Introduction

Proper alignment (tibial alignment, femoral alignment, and overall anatomic alignment) of the prosthesis during total knee replacement is critical in maximizing implant survival[7] and to reduce polyethylene wear[1]. Poor overall anatomic alignment of a total knee replacement was associated with a 6.9 times greater risk of failure due to tibial collapse, that varus tibial alignment is associated with a 3.2 times greater risk[2] and valgus femoral alignment is associated with a 5.1 times greater risk of failure[7]. To reduce this variability intramedullary (IM) instruments have been widely used, with increased risk of the fat emboli rate to the lungs and brain during TKA[6] and possible increase of blood loss[4, 5]. Or, alternatively, navigation has been used to achieve proper alignment and to reduce morbidity[3]. Recently, for distal femoral resection, inertial sensors have been coupled to extramedullary (EM) instruments to improve TKA surgery in terms of femoral implant alignment, with respect to femoral mechanical axis, and reduced morbidity by avoidance of IM canal violation. The purpose if this study is to compare blood loss and alignment of distal femoral cut in three cohorts of patients: 1 Operated with inertial based cutting guide; 2 Operated with navigation instruments; 3 operated with conventional IM instruments.

The main purpose of the present study was to determine long-term implant fixation of 15 unicompartmental knee arthroplasty (UKAs) with an all-poly tibial component using Roentgen stereophotogrammetric analysis (RSA) at a mean 10-year follow-up. The secondary purpose was to investigate whether the progressive loss of implant's fixation correlates with a reduction in Knee society score (KSS). Fifteen non-consecutive patients with primary knee osteoarthritis received a UKA with an all-poly tibial component were assessed using KSS scores pre-operatively and post-operatively and RSA on day 2 after surgery, then at 3, 6, and 12 months and yearly thereafter. The mean last follow-up was 10 years. An increase in maximum total point motion (MTPM) values from 6 months to 1 year post-operatively was found respect to post-operative reference. Implants’ displacement values were always 2 mm during the first 6 months, and then, two different trends were noticed in revised and non-revised implants. MTPM increase between 1 and 2 years of follow-up in non-revised UKAs was always 0.2 mm, whereas it was [0.2 mm in revised UKAs. A linear and negative correlation with statistical significance was found between MTPM and both clinical and functional KSS scores (p 0.001). Also in a long-term follow-up evaluation, RSA is an effective tool to predict functional results after an all-poly UKA providing also a relevant predictive value at 1 year follow-up, and this can be very useful for both patients and surgeons.

The main purpose of the present study is to prospectively investigate whether preoperative functional flexion axis in patients with osteoarthritisand varus-alignment changes after total knee arthroplasty and whether a correlation exists both between preoperative functional flexion axis and native limb deformity. A navigated total knee arthroplasty was performed in 108 patients using a specific software to acquire passive joint kinematics before and after implant positioning. The knee was cycled through three passive range of motions, from 0 to 120. Functional flexion axis was computed using the mean helical axis algorithm. The angle between the functional flexion axis and the surgical transepicondylar axis was determined on frontal (aF) and axial (aA) plane. The pre- and postoperative hip-kneeankle angle, related to femur mechanical axis, was determined. Postoperative functional flexion axis was different from preoperative only on frontal plane, while no differences were found on axial plane. No correlation was found between preoperative aA and native limb deformity, while a poor correlation was found in frontal plane, between aF and preoperative hip-knee-ankle angle. Total knee arthroplasty affects functional flexion axis only on frontal plane while has no effect on axial plane. Preoperative functional flexion axis is in a more varus position respect to the transepicondylar axis both in pre- and postoperative conditions. Moreover, the position of the functional axis on frontal plane in preoperative conditions is dependent on native limb alignment, while on axial plane is not dependent on the amount of preoperative varus deformity.

Introduction

Providing proper rotational alignment of femoral component in total knee arthroplasty is mandatory to achieve correct kinematics, good ligament balance and proper patellar tracking. Recently functional references, like the function flexion axis (FFA), have been introduced to achieve this goal. Several studies reported the benefits of using the FFA but highlighted that further analyses are required to better verify the FFA applicability to the general clinical practice. Starting from the hypothesis that the FFA can thoroughly describe knee kinematics but that the joint kinematics itself can be different from flexion to extension movements, the purpose of this study was to analyse which factors could affect the FFA estimation by separately focusing on flexion and extension movements.

Introduction

Several methods, based on both functional and anatomical references, have been studied to reach the goal of a proper knee kinematics in total knee arthroplasty (TKA). However, at present, there is still a large debate about which is the most precise and accurate method to achieve the correct rotational implant positioning. One of the main methods already used in TKA to describe the tibiofemoral flexion-extension movement, based on a kinematic technique, thus not influenced by the typical variability related to the identification of anatomical references, is called “functional flexion axis” (FFA) method. The purpose of this study was to determine the repeatability in estimating knee functional flexion axis, thus evaluating the robustness of the method for navigated total knee arthroplasty.

Purpose:

Management of unicompartmental knee osteoarthritis (OA) in middle-aged patients is a challenging problem. Recent studies have underlined the efficacy of UKA not just in elderly, but also in middle-aged patients. The primary purpose of the present study was to determine the short to mid-term survivorship of an all-poly tibial UKA in patients under 60 years of age. The secondary purpose was to prospectively evaluate the clinical outcome in this selected group of patients.

BACKGROUND:

The optimal reference for rotational positioning of femoral component in total knee replacement (TKR) is debated. Navigation has been suggested for intra-op acquisition of patient's specific kinematics and functional flexion axis (FFA).

INTRODUCTION

The purpose of our work was to evaluate changes in clinical scores, passive knee kinematics and stability after mobile bearing TKA surgery.

INTRODUCTION

The literature suggests a survivorship of unicompartmental knee arthroplasties (UKA) for spontaneous osteonecrosisof the knee range from 93% to 96.7% at 10 to 12 years. However, these data arise from series reporting 23 to 33 patients, jeopardizing meaningful conclusions.

INTRODUCTION

Conventional surgical exposures are usually inadequate for 2-stage revision knee replacement ofinfected implants. Reduced range of motion, extensor mechanism stiffness, peripatellar contracture and soft tissue scarring make patellar eversion difficult and forced eversion places the integrity of the extensor mechanism at risk. On the contrary, a wide exposure is fundamental to allow complete cement spacer removal, soft tissue balancing, management of bone loss and reimplantation without damaging periarticular soft tissues.