Application of 3D–printed and patient-specific cast for the treatment of distal radius fractures: initial experience
- Yan-Jun Chen†1,
- Hui Lin†2,
- Xiaodong Zhang6,
- Wenhua Huang1Email author,
- Lin Shi2, 3, 4Email author and
- Defeng Wang2, 5
© The Author(s) 2017
Received: 4 May 2017
Accepted: 25 October 2017
Published: 9 November 2017
Distal radius fracture is common in the general population. Fracture management includes a plaster cast, splint and synthetic material cast to immobilise the injured arm. Casting complications are common in those conventional casting technologies. 3D printing technology is a rapidly increasing application in rehabilitation. However, there is no clinical study investigating the application of a 3D–printed orthopaedic cast for the treatment of bone fractures. We have developed a patient-specific casting technology fabricated by 3D printing. This pioneering study aims to use 3D–printed casts we developed for the treatment of distal radius fractures, to provide the foundation for conducting additional clinical trials, and to perform clinical assessments.
Ten patients with ages between 5 and 78 years are involved in the clinical trial. Patients are applied 3D–printed casts we developed. Orthopaedic surgeons carried out a six-week follow-up to examine clinical outcomes. Two questionnaires were developed for the assessment of clinical efficacy and patients’ satisfaction. These questionnaires are completed by physicians and participating patients.
A 3D–printed cast creates a custom-fitted design to maintain the fractured bone alignment. No loss of reduction is found in all patients. Compartment syndrome and pressure sores are not present. Patient comfort gets positive scores on the questionnaire. All (100%) of the patients opt for the 3D–printed cast instead of the conventional plaster cast.
A patient-specific, 3D–printed cast offers a proper fit to immobilise an injured arm and holds the fracture reduction appropriately. A custom-fitted structure reduces the risk of pressure-related complications due to the high and concentrated local stress. The ventilated and lightweight design minimises interference with a patient’s daily activities and reduces the risk of cutaneous complications. Patients express a strong preference for using a 3D–printed cast instead of a plaster cast. Limitations of the novel cast include a slight odour after heavy sweating and the relatively high cost due to the limitations of current 3D printing technologies.
This pioneering study is the first clinical trial on the application of a 3D–printed cast for the treatment of forearm fractures. The novel casting technology heals the fracture effectively without casting complications. The 3D–printed cast is patient-specific and ventilated as well as lightweight, and it features both increased patient comfort and satisfaction.
Distal radius fractures are common skeletal injuries and occurred at all ages of the general population [1, 2]. These types of fractures are reported as having one of the highest incidences accounting for over 15% of bone fractures [3, 4]. Distal radius fracture management usually includes a plaster cast, splint, and a moulded synthetic material cast to immobilise the injured upper extremity [5–9]. A normal course of the treatment includes the application of a cast and several follow-up clinical visits lasting four to six weeks [7, 10, 11]. The traditional casts are described as having both poor ventilation and an improper fit, while also causing discomfort. These morbidities associated with conventional casts may result in cast complications such as cutaneous diseases, bone and joint injuries, or malunion [7, 12, 13]. The rate of cast-related complications published is high with up to 31% being reported in published studies .
The 3D printing technology is rapidly advancing in medical applications . In the manufacture of rehabilitation tools, 3D printing technology is being applied to orthopaedic cast fabrication to create patient-specific features with an appropriate fit and a ventilated structure . Jake Evill and Deniz Karasahin proposed a novel design of casts with a web-like structure and fabricated it by using a 3D printing technique. The cast models were built from 3D–scanned images of subjects’ limbs and created by using computer-aided design software, which can generate a Stereolithography (STL) file, a standard file format widely used for 3D printing. Kim et al. developed a hybrid model of wrist orthosis composed of a 3D–printed frame and an injection moulding shell [16, 17]. Although 3D printing has made advances at a rapid pace in the development of casting techniques, all published technologies for the design and fabrication of 3D–printed casts are still in the concept stage without clinical application . To date, there is no clinical study investigating the application of 3D–printed casts .
Our previous published study has developed a rapid and intelligent technique to create a patient-specific orthopaedic cast fabricated by 3D printing . Orthopaedic surgeons with little knowledge of engineering can design a high-quality cast in a short amount of time by utilising the technique. The novel cast also has additional features such as being ventilated and hygienic advantages that potentially lower the risk of complications. To our knowledge, there is no published clinical trial using the 3D–printed cast for the treatment of distal radius fractures. This study is to perform a pioneer clinical trial for the casting technology utilising 3D–printed casts for the treatment of distal radius fractures.
Ten patients (age range from 5 to 78 years old) including four males and six females are involved in the clinical trial. There were six patients who suffered distal radius and ulnar styloid fractures. Distal radius fractures were present in three patients. One patient sustained fractures of both the distal radius and ulna. Exclusion criteria included pathological/open fractures, fractures requiring internal fixation and patients who were not available for local follow-up. All clinical trials were performed in southern China where the weather was humid and warm, normally above 30 degrees Celsius during the clinical testing period. Patients first underwent closed reduction using traditional plaster cast fixation due to tissue swelling. The first treatment stage lasted for one week after swelling subsided. 3D–printed orthopaedic casts developed by our published techniques  were applied to these patients after one week fixation. Two follow-up examinations and investigations were performed about the second and sixth week after the application of the 3D–printed cast [11, 19].
Assessment of clinical effectiveness of a 3D–printed cast
Assessment contents and grading standard
Stability of immobilisation
No loss of reduction
Slight shift but no need for re-manipulation
Reinforced same cast
Loss of reduction requiring further procedure
Good terminal circulation with a florid complexion
Venous obstruction relief after physical movement or arm lifting
Pale skin, low temperature of the arm
Significant ischaemia of involved limb, compartment syndrome
Slight pain with a minor influence on sleep
Mild pain caused poor-quality sleep
Severe pain caused difficulty falling asleep
No abnormality of the skin
Non-blanchable erythema of the intact skin
Skin breakdown or bleeding blister
Full thickness skin loss
Patient satisfaction questionnaire
Assessment contents and grading standard
Bad experience wearing cast
Strong willingness to try new cast
Dubious but complied
Patient preference between 3D–printed cast and conventional plaster cast
Opted for 3D–printed cast without hesitation
Preferred a 3D–printed cast to a plaster cast
Either cast is acceptable
Insisted on using conventional cast
Cast odour and smell
Slight cast odour
Smelly cast after heavy sweating
Frequent itch but tolerable
Patients were taught how to check for compartment syndrome by themselves within one week of the application of the 3D–printed cast. As one of the most serious complications of traditional casting techniques, compartment syndrome was not found in any of the patients examined in the second and sixth week after casting. Orthopaedic surgeons inspected the skin appearance under the cast, and no visual signs of pressure damage were found in these patients. Complications associated with compromised blood flow commonly occurring when using circumferential casts and splints were not present during the healing period.
An appropriate casting technique not only holds the fracture reduction at a proper anatomic position but also minimises the risks of complications related to distal fracture. Complications including cutaneous diseases, compartment syndrome and vascular comprise, have been reported in conventional cast application due to the unbalanced pressures and high stiffness [3, 12]. Traditional casting creating mould utilising plaster and thermoplastic has rigid structure without flexibility and poor ventilation. In addition, the swelling of soft tissue occurring in an injured forearm at the initial stage makes it difficult to create patient-specific features. 3D–printed casts are featured as patient-specific and fully ventilated as well as lightweight structures . 3D–printing technology is an image-based technology combined with rapid prototyping that can create a patient-specific cast in terms of injury regions and severity. An orthopaedic surgeon performs the closed reduction for a displaced fracture followed by casting fixation. Patient-specific features of casting play an important role to maintain the alignment and avoid loss of closed reduction. Moreover, the custom-fit structure ensures the matching surface geometry between the cast and arm and thus disperses pressure. The ventilated structure featured in the novel cast confers the benefits of improved patient comfort and reduced risk of cutaneous complications.
Acquisition of a patient’s image is an important process for performing cast design. In the imaging process, fracture patients are required to hold a special posture to keep the forearm or lower leg in a natural position. Participants with fractures have swollen arms where the original shapes are difficult to be discerned. This study proposes the mirror technique, which scans the counterpart of an injured limb. Eight out of 10 testing casts used the contralateral arm. Bilateral symmetry exists in natural biological structures. For example, surgeons assume the bilateral symmetry of the human skeletal system for surgery purposes. Also, Islam et al. demonstrated the symmetric morphology of some human bones . Thus, the mirror technique offers relatively accurate patient data and minimises imaging difficulties for the patient.
Pressure-related complications are reported with traditional casts, especially circular casts. The cast utilised for this study are designed as splitting and circular structures with padding components, which can split the cast to accommodate the injured limb and relieve pressure. Slightly slow circulation is found after two weeks of cast application due to the wearing pressure. Participated patients can relieve the symptom through raising the injured arms. Slight pain is developed from wearing pressure, but no complaint is reported from patients. Wearing pressures are necessary for any casting or splint technology to maintain the reduction of the fracture and perform orthopaedic corrections effectively . Patient-specific and 3D–printed casts develop proper fit by the shape of the injured arm and thus reduce the risk of stress concentration since large contact areas are created. Concentrated stress is considered as an important factor associated with compartment syndrome. These technical advantages are present in the clinical trial so that no cases have compartment syndrome.
There are some limitations of this study concerning casting technology and clinical testing. First, acquisition of a patient’s data is a challenge for a patient with a fracture. A patient is asked to keep a required position during scanning for the purpose of data integrity. Additionally, we use mirror technology to acquire the counterpart of the fractured arm. Variation between arms is shown in the normal anatomy. Further investigations should be required to evaluate the bilateral symmetry of human bones digitally. There is no complaint about the fitting issue by using the mirror technique. The availability of biocompatible materials for 3D printing fabrication is limited. We used polypropylene (PP) and polyamide (PA2200) with Young’s modulus 1300Mpa. As our experiences, a material with stiffness higher than 2000Mpa of Young’s modulus, like acrylonitrile butadiene styrene (ABS), may cause uncomfortable contact to the skin. In addition, although a ventilated structure has been created, physicians receive a few of complaints about the smelly cast from participating patients who sweat a lot in hot weather. It should be noted that all clinical trials were carried out in a southern Chinese city with hot and humid weather during the testing period. The fabrication cost of a 3D printing cast is relatively high, about $150 US Dollars, compared with conventional alternatives less than $50 US Dollars. The rapid growth of 3D printing technologies would reduce the fabrication cost in the near future. As a pilot study, we are mainly concerned with the clinical feasibility of the application of the 3D–printed cast. Due to the limited amount of patients, the initial study investigated a small-sized group without performing statistical analysis for comparison among conventional and 3D–printed casts.
As a new casting technology, we conducted the clinical trials with the focus on mild distal fracture. Cast design and 3D–printing fabrication would require a longer time. In emergency situations requiring a cast for the case of an acute fracture, as per our initial experiences, the 3D–printed cast would not be suggested currently. Its personalised structure and ventilated as well as lightweight design bring about quality patient experiences as confirmed by positive assessments of patient comfort and acceptance. Those two assessments would be helpful for the improvement of the current casting technology. This pilot study provides an initial experience on how to apply the 3D printing technique in the treatment of fractures. The future study would perform clinical trials on a larger scale sample size, and as a comparison study among conventional and 3D–printed casts to assess whether clinical differences were statistically significant.
This study performs a pilot study with the focus on the clinical trial for the treatment of distal radius fracture using patient-specific and 3D printing cast developed by our published techniques. The novel cast performs circumferential support for the fractured forearm and prevents the injury from external impact. The patient-specific design maintains the alignment of fracture bones and creates the custom-fit and moderate wearing pressure to avoid compartment syndrome and pressure sores, which is considered as the casting complication to challenge conventional casting technology. The ventilated structure and fashionable design of the novel cast combined with the 3D printing fabrication increase patient comfort and satisfaction. Superior clinical outcomes have been obtained from clinical trials.
The authors wish to acknowledge Diya Ma, Matthew-Lun Wong, Ka-Long Ko, Ka-Hei Ko and Jin-Peng Lee for their important contributions to the software development.
The work described in this paper was supported by a grant from the Research Grants Council of the Hong Kong Special Administrative Region, China (Project No.: CUHK 14113214), grants from the Innovation and Technology Commission (Project No: ITS/149/14FP, GHP/028/14SZ, ITS/293/14FP), grants from CUHK Technology and Business Development Fund (Project No.: TBF16MED002, TBF16MED004), a grant from The Science, Technology and Innovation Commission of Shenzhen Municipality (Project No.: CXZZ20140606164105361), and a grant from The Scientific Research Project of Guangdong Province (Project No.: 2014B090901055).
YC performed the clinical trial, designed the questionnaires and edited the manuscript. HL conceived the cast design, carried out the clinical trial, and both drafted and edited the manuscript. LS carried out data collection and analysis. XZ carried out data collection and provided clinical advice. WH conducted the clinical trial and critically revised the manuscript. DW carried out the method design and development and critically revised the manuscript. All authors read and approved the final manuscript.
Ethics approval and consent to participate
The study concerning the client’s right to privacy. The study was approved by the Ethical Committee of The Third Affiliated Hospital of Southern Medical University (reference number: 201,603,006) and was conducted according to the principles of the Declaration of Helsinki. The experimental methods used in the study were in accordance with medical practice, and the subjects were protected.
The authors declare that they have no competing interests.
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