3D Printing Adjustable Stiffness External Fixator for Mechanically Stimulated Healing of Tibial Fractures

External fixation is a long-standing but well-established method, which has been widely used for the treatment of fractures. To obtain the maximum benefit from the mechanical stimulus, the stiffness of the external fixator should be adjusted properly throughout the treatment phase. Nevertheless, the lack of a valid dynamic adjustable fixation device impedes this possibility. Based on the stiffness adjustment tolerance of the healing callus, this paper proposes an active-dynamic stiffness adjustable external fixator design method to meet stiffness requirements at different stages of the tibial fracture healing process. A novel external fixator with an adjustable stiffness configuration was designed, and the finite element method was used to simulate the stress distribution between fixator and fracture gap. The stiffness adjustment tolerance was determined based on previous studies. According to this tolerance, the optimal block structure dismantling sequence was sought and the corresponding stiffness was calculated through topology optimization for the entire external fixator model. The appropriate amount of variable stiffness at the fracture gap was applied by dismantling the configuration of the block structure external fixator during the healing process. A novel patient-specific adjustable stiffness external fixator for mechanically stimulated tibial fracture reduction and therapy was proposed. This enables surgeons to tailor the construction of the external fixator frame to the clinical needs of each patient. The presented dismantling approach of the block structure to produce conformable stiffness provides a new clinical treatment strategy for tibial fractures.

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Comparison between External Locking Plate Fixation and Conventional External Fixation for Extraarticular Proximal Tibial Fractures: A Finite Element Analysis

10.21203/rs.3.rs-955261/v1 ◽

2021 ◽

Author(s):

Dejan Blažević ◽

Janoš Kodvanj ◽

Petra Adamović ◽

Dinko Vidović ◽

Zlatko Trobonjača ◽

...

Keyword(s):

Finite Element ◽

External Fixation ◽

External Fixator ◽

Tibial Fracture ◽

Locking Plate ◽

Plate Fixation ◽

Tibial Fractures ◽

Proximal Tibial Fracture ◽

Locking Plate Fixation ◽

Maximum Stiffness

Abstract BackgroundGood clinical outcomes for locking plates as an external fixator to treat tibial fractures have been reported. However, external locking plate fixation is still generally rarely performed. This study aimed to compare the stability of external locking plate fixator with that of conventional external fixator for extraarticular proximal tibial fractures, using finite element analysis. MethodsThree models were constructed: (1) external locking plating of proximal tibial fracture with lateral proximal tibial locking plate and 5-mm screws (ELP), (2) conventional external fixation of proximal tibial fracture with an 11-mm rod and 5-mm Schanz screws (EF-11), and (3) conventional external fixation of proximal tibial fracture with a 7-mm rod and 5-mm Schanz screws (EF-7). The stress distribution, displacement at the fracture gap, and stiffness of the three finite element models at 30-, 40-, 50-, and 60-mm plate–rod offset from the lateral surface of the lateral condyle of the tibia were determined. ResultsThe conventional external fixator showed higher stiffness than did the external locking plate fixator. In all models, the stiffness decreased as the distance of the plate–rod from the bone surface increased. The maximum stiffness was 121.06 N/mm in the EF-11 model with 30-mm tibia–rod offset. In the EF-7 model group, the maximum stiffness was 40.00 N/mm in the model with 30-mm tibia–rod offset. In the ELP model group, the maximum stiffness was 35.79 N/mm in the model with 30-mm tibia–plate offsetConclusionsExternal locking plate fixation is more flexible than conventional external fixation, which can influence secondary bone healing. External locking plate fixation requires the placement of the plate as close as possible to the skin, which allow low-profile design, because the increased distance of the plate from bone can be too flexible for bone healing.

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Optimization of a Patient-Specific External Fixation Device for Lower Limb Injuries

Polymers ◽

10.3390/polym13162661 ◽

2021 ◽

Vol 13 (16) ◽

pp. 2661

Author(s):

Mohammed S. Alqahtani ◽

Abdulsalam Abdulaziz Al-Tamimi ◽

Mohamed H. Hassan ◽

Fengyuan Liu ◽

Paulo Bartolo

Keyword(s):

Topology Optimization ◽

External Fixation ◽

Polylactic Acid ◽

External Fixator ◽

Bone Fractures ◽

Healing Process ◽

Patient Specific ◽

External Fixators ◽

Fixation Devices ◽

Limb Injuries

The use of external fixation devices is considered a valuable approach for the treatment of bone fractures, providing proper alignment to fractured fragments and maintaining fracture stability during the healing process. The need for external fixation devices has increased due to an aging population and increased trauma incidents. The design and fabrication of external fixations are major challenges since the shape and size of the defect vary, as well as the geometry of the human limb. This requires fully personalized external fixators to improve its fit and functionality. This paper presents a methodology to design personalized lightweight external fixator devices for additive manufacturing. This methodology comprises data acquisition, Computer tomography (CT) imaging analysis and processing, Computer Aided Design (CAD) modelling and two methods (imposed predefined patterns and topology optimization) to reduce the weight of the device. Finite element analysis with full factorial design of experiments were used to determine the optimal combination of designs (topology optimization and predefined patterns), materials (polylactic acid, acrylonitrile butadiene styrene, and polyamide) and thickness (3, 4, 5 and 6 mm) to maximize the strength and stiffness of the fixator, while minimizing its weight. The optimal parameters were found to correspond to an external fixator device optimized by topology optimization, made in polylactic acid with 4 mm thickness.

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Design, Dynamics Analysis, and Real-Time Stiffness Control of a Variable Stiffness Joint

Electronics ◽

10.3390/electronics9060973 ◽

2020 ◽

Vol 9 (6) ◽

pp. 973

Author(s):

Yang Yu ◽

Shimin Wei ◽

Qiunan Ji ◽

Zheng Yang

Keyword(s):

Real Time ◽

Elastic Deformation ◽

Simulation Analysis ◽

Mechanical Design ◽

Dynamic Stiffness ◽

Variable Stiffness ◽

Dynamical Model ◽

Adjustment Process ◽

Stiffness Control ◽

Stiffness Adjustment

This paper proposes a variable stiffness joint based on a symmetrical crank slider mechanism (SCM-VSJ). Firstly, the mechanical design and the working principle of the variable stiffness joint is described, and its stiffness regulation characteristics are studied. Secondly, the dynamical model of variable stiffness joint including joint motor, harmonic reducer and stiffness adjustment motor is established, in addition, the transmission mechanism of the crank slider mechanism and the elastic deformation of the spring bar are considered in the dynamic modeling. Finally, in order to control the dynamic stiffness of the variable stiffness joint in real time, a kind of improved PID (proportional-integral-derivative) control algorithm based on feed-forward and feedback closed-loop is proposed on the basis of the existing dynamical model, and the simulation analysis of real-time tracking control of dynamic stiffness for sinusoidal wave expected stiffness signal and random expected stiffness signal is carried out respectively. The research shows that the real-time stiffness control of SCM-VSJ can be realized effectively, and during the stiffness adjustment process, the output torque of the stiffness adjustment motor will be affected by the elastic deformation of the spring bar.

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Treatment of open tibial fracture with bone defect caused by high velocity missiles: A case report

Srpski arhiv za celokupno lekarstvo ◽

10.2298/sarh1310693g ◽

2013 ◽

Vol 141 (9-10) ◽

pp. 693-697

Author(s):

Zoran Golubovic ◽

Zoran Vukasinovic ◽

Predrag Stojiljkovic ◽

Ivan Golubovic ◽

Aleksandar Visnjic ◽

...

Keyword(s):

Bone Defect ◽

External Fixator ◽

High Velocity ◽

Tibial Fracture ◽

Healing Process ◽

Primary Treatment ◽

Bone Transport ◽

Open Tibial Fracture ◽

Tissue Reconstruction ◽

Treatment Of Wounds

Introduction .Tibia fracture caused by high velocity missiles is mostly comminuted and followed by bone defect which makes their healing process extremely difficult and prone to numerous complications. Case Outline. A 34-year-old male was wounded at close range by a semi-automatic gun missile. He was wounded in the distal area of the left tibia and suffered a massive defect of the bone and soft tissue. After the primary treatment of the wound, the fracture was stabilized with an external fixator type Mitkovic, with convergent orientation of the pins. The wound in the medial region of the tibia was closed with the secondary stitch, whereas the wound in the lateral area was closed with the skin transplant after Thiersch. Due to massive bone defect in the area of the rifle-missile wound six months after injury, a medical team placed a reconstructive external skeletal fixator type Mitkovic and performed corticotomy in the proximal metaphyseal area of the tibia. By the method of bone transport (distractive osteogenesis), the bone defect of the tibia was replaced. After the fracture healing seven months from the secondary surgery, the fixator was removed and the patient was referred to physical therapy. Conclusion. Surgical treatment of wounds, external fixation, performing necessary debridement, adequate antibiotic treatment and soft and bone tissue reconstruction are essential in achieving good results in patients with the open tibial fracture with bone defect caused by high velocity missiles. Reconstruction of bone defect can be successfully treated by reconstructive external fixator Mitkovic.

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A new variable stiffness robot joint

Industrial Robot the international journal of robotics research and application ◽

10.1108/ir-11-2014-0422 ◽

2015 ◽

Vol 42 (4) ◽

pp. 371-378 ◽

Cited By ~ 13

Author(s):

Yong Tao ◽

Tianmiao Wang ◽

Yunqing Wang ◽

Long Guo ◽

Hegen Xiong ◽

...

Keyword(s):

Design Methodology ◽

Dynamic Stiffness ◽

Variable Stiffness ◽

System Behavior ◽

Pivot Point ◽

Content Type ◽

Wide Range ◽

Variable Stiffness Actuators ◽

Stiffness Adjustment ◽

Elastic Elements

Purpose – This study aims to propose a new variable stiffness robot joint (VSR-joint) for operating safely. More and more variable stiffness actuators are being designed and implemented because of their ability to minimize large forces due to shocks, to safely interact with the user and their ability to store and release energy in passive elastic elements. Design/methodology/approach – The design of VSR-joint is compact and integrated highly and the operating is simply. The mechanics, the principle of operation and the model of the VSR-joint are proposed. The principle of operation of VSR-joint is based on a lever arm mechanism with a continuously regulated pivot point. The VSR-joint features a highly dynamic stiffness adjustment along with a mechanically programmable system behavior. This allows an easy adaption to a big variety of tasks. Findings – Preliminary results are presented to demonstrate the fast stiffness regulation response and the wide range of stiffness achieved by the proposed VSR-joint design. Originality/value – In this paper, a new variable stiffness joint is proposed through changing the cantilever arm to change the performance of the elastic element, which is compact, small size and simple adjustment.

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Outcome of External Fixator Management of Gustilo Anderson Type III Tibial Fractures in Lagos University Teaching Hospital

European Journal of Medical and Health Sciences ◽

10.24018/ejmed.2021.3.2.796 ◽

2021 ◽

Vol 3 (2) ◽

pp. 166-170

Author(s):

Tochukwu G. Ugwuowo ◽

Balantine U. Eze ◽

Benedict A. Okechukwu

Keyword(s):

Wound Infection ◽

External Fixator ◽

Tibial Fracture ◽

Delayed Union ◽

Tibial Fractures ◽

Open Tibial Fracture ◽

Mechanism Of Injury ◽

Type Iii ◽

Associated Injury ◽

Significant Difference

Type III open tibial fracture is the commonest type of open tibia fracture. The aim of this study was to determine the outcome of Gustilo-Anderson type III open tibial fracture managed with external fixator. Patients that presented with Gustilo-Anderson type III open tibial fractures were recruited. Patients with bone pathology, prior debridement and concomitant spinal cord injury were excluded. Ethical approval and informed consent were obtained. A structured proforma was used to collect the participant’s socio-demographic data, time of injury, fracture location, interval and number of debridement, need for skin graft or flap, duration of hospital stay, outcome of treatment, complications and events at follow-up. Wound biopsy was taken and processed for microscopy, culture, and sensitivity. Delayed union was diagnosed when the fracture united between 4-6 months. Non-union was defined as a varus or valgus angulation of >5 degrees or anterior or posterior angulation of >10 degrees. Patients were followed up for 6 months. Chi square was used to determine association between categorical variables. SPSS 20 was used for analysis. Significance was p value <0.05. Of 35 patients, males were 22 (62.9%) while females were 13 (37.1%) and mean age was 38 years. Average interval between injury and presentation was 14.5 hours. Fourteen (40%) patients had type IIIA, 18 (51.4%) patients had type IIIB while 3 (8.6%) patients had type IIIC. Mean time to fixation was 59.2 hours. Wound infection, malunion, delayed union, pin loosening and compartment syndrome were found in 42.9%, 21.3%, 21.3%, 11.5% and 1.6% respectively. Infection rate was significantly positively correlated with grade of fracture (p=0.04) and time to debridement (p=0.018). A significant association between the mechanism of injury and associated injury (p=0.027) but not mechanism of injury and grade of type III fracture (p=0.292). Significant difference between the duration of hospital stays and categories of type III fractures (p = 0.026) but not associated injury (p=0.403). No significant difference in location of fracture and time of union (p=0.723). Type III fractures managed with external fixator is associated with some complications among which infection is the commonest and delay in treatment is associated with higher risk. Post-debridement microscopy and culture is a better predictor of wound infection.

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A novel combination of computer-assisted reduction technique and three dimensional printed patient-specific external fixator for treatment of tibial fractures

International Orthopaedics ◽

10.1007/s00264-015-2943-z ◽

2015 ◽

Vol 40 (4) ◽

pp. 835-841 ◽

Cited By ~ 17

Author(s):

Feng Qiao ◽

Dichen Li ◽

Zhongmin Jin ◽

Dingjun Hao ◽

Yonghua Liao ◽

...

Keyword(s):

External Fixator ◽

Three Dimensional ◽

Reduction Technique ◽

Tibial Fractures ◽

Patient Specific ◽

Computer Assisted

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Reamed intramedullary nailing versus circular frame external fixation for segmental tibial fractures (STIFF-F): a mixed methods feasibility study

Pilot and Feasibility Studies ◽

10.1186/s40814-021-00821-3 ◽

2021 ◽

Vol 7 (1) ◽

Author(s):

Caroline B. Hing ◽

Elizabeth Tutton ◽

Toby O. Smith ◽

Molly Glaze ◽

Jamie R. Stokes ◽

...

Keyword(s):

Mixed Methods ◽

External Fixation ◽

Intramedullary Nailing ◽

Feasibility Study ◽

Online Survey ◽

Tibial Fracture ◽

Tibial Fractures ◽

Circular Frame ◽

Pilot Rct ◽

Randomised Controlled

Abstract Background Segmental tibial fractures are fractures in two or more areas of the tibial diaphysis resulting in a separate intercalary segment of the bone. Surgical fixation is recommended for patients with segmental tibial fractures as non-operative treatment outcomes are poor. The most common surgical interventions are intramedullary nailing (IMN) and circular frame external fixation (CFEF), but evidence about which is better is of poor quality. An adequately powered randomised controlled trial (RCT) to determine optimum treatment is required. STIFF-F aimed to assess the feasibility of a multicentre RCT comparing IMN with CFEF for segmental tibial fracture. Methods STIFF-F was a mixed-methods feasibility study comprising a pilot RCT conducted at six UK Major Trauma Centres, qualitative interviews drawing on Phenomenology and an online survey of rehabilitation. The primary outcome was recruitment rate. Patients, 16 years and over, with a segmental tibial fracture (open or closed) deemed suitable for IMN or CFEF were eligible to participate. Randomisation was stratified by site using random permuted blocks of varying sizes. Participant or assessor blinding was not possible. Interviews were undertaken with patients about their experience of injury, treatment, recovery and participation. Staff were interviewed to identify contextual factors affecting trial processes, their experience of recruitment and the treatment pathway. An online survey was developed to understand the rehabilitation context of the treatments. Results Eleven patients were screened and three recruited to the pilot RCT. Nineteen staff and four patients participated in interviews, and 11 physiotherapists responded to the survey. This study found the following: (i) segmental tibial fractures were rarer than anticipated, (ii) the complexity of the injury, study setup times and surgeon treatment preferences impeded recruitment, (iii) recovery from a segmental tibial fracture is challenging, and rehabilitation protocols are inconsistent and (iv) despite the difficulty recruiting, staff valued this research question and strived to find a way forward. Conclusion The proposed multicentre RCT comparing IMN with CFEF is not feasible. This study highlighted the difficulty of recruiting patients to an RCT of a complex rare injury over a short time period. Trial registration The study was registered with the International Standard Randomised Controlled Trials Number Registry: ISRCTN11229660

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