Evaluation of diamond-like carbon-coated orthopaedic implants

Diamond like carbon coatings for potential application in biological implants—a review

“…Previous research has suggested early delamination based failures, and this indeed occurred in large numbers of implanted DLC coated hip joints in the past [7]. Testing by Lappalainen et al [39], and to a lesser extent Dowling et al [40] and Oñ ate et al [50] tested over 15 million, 6 million and 5 million cycles on joint simulators respectively(Lappalainen estimated 1 million cycles to be equivalent to 1 year in use). These long term tests showed good results in wear reduction and life of the coating.…”

“…A number of papers do not state the type of DLC used [4,[40][41][42][43][46][47][48], while those that do state they are using ta-C or a-C:H, they fail to mention the composition ratio. While the manufacturing method and the source material enable an estimation of the composition, without knowing the exact conditions during the deposition, it remains little more than a guess.…”

“…Out of 14 reports [4,27,[39][40][41][42][43][44][45][46][47][48][49][50] there appeared to be no standardisation between choice of testing conditions and counter surface.…”

“…The results showed similarities, with all 3 tests showing a reduction in wear compared to uncoated tests, however to different levels. Tiainen [27] showed a reduction in wear by a factor of 10 5 -10 6 , Lappalainen et al [39] only showing a reduction of 10 2 -10 4 and Fisher et al [42] only showing a wear rate reduction of 26.The only notable differences between these tests is that Fisher et al tested the DLC coating against a different hard coating (CrN) not a 2nd DLC surface and a slightly different testing rig Papers that use DLC on UHMWPE(Saikko et al [43], Affatato et al [41] and Dowling et al [40]) use similar testing periods and testing solutions. However, Affatato et al [41] used double the test load that Saikko et al [43] employed.…”

“…So although the results are similar (Affatato et al showing DLC to offer a very slight improvement, Saikko et al showing it is virtually the same, if a little worse than using an uncoated sample) they are difficult to compare due to such a simple difference in test conditions. The other testing using UHMWPE were performed by Dowling et al [40].The study used a similar testing period, but a different testing solution (distilled water) with no information on the loading provided, making its' findings of a wear volume reduction by a factor of 18 very difficult to compare to that of the other two tests. Overall hip simulator testing seems to be positive with DLC showing an improvement compared to uncoated samples in all tests.…”