Extensive localized bone lysis in the femur following implantation of a metal-on-metal total hip prosthesis was observed. Fragmentation of the cement occurred 10 years after implantation. Histologic and ultrastructural features of macrophages are consistent with the hypothesis that particles from the acrylic resin were the factors stimulating the macrophagic reaction. Both mechanical factors and changes of the physico-chemical properties of the cement may have an etiologic role

Pazzaglia UE.

PAZZAGLIA, Ugo

Archivio istituzionale della ricerca - Università di Brescia

Arch Orthop Trauma Surg (1989) 109 : 49-52 Archives of o Orthopaedic andTrauma Surgery © Springer-Verlag 1989 Fragmentation of methylmethacrylate: A cause of late failure of total hip replacement A case report U. E. Pazzaglia Clinica Ortopedica dell' Universit~ di Pavia, IRCCS PolMinico San Matteo, Via Taramelli 3, 1-27100 Pavia, Italy Summary. Extensive local ized bone lysis in the femur fol lowing implantat ion of  a meta l -on-meta l  total  hip prosthesis was observed.  F ragmentat ion  of the cement  occurred 10 years after implantat ion.  Histologic and ultrastructural  features of macrophages are consistent with the hypothesis  that part ic les f rom the acrylic resin were the factors st imulat ing the macrophagic  react ion. Both mechanical  factors and changes of the physico- chemical  propert ies  of  the cement  may have an etiologic role. A fore ign-body react ion to part ic les re leased from the total  hip rep lacement  is a common cause of implant  fail- ure. Histological ly,  po lyethy lene and metal l ic debris are easi ly identi f ied,  but  no direct evidence of methyl-  methacry late  in the tissues is possible. F ragmentat ion  of the acrylic cement  produced,  in this case, an extensive, local ized bone lysis in the femur  and al lowed a study of the tissue response to this type of mater ia l  debris. Case report A 70-year-old man had a right total hip replacement in 1975 for severe osteoarthritis. There was no history of infection or trauma; osteoarthritis was present in the controlateral hip. A metal-on- metal McKee-Farrar prosthesis was inserted and fixed with Simplex P bone cement which did not contain barium sulphate. The postoperative course was uncomplicated and the patient re- gained excellent function of his hip. Five years later, total hip re- placement was carried out on the left side. The patient was satisfied with the results of the operation until September 1985, when he started to complain of pain in his right thigh. Roentgenograms taken in May 1986 showed osteolysis of the cortical bone at the level of the tip of the stem. The bone had been normal in control radiograms 1 year earlier (Fig. 1 a, b). The patient refused revision or other surgical diagnostic procedures. ESR, leukocyte count, serum proteins, electrophoretic pattern, acid and alkaline phosphatase, and chest radiograms were normal. There was no other evidence of infection or neoplasm. The patient was advised to walk with a cane. On July 1986 he was admitted for a fracture of the femur localized in correspondence to the osteolitic process (Fig. lc). Lab- oratory tests were normal with no evidence of infection. Revision was performed through an anterolateral pproach. Both the cup and the stem were not loosened and it was necessary toopen a win- Fig. 1. a No lysis was present in the femur 10 years after prosthesis mplantation. b Extensive, localized bone resorption developed from the 10th to the l l th  year, leading to femoral fracture 2months later (e) 50 U.E.  Pazzaglia: Methylmethacrylate fragmentation i  hip replacement failure dow in the anterior cortex to remove the stem and the cement from the proximal fragment of the femur. The osteolytic area at the site of the fracture was filled with a grayish-yellow, firm tissue which was curetted and examined histologically. Cultures of the material were negative. The distal cement of the stem was very brittle, and pulverized when it was touched. However, the cement of the cup and that of the proximal stem was of normal consistency. A long-stem Charnley prosthesis was inserted and the defect in the femur filled with acrylic cement; the window in the anterior cortex was tightened with Partridge plastic bands. After the opera- tion, weight bearing was restrained, but after 2 months a disloca- tion of the head of the prosthesis was observed. In February 1987, revision was carried out and a new stem inserted. After 3 months, walking with a cast was allowed. Specimens from the osteolytic area were fixed with neutral for- malin (10%), routinely processed, and stained with hematoxylin- eosin. Cortical bone was decalcified in EDTA before embedding. X-ray energy-dispersive analysis was performed on routine sec- tions after removal of the coverslip and observation with the scan- ning electron microscope. Specimens for transmission electron mi- croscopy were fixed in 4% glutaraldehyde, postfixed in 1% os- mium tetroxide, and embedded in Epon. Sections were stained with uranyl acetate and lead citrate. Pathological findings Most  of  the  soft t issue curet ted  f rom the osteolys is  con-  s isted of  a sheet  of  macrophages  wi th  a c lear  granu lar  cytop lasm;  f ibr in and hemorrag ic  and necrot i c  mater ia l  were  also present .  Fore ign-body  giant cells were  associ-  U. E. Pazzaglia: Methylmethacrylate fragmentation in hip replacement failure 51 Fig. 2. Irregular contour of the endosteal surface: osteoclasts are present, but most of the old resorption lacunae are occupied by macrophages or by active osteoblasts (right side of the figure). HE, × 86 Fig. 3. a Macrophages lining the bone surface; the cells have a clear and granular cytoplasm, but no particles were identified by polari- zed-fight examination or by analytical methods, b Bone is invaded by macrophages through vascular canals; these cells are observed either in the vessel lumen (empty arrow) or between the bone and the endothelial wall (full arrows). HE, × 340 Fig. 4a, b. Section of the cortex at the level of the osteolysis: bright field (a) and polarized light (b). The endosteal surface of the cortex has undergone xtensive resorption and presents a "moth- eaten" aspect. Two layers of periosteal pposition are evident: the inner represents a reaction to endosteal resorption (the bone is denser and remodeling more advanced); the outer is periosteal cal- lus of the fracture. HE, x 21 Fig. 5. Large, secondary l sosomes are present in the cytoplasm of macrophages. The negative image of the material contained inside the lysosomc appears as a globular, electron-transparent area (ar- rows). TEM, × 80000 ated with globular, empty spaces from 100 ~tm to 1 mm in diameter. No opaque particles nor birefringent material were observed in any of the sections. Neither metals nor barium were detected by X-ray energy-dispersive analy- sis. There were no inflammatory cells. The cortex of the femur was very thin, with an irregular inner surface and many resorption lacunae. Osteoclasts were numerous but osteoblastic activity was also present (Fig. 2). The sheet of macrophages filled inactive resorption lacunae and penetrated into all the cavities present on the inner surface of the cortical bone (Fig. 3 a). Invasion of the haversian canals was a constant finding, and mac- rophages were observed both inside vessels and outside the endothelial wall, in direct contact with the bone (Fig. 3b). Periosteal apposition was very active and the outer cortex was formed by a layer of trabeculae oriented perpendicular to the circumference of the di- aphysis (Fig. 4). Ultrastructurally, the cytoplasm of the macrophages presented large, secondary lysosomes which contained an electron-dense material, but also radiotransparent areas suggesting the negative image of a globular material (Fig. 5). Discussion Four cases of extensive, localized bone resorption in the femur following total hip replacement have been report- ed by Harris et al. [4]; in the same paper, these authors mention that they have knowledge of 11 other cases. Carlsson et al. [1] observed localized endosteal resorp- tion in 33 total hip replacements from a series of 70 revi- sions carried out for aseptic loosening. Probably, this phenomenon is more common than is generally recog- nized. The report of this further case is prompted by a combination of factors: 1. A metal-on-metal prosthesis allows the exclusion of polyethylene as an agent stimulating a macrophagic reaction. 2. The sequence of events in this case shows a very rapid resorption of the bone after a period of 10 years, in the course of which no adverse reaction was observed. Extensive, localized lysis of the bone is commonly ob- served in the presence of infection, but this seems un- likely in this patient, who had normal ESR and white cell count, negative cultures, and no inflammatory reaction in the histological sections. A macrophagic reaction is the common response to the release of different classes of particulate materials from implants [2, 5, 6, 8, 9] and the cause of bone re- sorption when granulation tissue accumulates in the space between the implant and the bone [10, 11]. Re- lease rate, number, and size of the particles are critical factors controlling the intensity of the macrophagic reac- tion [7]. Polyethylene particles have no role in this case, and the same holds true for metallic particles, since no opaque structures were observed in the cytoplasm of macrophages and X-ray energy-dispersive analysis was  negative. Direct, histologic demonstration f radiotrans- parent cement is not possible because small fragments are dissolved in processing the specimens. However, the granular aspect of the macrophage cytoplasm and the radiotransparent material in lysosomes are consistent with the hypothesis that the material stimulating the macrophagic reaction was methylmethacrylate. I  is fur- ther supported by the operative findings of cement frag- mentation in the cases of Harris et al. [4] and in the one reported here. In contrast to what Carlsson et al. [1] ob- served, the tip of the stem was completely enveloped by the cement and the osteolysis extended symmetrically on both the inner and the outer cortex; therefore, no direct metal-bone contact may be advocated as the cause of bone resorption. The particles may have a wide range in size: in the case studied they were small and had the appearence of a powder. To our knowledge, this has not been reported before and can explain the intense macrophagic reaction and the rapid, lytic evolution of the granuloma. Self-curing acrylic cement may be considered a com- posite material, where granules of polymer are bonded together with recently polymerized monomer [3]; frag- mentation of the cement may release the interlocking polymer in the form of a powder, as well as granules, which are observed in the tissues as spheres or large shreds in the wider size range (more than 100 gm). Radiographic records in this case allow us to date the phenomenon of fragmentation to 10 years after implan- tation; its cause remains obscure, but at least two hypo- theses can be suggested: 1. Aging, with changes in the physicochemical proper- ties of the resin; 2. mechanical factors. 52 U. E. Pazzaglia: Methylmethacrylate fragmentation in hip replacement failure The observation of fragmentation i a limited area of the cement coating favors the latter or a combination of both. References 1. Carlsson AS, Gentz CF, Linder L (1983) Localized bone re- sorption in the femur in mechanical failure of cemented total hip arthroplasties. Acta Orthop Scand 54: 396-402 2. Charnley J (1970) Acrylic cement in orthopaedic surgery. Livingstone, London, p 23 3. Charosky CB, Bullough PG, Wilson PD (1973) Total hip re- placement failures (a histological evaluation). J Bone Joint Surg [Am] 55 : 49-58 4. Harris WH, Schiller AL, Scholler JM, Freiberg RA, Scott R (1976) Extensive localized bone resorption in the femur fol- lowing total hip replacement. J Bone Joint Surg [Am] 58 : 612- 618 5. Mirra JM, Amstutz HC, Matos M, Gold R (1976) The pathol- ogy of the joint tissue and its clinical relevance in prosthesis failure. Clin Orthop 117 : 221-240 6. Pazzaglia UE, Ceciliani L, Wilkinson MJ, Dell'Orbo C (1985) Involvement of metal particles in loosening of metal-plastic total hip prostheses. Arch Orthop Trauma Surg 104:164- 174 7. Pazzaglia UE, Dell'Orbo C, Wilkinson MJ (1987) The foreign- body reaction in total hip arthroplasties. A correlated light-mi- croscopy, SEM, and TEM study. Arch Orthop Trauma Surg 106: 209-219 8. Revell PA, Weightman B, Freeman MAR, Vernon-Roberts B (1978) The production and biology of polyethylene wear de- bris. Arch Orthop Trauma Surg 91 : 167-181 9. Vernon-Roberts B, Freeman MAR (1977) The tissue response to total joint replacement. In: The scientific basis of joint re- placement. Pitman, Bath, pp 86-130 10. Willert HG (1973) Tissue reaction around joint implants and bone cement. In: Chapchal G (ed) Arthroplasty of the hip. Thieme, Stuttgart, pp 11-21 11. Willert HG, Ludwig J, Semlitsch M (1974) Reaction of bone to methylmethacrylate fter hip arthroplasty. A long-term gross, electron-microscopic and scanning electron microscopy study. J Bone Joint Surg [Am] 56 : 1368-1382 Received February 27, 1989 

Fragmentation of methylmethacrylate: a cause of late failure of total hip replacement. A case report.

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