and C.W.


Abstract-The use of acrylic cement in orthopaedic surgery has expanded the surgeon’s ability to achieve a rigid and immediate fixation in some difficult pathological fractures. The term ‘pathological’ in this context indicates a fracture occurring through an area of bone with loss of substance as the result of invasive nrocess (Ball et a/.. 1973: Enis (‘1ul.. 1973: Harrineton. 1972: Sim CI al.. 19731 Self-curing cement is gcnerall~ used in con.ju&ion with conventional metallic devices. If the acrylic cement was supplemented. the prtmar) goal would be a rigid immobilization of the fracture to alleviate the pain: usually. however. the final aim is toward osteosynthesis. During the course of rehabilitation. it is often desirous to supplement the treatment by irradiation. Although the industriaL dental and surgical literature has adequately dealt with many aspects of bone cement; for example, physical and chemical properties in joint replacement and so on. the effects of irradiation on the acrylic cement has not been previously reported:. It is the purpose of this paper to analyze the experimental studies conducted lo evaluate the mechanical properties of the polymethylmethacrylate when subjected to irradiation within a maximum range of a therapeutic dose.



A 68 yr-old man was admitted because of progressive left hip pain over a two-week period. He was previously well. On examination. any attempt at motion was painful and he was unable to bear weight. The remainder of the physical examination was essentially negative. Laboratory data was within normal limits. Xray of the proximal left femur showed a large radiolucent lesion in the intertrochanteric region and chest Xray also showed a small mass in the right upper lobe. Following a needle biopsy of the femoral lesion which proved to be metastatic papillary adenocarcinoma, the patient underwent curettage of the lesion and internal fixation of the fracture with a Smith-Petersen nail and McLaughlin plate using methylmethacrylate to fil3 the bony defect. Postopkratively. the patient was pain-free and was permitted weight-bearing as early as two weeks after surgery. Over a period of 4 weeks. the patient received radiation therapy to the area of the hip joint using a total of 4500 r cobalt therapy. He was totally symptom-free in regard to his hip and had resumed full weight-bearing three weeks following his surgery. Six months after surgery. there was evidence of callus formation and fracture repair. * Rrcriued 15 April 1974. t From Department Orthopaedic

Surgery and Orthouaedic Research Laboratories. College of Physicians and kurgrons. Columbia University. and Carleton Material Laboratories. Columbia University. New York. U.S.A. $ Associate Professor Orthopaedic Surgery. College of Physicians and Surgeons. Columbia University. ColumbiaPresbyterian Medical Center. New York 10032. U.S.A. 3 Associate Professor Architecture. Graduate School of .4rchitecture and Planning. Columbia University. New York. V.S.A. IINorth Hill Plastics Inc. London. England. q C M W Laboratories Ltd.. Blackpool. England.

Case No. 2 (Fig. 2) A 75 yr-old woman sustained a pathological fracture of the right femur. She was known, by previous biopsy, to suffer from reticulum cell sarcoma. In the presence of a large bony defect approximately 8 q and severe comminution, it was necessary to supplement the internal fixation device by acrylic cement. Following surgery, the patient received a total 45OOr. using cobalt 60. Fixation of the fracture has remained unchanged one year following radiation to the site. THE ACRYLIC CEMEhlT

Acrylics have been known io man for over a century. The clinical use of cold-curing acrylic cement for intramedullary fixation of prostheses was popularized bq Charnley ( 1970). There are several commercial acrylic products available; for example. the Simplex P Radiopaquell and C M w bone cements. commonly used in the U.S. and Great Britain. The basic chemistry and mechanical properties of Simplex P acrylic cement have been determined by several investigators (Charnley, 1970; Homsy et al.. 1972; Lee et al.. 1971). and are given in Table 1. The acrylic cement is supplied in its prepolymerized form of liquid monomer and finely graduated polymethylmethacrylate powder (Amstutz tif al.. 1973). Barium sulfate is added to enable the surgeon to evaluate the quality and quantity of the cement in the bone after application. In order to determine values of the mechanical properties of the cements under local conditions. further testing was conducted in our laboratories. MECJ-JANJCALTESTING: METHOD AND MATERIAL

Tests were conducted for both the C M W and Simplex cements with and without barium sulfate. All tests were performed in the Carleton Materials Laboratorv.




Table 1. Chemical constituent of basic components Simplex P Radiopaque cement Liquid


V/V 97.Q/o

Methylmethacrylate (monomer) N.N-dimethyl-para-toluidine (accelerator) Hydroquinone (stabilizer)

2.6% Trace

Columbia University, at various times during May and September 1971. No attempt was made during fabrication to keep the mixed material in sterile condition.

Some of the test specimens were irradiated before testing to note the effect of irradiation with the range of a tumor dose. A maximum of 10,OCMIrwas felt to be a maximum single dose for simulation of a human subject (Table 2). The material from which the test, skimems were made was secured from vendors in unmixed two component forms, polymer powder and liquid monomer, in premeasured amounts of 40g powder and 20cm3 liquid. Mixing was done by hand in a small stainless steel bowl, according to recommended practice, using an ordinary tablespoon as the mixing tool. Where barium sulfate was included, 5 g per mix in powder form it was added at the start of mixing. The components were blended and vigorously stirred for as .long as practical, two to two and one-half minutes for the Simplex, and about one and one-half minutes for C M W, stopping only when it was judged that just sufficient time remained to mold the mix while it was still adequately plastic. Specimens were molded by hand in molds machined from Teflon stock. The size of all molds was sufficiently rigid to yield uniform size of test specimen. For cylindrical torsion and compression test specimens, the molds were open-ended tubes permitting the plastic mixture to be forced through by finger pressure as in-an extrusion process. For the tension and flexure specimens the molds were open-top rectangular containers into which the mixture was simply placed by finger pressure. Heat of polymerization, a factor in handling the mixture, did not necessitate any particular procedure because of excessive temperature. The procedures of mixing the co_mponents of the plastics and molding the specimens were purposefully left unmechanized in order to simulate as nearly as possible current operating room techniques. In order to reflect fully the range of values which might be expected under comparable circumstances, the results given are for all but six (I5 per cent) of the

Polymethylmethacrylate (polymer) Copolymethylmethacrylate (styrene) Barium sulfate

total of all specimens which were molded. These six were among the first specimens formed and contained obvious defects; large air bubbles at critical test sections, resulting from inexperienced handling technique; these were rejected outright. Some later test specimens also contained air bubbles which were either visible before testing or became evident in the fracture surface after testing No trend was indicated however, of weakness of the specimens containing these noticeable bubbles when their results were compared with the average for their fellows. Specimens were removed from the molds as soon as sufficiently rigid normally well within an hour of forming. These specimens were machined in lathes and millers, as needed to provide regular surfaces and standard sizes. Those samples which were irradiated were subjected to the exposure detailed in Table I before testing. Various periods of time elapsed between the molding and testing of specimens, generally from 4 to 6 days for specimens not irradiated and near 20 days for the irradiated specimens. Compression, torsion, Rexure and tension tests were conducted on the several test specimens. For those tests for which appropriate ASTM standards exist. the shape of the test specimens and the testing arrangements conform to such standards. All tests were conducted at normal laboratory speeds for ‘static’ loading on standard laboratory testing machines using conventional- test setups. Test specimen dimensions and arrangements for testing are shown in Fig. 3. RESULTS

Test results are given in Tables 36. The results from representative tests are illustrated in Fig. 4. The results of the tests were in general agreement, establishing the following values for irradiated and non-irradiated specimens. Coinprrssiort

Ultimate compressive strength, psi Young’s modulus. ksi (approx.)

Table 2. X-ray data KVP 184 Double tube Output in air Average dose per exposure Total number exposure Total exposure time

MA 30

T-S Distance 46 cm

5OOr 10.000 r (measured in air)

Filtration Cu 0.28 mm Al 0.5 mm

1 20 min

11,000 280

EfTect of irradiation

on acrylic

Table 3. Flexure






3 3

c c

3 3




3 ?



? 3


J hr 5 days 4 hr I day 5 days 5 days 5 days 20 days 30 days 20 days 20 days

* *

* *

* * * *

‘66 274 256 256 269 307 297 295 ‘8’ JO; 2X8

302 299 274 309 310 320 307 314 316 307 301

‘85 290 264 286 ‘88 314 303 301 298 305 292


6’40 6430 61Oi) 6910 7390 6530 6140 8600 6140 7390 6X70

Table 4. Compression

3 2 ;,

S S S s

1 hr: I da) 43 days days

s S c c C S C c s s S C S C

67 days I da) 3 days 6 days 6days I da> 6days 4 days 7 days 21 days 21 days 21days 2ldays

, Y I 4 2 2 2 ? ; I 2 2 3 2

I -I





* * *

* *

2 days 3 days 4 days 14 days I7 days I7 days I4 days I7 days

1 * * * * *

9020 9500 8160 8540 XX30 79x0 7200 9600 75X0 86Ml 7900

7500 8070 72x0 7740 7970 7430 6750 9IwJ 6850 x030 7470

7660 7430 6750 9100 6850 8030 7470

7680 7090 7990 7750

11.900 9800 9850

12.100 1 I.200 9960

12.000 10.500 12.400 9900



10.930 13.100 1 t.400

1 I.300

11.160 11.080 11.750 IO.610 12.300 13.300 IO.620 9840 11.800 9750

IO.700 I I.100

1 I.100

I I.200

I I.100





273 239

236 260 280 239 280

266 270 282 239 ‘80

265 ‘81 ‘39 280

9960 il.140 11.020 11.000 IO.550

10,560 1I.190 1 I.140 12.500 IO.670

271 259 293 221

‘77 260 303 ‘57

274 260 298 239

IO.560 9610 11.740 9660

10.680 10.080 Il.860 9840

9500 10.200 1 I.300 13.400 12.700 7cQo Il.900 8600




* *



11.700 9800 II.800 9800

I I.200 7000




I I.100







Table 6. Tension tests

3 3

6 days 6 days

3030 2420


Modulus of rupture, psi Young’s modulus. ksi (approx.)

7640 290.


Ultimate tensile strength psi


Torsion 10.500. Modulus of rupture. psi Within each type of test, agreement was generally good. The weaknesses and the strengths of the various values reported appear to be by batch, reflecting variations in mixing techniques, rather than by treatment. For the most part, the fluctuations are well within 10 per cent above and below the average values, a spread fully anticipated for such test specimens and procedures. In the flexure tests there is a possible trend indicating that one material outperformed the other but. again, the variations determined are too small to be meaningful.


Polymethylmethacrylate is an excellent adjunct in fixation of pathological fractures. Based upon its mechanical properties, it cannot be substituted for bone; however. when used in conjunction with conventional nail. plate or screw fixation methods. it provides an immediate rigid fixation of some difficult pathological fractures. Tests were undertaken to determine the mechanical properties of two commonly used bone cements; Simplex P Radiopaque and C M W. and the effect, if any, of irradiation upon the acrylic cement. We conclude from this study that there was no significant difference in mechanical properties of irradiated and non-irradiated cement and that postoperative irra-

3390 5220

3200 4050


diation may be safely used after fixation of pathological fractures without fear of adverse effect on the mechanical properties of the cement. Acknowledgements-The authors wish to extend their gratitude to Dr. E. J. Hall and Miss Laurie Roizin. of the Radiological Research Laboratory. College of Physicians and Surgeons. Columbia University, for their assistance. Special thanks are due also to Mr. George Anderson and Mr. Jacob Varghese, of the Carleton Materials Laboratory. for their technical help in preparation and testing of the specimens. REFERENCES Amstutz. H. C. (1973) Clinical application of polymethylmethacrylate for total joint replacement. (Edited by Ahstrom. J. P.. Currer~t Pructicr irt Orthopdic Surgery, Vol 5. Mosby. New York. Ball, R. M., Dick. H. M. and Stinchfield F. E. (1973) Acrylic cement as a supplement in internal fixation of pathological fractures. Proceedings J. Bone Jr Surg. SSA. 1317. Charnley, J. (1970) .4crr/ic Cettrr~~titt Orrhopaedic Swger.v. Williams & Wilkins: Baltimore. Enis, J., Marshall, H. and Sarmiento. A. (1973) Methylmethacrylate in neoplastic bone destruction of the hip. Proceedings First Open Scientific Meeting Society. p. 118. Mosby. New York.

of The Hip

Harrington, K. D., Johnston. J. 0.. Turner, R. H. and Green D. L. (1972). The use of methylmethacrylate as an adjunct in the internal fixation of malignant neoplastic fractures. J. Bone Jnt Btrg. S4A, 1665. Homsy, C. A., Tulles, H. S.. Anderson. M. S.. Diferrante. N. M. and King, J. W. (1972) Some physiological aspects of prosthesisstabilization withacrylic polymer. Clin. Orthop. 83, 317. Lee, A. J. C., Ling, R. S. M. and Wrighton. J. D. (1971) Mechanical properties of methylmethacrylate cement. Proceedings. British Orthopaedic Association. Belfast. 1971. 1. Bone Jnt Surg. 53B. 759. Sim F. H. and Daugherty, T. W. (1973) Methylmethacrylate as an adjunct in internal fixation of pdtho(ogicaf fractures. J. Bone Jnt Surg. 55A. 1317.

Effect of irradiation on acrylic cement with special reference to fixation of pathological fractures.

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