Amirhossein Goharian

Biomechanical and bioactivity concepts of polyetheretherketone composites for use in orthopedic implants : a review

The use of polyetheretherketone (PEEK) composites in the trauma plating system, total replacement implants, and tissue scaffolds has found great interest among researchers. In recent years (2008 afterward), this type of composites has been examined for suitability as substitute material over stainless steel, titanium alloys, ultra high molecular weight polyethylene, or even biodegradable materials in orthopedic implant applications. Biomechanical and bioactivity concepts were contemplated for the development of PEEK orthopedic implants and a few primary clinical studies reported the clinical outcomes of PEEK-based orthopedic implants. This study aims to review and discuss the recent concepts and contribute further concepts in terms of biomechanical and bioactivity challenges for the development of PEEK and PEEK composites in orthopedic implants.

Bioinert Metals (Stainless Steel, Titanium, Cobalt Chromium)

Stainless steel and titanium alloys are commercially used in trauma plates and screws. Stainless steel implants are being developed for corrosion resistance and biocompatibility for long-term implantation in the human body environment. Likewise, the reduction of Young’s modulus to diminish the stress shielding effects of titanium alloys implants is being investigated to promote the quality of the bone healing, particularly in osteoporotic bone fractures. In this chapter, the current challenges and methods associated with development of the stainless steel and titanium alloys materials for use in trauma plating systems (plate and screws) are reviewed and discussed. Because cobalt chromium alloys (CoCr) have been recently utilized as screws in combination with titanium plates, the associated concepts related to this material for use in trauma plating systems are also reviewed.

Development of Novel Polymer Composite Beam Using Ultrasonic Welding Process for Acetabular Cup Prosthesis

The objective of this study was to prepare a basic contributed model in beam to examine this novel composition supposed to apply for acetabular cup. Injection molding process used to manufacture of the component whereas ultrasonic welding was utilized to joint two components. Molding and welding value parameters were carried out by trial and error process. Strength bonding of two components was evaluated by single cantilever beam (SCB) test. The Interfacial fracture energy attained by single cantilever beam (SCB) test was exceeded over 1800 after 70 mm crack propagation.

11 – Forearm (Radius and Ulna) Plating Fixation

The plating fixation of forearm bones fracture is biomechanically and clinically reviewed in this chapter. First, biomechanical aspects of forearm bones and effective muscle-tendons in various positions of the forearm are briefly reviewed. After understanding forearm biomechanics, biomechanical testing methods that could be utilized for evaluation of forearm fracture fixation are explained. Then clinical-biomechanical challenges of forearm plating fixation are explored. In this regard, the associated challenges in volar and dorsal plating fixation methods, plating fixation of fracture with a fragmentary dorsal fracture, plating fixation with variable angle locking system, plating fixation of fracture with radial column fragmentary, irritation of flexor tendons in volar plating fixation, plating fixation of comminuted fractures, etc. are extensively reviewed. Furthermore, clinical considerations that are normally contemplated before, during, and after operation are then elaborated. Finally, overall biomechanical and clinical aspects of forearm plating fixation are discussed.

Bioinert Polymers (Polyetheretherketone)

Polyetheretherketone (PEEK) is a newly developed polymer with good biocompatibility characteristics. The biomechanical and biological advantages of the PEEK polymer make it a promising material for the development of composites for orthopedic implants. Some of the PEEK advantages include the similarity of mechanical properties of PEEK compared with human bone tissue; lack of electrochemical activity in vivo; excellent corrosion resistance and biocompatibility; considerable fatigue strength; wear resistance; tensile strength, compressive strength, and ductility. All these superior characteristics have motivated biomechanical and biomaterial researchers and orthopedic manufacturers to develop the PEEK polymer in combination with other fillers such as carbon fiber, hydroxyapatite, etc. to promote the mechanical and biological benefits of the PEEK polymer for use in orthopedic implants. In this chapter, the biomechanical and biological concepts that have been considered in the possible development of PEEK medical implants are reviewed and discussed. The potential usage of PEEK and its composites are then reviewed in conjunction with their biomechanical and biological benefits compared to the current metallic implants. The biomechanical challenges of using PEEK composites, particularly carbon fiber reinforced polyetheretherketone (CFRPEEK) in trauma plating systems are examined and further evaluation concepts are discussed.

Humerus Trauma Plating Fixation

Plating fixation of fractures at proximal and distal portions of humerus bone (humeral head and distal humeral) have been found biomechanically challenging due to loss of stability under physiological loading conditions. Therefore, biomechanical strength of bone-implant fixation is crucial for successful clinical outcomes. From this view, the clinical biomechanical aspects of plating fixation would be reviewed and discussed in this chapter. By understanding of the relationship between biomechanical and clinical benefits of fracture fixation, the current biomechanical evaluation methods could be discussed and further improvements could be propounded. To better understanding of influenced loading and boundary conditions on humeral fracture fixation, a short introductory of humerus bone with attached muscle-tendons is presented before exploring the biomechanical and clinical challenges.

Pelvic and Clavicle Trauma Plating Fixation

Plating fixation has been found to be an effective fixation method for treating pelvic and clavicle unstable fractures. Pelvic fractures are classified as pelvic ring and acetabular fractures, which would be unstable due to the high-energy trauma. Reconstruction plate has been developed for fixation of pelvic fractures. This type of plates could be intraoperatively bended in two axes and twisted over the longitudinal axis of the plate to be anatomically positioned on the intended aspect of the pelvic bone. Reconstruction plating of pelvic ring and acetabular fractures has been biomechanically evaluated to compare the mechanical stability of fracture fixation in different positioning of the plate. In this chapter, the biomechanical and clinical challenges of various plating positioning of the pelvic ring and acetabular fracture fixation are reviewed and discussed. In biomechanical literature, anterior and superior plating of clavicle fractures have been biomechanically compared. The results showed that the location and type of fracture (at distal third or mid-shaft clavicle bone) and type of loading conditions (bending, axial compression, clockwise torsion, or anticlockwise torsion) have an influence on the mechanical advantage of superior and anterior plating fixation. It was even observed that the method of bending testing of mid-shaft fracture fixation would influence on the achieved results. The biomechanical challenges of the clavicle fracture fixation are also reviewed and discussed in this chapter.

Biodegradable Metals (Biodegradable Magnesium Alloys)

In this chapter, the recent developments of biodegradable magnesium alloys are reviewed. These materials are promising for use in trauma plating fixation. The main challenge of magnesium alloy is the biodegradation rate of the material in human body fluid. Recently, various methods have been utilized to promote the corrosion resistance of magnesium alloys in an in vivo environment. However, it is still controversial among the researchers how the degradation rate of magnesium alloy could be reduced to obtain sufficient mechanical stability of fracture fixation in treatment of trauma injuries. Due to fast degradation of magnesium alloy it will be very challenging to reduce the degradation rate. Methods developed for reduction of the magnesium degradation rate could affect biocompatibility, cytocompatibility, and mechanical strength of the magnesium alloy implant in vivo environment. The challenges and promising aspects of magnesium alloys are reviewed and discussed in this chapter. In Chapter 16, Further Development of Trauma Plating Fixation, the possible exploration of magnesium alloys for use in trauma plating fixation is presented.

Tibia and Fibula Trauma Plating Fixation

Fixation of tibia bone fractures is quite convenient in terms of surgical procedure, but it can be challenging to find a suitable fixation method based on the fracture pattern; soft tissue considerations; whether it is an open or close fracture; and expected clinical outcomes. Body weight bearing of tibia fracture fixation in conjunction with range of motion at knee and ankle joints would affect preservation of the primary reduction from which fracture union is challenged. In this regard, the extents of body weight bearing and range of motion at various stages of fracture healing (hematoma, primary callus formation, secondary callus formation, bone mineralization, and consolidation) are vital to obtain successful clinical outcomes. Tibia fractures might occur due to high trauma energy from falling or accidents that compromise skin and soft tissues. It is crucial to consider treatment and preservation of the injured soft tissues during implantation of a trauma locking plate to prevent delayed union, malunion, nonunion, and infection complications. Plating of tibia fractures could be more challenging at proximal and distal zones. Various trauma plates with specific intended uses were developed to be placed on the intended aspect of tibia bone to buttress the fracture site while capturing the bone fragments in a multifragmentary fracture pattern. In this chapter, these concepts along with other biomechanical and clinical concepts of tibia bone fracture fixation are reviewed and discussed.

Hand and Foot Trauma Plating Fixation

Fixation of hand and foot bone fractures is increasingly managed by plating systems. Progress in machining processes allows fabricating mini plates and screws to be implanted into the hand and foot bones to enhance open reduction and internal fracture fixation. Plating fixation has promoted fusion of bones at the joints of foot bones so that even severe fracture fragmentary fractures at the joints could be effectively treated. Higher stabilization of fracture fixation in the treatment of foot bone fractures has been reported in recent biomechanical researches, which allows further development of plating systems. The advantages of plating and transarticular screw fixations in treatment of unstable fractures at tarsometatarsal (TMT) and metatarsophalangeal (MTP) joints individually or in combination is of great interest to biomechanical-clinical researchers. Interestingly, the concept of using shape memory alloy implants with high elastic property was introduced most recently in the literature as a promising solution to enhance the contact force of bones for better joint fusion in arthrodesis treatment of severe unstable fractures or bone deformity. These concepts along with other biomechanical and clinical aspects of using trauma plating fixation for hand and foot bone fractures are reviewed in this chapter and recent developments are highlighted and discussed accordingly.