## 4 Discussion  
The present work reports the results of a complete clinical trial using an original multi-instrument procedure to assess the biomechanical effects on the operated lower limb for a novel custom-made HTO system for the personalized surgical correction of large knee varus deformities. Outcomes according to medical imaging and clinical scores before and after HTO are reported, but mainly a thorough functional assessment was performed and discussed. This involved merging state-of-the-art gait analysis with individual knee bone models from CT scans taken in a weight-bearing position. The fully personalized surgical procedure should have guaranteed relevant biomechanical correction at the knee as well as at the hip and ankle joints. A considerable consistent improvement at these joints in all three  
Figure 6: Hip, knee and ankle joint kinetics on the sagittal, frontal and transverse plane versus % of the full gait cycle (stance phase, i.e., with the foot on the forceplate, finishing at about 60% of the cycle). Pre- and post-operative data (in %BWxH) are reported as mean curves \(\pm\) standard deviations for all patients, along with the associated comparison of pre–post data via SPM (SPM(t)), where t* indicates the critical value of t given the significance level \(\alpha\). anatomical planes was observed, supported also by a thorough statistical analysis of the whole gait cycle in level walking. From the original procedure, patient-specific patterns of GRF location on the tibial plateau were obtained from the foot strike to toe off. A number of previous papers have used standard gait analysis to assess kinematics and kinetics at the major joints of the lower limbs for HTO patients [27; 38; 39; 40]. The present procedure also originally included state-of-the-art technology to enhance skeletal modelling of the knee bones by using a modern cone beam CT scanner. This enables 3D reconstruction of bone segments in a weight-bearing position for a realistic full representation of the knee morphology and alignment [41; 42]. Though the correction angle for the present surgical intervention was determined only from the long-leg frontal radiograph, the 3D model of the distal femur, of the patella and of the proximal tibia supported the best possible location and orientation of the osteotomy, also including possible necessary realignments out of the frontal plane [23]. An overall high-accuracy realignment is expected to be enabled by the cutting jig and the plate, which were both designed to match the tibial bones and to accurately achieve the desired correction. A robust stabilization of the open wedge was also expected. Thus, the present thorough functional analysis was performed on patients who underwent a highly optimized HTO intervention. The present results show a good restoration after surgery not only of traditional radiographical alignment but also of the physiological kinematics and kinetics of the knee and the other joints of the operated lower limb. These findings concur with those reported in the literature regarding the positive effects of using customized approaches in HTO, such as subject-specific cutting jigs [43; 44], both in terms of knee joint line realignment and clinical outcomes. In addition, though the actual association between post-operative joint line correction and the clinical consequences after HTO for medial knee osteoarthritis apparently cannot yet be ascertained from the recent literature [45; 46; 47], the present post-operative clinical scores demonstrate overall significant improvements for the treated patients in terms of pain relief and normal gait restoration after surgery. One of the major claims of opening-wedge HTO is a lateral transfer of loads for a relevant decompression of the medial compartment of the varus knee, which allows for improved mediolateral weight distribution at the tibial plateau and a more steady and symmetrical overall posture [12; 13; 14].