Cemented Total Hip Arthroplasty With Boneloc Bone Cement

David C. Markel, MD, Daniel B. Hoard, MD, Charles A. Porretta, MD


J South Orthop Assoc. 2001;10(4) 

In This Article

Abstract and Introduction

Boneloc cement (WK-345, Biomet Inc, Warsaw, Ind) attempted to improve cement characteristics by reducing exotherm during polymerization, lowering residual monomer and solubility, raising molecular weight, and lowering airborne monomer and aromatic amines. To study the efficacy of this cement, a selected group of 20 patients were prospectively enrolled and followed up after hip arthroplasty. All components were cemented. During the enrollment period, approximately 70 other hip arthroplasties were performed. Clinical evaluation was based on the Harris hip score. Radiographic evaluation was based on assessment of position of the components, subsidence, and/or presence of radiolucencies. Patients had follow-up for an average of 42 months (11 to 58 months); 1 was lost to follow-up. Of these, 7 (35%) had failure at last follow-up. Despite its initial promise, Boneloc cement had an unacceptably high failure rate over a relatively short follow-up period and is not recommended for use. Despite the longevity and odor toxicity problems with conventional bone cement, new cement technologies must be approached with caution.

Cemented hip arthroplasty has been performed since the late 1960s.[1] It became clear over the ensuing years that cemented arthroplasties had a limited longevity and that the mechanical construct would fail via a process of aseptic loosening. In addition, a number of less than desirable characteristics were noted. The fumes of the polymerizing cement were found to be noxious to the operating room staff, and the exotherm of the polymerizing cement was potentially damaging to the bone. To address these concerns, several implant manufactures developed or are developing newer cement technologies.

In 1986, development was begun of a new bone cement, which was later marketed by Biomet Inc (Warsaw, Ind) as Boneloc. The first objective for Boneloc was to create a cement equal to or better than conventional methyl methacrylate/polymethyl methacrylate in both efficacy and longevity. The second objective was to create a product that was safer for operating room personnel.

By decreasing the chemical and thermal damage to bone during implantation, it was believed that the clinical efficacy of conventional polymethyl methacrylate could be improved. It was hoped that by preventing bone necrosis at the bone-cement interface the mechanical grouting action of the cement would be better preserved and perhaps improve the longevity of the construct. Therefore, the first goal was to reduce the exothermic temperature generated during cement polymerization, lower the residual monomer content, and create a product with both a lower solubility and a higher molecular weight. The second objective was protection of operating room personnel. Nursing staff have been noted to complain about the odor of cement and have anecdotally associated exposure to cement fumes with headache, nausea, and/or dizziness. While there is no clear evidence that the cement fumes are teratogenic, pregnant nurses are often not used to staff joint replacement procedures done with cement at many hospitals, including ours. Thus, the second objective would be accomplished by lowering the residual content of the airborne monomer and aromatic amines, as well as containing the noxious airborne material by modifying the cement delivery system.

The resultant Boneloc cement consisted of a two-component self-curing system. The powdered polymer component consisted of butylmethyl methacrylate copolymers in a ratio of 40%:60%. The liquid monomer component contained 50% methyl methacrylate, 30% n-decyl methacrylate and 20% isobornyl methacrylate. An integrated packaging, mixing, and delivery system was developed to minimize operating room staff exposure to the monomer vapor. The system used a double-chambered high-density polyethylene cartridge into which the two cement components were packeted. Within the chambers, an aluminum membrane separated the monomer and polymer. When the separating aluminum membrane barrier was broken, the polymer and monomer mixed, yet the entire process was kept isolated from the operating room environment and staff. Initial reports noted difficulty with the mixing and cement delivery. Therefore, in 1993, a more conventional vacuum mixing and delivery system replaced the cartridge system.

Analysis and evaluation of new technology is, of course, important and is required in the United States by the Food and Drug Administration. The index study and patient population were based on participation in the United States' Boneloc cement Investigational Device Exemption during the years 1991 to 1993. We present the results of the cemented total hip arthroplasties done at our institution.