Materials retrieval and analysis - Orthopaedic Biomaterials in Research and Practice - page 396

The recommended analytic approach to the study of retrieved devices
is that of the traditional medical case history study, marrying medical
and engineering approaches. A careful accumulation of clinical find-
ings, the development of a working hypothesis involving both modes
and mechanisms, and the use of clinical and engineering test methods
to substantiate preliminary impressions will result in a coherent view of
device performance in cases with both satisfactory and unsatisfactory
clinical outcomes. In addition, the use of an analytic (triage) system to
establish the level of study of each device can provide results at a sub-
stantially lower cost than is possible through the use of a fixed recovery
and analysis protocol. Finally, provisions should be made for permanent
record preparation and controlled storage of retrieved devices.
Throughout this discussion, the parallel with examination of tissue
removed from patients during surgery will be noted. This is deliber-
ate; it is felt that the problems to be dealt with are essentially identical,
although the device retrieval case is further complicated by the existence
of patient's property and other rights associated with the manufactured
and electively inserted implant. However, many of the same techniques
are used and many of the same benefits result in each kind of study.
The increased enforcement of postmarket product surveillance has
also been emphasized by regulatory agencies. The US Food and Drug
Administration (FDA), for example, has developed initiatives for more
active surveillance through data networks, such as the Sentinel System in
2008. In the orthopaedic world, implant registries have been in existence
since the early 1970s, mainly pioneered by the Swedish joint arthro-
plasty registries. Efforts to develop a similar type of infrastructure in the
United States began picking up steam in 2009. All these data systems
or data networks provide additional resources to better understand the
performance of materials in medical devices in the real world.
Significance of device retrieval and analysis studies
The development of orthopaedic implants has been more or less an
empirical process. From the initial applications of ivory pegs, soft iron
wire, and wood screws in fracture treatment to the use of modern high-
strength alloy total joint replacements, devices have been built from
concept to practice under the guidance of treating surgeons. Safety and
performance have been measured against comparative and subjective
criteria: Is the patient's condition improving? Is the patient satisfied with
the results?
From modest beginnings, the use of orthopaedic implants has grown
to enormous proportions. Between 5 and 10 million metallic, polymeric,
or ceramic parts are implanted each year; perhaps as many as 100 mil-
lion parts have been used and millions remain in patients permanently,
either by design or by chance. The performance of a device in the field
cannot be predicted with 100% certainty, since it is widely accepted that
there are uncertainties in predicting the performance of present devices
owing to the contributions from many factors. From that standpoint,