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.

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).

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.

Background

The reported outcomes of unicompartmental knee replacement (UKR) for spontaneous osteonecrosis of the knee (SPONK) often derive from small series with an average followup of 5 years, enabling to generate meaningful conclusions. Therefore, we determined the long-term functional results and the 10-years survivorship of the implant in all patients with advanced SPONK of the medial tibio-femoral compartment treated with a unicompartmental knee arthroplasty at our institute.

We performed a retrospective clinical and radiographic evaluation of 100 cases operated in our institute between February 1996 and March 2003 with a mean follow-up of 60 months to assess the efficiency of UKR performed with a new minimally invasive technique. The aim of this study is to correlate the clinical outcome of the patients with the pre- and post-op alignment, and with implant positioning on coronal and sagittal plane.

100 patients (23 ♂, 64 ♀) underwent cemented UKR (De Puy Preservation Uni with all poly tibial component), both for arthritis and osteonecrosis. At the pre-op clinical and radiographic evaluation, 82 patients presented a varus deformity, 5 patients a valgus deformity. The Hospital for Special Surgery Score (HSS) was used to determine the subjective and objective clinical status of the patients before and after the intervention.

Pre-op antero-posterior (AP) x-rays of the knee were executed to establish the femoro-tibial angle (FTA) and the angle between the affected tibial plateau and the tibial anatomical axis (PTA), while latero-lateral (LL) x-rays were performed to determine the posterior tibial slope (PS). To analyze ligamentous balancing, x-rays were performed both in supine and in plain weight bearing stance. Post-op, we performed supine AP e LL X-rays and at a mean follow-up of sixty months (12–84 months) we performed AP and LL plain weight bearing x-rays.

We considered a knee with FTA > 175° as varus knee, 170°< FTA< 175° as normal knee and an FTA < 170° as valgus knee. Moreover, we assumed a TPA > 90° for valgus knee and a TPA< 90° for varus knee.

According with HSS scoring system, at a mean follow-up of 60 months, 63 (76%) cases were excellent (100-85 points), 15 (18%) cases were good (84-70 points), 5 (6%) bad results (< 60 points). Our results demonstrate that patients with a pre-operative varus alignment of 7 degrees are slightly more likely to be selected for UKR. In our series, patients with an excellent clinical result presented pre-operatively a mean varus deformity of 7,9°. According to literature, we demonstrated that a small amount of undercorrection with a residual varus deformity of 3–5° is the goal to be reached in order to avoid both rapid degeneration of the non-replaced compartment as well as the premature loosening of the replaced compartment. We performed a mean axial correction of 5,1° leaving a mean axial varus deformity of 2,8° in the excellent group. In our series the group with excellent results also showed a post-operative PTS of 7,1°, while mean pre-operative PTS was 6,6°. Moreover, the further our radiographic findings were from the optimal position suggested, the worst were the results : a decrease was evident comparing excellent group with good group and this was even more marked comparing excellent group with bad results group.

Arthroscopic selective resurfacing of the knee may be considered a treatment option for selected patients with focal articular damage.

From more than 2 years in IX Division of Rizzoli Orthopaedics Institute(Bologna- Italy) we use, in selected cases with only one articular compartment damaged, an innovative resurfacing prosthesis.

We mad a new design of focal resurfacing (MAIOR) that is possible to implant with arthroscopic technique and that realize both mini-invasive and mini-traumatic surgery.

The fixation method of the MAIOR allows higher osteointegration by biomaterials and hydrossiapatite of new generation that permit a press-fit fixation of the implant.

The new philosophy of this implant consist of early focal treatment with low compromise of bone. Many surgeons, in case of focal articular damage, prefer to attend to made an unique definitive surgical operation when the degenerative changes are more severe.

This new implant permit to substitute, also in arthroscopic technique, only the articular damage and to avoid to attend a more important and diffuse articualr damage.

It is an uncemented, focal resurfacing prosthesis that requires minimal bone sacrifice and utilizes a minimal invasive surgical (MIS) approach with or without arthroscopic assistance.

In a prospective and consecutive study, 78 patients were followed up at least for 12 months. Subjective pain and joint function were assessed using Visual analogue scale (VAS) and Knee society scores respectively. The preliminary results are interesting and encouraging with subjective evaluation equal to 85% of normal knee.

Significant reduction of pain and improvement in joint function was observed. Although, long term study will determine the real performance of the prosthesis, trend seems to be positive.

Information on knee kinematics during surgery is currently lacking. The aim of this study is to describe intra-operative kinematics evaluations during uni-compartmental knee arthroplasty (UKA) and total knee arthroplasty (TKA) by mean of a navigation system. Anatomical and kinematic data were acquired by Kin-Nav navigation system and analysed by a dedicated elaboration software developed at our laboratory. The study was conducted on 20 patients: 10 patients undergoing mini-invasive UKA and 10 patients undergoing posterior-substituting-rotating-platform TKA. In both group of patients the surgeon performed passive knee flexion immediately before and immediately after the prosthetic implant. Pattern and amount of internal/external tibial rotation in function of flexion were computed and significant changes between before and after implant were evaluated adopting Student’s t-test (significant level p=0.05).

UKA implant did not significantly change the pattern of internal/external tibial rotation, nor the total magnitude of tibial rotation (15.75°±7.27°) during range of flexion (10°–110°), compared to pre-operative values (17.87°±7.34°, p=0.25). Magnitude of tibial rotation in TKA group before surgery (8.00°±3.67°) was significantly less compared to UKA patients and did not changed significantly after implant (5.96°±4.88°, p=0.09). Pattern of rotation before and after TKA implant were different between each other and between pattern in UKA patients both before and after implant.

Intra-operative evaluations on tibial rotation during knee flexion confirmed some assumptions on knee implants from post-operative methods and suggest a more extensive use of surgical navigation systems for kinematic studies.

Total knee arthroplasty (TKA) is actually a satisfactory technique to reduce pain and enhance mobility in osteoartritic pathologies (OA) of the knee. However, life of the implant is strictly dependent on restoration of correct knee kinematics, as alteration of motion pattern could led to abnormal wear in prosthetic components and also damage soft tissues. The aim of our study was to evaluate new kinematic tests to be performed during surgery in order to improve the standard intra-operative evaluation of the outcome on the individual case. We used Kin-Nav navigation system to acquire anatomic and kinematic data, which were analysed by a dedicated elaboration software developed at our laboratory. Ten patients undergoing rotating platform cruciate substituting TKA were considered for this study. Immediately before the implant and immediately after component positioning, the surgeon performed 3 complete knee flexion imposing internal tibial rotation (IPROM) and 3 complete knee flexion imposing external tibial rotation (EPROM). Tibial rotation during IPROM and EPROM tests was plotted in function of flexion (in the range 10°–110°). Repeatability of IPROM and EPROM was tested by calculating ICC (Intra-class Correlation Coefficient) between 3 repeated curves. Distance between IPROM curve and EPROM curve was computed at various degree of flexion. Maximum distance obtained during all range of flexion before and after the implant were compared by Student’s t-test (significant level p=0.05).

ICC for repeated motions were 0.99 for IPROM and 0.98 for EPROM. Maximum distance between tibial rotation in IPROM and EPROM was 27.82±6.98 before implant and significantly increased (p=0.001) to 40.09±6.92 after TKA. In one case we observed that the value remained similar before and after implant (from 33.11 to 33.98) while in one case we observed very large increase of rotation (from 30.56 to 50.01).

The proposed kinematic tests were able to quantify the increase of tibial rotation after TKA implant. Future development of the study are encouraging and will include a larger sample and reflections on individual findings.

Aims: This work describes a new intraoperative computer-assisted method for the evaluation of joint kinematics in both total (TKA) and uni-compartmental (UKA) knee arthroplasty. We report schematically the protocol and the preliminary in-vivo results we obtained on 11 patients (9 UKA – 2 TKA).

Methods: The system consists of an optoelectronic localizer, 2 reference arrays and a dedicated acquisition software, that permits the real-time control of limb position and allows the acquisition of joint motions. After a first phase of registration (anatomical landmarks identification) the surgeon executes, both before and after the reconstruction, a series of passive tests: range of motion (PROM) evaluation, varus-valgus (VV) stress at 0°, and VV at 30°. Furthermore the surgeon can acquire also anatomical surfaces (tibial plateaus, femoral condyles, prosthetic components, etc.). The 3D kinematic evaluations and anatomical data are recorded before and after the joint reconstruction. This new methodology has been used during 11 interventions fulfilled at our institute. We compare the PROM results with literature, and we also analyzed the interoperator repeatability in the execution of the tests (3 repetitions performed by a senior surgeon).

Results: The kinematic analysis of the PROM showed that there were no significant differences between per-operative and post-operative in all UKA cases. In the 2 TKR cases internal-external (IE) rotations appeared reduced after the implant, but further data are necessary to have a statistical evidence. The extension was improved both in UKA and TKA. The VV laxity at 0 ° was significantly reduced (p < 0.001), while at 30 ° stayed constant (p = 0.010). In all the TKR cases the evaluation of contact areas between femoral and tibial components showed normal pattern, and in UKA the contacts remain inside the prosthesis areas. Measured kinematic parameters (knee rotations, screw-home mechanism and alignment) were comparable with literature and manual estimation at surgical time.

Conclusions: The proposed protocol optimizes surgical times and minimizes invasiveness. The preliminary results showed that the system is able to quantify new kinematic parameters during intraoperative evaluations, provides data about alignments, gaps, stability and 3D motions of the individual knee and therefore can allow an accurate and real-time estimation of the passive knee function. Moreover the new 3D anatomical and kinematic data can improve the biomechanical understanding of the pathological and prosthetic knees.

Aims: In Revision Total Knee Arthroplasty (RTKA), bone deficiencies and lack of anatomical references make it difficult to understand the normal knee kinematic and adequately plan the intervention. To our knowledge there are no data about computer assisted navigation system specifically developed for RTKA in the literature and existing navigated techniques for RTKA use navigation systems developed for primary TKA. A new computer assisted technique for RTKA is presented.

Methods: This technique is based on the use of a navigation system, RTKANav consisting of an optical localizer, a dedicated software and some navigated tools specifically done for RTKA. The system doesn’t use medical images, and patient anatomy model is represented with dots and lines corresponding to acquired landmarks, providing the surgeon with the main references for the intervention monitored in real-time. During the most critical steps of the intervention (soft tissue balancing and the consequent choice of implant size, and joint line height restoration), the system provide the surgeon with graphical and numerical tools to improve the surgical outcome. Several criteria to set each degree of freedom of prosthetic components are considered and compared, and even if some required landmarks can not be identified, the system is always able suggest an intervention plan. The surgeon is provided with tools to analyze and modify the proposed plan, and to reproduce it on the patient.

Results: Till now the presented technique was used on five patients by an expert surgeon. Qualitative results, collected after the intervention through a questionnaire on surgeon feelings, in order to assess the functionality, user friendliness and the data visualization criteria implemented were very satisfying. System reliability was assessed intraoperatively analyzing joint line height, limb alignment and knee stability using trial components: based on his experience, the surgeon checked some acceptable components combination and compared the corresponding outcome with the one provided by the implant planned by the system. In three out five cases the suggested implant was considered the best by the surgeon, while in one case he decided to change the tibial insert of one size because of knee instability and in another case he changed the tibial component of one size because the planned one was too small. Final limb alignment evaluated with postoperative x-rays, was satisfactory in all cases.

Conclusions: Presented navigation system showed early promising results providing the surgeon with intraoperative quantitative and qualitative information on the main surgical parameters, useful to achieve a satisfactory prosthesis implant. Moreover this system use anatomical patient specific landmarks acquired after prosthesys removal, while navigation systems developed for primary TKA use both reference taken from preoperative x-rays and anatomical references acquired on metal component to be removed. Therefore in this case the operation planning is based on rough anatomical landmarks that do not reflect patients original anatomy.

A computer assisted technique for TKA Revision is presented. It is based on the use of a navigation system, RTKANav consisting of anl optical localizer, a dedicated software specifically done for TKA revision and some navigated tools developed for this application.

The system doesn’t use any patient model derived from medical images, but on the system interface patient anatomy model is represented with dots and lines corresponding to acquired landmarks and data derived from them. These data describe the main anatomical features and provide the surgeon with the main references for the intervention; angles between the mechanical axes can be controlled and monitored at any time.

Even if during acquisition phase some specific points can not be identified, since for each prosthetic component several criteria to set each degree of freedom are considered and compared, the system is always able suggest an intervention plan.

The system provides the surgeon with tools to analyse and modify the proposed plan, and to reproduce it on the patient.

Navigated technique validation is under development. Till now it was used on two patients by an expert surgeon. Computer guidance showed early promising results providing the surgeon with useful indications achieve a satisfactory prosthesis implant.

Introduction: In the last years matrix autologous chondrocyte transplantation becomes a possible solution in the treatment of chondral lesions. We develop an arthroscopic procedure for chondrocyte implant on hyaluronian-based scaffold.

Material and methods: Thirty-five patients treated using this technique achieved 3 years follow up. All the patients were clinically evaluated using IKDC score and with MRI or TC scan. In some Patients we performed a second look arthroscopy and histological evaluation.

Results: IKDC objective score improved after 12 months in all patients and the results were confirmed at 24 and 36 months of follow-up. The improving was obtained also according to IKDC subjective score. A second look arthroscopy showed healing of the defect with regenerated cartilage. The histological evaluation has demonstrated in 80% the hyaline type of new cartilage.

Conclusions: This matrix autologous chondrocyte transplantation procedure avoids the use of periosteal flap, simplify the surgical procedure and permit to perform the arthroscopic implant reducing the morbidity of the procedure. The preliminary clinical and histological results at 3 years follow-up are encouraging.