Customized Three-Dimensional-Printed Orthopedic Close Contact Casts for the Treatment of Stable Ankle Fractures: Finite Element Analysis and a Pilot Study

Identification of excessive contact pressures under hand orthosis based on finite element analysis

BACKGROUND

Implicit magnitudes and distribution of excessive contact pressures under hand orthoses hinder clinicians from precisely adjusting them to relieve the pressures. To address this, contact pressure under a hand orthosis were analysed using finite element method.

METHODS

This paper proposed a method to numerically predict the relatively high magnitudes and critical distribution of contact pressures under hand orthosis through finite element analysis, to identify excessive contact pressure locations. The finite element model was established consisting of the hand, orthosis and bones. The hand and bones were assumed to be homogeneous and elastic bodies, and the orthosis was considered as an isotropic and elastic shell. Two predictions were conducted by assigning either low (fat) or high (skin) material stiffness to the hand model to attain the range of pressure magnitudes. An experiment was conducted to measure contact pressures at the predicted pressure locations.

RESULTS

Identical pressure distributions were obtained from both predictions with relatively high pressure values disseminated at 12 anatomical locations. The highest magnitude was found at the thumb metacarpophalangeal joint with the maximum pressure range from 13 to 78 KPa. The measured values were within the predicted range of pressure magnitudes. Moreover, 6 excessive contact pressure locations were identified.

CONCLUSIONS

The proposed method was verified by the measurement results. It renders understanding of interface conditions underneath the orthosis to inform clinicians regarding orthosis design and adjustment. It could also guide the development of 3D printed or sensorised orthosis by indicating optimal locations for perforations or pressure sensors.

Scaphoid numerical simulation of the critical loading until fracture

The numerical study of the scaphoid fracture, although it is relatively unexplored, can be of great clinical interest since it is highly common and can result in temporary or persistent disability. In this manuscript, seven combinations of boundary conditions and contacts between adjacent bones, together with four different loads, simulating real hand movements, are assessed. Three different fracture criteria for bones are employed to study the failure of the scaphoid with the aforementioned combination of interaction conditions. The results offer an interesting view of the accuracy of the possible interaction between adjacent bones. For future calculation, it would be possible to choose a combination of the balance between precision and computational cost savings. This study provides a comprehensive assessment into the modeling of the scaphoid bone and its interactions with adjacent bones. The findings reveal that various choices of interactions can yield similar results, allowing for flexibility in selecting interaction models based on desired accuracy or computational efficiency. Ultimately, this study establishes a foundational understanding for future research on modeling scaphoid motion.

Optimizing Spinal Fusion Cage Design to Improve Bone Substitute Filling on Varying Disc Heights: A 3D Printing Study

The success of spinal fusion surgery relies on the precise placement of bone grafts and minimizing scatter. This study aims to optimize cage design and bone substitute filling methods to enhance surgical outcomes. A 3D printed lumbar spine model was utilized to implant 3D printed cages of different heights (8 mm, 10 mm, 12 mm, and 14 mm) filled with BICERA® Bone Graft Substitute mixed with saline. Two filling methods, SG cage (side hole for grafting group, a specially designed innovative cage with side hole, post-implantation filling) and FP cage (finger-packing group, pre-implantation finger packing, traditional cage), were compared based on the weight of the implanted bone substitute. The results showed a significantly higher amount of bone substitute implanted in the SG cage group compared to the FP cage group. The quantity of bone substitute filled in the SG cage group increased with the height of the cage. However, in the FP cage group, no significant difference was observed between the 12 mm and 14 mm subgroups. Utilizing oblique lumbar interbody fusion cages with side holes for bone substitute filling after implantation offers several advantages. It reduces scatter and increases the amount of implanted bone substitute. Additionally, it effectively addresses the challenge of insufficient fusion surface area caused by gaps between the cage and endplates. The use of cages with side holes facilitates greater bone substitute implantation, ultimately enhancing the success of fusion. This study provides valuable insights for future advancements in oblique lumbar interbody fusion cage design, highlighting the effectiveness of using cages with side holes for bone substitute filling after implantation.

The NuroSleeve, a user-centered 3D printed hybrid orthosis for individuals with upper extremity impairment

BACKGROUND

Active upper extremity (UE) assistive devices have the potential to restore independent functional movement in individuals with UE impairment due to neuromuscular diseases or injury-induced chronic weakness. Academically fabricated UE assistive devices are not usually optimized for activities of daily living (ADLs), whereas commercially available alternatives tend to lack flexibility in control and activation methods. Both options are typically difficult to don and doff and may be uncomfortable for extensive daily use due to their lack of personalization. To overcome these limitations, we have designed, developed, and clinically evaluated the NuroSleeve, an innovative user-centered UE hybrid orthosis.

METHODS

This study introduces the design, implementation, and clinical evaluation of the NuroSleeve, a user-centered hybrid device that incorporates a lightweight, easy to don and doff 3D-printed motorized UE orthosis and a functional electrical stimulation (FES) component. Our primary goals are to develop a customized hybrid device that individuals with UE neuromuscular impairment can use to perform ADLs and to evaluate the benefits of incorporating the device into occupational therapy sessions. The trial is designed as a prospective, open-label, single-cohort feasibility study of eight-week sessions combined with at-home use of the device and implements an iterative device design process where feedback from participants and therapists informs design improvement cycles.

RESULTS

All participants learned how to independently don, doff, and use the NuroSleeve in ADLs, both in clinical therapy and in their home environments. All participants showed improvements in their Canadian Occupational Performance Measure (COPM), which was the primary clinical trial outcome measure. Furthermore, participants and therapists provided valuable feedback to guide further development.

CONCLUSIONS

Our results from non-clinical testing and clinical evaluation demonstrate that the NuroSleeve has met feasibility and safety goals and effectively improved independent voluntary function during ADLs. The study's encouraging preliminary findings indicate that the NuroSleeve has met its technical and clinical objectives while improving upon the limitations of the existing UE orthoses owing to its personalized and flexible approach to hardware and firmware design.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT04798378, https://clinicaltrials.gov/ct2/show/NCT04798378 , date of registration: March 15, 2021.

Personalized Offloading Treatments for Healing Plantar Diabetic Foot Ulcers

BACKGROUND

Non-removable knee-high devices are the gold-standard offloading treatments to heal plantar diabetic foot ulcers (DFUs). These devices are underused in practice for a variety of reasons. Recommending these devices for all patients, regardless of their circumstances and preferences influencing their ability to tolerate the devices, does not seem a fruitful approach.

PURPOSE

The aim of this article is to explore the potential implications of a more personalized approach to offloading DFUs and suggest avenues for future research and development.

METHODS

Non-removable knee-high devices effectively heal plantar DFUs by reducing plantar pressure and shear at the DFU, reducing weight-bearing activity and enforcing high adherence. We propose that future offloading devices should be developed that aim to optimize these mechanisms according to each individual's needs. We suggest three different approaches may be developed to achieve such personalized offloading treatment. First, we suggest modular devices, where different mechanical features (rocker-bottom sole, knee-high cast walls/struts, etc.) can be added or removed from the device to accommodate different patients' needs and the evolving needs of the patient throughout the treatment period. Second, advanced manufacturing techniques and novel materials could be used to personalize the design of their devices, thereby improving common hindrances to their use, such as devices being heavy, bulky, and hot. Third, sensors could be used to provide real-time feedback to patients and clinicians on plantar pressures, shear, weight-bearing activity, and adherence.

CONCLUSIONS

By the use of these approaches, we could provide patients with personalized devices to optimize plantar tissue stress, thereby improving clinical outcomes.

Polymeric Orthosis with Electromagnetic Stimulator Controlled by Mobile Application for Bone Fracture Healing: Evaluation of Design Concepts for Medical Use

Background: The occurrence of bone fractures is increasing worldwide, mainly due to the health problems that follow the aging population. The use of additive manufacturing and electrical stimulators can be applied for bioactive achievements in bone healing. However, such technologies are difficult to be transferred to medical practice. This work aims to develop an orthosis with a combined magnetic field (CFM) electrostimulator that demonstrates concepts and design aspects that facilitate its use in a real scenario. Methods: A 3D-printed orthosis made of two meshes was manufactured using PLA for outer mechanical stabilization mesh and TPU for inner fixation mesh to avoid mobilization. A CFM stimulator of reduced dimension controlled by a mobile application was coupled onto the orthosis. The design concepts were evaluated by health professionals and their resistance to chemical agents commonly used in daily activities were tested. Their thermal, chemical and electrical properties were also characterized. Results: No degradation was observed after exposure to chemical agents. The CMF achieved proper intensity (20-40 µT). The thermal analysis indicated its appropriate use for being modelled during clinical assessment. Conclusion: An orthosis with a coupled electrostimulator that works with a combined magnetic field and is controlled by mobile application was developed, and it has advantageous characteristics when compared to traditional techniques for application in real medical environments.