Achieving Specified Laxity in a Noncruciate Total Knee: A Laboratory Design Study.

Background: Noncruciate total knee arthroplasty designs, including ultracongruent, medially congruent, and medial pivot, are gaining increasing attention in total knee arthroplasty surgery. However, there is no consensus for the bearing surface design, whether there should be different medial, lateral, anterior, and posterior laxities, or whether the medial side should be a medial pivot. This study proposes the criterion of reproducing the laxity of the anatomic knee, defined as the displacements and rotations of the femur on the tibia in the loaded knee when shear and torque are applied.

Design and evaluation of a 3D printed mechanical balancer for soft tissue balancing in total knee replacement.

Purpose: Soft tissue balancing is an important step in a total knee procedure, carried out manually, or using an indicator. The purpose of this study was to evaluate our design of 3D printed Balancer, and demonstrate how it could be used at surgery.

Procedures: When inserted between the femur and tibia, the Balancer displayed the forces acting across the lateral and medial compartments, indicated by pointers at the end of the handle.

Obtaining anatomic motion and laxity characteristics in a total knee design.

Background: Since the introduction of the first total knee designs, a frequent design goal has been to reproduce normal knee motion. However, studies of many currently used total knee designs, have shown that this goal has not been achieved. We proposed that Guided Motion total knee designs, could achieve more anatomic motion than present standard designs.

Investigation of Foot Sensor Insoles for Measuring Functional Outcome After Total Knee Replacement.

Background: To measure functional outcome, patient reported outcome measures (PROMs) are most often used but biomechanical tests can provide valuable supplementary data. The objective of this study was to investigate instrumented insoles for measuring ground-to-foot forces during basic activities.

Methods: Three groups were evaluated: normal controls, preoperative, and postoperative total knees.

The effect of total knee geometries on kinematics: An experimental study using a crouching machine.

Obtaining anatomic knee kinematics after a total knee is likely to improve outcomes. We used a crouching machine to compare the kinematics of standard condylar designs with guided motion designs. The standard condylars included femoral sagittal radii with constant radius, J-curve and G-curve; the tibial surfaces were of low and high constraint.

Principles of a 3D printed mechanical device for total knee balancing.

Implant alignment and soft-tissue balancing are important factors in total knee arthroplasty (TKA). The purpose of this study was to design a mechanical balancing device, which measures deflections resulting from forces applied on each condyle to provide numerical data indicating the extent of ligament release needed, or angular changes in the bone cuts required to achieve a balanced knee. Two mechanical devices were designed and 3D printed, Pistol Grip and In-line.

The Role of the Hindfoot in Total Knee Arthroplasty Alignment.

Limb alignment is a critically important factor to consider in the management of the patient with knee arthritis. Abnormal alignment is associated with the accelerated progression of osteoarthritis and, if not addressed at the time of surgery, may contribute to early failure of knee replacement implants. The contribution of the hindfoot to overall limb alignment has received limited attention in the context of deformity correction in total knee arthroplasty (TKA).

Guidelines for Instrumentation for Total Knee Replacement Based on Frontal Plane Radiographs.

Objective: The objective of this study was to measure the dimensions and the angulations of the femur and tibia for arthritic knees that were scheduled for total knee surgery. The purpose was to provide information for the design of surgical instruments such as cutting guides. Instruments made using three-dimensional printing were a particular consideration because of the variations in sizing that are possible.

Relationship between surgical balancing and outcome measures in total knees.

Background: The purpose of the study was to investigate the accuracy of balancing which could be achieved at total knee surgery and its relation to functional outcomes.

Methods: During surgery, the forces on the medial and lateral plateaus were measured at 10-15 degrees flexion in 101 patients, using an instrumented tibial trial, with equal forces being targeted. Of the initial 101 cases, 71 cases completed all follow-up visits to 1 year.

Feasibility of single-use 3D-printed instruments for total knee arthroplasty.

Aims: 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.

Materials And Methods: 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.

Relationship Between Ligament Forces and Contact Forces in Balancing at Total Knee Surgery.

Background: Spacer blocks, tensors, or instrumented tibial trials are current methods of balancing the knee during surgery but there are no current techniques for measuring ligament forces. Our goal was to study the relationship between the collateral ligament forces and the condylar contact forces to determine whether there was equivalence.

Methods: A test rig was constructed modeling an artificial knee joint with collateral ligaments.

Histological Analysis of the Effect of ATX-101 (Deoxycholic Acid Injection) on Subcutaneous Fat: Results From a Phase 1 Open-Label Study.

Background: ATX-101 is approved for submental fat reduction.

Objective: To characterize the histological effect of ATX-101 injection into subcutaneous fat.

Methods: This Phase 1 open-label study enrolled 14 adults to receive injections of ATX-101 into abdominal fat at varying concentrations (0.

Effects of femoral component placement on the balancing of a total knee at surgery.

Misalignment and soft-tissue imbalance in total knee arthroplasty (TKA) can cause discomfort, pain, inadequate motion and instability that may require revision surgery. Balancing can be defined as equal collateral ligament tensions or equal medial and lateral compartmental forces during the flexion range. Our goal was to study the effects on balancing of linear femoral component misplacements (proximal, distal, anterior, posterior); and different component rotations in mechanical alignment compared to kinematic alignment throughout the flexion path.

Measuring the sensitivity of total knee replacement kinematics and laxity to soft tissue imbalances.

Ligament balancing during total knee replacement (TKR) is receiving increased attention due to its influence on resulting joint kinematics and laxity. We employed a novel in vitro technique to measure the kinematics and laxity of TKR implants during gait, and measured how these characteristics are influenced by implant shape and soft tissue balancing, simulated using virtual ligaments. Compared with virtual ligaments that were equally balanced in flexion and extension, the largest changes in stance-phase tibiofemoral AP and IE kinematics occurred when the virtual ligaments were simulated to be tighter in extension (tibia offset 1.

The Hyperhidrosis Disease Severity Measure-Axillary: Conceptualization and Development of Item Content.

Introduction: Patients with primary axillary hyperhidrosis (AHH) suffer from a variety of symptoms. Improved patient-reported outcome (PRO) measures are needed to better assess and categorize the severity of AHH symptoms experienced by patients because the widely used Hyperhidrosis Disease Severity Scale (HDSS) is a single-item measure that cannot capture the broad scope of disease impact.

Methods: The Hyperhidrosis Disease Severity Measure-Axillary (HDSM-Ax) was developed for determining the severity of excessive sweating in patients with primary focal AHH based on face-to-face concept elicitation interviews with 58 AHH patients, a literature review, and expert clinical input.

OpenSim as a preliminary kinematic testing platform for the development of total knee arthroplasty implants.

The design of a total knee replacement implant needs to take account the complex surfaces of the knee which it is replacing. Ensuring design performance of the implant requires in vitro testing of the implant. A considerable amount of time is required to produce components and evaluate them inside an experimental setting.

Laxity and contact forces of total knee designed for anatomic motion: A cadaveric study.

Background: Total knee designs that attempt to reproduce more physiological knee kinematics are gaining attention given their possible improvement in functional outcomes. This study examined if a total knee designed for anatomic motion, where the soft tissue balancing was intended to replicate anatomical tibiofemoral contact forces, can more closely reproduce the laxity of the native knee.

Methods: In an ex-vivo setting, the laxity envelope of the knees from nine lower extremity specimens was measured using a rig that reproduced surgical conditions.

Surgical Accuracy of an Early Intervention Knee Implant Instrumentation System.

Accuracy of component and limb alignment are critical parameters for the long-term success of unicompartmental knee implants. In this study, we performed a laboratory evaluation of an instrumentation system which was designed for an early intervention (EI) type of unicompartmental knee. The accuracy of fit was evaluated by implanting in 20 sawbones full leg models.

Contact forces in the tibiofemoral joint from soft tissue tensions: Implications to soft tissue balancing in total knee arthroplasty.

Proper tension of the knee's soft tissue envelope is important during total knee arthroplasty; incorrect tensioning potentially leads to joint stiffness or instability. The latter remains an important trigger for revision surgery. The use of sensors quantifying the intra-articular loads, allows surgeons to assess the ligament tension at the time of surgery.

Mechanisms of anterior-posterior stability of the knee joint under load-bearing.

The anterior-posterior (AP) stability of the knee is an important aspect of functional performance. Studies have shown that the stability increases when compressive loads are applied, as indicated by reduced laxity, but the mechanism has not been fully explained. A test rig was designed which applied combinations of AP shear and compressive forces, and measured the AP displacements relative to the neutral position.

Analysis of an early intervention distal femoral resurfacing implant for medial osteoarthritis.

A design concept was formulated for implants to treat medial osteoarthritis of the knee, using a metal plate resurfacing of the tibia plateau and a plastic bearing embedded in the distal end of the femur. A finite element analysis was carried out to determine whether a metal backing would be needed for the femoral component, and to what extent the stress and strain distribution in the trabecular bone surrounding the implant would match the normal intact condition. The CT scans from three knees scheduled for unicompartmental replacement were selected to generate computer models with variable bone densities in each element to cover a range of density patterns.

Accuracy of Balancing at Total Knee Surgery Using an Instrumented Tibial Trial.

Background: Balancing is an important part of a total knee procedure, and in recent years, more emphasis has been given to quantifying the process.

Methods: During 101 total knee surgeries, initial bone cuts were made using navigation. Lateral and medial contact forces were determined throughout flexion using an instrumented tibial trial.

Relationship between meniscal integrity and risk factors for cartilage degeneration.

Background: The purpose of this study was to use MRI to determine if a loss of meniscal intra-substance integrity, as determined by T2* relaxation time, is associated with an increase of Kellgren-Lawrence (KL) grade, and if this was correlated with risk factors for cartilage degeneration, namely meniscal extrusion, contact area and anterior-posterior (AP) displacement.

Methods: Eleven symptomatic knees with a KL 2 to 4 and 11 control knees with a KL 0 to 1 were studied. A 3 Tesla MRI scanner was used to scan all knees at 15° of flexion.

Does Anteromedial Portal Drilling Improve Footprint Placement in Anterior Cruciate Ligament Reconstruction?

Background: Considerable debate remains over which anterior cruciate ligament (ACL) reconstruction technique can best restore knee stability. Traditionally, femoral tunnel drilling has been done through a previously drilled tibial tunnel; however, potential nonanatomic tunnel placement can produce a vertical graft, which although it would restore sagittal stability, it would not control rotational stability. To address this, some suggest that the femoral tunnel be created independently of the tibial tunnel through the use of an anteromedial (AM) portal, but whether this results in a more anatomic footprint or in stability comparable to that of the intact contralateral knee still remains controversial.

Evaluation of total knee mechanics using a crouching simulator with a synthetic knee substitute.

Mechanical evaluation of total knees is frequently required for aspects such as wear, strength, kinematics, contact areas, and force transmission. In order to carry out such tests, we developed a crouching simulator, based on the Oxford-type machine, with novel features including a synthetic knee including ligaments. The instrumentation and data processing methods enabled the determination of contact area locations and interface forces and moments, for a full flexion-extension cycle.