Hybrid fracture fixation systems developed for orthopaedic applications: A general review

Orthopaedic implants are applied daily in our orthopaedic clinics for treatment of musculoskeletal injuries, especially for bone fracture fixation. To realise the multiple functions of orthopaedic implants, hybrid system that contains several different materials or parts have also been designed for application, such as prosthesis for total hip arthroplasty. Fixation of osteoporotic fracture is challenging as the current metal implants made of stainless steel or titanium that are rather rigid and bioinert, which are not favourable for enhancing fracture healing and subsequent remodelling. Magnesium (Mg) and its alloys are reported to possess good biocompatibility, biodegradability and osteopromotive effects during its in vivo degradation and now tested as a new generation of degradable metallic biomaterials. Several recent clinical studies reported the Mg-based screws for bone fixation, although the history of testing Mg as fixation implant was documented more than 100 years ago. Truthfully, Mg has its limitations as fixation implant, especially when applied at load-bearing sites because of rather rapid degradation. Currently developed Mg-based implants have only been designed for application at less or non-loading-bearing skeletal site(s). Therefore, after years research and development, the authors propose an innovative hybrid fixation system with parts composed of Mg and titanium or stainless steel to maximise the biological benefits of Mg; titanium or stainless steel in this hybrid system can provide enough mechanical support for fractures at load-bearing site(s) while Mg promotes the fracture healing through novel mechanisms during its degradation, especially in patients with osteoporosis and other metabolic disorders that are unfavourable conditions for fracture healing. This hybrid fixation strategy is designed to effectively enhance the osteoporotic fracture healing and may potentially also reduce the refracture rate. The translational potential of this article: This article systemically reviewed the combination utility of different metallic implants in orthopaedic applications. It will do great contribution to the further development of internal orthopaedic implants for fracture fixation. Meanwhile, it also introduced a titanium-magnesium hybrid fixation system as an alternative fixation strategy, especially for osteoporotic patients.

Open-Design Collar vs. Conventional Philadelphia Collar Regarding User Satisfaction and Cervical Range of Motion in Asymptomatic Adults

OBJECTIVE

The current study aimed to compare the Philadelphia collar and an open-design cervical collar with regard to user satisfaction and cervical range of motion in asymptomatic adults.

DESIGN

Seventy-two healthy subjects (36 women, 36 men) aged 18 to 29 yrs were recruited for this study. Neck movements, including active flexion, extension, right/left lateral flexion, and right/left axial rotation, were assessed in each subject under three conditions--without wearing a collar and while wearing two different cervical collars--using a dual digital inclinometer. Subject satisfaction was assessed using a five-item self-administered questionnaire.

RESULTS

Both Philadelphia and open-design collars significantly reduced cervical motions (P < 0.05). Compared with the Philadelphia collar, the open-design collar more greatly reduced cervical motions in three planes and the differences were statistically significant except for limiting flexion. Satisfaction scores for Philadelphia and open-design collars were 15.89 (3.87) and 19.94 (3.11), respectively.

CONCLUSION

Based on the data of the 72 subjects presented in this study, the open-design collar adequately immobilized the cervical spine as a semirigid collar and was considered cosmetically acceptable, at least for subjects aged younger than 30 yrs.

Numerical modelling and experimental investigation of drug release from layered silicone matrix systems

Medical devices and polymeric matrix systems that release drugs or other bioactive compounds are of interest for a variety of applications. The release of the drug can be dependent on a number of factors such as the solubility, diffusivity, dissolution rate and distribution of the solid drug in the matrix. Achieving the goal of an optimal release profile can be challenging when relying solely on traditional experimental work. Accurate modelling complementing experimentation is therefore desirable. Numerical modelling is increasingly becoming an integral part of research and development due to the significant advances in computer simulation technology. This work focuses on numerical modelling and investigation of multi-layered silicone matrix systems. A numerical model that can be used to model multi-layered systems was constructed and validated by comparison with experimental data. The model could account for the limited dissolution rate and effect of the drug distribution on the release profiles. Parametric study showed how different factors affect the characteristics of drug release. Multi-layered medical silicone matrices were prepared in special moulds, where the quantity of drug in each layer could be varied, and release was investigated with Franz-diffusion cell setup. Data for long-term release was fitted to the model and the full depletion of the system predicted. The numerical model constructed for this study, whose input parameters are the diffusion, effective dissolution rate and dimensional solubility coefficients, does not require any type of steady-state approximation. These results indicate that numerical model can be used as a design tool for development of controlled release systems such as drug-loaded medical devices.

Part 2: Devices of the Head, Neck, Spine, Chest, and Abdomen

This gallery of medical devices illustrates a multitude of common devices in the head, neck, spine, chest, and abdomen that are found in daily radiologic practice (orthopedic devices for the extremities and pelvis were illustrated in Part 1). All these medical devices have been more thoroughly discussed in the previous articles in this medical devices series and in other detailed references. The present article is a comprehensive overview of these devices and provides a quick reference for identifying an unfamiliar device. It is intended to allow the reader to identify a device generically and to understand its purpose. It is important to recognize the presence of a device, understand its purpose and proper function, and recognize the complications associated with its use. Knowing the specific or proper brand name of every device is not important and frequently not possible. New devices are constantly being introduced, although most of them are variations of a previous device. Sometimes, so many devices are used in a patient's treatment that they obscure important anatomy and pathologic conditions (Fig 1). Herein, we present an overview of the many medical devices frequently used in the head, neck, and spine, including a halo device, aneurysm clips, spinal fusion devices, deep brain electrodes, sacral nerve stimulator, and vertebroplasty (Figs 2-9). We also illustrate numerous chest medical devices that are seen daily by almost all radiologists. These devices include a multitude of extrathoracic and intrathoracic apparatus, ranging from intravenous catheters to oxygen tubing and electrocardiographic leads, central venous catheters, chest tubes, endotracheal and feeding tubes, cardiac valves, coronary artery bypass stents, pacemakers, internal cardiac defibrillators, ventricular assist devices, and total artificial hearts (the latter two devices are frequently encountered in many large medical centers) (Figs 10-26). We also present medical devices of the abdomen and pelvis, which can be grouped into four major categories: intestinal tubes, genitourinary apparatus, postoperative apparatus, and vascular devices (Figs 27-47). For a detailed discussion of a particular device, the reader should refer to the appropriate references cited.

Rings and things on upper extremity radiographs of emergency patients

Rings, intravenous lines, and other objects on the injured upper extremities of trauma patients are frequently overlooked by radiology and emergency department (ED) personnel. This can impair proper radiologic evaluation of the injured extremity as well as negatively affect the quality of the patient's treatment. A 1-week sample of radiographs of injured upper extremities from the ED of University Medical Center (UMC), Tucson, Arizona, showed that 20% of the studies (19 of 95) contained at least one object on the injured upper extremity, but only one radiology report (1.1%) mentioned such an object. A review of 2489 upper extremity ED radiology reports from January to June 2002 showed only 47 reports (1.9%) that mentioned the presence of an overlying object. It is important to educate radiology department and ED personnel to remove upper extremity jewelry and place necessary medical devices on noninjured extremities.

Medical Devices of the Head, Neck, and Spine

There are many medical devices used for head, neck, and spinal diseases and injuries, and new devices are constantly being introduced. Many of the newest devices are variations on a previous theme. Knowing the specific name of a device is not important. It is important to recognize the presence of a device and to have an understanding of its function as well as to be able to recognize the complications associated with its use. The article discusses the most common and important devices of the head, neck, and spine, including cerebrospinal fluid shunts and the Codman Hakim programmable valve; subdural drainage catheters, subdural electrodes, intracranial electrodes, deep brain stimulators, and cerebellar electrodes; coils, balloons, adhesives, particles, and aneurysm clips; radiation therapy catheters, intracranial balloons for drug installation, and carmustine wafers; hearing aids, cochlear implants, and ossicular reconstruction prostheses; orbital prostheses, intraocular silicone oil, and lacrimal duct stents; anterior and posterior cervical plates, posterior cervical spine wiring, odontoid fracture fixation devices, cervical collars and halo vests; thoracic and lumbar spine implants, anterior and posterior instrumentation for the thoracic and lumbar spine, vertebroplasty, and artificial disks; spinal column stimulators, bone stimulators, intrathecal drug delivery pumps, and sacral stimulators; dental and facial implant devices; gastric and tracheal tubes; vagus nerve stimulators; lumboperitoneal shunts; and temperature- and oxygen-sensing probes.

Fracture Fixation

The basic goal of fracture fixation is to stabilize the fractured bone, to enable fast healing of the injured bone, and to return early mobility and full function of the injured extremity. Fractures can be treated conservatively or with external and internal fixation. Conservative fracture treatment consists of closed reduction to restore the bone alignment. Subsequent stabilization is then achieved with traction or external splinting by slings, splints, or casts. Braces are used to limit range of motion of a joint. External fixators provide fracture fixation based on the principle of splinting. There are three basic types of external fixators: standard uniplanar fixator, ring fixator, and hybrid fixator. The numerous devices used for internal fixation are roughly divided into a few major categories: wires, pins and screws, plates, and intramedullary nails or rods. Staples and clamps are also used occasionally for osteotomy or fracture fixation. Autogenous bone grafts, allografts, and bone graft substitutes are frequently used for the treatment of bone defects of various causes. For infected fractures as well as for treatment of bone infections, antibiotic beads are frequently used.

Joint arthroplasties and prostheses

Joint arthroplasty is the most frequently performed orthopedic procedure after fracture fixation. The major indications for any joint replacement are degenerative joint disease, inflammatory arthropathy, avascular necrosis, and complicated fractures. The major contraindications for any joint arthroplasty are systemic and joint infection and a neuropathic joint. The interpretation of radiographs in cases of joint arthroplasty is a significant part of many radiology practices, and correct recognition of the prosthetic devices and their complications by the radiologist is important. The article reviews the most common types of joint arthroplasties and prostheses of the upper and lower extremities and discusses the most frequent complications associated with their placement.