Objective To provide the anatomic basis for thelag screw placement in the anterior column of the acetabulum. Methods Twenty-two pelvis specimens with 44 acetabula of the native adult cadavers were studied. The anthropometric measurement was performed on 44 acetabula to determine the shape of the transverse section of the anterior column of the acetabulum, the optimal entry point for the lag screw on the outer table of the ilium, the direction of the screw, and the distance from the entry point to the obturator groove. Results The transverse section of the anterior column of the acetabulum was almost triangle-shaped. The path for the lag screw placement was 10.5±0.8 mm in diameter. The optimal entry point on the posterolateral ilium for the screw fixation was found toexist 9.2±2.4 mm superior to the line between the anterior superior iliac spine and the greater sciatic notch and 38.5±3.8 mm superior to the greater sciatic notch. The distance from the entry point to the obturator groove was 84.1±6.2 mm. The inclination of the lag screw was 54.2±5.5° at the caudal direction in the sagittal plane and 40.7±3.8° in the horizontal plane. The device for the safe screw placement in the anterior column was designed. Conclusion The above datacan facilitate an insertion of one 6.5 mm lag screw into the anterior acetabular column and minimize the risk of articular violation or cortical penetration, which has a narrow margin of safety. The safe length of the lag screw should be 70 mm.The optimal entry point on the posterolateral ilium for the screw fixationis determined to be 10 mm superior to the line between the anterior superior iliac spine and the greater sciatic notch and 40 mm superior to the greater sciatic notch. The inclination of the lag screw should be 55° at the caudal direction in the sagittal plane and 40° in the horizontal plane. It is safe to place thelag screw in the anterior column with the help of the targeting device.
ObjectiveTo develop an instrument for sacroiliac joint fixation with less injury and less complications. MethodsFirstly, 18 adult pelvic specimens (8 males and 10 females) were used to measure the anatomical data related to the locking plates and locking screws on the sacrum and ilium, and the polyaxial locking plate screw system of the sacroiliac joint was designed according to the anatomic data. This system was made of medical titanium alloy. Then 4 adult male plevic specimens were harvested and the experiment was divided into 3 groups:group A (normal pelvic), group B (the dislocated sacroiliac joint fixed with sacroiliac screws), and group C (the dislocated sacroiliac joint fixed with polyaxial locking plate screw system). The vertical displacement of sacroiliac joint under the condition of 0-700 N vertical load and the horizontal displacement on angle under the condition of 0-12 N·m torsional load were compared among the 3 groups by using the biological material test system. Finally, the simulated application test was performed on 1 adult male cadaveric specimen to observe soft tissue injury and the position of the locking plate and screw by X-ray films. ResultsAccording to the anatomic data of the sacrum and ilium, the polyaxial locking plate screw system of the sacroiliac joint was designed. The biomechanical results showed that the vertical displacement of the sacroiliac joint under the condition of 0-700 N vertical load in group A was significantly bigger than that in group B and group C (P < 0.05), but there was no significant difference between group B and group C (P>0.05). The horizontal displacement on angle under the condition of 0-12 N·m torsional load in group A was significantly less than that in group B and group C (P < 0.05). The horizontal displacement on angle under the condition of 0-6 N·m torsional load in group B was bigger than that in group C, and the horizontal displacement on angle under the condition of 6-12 N·m torsional load in group B was less than that in group C, but there was no significant difference between group B and group C (P>0.05). The test of simulating application showed that the specimen suffered less soft tissue injury, and this instrument could be implanted precisely and safely. ConclusionThe polyaxial locking plate screw system of the sacroiliac joint has the advantages of smaller volume and less injury; polyaxial fixation enables flexible adjustment screw direction. The simulated application test shows satisfactory fixing effect.
Objective To evaluate the accuracy of pedicle guide device for the placement of the pedicle screws. Methods Pedicle guide device was designed and made for the anatomical trait of pedicle. The 3-Danatomical data of the thoracic pedicles were measured by multislice spiral CT in two embalmed human cadaveric thoracic pedicles spine(T1 -T10). Depending on transverse section angle(TSA) and sagittal section angle(SSA) of pedicle axis, the degree of horizontal dial and sagittal dial were adjusted in the guide device. The screws wereinserted bilaterally in the thoracic pedicles by using the device. After pulling the screws out, the pathways were filled with contrast media. The TSA and SSA of developed pathways were measured. Results Analysis of the difference between pedicle axis and developed pathway was of no statistical significance(P＞0.05). Conclusion The guide device could be easilyoperated and guarantee high accuracy of the pathways of screws and the incidence of pedicle penetration could be significantly reduced.
Objective To ascertain whether augmentation pedicle screw fixation with polymethylmethacrylate (PMMA) can enhance the stability of unstable thoracolumbar burst fractures of osteoporotic spine. Methods Six fresh frozen female osteoporotic spines (T10-L5) were harvested and an anterior and posterior columnunstable model of L1 was made. Each specimen was fixated with plate and the stability test were performed by flexion, extension, axial rotation and lateral bending. The test of fatigue was done with MTS 858.The tests were repeated after screws were augmented with PMMA. To compare the biomechanical stability of 6 different conditions:○anormal specimens(control), ○bdefectmodel fixed with plate, not augmented and not fatigued, ○cafter fatigued, not augmented, ○dscrews augmented with PMMA, not fatigued, ○e after augmented and fatigued. ResultsIn ○b,○d and ○e conditions, the ranges of motion(ROM) were 6.23±1.56，4.49±1.00，4.46±1.83 inflexion and 6.60±1.80，4.41±0.82，4.46±1.83 in extension. There was no significant difference (Pgt;0.05), they were significantly smaller than those in ○a and ○c conditions (8.75±1.88，1.47±2.25 and 8.92±2.97，12.24±3.08) (Plt;0.01).Conclusion The results demonstrated that augmentation pedicle screws fixation with PMMA can increase the stability of osteoporotic spine.
OBJECTIVE: To observe the early clinical results with degenerative lumbar instability treated with transpedical screw fixation and intertransverse process autogenous bone grafting. METHODS: From September 2000 to February 2002, 19 patients (5 males and 14 females) of degenerative lumbar spine instability were treated with decompression for spinal canal stenosis, transpedical screw fixation and intertransverse process autogenous bone grafting. The locations of degenerative lumbar spine instability were between L4 and L5 in 10 patients, between L3, L4 and L5 in 4 cases, between L3 and L4 in 3 cases, between L5 and S1 in 2 cases. The results were evaluated after operation. The preoperative clinical symptoms disappeared completely as excellent results, relieved obviously as good results, improved as fair results and unrelieved or worsened as poor results. RESULTS: Seventeen patients were followed up for 4-18 months with an average of 8.1 months. The results of the treatment were excellent in 12 patients, good in 4 patients and fair in 1 patient. The excellent and good rate was 94.1%. Intertransverse process arthrodesis was obtained after 6 months of operation in all cases. No loosened and broken instruments occurred. CONCLUSION: The advantages of degenerative lumbar spine instability treated with transpedical screw fixation and intertransverse are reliable fixation, high successful rate of fusion and less influence on spinal canal. The above results show satisfactory clinical outcome.
OBJECTIVE: To introduce a method to treat kyphosis with universal spine system (USS) and to evaluate its clinical effect. METHODS: From January 2000 to September 2002, 31 patients with kyphosis were treated with "one-stage total vertebral wedge-shaped osteotomy" and internal fixation of USS. The average follow-up time was 12 months (6-31 months). We observed the clinical effect with the spinal column Cobb before operation and after operation, and the osteotomy confluence rate. RESULTS: In 31 patients, the average angle (Cobb) was 89 degrees before operation and 74 degrees after operation; the average rate of correction was 83.15% and the average rate of osteotomy confluence was 96.77%. No screw and rod broke and loosened. CONCLUSION: The USS is the reliable internal fixation instrument for the treatment of kyphosis, can increase the osteotomy confluence rate and improve correcting rate.
Objective To compare the curative effect of posterior lumbar interbody fusion with autologous il iac crest to that of interbody fusion cage for adult instabil ity of lower lumbar. Methods From February 2003 to October 2006,60 inpatients with lower lumbar instabil ity were treated. Patients were randomized into 2 groups: bone-graft group (n=28) was treated with posterior lumbar interbody fusion with two autologous il iac crests, while cage group (n=32) was treated with posterior lumbar interbody fusion with two quadrate cages. In the bone-graft group, 17 males and 11 females aged (52.78 ± 10.50) years with 3-16 months of disease course, there were 12 cases of degenerative instabil ity, 14 isthmus sl it ol isthe and 2 iatrogenic instabil ity, including 1 case of L3,4, 17 cases of L4,5 and 10 cases of L5, S1. Relative disc space height was (23.24 ± 6.62) mm, disc space activity was (10.50 ± 5.07)º, sagittal saw sl ippage distance was (4.50 ± 1.15) mm and the JOA score was 18.56 ± 2.68. In the cage group, 19 males and 13 females aged (51.75 ± 10.44) years with 3.5-14.0 months of disease course, there were 16 cases of degenerative instabil ity, 14 isthmus sl it ol isthe and 2 iatrogenic instabil ity, including 16 cases of L4,5 and 16 cases of L5, S1. Relative disc space height was (24.34 ± 7.22) mm, disc space activity was (11.12 ± 5.67)º, sagittal saw sl ippage distance was (4.38 ± 0.75) mm and the JOA score was 19.00 ± 4.12. There was no significant difference between the two groups in termsof age, gender, JOA score, disc space activity and relative disc space height preoperatively (P gt; 0.05). Results All patients received the follow-up at the 1st, 3rd, 6th and 12th month postoperatively. There was no significant difference in operation time and hemorrhage amount between the two groups (P gt; 0.05), but significant difference in the cost of operation (P lt; 0.01). Two cases in the bone-graft group suffered donor site pain and received no treatment. Three cases in the bone-graft group and 2 cases in the cage group had symptom of nerve injury 1-2 days after surgery, which were cured after expectant treatment. There were no pseudoarticulation formation, intervertebral space infection and cage aversion in both groups. Significant difference of relative disc space height was found in each group pre- and post- operatively (P lt; 0.01) and significant differences were evident between the two groups at any of the time points (P lt; 0.01). One month after operation, there was significant difference between the two groups (P lt; 0.05). There was also significant difference at the 3rd, 6th and 12th month after operation (P lt; 0.01). No sign offusion was found in each group at the 1st and 3rd month after operation. In bone-graft group, there were 7 vertebral fusion cases 6 months after operation and 23 vertebral fusion cases 12 months after operation. In cage group, there were 8 vertebral fusion cases 6 months after operation and 29 vertebral fusion cases 12 months after operation. There was no significant difference in the rate of fusion at 6 and 12 months follow-up between the two groups (P gt; 0.05). Significant difference of JOA scores was found in each group pre- and post- operatively (P lt; 0.05). And no significant difference in JOA scores at 1, 3, 6, and 12 months follow-up was evident between the two groups (P gt; 0.05). Conclusion There is no significant difference between the two groups in the fusion time, the fusion rate and the cl inical symptoms alleviation, indicating autologous il iac crest is appl icable to interbody fusion for the treatment of adult instabil ity of lower lumbar and good therapeutic effect can be achieved with no immunoreaction and lower cost.
Objective To compare the effectiveness of biplanar vertical fixation and inverted triangle fixation with hollow screw for Pauwels type Ⅲ femoral neck fracture in young and middle-aged patients. Methods The clinical data of 55 young and middle-aged patients with Pauwels type Ⅲ femoral neck fracture between June 2021 and December 2022 was retrospectively analyzed. All patients were treated with closed reduction and internal fixation with hollow screws, 25 cases were treated with biplanar vertical fixation (study group), 30 cases with inverted triangle fixation (control group). There was no significant difference in gender, age, affected side, cause of injury, underlying diseases, and time from injury to operation between the two groups (P>0.05). The operation time, intraoperative blood loss, fluoroscopy times, guide needle puncture times, starting time of weight bearing, time of full weight bearing, time of fracture healing, and complications were recorded and compared between the two groups. The hip joint function was evaluated by Harris score at 1 day, 6 months, 12 months after operation, and at last follow-up, and the pain relief was evaluated by visual analogue scale (VAS) score. The femoral neck shortening was measured on the X-ray film at last follow-up. Results All patients were followed up 12-31 months (mean, 22.0 months), and there was no significant difference in follow-up time between the two groups (P>0.05). The operation time, intraoperative blood loss, and fluoroscopy times in the study group were higher than those in the control group, but the difference was not significant (P>0.05). The guide needle puncture times in the study group was more than that in the control group, and the time of starting weight bearing and the time of full weight bearing in the study group were shorter than those in the control group, the differences were significant (P<0.05). Bony healing was achieved in both groups, and there was no significant difference in fracture healing time between the two groups (P>0.05). No osteonecrosis of the femoral head and incision-related complication was found in the two groups during follow-up, and the femoral neck shortening length in the study group was significantly shorter than that in the control group at last follow-up (P<0.05). There was no significant difference in Harris score between the two groups at 1 day after operation (P>0.05), and the Harris score of the study group was significantly better than that of the control group at other time points (P<0.05); there was no significant difference in VAS score between the two groups at each time point after operation (P>0.05). Conclusion Compared with the inverted triangle fixation, the treatment of Pauwels type Ⅲ femoral neck fracture with biplanar vertical fixation can effectively reduce femoral neck shortening without affecting fracture healing, and improve hip joint function in early stage.
Objective To evaluate the biomechanical effect of a self-made iliac screw plate on the stability of lumbo-iliac fixation construct before and after fatigue loading. Methods Twelve fresh lumbo-pelvic specimens from donated adult cadavers with formalin embalm were used in the study. According to whether use the iliac screw plate or not, the specimens were randomly assigned into group A (with iliac screw plate, n=6) and group B (without iliac screw plate, n=6). The bone mineral density (BMD) of L1-4 was measured using dual-energy radiograph absorptiometry. The pedicle screw and iliac screw fixation were given at L3-5, and bilateral facetectomy and diskectomy at L5, S1 level were performed to prepare the model of the intervertebral destabilization. The biomechanical testing was conducted on a material testing machine under 0-600 N compression and — 7-7 N · m torsion loading modes for the initial compressive stiffness and torsional stiffness evaluation. And then 20 000 cyclic compressive loading of 40-400 N was given to the specimen, the stiffness evaluation was repeated. Then the maximum pull-out strength of screws at every level was measured and compared. Gross observation and radiological observation were performed during experiment. Results The BMD values of groups A and B were (1.15 ± 0.13) g/cm2 and (1.12 ± 0.11) g/ cm2 respectively, showing no significant difference between 2 groups (t=0.428, P=0.678). All pedicle screws and iliac screws were inserted in good position; no loosening or breaking of screw was observed during loading. After fatigue loading, the incidence of halo ring around the iliac screws of groups A and B was 16.7% (1/6) and 50.0% (3/6), respectively. The compressive stiffness and torsional stiffness after fatigue loading were significantly lower than those in initial state in groups A and B (P lt; 0.05); there was no significant difference in compressive stiffness and torsional stiffness between groups A and B before fatigue loading (P gt; 0.05). However, group A had higher compressive stiffness than group B (t=2.664, P=0.024) after fatigue loading, and there was no significant difference in torsional stiffness between 2 groups (t=0.410, P=0.690). No significant difference was found in screw pull-out strength of pedicle screws at L3, L4, and L5 levels between groups A and B (P gt; 0.05); however, the pull-out strength of the iliac screws in group A was significantly higher than that in group B (t=3.398, P=0.007). In groups A and B, the pull-out strength of L3 screw was significantly lower than that of L4 and L5 screws (P lt; 0.05). In group A, pull-out strength of the iliac screws was significantly higher than that of L3, L4, and L5 screws (P lt; 0.05); in group B, the pull-out strength of iliac screws was significantly lower than that of L4 and L5 screws (P lt; 0.05). Conclusion In the lumbo-iliac reconstruction, the use of iliac screw plate could resist iliac screw loosening, therefore, it has the potential to increase the stability of lumbo-iliac fixation construct.
Objective To develop a high-accuracy, better-safety and low-cost cervical pedicle locator system for guiding cervical pedicle screw placement. Methods Cervical pedicle screw locator system was made of stainless steel. Ten cervical specimens from voluntary donation were divided into two groups according to compatibil ity design: control group inwhich 60 screws were planted into C2-7 by free hand; and experimental group in which 60 screws were planted into C2-7 under the guidance of three-dimensional locator system. The condition of screw insertion was observed and the accuracy was evaluated by the integrity of pedicle walls. Results In the control group, 32 screws (53.33%) were placed inside the pedicles and 28 (46.67%) were outside; 9 screws (15.00%) led to nerve root injury, 5 screws (8.33%) caused vertebral artery injury and no spinal cord injury occurred; and the qual ification ratio of screw insertion was 76.67% (excellent 32, fair 14, poor 14). While in the experimental group, 54 screws (90.00%) were placed inside the pedicles and 6 (10.00%) were outside; 1 screw (1.67%) caused vertebral artery injury and no nerve root injury and spinal cord injury occurred; and the qual ification ratio of screw insertion was 98.33% (excellent 54, fair 5, poor 1). There was significant difference between the two groups (P lt; 0.05). Conclusion Cervical pedicle screw locator system has the advantages of easy manipulation, high accuracy of screw placement and low cost. With further study, it can be appl ied to the cl inical.