Objective To review the biomechanics of internal fixators for proximal humeral fractures, and to compare the mechanical stabil ity of various internal fixators. Methods The l iterature concerning the biomechanics of internal fixators for proximal humeral fractures was extensively analyzed. Results The most important things for best shoulder functional results are optimal anatomical reduction and stable fixation. At present, there are a lot of methods to treat proximal humeral fractures. Locking-plate exhibites significant mechanical stabil ity and has many advantages over other internal fixators by biomechanical comparison. Conclusion Locking-plate has better fixation stabil ity than other internal fixators and is the first choice to treat proximal humeral fractures.
Objective To investigate the cl inical appl icabil ity and value of internal fixator for the reconstruction of lumbar isthmus in the treatment of lumbar vertebral spondylolysis and to lay a fundation for its cl inical appl ication. Methods Sixteen healthy goats weighing 22.65-31.22 kg were selected to establ ish the models of vertebral spondylolysis at L5, which thereafter were randomized into two groups (n=8): bone graft group in which 0.8-1.1 g fresh autogenous bone was transplanted into the isthmus spondylolysis area, and internal fixation with bone graft group in which internal fixator was installed before transplanting 0.8-1.1 g fresh autogenous bone into the isthmus spondylolysis area. All animals were killed 8 weeks after operation to receive imaging, topographic anatomy and histology detection. Meanwhile, biomechanics test was performed by using 5 donated vertebral body specimens (4 males and 1 female aged 35-51 years old). The left isthmus of L5 vertebra was transected to serve as lumbar vertebral spondylolysis model. A mini-displacement sensor was put at the transected ends of the isthmus. Then loading was conducted with a constant velocity of 2 mm/min by electronic omnipotent tester simulating the direction of fixation force of the internal fixator, and the deformation value of the transected ends was collected by a dynamic data collector and analyzer. The loading wascontinued until the vertebra specimens were damaged. The deformation of displacement sensor and the closure of transected ends of the lumbar isthmus were observed. Results All the goats behaved normally shortly after operation, and no nerve injury induced by operation and no wound infection occurred. Bilaterally obl ique X-ray films of lumbar vertebra and topographic anatomy 8 weeks after operation showed the fusion rate of the internal fixation and bone graft group and the bone graft group was 100% and 62.5%, respectively, indicating there was a significant difference (P lt; 0.05). Histology observation showed 3 goats in the bone graft group presented empty bone trabecula, empty bone lacuna and the disappearance of osteocytes at the transected ends of lumbar isthmus; while in the internal fixation and bone graft group, the bone trabecula grew into cancellous structures with hematopoietic and fatty bone marrow tissue inside, and parts of the bone trabecula had various degrees of mosaic-l ike pattern. During the upload, the biomechanics test and data processing results showed when the external load was 40 N, the deformation of displacement sensor was identified and the gap between the transected ends of lumbar isthmus started to close; then with the increase of external load, the displacement sensor tended to ascend in a l inearity manner; while when the external load was 212 N, the displacement sensor had no further deformation, the gap between the transected ends of lumbar isthmus wascompletely closed, and the pressor effect appeared. Conclusion The internal fixator for the reconstruction of lumbar isthmus has mechanical effects of stabil izing and elevating pressure with a high fusion rate.
【Abstract】 Objective To develop a new internal fixator Ni-Ti shape memory alloy scaphoid arc nail (NT-SAN)for fracture of the scaphoid waist and to test the biomechanical characteristics of NT-SAN so as to provide the biomechanicalproofs for cl inical appl ication. Methods According to the acquired measurements and anatomic features of the scaphoid in Chinese population, a special internal fixator—— NT-SAN was designed. The biomechanical intensity experiment: The 32 specimens of fractures of the waist of scaphoid were divided randomly into 4 groups (n =8). Reduction and internal fixation were carried out in each specimen, with Kirschner wires (Group A), with Kirschner wires stapl ing (Group B), with screw (Group C) and with NT-SAN (Group D). Their fixed strength was tested by a hydrol ic pressure biomechanical system AG-1. The biomechanical fatigue experiment: The models of 24 waist scaphoid fracture of adult upper l imbs specimens were made and randomly divided into 3 groups (n =8). Fracture was fixed with Kirschner wire stapl ing (Group E), with screw(Group F) and with NTSAN(Group G). Wrist joint was vertically pressured load of 98 N, palmar flexion and dorsal extension motion was simulated;the range of movement was from palmar flexion 5° to dorsal extension 30° and the frequency was 2 000 cycles. Displace data offragment were measured at every 500 cycles. Finally, the biomechanical features of NT-SAN were evaluated according to thetested data. NT-SAN was used to treated 1 patient with fracture of the waist of scaphoid, who was typed as Ⅱ b according to Herbert classification. Results The biomechanical tests showed that the traction forces were (15.18±3.55), (36.04±4.30),(64.88±11.62), (65.84±12.22) N and (20.28±12.09), (75.95±47.64), (120.91±26.68), (130.21±31.55) N when the displacements of the fracture l ines distracted in 1 mm/min were 1 mm and 2 mm; showing significant differences between Group D and groups A, B (P lt; 0.05), and showing no significant difference between Group D and Group C (P lt; 0.05). The biomechanical fatigue experiment showed that there were significant differences between Group G and groups E, F(P lt; 0.05) according to the measuredresults of the displacements of the fracture l ines. When wrist joint were circularly moved; showing significant differences between Group G and Group E(P lt; 0.05) after 500 circular movements, and showing significant differences between Group G and Group F(P lt; 0.05) after 1 500 circular movements according to the measured results of the “stage-shape” displacements in the fracture position. Incision healed by first intention and the X-ray films showed good NT-SAN fixation 3 months after followup.Conclusion The design of NT-SAN is in accordance with the anatomic features of the scaphoid. The fixed strength can meet the demand of the biomechanics and the range of fatigue strength can meet the demand of bony union.
【Abstract】 Objective To determine the three-dimensional stabil ity of atlantoaxial reconstruction withanterior approach screw fixation through C2 vertebral body to C1 lateral mass and Gall ie’s technique (ASMG) for C1,2instabil ity. Methods Twenty-five human cadaveric specimens (C0-3 ) were divided randomly into 5 groups (n=5). Thethree-dimensional ranges of motion C1 relative to C2 were measured under the five different conditions：the intact state group (group A), type II odontoid fracture group (group B), posterior C1,2 transarticular screw fixation group (group C), ASM group (group D) and ASMG group (group E). The three-dimensional ranges of motions C1 relative to C2 by loading ± 1.5 Nm were measured under the six conditions of flexion/extension, left/right lateral bending, and left/right axial rotation. The obtained data was statistically analyzed. Results In each group, the three-dimensional ranges of motion C1 relative to C2 under the six conditions of flexion/extension, left/right lateral bending, and left/right axial rotation were as follows: in group A (8.10 ± 1.08), (8.49 ± 0.82), (4.79 ± 0.47), (4.93 ± 0.34), (28.20 ± 0.64), (29.30 ± 0.84)°; in group B (13.60 ± 1.25), (13.80 ± 0.77), (9.64 ± 0.53), (9.23 ± 0.41), (34.90 ± 0.93), (34.90 ± 1.30)°; in group C (1.62 ± 0.10), (1.90 ± 0.34), (1.25 ± 0.13), (1.37 ± 0.28), (0.97 ± 0.14), (1.01 ± 0.17)°; in group D (2.03 ± 0.26), (2.34 ± 0.49), (1.54 ± 0.22), (1.53 ± 0.30), (0.80 ± 0.35), (0.76 ± 0.30)°; in group E (0.35 ± 0.12), (0.56 ± 0.34), (0.44 ± 0.15), (0.55 ± 0.16), (0.43 ± 0.07), (0.29 ± 0.06)°. Under the six conditions, there were generally significant differences between group A and other four groups, and between group B and groups C, D and E (P lt; 0.001), and between group E and groups C, D in flexion/ extension and left/right lateral bending (P lt; 0.05). There was no significant difference between group E and groups C, D in left/right axial rotation (P gt; 0.05). Conclusion In vivo biomechanical studies show that ASMG operation has unique superiority in the reconstruction of the atlantoaxial stabil ity, especially in controll ing stabil ity of flexion/extension and left/right lateral bending, and thus it ensures successful fusion of the implanted bone. It is arel iable surgical choice for the treatment of the obsolete instabil ity or dislocation of C1, 2 joint.
Objective To investigate the cl inical outcomes of lumbar spondylol isthesis associated with lumbar spinal stenosis through decompressive laminectomy, spondylol ithesis reduction system (SRS) internal fixation, single posteriolateralVigor Spacer threaded fusion cages and intertransverse process arthrodesis bone grafting. Methods From June 2002 to June 2006, 58 cases of lumbar spondylol isthesis were treated with decompressive laminectomy, fixed by SRS instrumentation, posterior installed with interbody Vigor Spacer Cage and bone grafted between intertransverse process arthrodesis. There were 47 males and 11 females, aged 32-66 years old (45.8 on average). The course of disease was 3 months to 7 years, with an medium course of 25 months. Accoding to the Meyerding standard, 38 cases were classified as degree I and 20 as degree II. Spondylol isthesis between L4 and L5 covered 21 cases and between L5 and S1 covered 37 cases. There were 44 cases of lumbar spondylol isthesis and 14 of degenerative lumbar spondylol isthesis. The intervertebral height was 1.5-10.5 mm with the average of 5.1 mm. Results All patients’ incisions obtained heal ing by first intension after operation. The operation time was 50-90 minutes with an average of 65 minutes. The blood loss was 200-500 mL with an average of 250 mL. The patients were followed up for 10-38 months with an average of 23.6 months. According to the Macrab criteria, 54 cases were excellent, 3 good, 1 fair and the choiceness rate was 98.3%. According to the Meyerding classification, 38 cases of degree I and 19 out of 20 cases of degree II obtained complete reduction, and the rate of complete reduction was 98.3%. There were 57 (98.3%) cases which fused well 3-6 months after operation. The intervertebral height resumed to 9.6-12.5 mm with an average of 11.6 mm, and no intervertebral height loss was found. Conclusion The treatment of lumbar spondylol isthesis with decompressive laminectomy, SRS internal fixation, single posteriorolateral Vigor Spacer threaded fusion cage and bone grafting has excellent cl inical results and stable reduction.
Objective To evaluate the effect of self-designed antirotation reduction internal fixator(ARRIF) on treating different spine segment fracture.Methods From August 1999 to March 2003, 76 patients(48 males and 28 females, aged from 22 to 59 with an average of 34.1) with thoracolumbar fracture were operatively treated by ARRIF. The follow-up period ranged from 6 to 21 months(15 months in average). Classification according to injury segment: flexion compression racture 27 cases, burst fracture 42 cases, flexion distraction injury 3 cases, flexion revolving type fracture dislocation 2 cases, shear force type dislocation 2 cases. Classification according Frankel’s grade:A grade 16 cases, B grade 15 cases, C grade 27 cases, D grade 10 cases, E grade 8 cases.Operation duration, volume of bleeding, incidence postoperation complication and effect of reduction fixation were observed. Results The operation duration of ARRIF was 1.2 h in average, and there was about 200 ml volume of bleeding during operation. The nerve function showed one Frankel’s grade improvement after operation were as follows:A grade 8 cases(50%), B grade 11 cases (73.3%), C grade20 cases(74.1%), D grade 3 cases (30%); 2 Frankel’s E cases have no nerve function changes.The nerve function damage have no aggravation in all the patients,the postoperation Cobb’s angle was averagely corrected 22°. The horizontal displacement of dislocation vertebrae was averagely corrected 28% in sagittal plane, the statistical analysis had significant variance(Plt;0.01).ARRIF had no complications of the breakage of screws and rods. Conclusion ARRIF proves to be a valid internal fixator in reducing and fixing different thoracic lumbar segment spine fracture.
Objective To summarize the methods andskills of anterior cervical locking plate systems in clinical application and to analyze the causes of some complications as well as give some preventive or remedial countermeasures. Methods From 1998 to 2002, 159 patients with cervical spondylotic myelopathy,fracturedislocation,tumor or tuberculosis of the cervical spine were treated with anterior locking plate systems. The complications were reviewed and analyzed. Results Ten kinds of complications related to anterior locking plate systems occurred in 21 patients. Most of the complications were caused by improperly-selecting implants, experience and technique deficiency. Conclusio The important preventive or remedial countermeasures are correctly-selecting patients, meticulous preoperative preparation, properly-selecting implants, standard and skillful manipulation and rational postoperative protection.
ObjectiveTo investigate the accuracy of the two-dimension computer-aided surgery navigation system in the lumbar pedicle screw fixation on recombinant CT section after operation. MethodsBetween February 2011 and April 2013, 218 patients undergoing lumbar spinal pedicle screw fixation were divided into 2 groups:two-dimension computer-aided surgery navigation system was used in 95 cases (the navigation group) and X-ray fluoroscopy assistant technology in 123 cases (the fluoroscopy assistant group). There was no significant difference in age, gender, and type of disease between 2 groups (P>0.05). The mean operating time, blood loss volume, and fluoroscopy times, and the one-time success rate of pedicle screw implant were observed. The sagittal screw angle (SSA), the relationship between the pedicle cortex and screw, the accuracy rate of pedicle screw, and the sagittal angle on both sides (SBA) were observed. ResultsA total of 504 screws were inserted in navigation group, 432 (85.7%) were inserted successfully at first time and 472 (85.7%) were inserted successfully at end time. A total of 656 screws were inserted in fluoroscopy assistant group, 474 (72.3%) were successfully inserted at first time, and 563 (85.8%) were inserted successfully at end time. There were significant differences in the one-time success rate and final success rate of pedicle screw implant between 2 groups (χ2=30.19, P=0.00; χ2=18.16, P=0.00). There was no significant difference in the mean operating time and the blood loss volume of pedicle screw implant between 2 groups (t=0.88, P=0.38; t=1.47, P=0.14); but the fluoroscopy times of pedicle screw implant in navigation group 0.7±0.3 were significantly less than that in fluoroscopy assistant group 1.5±1.0 (t=-8.09, P=0.00). The SSA and SBA in navigation group[(3.7±0.9)° and (1.7±0.8)°] were significantly less than those in fluoroscopy assistant group[(6.0±1.7)° and (3.5±1.6)°] (t=-26.92, P=0.00; t=-22.49, P=0.00). ConclusionThe sagittal screw angle and accuracy of pedicle screw implant can be significantly improved using the two-dimension computer-aided surgery navigation system in lumbar posterior fixation.
ObjectiveTo explore the effectiveness and safety of open arthrolysis combined with internal fixator removal for post-traumatic elbow stiffness. MethodsA retrospective analysis was made on the data of 80 cases treated by open arthrolysis for elbow stiffness between January 2010 and December 2011. The patients were divided into 2 groups:no internal fixation group (group A, n=39) and internal fixation group (group B, n=41) according to whether they underwent internal fixator removal at the same time. No significant difference was found in age, gender, affected side, injury time, elbow rigidity grade, and severity of heterotopic ossification (HO) between 2 groups (P>0.05) except for original injury type (P<0.05). The effectiveness was evaluated by the occurrence of complications including ulnar nerve symptoms, HO recurrence and re-fracture, the elbow range of motion (ROM) and the Mayo elbow performance score (MEPS). ResultsThe mean follow-up duration was 15.7 months (range, 12-18 months) in group A and 16.1 months (range, 12-20 months) in group B. Ulnar nerve symptoms in 5 cases (12.8%) and HO reccurrence in 1 case (2.6%) occurred in group A, while ulnar nerve symptoms in 4 cases (9.8%), HO recurrence 1 case (2.4%), and refracture in 1 case (2.4%) occurred in group B. The incidence of each complication showed no significant difference between 2 groups (P>0.05). Both the ROM and the MEPS at last follow-up increased significantly when compared with preoperative ones in 2 groups (P<0.05). Besides, MEPS of group A was significantly higher than that of group B (t=2.36, P=0.02), but no significant difference was found in the ROM between 2 groups at last follow-up (t=0.40, P=0.69). Based on MEPS, the results were excellent in 16 cases, good in 16 cases, fair in 6 cases, and poor in 1 case in group A with an excellent and good rate of 82.1%;the results were excellent in 10 cases, good in 25 cases, fair in 4 cases, and poor in 2 cases in group B with an excellent and good rate of 85.4%. There was no significant difference in excellent and good rate between 2 groups (χ2=0.16, P=0.69). ConclusionOpen elbow arthrolysis combined with internal fixator removal for post-traumatic elbow stiffness is safe and effective. However, measures for prevention of re-fracture should always be taken into consideration.