Don Garbuz reported data at 6 years, and to quote the author, “The failure rate due to loosening (4 cases) in this and other reports does prompt the need for refinement of the technique and technology.” (Konan, Garbuz, et al., Hip Intl, 2017)
Why a custom triflanged acetabular component?
It allows for rigid fixation above (into the ilium) and below (primarily the ischium) a large acetabular defect. The fixation, we have found, has been dramatically enhanced with the use of locking screws, particularly in our pelvic discontinuity cases. And shear is limited. Because no matter how high the defect is, there is always a remaining iliac shelf and you can design the globe portion of the custom triflanged device to sit on that ledge, limiting shear on your construct.
It allows for precise reconstruction of the hip center, through the CT scan and the custom design. You can put the hip center wherever you want. Also, it is less dependent on us finding all our normal bone landmarks so it’s very easy to get your cup in the right orientation.
Also, increased construct strength. There is no metal modularity. I’ve never in 15 years of doing these found an implant fracture. It accepts all available acetabular liners. Also, with the potential to cement in a dual mobility construct.
And from that CT I think that is a positive in these cases because you get a lot more pre-operative information: the magnitude; the geometry of the defect. You know what’s left before you walk into the operating room. Also, it shows the presence and severity of the pelvic discontinuity and can even be predictive of the screw length that you need to put in.
I think, also, you can deal with more extensive defects. If you look in the literature, what do a lot do when a cup-cage fails? Go ahead to a custom triflanged device.
Michael Taunton reported on 57 cases treated with a custom triflanged with an associated pelvic discontinuity. They had one case revised for loosening at 11 years, and 81% of the custom triflanged components were stable and the discontinuity healed (CORR, 2012).
In summary, I think favorable results have been obtained with the custom triflanged acetabular component in the pelvic discontinuity cases. It is a stronger, non-modular construct. That pre-op CT provides me with a lot of valuable information including: both the size and shape of the bone defect; the presence and magnitude of the discontinuity; and the precise restoration of the hip center and cup position. And I get rigid fixation on good remaining host bone.
Moderator Lachiewicz: This has brought up a lot of issues I’d like to ask each speaker. So first let’s talk about exposure. Matt, with the cup-cage do you have less dissection, less exposure than with the triflanged?
Dr. Abdel: Good question, Paul. I think both Dr. Dennis and I can agree that for both of these cases you need excellent exposure. In my hands utilizing a cup-cage construct, particularly with the half cage, there’s much less exposure inferiorly. I think we can all agree at the ischium and the pubis there’s less exposure with the half cage cup-cage construct and superiorly I can usually elevate the abductors without going far superior, place the cage and then place my iliac screws at an angle.
Moderator Lachiewicz: One follow-up question. Let’s say you’re planning a cup-cage with a well-fixed femoral component and a modular head. Will you have to do an ETO to do this procedure? Or some type of osteotomy?
