Minimally invasive removal of a deep-positioned cannulated screw from the femoral neck:A case report

BACKGROUND Clinical femoral neck fracture is common.Based on patient age and fracture type,different surgical methods can be selected,including cannulated screw fixation of the femoral neck and artificial total hip joint or semi-hip joint replacement.When patients with femoral neck fracture are treated with cannulated screw fixation,a cannulated screw may be positioned too deep.The excessively deep-placed screw is difficult to remove and causes major trauma to the patient.CASE SUMMARY A patient with poliomyelitis and femoral neck fracture was treated with a cannulated screw that was placed too deep.A self-made auxiliary tool(made of a steel sternal wire)was used to remove the cannulated screw near the pelvic cavity.CONCLUSION The depth of the cannulated screw can be estimated before screw placement using an improved hollow screwdriver with a scale mark,thus improving the safety of screw placement and facilitating clinical use.

Study on clinical effects of pedicle screw combined with immobilized implantation bone by wirerope and hallow compression screw immobilization in treating spondylolysis of lumbar vertebra of multiple segments of adults

Objective:To observe clinical effects of pedicle screw fixation combined with cable wires and bone graft and cannulated compression screws on adult multi-segment lumbar spondylolysis.Methods:70 cases of patients with multi-segment lumbar spondylolysis were selected in our hospital.According to different surgical schemes,these patients were divided into the observation group(35 cases)and the control group(35 cases).The observation group received pedicle screw fixation combined with cable wires and bone graft and the control group received cannulated compression screw fixation.Macnab criteria were adopted to implement a therapeutic evaluation of two groups of patients to make an observation and comparison of the excellent and good rate of surgery and a series of indicators including perioperative clinical effects,intraoperative blood loss,duration of surgery,hospital length of stay(HLOS),visual analogue scale(VAS),Oswestry disability index and Japanese Orthopaedic Association(JOA)score.Results:The excellent and good rate of the observation group was 97.14%,and that of the control group was 82.86%,the difference between two groups was statistically significant(χ^(2)=6.248,p=0.012).The differences in intraoperative blood loss,duration of surgery and HLOS between two groups were statistically significant(t=-4.55,t=-4.55,t=-4.55;p<0.05).Oswestry index,VAS score and JOA score of the observation group were(2.4±0.9),(28.5±6.4)and(27.1±3.1)respectively,and these of the control group were(3.5±1.2),(37.1±7.8)and(21.3±2.7)respectively,the differences between two groups were statistically significant(t=4.338,t=5.043,t=8.347,p<0.05).Conclusions:Pedicle screw combined with immobilized implantation bone by wirerope has an excellent clinical effect on the treatment of adult multi-segment lumbar spondylolysis,and it has a series of advantages such as fast postoperative recovery,small surgical trauma and so on.In addition,this technique can also restore the stability of spinal segments and relieve pains to a greater degree.

In vitro crevice corrosion of biodegradable magnesium in different solutions

Magnesium(Mg)is a promising biomedical metal because of its biodegradability.The crevice between tissue and Mg implant can not be neglected in some implantation sites due to inducing crevice corrosion of Mg.In this paper,a new single mold was designed to build the in vitro experimental setup and four kinds of solutions,i.e.the deionized water(DW),the 0.9 wt.%sodium chloride solution(NaCl),the phosphate buffer saline(PBS)and the modified simulated body fluid(m-SBF)were used to explore necessary factors of crevice corrosion in Mg.It was observed that crevice corrosion in Mg sheets would occur in NaCl and PBS solution under 0.2,0.5 and 0.8 mm crevice thickness.And it was found that there were two necessary factors,i.e.chloride ion and crevice dimension,in crevice corrosion.For the high-purity Mg cannulated screws,crevice corrosion could occur inside tunnel when immersed in PBS.

Comparison of the clinical efficacy of different fixation systems for the treatment of transverse patellar fractures

Purpose:This study was designed to compare the clinical efficacy of"8"and"0"wire fixation systems combined with double-head cannulated compression screws or Kirschner wires for the treatment of transverse patellar fractures.Methods:From September 2011 to September 2018,patients with closed transverse patellar fractures treated with a double-head compression screw or Kirschner wire were included and analyzed retrospectively.Patients with patellar fractures combined with distal femoral fractures,tibial plateau fracture or preoperative lower limb dysfunction were excluded.The patients treated with the"8"tension band wire fixation system and Kirschner wire were taken as Group A;those treated with the"0"fixation system and Kirschner wire were taken as Group B;those treated with the"8"fixation system and double-head cannulated compression screw were taken as group C;and those treated with the"0"fixation system and double-head cannulated compression screw were taken as group D.Six weeks and one year after the operation and every month from the third month after the operation until the fractures healed,an X-ray examination was performed to identify fracture healing.The time of fracture healing and postoperative complications of the four groups were compared.One year after the operation,knee function was evaluated by Bostman’s score.Results:During the study period,168 patients with patellar fractures were treated by operations,and 88 patients were excluded because the fracture type did not meet the requirements or because there were combined fractures of the distal femur or tibial plateau.As a result,80 patients were included in this study,20 in each group.All the patients were followed up for an average period of 12.2 months.Compared with Group A,patients in Group D presented less postoperative discomfort in the prepatellar region,quicker fracture healing,less fixation failure and better postoperative knee function scores(all p<0.05).The incidence of internal fixation failure in Group(B+D)was lower than that in Group(A+C)(p>0.05).Conclusion:The"0"wire fixation system combined with a double-head cannulated compression screw seems to be more beneficial than the other three fixation systems for the treatment of transverse patellar fractures.

Biomechanical analysis of the computer-assisted internal fixation of a femoral neck fracture

The number and spatial configuration of the screws will affect the stability and prognosis of the fractures.In our study,we assessed the biomechanical effects of the double-head cannulated compression screw(DhCCS)and ordinary cannulated compression screw(OCCS)for the treatment of femoral neck fractures by using computer finite element analysis.The original digital imaging and communications in medicine(DICOM)data of a proximal femur were imported into Materialise’s interactive medical image control system(MIMICS)software for modeling.Both DhCCS and OCCS 3D-models were obtained by using the 3D scan technique.Using the fracture model and internal fixation assembly model with an inverted triangle,two horizontal and vertical distribution were established in UG software.Next,the displacement and stress distribution were calculated in ANSYS software.The displacement value of the femoral head in the DhCCS group was smaller than that in the OCCS group,and the displacement value in the two horizontal groups was smaller than that in the vertical group.The stress distribution in the DhCCS group was concentrated on the screw rod at the fracture block and thread end,while only at the fracture block in the OCCS group.The stress in the horizontal group was more dispersed on the screws than that in the vertical group.DhCCS has reliable stability for the fixation of femoral neck fractures and applied in the clinical work and 2 horizontal fixation can be used when two screws are selected.