The Big Question

Additional evidence released this time from the British Journal of Medicine suggests that the high flexion knee and gender specific knee replacement implants do not improve function or patient related outcomes. After a review of 118 studies, they concluded that …

there was no clinically relevant improved benefits for these devices compared with older and established alternative implants. Furthermore, neither of these technologies was found to be safer or to have better survival than the established implants. In fact, high flexion implants in total knee replacement had inferior survival.

Assumptions About Knee Replacement Implants

The authors discussed many critical issues related to implant testing and approval that will probably shock and surprise.

Check carefully to see if you could be making one or more erroneous assumptions about the knee replacement implant industry?

Assumption 1: Present systems on the market are carefully vetted through controlled and evidence based studies.  WRONG

Our goals are to highlight that the status quo regarding the introduction of new device technologies is not acceptable, that substantial efforts are needed by all stakeholders to invest in systems of careful evaluation and to promote controlled and evidence based introduction of device innovations.

Assumption 2: Benefits of new implants have been convincingly established prior to marketing.  WRONG

This is particularly important when the comparative benefits of new device related technologies have not been convincingly demonstrated. Exposing large numbers of patients to new devices with uncertain safety could be considered unethical and should be avoided without controlled introduction and proper systems of evaluation. In this context, stepwise introduction of device related technologies has been proposed

Assumption 3: The risks of releasing new implants on the general population have been throughly evaluated prior to marketing. WRONG

For now, the need for new device technologies and the associated expected benefits need to be carefully balanced against the possible associated risks. We suggest adherence to the IDEAL recommendations, and when clinically relevant improvements have not been convincingly shown widespread commercial introduction should be deferred until appropriate long term safety comparable to existing technologies has been demonstrated.

No Criticism Of the Surgical Community or Orthopedic Industry Intended

The search for implants with superior functional outcome, increased longevity, and better survival is needed. Hence, this review is not intended to criticise the surgical community or orthopaedic industry.

Pathway for Implant Approval 

At this time, as moderate-risk, class 2 medical devices, incremental changes to devices can be made through the 510(k) pathway, which requires manufacturers to demonstrate that the new product is “substantially equivalent” to the design that was previously approved. The authors of the study suggest that improved features should be tested in smaller groups of patients before being approved for wider use.

Others have suggested that a black box warning of sorts for knee replacement devices could help correct the misapprehension of benefits and understating of risks inherent in new devices that current marketing engenders in the public.

You might also be making one or more erroneous assumptions about total knee replacement rehab. Read more

WHAT THE FDA REQUIRES FOR CLASS 2 AND CLASS 3 DEVICES

Premarket Notification (510(k))

510(k) is required when demonstrating substantial equivalence to a legally marketed device, when making significant modifications to a marketed device, and when a person required to register with FDA introduces a device for the first time. If a device requires the submission of a 510(k), it cannot be commercially distributed until the FDA authorizes it.
Substantial Equivalence
A device is substantially equivalent (SE) if it has the same intended use and same technological characteristics as a legally marketed device, known as the predicate. A legally marketed device:
1. was legally marketed prior to May 28, 1976 (“preamendments device”), for which a PMA is not required, or
2. was reclassified from Class III to Class II or Class I, or
3. was found SE through the 510(k) process.
Applicants must compare their device to one or more similar legally marketed devices and make and support their SE claims. If the device is SE to a predicate, it is placed in the same class. If it is not SE, it becomes non-SE and is placed into Class III.
Examples of 510(k)s include x-ray machines, dialysis machines, fetal monitors, lithotripsy machines, and muscle stimulators.

Premarket Approval (PMA)

PMA refers to the scientific and regulatory review necessary to evaluate the safety and effectiveness of Class III devices or devices that were found not substantially equivalent to a Class I or II predicate through the 510(k) process.
PMA is the most involved process. To reasonably assure that a device is safe and effective, PMA requires valid scientific evidence that the probable benefits to health from the intended use of a device outweigh the probable risks, and that the device will significantly help a large portion of the target population. Sources of valid scientific evidence may include well controlled investigations, partially controlled studies, historical controls, well documented case histories by qualified experts, and robust human experience.
Independence is an important concept for PMAs, meaning that each PMA should establish the safety and effectiveness of the device under review, and that data about one device cannot be used to support another.
Examples of PMAs include digital mammography, minimally invasive and non-invasive glucose testing devices, implanted defibrillators, and implantable middle ear devices.