Feasibility analysis and nail planning ofS2 iliac crest screw placement in children / 中国骨伤

OBJECTIVE@#To evaluate the feasibility of S2 alar iliac screw insertion in Chinese children using computerized three-dimension reconstruction and simulated screw placement technique, and to optimize the measurement of screw parameters.@*METHODS@#A total of 83 pelvic CT data of children who underwent pelvic CT scan December 2018 to December 2020 were retrospectively analyzed, excluding fractures, deformities, and tumors. There were 44 boys and 39 girls, with an average age of (10.66±3.52) years, and were divided into 4 groups based on age (group A:5 to 7 years old;group B:8 to 10 years old;group C:11-13 years old;group D:14 to 16 years old). The original CT data obtained were imported into Mimics software, and the bony structure of the pelvis was reconstructed, and the maximum and minimum cranial angles of the screws were simulated in the three-dimensional view with the placement of 6.5 mm diameter S2 alar iliac screws. Subsequently, the coronal angle, sagittal angle, transverse angle, total length of the screw, length of the screw in the sacrum, width of the iliac, and distance of the entry point from the skin were measured in 3-Matic software at the maximum and minimum head tilt angles, respectively. The differences among the screw parameters of S2 alar iliac screws in children of different ages and the differences between gender and side were compared and analyzed.@*RESULTS@#In all 83 children, 6.5 mm diameter S2 iliac screws could be placed. There was no significant difference between the side of each screw placement parameter. The 5 to 7 years old children had a significantly smaller screw coronal angle than other age groups, but in the screw sagittal angle, the difference was more mixed. The 5 to 7 years old children could obtain a larger angle at the maximum head tilt angle of the screw, but at the minimum cranial angle, the larger angle was obtained in the age group of 11 to 13 years old. There were no significant differences among the age groups. The coronal angle and sagittal angle under maximum cephalic angle and minimum cranial angle of 5 to 7 years old male were (40.91±2.91)° and (51.85±3.75)° respectively, which were significantly greater than in female. The coronal angle under minimum cranial angle was significantly greater in girls aged 8-10 years old than in boys. For the remaining screw placement angle parameters, there were no significant differences between gender. The differences in the minimum iliac width, the screw length, and the length of the sacral screws showed an increasing trend with age in all age groups. The distance from the screw entry point to the skin in boys were significantly smaller than that of girls. The minimum width of the iliac in boys at 14 to 16 years of age were significantly wider than that in girls at the same stage. In contrast, in girls aged 5 to 7 years and 11 to 13 years, the screw length was significantly longer than that of boys at the same stage.@*CONCLUSION@#The pelvis of children aged 5 to 16 years can safely accommodate the placement of 6.5 mm diameter S2 alar iliac screws, but the bony structures of the pelvis are developing and growing in children, precise assessment is needed to plan a reasonable screw trajectory and select the appropriate screw length.

Freehand S2 Alar-Iliac Screw Placement Using K-Wire and Cannulated Screw: Technical Case Series

OBJECTIVE: Among the various sacropelvic fixation methods, S2 alar-iliac (S2AI) screw fixation has several advantages compared to conventional iliac wing screw. However, the placement of S2AI screw still remains a challenge. The purpose of this study was to describe a novel technique of free hand S2AI screw insertion using a K-wire and cannulated screw, and to evaluate the accuracy of the technique. METHODS: S2AI screw was inserted by free hand technique in sixteen consecutive patients without any fluoroscopic guidance. The gearshift was advanced to make a pilot hole passing through the sacroiliac joint and directing the anterior inferior iliac spine. A K-wire was placed through the pilot hole. After introducing a cannulated tapper along with the K-wire, a cannulated S2AI screw was installed over the K-wire. RESULTS: Thirty-three S2AI screws were placed in sixteen consecutive patients. Thirty-two screws were cannulated screws, and one screw was a conventional non-cannulated screw. Thirty out of 32 (93.8%) cannulated screws were accurately positioned, whereas two cannulated screws and one non-cannulated screw violated lateral cortex of the ilium. CONCLUSION: The technique using K-wire and cannulated screw can provide accurate placement of free hand S2AI screw.

Freehand S2 Alar-Iliac Screw Placement Using K-Wire and Cannulated Screw: Technical Case Series

OBJECTIVE: Among the various sacropelvic fixation methods, S2 alar-iliac (S2AI) screw fixation has several advantages compared to conventional iliac wing screw. However, the placement of S2AI screw still remains a challenge. The purpose of this study was to describe a novel technique of free hand S2AI screw insertion using a K-wire and cannulated screw, and to evaluate the accuracy of the technique.METHODS: S2AI screw was inserted by free hand technique in sixteen consecutive patients without any fluoroscopic guidance. The gearshift was advanced to make a pilot hole passing through the sacroiliac joint and directing the anterior inferior iliac spine. A K-wire was placed through the pilot hole. After introducing a cannulated tapper along with the K-wire, a cannulated S2AI screw was installed over the K-wire.RESULTS: Thirty-three S2AI screws were placed in sixteen consecutive patients. Thirty-two screws were cannulated screws, and one screw was a conventional non-cannulated screw. Thirty out of 32 (93.8%) cannulated screws were accurately positioned, whereas two cannulated screws and one non-cannulated screw violated lateral cortex of the ilium.CONCLUSION: The technique using K-wire and cannulated screw can provide accurate placement of free hand S2AI screw.

Percutaneous S2-alar-iliac screw fixation for lower lumbar spondylodiscitis with no neurological symptoms in elderly patients: analysis of short-term curative effect / 介入放射学杂志

Objective To evaluate the short-term efficacy of percutaneous S2-alar-iliac screw (S2AIS) fixation for the treatment of lower lumbar spondylodiscitis with no neurological symptoms in elderly patients.Methods The clinical data of 28 patients of lower lumbar spondylodiscitis with no neurological symptoms,who were admitted to the Ward of Spine,Department of Orthopaedics,General Hospital of Shenyang Military Region,China,to receive percutaneous S2AIS fixation,were retrospectively analyzed.The operation was performed by the same surgeon for all patients.A total of 56 S2AIS fixation procedures were accomplished.The patients' age varied from 71 to 79 years old.The spondylodiscitis was located at IAL5 or L5-S1.After the treatment,the patients were followed up for a mean of 6.67 months.The mean operative time,the amount of intraoperative blood loss,the postoperative bed time,the average hospitalization days and the postoperative wound healing were documented and analyzed.The Oswestry score,visual analogue score,erythrocyte sedimentation rate,C reactive protein level were determined before operation as well as at one week and 6 months after operation,and postoperative CT was performed to check the loosening of internal screw fixation.The results were compared and analyzed.Results The mean operative time was (158.12±4.32) min,the average amount of intraoperative blood loss was (25.34±3.23) ml,the average postoperative bed time was (1.34±0.35) d,and the average hospitalization time was (7.29±1.34) d.Poor surgical incision healing was seen in only one patient,and the postoperative wound healing rate was up to 96.42％.Loosening of right S2AIS was detected in one patient,with the screw loosening rate being 1.79％.The Oswestry scores determined at one week and 6 months after treatment were 32.21 and 23.20 respectively,which were significantly different from the preoperative score (P＜0.05).The visual analogue scores determined at one week and 6 months after treatment were 2.17 and 1.25 respectively,which were significantly different from the preoperative score (P＜0.05).At one week and 6 months after treatment,the erythrocyte sedimentation rates were 15.32 mm/h and 14.56 mm/h respectively,and the C reactive protein levels were 7.89 mg/L and 8.90 mg/L respectively,both of which were significantly different from the preoperative ones (both P＜0.05).Conclusion For the treatment of lower lumbar spondylodiscitis with no neurological symptoms in elderly patients,percutaneous S2AIS fixation has certain advantages,such as less trauma,less blood loss,early postoperative ambulation,remarkable improvement of clinical symptoms,etc.with satisfactory short-term clinical efficacy.

Finite element comparative study of S2 alar-iliac screw and sacroiliac joint screw in treatment of type C sacroiliac joint dislocation / 中华创伤杂志

Objective To compare the biomechanical characteristics between S2 alar-iliac (S2AI) screw and sacroiliac joint screw in treating unilateral type C sacroiliac joint dislocation. Methods A 25 year-old healthy male adult agreed to take computed tomography scan of the pelvis. The pelvic floor thickness was 1 mm and the image data were saved in DCOM format. A three dimensional finite element model of intact pelvis was reconstructed by Mimics, Geomagic, SolidWorks, and Abaqus softwares. A finite element model of type C unilateral sacroiliac dislocation was established. One S1 vertebral sacroiliac screw of 6.5 mm in diameter (S1 group), one S2AI screw (S2AI group) and one Si vertebra sacroiliac screw + one S2 vertebra sacroiliac screw (S1+S2 group) were placed in the model, respectively. The500 N vertical load on the upper surface of the sacrum was simulated. The displacement value of sacroiliac joint, the displacement of sacrum, the stress value of the internal fixation and surrounding bone, and the stress distribution cloud map were recorded and analyzed. Results The displacement data showed that displacement distribution in the three groups had a consistent trend. In terms of the absolute value of displacement the result was S, group＞S 2AI group＞S1+ S2 group, of which the maximum displacement of sacroiliac joint in S1 groups was 0.87 mm and that of sacrum was 1.6 mm; the maximum displacement of sacroiliac joint in S2 AI group was 0.22 mm, and that of sacrum was 0.24 mm; the maximum displacement of the sacroiliac joint in S1 + S2 group was 0.06 mm, and that of sacrum was0.16 mm. Stress data showed that the stress in the internal fixation was mainly distributed at the sacroiliac joint, and the stress result was S2AI group＞S, group＞S, + S2 group, of which the maximum stress value was 52.8 MPa in S1 group, 62.1 MPa in S2AI group, and 38.2 MPa in S1 + S2 group. The stress around the screws was also concentrated at the sacroiliac joint, and the stress result was S1 group＞S2AI group＞S1 + S2 group, of which the maximum stress value was 56.8 MPa in S1 group, 11.2 MPa in S2AI group, and 5.8 MPa in S1 + S2 group. Conclusions Single S1 screw, single S2 AI screw and S, screws combined S2 screws can be used for the treatment of unilateral C type sacroiliac joint dislocation. Early weight bearing of single S1 screw might lead to the risks of increased sacroiliac joint displacement and internal fixation failure. S2 AI screw fixation and S1 + S2 screw fixation have similar biomechanical strength, allowing early weight-bearing and contributing to better postoperative rehabilitation.

Comparison of clinical complications of iliac screw fixation versus S2 alar-iliac screw / 局解手术学杂志

Objective To compare the clinical complications between S2 alar-iliac(S2AI) screw and iliac screw(IS) fixation technique.Methods The data of 65 patients who were diagnosed as degenerative scoliosis and underwent spinopelvic fixation in our hospital from August 2010 to July 2012 were retrospectively reviewed.These patients were divided into the iliac screw fixation group (IS group) with 43 patients and the S2 alar iliac fixation group (S2AI group) with 22 patients according to different methods.The complications included screw loosening,screw breakage,acute infections,delayed wound infection and persistent pain over the gluteal region occurring longer than 3 months postoperatively were recorded.Results There were 8cases with screw loosening and 13 cases with gluteal pain in IS group,while there were no screw loosening and only 2 cases with gluteal pain in S2AI group.The average onset of gluteal pain were 11.8 months postoperatively in the IS group and 18 months postoperatively in the S2AI group.It showed that the absolute risk reduction(ARR) of screw loosening and late pain in the S2AI group was 18.6%,which was lower than 21.1% in the IS group. In the IS group, there were a total of 5 cases of delayed wound infection. Finally,3 caes of them were cured by irrigation and debridement only.and the other 2 cases were cured by irrigation and debridement with implant removal.There were no cases of delayed wound infection in the S2AI group.Conclusion The S2AI technique is associated with significantly less clinical and radiographic complications when compared with the iliac screws technique,it is a kind of internal fixation of spine and pelvis,which is worthy of being popularized by spine surgeons.

Free Hand Insertion Technique of S2 Sacral Alar-Iliac Screws for Spino-Pelvic Fixation: Technical Note, Acadaveric Study

A rigid spino-pelvic fixation to anchor long constructs is crucial to maintain the stability of long fusion in spinal deformity surgery. Besides obtaining immediate stability and proper biomechanical strength of constructs, the S2 alar-iliac (S2AI) screws have some more advantages. Four Korean fresh-frozen human cadavers were procured. Free hand S2AI screw placement is performed using anatomic landmarks. The starting point of the S2AI screw is located at the midpoint between the S1 and S2 foramen and 2 mm medial to the lateral sacral crest. Gearshift was advanced from the desired starting point toward the sacro-iliac joint directing approximately 20degrees angulation caudally in sagittal plane and 30degrees angulation horizontally in the coronal plane connecting the posterior superior iliac spine (PSIS). We made a S2AI screw trajectory through the cancellous channel using the gearshift. We measured caudal angle in the sagittal plane and horizontal angle in the coronal plane. A total of eight S2AI screws were inserted in four cadavers. All screws inserted into the iliac crest were evaluated by C-arm and naked eye examination by two spine surgeons. Among 8 S2AI screws, all screws were accurately placed (100%). The average caudal angle in the sagittal plane was 17.3+/-5.4degrees. The average horizontal angle in the coronal plane connecting the PSIS was 32.0+/-1.8degrees. The placement of S2AI screws using the free hand technique without any radiographic guidance appears to an acceptable method of insertion without more radiation or time consuming.