|
It was reported that after a right thr surgery, the patient experienced pain caused by symptomatic osteolysis of the acetabulum and proximal femur on the right by abrasion from polyethylene.Revision surgery was performed in order to remove the shell, insert and the head.The patient outcome is unknown.
|
|
Results of investigation: a revision surgery was reported with an ep-fit shell (b)(6), an ep-fit pe insert (b)(6) and an unknown ceramic ball head forte.It was reported that the patient experienced pain which was caused by osteolysis in the acetabulum ultimately due to abrasion of the ep-fit pe insert and it was assumed in the operative report that the cup inclination may have contributed to the relatively early failure of the insert.The complaint devices, used in treatment, were returned for investigation.A material inspection of the complaint parts was performed.The cup surface showed signs of bone ongrowth distributed over the whole cup surface.The surface of the polyethylene (pe) insert showed signs of wear and scratches, it is unclear if the scratches were caused during implantation or the explantation procedure.The maximum linear wear of the ep-fit pe insert was determined as 1.076 mm using a taylor hobson tr290 roundness machine.The profile of the pe insert was taken at approximately 4mm below the rim and can be seen in the attached report indicating the region of maximum wear where the chamfer of the liner was partially worn away (see attachment, figure 2).Based on an in vivo time of 13 years, a linear wear of 1.076 mm corresponds to a wear rate of 0.083 mm/y.This is in line with wear rates of uhmwpe hip cup inserts reported in literature.According to different sources, osteolysis is rarely observed at wear rates below 0.1 mm/y.As alternative product, a highly crosslinked polyethylene insert could have been used in this case.Based on the available information it is not possible to assess whether the use of a highly crosslinked polyethylene insert would have prevented the development of osteolysis in the observed time frame.Additionally, discoloration of the bearing regions was observed for the pe insert.A slight uniformly distributed discoloration was observed on the pe insert.No association could be found between the location of discoloration of the pe insert and the region of wear of the product.For most cases, the root cause for yellowing in the bearing regions is lipid absorption.The determination of the cause for the discoloration would require destructive methods such as extraction of the lipids in a solvent or infra-red spectroscopy to measure oxidation.In order to perform a destructive analysis, an authorization of the patient and of the national competent authorities is required.These analyses were therefore not performed.The production documentation for the ep-fit shell (art.No.75003902, lot no.0511.13.6375) and pe insert (art.No.75003961, lot no.0508.02.4155) were reviewed.The raw material certificate for the pe insert were checked, no non-conformity was found.No deviations from the standard manufacturing process were found which could have contributed to the reported issue.No further complaints were found in the complaint history reviews for either products.In the current ifu lit.No.12.23 ed.05/16, wear and loosening of the implant are listed as possible side effect.The severity and the failure mode are covered through our risk management.On the basis of the provided medical documents, it is unknown whether there was any traumatic injury or if the patient had any underlying comorbidities which may have contributed to the revision.Based on the conducted investigation, it is seen that this issue is a known inherent risk of the device which is listed as possible adverse effects in the ifu of the product.Smith+nephew will continue to monitor for similar issues.No further actions are deemed necessary at this time.The complaint parts will be retained.
|
