Purpose. Flat feet are an important cause of foot problems in children. The flexible flat foot is the most common form and is normally physiological and asymptomatic. Further assessment is necessary when a symptomatic flat foot persists. Surgical interventions are indicated when conservative therapies have failed. The Kalix arthroereisis is a surgical option and is placed in the subtalar joint of the foot, thereby preventing hyperpronation, and stabilizes the foot against excessive movements. The purpose of this study was to evaluate the functional and radiological outcomes of pediatric patients who had undergone a Kalix implantation for the treatment of a symptomatic flexible flat foot. Methods. Patient files of our institution were searched for patients who underwent a Kalix implantation between 2009 and 2014. Sixteen patients (26 feet) with symptomatic flexible flat feet were clinically and radiographically evaluated in this retrospective study. The calcaneal pitch and Meary”s angle were measured on the pre-, and postoperative follow-up radiographs and patient satisfaction survey was performed at follow-up to gain insight into functional outcome and satisfaction after the intervention. Results. Surgery was performed on an average age at 12.5 (range:10–15) years with a mean time from surgery to follow-up of 45.1±3.16 (range:18–78) months. There was a statistically significant increase in calcaneal pitch of 2.9° (11.7°to14.6°) and decrease in Meary”s angle of 15.8° (23.2° to7.85°) after surgery. The postoperative angles were maintained during follow-up, for both the calcaneal pitch (13.89°) and Meary”s angle (8.67°) in patients with the Kalix in situ (n=9/26) and in patients with the Kalix removed (15.4° and 7.8° respectively, n=17/26). The patient satisfaction survey shows that the majority of patients were satisfied regarding the state (81%) and appearance (75%) of their feet at follow-up. The majority never complained about their feet (81%) and heavy exercise was the major cause of complaints (23%). Limitations during walking were usually not the case (81%), though some patient experienced limitations during running (57%). Most reported preoperative complaints were pain, walking problems or a combination of both. The majority of these are relieved after surgery and patients were still asymptomatic at follow up. Conclusion. Kalix implantation improves the calcaneal pitch and Meary”s angle, thereby restoring foot anatomy towards a normal anatomy. These improvements were observed directly postoperatively and remained at follow-up. In addition, relieve of symptoms was observed postoperatively and the majority of patients were even satisfied at follow-up. We therefore suggest that Kalix arthroereisis is an appropriate treatment option for pediatric patients with symptomatic flexible flat feet. Significance. This was the first study evaluating functional and radiological outcomes of the Kalix arthroereisis in patients with symptomatic flexible flat feet

Biomedical imaging is essential in the diagnosis of musculoskeletal pathologies and postoperative evaluations. In this context, Cone-Beam technology-based Computed Tomography (CBCT) can make important contributions in orthopaedics. CBCT relies on divergent cone X-rays on the whole field of view and a rotating source-detector element to generate three-dimensional (3D) volumes. For the lower limb, they can allow acquisitions under real loading conditions, taking the name Weight-Bearing CBCT (WB-CBCT). Assessments at the foot, ankle, knee, and at the upper limb, can benefit from it in situations where loading is critical to understanding the interactions between anatomical structures. The present study reports 4 recent applications using WB-CBCT in an orthopaedic centre. Patient scans by WB-CBCT were collected for examinations of the lower limb in monopodal standing position. An initial volumetric reconstruction is obtained, and the DICOM file is segmented to obtain 3D bone models. A reference frame is then established on each bone model by virtual landmark palpation or principal component analysis. Based on the variance of the model point cloud, this analysis automatically calculates longitudinal, vertical and mid-lateral axes. Using the defined references, absolute or relative orientations of the bones can be calculated in 3D. In 19 diabetic patients, 3D reconstructed bone models of the foot under load were combined with plantar pressure measurement. Significant correlations were found between bone orientations, heights above the ground, and pressure values, revealing anatomic areas potentially prone to ulceration. In 4 patients enrolled for total ankle arthroplasty, preoperative 3D reconstructions were used for prosthetic design customization, allowing prosthesis-bone mismatch to be minimized. 20 knees with femoral ligament reconstruction were acquired with WB-CBCT and standard CT (in unloading). Bone reconstructions were used to assess congruency angle and patellar tilt and TT-TG. The values obtained show differences between loading and unloading, questioning what has been observed so far. Twenty flat feet were scanned before and after Grice surgery. WB-CBCT allowed characterization of the deformity and bone realignment after surgery, demonstrating the complexity and multi-planarity of the pathology. These applications show how a more complete and realistic 3D geometric characterization of the of lower limb bones is now possible in loading using WB-CBCT. This allows for more accurate diagnoses, surgical planning, and postoperative evaluations, even by automatisms. Other applications are in progress