Applid Anatomical Study Of The Surgical Safe Zone For The Anterior Double Plates And Screws To Treat The Sacroiliac Jiont Frcture And Dislocation

ObjectiveTo explore the surgical safe zone for the anterior double plates to fixthe sacroiliac joint and assess the anatomical security of the differentnumber of screws on the sacral sides by the sacroiliac joint appliedanatomical research and CT scan, then to treat posterior ring injuries in theTile type C pelvis fractures according to the results of anatomical study andCTThe study included three parts:1Applied anatomical study of the surgical safe zone of the sacroiliacjoint for the anterior double plates.2Anatomical security study of the different number of screws on thesacral sides3Clinical application of the anterior double plates to fix the sacroiliacjoint.Method: 1Applied anatomical study of the surgery safe zone for the anteriordouble plates.Applied anatomical study of the sacroiliac joint15normal cadavers pelvis were used in this study. The horizontaldistances from the L₄,L₅nerves anterior roots to the sacroiliac joint andthe vertical distance from L₄,L₅nerve root to anterior surface of sacral wingwere measured respectively, then the distances from the intervertebralforeman of L₄,L₅nerve roots to rim of real pelvis and the diameter of theL₄,L₅nerve root in their midpoint were measured respectively.CT study of the sacroiliac jointIn two dimensional coronal reconstruction of the pelvis specimen, theangles between the sacroiliac joints and sagittal planes, the angles betweenthe upper border and lower border of sacral rings,the length of thesacroiliac joint and the distance from the sacroiliac joint to the lateralaspect of sacral canal were tested.2Anatomic security study of the different number of screws on thesacrum（1） The virtual operations in the MIMICS soft15normal cadavers pelvis were scanned in CT. Thin-section CT scandata were saved, and analyzed by the software10.0.The virtual operationsof the anterior double plates to fix the sacroiliac joint were performed in thesame software. Mimic operations on the pelvis specimensThe left sides of the sacroiliac joint were divided into group A, inwhich two screws were placed into the sacral sides. The right sides of thesacroiliac joint were divided into group B, one screw was placed into thesacral sides. The distances from the medial edge of the plates to the lateralsides of the L₄,L₅nerves roots were measured. The relationship of thescrews and the sacroiliac joint was checked by radiograph.3Clinical application of the anterior double plates to fix the sacroiliacjoint.From March2011to January2012，we used the anterior double platestechniques to treat posterior injuries of Tile type C pelvic fractures in5cases who have no symptom of the L₄,L₅nerves roots injuries. Afterfollowing-up from4months to12months, the pain of sacroiliac joint, thegaits, the power of knee extension and dorsal extension of big toe and thesense of pain and touch in the legs were examined. The X-ray of pelviswere took every two to three months.Results:1Applied anatomic study of surgical safe zone of the double anteriorplates to fix the sacroiliac joint（1） Applied anatomical study of the sacroiliac jointThe horizontal distance from the lateral side of the L₄、L₅nerves rootto the sacroiliac joint gets gradually shorter from the top to the bottom, the widest distances are（2.1±0.2）and（2.7±0.2）cm respectively, the mostnarrow were（1.2±0.2）and（1.5±0.2）cm respectively. The vertical distancefrom the L₄nerves roots to the front surface of the sacrum becomes bit bybit shorter from the intervertebral foramen to the rim of the pelvis. Thelength of the L₄nerves root is（7.4±0.8）cm, its average diameter at themidpoint is（2.7±0.8）mm; the length of the L₅nerves root is（3.9±0.5）cm, and its average diameter at the midpoint is（7.3±1.4）mm.（2） CT study of the sacroiliac jointBy CT reconstructation measure, the angle between the sacroiliac jointand sagittal plane varies indistinctively, about30°, the distance from thesacroiliac joint to the spinal canal changes from3.3cm to2.3cm, thehorizontal distance from the sacroiliac joint to the intervertebral foramen is2cm. The angle between the upper border and lower border of the Sacralwing is （78±3） degrees. The length of the sacroiliac joint line is（4.6±0.3）cm2Anatomical security study of the different number of screws on thesacrum.（1） The virtual operations in the MIMICS softIn the virtual operations, the sacrum sides can accommodate twoscrews safely. However, the angels of screws in the sacrum vary from29°to52°,mean（35±6）degrees.（2）Mimic operations on the pelvis specimens In group A, The distances from the medial edge of the upper and lowerplates to the lateral sides of the L₅nerves roots are（3.0±1.4）mm and（1.5±1.0）mm respectively. The upper and lower plates can be placedbelow the L₄nerves roots safely. In group B, the distances from the medialedge of the upper plates to the lateral sides of the L₄,L₅nerves roots are（5.0±1.1）mm and（10.3±1.3）mm respectively. The lower plates were（2.7±0.5） mm and（5.1±0.9）mm respectively. In X-ray examination,no screw of the sacrum of the upper plates was found in the sacroiliac jointin group A, and4screws in lower plates. On the other hand, no screw in thesacrum in the group B was in the sacroiliac joint.3Clinical application of the anterior double plates to fix the sacroiliacjoint.All incisions healed without infection. The duration of following-upvary from3months to12months. No pain is found in the sacroiliac joints,The length of two lower limbs in the all patients is almost same. The powerof injured limbs in the knee extension and dorsal extension of big toe issame to the normal sides. The sense of touch and pain is equal in the twolegs. The patients can walk normally without limp and sacroiliac joint painafter6months of post-operation. The X-ray film showed that the sites ofplates and screws were right without mental works breakagepost-operatively.Conclusion: 1The surgical safe zone for the anterior double plate and screws to fixthe sacroiliac joint fracture and/or dislocation is described as following:The upper plates should be placed on the upper third of the sacroiliac joint,and the exposed width should not be more than2.5cm to medial side ofsacroiliac joint. The lower plates should be placed on the middle third ofthe sacroiliac joint, and the exposed maximal width is1.5cm to the medialside of sacroiliac joint. The screws should be inclined medially a bit morethan30degrees and toward rim of real pelvis. The angle of two plateswhich are toward the medial aspect of sacrum varies from50to60degrees.2When the anterior double plates are applied to fix the sacroiliac joint,that two screws are implanted into the sacrum in the upper plate and onescrew in the lower plate is safe, and can increase the stability in theory.3The anterior double plates techniques to treat posterior ring injuriesof type C pelvic fracture are safe and effective in clinic when they areplaced with right techniques and at the surgical safe zone.