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Description of mdr reportable event received by implantcast implantcast received the following report from a license partner on (b)(6) 2020: patient was originally treated in (b)(6) 2009 with a cemented distal femur reconstruction.After 10 years without any complications, whilst getting out of her car, she heard a loud sound from the affected limb and couldn't walk on it anymore.Subsequent imaging showed that the femoral stem has been completely dislodged from the assembly.A revision operation was scheduled and following observations were made: the bar screw was broken in two pieces with the shorter segment stuck in the femoral stem.Teeth locking mechanism on top of the extension piece was completely gone as if it was worn down over time.Damage analysis.Optical inspection: an optical inspection of the affected medical device could not be performed.So far, the device is not available for inspection.Photographs were available.These show the stem, the mutars screw and the extension piece.It can be seen that a broken piece of the mutars screw is in the thread of the stem.A further picture of the screw shows the opposite fracture surface.At first, there are no visible abnormalities on the extension piece.Assessment of the manufacturing protocols: the manufacturing protocol of the medical devices known were checked.These show no deviations.Assessment of the dimensional accuracy of the construction: as no product is available for inspection, an assessment of the dimensional accuracy could not be performed, yet.Functional testing as no product is available for inspection, a functional testing could not be performed, yet.Assessment of the mechanical properties: the approval of the basic materials was performed.External evaluation: as no explant is available for inspection, an external evaluation was not commissioned.Assessment of the medical records: patient gender: female.Age at time of event: (b)(6).Weight: (b)(6).Height: 165.Degree of activity: normal.Past medical history: implantation date: (b)(6) 2009 (diagnosis: osteosarcoma of distal of right femur).Explantation date: (b)(6) 2020 (diagnosis: disassembled reconstruction system (broken screw); replacement of stem of the prosthesis).An x-ray is available for inspection.The x-ray shows the femoral stem, which is disconnected from the extension piece.Surgical technique and instructions for use: the surgical technique 'mutars distal femur st' describes the complete implantation process in detail.There are no indications of an incorrect or incomplete surgical technique.The instruction for use (ifu) 'mutars® tumor- and revision system' was checked.There is no indication of incorrect instructions for use.Summary: the medical device is not available for inspection at the moment.Photographs were available.These show the stem, the mutars screw and the extension piece.It can be seen that a broken piece of the mutars screw is in the thread of the stem.A further picture of the screw shows the opposite fracture surface.At first, there are no visible abnormalities on the extension piece.The manufacturing protocols of the affected products were checked.These show no deviations.An x-ray is available for inspection.The x-ray shows the femoral stem broken, which is disconnected from the extension piece.Further information and the affected products have been requested from the reporter.
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Damage analysis: 1.Visual inspection (condition of the product).Implant cast received the following explants from our license partner - see pic.1 pic.1 shows the mutars® femoral stem (1); the broken mutars® screw m10x65mm (2), mutars® extension piece 40mm (3).The femoral stem in picture 2 shows no abnormalities.There were no remains of bone cement on the stem.But in the inner thread at the end of the stem is the broken part of the thread of the mutars® screw, which cannot be released without damaging the explant.The tooth locking on the stem is ok (see pic.3).The fracture surface of the broken screw inside the stem is completely abraded and has mechanical damages.That's why an analysis of the cause of the break is no longer possible.Figure 5 shows the opposite side to the fracture surface of the broken screw.There is an approx.2mm wide circumferential, shiny abraded edge on the fracture surface and in the middle an approx.2mm high raise with a 6mm diameter on which there is abraded metallic material.Here, too, the cause of the break can no longer be analyzed.But it can be said that the bare, abraded area was caused by permanently tough touching and grinding on the edge of the stem opening.The raised 6 mm wide area in the middle of the fracture surface abraded the thread piece which sticks in the end of the stem.There are metal particles in the thread.On the male side of the extension piece in picture 6 & 7 the teeth are strongly rounded (orange arrows).The tooth interlock is completely abraded at the opening of the extension sleeve with the larger diameter (pic.8).A deconcentric friction surface has formed there (red line in pic.8), which was created by the friction of the extension sleeve on the tooth interlock of the stem.In figure 9 you can see that an edge has formed inside the extension piece.The inner diameter is severely widened by abrasion.It tapers along its length and widens again behind it (like a double cone).2.Assessment of the manufacturing protocols.The manufacturing documents and the test records were checked.There were no deviations during the production process, the product has been released with the final inspection.3.Assessment of the dimensional accuracy of the construction.Mechanical damages and abrasion are clearly visible on the components.Therefore, it is obvious that the dimensional accuracy is no longer given.For this reason, the components were not measured.4.Functional testing.The following photos show a reconstruction of the failure situation inside the patient.It is shown in which position the parts must have stood together for the damage described to occur (see section 5.1 visual inspection in figs.4 & 5 or in figs.8 & 9).5.Assessment of the mechanical properties.For the raw material used, materials were released in accordance with the procedure instruction "va_743-mat_freigabe von werkstoffe".According to the documents available, the materials used corresponded to the specification.Testing the mechanical properties of the product would require destructive testing, which requires explicit patient permission.At the present time of the investigation, there is enough data that clearly shows that the damage event cannot be attributed to a possible deviation from specified material properties.Therefore, no mechanical tests are carried out on the product.6.External evaluation.The available data provide sufficient information on the damages, so no external assessment of the damaged parts is commissioned.7.Assessment of the medical records.The investigation included the analysis of surgical reports from (b)(6) 2009 and (b)(6) 2020.X-rays of the time of implantation and the current incident were also available.General information about the affected patient patient gender: female.Age at time of event: 30.Weight: 65.Height: 165.Bmi: 23,9 (normal weight).Degree of activity: normal (working in a seated position, regular walking on a treadmill inside a gym).No accident.Information on the past medical history of the affected implant and the current incident.Affected side: right.Implantation date: 12/23/2009 (diagnosis: osteosarcoma of distal of right femur).Explantation date: 05/05/2020 (diagnosis: disassembled reconstruction system(broken screw); replacement of stem of the prosthesis).Lying time of the implant: 10 years, 4months.The x-ray shows the femoral stem, which is disconnected from the extension piece.8.Surgical technique and instructions for use.The surgical technique "mutars® distal femur st" describes the complete implantation process in detail.There are no indications of an incorrect or incomplete surgical technique.The instruction for use (ifu) "mutars® tumor- and revision system" was checked.There is no indication of incorrect instructions for use.The compatibility of the 3 products mutars® screw m10x65mm, mutars® femoral stem cemented 13/120mm and mutars® extension piece 40mm with each other was checked.The combination variants are approved.Summary - categorization and interpretation of the results.Due to the low information content of the op reports and the severely damaged explants, only a presumption can be made about the possible cause of the damage.The cause of the damage can be described in such a way that initially there was no complete frictional connection at the tooth interlock between stem and extension piece.There could be several reasons for this.For example, the tooth interlock could have been contaminated with foreign body.It is also possible that the threads were damaged during implantation.It is also possible that the screw jammed in the internal thread of the stem and thus could not be fully tighten or the screw had been tightened too little.On the other hand, there may have been increasing loosening of the femoral stem over the 11 years that the implant has been in place.Increased play can presumably have loosened the components below the stem.Due to the lack of frictional connection in the tooth interlock, there were initially minimal rotary movements, which led to increasing wear on the toothing.When the teeth were increasingly worn off, a small gap formed between the extension piece and the stem.On the mutars® screw, the patient's activity resulted in intense micro-movements at the later break point, which could be due to torsional and bending moments.This application of force resulted in material fatigue on the thread of the mutars® screw in the form of a progressively developing fatigue fracture, which reduced the load-bearing capacity of the component.The sudden shearing off caused by a violent fracture could have triggered everyday movements of the patient.It can be assumed that the patient was still active with the broken implant for a very long time, as the fracture surfaces and the inner cone of the extension piece show very strong abrasion.The patient could still be active because the end of the stem stuck quite deeply into the extension sleeve.Due to a random movement, such as getting out of the car as described, the stem suddenly seemed to have lifted itself out of the extension piece and slipped next beside the opening of the extension sleeve.After reviewing the product and manufacturing documentation, a technical cause that could be due to design or manufacturing problems can be ruled out.The basic cause of the material fatigue on the screw cannot be clarified.
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Implantcast received the following report from a license partner on 05/06/2020: "patient was originally treated in (b)(6) 2009 with a cemented distal femur reconstruction.After 10 years without any complications, whilst getting out of her car, she heard a loud sound from the affected limb and couldn't walk on it anymore.Subsequent imaging showed that the femoral stem has been completely dislodged from the assembly.A revision operation was scheduled and following observations were made: the bar screw was broken in two pieces with the shorter segment stuck in the femoral stem.Teeth locking mechanism on top of the extension piece was completely gone as if it was worn down over time.Since explantation of the bar screw (broken piece) from femoral stem was not possible, the old stem was explanted and replaced with a brand new cementless femoral stem.Additionally a new extension piece and bar screw (both of the same size) were used.".
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