# Does Pressurized Carbon Dioxide Lavage Improve Bone Cleaning in Cemented Arthroplasty?
## 4 Discussion  
The use of pulsatile lavage is known to enhance the fixation of cemented total knee arthroplasty [38]. Highly significant improvements of cement penetration into cancellous bone can be demonstrated in vitro comparing manual rinsing and pulsed saline lavage [25]. In addition, cleaning of cancellous bone leads to improved cement penetration and therefore to a stronger bone cement interface, which reduces the probability of aseptic loosening [18; 39]. However, aseptic loosening is the main reason for revision in cemented total knee and hip arthroplasty [12; 13]. Modern cementing technique requires pulsed saline lavage, drying bone by abdominal cloth and suction, drilling holes in the tibia and applying vacuum-mixed-cement either on both, metal and bone in total knee arthroplasty, or filling the femur in retrograde technique using a cement gun in total hip arthroplasty. Considering this, many factors besides the cancellous bone cleaning result can affect cementation. Bone density or sclerotic bone also can cause reasonable differences [40]. Cement storage temperature, humidity, cement viscosity or timing of cement application are other aspects that have to be considered [41; 42]. Figure 6: Volume of removed grease in standardized carbon foam specimens. Figure 7: Cleaning depth in mm in standardized carbon foam specimens. In our experimental in vitro study, we compared a standard high-pressure pulsatile saline lavage to a novel lavage system using compressed carbon dioxide to enhance cleaning efficiency of cancellous bone under standardized conditions. Cancellous bone was simulated by standardized fat-filled carbon foam. In this experimental setup, impact pressure was applied to a force-measuring-plate. We detected significantly higher pressures in pulsatile saline lavage (InterPulse) than in pressurized carbon dioxide lavage (CarboJet). Although we showed higher cleaning volume and deeper penetration in carbon foam, when using carbon dioxide lavage additionally to high-pressure pulsatile saline lavage (Group C) these differences were not significant. Similar results were obtained for the single use of carbon dioxide lavage (Group B) in comparison to the single use of pulsatile saline lavage (Group A) (Figures 6 and 7). So far, there is only limited data available about carbon dioxide lavage. A cadaveric study in 10 knees in 2016 demonstrated that a combination of pressurized carbon dioxide and common pulsatile saline lavage produced a significantly deeper bone cement penetration than saline lavage alone [30]. In addition, another study demonstrated that bone cement interface was stronger [32]. In 2019, [PERSON] et al. revealed that using sterile compressed carbon dioxide in addition to the established pulsatile jet lavage, resulted in a deeper cement penetration in six of seven defined zones (Knee Society Radiographic Evaluation System) in 303 total knee endoprostheses. This difference was significant in three out of seven zones [31]. In this standardized laboratory setup, which was established in earlier studies [35; 36], no significant difference between the three experimental groups was detected although higher cleaning volumes and cleaning depth using additional carbon dioxide lavage (Group C) was discovered. In this study the aspect of preparing bone bed prior to cementation was investigated. Other aspects such as pressure during cementing, viscosity of cement, remaining blood or fat in the interface or the timing of cement-application were excluded from the investigations. With this test setup, the ability of carbon dioxide lavage to clean cancellous bone was examined closely. Whether or not the slightly enhanced cleaning ability will result in deeper cement penetration remains uncertain. The use of additional carbon dioxide lavage needs extra devices, sterilization and carbon dioxide gas cylinders, which need adequate storage and the exact following of safety instructions. Moreover, the additional time needed for the procedure extends duration of operation and time of anesthesia.