Determining the role of femoral modularity in THA
According to the Millennium Research Group, more than 460,000 primary and revision hip arthroplasty procedures were performed in the United States in 2012 and component modularity in femoral stem design enjoys universal adaptation particular to the use of femoral head-neck tapered junctions providing head size and material choices. The further inclusion of distal neck-stem and mid-stem modular metal-metal tapered connections offer the advantages of off-the-shelf flexibility for customizing proximal and distal canal filling, preservation of soft tissue structures, biomechanical restoration of offset, version and leg length as well as accommodating difficult situations of femoral deformity and bone loss. Coincident with the advantages, concerns relating to design structural integrity attributed to fretting and fretting-corrosion at the tapered connections, stability within the femoral canal as well as debris generation and ion release have been reported. The further influence of these metal-metal interconnections and their role in citations of allergenicity, osteolysis and the occurrence of soft and hard tissue pathologies, heretofore attributed to metal-on-metal articulations, is now a focus of contemporary research and clinical importance.
In this first part of an Orthopedics Today Round Table, a panel of experienced hip arthroplasty surgeons provide insight into the pros and cons of their clinical utility.
A. Seth Greenwald, DPhil (Oxon)
- A. Seth Greenwald, DPhil (Oxon)
- John J. Callaghan, MD
- Iowa City, Iowa
- Michael J. Dunbar, MD, FRCS(C), PhD
- Halifax, Nova Scotia, Canada
- Allan E. Gross, MD, FRCS(C)
- Adolph V. Lombardi Jr., MD, FACS
- New Albany, Ohio
- Wayne G. Paprosky, MD
- Thomas P. Schmalzried, MD
- Los Angeles
A. Seth Greenwald, DPhil (Oxon): In your practice, what is the bearing of choice for primary and revision total hip arthroplasty (THA)? What is the percentage of their employ and is there a patient selection algorithm?
Allan E. Gross, MD, FRCS(C): For all of my primaries and revisions, we use crosslinked polyethylene and a cobalt chrome head. There is no patient selection algorithm.
Wayne G. Paprosky, MD: My bearing of choice for primary THA is ceramic-on-highly crosslinked polyethylene. This is for all patients younger than 75 years. My choice for patients older than 75 years is chrome-cobalt heads on highly crosslinked polyethylene. The head diameter is 36-mm for patients older than 60 years. Inactive patients younger than 60 years also get 36-mm heads. Active patients with cups less than 56 mm get 32-mm heads. Active patients with greater than 56-mm cups get 36-mm heads.
I use the largest head possible for revision THA. This would include up to 48-mm monoblock heads where 48-mm ID polyethylene is available. I will also use bipolars over 28-mm heads. In extreme cases, I will also use large diameter heads of the ADM type and these may be 52 mm or greater.
Adolph V. Lombardi Jr., MD, FACS: Commencing in 2000 to 2008, I selected metal-on-metal (MoM) articulation as a primary bearing for both my primary and revision THAs. In addition, I was a strong proponent of large head technology feeling this contributed to stability in both primary and revision THA secondary to the increased range of motion prior to impingement and the increased jump distance. However, in the past few years there has been a growing concern regarding MoM articulations, elevated metal ions and possible pseudotumor or the so-called adverse reaction to metal debris (ARMD). As a result of concerns over MoM articulations, there has been a precipitous decline in the use of MoM articulations. In response to this concern, I have moved to using a second-generation highly crosslinked polyethylene for the acetabular side in all of our patients. For the femoral side, I use ceramic articulations almost exclusively. However, I use chromium cobalt in patients of low demand and of advanced age (older than 75 years).
In addition to concerns regarding ARMD, there have been an increasing number of patients reporting allergy to metals, specifically nickel. In 12,680 patients who presented for total joint arthroplasty between May 2008 and May 2013, we identified that 425 (3.4%) of the patients reported allergy to metals. When broken down by gender, 5.4% of women vs. 0.6% of men reported allergy. In the patients who present with concerns over allergy, we would advise a ceramic femoral head and, therefore, eliminate chromium cobalt and the possibility of a nickel allergy. In patients undergoing a revision, especially those who are being revised for failed MoM secondary to adverse reaction to metal debris, it is my impression that ceramic articulation should be use, and specifically in failed MoM cases, ceramic femoral heads with the option taper adapter sleeve. Anecdotally having had two cases of fracture of 28-mm heads, I prefer to use 32-mm heads as the smallest ceramic option.
If I am forced to use a 28-mm head, then I will use the option taper since this device has higher burst strength than the standard 28-mm head. Although historically I have been a proponent for large femoral heads, I have conceded to concerns regarding frictional forces on the tapers and the possibility of added stresses and therefore, corrosion of the tapers secondary to the stresses. As a result I prefer to use 32-mm or 36-mm femoral heads and no larger.
Thomas P. Schmalzried, MD: For both primary and revision hips, I prefer a 36-mm diameter bearing, always crosslinked polyethylene, and mostly Delta ceramic femoral heads (DePuy Synthes, Warsaw, Ind.). I may use a cobalt-chromium head in older or lower demand patients.
John J. Callaghan, MD: In all patients aged 75 years and younger, I use ceramic heads, usually on titanium neck tapes, not double tapers, in the primary situation. I still use chrome cobalt heads on very low demand patients. This age limit has increased from age 65 years to 70 years and older, during the last couple of years as I have increased my concerns about tribocorrosion. I would also make a point that we are meticulous about cleaning the taper and applying a heavy on axis impaction to the head.
In revision, I am using almost all ceramic heads (usually large 36-mm heads and greater) both for concern of tribocorrosion at the taper and to potentially help with decreasing head scratching from the third-body particles that are always left after the debridement in the revision situation.
Michael J. Dunbar, MD, FRCS(C), PhD: In both cases, I use exclusively metal-on-crosslinked polyethylene. I typically use a 28-mm or 32-mm bearing. In larger patients with large cup sizes, I will sometimes push to a 36-mm head although I am increasingly reluctant to do so. In some cases where stability is an issue, I will consider a dual-mobility type bearing, but this again would be metal-on-crosslinked polyethylene.
Greenwald: Beyond the femoral head-neck taper, what is the extent of distal neck-stem and/or mid-stem modular metal-metal interconnection use for primary and revision hip reconstruction? In what clinical situations are they employed?
Gross: We have never used distal neck-stem modularity. We use modular femoral components for about 80% of our revision femoral arthroplasties. The modular femoral stem, which is titanium, is used for all femoral revisions where we do an extended trochanteric osteotomy or a trochanteric slide. For some patients where there is no significant bone loss, we will use a 6-inch or 8-inch full porcoat implant which is beaded cobalt chrome.
Paprosky: I rarely use distal neck-stem metal-metal interconnections. My only indication is in high valgus females with very minimal offset. I use mid-stem type modularity in certain dysplastic hips. I do not use mid-stem modularity in primary hips. In revision THA, I use mid-stem modular connections in some type 3 B or type 4 femurs with sever proximal femoral remodeling where anteversion is difficult to determine. Modularity is also used in periprosthetic fractures where leg length determination might be difficult.
Lombardi: I have not utilized the distal neck-stem modular junctions in primary THA. However, I have used modular cones and stems in primary THA. These types of modular devices have been utilized since the mid-1980s. They have an excellent track record and are useful in situations of proximal and distal mismatch, such as patients with Crowe III and Crowe IV hip dislocations. These patients frequently require a subtrochanteric shortening osteotomy. The proximal sleeve can be effectively placed in the proximal portion of the femur, and the cutting splines of the cylindrical stem secure fixation in the distal fragment. This type of modularity is helpful for these difficult cases.
Revision THA has significantly changed in the past several years. The majority of manufacturers have adopted modular revision stems. These devices typically utilize a splined distal component of varying length which engage into the diaphysis with sharp cutting splines. Proximally coned bodies have been used which allow for change in length, version and offset. These devices have dramatically simplified revision hip reconstruction. Early in modular hip revision there was some concern regarding fracture of these devices; however, this has been virtually eliminated with new and improved technology.
Schmalzried: I have not implanted any stem with a modular neck. I use the S-ROM stem (DePuy Synthes; Warsaw, Ind.) in some small patients and higher grade dysplastic cases, which is about 5% of my practice. I use a mid-stem modular component in about 50% of revisions, usually in Paprosky types III and IV and/or an extended trochanteric osteotomy (ETO).
Callaghan: I have never used a modular neck taper. I use modular body stem tapers in many revision situations.
Dunbar: I do not currently use distal neck-stem modularity and would not do so going forward. We have published our unfortunate experience with high rates of fractures with a specific device using this construct. In difficult primaries, I sometimes consider using mid-stem modularity to compensate for metaphyseal-diaphyseal mismatch or significant anteversion issues, such as in developmental dysplasia of the hip (DDH). However, I find a cemented femoral component can get around most of these issues.
In revision surgery, I frequently use mid-stem modularity. Distal fixation is often necessary in these cases and there is often varus remodeling in association with the anterior bow of the femur. The combination can drive a monoblock femoral revision component into excessive anteversion. Mid-stem modularity is helpful in this situation. Also, reconstituting offset in these cases is important for stability and can as well be addressed with modularity.
Greenwald: Have you encountered problems requiring revision with the use of femoral stem tapered interconnections when a metal-on-metal articulating bearing surface was not involved?
Gross: To date, I have not done a revision for metallosis occurring at the junction of a proximal femoral body and the femoral stem. We have had fractures at the junction, but no problems with the taper itself with regards to corrosion, metallosis, etc.
Paprosky: I have encountered problems with femoral stem taper interconnections without MoM bearings. These were in some stems that were recalled and others that were not. Some were in titanium connections and others were chrome-cobalt. The findings were from painful fluid connections to varying degrees of pseudotumors. I have had eight of these.
Lombardi: Unfortunately, some modular stems have been recalled. We have had the opportunity to evaluate patients with the recalled devices. They typically complain of pain, discomfort and limited function, and behave similar to patients with failed MoM articulations. Laboratory evaluation typically reveals a disproportionate elevation of cobalt higher than chromium, and cross-sectional imaging can reveal not only increased fluid but also pseudotumor. I also have had the opportunity to revise patients with typical ARMD, which has been secondary to corrosion from the femoral head-neck modular junction. These patients can present with similar complaints to failed MoM, osteolysis, elevated metal ions (usually a disproportionate elevation of cobalt higher than chromium) and pseudotumor.
Schmalzried: Yes, but just once in the past 10 years. The cementless stem had an “old generation” femoral taper that is no longer employed. I cannot recall revising a non-MoM hip with a “current generation” taper, for a problem due to the taper.
Callaghan: Absolutely. I think large head MoM with modular necks have created some of the largest pseudotumors with muscle destruction and/or neck fracture, but we are beginning to see many cases with polyethylene-on-metal bearings and a few with ceramic-on-metal bearings, especially in some of the recalled or withdrawn double taper neck components.
Dunbar: With the exception of the fractures of a specific prosthesis at the neck-stem interface, I have not seen any issues to date with femoral stem tapered interconnections. I have not seen any fractures in the mid-stem group. I have not seen much in the way of clinically significant corrosion.
For more information:
Michael J. Dunbar, MD, FRCS(C), PhD, can be reached at Dalhousie University, QEII Health Sciences Center, New Halifax Infirmary, Suite 4822, 1796 Summer St., Halifax, Nova Scotia B3H 3A7, Canada; email: email@example.com.
A. Seth Greenwald, DPhil (Oxon), can be reached at Orthopaedic Research Laboratories, 2310 Superior Ave. East, Cleveland, OH 44114, email: firstname.lastname@example.org.
Allan E. Gross, MD, FRCS(C), can be reached at Mount Sinai Hospital, 600 University Ave., Suite 476(A), Toronto, ON M5G IX5 Canada; email: email@example.com.
Adolph V. Lombardi Jr., MD, FACS, can be reached at Joint Implant Surgeons Inc., 7277 Smith’s Mill Rd., Ste. 200, New Albany, OH 43054; email: firstname.lastname@example.org.
Wayne G. Paprosky, MD, can be reached at 25 N. Winfield Road, Suite 505, Winfield, IL 60190.
Thomas P. Schmalzried, MD, Joint Replacement Institute, 2200 W. Third St., Suite 400, Los Angeles, CA 90057-0992.
Disclosures: Callaghan is a consultant for and receives royalties from DePuy Synthes for intellectual property transfer for hip and knee implant designs; Dunbar is a consultant for and receives royalties from Stryker and receives institutional/research support from Canadian Institute of Health Research, Atlantic Innovation Fund, Natural Sciences and Engineering, Research Council of Canada, Stryker, Wright Medical, DePuy Synthes, Smith & Nephew, and Zimmer; Greenwald has no relevant financial disclosures; Gross is an educational consultant for Zimmer; Lombardi is a consultant for Biomet and receives roylaties from Biomet and Innomed; Paprosky receives royalties from Zimmer, is on the speakers bureau and does paid presentations for Zimmer, DePuy Synthes, Medtronic and Stryker, and is a paid consultant for Stryker, Zimmer, DePuy Synthes and Medtronic; Schmalzried receives royalties and consulting payments from DePuy Synthes for hip arthroplasty products.