Dataset Information

Tibial post wear in posterior-stabilized knee replacements is design-dependent.

ABSTRACT: Polyethylene tibial post wear in posterior-stabilized knee designs is a major problem. The Insall-Burstein II (IB PS II) reportedly has severe anterior wear of the post in retrieved implants. We hypothesized the more anterior placement in the IB PS II would be reflected in greater wear at the anterior face than the IB PS I. We examined 234 retrieved inserts using subjective scales to grade post damage and wear. Of the IB PS II inserts, 38% demonstrated severe wear compared with only 25% of IB PS I inserts. The most prevalent damage location for the IB PS II was the anterior face, whereas the IB PS I sustained wear mainly on the medial face. While the IB PS post was not designed to constrain posterior femoral displacement, our observations confirm contact in hyperextension or other paradoxic anterior tibial translation is common and design-dependent. Minimizing wear and damage through proper post placement and changes in implant design to anticipate contact on the anterior post should be considered for future posterior stabilized knee replacements. These changes cannot occur in isolation, however, because changes in post placement and design also depend on their relation to the shape and location of the tibial bearing surfaces.

SUBMITTER: Furman BD

PROVIDER: S-EPMC2565057 | biostudies-other | 2008 Nov

REPOSITORIES: biostudies-other

ACCESS DATA

Similar Datasets

Project description:BackgroundPosterior stabilized total knee arthroplasty requires an intercondylar notch to accommodate the cam housing that articulates with the tibial post to create femoral rollback required for deep flexion. The volume of bone resected for the intercondylar notch varies with implant design, and newer designs may accommodate high flexion with less bone resection.Questions/purposesThis study aims to analyze the bone volume and density resected from the intercondylar notch for three posterior stabilized implants from a single company: a Posterior Stabilized (PS) system, a Hi-Flex system (HF), and a rounded new box-reamer (RB) system and to further assess whether the newer RB with a cylindrical cutting tool would preserve more native bone.Materials and methodsUsing a computer model, the PS, HF, and RB femoral components were digitally implanted into CT scans of 19 cadaver femurs. Nine cadavers were fit with a size 4 implant, six with size 3, and four with a size 2. The volume of intercondylar bone resected digitally for femoral preparation was measured. Bone density was measured by CT scans in Hounsfield units (HU). A paired t test was used to compare the mean volume of bone resected for each implant.ResultsFor the size 4 femurs, the newer RB design removed 8% less intercondylar bone than the PS design (7,832 ± 501 vs. 8,547 ± 377 mm(3), p < 0.001) and 28% less bone than the HF design (7,832 ± 501 vs. 10,897 ± 444 mm(3), p < 0.001). The average HU for size 4 femurs for RB design was 427 ± 72 (PS = 399 ± 69, p < 0.001; HF = 379 ± 66, p < 0.001). For the size 3 femurs, the RB design removed 12% less intercondylar bone than the PS (6,664 ± 786 vs. 7,516 ± 648 mm(3), p < 0.001) and 27% less bone than the HF (6,664 ± 786 vs. 9,078 ± 713 mm(3), p < 0.001). HU for size 3 femurs for the RB design was 452 ± 70 (PS = 422 ± 53, p < 0.1; HF = 410 ± 59, p < 0.01). For the size 2 femurs, the RB design removed 5% less intercondylar bone than the PS (5,730 ± 552 vs. 6,009 ± 472 mm(3), p < 0.01) and 22% less bone than the HF (5,730 ± 552 vs. 7,380 ± 532 mm(3), p < 0.001). HU for size 2 femurs for the RB design was 430 ± 48 (PS = 408 ± 55, p < 0.01; HF = 385 ± 56, p < 0.01).ConclusionsThe newer RB design removes less bone from the intercondylar notch than the classic PS and HF designs in all sizes tested. The bone-conserving cuts incorporated into this newer implant design appear to preserve native bone without compromising design objectives.

Project description:BackgroundThe controversy regarding the outcome of total knee arthroplasties after high tibial osteotomy may relate to malalignment secondary to overcorrection after high tibial osteotomy (HTO) [1, 2] and to the type of arthroplasty itself (posterior-stabilized arthroplasty or posterior cruciate ligament-retaining prosthesis).Questions/purposeWe asked two questions: (1) Would a posterior-stabilized arthroplasty provide sufficient constrain and improve pain and function in patients with severe malalignment due to a previous HTO? (2) Will malalignment of the previous HTO jeopardize the long-term results of a total knee reconstruction with a posterior-stabilized implant?Patients and methodsWe retrospectively reviewed 25 posterior-stabilized TKAs in 25 patients with severe valgus deformity after HTO (ranging from 10° to 20° of valgus) and compared the results with a series of matched 25 posterior-stabilized TKAs in 25 patients with normocorrection after HTO ranging from 5° of valgus to 5° of varus. Clinical, operative, and radiographic data were reviewed. Minimum follow-up was 10 years after the arthroplasty (average, 15 years; range, 10-20 years).ResultsAll the knees had standard posterior-stabilized total knee arthroplasty implants. Patients with an overcorrected HTO were more likely to require a soft tissue release to balance the knee. However, Average Knee Society and Function Score improved, respectively, from 48 to 85 and from 50 to 90 points in the severely overcorrected group, versus, respectively, 50 to 89 and 52 to 97 in the normocorrected group, but the range of mobility was superior for patients with normal alignment. Fifteen-year survivorship after the arthroplasty comparison showed no significant difference between the two groups (one revision in each group).ConclusionsPatients with an overcorrected HTO are more likely to require a soft tissue release to balance the knee. However, both groups show improvements in function and pain. With a posterior-stabilized arthroplasty, the degree of deformity has no impact on the longevity of the TKA.

Project description:More robust preclinical experimental wear simulation methods are required in order to simulate a wider range of activities, observed in different patient populations such as younger more active patients, as well as to fully meet and be capable of going well beyond the existing requirements of the relevant international standards. A new six-station electromechanically driven simulator (Simulation Solutions, UK) with five fully independently controlled axes of articulation for each station, capable of replicating deep knee bending as well as other adverse conditions, which can be operated in either force or displacement control with improved input kinematic following, has been developed to meet these requirements. This study investigated the wear of a fixed-bearing total knee replacement using this electromechanically driven fully independent knee simulator and compared it to previous data from a predominantly pneumatically controlled simulator in which each station was not fully independently controlled. In addition, the kinematic performance and the repeatability of the simulators have been investigated and compared to the international standard requirements. The wear rates from the electromechanical and pneumatic knee simulators were not significantly different, with wear rates of 2.6?±?0.9 and 2.7?±?0.9?mm3/million cycles (MC; mean?±?95% confidence interval, p?=?0.99) and 5.4?±?1.4 and 6.7?±?1.5?mm3/MC (mean?±?95?confidence interval, p?=?0.54) from the electromechanical and pneumatic simulators under intermediate levels (maximum 5?mm) and high levels (maximum 10?mm) of anterior-posterior displacements, respectively. However, the output kinematic profiles of the control system, which drive the motion of the simulator, followed the input kinematic profiles more closely on the electromechanical simulator than the pneumatic simulator. In addition, the electromechanical simulator was capable of following kinematic and loading input cycles within the tolerances of the international standard requirements (ISO 14243-3). The new-generation electromechanical knee simulator with fully independent control has the potential to be used for a much wider range of kinematic conditions, including high-flexion and other severe conditions, due to its improved capability and performance in comparison to the previously used pneumatic-controlled simulators.

Dataset Information

Tibial post wear in posterior-stabilized knee replacements is design-dependent.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets