This aim of this study was to assess the feasibility of designing and introducing generic 3D-printed instrumentation for routine use in total knee arthroplasty. Instruments were designed to take advantage of 3D-printing technology, particularly ensuring that all parts were pre-assembled, to theoretically reduce the time and skill required during surgery. Concerning functionality, ranges of resection angle and distance were restricted within a safe zone, while accommodating either mechanical or anatomical alignment goals. To identify the most suitable biocompatible materials, typical instrument shapes and mating parts, such as dovetails and screws, were designed and produced.Aims
Materials and Methods
Loosening of the tibial component after total knee arthroplasty (TKA) is a common indication for revision. Increasing the strength of the initial tibial implant/cement interface is desirable. There is little information about the surgical techniques that lead to the highest strength. We investigated the effects of eight variables on the strength of the initial tibial baseplate/cement interface. A total of 48 tibial trays were cemented into acrylic holders using cement from two manufacturers, at three different times (early, normal, and late) using two techniques: cementing the tibial plateau or the plateau and the keel; and involving two conditions of contamination with marrow fat (at the metal/cement and cement/cement interfaces). Push-out tests were performed with load continuously recorded.Aims
Materials and Methods
The aim of this study was to compare the maximum
laxity conferred by the cruciate-retaining (CR) and posterior-stabilised
(PS) Triathlon single-radius total knee arthroplasty (TKA) for anterior
drawer, varus–valgus opening and rotation in eight cadaver knees
through a defined arc of flexion (0º to 110º). The null hypothesis
was that the limits of laxity of CR- and PS-TKAs are not significantly
different. The investigation was undertaken in eight loaded cadaver knees
undergoing subjective stress testing using a measurement rig. Firstly
the native knee was tested prior to preparation for CR-TKA and subsequently
for PS-TKA implantation. Surgical navigation was used to track maximal
displacements/rotations at 0º, 30º, 60º, 90º and 110° of flexion.
Mixed-effects modelling was used to define the behaviour of the
TKAs. The laxity measured for the CR- and PS-TKAs revealed no statistically
significant differences over the studied flexion arc for the two
versions of TKA. Compared with the native knee both TKAs exhibited
slightly increased anterior drawer and decreased varus-valgus and
internal-external roational laxities. We believe further study is required
to define the clinical states for which the additional constraint
offered by a PS-TKA implant may be beneficial. Cite this article:
Although it is clear that opening-wedge high
tibial osteotomy (HTO) changes alignment in the coronal plane, which is
its objective, it is not clear how this procedure affects knee kinematics
throughout the range of joint movement and in other planes. Our research question was: how does opening-wedge HTO change
three-dimensional tibiofemoral and patellofemoral kinematics in
loaded flexion in patients with varus deformity?Three-dimensional
kinematics were assessed over 0° to 60° of loaded flexion using
an MRI method before and after opening-wedge HTO in a cohort of
13 men (14 knees). Results obtained from an iterative statistical
model found that at six and 12 months after operation, opening-wedge
HTO caused increased anterior translation of the tibia (mean 2.6
mm, p <
0.001), decreased proximal translation of the patella
(mean –2.2 mm, p <
0.001), decreased patellar spin (mean –1.4°,
p <
0.05), increased patellar tilt (mean 2.2°, p <
0.05) and
changed three other parameters. The mean Western Ontario and McMaster
Universities Arthritis Index improved significantly (p <
0.001)
from 49.6 (standard deviation ( The three-dimensional kinematic changes found may be important
in explaining inconsistency in clinical outcomes, and suggest that
measures in addition to coronal plane alignment should be considered. Cite this article:
The purpose of this study was to test the hypothesis that patella alta leads to a less favourable situation in terms of patellofemoral contact force, contact area and contact pressure than the normal patellar position, and thereby gives rise to anterior knee pain. A dynamic knee simulator system based on the Oxford rig and allowing six degrees of freedom was adapted in order to simulate and record the dynamic loads during a knee squat from 30° to 120° flexion under physiological conditions. Five different configurations were studied, with variable predetermined patellar heights. The patellofemoral contact force increased with increasing knee flexion until contact occurred between the quadriceps tendon and the femoral trochlea, inducing load sharing. Patella alta caused a delay of this contact until deeper flexion. As a consequence, the maximal patellofemoral contact force and contact pressure increased significantly with increasing patellar height (p <
0.01). Patella alta was associated with the highest maximal patellofemoral contact force and contact pressure. When averaged across all flexion angles, a normal patellar position was associated with the lowest contact pressures. Our results indicate that there is a biomechanical reason for anterior knee pain in patients with patella alta.
