The discovery of acrylic cement for use in total hip surgery

The history of "discovery" of bone cement for use in surgery of total hips is a good illustration of the statement made by Sir Wiliam Osler, a renowned English professor of Medicine, who said: “In science the credit goes to the man who convinced the world, not to the man to whom the idea first occurs”.

 Show: Picture of title pages of Haboush's  paper and Charnley's  book

 As it happened, neither the use of the total hip replacement device nor the use of bone cement for its fixation did spread from New York to the USA’s orthopaedic surgeons. Doctor Haboush is unknown for the majority of contemporary orthopaedic surgeons.

John Charnley, on the other hand, is today universally (and rightly) credited with introduction of bone cement in the surgery of total hip joints.Why?

The answer on this question is not simple.  One reason may be the fact that in contrast to Europe, the USA had since 1927 a central institution (FDA) that regulated the use of drugs and that this institution initially did not approve of the use of acrylic cement in bone and joint surgery.

The English surgeon John Charnley, on the other hand, was using bone cement for fixation of total hip joints since 1957. unhampered by any supervising agency. What is more important, John Charnley also spread the knowledge how to use the bone cement among the world’s surgeons. John Charnley used the acrylic cement that was developed for dentists (NuLife TM)  as did Doctor Haboush. It lasted to1965 until John  Charnley began to use the proper “bone cement” developed specifically for total hip replacement (CMW Bone Cement TM).

Illegal trade with bone cement over the Atlantic.

In the 1960’s, the American surgeons traveled to John Charnley who worked at the Wrightington Hospital in England to learn the total hip surgery.

In the USA bone cement was, however, not generally available in the 1960’s and early 1970’s   because the FDA just then did not approve of the use of bone cement for total hip surgery.

 Thus, on their way back to States, the American surgeons brought with them several packages of John Charnley’s bone cement to use it with their total hip operations on their American patients. A busy illegal trade with English bone cement thus developed over the Atlantic.

FDA regulation lagging behind the development

 It lasted until 1969 when  the FDA approved for the first time the use of bone cement in a clinical experiment. In that year got the Mayo surgeon Marc Coventry a special license for use of bone cement for fixation of total hip devices, just sixteen years after the publication of doctor Haboush’s paper. After the first experiments in the USA with bone cement that showed very good results the FDA reversed its policy. Since the mid 1970's the FDA prescribed that all newly approved total hip devices should be used with bone cement.

And here comes the second peculiar event in the history of use of bone cement in the USA.

The FDA regulation that all total hips should be used with bone cement fixation lagged behind the development of new total hip models. Since the mid of 1970’s  the bone cement was successively falling into disrepute among some surgeons both in Europe and the USA. These surgeons were accusing the bone cement for causing premature failures of the total hips. The innovative surgeons longing for better total hip models, the bioengineers seeking new areas of work and the manufacturers reacted on these ideas accordingly. They developed together total hip joint models that should be used without the bone cement that caused this dreadful bone cement disease. These new total hip models were called cementless total hips.

First "modern" cementless total hip devices were put on the European market in the mid 1970’s. The French surgeon Rober Judet published his results with the cementless total hips in 1978 in an American Journal and his colleague Lord in 1978 too, but in a French Journal. These publications started the competition between cemented and cementless total hip models that raged at most in the 1980's.

Bone cement disease

In the USA, many of the influential total hip surgeons were, however, members of the Low Friction Society and their influence on their colleagues was considerable. And they still  recommend the use of bone cement. To bring the use of bone cement into disrepute in the eyes of the majority of American total hip surgeons it was necessary to come with more than scientific arguments. The term “bone cement disease”, propagated originally by the American surgeon Hungerford (Hungerford 1987), added an emotionally disreputable characteristic to the bone cement. 

 The theory of  "bone cement disease"  said that the the bone cement was a fragile material that moreover aged. As the bone cement aged it  became even more brittle. Small particles of bone cement separated from the cement layer and came in contact with bone tissue, There, the particles produced inflammation-like changes that successively dissolved bone tissue. Bone cement disease was the  dissolving of the skeleton observed around the cemented total hips -an  osteolysis that eventually ended with failure of the total hip.

According to the doctor Hungerford the characteristics of the current bone cement were such that it was impossible to improve the product. There were only two alternatives left: either to develop a new and better "grout" or to go over to cementless fixation.

 The  term "bone cement disease" was a strong argument used to promote the newly constructed models of cementless total hips on the market. The idea was embraced by the manufacturers: it offered endless possibilities to modify the form and surface of the cementless total hip models. These small modifications allowed the production of steady new models of cementless total hips.

When the cementless total hip models were introduced on the market, it appeared, however, that the typical "bone cement disease" with dissolving of the skeletons appeared also in the cementless total hips although no bone cement was used in these operations.

Surgeons then simply changed the name from "bone cement disease" to "particle disease". The blame on bone cement, however, remained.

Show Picture: The first cementless total hip joints

Whereas new models of cementless total hips were being introduced on the European continent, FDA still adhered to its policy that prescribed cement fixation for all total hip devices, even for those porous coated models developed for use without bone cement. Behind this obstinacy was the simple fact that the cemented total hip models had much longer follow up experience behind them whereas there was practically no experience (in the USA) with the cementless total hips. Thus, the FDA ordered the surgeons to wait until more experience with cementless models will be gathered. This bureaucratic obstinacy had unexpected and bad consequences.

Show Picture : Mallory-Head TM total hip.

 

Cementless total hips to be used without cement - on permission only (in the USA)

In Europe, the surgeons simply did not use bone cement for fixation of cementles total hips.  In the USA the manufactures, however, were forced to apply for special license at FDA so that the American surgeons could abstain from the use of bone cement when  implanting total hip models constructed to be used without bone cement. The possibility to use a cementless, porous coated total hip model without bone cement  was now seen as an advantage on the American market. Altogether a curious situation.

Show Picture: Approval seal of cementless total hip stem

Later on several cementless total hip models were approved for general use without bone cement. Nowadays, the majority of total hip devices in the USA are used without bone cement (cementless).

Metal backed cups do not like bone cement

Another epidemic of total hip failures followed the introduction of metal-backed polyethylene cups that were fixated with bone cement. In this case, the culprit was not the bureaucratic obstinacy but reliance on a new computer modeling method - finite element analysis. An armchair science at its best.

The whole affair started in the late 1970's with observation made by some surgeons that monobloc polyethylene cup fixated with bone cement have had  rather high rate of failures, up to 25 % within 10 years. At the same time, however, the experienced surgeons such as John Charnley or Marc Coventry, who carried careful statistics, observed only about 10% cup failures within same time period.

The biomechanical scientists, however, advanced a theory that the high failure rate of cemented polyethylene cups is the result of polyethylene's softness. A new computer modeling method, finite element analysis, confirmed this theory - on computer models. You must remember, however, that in the late 1970's and early 80's, the computer power was not what it is now; the computer models studied were very primitive, the studied object (the cup) had only two dimensions. Notwithstanding the primitiveness of these models, many surgeons accepted them gladly as true. And when these surgeons believed that one  discovered the source of the problem one started to do something about it. The bioengineers embedded the soft polyethylene cup in a hard metallic sleeve.

Manufacturers produced these new metal-backed cups to be used with bone cement, thus the surface of the metallic sleeve was rough. Manufacturer of one such cup wrote: "The cup delivers superior cement performance with a textured surface..." (Richard's Spectron Cup). You can only guess what is "a superior cement performance".

Early results with the cemented metal backed polyethylene cups were promising - because that were the early results (follow-up of 2- 5 years only).  After longer observation time ( 9 and more years) it became obvious that metal backed polyethylene cups do not tolerate cement fixation. In some reports metal backed cemented polyethylene cups produced up to 25 % failures within six years after surgery (Chen 1998).

Results of the Spectron total hip in the Swedish National Hip Register speak for themselves: In Sweden between the years 1984 and 1994, one operated on totally 2301 cemented Spectron total hips models; from them 939 had all polyethylene cup (without metallic sleeve) and 1362 had metal backed polyethylene cup (as that on the upper picture).(Malchau 1998)

Within ten years after the surgery, only 0.9% of all  Spectron total hips with all polyethylene cup failed; whereas under the same time period failed 12.1% of all total hips with metal-backed polyethylene cup. Calculating the percentages into the number of failed total hips, it appears that 154 total hips could be saved from failure if the surgeon did not use the metal backed cup model in Sweden. How much patient misery could be spared?

The Boneloc catastrophe

Already in the late 1960’s there were four basic concerns with the use of bone cement: That it promotes development of postoperative infection, that it produces allergic reaction in the patients, that it develops too much heat during curing, and that its components (monomer) may cause heart failure. Later on the fifth concern appeared: the fumes of monomer caused headache, nausea, and dizziness in operation personal (mainly nurses who mixed the bone cement in open bowls). For more details about bone cement characteristics see also the chapter Bone Cement for total Joints.

John Charnley discussed at length in his book all possible risks connected with the use of bone cement inclusive of the risk of cancer development . He concluded that use of bone cement was not associated with risks, neither for the patient nor for the function of the total hip. Charnley's conclusion were not accepted by all orthopaedic surgeons and from time to time there were reports from individual surgeons about damaging effects of the bone cement. In the mid 1980's, Swedish surgeons published reports pointing to two damaging characteristics of bone cement: first, bone cement leaches toxic monomer that intoxicates the skeleton around the cemented total hip; second, when the bone cement hardens (polymerizes, cures) it emits heat that damages the skeleton. Both these characteristics lead to loosening and eventually failure of the total hip, suggested these surgeons. Thus the idea that bone cement has dangerous effects had support in laboratory experiments.

. On the other hand, the results of cemented total hip replacement, as recorded from several surgeons and newly founded National Registries, did not demonstrate deteriorating results. On the contrary, the improved cementing techniques resulted in improved results of cemented total hips. Thus, the patient results do not demonstrate these that these dangerous cement characteristics are causing serious problems.

In spite of these good clinical results with bone cement, the Danish surgeons at Copenhagen University Hospital together with material scientists started development of a new bone cement product in the 1986. The goals were: First, the product should contain and emit less quantities of the toxic monomer and at polymerization the product should emit less heat. Second, the product should be more strong and produce better fixation of the total hip than the present bone cement.

The scientist succeeded in their work: the new product leached less toxic monomer because it contained less of it (the monomer was replaced by another substance). The product also emitted less heat during polymerization (because its composition waas changed). The measurements of the strength of the new product produced values that were interpreted by some as better, by some as worse than values of the present bone cement. The product could, however, not be called polymethyl metacrylate as was the Charnleys bone cement. The developers called it BONELOC TM

The manufacturer was the Danish company Polymers Reconstructive A/S although the product was introduced on the market by the Biomet Company. How much was Biomet company involved in the whole process of development of the BONELOC from the beginning was never revealed. Biomet also developed a special closed cement gun for mixing and application of the BONELOC. The closed cement gun secured that no monomer fumes could escape into the air of operation room during mixing of the product. This would be an important advantage especially for the planned introduction of the product on the USA market.

BONELOC was introduced on the European market in the 1991. Biomet company advertised this product in 1991 in the British issue of the  renowned Journal Bone Joint Surgery (click on the icon for a full size picture).

If we go after the individually published reports, the number of patients operated on with BONELOC was not great, less than 100 operations in every published report. How many patients were operated on by surgeons who did not publish their results we would, however, never know.

All published reports demonstrated an early and catastrophic failure rate of total hips  cemented with this product. For example one article of Danish surgeons has the title:

(Riegels-Nielsen 1995). Try to understand it:  In 65% of all operated on patients the total hip failed within less than 4 years because the surgeons used a previously unproven bone cement! 65% of all patients  were subjected to the misery of pain and all the risks of revision operation because of the armchair science!

On the USA market, the FDA never approved of the general use of BONELOC although the product (marked as a product of Biomet Company) was used on some USA hospitals, mostly for purposes of later submission for the approval by FDA.  The results there were equally bad as those on the European continent (Markel 2001).

In 1994 the Norwegian surgeons issued a ban of the BONELOC in Norway, their decision was based on the disastrous evidence from the Norwegian National Arthroplasty Register accumulated there and in April 1995 the Biomet company retracted the product from the market worldwide.

 In the aftermath one discussed the moral responsibility of the Danish manufacturer of the product and of its distributor Biomet. One discussed also the ethical responsibility of surgeons who chose this unproven product in their patients instead of the well proven products (Linder 1995).

Were at least the patients informed before the surgery? Probably not. At least none of the articles on the Boneloc catastrophe mentions patient information and patient consensus issues.

The development of cementing techniques

The cementing technique, however, did not stand still. Improvements included all steps in the cementing technique: preparation of the bone cement, cleaning of the holes (beds) in the skeleton from blood, insertion of bone cement. The improvement was such that the surgeons (and manufacturers) speak about two, or three, generations of cementing techniques.

The first generation cementing technique was the technique used originally by John Charnley. He used this technique still in the late 1970's. The following pictures are adapted from his book published in1979.

Show Picture: First generation of cementing technique

(Click on the icon for a full size picture).

( 1 ) After opening of the medullary cavity of the thigh bone the surgeon packs it with "  dry gauze" to stop the bleeding there. Charnley describes in detail special technique how the medullary cavity should be backed from bottom up. When the gauze is removed from the medullary cavity its packing full with bone cement starts. ( 2 ) The nurse assistant prepared the lump of bone cement in an open bowl. The toxic fumes of evaporating monomer substance were spreading freely into the atmosphere of the operation theatre during preparation of the doughy bone cement. In this picture the nurse has an astronaut dress, which by no means protect her completely from breathing in the toxic fumes. On operation theaters where one did not use the astronaut dresses the situation was even worse; the  concentration of toxic fumes inbreathed by nurses working with bone cement was much higher; these nurses (and other people around the fuming bowl) often complained of headache and dizziness.  Eventually authorities had to establish norms how much monomer fumes concentration was allowed in the the atmosphere of the operation theatres. These norms hastened the development of closed mixing apparatuses. ( 3) When the surgeon got the lump of the still doughy bone cement from the nurse he started immediately to pack it into the medullary cavity of the thighbone. The surgeon applied his two thumbs for packing the medullary cavity completely with bone cement. The curing time of bone cement is about 7 - 10 minutes.  Within this time the surgeon was forced to fill completely the whole medullary cavity with  bone cement and then place the shaft of the femoral component in the right position into the dough. The surgeon used his two thumbs. John Charnley describes in detail the technique stating what make the inside and the outside thumbs. In this picture, John Charnley chose red color for bone cement in this illustration. Although he ordained that bone cement should not be soiled with blood he perhaps knew that admixing of blood with this primitive technique was inevitable.

The modern, third generation cementing techniques may differ on individual hospitals, but in general the modern cementing procedure proceeds as follows:

Show Picture: Third generation cementing techniques

Results of cemented total hip replacements.

On the European continent the majority of surgeons still use bone cement for fixation of their total hips with these new cementing techniques, although their numbers are dwindling. In the USA, on the other hand,  some older surgeons scoff off the  young surgeons because they cannot longer use bone cement-"nobody learned them the technique".

 In Swedish National Hip register the cemented total hip models show actually three times less failures by aseptic loosening than the cementless ones (Malchau 2002).

Table

All models, 1990 -2001, ten years follow-up.

Failures of all models of cemented total hips	Failures of all models of cementless total hips
2.2%	6.5%

The cementless total hips are substantially more expensive and substantially more profitable for implant manufacturers. Exact cementing technique is on the other hand time demanding. Perhaps these two factors contribute more to the spreading of cementless total hips than the available results of their success.

_________________________________________

Haboush E: A new operation for arthroplasty of the hip based on biomechnics, photoelasticity, fast-setting dental acrylic, and other considerations. Bulletin Hospital for Joint Diseases 1953, 14: 242-277

Charnley J. : Acrylic cement in orthopaedic surgery. The Williams & Wilkins Company  Baltimore 1970

Charnley J.: Low friction arthroplasty of the hip. Springer 1979

Chen FS et al.: Results of cemented Metal-Backed Acetabular components. J Arthroplasty 1998, 13: 867- 73

Hungerford D.: Cement disease. Clin Orthop Rel Research 1987; 225: 192- 206

Judet R et al.: A noncemented total hip prosthesis. Clin Orthop Rel Res 1978; 137: 76- 84

Linder L.: Boneloc R the Christiansen experience revisited. Editorial.  Acta Orthop Scand 1995; 66: 205

Loupacis A et al.: J Bone Joint Surg Am 2002; 84-A: 1823 - 8

Malchau H. et al.: Prognosis of total hip replacement. Scientific Exhibition presented at the 69^th Annual Meeting of the AAOS, February 13-17, 2002, Dallas, USA

Malchau et al.: Prognosis of total hip replacement. Scientific Exhibition presented at the 63^rd Annual Meeting of the AAOS, February 22-26, 1998, Atlanta, USA

 Markel DC et al:  Cemented total hip arthroplasty with Boneloc bone cement.  J South Orthop Assoc 2001, 10, 202 -8

Riegels-Nielsen P et al.: Boneloc R Cemented total hip prostheses. Acta Orhop Scand 1995; 66: 215 -7

 Revised July 2007