Bending in Midair
By Steve Hill, BOCO, CO

I must have led a sheltered life as a young technician. I always thought there was only one way to bend uprights to shape.

Boy was I wrong.

There are actually two ways to bend metal uprights: use an alignment jig or "bend it in midair," as my teacher called it. This method is the fastest and most effective method, though that's just a matter of opinion.

In truth, whatever way you practice most is going to be the most effective. But, if you don't know both ways, then you may not know which works best for you.

For most technicians, the alignment jig is a common bench tool.

Alignment jigs come in two basic varieties: internal and external.

Obviously, internal jigs are placed inside of the cast, either during the pour or drilled to fit after the pour. External jigs are placed outside of the cast and connect the two joints externally, allowing for easier removal from the mold.

Internal jigs are most commonly used at the ankle joint, where the alignment can be seen before filling the cast (Integrated Ankle and Gaffney).

External fixtures see most use at the knee, where alignment may not be so clear or varus/valgus corrections may need to be fine-tuned. The external fixtures can either be handheld (Becker and Cascade) or come attached to a much bigger system (V-Tech, Becker and O&P Equipment Corp). These systems, while efficient and cost effective, do require the initial investment in a multifunctional setup and are not job-specific tools.

The "midair" method is, in my opinion, the least expensive and most versatile method, because it allows for the invariable fluctuations in plastic spreading and shrinking.

What I mean is after the joints have been mounted in this inflexible metal jig to keep them square, the uprights are eventually screwed or riveted to the plastic cuffs. When taken off the cast, these cuffs will either spread open or shrink inward a little.

It doesn't take much spreading or shrinking to affect the parallel alignment of the joints adversely. And then, you have to rebend the uprights square again, doubling your work.

Now, read how OTS does it.

First, we draw knee center, just like everyone else. Then, we disassemble proximal and lower sections from each other and contour each proximal side, making sure the knee center drawn on the cast is centered in the pivot hole in the proximal joint head.

Once each proximal upright is contoured, it's nailed onto the cast, right through the plastic cuff, assuring that it won't slip while contouring the distal uprights. Also, the holes will align through the upright and plastic cuff, where it will be attached by either a screw or rivet.

Now, contour the distal uprights to the cast. To hold the proximal and distal joint heads together, we use a little homemade tool. Using a leftover joint bushing and a longer screw to attach and detach the joint heads quickly while bending, you can make one by simply screwing the bolt into the bushing. Make two and keep them handy, right next to the bending irons.

Once the uprights are contoured and all of the holes are drilled, remove them from the cast and finish as usual. Drill out the holes in the plastic cuffs and attach the uprights. At OTS, we use SS screws to attach our uprights to make adjustments and repairs easier.

Now, you can assemble the proximal and distal joint heads together and check alignment. Of course, it's not perfectly square. It never is. No matter if you used a jig or bent it up by eye, you'll have to resquare the joints. The reason for this is very simple.

As soon as you attach the uprights to the plastic cuffs, the relationship of the uprights—and, by extension, the joints—is changed. Tightening the rivets and screws against the softer plastic makes it catawampus.

So, invariably, you must resquare the carefully prepared alignment. But, just get them in the ballpark, and then worry about how square they are after assembly.

That's another good reason to attach with screws. If need be, and it only happens occasionally, we can sand any bend marks in the uprights.

And that's it. I know that most of you use an alignment fixture and will never try bending it in midair. But, should the need arise, now you know the method used by professionals the world over—or, at least in Weaverville, N.C.

Steve Hill, BOCO, CO, is with OTS Corp. in Weaverville, N.C. He is the secretary of OPTA. For more information about OPTA, call (866) 736-2637 or visit www.oandp.com/opta.