLPE and CPE. Data from one hospital suggests that HXLPE inserts cost approximately 150 USD more than CPE, while others estimate this difference to be even higher [43].

The role of isolated polyethylene exchange in total knee arthroplasty

After verbal consent, patients were asked to answer questions regarding pain, feelings of knee instability, and subsequent revision surgery. Of 1606 revision TKA patients, 4% underwent an isolated PE for prosthetic knee instability. All cases were classified using the novel OrthoCarolina Prosthetic Knee Instability Classification System. This classification system was how to buy polymath established to guide surgeons in the diagnosis and surgical management of periprosthetic knee instability. While most companies have adopted newer technology, some still market CPE (non-cross linked) due to the concerns that cross-linking leads to inferior mechanical properties. Thermal treatment of irradiated HXLPE further compromises the mechanical properties.

When Polyethylene Exchange Is Appropriate for Prosthetic Knee Instability

In an in vitro study, VitE poly demonstrated decreased bacterial adherence (Staphylococcus epidermis and S. aureus) [21,22]. Overall, preclinical studies have shown promising improvements in fatigue strength when doped with VitE while maintaining the wear properties and oxidation resistance comparable to irradiated and remelted HXLPE [23]. 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]. Further, lower rates of bone resorption and inflammatory fibrous tissue were noted with VitE poly than HXLPE [25,26]. In literature, fracture of VitE poly has been reported in THR but not in TKR [27]. However, there are no midterm or long-term studies available on the use of VitE poly in TKR.

Component removal

Therefore, the key to avoiding prosthetic knee instability is through prevention at the time of primary surgery. A successful stable knee requires proper alignment, a complete concave release of the coronal https://www.tokenexus.com/ deformity, and equalization of the flexion-extension gaps. Failure to meet each of these basic technical criteria for knee arthroplasty puts the patient at risk for a difficult problem to treat.

At this time, there is no consensus in the United States regarding the acceptable shelf life. Whereas in Europe, a standard practice of five years of shelf life has been adopted [9]. Given that sterilization by EtO or GP does not produce any free radicals, the longer shelf life of more than five years may be justifiable. An irradiated plastic either by gamma or E-beam necessitates gas barrier packaging methods to prevent oxidation, while gas permeable packaging is acceptable for EtO and GP sterilization techniques [10]. A type 3 instability pattern is global in nature; that is, ligamentous instability is present both in full extension and at 90° of flexion.

• Existing short and midterm studies demonstrate no differences in revision rates between XLPE and CPE in TKA [32,34].
• Destruction of the plastic liner with saws or osteotomes trough sagittal cuts should be considered if specific instruments are missing.
• After the minimally invasive era in knee arthroplasty, patellar eversion has become unpopular and inconvenient in primary and especially in rTKA.
• IPE should be undertaken with caution and an institutional algorithm should be followed based on current literature.
• This method, however, had resulted in the production of innumerable free radicals that typically react with oxygen causing PE chain scission and significant oxidative wear.
• In this heterogeneous situation, surgeons should adopt an algorithm to approach these cases and avoid failures.

Posterior augments, preferentially on the lateral side, can be used to correct the internal rotation. At this point a ‘fine-tuning’ between flexion and extension gaps is carried out, changing the thickness of the polyethylene liner and the thickness of the distal femoral augments. Porous metal augments can be fixed with screws to the bone of the epiphyseal zone to increase resistance to the rotational force. Rarely, the surgeon may resect additional distal femur to stabilize the knee in extension if a fixed flexion contracture is present. ‘Mephistophelian’ is trying to restore the joint line with a millimetre accuracy at the anatomic joint line height.

Polyethylene Exchange Only for Prosthetic Knee Instability