Friday, December 21, 2012

Incidence of early radiolucent lines after glenoid component insertion for total shoulder arthroplasty: a radiographic study comparing pressurized and unpressurized cementing techniques.

Incidence of early radiolucent lines after glenoid component insertion for total shoulder arthroplasty: a radiographic study comparing pressurized and unpressurized cementing techniques.

Radiolucent lines are a problem in glenoid component fixation. These lines represent areas filled with fluid or debris between the bone and the cement. These zones do not have the potential to turn into either bone or cement and as such represent insecure fixation of the component that can only progress, but not regress. In the figure below, note that there are lucencies around each of the pegs. There are also lucencies beneath cement placed beneath the articular surface of the component - a practice we avoid because this thin cement layer is brittle and can crack, leaving the component unsupported.

In a prospective study of 130 shoulders, the authors of this paper found sigificantly fewer lucent lines in a group of shoulders having a 3-step pressurization as opposed to a group that underwent minimal manual pressurization. In their 3-step technique,  the cement was first pressurized by injecting the cement into each peg hole using a syringe that fit perfectly into the peg hole. The second pressurization was completed by pushing a polished metal rod into each hole. Finally, cement in its doughy state was manually pressurized into each peg hole, followed by placement of the final implant.

We have taken a simpler approach to avoiding radiolucent lines - using a carbon dioxide jet to remove all fluid and tissue from the drill hole immediately prior to cementing. This method has virtually eliminates the radiolucent lines from our post operative films as shown in this film from last week after a total shoulder we performed for a gentleman from California. Note the absence of cement between the face of the component and the bone ( 'bone backing').

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