Materials retrieval and analysis - Orthopaedic Biomaterials in Research and Practice - page 395

CHaPTer SIXTeeN
Materials retrieval
and analysis
With the exception of a very small number of studies, orthopaedic
devices that “fail” in service are still not routinely or systematically
collected and studied. Studies of those implants that are collected tend
to concentrate on the physical findings obtained from the device itself,
neglecting the patient and events of treatment. Clinical reviews and case
reports of implant malfunction tend to focus on the patient, often to a
near total exclusion of an engineering description of the device. Finally,
both types of study concentrate on frank failures, with an absence of
comparative data from successful or partially successful performance
of similar or identical devices. Thus, much of what we think we know
about orthopaedic device performance is drawn from a very small, non-
random sample of the actual clinical experience. This is an error, in the
same way that studies of criminology based solely on prison populations
are.
This error is further increased by a failure to separate materi-
als aspects from device aspects. In fact, with few exceptions, study of
retrieved devices focuses on mechanical features of the devices and the
local host response to these features. A more careful approach would
yield useful information concerning biologic performance of biomateri-
als in clinical use.
An additional reason to become more thorough in studying devices in
clinical experience is the increasing interest being shown by both law-
yers and (in the United States) federal regulatory officials. The pres-
ent system and practice of device removal make it difficult to account
for particular devices, to establish that a particular device was removed
from a patient, and to determine the device's condition at removal. The
ability to deal with these questions is desirable and may in the future
become mandatory.*
* Postmarket introduction surveillance orders by the FDA (“522” orders) frequently man-
date such reporting in subsequently approved study plans.