Trackwise #(b)(6).Event description: the hospital reported that during a coronary artery bypass procedure using acrobat-i stabilizer.The knob cannot fix the flexible arm.This complaint belongs to c-om-10000.The problem was discovered during use and did not affect the patient, and the operation was completed after replacing the same product.The product is from lot 3000189482.This issue occurred in china, and it is determined to file a medical device reporting since the similar products are sold in us.The investigation has been started since the complaint was received, and the following contents has been conducted: 1.Dhr review: the dhr of the reported lot 3000189482 has been reviewed.No non-conformity indicating the reported failure was observed.All the products had been performed 100% mechanical functional test during production.They all passed the function test which demonstrate the knob can be tightened and also can tighten the link arm.2.Trend review: in the last 12 months, 1st mar 2021 to (b)(6) 2022, the occurrence rate is approx.0.051% for suzhou manufactured om-10000/om-10000z.3.Returned device evaluation: the device was received on (b)(6) 2021, the following contents have been done: 1) visual inspection: no visual defects were observed on the product; 2) functional test: rotating the knob, idling rotating was found, the knob cannot be tightened and link arm cannot be tightened.To check this knob idle rotating during tightening, the stabilizer was disassembled for checking the relevant assembly and components status.3) disassemble and examine the assembly according to the applicable instructions found in the manufacturing process instructions knob assembly mp-bh-0005.It is found that the lead-in thread on acme nut was broken.4) verify 2 to 4 threads of the acme screw are exposed past the housing mount.It shows about 3 threads out of the housing mount, the returned product is conforming to this requirement.5) check the pilot crimping and its position, the pilot crimping is conforming to process instruction requests.6) replace the abnormal acme nut with a new one taken from another raw material lot to check the function of the returned product.It was tested 30 times according to ifu, and found that no knob tighten issue happened, the knob rotating smoothly without idle rotating, and the link arm can be tightened.7) the stabilizer was furtherly disassembled to check the relevant components' dimensions, the dimensions are conforming to the drawing requirements, no deficiency was observed.It¿s indicated based on the above evaluation that, the knob idling rotation during tightening would be caused by the acme nut lead-in thread broken, since the broken thread would be potentially not smoothly engaged or even not engaged with the acme screw lead- in thread during tightening.However, no non-conformities indicating the acme nut thread broken or defect from raw material were observed.All the products have passed 100% mechanical functional test in process, which demonstrated the knob can be tightened and link arm can be tightened.Complaint historical data has also been reviewed, the failure knob difficult/ unable to tighten-arm does not lock happened before and has been investigated.The most probable root cause for the acme nut lead in thread broken would be rotating to loosen the knob anti-clockwise rapidly for several circles and then rotating to tighten the knob clockwise rapidly, or rotating the knob leaner or too much strength used, which caused acme screw misaligned with the acme nut lead-in thread, acme nut lead-in thread broken, then the knob could not be tightened and link arm could not be tightened.
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