Hydrogen peroxide damages some implant materials

One minute of submersion in a 3% HO solution caused surface cracks on titanium and hydroxyapatite samples.

Hydrogen peroxide can cause erosive or degenerative changes to the surfaces of some common materials used in total hip replacement implants, Japanese researchers show.

Masamori Shigematsu, MD, and colleagues at Saga University’s department of orthopedic surgery in Saga City evaluated how a hydrogen peroxide (HO) solution affected three joint replacement materials; ultra high-molecular-weight polyethylene (UHMW-PE), a titanium alloy (Ti-6Al-4V) and thermal sprayed hydroxyapatite.

The researchers prepared eight samples each of 0.1 g of the polyethylene material (GUR1050, Ticona Co. Ltd.), 0.32 g of the titanium (Ti) alloy and 0.3 g of the hydroxyapatite material. Each sample measured 8×10×1 mm and was polished with a waterproof abrasive paper to create uniform surface conditions, according to the study.

Each sample was submerged in a Teflon container holding 20 ml of a 3% HO solution maintained at 37ºC. Two samples of each material were removed for evaluation after being submerged for one minute, 10 minutes and 180 minutes, according to the study.

The researchers found that none of the samples changed in weight after being submerged for any length of time. Scanning electron microscopy (SEM), Fourier transform infrared analysis and X-ray diffraction analysis also showed no marked changes. However, the HO solution did affect the titanium and hydroxyapatite samples.

After one minute, SEM showed black areas resembling cracks on the surfaces of Ti samples, which slightly increased in size as soaking continued.

“[Blackening] of the surface of [Ti] samples ... represented a degenerative process, which remained within a layer less than 1 µm in depth and did not invade deeper layers. Although they were only superficial, cracks did in fact occur on the Ti surface because of hydrogen peroxide, which is a fact that cannot be ignored,” the authors said in the study.

Hydroxyapatite samples also showed surface changes after one minute of HO exposure. These samples developed areas that the researchers considered to be grain boundaries, which also progressed as soaking continued. Samples soaked for 180 minutes also developed cracks in the vicinity of the grain boundaries, according to the study.

“[Etching] ... was found to proceed with increasing soaking time in areas that were thought to be grain boundaries,” the authors said.

“The formation of grain boundaries is a particularly serious problem, because grain boundaries weaken the fixation power of [hydroxyapatite] and may possibly influence the outcome of surgery,” they added.

The authors proposed several additional measures for the safe use of HO solutions, particularly during procedures involving titanium or hydroxyapatite-coated implants. These include the following:

use HO solutions before inserting an implant's socket and stem;
keep soaking periods under one minute; and
after using HO, sufficiently wash the site with a physiological saline solution and then sufficiently dry the site.

It is particularly important not to fill the articular cavity with HO solution after reduction, the authors noted.

For more information:
Shigematsu M, Kitajima M, Ogawa K, et al. Effects of hydrogen peroxide solutions on artificial hip joint implants. J Arthroplasty. 2005;20:639-646.