Titanium Implant Impairment and Surrounding Muscle Cell Death Following High-Salt Diet: An In Vivo Study

Abstract

Aim of the study: High-salt consumption has been widely described as a risk factor for cardiovascular, renal and bone functions. In the present study, the extent to which high-salt diet could influence Ti6Al4V implant surface characteristic, its adhesion to rat tibial crest, and could modify muscle cell viability of two surrounding muscles, was investigated in vivo. These parameters have also been assessed following a NMES (neuro-myoelectrostimulation) program similar to that currently used in human care following arthroplasty.

Results: After a three-week diet, a harmful effect on titanium implant surface and muscle cell viability was noted. This is probably due to salt corrosive effect on metal and then release of toxic substance around biologic tissue. Moreover, if the use of NMES with high-salt diet induced muscles damages, the latter were higher when implant was added. Unexpectedly, higher implant-to-bone adhesion was found for implanted animals receiving salt supplementation.

Conclusion: Our in vivo study highlights the potential dangerous effect of high-salt diet in arthroplasty based on titanium prosthesis. This effect appears to be more important when high-salt diet is combined with NMES.

Fig 1. Design of the implant and NEMS device.

Rat is positioned in supination. Straps located on thorax and abdomen avoid any movement interference. Foot is firmly held and stimulation electrodes are positioned on the skin right above the first 1/3 of FD muscle. Implant location is represented from digitalized implant and tibial bone made using a Computer Assisted Design system.

Fig 2. Tensile test.

A homemade device is used to measure the adhesion load between the implant and the bone. Briefly, tibial bone is placed, implant downwards, on a flat metal bracket containing a hole allowing the implant to be loaded by a tension device. Highly resistant wire is passed through the implant hole then connected to the load system. The mobile part of the testing device is slowly displaced to stretch the wire until the implant loosened. Graphic in lower part indicates the time-curve of force recorded and the maximum load value obtained just before the breakout of the implant marked by a thin arrow.

Fig 3. Implant-to-bone adhesion.

Measurement of the maximum load value indicates that adhesion of the implants to the tibial crest bone is significantly (**: p<0.01) higher when implanted animals are submitted to high-salt diet (Ti-NaCl) compared to only implanted animals (Ti) or animals simultaneously submitted to high-salt diet and NEMS program (Ti-NaCl-Es).

Fig 4. Surface degradation of the implant.

The surface of the implant is scanned before and 3 weeks after implantation and the range between higher and lower surface point is measured. Results indicate that the Ti-NaCl (implanted and submitted to high-salt diet) and Ti-NaCl-Es (implanted and simultaneously submitted to high-salt diet and NEMS program) groups present a significant higher (*: p<0.05) degradation of implant compared to Ti (non submitted to high-salt diet and NEMS program) group.

Fig 5. Muscle damages.

Antibodies directed against activated caspase 3 are used on flexor digitorum and tibialis anterior muscles to evaluate cell death rate (number of dead cells per surface unit). No significant muscle damage is observed between muscles in each group. Furthermore, significant differences between Control and other groups are indicated by * for flexor digitorum and + for tibialis anterior (*** and +++, p<0.001). δ indicates significant intergroup differences for both muscles (δδδ, p<0.001).