Among the advanced technology developed and tested for orthopaedic surgery, the Rizzoli (IOR) has a long experience on custom-made design and implant of devices for joint and bone replacements. This follows the recent advancements in additive manufacturing, which now allows to obtain products also in metal alloy by deposition of material layer-by-layer according to a digital model. The process starts from medical image, goes through anatomical modelling, prosthesis design, prototyping, and final production in 3D printers and in case post-production. These devices have demonstrated already to be accurate enough to address properly the specific needs and conditions of the patient and of his/her physician. These guarantee also minimum removal of the tissues, partial replacements, no size related issues, minimal invasiveness, limited instrumentation. The thorough preparation of the treatment results also in a considerable shortening of the surgical and of recovery time. The necessary additional efforts and costs of custom-made implants seem to be well balanced by these advantages and savings, which shall include the lower failures and revision surgery rates. This also allows thoughtful optimization of the component-to-bone interfaces, by advanced lattice structures, with topologies mimicking the trabecular bone, possibly to promote osteointegration and to prevent infection. IOR's experience comprises all sub-disciplines and anatomical areas, here mentioned in historical order. Originally, several systems of Patient-Specific instrumentation have been exploited in total knee and total ankle replacements. A few massive osteoarticular reconstructions in the shank and foot for severe bone fractures were performed, starting from mirroring the contralateral area. Something very similar was performed also for pelvic surgery in the Oncology department, where massive skeletal reconstructions for bone tumours are necessary. To this aim, in addition to the standard anatomical modelling, prosthesis design, technical/technological refinements, and manufacturing, surgical guides for the correct execution of the osteotomies are also designed and 3D printed. Another original experience is about en-block replacement of vertebral bodies for severe bone loss, in particular for tumours. In this project, technological and biological aspects have also been addressed, to enhance osteointegration and to diminish the risk of infection. In our series there is also a case of successful custom reconstruction of the anterior chest wall. Initial experiences are in progress also for shoulder and elbow surgery, in particular for pre-op planning and surgical guide design in complex re-alignment osteotomies for severe bone deformities. Also in complex flat-foot deformities, in preparation of surgical corrections, 3D digital reconstruction and 3D printing in cheap ABS filaments have been valuable, for indication, planning of surgery and patient communication; with special materials mimicking bone strength, these 3D physical models are precious also for training and preparation of the surgery. In Paediatric surgery severe multi planar & multifocal deformities in children are addressed with personalized pre-op planning and custom cutting-guides for the necessary osteotomies, most of which require custom allografts. A number of complex hip revision surgeries have been performed, where 3D reconstruction for possible final solutions with exact implants on the remaining bone were developed. Elective surgery has been addressed as well, in particular the customization of an original total ankle replacement designed at IOR. Also a novel system with a high-tibial-osteotomy, including a custom cutting jig and the fixation plate was tested. An initial experience for the design and test of custom ankle & foot orthotics is also in progress, starting with 3D surface scanning of the shank and foot including the plantar aspect. Clearly, for achieving these results, multi-disciplinary teams have been formed, including physicians, radiologists, bioengineers and technologists, working together for the same goal.
The flat foot is a frequent deformity in children and results in various levels of functional alterations. A diagnosis based on foot morphology is not sufficient to define the therapeutic approach. In fact, the degree of severity of the deformity and the effects of treatments require careful functional assessment. In case of functional flatfoot, subtalar arthroereisis is the surgical treatment of choice. The aim of this study is to evaluate and compare the functional outcomes of two different bioabsorbable implants designed for subtalar arthroereisis in childhood severe flat foot by means of thorough gait analysis. Ten children (11.3 ± 1.6 yrs, 19.7 ± 2.8 BMI) were operated for flat foot correction [1,2] in both feet, one with the calcaneo-stop method, i.e. a screw implanted into the calcaneus, the other with an endoprosthesis implanted into the sinus-tarsi. Gait analysis was performed pre- and 24 month post-operatively using a 8-camera motion system (Vicon, UK) and a surface EMG system (Cometa, Italy) to detect muscular activation of the main lower limb muscles. A combination of established protocols, for lower limb [3] and multi-segment foot [4] kinematic analysis, was used to calculate joint rotations and moments during three level walking trials for each patient. At the foot, the tibio-talar, Chopart, Lisfranc, 1st metatarso-phalangeal joints were tracked in three-dimensions, together with the medial longitudinal arch. Significant differences in standard X-ray measurements were observed between pre- and post-op, but not between the two treatment groups. Analysis of the kinematic variables revealed functional improvements after surgery. In particular, a reduction of eversion between the shank and calcaneus (about 15° on average) and a reduction of inversion between metatarsus and calcaneus (about 18° on average) were detected between pre- and post-operatively after both treatments. Activation of the main plantar/dorsiflexor muscles was similar at both pre- and post-op assessments with both implants. The combined lower limb and multi-segment foot kinematic analyses were found adequate to provide accurate functional assessment of the feet and of the lower limbs. Both surgical treatments restored nearly normal kinematics of the foot and of the lower limb joints, associated also to a physiologic muscular activation.
In podiatric medicine, diagnosis of foot disorders is often merely based on tests of foot function in static conditions or on visual assessment of the patient's gait. There is a lack of tools for the analysis of foot type and for diagnosis of foot ailments. In fact, static footprints obtained via carbon paper imprint material have traditionally been used to determine the foot type or highlight foot regions presenting excessive plantar pressure, and the data currently available to podiatrists and orthotists on foot function during dynamic activities, such as walking or running, are scarce. The device presented in this paper aims to improve current foot diagnosis by providing an objective evaluation of foot function based on pedobarographic parameters recorded during walking. 23 healthy subjects (16 female, 7 males; age 35 ± 15 years; weight 65.3 ± 12.7; height 165 ± 7 cm) with different foot types volunteered in the study. Subjects' feet were visually inspected with a podoscope to assess the foot type. A tool, comprised of a 2304-sensor pressure plate (P-walk, BTS, Italy) and an ad-hoc software written in Matlab (The Mathworks, US), was used to estimate plantar foot morphology and functional parameters from plantar pressure data. Foot dimensions and arch-index, i.e. the ratio between midfoot and whole footprint area, were assessed against measurements obtained with a custom measurement rig and a laser-based foot scanner (iQube, Delcam, UK). The subjects were asked to walk along a 6m walkway instrumented with the pressure plate. In order to assess the tool capability to discriminate between the most typical walking patterns, each subject was asked to walk with the foot in forcibly pronated and supinated postures. Additionally, the pressure plate orientation was set to +15°, +30°, −15° and −30° with respect to the walkway main direction to assess the accuracy in measuring the foot progression angle (i.e. the angle between the foot axis and the direction of walk). At least 5 walking trials were recorded for each foot in each plate configuration and foot posture. The device allowed to estimate foot length with a maximum error of 5% and foot breadth with an error of 1%. As expected, the arch-index estimated by the device was the lowest in the cavus-feet group (0.12 ± 0.04) and the highest in the flat-feet group (0.29 ± 0.03). These values were between 4 – 10 % lower than the same measurements obtained with the foot scanner. The centre of pressure excursion index [1] was the lowest in the forcibly-pronated foot and the largest in the supinated foot. While the pressure plate used here has some limitations in terms of spatial resolution and sensor technology [2], the tool appears capable to provide information on foot morphology and foot function with satisfying accuracy. Patient's instrumental examination takes only few minutes and the data can be used by podiatrists to improve the diagnosis of foot ailments, and by orthotists to design or recommend the best orthotics to treat the foot condition.
Rehabilitation systems based on inertial measurement units (IMU) and bio-feedbacks are increasingly used in many different settings for patients with neurological disorders such as Parkinson disease or balance impairment, and more recently for functional recover after orthopedic surgical interventions or injuries especially concerning the lower limb. These systems claim to provide a more controlled and correct execution of the motion exercises to be performed within the rehabilitation programs, hopefully resulting in a better outcomes with respect to the traditional direct support of a physical therapists. In particular recruitment of specific muscles during the exercise is expression of its correct and finalized execution. The objective of this study was to compare muscular activation patterns of relevant lower limb muscles during different exercises performed with traditional rehabilitation and with a new validated system based on IMU and biofeedback (Riablo, Corehab, Trento, Italy). Twelve healthy subjects (mean age 28.1 ± 3.9, BMI 21.8± 2.1) were evaluated in a rehabilitation center. Muscular activation pattern of gluteus maximum, gluteus medium, rectus femoris and biceps femoris was recorded through surface EMG (Cometa; Milan) during six different motion tasks: hip abduction in standing position, lunge, hip flexion with extended knee in standing position, lateral lunge, hip abduction with extended knee in lateral decubitus, squat. Subjects performed 10 repetitions of each task for a total of 100 repetitions per motion task, with and without Riablo System as well as during standard rehabilitation. An additional IMU was positioned on the shank in order to detect beginning and end of each repetition. A single threshold algorithm was used to identify muscle activation timing. During hip abduction in standing position, gluteus maximum and rectus femoris showed a better and longer activation pattern while using Riablo compared to traditional rehabilitation. Gluteus medium showed a similar activation pattern whereas biceps femoris showed no activation from 30% to 80% using Riablo. During squat, rectus femoris and biceps femoris had a similar activation pattern with and without Riablo whereas gluteus maximum and gluteus medium showed a better activation pattern while using Riablo. The recent development of innovative rehabilitation systems meets the need of manageable, reliable and efficient instruments able to reduce rehabilitation costs but with the same good clinical outcomes. Muscular activation patterns of relevant lower limb muscles during selected motion tasks reveal their correct execution. The use of this new rehabilitation system based on IMU and biofeedback seems to allow a more selective and effective muscular recruitment, likely due to the more correct and controlled execution of the exercise, particularly for the identification and interdiction of possible compensation mechanisms.
Total ankle replacement (TAR) is the main surgical option in case of severe joint osteoarthritis. The high failure rate of current TAR is often associated to inappropriate prosthetic articulating surfaces designed according to old biomechanical concepts such the fixed axis of rotation, thus resulting in non-physiological joint motion. A recent image-based 3D morphological study of the normal ankle (Siegler et al. 2014) has demonstrated that the ankle joint surfaces can be approximated by a saddle-shaped cone with its apex located laterally (SSCL). We aimed at comparing the kinematic effects of this original solution both with the intact joint and with the traditional prosthetic articulating surfaces via in-silico models and in-vitro measurements. Native 3D morphology of ten normal cadaver ankle specimens was reconstructed via MRI and CT images. Three custom-fit ankle joint models were then developed, according to the most common TAR designs: cylindrical, symmetrically-truncated medial apex cone (as in Inman's pioneering measures), and the novel lateral apex cone, i.e. SSCL. Bone-to-bone motion, surface-to-surface distance maps, and ligament forces and deformations were evaluated via computer simulation. Prototypes of corresponding prosthesis components were designed and manufactured via 3D-printing, both in polymer-like-carbon and in cobalt-chromium-molybdenum powders, for in-vitro tests on the cadaver specimens. A custom testing rig was used for application of external moments to the ankle joint in the three anatomical planes; a motion tracking system with trackers pinned into the bone was used to measure tibial, talar and calcaneal motion (Franci et al. 2009), represented then as tibiotalar, subtalar and ankle complex 3D joint rotations. Each ankle specimen was tested in the intact joint configuration and after replacement of the articulating surfaces according with the three joint models: cylindrical, medial apex cone and SSCL. Results. Small intra-specimen data variability in cycle-to-cycle joint kinematics was found in all cadaver ankles, the maximum standard deviation of all rotation patterns being smaller than 2.0 deg. In-silico ligament strain/stress analysis and in-vitro joint kinematic and load transfer measurements revealed that the novel SSCL surfaces reproduce more natural joint patterns than those with the most common surfaces used in current TAR. TAR based on a saddle-shaped skewed truncated cone with lateral apex is expected to restore more normal joint function. Additional tests are undergoing for further biomechanical validation. The present study has also demonstrated the feasibility and the quality of the full process of custom TAR design and production for any specific subject. This implies a thorough procedure, from medical imaging to the production of artificial surfaces via 3D printing, which is allowing for personalised implants to become the future standard in total joint replacement.
