An event regarding wear involving an mrh bushing was reported.The event was not confirmed.Device evaluation and results: not performed as no product was returned for evaluation.Medical records received and evaluation: a review of the medical records by a clinician indicated that: i have seen the info for this patient with worn poly bushings in a gmrs device some 9-years post implantation.There is rather minimal information but it confirms the device was implanted after an extremely fragmented periprosthetic fracture around a previous ¿mega-prosthesis¿, type not specified in 2008.The old prosthesis was removed, the bone pieces collected and held together with a few cables with a new cemented ¿mega-prosthesis¿, the current gmrs.No other information is available, no x-rays or any other, so there is no info about conditions surrounding the current event.Given however the bad conditions surrounding the implantation we may suspect some procedure-related factors to be present increasing the poly wear rate.Anyway, the implantation in this very young patient (now 26-years) was probably for a malignant bone tumour at childhood age.We have to remind that a large segmental replacement has been performed.Such long segmental replacements cause huge stresses within the implant and especially its transition to the bone fixation area and the moving parts in the joint area as a consequence of the very long lever moment arm from mid femur to knee joint area.In addition, large soft tissue resections usually accompany the bone resection further weakening the musculature around the arthroplasty while reducing the muscular control of the patient over his/her arthroplasty and thereby further aggravating the relative overload condition on the implanted devices.A high poly wear rate can thus be expected given the size of the implanted bushings.Such problems are inherent to the much better survival of oncology patients in modern times.Clinical survival of patients after treatment for malignant bone tumours has much improved in the recent decades thanks to adjuvant therapy such as chemotherapy and radiotherapy.5-year survival of these patients has improved from a few percent to a large category of patients, real progress.The issue then has become that the service life of the implant is not anymore limited by the limited survival of the patient him/herself but by fatigue and wear phenomena in the devices.Such procedures thus should be regarded as temporary relief for patients with periodical renew surgery required after problems occur.The technical challenges for design of appropriate devices are however huge and cannot yet be completely solved with current technology.Prophylactic device exchange after growth is complete might theoretically be recommended for strength reasons but well ingrown device removal causes considerable surgical collateral damage and thus is rarely undertaken, only when problems arise such as in the current case.The problem of this device fracture should thus be considered an end of practical service life condition given the current state of device technology and the operating conditions in a childhood/young adult skeleton where activity level of patients is usually still relatively high.Principal failure mode thus represents quite likely an adverse mix of procedure-related factors regarding limits of current device technology and patient-related factors regarding implantation conditions for malignant bone tumour at young age.More clinical and especially radiological info might help solve further details of this case.-device history review: indicated all devices were manufactured and accepted into final stock with no reported discrepancies.Complaint history review: there have been no other similar events for the lot referenced.Conclusions: the medical review comment indicates that the problem of this device fracture should thus be considered an end of practical service life condition given the current state of device technology and the operating conditions in a childhood/young adult skeleton where activity level of patients is usually still relatively high.Principal failure mode thus represents quite likely an adverse mix of procedure-related factors regarding limits of current device technology and patient-related factors regarding implantation conditions for malignant bone tumour at young age.The exact cause of the event could not be determined because insufficient information was provided.Further information such as pre- and post-operative x-rays, operative reports as well as patient history and follow-up notes are required to complete the investigation for determining a root cause.No further investigation is required at this time.If additional information becomes available to indicate further evaluation is warranted, this record will be reopened.
|