Variability, agreement and reliability of MRI knee landmarks.

Surface mesh reconstructions of bones are often required to define landmark-based coordinate systems, regions of interest and morphological features when studying the soft tissues of the knee from MRI scans. This study reports the variability, agreement and reliability of osseous landmarks to better understand their downstream effects. Fifteen landmarks were defined on the distal femur and twelve on the proximal tibia.

Sagittal shapes of current fixed-bearing unicompartmental knee replacements differ from those of normal knees.

Background: The principle when performing unicompartmental knee replacements (UKR), is to restore the natural alignment as well as the ligament tension. The tension in the ligaments is determined by the position of the joint line and the geometry of the articulating surfaces of the joint. If the surface geometry of the femoral component in a UKR is different from that of the natural knee it might cause abnormal ligament tension.

Estimating regions of interest on the distal femur.

We investigated the ability of a statistical shape model to estimate unknown regions of interest related to patient-specific unicompartmental knee replacement design on the distal femur. Generality ranged between 0.67 and 1.

Application of an artificial neural network and morphing techniques in the redesign of dysplastic trochlea.

Segmentation and computer assisted design tools have the potential to test the validity of simulated surgical procedures, e.g., trochleoplasty.

Development and testing of patient-specific knee replacements.

This study presents a design methodology for designing and manufacturing patient-specific unicompartmental knee replacements. The design methodology uses mathematical modeling and an artificial neural network to predict the original and healthy articulating surfaces of a patient's knee. The models are combined with medical images from the patient to create a knee prosthesis that is patient-specific.

Classification of gender and race in the distal femur using self organising maps.

In this study gender and race differences in distal femoral morphology were investigated. Reliable anatomic knee measurements were obtained for 60 knees via MRI and direct scanning of cadaver specimens. The MRI data comprised of 20 White males and 22 White females while the cadaver specimens comprised of 18 Black males.

Mathematical reconstruction of human femoral condyles.

There is a direct correlation between ligament function and the articulating surface of the normal knee, and changes to any of these structures can affect the other. This is also true for knee replacements, where the articulating surface is greatly changed compared to the natural knee. This study investigated the morphometry of healthy knees and proposes a method to predict original normal knee profiles.

Method for selection of femoral component in total knee arthroplasty (tka).

A method is proposed enabling a surgeon to preoperatively determine the preeminent type and size of prosthesis, from those available, to be used in a particular patient undergoing knee replacement surgery. Parameters of healthy knee geometry were estimated by employing an unsupervised neural network. These estimated parameters were then applied in a χ(2) goodness of fit (GoF) test to determine which femoral prosthesis type and size delivers the most appropriate fit.

Contact stresses in a patient-specific unicompartmental knee replacement.

A custom, patient-specific unicompartmental knee replacement was developed using a unsupervised neural network trained on a database of healthy knee geometries. This custom implant was then compared to a conventional implant in terms of contact stress in a Finite Element Model. The custom implant experienced lower contact stresses at the tibiofemoral joint compared to the conventional implant.

Comparison of two commercial patellofemoral prostheses by means of computational modeling.

There are many patellofemoral prostheses designs available for patellofemoral resurfacing, but few studies provide results objectively comparing these designs. In this study two designs are compared on the basis of patella kinematics and patellofemoral kinetics by means of a computational technique. Results indicated that the patellae displaced laterally after trochlear engagement, while tilt patterns were irregular between volunteers.

Contact stresses in a patient-specific unicompartmental knee replacement.

Background: Unicompartmental knee replacement has gained popularity in recent times, showing improved success rates. The main reasons for the failure of unicompartmental knee replacement are the wear of the polyethylene bearing, aseptic loosening and wear in the opposite compartment. The contact stresses involved are significant contributing factors to these causes of failure.

Anatomical study of the radius and center of curvature of the distal femoral condyle.

In this anatomical study, the anteroposterior curvature of the surface of 16 cadaveric distal femurs was examined in terms of radii and center point. Those two parameters attract high interest due to their significance for total knee arthroplasty. Basically, two different conclusions have been drawn in foregoing studies: (1) The curvature shows a constant radius and (2) the curvature shows a variable radius.

Management of overtight medial patellofemoral ligament reconstruction.

The clinical presentation of an overtight medial patellofemoral ligament (MPFL) reconstruction can differ depending on whether it is too tight in extension (extensor lag) or too tight in flexion (anterior knee pain and loss of flexion). We report one clinical case of each presentation. Both cases were treated with a percutaneous release of the graft.

Differential forces within the proximal patellar tendon as an explanation for the characteristic lesion of patellar tendinopathy: an in vivo descriptive experimental study.

Background: Patellar tendinopathy is a common condition affecting the posterior region of the proximal patellar tendon, but the reason for this typical location remains unclear.

Hypothesis: The posterior region of the proximal patellar tendon is subjected to greater tendinous forces than is the corresponding anterior region.

Study Design: Descriptive laboratory study.

Recurrent patellar dislocation after medial patellofemoral ligament reconstruction.

We report on three cases of recurrent lateral patellar dislocation following a medial patellofemoral ligament (MPFL) reconstruction for patellar instability. In all three cases, an isolated MPFL reconstruction was performed with a double autogenous gracilis graft. The patellar fixation was done through bone tunnels.

The favourable anisometry: an original concept for medial patellofemoral ligament reconstruction.

Medial patellofemoral ligament (MPFL) reconstruction for recurrent patellar dislocation has recently become more popular. We describe a technique that involves tensioning of the graft with the knee in full extension while simultaneously pulling with a bone hook on the patella in the direction of the quadriceps tendon, thus facilitating placement of the femoral attachment and accurate graft tensioning. We investigated the clinical outcome of this reconstructive procedure in 20 patients (23 knees), with a mean follow-up of 2 years.

Surgical biomechanics of the patellofemoral joint.

This review presents objective data, as far as possible, about the current understanding of the biomechanics of the patellofemoral joint as it pertains to the management of patellofemoral problems. When faced with a patellofemoral malfunction, it is important to check all the soft-tissue and articular geometry factors relating to the patella locally and not to neglect the overall lower limb alignment and function. It is important to remember that small alterations in alignment can result in significant alterations in patellofemoral joint stresses and that changes in the mechanics of the patellofemoral joint can also result in changes in the tibiofemoral compartments.