This week’s Orthopaedic Crossfire® debate was part of the 18th Annual Current Concepts in Joint Replacement® (CCJR®), Spring meeting, which took place in Las Vegas. This week’s topic is “Flatow v. Sperling: Lateralization in Reverse TSA: Bone Graft & Long Stem Outdistances Metal” For is Evan L. Flatow, M.D., Mt. Sinai Health System, New York, New York. Opposing is John Sperling, M.D., Mayo Clinic, Rochester, Minnesota. Moderating is Thomas S. Thornhill, M.D., Brigham and Women’s Hospital, Boston, Massachusetts.
Dr. Flatow: I’m going to talk about the value of bone graft and a long post and some subtleties on it.
To begin, there are different approaches to inclination and lateralization in the reverse shoulder and some really brilliant people have weighed in on this. With all due respect to Seth, it’s hard to be completely binary in this debate and you’ll see as our remarks go on, that there are roles for metal and there are roles for bone even though I’m defending bone graft.
I think when you say, “Should we rebuild bone loss with bone or metal?” surgeons need versatile tools. Much of the literature and experience came from Switzerland with Christian Gerber who taught us to always have a lot of options like a Swiss army knife. Of course, the French school also taught us to have versatile tools. What I am going to give you is a lot of opinion, there’s not a lot of science on this particular one.
I don’t like to lateralize completely with graft because of its weak initial strength, the fact that it can resorb, and the long cantilever moment. I think if you put on a dead piece of bone completely circumferentially, there is the risk that with offset loading and time, as the bone resorbs, it puts a rocking moment on the fixation that’s deep in the canal. Circumferential graft is a means of lateralization and has many risks.
I prefer to use a combination of bone graft with the system I use that has a lateral offset built in with porous material (tantalum) that allows bone to grow in. So, it has initial strength and later has bone ingrowth to become like a “metal bone graft.”
Each system is different. You have to add it up whether it’s in the glenosphere or in the baseplate. Some amount of offset can be achieved through metal within the system or in the size of the glenosphere that is used.
Now the offset compensation. If you take all of the bone away when you want to put on a baseplate, you have to go medial in order to get your fixation. I think that’s the role of the long post which is in the title of our debate because you can’t hold on completely with screws.
You can have a larger glenosphere to give you some offset or you can have it in the baseplate, but when you do use metal, you really have to have fixation that goes medial in the scapula not in the soft resorbed bone laterally and that’s the challenge of metal. Whereas bone graft over time, as it reconstitutes, is able to bear load.
My own preference is to graft an eccentric defect which I think is better than metal because it allows for reconstitution. I like to have a portion of the native bone supporting the construct laterally otherwise everything is hinging on the cantilever loading of the long post. I like to have at least 40% living bone-implant contact so there is some compression and then have a long post with a textured surface to the distal cortex.
I like to use porous tantalum but there are other options. In general I like a post rather than a screw because a screw is the strongest when you first put it in and an ingrowth post gets stronger with time.
