Despite clear clinical advantages Unicompartimetal Knee Replacement (UKR) still remain a high demanding and less forgiving surgical procedure. Different Authors in literature pointed out how in coronal tibial malalignment beyond 3° as well as tibial slope beyond 7° increase the rate of aseptic failure. Likewise, overcorrection in the coronal plain is a well recognised cause of failure because of an overweighting on the controlateral compartment. Furthermore it has been shown how in UKR surgery even using short narrow intramedullary guide this can cause errors in both coronal planes. Computer assisted surgery has been proposed to improve implant positioning in joint replacement surgery with no need of intramedullary guide. Likewise more recently Patient Specific Instrumentation (PSI) has been suggested as a new technology capable of new advantages such as shorter surgical times and lower blood losses maintaining at least the same accuracy. Aim of this prospective study is to present comparing 2 groups of UKRs using either a computer assisted technique or a CT based PSI. Since January 2010 54 patients undergoing UKR because of medial compartment arthritis were prospectively enrolled in the study. Before surgery patients were alternatively assigned to either computer-assisted alignment (group A) or PSI group (group B). In the group A (27 knees) the implant (Sigma, Depuy Orthopaedics Inc, Warsaw, Indiana, USA) was positioned using a CT-free computer assisted alignment system specifically created for UKR surgery (OrthoKey, Delaware, USA USA). In group B (27knees) the implant (GMK uni, Medacta, Castel San Pietro, Switzerland) was performed using a CT-Based PSI technology (MyKnee, Medacta, Castel San Pietro, Switzerland). In both the groups all the implants were cemented and using always a fixed metal backed tibial component. The duration of surgery and all the complications according to Kim classification were documented in all cases. Six months after surgery each patient had long-leg standing anterior-posterior radiographs and lateral radiographs of the knee. The radiographs were assessed to determine the Frontal Femoral Component angle (FFC), the Frontal Tibial Component angle (FTC), the Hip-Knee-Ankle angle (HKA) and the sagittal orientation (slope) of both tibial and femoral component. The number and percentage of outliners for each parameter was determined. In addition the percentage of patients from each group with all 5 parameters within the desired range was calculated. Furthermore at the latest follow-up the 2 groups were clinically assessed using KSS and Functional score.INTRODUCTION
MATERIALS AND METHODS
A preoperative planning for accurately predicting the size and alignment of the prosthetic components may allow to perform a precise, efficient and reproducible total knee replacement. The planning can be carried out using as a support digital radiographic images or CT images with three-dimensional reconstruction. Aim of this prospective study is to evaluate and compare the accuracy of two different types of pre-operative planning, in determining the size of the femoral and tibial component in total knee arthroplasty performed with Patient Specific Instrument (PSI). The two compared techniques were: digital radiography and “CT-Based”. A prospective study was conducted to compare the accuracy in predicting the size of the prosthetic components in total knee replacement in 71 patients diagnosed with primary and symptomatic osteoarthritis of the knee. Inclusion criteria was “Easy Knee”: BMI ≤ 35, varus/valgus deviation ≤15° and residual flexion of the knee ≥ 90°. Pre-operatively all the patients underwent to the same standard protocol including digital radiographs with calibration and a CT scan. A dedicated IMPAX digital software (Agfa-Gevaert, NV, USA) was used to template the radiographs. The CT-based planning was performed on 3D reconstruction of CT scans of 3 joints: hip, knee and ankle, as established in standardised protocol to build up patient specific cutting mask (MyKnee, Medacta, Castel S. Pietro, Switzerland). All the surgeries were performed by 2 senior Authors (M.A and N.C.) using the same implant and the definitive component sizes implanted were registered and compared with the sizes suggested by both planning techniques considering also the range of error. Results analysis was carried out using nonparametric tests.INTRODUCTION
MATERIALS AND METHODS
