Session VIIIFixation Devices

• Casts are stress sharing• Pins, screws, Steinman pins and Kirschner wires

when used alone provide partial immobilization and are stress sharing.

• Compression screws and plates are stress shielding or bearing.

• External fixation is stress sharing– No metal at fx site: distal and proximal– Avoids excessive soft tissue dissection– Potential loss of joint motion due to penetration of multiple

tissues– Applicable to any long bone fx

Casts are stress sharing

Intramedullary rod with locking screws-stress sharing

Tibial nail unlocked (L) and statically locked (R) are stress sharing

K wires are stress sharing

Screws: Note threads and flutes

Cortical Screw: May-depending on type- require tapping of threads into cortex. Small flutes, designed for solid cortical bone. Can be used for fixation of bone to bone or hardware to bone. Will not create compression without over-drilling near cortex.

Cancellous screw: self tapping. Large flutes for gripping softer spongy bone. Usually used for bone to bone fixation. Will create compression. May be used to attach hardware.

Cortical Screw

Self-tapping flutes on this example.

Cancellous ScrewNote the larger flutes

Comparision of cancellous and cortical screws.

Fixation plates. Many types available. These are malleable and are hand-bent to fit bone contour. Note oval screw holes. Eccentric placement of screw within hole allows

compression of fracture fragments.

Screws combined with plates are stress bearing.

Dynamic Compression Plate

Kirschner Wires and Steinman PinsK-wires are smaller, come in smooth or threaded,

usually in 3 sizes: .035, .045, and .062.Steinman pins are larger.

Steinman Pins Kirschner Wires

• Thicker

• Usually Threaded

• Thinner

• .035• .045• .062• Threaded or plain

Cerclage Wires and Staples

Stainless Steel Monofilament Wire

SS Wire in Cerclage

AP View Cerclage

K-wires used for small bone fixation. The hooked portion protrudes through the skin allowing “easy” removal.

Lateral View, same wrist

Medullary Rod. Here a femoral rod.

Note locked rod fixation to prevent rotation, and “pistoning” of rod.

Canulated ScrewK-wire used as guide for larger screw: less bone loss if error occurs and second placement attempt is required.

Canulated Screw: where you really don’t want to lose too much bone while getting the screw just right.

What was the pre-op Dx?

Try this one for practice.

Practice film #2. Dynamic hip screw