This week’s Orthopaedic Crossfire® debate was part of the 35th Annual Current Concepts in Joint Replacement® (CCJR®), Winter meeting, which took place in Orlando. This week’s topic is “The Cup Cage Construct: Preferred Solution for Pelvic Discontinuity.” For is Matthew P. Abdel, M.D., Mayo Clinic, Rochester, Minnesota. Opposing is Douglas A. Dennis, M.D., Colorado Joint Replacement, Denver, Colorado. Moderating is Paul F. Lachiewicz, M.D., Duke University Medical Center, Durham, North Carolina.
Dr. Abdel: Pelvic discontinuity is where the superior and inferior hemi-pelvises are no longer joined. Contemporary reconstructive options include cup-cage construct, which is my preferred method; distraction method as popularized by Paprosky, et al., which encompasses cup-cage construct; and what likely Dr. Dennis will discuss is a custom triflange (Abdel, et al., JAAOS, 2017; Sculco, et al., JBJS Am, 2017).
So, why do I prefer a cup-cage construct for the treatment of pelvic discontinuity? Three simple reasons.
- I can place a highly porous cup acetabular component directly against host bone and use highly porous augments to supplement bone loss using superior or medially
- I can plan supplemental screws anywhere that there’s remaining bone, typically that’s superior and inferior, utilizing the acetabular component as if it’s an internal plate for the discontinuity
- I can utilize a half- or full-cage as reinforcement for the construct.
What is the technique?
First, identify the discontinuity. Then, remove that fibrous tissue and place bone graft. Thereafter, I utilize acetabular augments. Thereafter we’ll reverse ream some bone graft in there. Place cement on those augments and put a highly porous acetabular component directly up against the patient’s own bleeding bone.
Thereafter place supplemental screws and we can use a half-cage. My preference is to remove the inferior flange of that cage and what that allows us to do is avoid that inferior dissection by the sciatic nerve. Remove one screw that’s going through the dome, through the cage and place that up through, unitizing the construct, and cement the polyethylene liner utilizing that whole construct as a unification for that patient.
So, what’s the data with this technique?
There are now multiple series with mid-term follow-up looking at pelvic discontinuities, treated with a cup cage, some survivorship free of revision, some around 90% for some of our most difficult cases (Koshashvili, et al., JBJS Br, 2009; Rogers, et al., JOA, 2012; Amenabar, et al., CORR, 2016).
What about the half-cage technique that I alluded to? We recently published our series in JBJS Am (2017) looking at this technique. The half-cage technique entails removing the inferior flange of the cage. My preference is to utilize a contralateral sided cage; remove the inferior aspect; avoid the dissection by the sciatic nerve; remove one screw that was going through the acetabular component in the dome and place that through the cage, through the acetabular component and into the host bone. Then cement a polyethylene liner.
