Gross v. Berend: The Cup Cage Construct: Preferred Solution for Pelvic Discontinuity

This week’s Orthopaedic Crossfire® debate was part of the 34th 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 Allan E. Gross, M.D., F.R.C.S.(C), University of Toronto, Toronto, Ontario, Canada.Opposing is Keith R. Berend, M.D., Mt. Carmel New Albany Surgical Hospital, New Albany, Ohio. Moderator is Daniel J. Berry, M.D., Mayo Clinic, Rochester, Minnesota.

Dr. Gross:  The options for chronic pelvic discontinuity are:

1. plate and an uncemented cup
2. a cage and structural allograft
3. a large uncemented cup plus or minus an augment with pelvic distraction
4. a triflange cup
5. 3D printed custom implants and
6. finally, the cup cage.

The custom triflange cup. A study from the Hospital for Special Surgery (J Arthroplasty, 2016)—63 patients – reported fairly good results, although the dislocation rate was high. The revision rate was 13.5%. And they did not separate discontinuity in the series. There is a big difference in the results of these reconstructions between those with and without discontinuity.

A study from my worthy opponent’s center (Clin Orthop Relat Res, 2015)—23 patients—reported very good results with 0% dislocation. But, once again, they didn’t separate pelvic discontinuity. I’m sure we’ll get more up-to-date data.

A very good series because part of it comes from Nashville—which actually talked a lot about the triflange cup (Clin Orthop Relat Res, 2012)—57 patients; pretty good follow-up (average 65 months); 81% had a stable reconstruction. Twelve patients, however, had instability and 10 of those required revision.

Now the cup cage construct. A paper we published back in 2014 (Bone Joint J, 2014) showed that the cup cage did better than conventional cages.

The cup actually bridges the discontinuity and ingrowth occurs on both sides of the discontinuity. You don’t get a primary healing of the discontinuity. It’s like a fracture due to a metastasis. It will not heal primarily so what we try to do with the cup cage is get ingrowth on both sides of the discontinuity.

In our latest publication (Clin Orthop Relat Res, 2016), we describe all of our cup cages, but a large percentage were discontinuity. Seventy-five cup cages, three tumor cases and one acute fracture were excluded and we lost four patients to follow-up so we had 67 cup cages in 64 patients with a good follow-up (average 73.5 months) for a revision series.

Within this study, there were 26 Type IV defects (bone loss greater than 50% of the acetabulum) and 41Type V defects with pelvic discontinuity. For cases without pelvic discontinuity, the revision rate was 7.6%. For cases with pelvic discontinuity, the revision rate was 9.1%. So there is a difference, but still a very good result.