[Status of cementation technique in total hip endoprostheses in Germany]

Amphiphilic bonder improves adhesion at the acrylic bone cement-bone interface of cemented acetabular components in total hip arthroplasty: in vivo tests in an ovine model

INTRODUCTION

Even following the introduction of the "third generation" cementing technique, an improvement of the fixation of the acetabular component similar to that of the femoral has not been shown in clinical studies. The goal of the present study was to achieve a better stability with the use of an amphiphilic bonder while preserving the mechanically important subchondral sclerosis.

MATERIALS AND METHODS

In a total of 20 sheep, a cemented total hip replacement was implanted. In the treatment group (n = 10), the implantation was carried out following surface conditioning of the acetabular bed with an amphiphilic bonder. All the sheep were followed for 9 months. To assess the biocompatibility, the osseous ingrowth at the cement-bone interface was depicted with the help of an in vivo fluorescent marking of the osteoblasts. Additionally, conventional radiographs were obtained over the course of treatment. Finally, the ovine pelvic regions were split following a standardized technique allowing for histological evaluation of the cement-bone interfaces.

RESULTS

The acetabular components of the treatment group revealed a stable cement-bone compound. In the control group, the implants were easily dislodged from their beds. This finding was consistent with the radiological and histological results, which had revealed increased, progressive lytic radiolucent lines and the interposition of fibrous tissue at the cement-bone interface in the control group compared to the treatment group. The bonder was biocompatible.

CONCLUSION

Following the application of the bonder, the cemented acetabular components revealed an improved stability without signs of inflammation or neoplasia in a viable acetabular osseous bed. With the help of this technique, the in vivo longevities of cemented acetabular components can be increased in the clinical setting without sacrificing the biomechanical relevant subchondral sclerosis.

Einfluss der femoralen Zementiertechnik auf das Zementierergebnis

METHODS

To evaluate the penetration depth of cement into trabecular femoral bone, femora of 14 sheep were subjected to simultaneous bilateral cementing. After femoral neck osteotomy, preparation of the bone cavities and jet lavage, cement was applied simultaneously using the conventional retrograde method for one side and vacuum application for the contralateral limb. Bilateral simultaneous pressurisation was then applied. All femoral specimens were X-rayed, sawed into standardised, horizontal, stereometric, identical slices and microradiographed. Cement penetration was assessed using a morphometric software system.

RESULTS

No significant differences in depth of cement penetration between sheep femora cemented with the vacuum application method and the standard retrograde method could be found or between the ratio of cement-consolidated and non-cement-consolidated cancellous bone.

CONCLUSION

The more complicated and technically challenging method of cement application under vacuum had no advantage in terms of cement interdigitation over the standard retrograde method.

Clinical development and current status: Europe

This article reviews the development and current status of cemented fixation in total hip replacement in Europe. Key points include the wide country-to-country variation in use of cemented vs. non-cemented fixation and the largely overlooked importance of the choice of bone cement as a factor highly correlated with clinical outcome. Laboratory studies by the authors are also reviewed. Results suggest that the type of acrylic bone cement used affects wear phenomena at the implant/cement interface. Further studies by microcalorimetry suggest that certain aspects of acrylic starting materials (low molecular weight and use of radiation sterilization) affect long-term physico-chemical stability and may thus influence clinical outcomes.

In vitro performance of intramedullary cement restrictors in total hip arthroplasty

Contemporary cementing techniques in total hip arthroplasty include the use of a cement restrictor to occlude the intramedullary canal. As there are many different designs currently available it was the aim of our study to compare the stability of eight different systems. We investigated the displacement and the ability to occlude the femur of these cement restrictors during standardised cementing of artificial and fresh frozen femora. The maximal intramedullary pressures and the displacement of the plugs were continuously recorded and statistically evaluated. The results revealed significant differences between the tested cement restrictors. The expandable REX Cement Stop and the Exeter Plug achieved the highest stability and the least cement leakage. The more rigid designs (Palacos Plug, BUCK, Universal) in contrast showed inferior performance. Our biomechanical study emphasises the importance of cement restrictor selection, which can have a crucial influence on the fixation of a cemented total hip replacement.

Lavage technique in total hip arthroplasty: jet lavage produces better cement penetration than syringe lavage in the proximal femur

Sixteen paired human cadaver femora were prepared using conventional broaches. Cancellous bone was irrigated with 1 L pulsed lavage in one femur and 1 L syringe lavage in the contralateral femur. The specimens were embedded in specially designed pots, and vacuum-mixed bone-cements were applied in a retrograde manner. After application of a standard pressure to the pots, the femora were removed and radiographed, and horizontal sections were obtained and analyzed to assess cement penetration into cancellous bone and the ratio of the area of supported to unsupported cancellous bone (Rcb). Our results show that in equal quality bone, the use of jet lavage yields significantly (P < .0001) improved cement penetration and Rcb compared with syringe lavage specimens. Jet lavage should be considered routine to achieve interdigitation with cancellous bone in cemented total hip arthroplasty.