JISRF Activities May 2010

May 31, 2010

MHRA Medical Device Alert
	MHRA Medical Device Alert for surgeons.	MHRA Medical Device Alert for patients.

Metal on Metal (MoM) Bearings in THA - Surgeon Interviews

There has been considerable debate and controversy over the past few years with regards to MoM bearings. The current issue at hand: Do MoM bearings have a higher incidence of post-operative pain and tissue damage compared to conventional bearings of MoP, CoP or CoC?

In both the U.S. and Australia the recent notice from the British Orthopaedic Association (BOA) has added concern to the selection and use of MoM in THA.

Timothy McTighe of JISRF has conducted an interview with the surgeons listed below on their historical use, current practice and future concerns with the use of all bearing material with special emphasis on MoM bearings.

The 13 Questions of the Interview

1. How long have you been implanting MoM bearings?
2. Do you use MoM for both THA and HR?
3. How many THA using Mom have you done and over what period of time?
4. Have you had any revisions as a result of pain, aseptic loosening or any related issue with the bearing surface?
5. Do you have any concerns over the recent BOA MoM warning letter?
6. What is your current indication for MoM bearings?
7. Do you inform your patients as to the recent concern over MoM bearings and if you do what is your procedure?
8. If not, does recent events make you think you should discuss the concerns of these professional societies?
9. What is your current selection process for any of the bearings that you use?
10. If you stop using MoM for THA will you continue to do HR?
11. What is you percentage of use for HR?
12. What if any advise do you have for your colleagues with regard to disclosure on bearing selection to their patients?
13. Will any of the recent warnings posted by the BOA result in your altering your selection process of bearings?

	Timothy McTighe, Dr. H.S. (hc) Executive Director JISRF Affiliate Member AAHKS Affiliate Member AOA Member ORS Member Society Biomaterials Shands Circle Member OREF & National Board Member			Dr. Bradley Walter Orthopaedic Surgeon private practice Thomasville GA, USA Member AAOS JISRF TSITM Study Group Member
	Dr. Keith Berend Joint Implant Surgeons, Inc. New Albany, OH Member AAOS Member AAHKS Board Member JISRF			Prof. Warwick Bruce Current President of the Australian Arthroplasty Society M.B., B.S.(Syd), F.I.C.S., F.R.A.C.S., F.A. Ortho A. _Orthopaedic Hip & Knee Surgeon, Sydney Australia Clinical/Surgical Research Advisory to JISRF
	Dr. Terry A. Clyburn, P.A. Associate Professor Joint Replacement Associate, Houston TX, USA Member AAOS Member AAHKS Special Ongoing Research Clinical Studies in Evaluation of Total Knee and Hip Replacement, with specific interest in minimal incision techniques and metal on metal articulations.			Dr. Thomas K. Donaldson Founder and Director Donaldson Arthritis Research Foundation Colton, CA. U.S.A. Director, Joint Replacement Surgery at VA Medical Center, Loma Linda, California. Member AAOS Member AAHKS Board Member JISRF
	Dr. John M. Keggi Middlebury, CT. U.S.A. Member of the AAOS Member AAHKS Clinical/Surgical Research Advisory to JISRF			Dr. Louis Keppler Co-Director, The Spine and Orthopaedic Institute at St. Vincent Charity Medical Center, Cleveland, Ohio, U.S.A. Member AAOS Member AAHKS Clinical/Surgical Advisory to JISRF
	Dr. Edward J. McPherson Director of Orthopedic Surgery L.A. Orthopedic Institute Los Angeles, California Member AAOS Board Member JISRF			Dr. Thomas Tkach McBride Clinic, OKC, OK, U.S.A. Member AAOS Member AAHKS Clinical/Surgical Advisory to JISRF
	Dr. Allen Turnbull Orthopaedic + Joint Replacement Centre, Sydney Australia Member of the Australian Orthopaedic Association Member of the Australian Arthroplasty Society Affiliate member of the American Association of Hip and Knee Surgeons (AAHKS) Clinical/Surgical Research Advisory to JISRF			Dr. Bradley Vaughn Raleigh Orthopaedic Clinic Member AAOS Member AAHKS Member AOA Clinical/Surgical Research Advisory to JISRF

Answers

  May 20, 2010

Metal on Metal Bearings in THA - Historical Review

MoM Comments Metal on Metal Bearings in THA have been around since the 1930’s when Phillip Wiles designed and inserted the first MoM THA.

Other historical pioneers followed McKee, Peter Ring, Sivash and they all had different stems and cup designs.

We have seen examples of these devices working well for a number of years and we have seen examples of these devices going on to revision surgery due to a number of different problems. Certainly under today's standards they were all under-designed from an implant to bone stability point of view. However, the articulation often after years of implantation showed little damage upon retrieval.

There is no question that the current concern over MoM bearings has multiple factors that can determine the survivorship of the implanted device. Biological concerns: cellular toxicity, cancer risk, teratogenicity (metal ions cross placenta), metal sensitivity, corrosion, osteonecrosis and fracture.

MoM Bone Necrosis

Long term effects from metal ion exposure requires close monitoring.

JISRF encourages caution in not overreacting to the current situation. It behooves surgeons that have used or anticipate using MoM to be informed and to make sure they are warning their patients to the appropriate risk involved with THA. In fact, this is a good time to suggest that all surgeons review their current patient consent forms and, if needed, be updated. Use this time to learn not only the latest about MoM bearings, but also that all bearings bring about specific advantages and concerns.

Basic Problems

It has been almost three decades since Willert first describe the problem of polyethylene wear leading to peri-prosthetic inflammation, granuloma, bone resporption and implant loosening.3 Since then many publications have discussed this subject.4,5,6,7 Issues have been raised with current materials (MoM, CoC, MoP) from squeaking, high trace elements, strength and implant stability.8,9,10,11,12,13,14

The following are examples of polyethylene failed devices and induced osteolysis:

Ploy II (carbon reinforced poly)	Heat Pressed Poly	Hylamer Poly

UHMWPE	XLPE

Substantial wear reductions have been made with crosslinking technology when compared to traditional poly. However, crosslinking compromised the material's properties and created a new set of problems in dealing with strength issues.

Over all, volume of wear generation is less with XLPE poly. However, there is growing concern on the behavior of the smaller and potentially more reactive particles generated with crosslinking of polyethylene.

Polyethylene insert rim failures.

	Currier BH, Currier JH, Mayor MB, Lyford KA, Collier JP, Van Citters DW,: Evaluation of Oxidation and Fatigue Damage of Retrieved Crossfire Polyethylene Acetabular Cups. Journal of Bone and Joint Surgery. 89: 2023-2029, 2007
	Tower SS, Currier JH, Currier BH, Lyford KA, Van Citters DW, Mayor MB: Rim Cracking of the Cross-linked LongevityTM Polyethylene Acetabular Liner After Total Hip Arthroplasty. Journal of Bone and Joint Surgery. 89: 2212-2217, 2007.

Ceramic head and metal shell failure. Complete wear-through poly 28mm insert.15

Polyethylene induced osteolysis.

Ceramic on Ceramic

CoC is recognized for low wear and no metal ion release. However, fatigue issue can be a problem resulting in component fracture, intraoperative chipping, and now reported articulation noise in the form of squeaking.

Fractures occur for a reason:

• Patient related - excessive demand, trauma, dislocations, etc.
• Surgical technique such as poorly positioned components
• Design related

Articulation noise (squeaking) can be multi-factorial:

• Implant position (impingement, edge loading, subluxation)
• Many factors can contribute to squeaking
• It is a hard on hard articulation issue
• Components design, material and quality are part of the issue
• Emerging reports indicate that it is transient

Improvements have been made.

Summary

Total Hip Arthroplasty is only as good as its bearing surfaces. It's of little value to have the perfect stem and cup component if the bearing surfaces do not hold up for at least the life of the stem and cup. We have seen many advances in all areas of THA with the bearing surface but there is still the need for improvements given today's active life style. Until newer materials are developed - silicone nitride, diamond on diamond, ceramic on metal, polycarbonate urethane (PCU) or something entirely new and different - caution should be used when discussing patient related activities.

Patients tend to do what they want, and then some. Encouraging your patient not to have some restraint in their daily activity can send the message that the new reconstruction is better than the original. Failure to warn your patient as to reasonable risks associated with there surgery and related physical activity can, and will, place the surgeon in harms way legally.

We are not far from having improved hard on hard bearings like Silicone Nitride available for our younger more active patients. This is a strong material that resists deformation. It is 20 times stronger than PEEK and has a hardness approaching that of diamond. This can be formed into a highly polished bearing surface.

This material is in development for bearing surfaces:

• Highly polished, low wear surfaces
• Provides low wear advantages of ceramic with the strength of cobalt chrome

New technologies can provide the low wear advantages of ceramic, the strength of cobalt chrome, and the bony in-growth of trabecular metal. However, until these materials have been fully tested, let's use caution with what we have to work with; understand their material properties (limits) and required technique and full appreciation of the potential risks and hazards in their selection. Patients have selective memory and when things start to go wrong they don’t remember the cautions that were told to them. Document clearly so “failure to warn” is not an argument they can use against you.

Ian Clarke, PhD Board Member JISRF Affiliate Member AAHKS Member of Society of Biomaterials Member of ORS Considered a global expert of tribology

Clarke - MOM

One would be led to believe by the popular press and the BOA announcement that the sky may be falling on MOM bearings. It is there fore very interesting that this group of eleven surgeons have used MOM bearings for 10 to 15 years and amassed over 5,500 cases between them. Even so, the few problem cases can be enumerated on the fingers of two hands. Eleven of this group continue to use MOM and two have abandoned it. The incidence of adverse biological reactions is believed to be in the 0.5% to 1% (Donaldson; Berends). However as pointed out in this article, our community is well aware of this risk and certainly use of alternative cups such as UHMWPE and ceramic clearly introduces other risks.

The true dilemma of MOM bearings is that we are unsure of which patients are at risk and also uncertain of what conditions may trigger the adverse biological reactions reported in Europe and the USA. High CoCr wear rates appear to be one likely cause. The implicated source has mainly been cup positioning although there is a long list of alternative parameters. It is for that reason that our DARF Center in California has been analyzing both linear and volumetric wear rates in retrieved MetasulTM (28mm) and large ball diameters (LBD) cases (38-60mm). We need to know what a ‘normal’ MOM wear rate is, i.e. the clinically acceptable level, and what wear level brings on the reported short-term failures. For example, we know virtually nothing about volumetric wear magnitudes in a 28mm hip versus a 58mm MOM. Similarly in the tribology laboratories, we have been reporting for at least 12 years that MOM hips can turn the lubricant black in somewhat random fashion during the typical 5-million cycle test. We know virtually nothing about how the proteins perform as lubricants in such MOM wear tests. Last month we presented the first analysis of protein-lubricated MOM tests at the annual meeting of the Society for Tribology and Lubrication Engineering in Las Vegas. As Dr. Keggi stated, many centers are now studying this phenomenon and we will know a lot more very soon. The real danger to MOM bearings is that the insurance companies and plaintiff’s attorneys will render their use inappropriate and that would be unfortunate.

Clarke - Ceramics

Silicone nitride (Si3N4) implants are synthesized with 6 wt% yttrium oxide and 4% alumina ceramic. SiN is 3x harder than CoCr and alumina is bout 3.6x harder than CoCr. In terms of strength, the alternate ceramics SiN and ZrO2 average 3.1 times stronger than alumina. These are stronger than even the alumina-matric composite ceramics (Biolox delta TM).

We ran three balls and cups of silicone nitride versus three CoCr balls running in silicone nitride cups. These 1 million cycle tests averaged wear rates of the order 0.18 to 0.2 mm3/Mc, which was in a satisfactorily low wear range typical of ceramics.

References:

• Bobyn, J. D., Collier, J. P., Mayor, M. B., McTighe, T., Tanzer, M., and Vaughn, B. K.: Particulate Debris In TOTAL HIP ARTHROPLASTY: “PROBLEMS AND SOLUTIONS” 1993 AAOS Scientific Exhibit
• Treharne, R., and McTighe, T., A NOVEL APPROACH TO REDUCTION OF WEAR IN THA. 2008 ISTA Poster Exhibit
• Willerrt, H.G., and Semlitsch, M.: REACTIONS OF THE ARTICULAR CAPSULE TO WEAR PRODUCTS OF ARTIFICAL JOINT PROSTHESES. J. Biomed. Meter. Res. 11:157, 1977
• Howie, D. W.,:TISSUE RESPONSEINRELATIONTOTYPEOF WEAR PARTICLES AROUND FAILED HIP ARTHROPLASTIES. J. Arthrop. 5:337, 1991
• Schmalzried, T.P., Jasty, M., Harris, W.H.: PERIPROSTHETIC BONE LOSS IN THA, POLYETHYLENE WEAR DEBRISAND THE CONCEPTOF THE EFFECTIVE JOINT SPACE. J. Bone Joint Surg. 74A:849, 1992
• McTighe, T., Ko, Y., Bennett, R. B., and Adams, J.: A NEW APPROACH TO BEARING SURFACES FOR TOTAL HIP ARTHROPLASTY. 1994 AAOS Poster Exhibit
• McTighe, T., Trick, L., and Koeneman, J.B.,: DESIGN CONSIDERATIONS FOR CEMENTLESS TOTAL HIP ARTHROPLASTY. Encyclopedic Handbook of Biomaterials & Bioengineering Part B Vol 1 1995 Markel Dekker
• Dorr, L., : IMPLANT PERFORMANCE OBSERVATIONS. Letter to AAHKS Members April 22, 2008
• Lhotka, et al., JOR 2003
• Landon, D., Doherty, A., Newson, R.,Turner, J., Bhamra, M.: CELLULAR TOXICITY. J. Arthroplasty 2004; 19:78-83
• Visuri, T., Pukkala, E., Paavolainen, P., Pulkkinen, P., Riska E.B.:CANCER RISK. Clin Orthop and Related Res 1996; 329 Suppl: 280-289
• Ziaee, H., Daniel, J., Datta, A. K., Blunt, S., McMinn, D. J. W.: TERATOGENCITY> JBJS 2007; 89:301-305
• Jones, D. A., Lucas, K., O’Driscoll, M., Price, C.H.G., and Bristol, B.W.:COBALT TOXICITY AFTER MCKEE HIP ARTHROPLASTY. JBJS 1975; 57: 289-296
• Carbone, A., Howie, D.W. et al.: aging performance of a compliant layer bearing acetabular prosthesis in an ovine hip arthroplasty model. The Journal of Arthroplasty Vol, 21 No. 6, 2006
• Tsaroughas, A., Iosifidis, M., et al.: PROTRUSION OF THE CERAMIC HEAD THROUGH THE ACETABULAR SHELL IN TOTAL HIP REPLACEMENT. ORTHOPEDICS 2008; 31:812

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