Med Device Monday: Bone Mills


I smell the blood of an Englishman

Be he alive or be he dead...

We all know what comes after those famous lines. But did you know that in some translations, it reads "Be he alive or be he dead, I'll grind his bones to make some bone graft"? Languages are amazing!

Okay, maybe not. But what's not an exaggeration is that bone mills are pretty amazing. In simplest (and slightly disturbing) terms, they're like a coffee grinder for bones—but with a pretty noble purpose.

They can look quite simple:

Photo from innomed.com.

Photo from innomed.com.

Or they can be more complex:

Photo from stryker.com.

Photo from stryker.com.

But however they look, the purpose of these devices is roughly the same: to grind up somebody's bone to be used during surgery. These devices are often used in the Operating Room to grind up a patient's bone to be placed back into the same patient. 

While they're not new, these Class I (lowest risk) medical devices are truly brilliant in their simplicity. Grinding bones to use for bone grafting go back a long way. This interesting history of bone grafting discusses osteopathy in 1863, and cites examples in 1889 (tibia bone used to heal a skull defect) and 1910 (a split rib was used to heal a skull)! 

Screenshot from sciencedirect.com.

Screenshot from sciencedirect.com.

In today's Operating Room, no ribs are split and attached to skulls. Instead, bone mills are used to grind up bone to make grafting material. As mentioned earlier, using the patient's own tissue is often preferable as tissue that comes out of one's own body has less of a chance of being rejected. Taking a piece of hip bone out of a patient to grind it up and help rebuild that same patient's spine, for instance, fits into this category.

Class I devices like bone mills don't require a 510(k) premarket notification. However, they are still required to comply with general controls such as registration and listing, labeling, and GMPs. You can read more about these requirements on FDA's page about Class I devices.

It's always good to look back on the history of devices and procedures. While medical technology has certainly advanced—and we are better for it—some things remain the same.


Further reading:

Bone mill product classification and regulation

I often include videos in posts in order to show how a device works. This time, I am linking to a video with the disclaimer that, while it does show how a manual bone mill works, it is not for the faint of heart—so proceed with caution: 

Video of a bone mill being used

Med Device Monday: Bone Anchors

FDA has just released a draft guidance for bone anchors. This new draft guidance document, dated January 3, 2017, is a reissuance of the previous version from April, 1996: "Specifically, this guidance reflects the most current thinking on relevant bench testing methods for bone anchor devices including nitinol and absorbable polymeric bone anchors." 

Bone anchors! These cool medical devices help attach soft tissue to bone. Partial or full detachment from the bone of ligaments, tendons and other tissues, are common injuries. Think achilles tendons, rotator cuff tears and other shoulder injuries, ACL tears and other knee injuries, and countless other ailments. While these tissues can re-attach without intervention, in some cases, especially with complete detachment, surgery may be necessary to help the process along. Bone anchors assist with these surgeries by, literally, anchoring a suture to the bone from the tissue. The injury will then heal as the as the connection between bone and tissue is reestablished.

Have a look:

Photo from dolcera.com.

Photo from dolcera.com.

Photo from smith-nephew.com.

Photo from smith-nephew.com.

This video provides a pretty cool illustration of how it works:

And this video provides a different angle and shows a different type of anchor:

Some of these anchors, like some of the sutures they help affix, are dissolvable. It's always impressive to encounter a device that can do its job and then quietly disappear. The new draft guidance focuses on this area, and the Office of the Federal Register explains, "The guidance provides recommendations for the information and testing that should be included in premarket submissions for bone anchor (suture anchor) devices used in the appendicular skeleton for attachment of soft tissue to bone. This draft guidance is not final nor is it in effect at this time."  Comments are being accepted through March 6, 2017, and the link above to the Federal Register explains how they can be submitted.


Further reading:

Code of Federal Regulations for single/multiple component metallic bone fixation appliances and accessories

Corresponding MAI product code

Code of Federal Regulations for smooth or threaded metallic bone fixation fastener

Corresponding MBI product code

Guidance Document for Testing Biodegradable Polymer Implant Devices