Holding power of threaded external skeletal fixation pins in the near and far cortices of cadaveric canine tibiae.

We compared the pin-bone interfaces at the near and far cortical penetration sites of positive-profile end-threaded external fixation pins in cadaveric canine tibiae. The holding power of the pins in each cortical surface was independently measured in 21 pin-bone sections. Scanning electron microscopy (SEM) was used to compare subjectively the microstructural appearance of the pin-bone interfaces at the near and far cortical penetration sites in eight pin-bone sections. The far cortical penetration site provided greater holding power than did the near cortical site. SEM evaluation suggested more bony microfractures and debris with less pin-bone SEM evaluation suggested more bony microfractures and debris with less pin-bone interlock in the near cortical penetration sites than in the corresponding far cortical penetration sites. This study showed that after low-speed power insertion of positive-profile end-threaded pins in canine cadaveric tibiae, the near cortical penetration site contributes approximately 25% less to the overall holding power of the pin than does the far cortical penetration site.

Device-related litigation & clinical engineering.

The investigation of patient-related incidents often must include consideration of the role of the associated medical devices. In addition to being good practice from quality review perspectives, federally mandated MDR requirements generally need to include clinical engineering input. Medical devices also play a significant role in patient litigation aimed at medical providers, hospitals and device manufacturers. Clinical engineering has an important role to play in supporting and tracking litigation as it relates to medical equipment. This role requires an understanding of the litigation process and active participation as a claim progresses. It also should include careful evaluation of the assertions and defenses raised by the various parties both during and at the conclusion of litigation.

Pressure wave fidelity in catheter introducers.

Pressure waveform fidelity was examined in two sizes of the Bard catheter introducer. The purpose of this endeavor was to determine whether accurate blood pressure measurements could be achieved directly via the catheter introducers. The introducers were incorporated into a mock circulatory system for the study. The effects of supporting dilators and catheters within the introducer sheath during pressure measurements were also considered. Parameters used to explain pressure waveform response within the catheter introducers included the damping coefficient and the natural frequency of the catheter introducer, and the effects of impedance mismatching between the transducer and the mock circulatory system. Overall, the pressure measurements obtained from the catheter introducer were distorted. Mean pressure levels measured in the introducers were up to 15 mmHg higher than the true mean pressure. The distortion in the pressure measurements can be attributed for the most part to impedance mismatching. In sum, the pressure measurements obtained from catheter introducer-manometer systems should be used only referentially, and not as an absolute standard.

Principles of bone healing and biomechanics of external skeletal fixation.

External skeletal fixation is being used to treat an increasing number of orthopedic conditions in veterinary medicine. Study of the variables affecting the biomechanics of external fixation and bone healing is vital if patient morbidity is to be minimized. These are reviewed and incorporated into strategies that can be applied to decision making using external fixation in the clinical setting.

Information sources for medical equipment risk management.

An effective risk management program must include specific consideration of medical equipment, and must address hazard identification, incident prevention, and the coordination of efforts to minimize losses when incidents do occur. The hazard identification and prevention components require an organized effort to utilize external and internal information sources to determine both generic and device-specific hazards, recalls, alerts and related data. Equally important is the effective processing of this information so that it is integrated into the routine activity of the hospital. Attention to these information sources can contribute to the broad clinical engineering goal of helping to assure the safe and effective use of medical equipment throughout the hospital.

Legal liability in the development and use of medical expert systems.

The application of medical expert systems is likely in some instances to result in patient injury litigation. Such legal action will be based on the same principles now applicable to medical practice and products liability. These principles define legally wrongful acts, product defects, and theories of recovery: negligence, breach of warranty and strict liability. The resolution of such litigation will depend on whether the clinician should have relied on the advice of the expert system when the advice and patient treatment is alleged to have been wrong, as well as the overall quality of the expert system, its functional design, and claims made for it. Clinical engineers who become involved with expert system development, selection or implementation should understand the risk management implications of this technology.

Regulatory and other public policy issues.

Regulatory and other public policy issues in the future of biomedical engineering, as they relate to the development and use of medical devices, are discussed. At the federal level, agencies that directly influence the application of medical technology include the Food and Drug Administration (FDA), with its clinical trials and premarket and regulatory authority, and the Health Care Financing Administration (HCFA), with its reimbursement policy. The Occupational Safety and Health Administration (OSHA), the Environmental Protection Agency (EPA), and the Department of Commerce can have a considerable impact on corporate profitability, which is a driving force for most new technology and new product introductions. Another area of public policy that has been cited as significantly influencing health care and medical device development, namely, civil litigation, is also considered. To illustrate the issues, the impact of the regulatory environment on the application of computer software to a wide variety of medical products is examined. The humanistic and ethical problems brought about by technological advances are discussed. Ten key technologies that are likely to have the greatest importance in the next few years and ten external influences on the future of the medical device technology industry that have been identified by the Health Industry Manufacturers Association are described.

Risks associated with diagnostic devices.

Therapeutic medical devices alter patients' physiological functions. Diagnostic devices are for information gathering, manipulation, and display. Despite this difference in purpose, both types of medical equipment have potential risks associated with their use that must be recognized and subjected to the principles of risk management. For diagnostic equipment, special concerns include direct side effects, clinical misinterpretation of results, malperformance, obvious non-function, and inherent limitations. The role of clinical engineering in diagnostic risk management must be consistent with its general obligations in equipment acquisition, training, maintenance, and hazard identification. Since sharp lines of distinction often cannot be drawn between equipment, operator, and clinical issues, clinical engineering has the opportunity and responsibility to extend its contributions into an integrated systems approach to medical device safety and effectiveness.

Design of medical device alarm systems.

Medical device alarms are intended to enhance safety by augmenting the operator's ability to monitor an array of system and patient variables. To this end, alarm design must consider both technical and human requirements. Technical factors include selection of variables, limit-setting techniques, alarm reliability, and alarm output system. Human factors include the types of controls, displays, and instructional materials that assist the users in effective use of the machine. The designer and the user of medical devices must recognize that alarms can at times present problems unless the operator takes care to maintain correct use and to avoid false reliance on the alarm's ability to indicate all unacceptable conditions in the clinical setting.

Evaluation of alarm systems for medical equipment.

The provision of automatic alarm systems on medical equipment is generally designed to supplement the user's ability to monitor a variety of device and patient variables simultaneously. The potential value of such systems in improving the safety and efficacy of medical care is accompanied by the potential for false reliance on or other misuse of the alarm systems. Therefore the alarm provisions become an important aspect of clinical engineering assessment of equipment with respect to selection, user training, hazard analysis, and the provision of effective and appropriate preventive maintenance programs.

Home-environment controls for the mobility-impaired.

One aspect of self-care and independence for many older individuals concerns their ability to control their home environment when their mobility is impaired. Although rehabilitation devices have often been custom designed, the availability of these devices has been limited because of high manufacturing costs and a lack of production and marketing channels. It should therefore be recognized that many devices already available to consumers offer a wide range of environmental control without the problems associated with custom design.

Hemodynamic analysis of the ischemic complications of arteriovenous fistulas.

The steal syndrome and its concomitant ischemic complications have long been known to occur in some patients following the construction of various types of access fistulas. A hemodynamic analysis of the flow at a bifurcation provides the basis for understanding the conditions which leads to steal. The analysis also suggests a method for assessing the potential for steal and supports the concept of banding of a fistula as a control measure.