1.6 Equipment
Operating room table Sari Cohen
Image intensifier Poh Yan Lim, Merng Koon Wong
Pneumatic tourniquet Poh Yan Lim, Merng Koon Wong
Air and power supply Poh Yan Lim, Siew Hong Lau, Donna Russell-Larson
Authors Sari Cohen, Poh Yan Lim, Merng Koon Wong, Siew Hong Lau, Donna Russell-Larson
1.6 Equipment
1.6.1 Operating room table Sari Cohen
1.6.1.1 Introduction
Proper patient positioning is essential to allow surgery to proceed in a correct, safe, and successful manner. The goals of correct patient positioning include providing optimum exposure and access to the surgical site, maintaining body alignment, supporting cardiovascular and respiratory function, protecting neuromuscular and skin integrity, and allowing the anesthetist access to the airway, intravenous sites, and anesthetic support devices. Insufficient care in transferring and positioning a patient can have a damaging effect on them.
The operating room personnel (ORP) must be knowledgeable, experienced, and trained in positioning the patient for surgery. Correct positioning requires understanding and awareness of the physiological effects and the implications and risks of positioning in relation to the patient’s general and medical condition.
Planning is necessary to ensure correct and safe positioning. Preoperative assessment includes both patient and intraoperative factors. Patient factors include age, height, weight, skin condition, nutrition status, and physical/mobility limits. Intraoperative factors include type of anesthesia, length of surgery, position required for the operation, and the need for intraoperative imaging.
Teamwork is essential for safe and appropriate patient positioning. Although the surgeon has the final responsibility for the safety of the patient, successful patient positioning can only be achieved by cooperation and coordination of the whole surgical team. ORPs have a leading role in this aspect of patient care. Adequate number of personnel must be available to position the patient on the operating table (OT). Consideration must be given to the type of OT required (standard table, radiolucent table, fracture table, or table for spine surgery). The table must be checked to ensure that it is in good working order, and that the appropriate padding, positioning devices, and attachments are available. In the operating room, it should be positioned so as to allow access for additional equipment (eg, an image intensifier).
1.6.1.2 Operating tables
Of all surgical specialities orthopaedics is the one with the greatest variety of patient positioning. Operating tables are designed to support the patient in these positions. Because the requirements are so varied specialized orthopaedic tables have been designed.
General OTs are composed of a platform divided into major sections: the head, torso, and leg (Fig 1.6-1). Each has a corresponding removable mattress pad. The area between each section is called a break; each section can be angled relatively to its adjacent section—this is called breaking the table. The torso section is attached to the base of the OT.
Along the edges of each section of a general table run flat metal side rails with a gap at each break. These allow attachment of accessories, such as arm boards, hand tables, and overhead arm supports to be fitted to the table, either directly or using clamps that are fastened onto the rails.
The table height can be raised or lowered, and the table top tilted laterally or tipped head down (Trendelenburg position) or head up positions. Modern OTs are generally electrically or battery operated with a manual mechanical backup, although older manual tables are used in many countries. They have roller wheels which allow them to be moved and a brake that locks them in place. In newer models, the entire table platform is radiopaque to accommodate the use of intraoperative fluoroscopy.
Most types of surgery can be performed on an unmodified standard OT, including lower limb surgery. The attachment of a hand table facilitates hand surgery.
Shoulder surgery can be performed by applying a back plate attachment and head support. The knee-chest position for lumbar laminectomy or discectomy can be achieved by attaching a vertical extension platform onto the end of the foot section of the standard OT. An extension may also be needed for tall patients.
Special orthopaedic OTs are designed for specific operations. The fracture table allows access for an image intensifier. AP and lateral views of the proximal femur can be obtained when performing hip fracture surgery and closed femoral nailing (Fig 1.6-2). The unaffected leg is raised and supported in a padded leg rest, while traction can be applied to the affected leg either indirectly by placing it in a boot, or for a stronger pull by placing a Steinmann pin through the distal femur.
Modular base table technology comprises a permanent table base which accepts standard, orthopaedic trauma, Jackson spinal, maximum access, and imaging table tops. The tops can be switched depending on the type of surgery. Modular base table tops are generally made of a radiolucent composite material that allows unrestricted image intensifier use.
1.6.1.3 Parts and accessories
Each OT is designed with parts and accessory devices that can accommodate most surgical positioning needs (Fig 1.6-3).
These accessories are used to achieve the optimal, safe, and adequate positioning of the patient for surgery. Accessories required depend on the OT type, the preference of the surgeon, and the patient’s weight and size. They include padding and pressure-relieving devices, such as durable mattress and gel products. These are used as an overlay to the mattresses, and positioning devices are used to fix the patient in a stable position. They minimalize pressure effects on soft tissues by distributing pressure evenly and thus decrease the potential for injury (Fig 1.6-4).
Accessories for OTs from different manufacturers are often not compatible with each other. This must be considered when scheduling surgery if the OR has tables manufactured by different companies.
When positioning a patient note that different individuals have different anatomical and physical limitations. This particularly applies to the elderly in whom the joints may be stiffer and the bones osteoporotic. Rough handling of such patients when administering anesthesia or during positioning can lead to fractures or joint dislocations. All ORP must be familiar with the proper function and use of the positioning equipment and accessories required to maintain the safety of each patient.
Selection criteria for positioning devices and accessories are based on:
Position needed for surgery
Availability of appropriate sizes and shapes
Durability of material and design
Ability to maintain normal capillary interface pressure
Resistance to moisture and microorganisms
Radiolucency
Fire resistance
Water resistance
Nonallergenic to the patient
Ease of use
Ease of cleaning/disinfection, if not disposable
Ease of storage, handling, and replacement
Cost-effectiveness
Conclusion
Every orthopaedic OT should be of appropriate design and have suitable positioning devices and accessories available. These are used for positioning the patient for surgery, allowing maximum safe anatomical exposure of the surgical site. Equipment function should be verified before every use and must be maintained and used according to the manufacturer’s instructions.
Before a patient enters the OR the position required must be known and the proper OT prepared and be in good working order. Any positioning accessories or table attachments that might be needed must be available.
Special orthopaedic OT components are often used several times daily. All accessories belonging to the OT need to be stored carefully to prevent any damage or loss. This is best done in a designated area close to the orthopaedic rooms.
Properly functioning equipment, used correctly, will achieve safe positioning of the patient and good exposure of the surgical site.
1.6.1.4 Further reading
AORN Standards, Recommended Practices, and Guidelines (2003) Recommended practice for positioning the patient in perioperative practice setting. AORN; 341–346.
Corbett S (2006) Patient positioning for spine surgery. Introduction to Spine Surgery. Stuttgart New York: Thieme; 203–213.
Heizenroth PA (2003) Positioning the Patient for Surgery: Alexander’s Care of the Patient in Surgery. Philadelphia, Amsterdam: Elsevier, 159–185.
Ozcan MS, Praetel C, Bhatti MT, et al (2004) The effect of body inclination during prone positioning on intraocular pressure in awake volunteers: a comparison of two operating tables. Anesth Analg; 99:1152–1158.
Lee FY, Chapman CB (2003) In situ pinning of hip for stable slipped capital femoral epiphysis on a radiolucent operating table. J Pediatr Orthop; 23(1):27–29.
Randall KR, Harding WG 3rd (2002) A safe, easy, and inexpensive technique for patient positioning in shoulder surgery. J Arthros Relat Surg; 18(7):812–814.
1.6.2 Image intensifier Poh Yan Lim, Merng Koon Wong
The discovery of x-rays had a profound impact on the diagnosis and management of fractures. The subsequent development, introduction, and improvement of image intensifier technology has had an equally profound impact on trauma surgery as it allows immediate verification of fracture reduction and accurate positioning of orthopaedic implants on bone. However, as with any medical equipment, the benefits, risks, and limitations must be thoroughly weighed and balanced.
Ionizing radiation
Ionizing radiation is electromagnetic or particulate radiation capable of producing ions, directly or indirectly, in its passage through tissue. It alters atoms by removing one or more electrons, leaving positively charged particles known as free radicals. These free radicals may cause changes in DNA causing it to mutate and this can set off the development of malignancies. The amount of damage done by ionizing radiation depends on the dose received.
Alpha and beta particles, gamma rays, and x-rays are all forms of ionizing radiation. X-rays and gamma rays are forms of short wavelength electromagnetic radiation.
Diagnostic imaging
There are three primary components in an x-ray imaging system, ie, an x-ray source, the object to be x-rayed, and a system for detecting and displaying the resultant image.
The x-ray source produces x-rays using high-voltage electricity in a vacuum. The operator is able to focus the beam in a process called collimation. The smaller the area focused, the sharper the x-ray image and the smaller the dose. Collimation is exactly the same process as the setting of the aperture on a conventional camera (Fig 1.6-5). The operator is also able to select predetermined settings of an x-ray exposure dose and to initiate the exposure.
The x-rays produced penetrate the body which absorbs, refracts, or reflects the x-ray beam energy depending on the tissue. Bone will reflect and absorb most x-rays while soft tissue will allow penetration. It is this differential of x-ray penetration which results in being able to visualize human bone and joint anatomy using x-rays.
When x-rays reach the target-imaging plate and are absorbed, they cause certain substances on the imaging plate to fluoresce; thus emitting photons of lower energy. This is how x-rays can produce an image on a photosensitive film which can then be made visible by developing it. Alternatively, an x-ray sensitive cartridge is used which is developed to produce an electronic version of the image which is downloaded onto a computer network. An image intensifier captures this fluorescence in real time, transmitting it to a screen. X-ray dose is measured using the “Gray scale” (Gy), an international unit of absorbed dose.
The image intensifier has three main parts—the x-ray tube, the image intensifier collector, and the display screen (Fig 1.6-6). Note that x-rays come from the tube and are fired toward the collector.
For good-quality images the beam of the x-ray should travel perpendicular to the limb/bone with the image intensifier receptor as close to the patient as possible. The source-to-patient distance must be at least 38 cm for image-intensified fluoroscopic units.
Hazards of radiation exposure
Everyone is subjected to background radiation and most is derived from cosmic rays. Some comes from the earth itself and small amounts from medical and other artificial sources. These background levels are always present and pose little hazard.
Radiation sources are found in a wide range of occupational settings. If radiation is not properly controlled, it can be potentially hazardous to the workers’ health and can lead to development of cancer in sensitive organs, particularly in the thyroid and in bone marrow. The developing fetus is particularly at risk and exposure should be minimized in pregnancy. Exposure to x-rays is cumulative; thus, long periods between doses do not lessen the risks.
1.6.2.1 Radiation safety
Although modern x-rays have minimal radiation effects on the patient, frequent, prolonged, and repetitive use of intraoperative image intensification have greatly increased the risk of significant radiation exposure to the surgical teams. It is the responsibility of every surgeon to be familiar with the image intensifier and to know how to minimize radiation exposure to himself/herself, the patient, and other members of the surgical team. Image intensifier machines which are able to store and then show the images taken have the effect of greatly reducing the radiation dose to which the patient and the surgical teams are exposed.
The system of radiation protection recommended by the International Commission on Radiological Protection (ICRP) in Publication 60 is based on three major principles:
Justification of practice
A practice which involves exposures or potential exposures should only be adopted if it is likely to produce sufficient benefit to the individual or society to outweigh the detriment or harm to health.
Optimization of protection—ALARA principle
Individual doses, the number of people exposed, and the likelihood and magnitude of potential exposures should be kept As Low As Reasonably Achievable (ALARA), economic and social factors being taken into consideration.
Individual dose and risk limits
The ICRP recommends that exposure of individuals should be subjected to dose limits, aimed at ensuring that no individual is exposed to unacceptable risks. Certain harmful effects of radiation, such as cataract formation, are dependent on dose. Patients and staff exposed to radiation below a certain dose (threshold dose) are not at risk of developing this complication. These effects are called deterministic. Other harmful effects of radiation do not have a threshold dose. The adverse effects which can include cancers are related to the absorbed dose but any exposure can potentially be harmful. These effects are called stochastic. The aim is to prevent any deterministic effects and minimizing the chance of stochastic effects (Tab 1.6-1).
The most important principle of radiation protection is to keep all doses As Low As Reasonably Achievable while still allowing the beneficial use of ionizing radiation. The recommendations of the ICRP can be applied at several levels to control the hazards from radiation.
Regulatory requirements
The ICRP and many national regulatory agencies worldwide adopt a conservative stance with regard to radiation protection in radiology and medicine. The reason is that evidence surrounding low-dose radiation and its resulting risks is inconclusive.
The formulation and implementation of regulations and legislation varies from country to country. Regulations provide a link between the ICRP recommendations and their implementation in the workplace. The regulations define a satisfactory standard of protection and apply to all justified practices.
Management requirements
Management has the important role of implementing system safeguards for quality control and safety. It should also take potential exposures into account and institute risk analysis to identify possible causes of incidents and limit the probability and effect of such incidents. Regular quality control tests should be done to detect deterioration in equipment performance to minimize undue patient and staff radiation exposure.
One of the main responsibilities of this management is to encourage a good attitude to safety and recognition that safety is a personal responsibility. In addition, the management should optimize protection by clearly defining responsibilities and providing clear and simple operating instructions.
Monitoring
Absorbed dose by staff members needs to be monitored by means of thermoluminescent dosimeters (TLDs) and personal pocket dosimeters. TLDs are able to record total exposure, while pocket dosimeters are used to immediately determine radiation exposure. They are to be worn at the waist level and are the most accurate form of monitoring workers’ exposure to radiation.
Foundation for a safety program
Absorbed dose is related to duration, distance, and shielding. The three major techniques to maintain the ALARA principles are reducing duration of exposure, increasing the distance to the source of exposure, and shielding.
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