Intraoperative pressure sensors allow surgeons to quantify soft-tissue balance during total knee arthroplasty (TKA). The aim of this study was to determine whether using sensors to achieve soft-tissue balance was more effective than manual balancing in improving outcomes in TKA. A multicentre randomized trial compared the outcomes of sensor balancing (SB) with manual balancing (MB) in 250 patients (285 TKAs). The primary outcome measure was the mean difference in the four Knee injury and Osteoarthritis Outcome Score subscales (ΔKOOS4) in the two groups, comparing the preoperative and two-year scores. Secondary outcomes included intraoperative balance data, additional patient-reported outcome measures (PROMs), and functional measures.Aims
Methods
To assess the effect of high tibial and distal femoral osteotomies
(HTO and DFO) on the pressure characteristics of the ankle joint. Varus and valgus malalignment of the knee was simulated in human
cadaver full-length legs. Testing included four measurements: baseline
malalignment, 5° and 10° re-aligning osteotomy, and control baseline
malalignment. For HTO, testing was rerun with the subtalar joint
fixed. In order to represent half body weight, a 300 N force was applied
onto the femoral head. Intra-articular sensors captured ankle pressure.Aims
Materials and Methods
Total knee replacement (TKR) smart tibial trials
have load-bearing sensors which will show quantitative compartment
pressure values and femoral-tibial tracking patterns. Without smart
trials, surgeons rely on feel and visual estimation of imbalance
to determine if the knee is optimally balanced. Corrective soft-tissue
releases are performed with minimal feedback as to what and how
much should be released. The smart tibial trials demonstrate graphically
where and how much imbalance is present, so that incremental releases
can be performed. The smart tibial trials now also incorporate accelerometers
which demonstrate the axial alignment. This now allows the surgeon
the option to perform a slight recut of the tibia or femur to provide
soft-tissue balance without performing soft-tissue releases. Using
a smart tibial trial to assist with soft-tissue releases or bone
re-cuts, improved patient outcomes have been demonstrated at one
year in a multicentre study of 135 patients (135 knees). Cite this article:
As many as 25% to 40% of unicompartmental knee
replacement (UKR) revisions are performed for pain, a possible cause
of which is proximal tibial strain. The aim of this study was to
examine the effect of UKR implant design and material on cortical
and cancellous proximal tibial strain in a synthetic bone model.
Composite Sawbone tibiae were implanted with cemented UKR components
of different designs, either all-polyethylene or metal-backed. The tibiae
were subsequently loaded in 500 N increments to 2500 N, unloading
between increments. Cortical surface strain was measured using a
digital image correlation technique. Cancellous damage was measured
using acoustic emission, an engineering technique that detects sonic
waves (‘hits’) produced when damage occurs in material. Anteromedial cortical surface strain showed significant differences
between implants at 1500 N and 2500 N in the proximal 10 mm only
(p <
0.001), with relative strain shielding in metal-backed implants.
Acoustic emission showed significant differences in cancellous bone
damage between implants at all loads (p = 0.001). All-polyethylene implants
displayed 16.6 times the total number of cumulative acoustic emission
hits as controls. All-polyethylene implants also displayed more
hits than controls at all loads (p <
0.001), more than metal-backed
implants at loads ≥ 1500 N (p <
0.001), and greater acoustic
emission activity on unloading than controls (p = 0.01), reflecting
a lack of implant stiffness. All-polyethylene implants were associated
with a significant increase in damage at the microscopic level compared
with metal-backed implants, even at low loads. All-polyethylene
implants should be used with caution in patients who are likely
to impose large loads across their knee joint. 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.
