The present study aimed to evaluate the effect of using one-stage posterior C2 and C3 pedicle screw fixation or combined anterior C2-C3 fusion in the treatment of unstable hangman’s fracture. A total of 13 patients with unstable hangman’s fractures underwent C2 and C3 pedicle screw fixation, lamina interbody fusion or combined anterior C2-C3 fusion and imaging examinations to evaluate the fracture fixation and healing condition at three days and three months following surgery. Postoperative X-ray and computed tomography (CT) results showed high fracture reduction, good internal fixation position and reliable fracture fixation. The three-month postoperative CT showed good vertebral fracture healing. C2 and C3 pedicle screw fixation has a good curative effect in the treatment of unstable hangman’s fracture. The direct fixation of the fracture enables early ambulation by the patients.
hangman’s fracture; C2; C3; pedicle screw; instability
Opinions have varied regarding the optimal treatment of an unstable Hangman’s fracture. C2 pedicle screw instrumentation is a biomechanically strong fixation which although done through a simple posterior approach, is a technically demanding procedure. This prospective, non-randomized multicentre study included 15 consecutive patients with displaced type II traumatic spondylolisthesis of the axis. There were nine males and six females with a mean age of 37 years at surgery. The cause of injury was a road traffic accident in 11 patients and a fall from height in 4 patients. All patients had a single stage reduction and direct transpedicular screw fixation through the C2 pedicles. During follow-up, clinical evaluation and plain X-rays were performed at each visit; at 6-month follow-up, additional dynamic lateral flexion/extension views and a CT scan were performed. The average follow-up period was 32 months (range 25–56 months). At final follow-up, all patients were asymptomatic and regained a good functional outcome with no limitation of range of motion; all the patients showed solid union with no implant failure. There were no neurological complications. At 6-month follow-up, CT evaluation showed fusion in all patients and an adequate position of 28 screws. Two pedicle screws (6.6%) showed minimal (defined as <2 mm) intrusion; one into the spinal canal and the other into the vertebral foreamen. Transpedicular screw fixation through the C2 pedicles is a safe and effective method in treating type II traumatic spondylolisthesis of the axis resulting in good clinical and radiological outcomes. Adequate reduction was achieved and motion segments were preserved with its use.
Hangman’s fracture; Transpedicular screw; Motion preservation; Cervical spine
During the past 30 years various treatment protocols for hangman’s fractures have been attempted. In order to guide the management of hangman’s fractures, different classifications have been introduced. However, opinions on operative or nonoperative treatment have not yet been solidified. To evaluate both conservative and operative management of hangman’s fractures in the published literature and to provide appropriate guidelines for treatment of hangman’s fractures, a systematic review of the literature regarding the management of hangman’s fractures was performed. An English literature search from January 1966 to January 2004 was completed with reference to treatment of hangman’s fractures. The classification for treatment guidance from the literature was also reviewed. Regarding a primary therapy for hangman’s fractures, there were 20 papers (62.5%) that advocated for a conservative treatment and 11 of the remaining 12 papers suggested that conservative treatment was suitable for some stable fractures. The classification of Effendi et al. modified by Levine and Edwards was used widely. Most hangman’s fractures could be managed successfully with traction and external immobilization, especially in Effendi Type I, Type II and Levine-Edwards Type II fractures. It is necessary for Levine-Edwards Type IIa and III fractures to be treated with rigid immobilization. Only for some stable Type I and Levine-Edwards Type II injuries, nonrigid external fixation alone was sufficient. Rigid immobilization alone was necessary for most cases. Surgical stabilization is recommended in unstable cases when there is the possibility of later instability, such as Levine-Edwards Type IIa and III fractures with significant dislocation. The classification system proposed by Effendi et al. and modified by Levine and Edwards provided a clinically reasonable guideline for successful management of hangman’s fractures.
Hangman’s fracture; Traumatic spondylolisthesis of C2; Management; Systematic review
Between 1999 and 2004, 28 patients (average age: 41, range: 18–70 years) with unstable hangman’s fracture underwent anterior discectomy and fusion with internal fixation at our unit. According to the Levine-Edwards classification, all cases were unstable with type II (10 cases), type IIA (17 cases) and type III (1 case). An average follow-up of 15 months was achieved (range: 3–48 months). The average operative time was 107 min (80–131 min). No patient received blood transfusion. No patient experienced worsening neurological function postoperatively. No other intra- or postoperative complication was observed. All patients were relieved from axial pain. Neurological status improved postoperatively in all four cases with neurological deficit. Each patient showed evidence of a solid anterior C2–3 interbody fusion after six months. No bone graft or plate screws complication was observed in any of the cases during the follow-up period. In our experience the anterior approach with primary internal stabilisation may be a feasible and safe method to treat unstable hangman’s fracture.
Transpedicular screw fixation has been accepted worldwide since Harrington et al. first placed pedicle screws through the isthmus. In vivo and in vitro studies indicated that pedicle screw insertion accuracy could be significantly improved with image-assisted systems compared with conventional approaches. The O-arm is a new generation intraoperative imaging system designed without compromise to address the needs of a modern OR like no other system currently available. The aim of our study was to check the accuracy of O-arm based and S7-navigated pedicle screw implants in comparison to free-hand technique described by Roy-Camille at the lumbar and sacral spine using CT scans. The material of this study was divided into two groups, free-hand group (group I) (30 patients; 152 screws) and O-arm group (37 patients; 187 screws). The patients were operated upon from January to September 2009. Screw implantation was performed during PLIF or TLIF mainly for spondylolisthesis, osteochondritis and post-laminectomy syndrome. The accuracy rate in our work was 94.1% in the free-hand group compared to 99% in the O-arm navigated group. Thus it was concluded that free-hand technique will only be safe and accurate when it is in the hands of an experienced surgeon and the accuracy of screw placement with O-arm can reach 100%.
Pedicle screws; Image-guided surgery; Spine navigation; O-arm
Pedicle screw fixation is the most preferred method of stabilizing unstable spinal fractures. Pedicle screw placement may be difficult in presence of fractured posterior elements, deformed spine, gross instability and spinal pathology. Challenging spine-fracture fixation is defined as the presence of one or more of the following: 1) obscured topographical landmarks as in ankylosing spondylitis, 2) fractures in occipitocervical or cervicothoracic regions and 3) preexisting altered spinal alignment. We report a series of pedicle screw insertion with guidance of navigation in difficult fixation problems..
Materials and Methods:
Fourteen patients [hangman's fracture (n=3), odontoid fracture (n=4), C1C2 fracture (n=1) and spinal fracture with coexistent ankylosing spondylitis (n=6)] underwent posterior stabilization. Intraoperatively after surgical exposure, images were acquired by Iso-C 3D C-arm and transferred to navigation system. Instrumentation was performed with navigational assistance. Postoperatively, placements of pedicle screws were evaluated with radiographs and CT scan.
Sixty-seven pedicle screws (cervical, n=33; thoracic, n=6; lumbar, n=26; sacral n=2) and 15 lateral mass screws were inserted with navigation guidance. The average time of image data acquisition by Iso-C 3D C-arm and its transfer to workstation was 4 minutes (range, 2-6 minutes). Postoperative CT scan revealed ideal placement of screws in 63 pedicles (94%), grade 1 cortical breaches (<2 mm) in 3 pedicles (4.5%) and grade 2 cortical breach (2-4 mm) in one pedicle (1.5%). There were no neurovascular complications. Deep infection was encountered in one case, which settled with debridement.
Intraoperative Iso-C 3D C-arm based navigation is a useful adjunct while stabilizing challenging spinal trauma, rendering feasibility, accuracy and safety of pedicle screw placement even in difficult situations.
Computer-assisted surgery; neuronavigation; pedicle screw; spine fracture; challenging spinal trauma
A retrospective analysis of 7 patients with traumatic rotatory atlanto-axial subluxation.
Overview of Literature
Cases of traumatic rotatory atlantoaxial subluxation in children are difficult to be stabilized. Surgical challenges include: narrow pedicles, medial vertebral arteries, vertebral artery anomalies, fractured pedicles or lateral masses, and fixed subluxation. The use of O-arm and computer-assisted navigation are still tested as aiding tools in such operative modalities.
Report of clinical series for evaluation of the safety of use of the O-arm and computed assisted-navigation in screw fixation in children with traumatic rotatory atlantoaxial subluxation.
In the present study, 7 cases of rotatory atlantoaxial traumatic subluxation were operated between December 2009 and March 2011. All patient-cases had undergone open reduction and instrumentation using atlas lateral mass and axis pedicle screws with intraoperative O-arm with computer-assisted navigation.
All hardware was safely placed in the planned trajectories in all the 7 cases. Intraoperative O-arm and computer assisted-navigation were useful in securing neural and vascular tissues safety with tough-bony purchases of the hardware from the first and only trial of application with sufficient reduction of the subluxation.
Successful surgery is possible with using the intraoperative O-arm and computer-assisted navigation in safe and proper placement of difficult atlas lateral mass and axis pedicle screws for rotatory atlantoaxial subluxation in children.
Atlantoaxial joint fusion; Intraoperative computer-assisted 3D navigation; Computer-assisted three-dimensional imaging
To reconstruct highly destructed unstable rheumatoid arthritis (RA) cervical lesions, the authors have been using C1/2 transarticular and cervical pedicle screw fixations. Pedicle screw fixation and C1/2 transarticular screw fixation are biomechanically superior to other fixation techniques for RA patients. However, due to severe spinal deformity and small anatomical size of the vertebra, including the lateral mass and pedicle, in the most RA cervical lesions, these screw fixation procedures are technically demanding and pose the potential risk of neurovascular injuries. The purpose of this study was to evaluate the accuracy and safety of cervical pedicle screw insertion to the deformed, fragile, and small RA spine lesions using computer-assisted image-guidance systems. A frameless, stereotactic image-guidance system that is CT-based, and optoelectronic was used for correct screw placement. A total of 21 patients (16 females, 5 males) with cervical disorders due to RA were surgically treated using the image-guidance system. Postoperative computerized tomography and plane X-ray was used to determine the accuracy of the screw placement. Neural and vascular complications associated with screw insertion and postoperative neural recovery were evaluated. Postoperative radiological evaluations revealed that only 1 (2.1%; C4) of 48 screws inserted into the cervical pedicle had perforated the vertebral artery canal more than 25% (critical breach). However, no neurovascular complications were observed. According to Ranawat’s classification, 9 patients remained the same, and 12 patients showed improvement. Instrumentation failure, loss of reduction, or nonunion was not observed at the final follow-up (average 49.5 months; range 24–96 months). In this study, the authors demonstrated that image-guidance systems could be applied safely to the cervical lesions caused by RA. Image-guidance systems are useful tools in preoperative planning and in transarticular or transpedicular screw placement in the cervical spine of RA patients.
Cervical spine; Image guidance; Rheumatoid arthritis; Cervical pedicle screw; Transarticular screw
Despite potential advantages of three-dimensional fluoroscopy-based navigation, there still remain a lot of controversies about the indications of this technology, especially whether it is worthy of being used in placement of pedicle screws in lumbar spine. However, according to the inconsistent conclusions reported in the literature and our experiences, the traditional method relying on anatomical landmarks and fluoroscopic views to guide lumbar pedicle screw insertion is unable to meet the requirement of precise screw placement. Based on our observation, screw malposition seems to occur concomitant with vertebral axial rotation which is a ubiquitous phenomenon. Three-dimensional fluoroscopy-based navigation can provide the most valuable axial images in real-time, so it may be useful for placement of pedicle screws in lumbar spine. This study was intended to evaluate the effect of axial rotation of lumbar vertebrae on the accuracy of pedicle screw placement using the traditional method, as well as assess the value of three-dimensional fluoroscopy-based navigation in improving the accuracy. Sixteen lumbar simulation models at different degrees of axial rotation (0°, 5°, 10°, and 20°), with every four assigned the same degree, were equally divided into two groups (traditional method group and three-dimensional fluoroscopy-based navigation group). Random placement of pedicle screws was carried out, followed by CT scan postoperatively. Then the outer pedicle cortex contours were depicted from reconstructed sectional pedicle images using Photoshop. The accuracy of pedicle screw placement was evaluated by determining the interrelationship between screw trajectory and pedicle cortex (quality), and measuring the shortest distance from pedicle screw axis to outer cortex of the pedicle (quantity). Eighty pedicle screws were implanted, respectively, in each group. In traditional method group, statistical difference existed in the accuracy of pedicle screw placement at different axial rotational degrees (P < 0.05). With degrees increasing, the accuracy declined. The accuracy of three-dimensional fluoroscopy-based navigation group was higher than traditional method group in vertebrae with axial rotation (P < 0.01). In qualitative evaluation, the accuracy of the two methods had statistical difference when the degree was 20°, and in quantitative evaluation, statistical difference existed in 5°, 10°, and 20° of vertebral axial rotation.
Lumbar spine; Pedicle screw; Vertebral rotation; Three-dimensional fluoroscopy-based navigation; Accuracy
Free-hand thoracic pedicle screw placement is becoming more prevalent within neurosurgery residency training programs. This technique implements anatomic landmarks and tactile palpation without fluoroscopy or navigation to place thoracic pedicle screws. Because this technique is performed by surgeons in training, we wished to analyze the rate at which these screws were properly placed by residents by retrospectively reviewing the accuracy of resident-placed free-hand thoracic pedicle screws using computed tomography imaging. A total of 268 resident-placed thoracic pedicle screws was analyzed using axial computed tomography by an independent attending neuroradiologist. Eighty-five percent of the screws were completely within the pedicle and that 15% of the screws violated the pedicle cortex. The majority of the breaches were lateral breaches between 2 and 4 mm (46%). There was no clinical evidence of neurovascular injury or injury to the esophagus. There were no re-operations for screw replacement. We concluded that under appropriate supervision, neurosurgery residents can safely place free-hand thoracic pedicle screws with an acceptable breach rate.
Computed tomography; Free-hand; Pedicle screw; Resident; Thoracic
Intra-articular screw penetration is one complication of volar plate fixation of distal radius fractures. This study was designed to determine the most utilized imaging techniques and views during volar plating of distal radius fractures and to evaluate surgeons’ ability to detect intra-articular screw placement on static fluoroscopic images and rotational fluoroscopy.
Active members of The American Society for Surgery of the Hand were polled regarding preferred imaging techniques (fluoroscopic versus cassette radiographs) and views (rotational fluoroscopy, static orthogonal/anatomic tilt/semi-pronated imaging) during volar plating of distal radius fractures. Following the survey, volar locking plates were applied to 30 cadaveric distal radii. A single screw intentionally penetrated the radiocarpal joint in half of the specimens (15 arms) and intentionally did not penetrate the radiocarpal joint in the other half. Imaging (standard posterior-anterior (PA) and lateral views, 11° tilt PA and 22° tilt lateral views, and two 360° fluoroscopy movies) was performed utilizing a custom jig. Five blinded surgeons reviewed randomized image sets evaluating for intra-articular screw placement. Receiver operating characteristic curves were constructed to compare the reliability of each fluoroscopic projection/movie.
Among 696 survey respondents, 88% exclusively utilized fluoroscopic imaging (without cassette radiographs) and nearly 66% preferred either tilt images or rotational fluoroscopy to detect intra-articular screw penetration. In our cadaveric model, rotational fluoroscopy provided the highest sensitivity (93%) and specificity (96%) for the detection of intra-articular screw penetration. Rotational fluoroscopy was significantly more reliable (p<0.01) than most images (standard lateral, 11° PA, 22° lateral, paired PA/lateral) and trended strongly toward better reliability for all remaining images (standard PA [p=0.07], paired 11° PA/22° lateral [p=0.08], 22° tilt fluoroscopy movie [p=0.11]).
Rotational fluoroscopy improves the surgeon’s ability to detect intra-articular screw penetration during volar plating of the distal radius. No combination of imaging allowed detection of all intra-articular screws. A high level of suspicion for intra-articular screw penetration should be maintained during volar plating of distal radial fractures.
Level of evidence
Unable to be determined according to guidelines
complication; distal radius; fracture; fluoroscopy; volar plate
Internal fixation is the established dorsal standard procedure for the treatment of thoracolumbar fractures. The main problem of the procedure is the false positioning of the pedicle screws. The exact determination of pedicle screws has up to now only been possible through postoperative computed tomography. This study was intended to clarify the diagnostic value of intraoperative 3D scans after pedicle screw implantation in thoracolumbar spine surgery. The direct intraoperative consequences of the 3D scans are reported and the results of the 3D scans are compared with the postoperative computed tomography images. Intraoperative 3D scans were prospectively carried out from June 2006 to October 2008 on 95 patients with fractures of the thoracolumbar spine that have been treated with internal fixation. Screws positions were categorised intraoperatively, screws in relevant malposition were repositioned immediately. A computed tomography of the involved spinal section was carried out postoperatively for all patients. The positions of the pedicle screws were determined and compared in the axial reconstructions of both procedures. Four hundred and fourteen pedicles with enclosed screws were evaluated by the 3D scans. The time needed for carrying out the 3D scan amounts to an average of 8.2 min. Eleven screws (2.7%) in ten patients were primarily intraoperatively repositioned on the basis of the 3D scan evaluation. Two of 95 patients had to have false positions of the screws revised secondarily following evaluation of the computed tomographies. The secondary postoperative revision rate of the patients amounts to 2.1%. In relation to the number of screws, this is a revision rate of 0.5%. The postoperative computed tomographies showed 323 pedicles without cortical penetration by the screws (78.0%). Ninety-one screws penetrated the pedicle wall (22%). It was possible to postoperatively compare the position classifications of 406 pedicle screws. The CT showed 378 correct screw positions, while 28 screws were positioned falsely. On the basis of the 3D scans, 376 of 378 correct positions were correctly assessed. Twenty-one of 28 false positions could be correctly classified. The sensitivity of all 3D scans reached 91.3% and the specificity 98.2%. The position of 97.8% of the pedicle screws was correctly recognised by the intraoperative 3D scan. Nine screws were classified falsely (2.2%). The comparison of the classification results showed significantly higher error findings by the 3D scan in the spinal section T1–10 (P = 0.014). The image quality of the 3D scan correlates significantly with the width of the scanned pedicle, with the body mass index, the scanned spinal section and the extent of the fixation assembly. 3D scans showed a high accuracy in predicting pedicle screw position. Primary false placement of screws and primary neurovascular damage cannot be avoided. But intraoperative evaluation of the 3D scans resulted in a primary revision rate of 2.7% of the pedicle screws and we could lower the secondary revision rate to 0.5%.
Three-dimensional fluoroscopy; Intraoperative 3D-imaging; Pedicle screws; Thoracolumbar fracture; Spine
The management of odontoid fracture has evolved but controversy persists as to the best method for Type II odontoid fractures with or without atlantoaxial (AA) instability. The anterior odontoid screw fixation can be associated with significant morbidity while delayed odontoid screw fixation has shown to be associated with reasonable good fusion rates. We conducted a retrospective analysis to evaluate the outcome of a trial of conservative management in type II odontoid fractures without atlantoaxial instability (Group A) followed by delayed odontoid screw fixation in cases in which fusion was not achieved by conservative treatment. The outcome of type II odontoid fracture with AA subluxation (Group B) was also analysed where closed reduction on traction could be achieved and in those atlantoaxial subluxations that were irreducible an intraoperative reduction was done.
Materials and Methods:
A retrospective evaluation of 53 cases of odontoid fractures treated over a 9-year period is being reported. All odontoid fractures without AA instability (n=29) were initially managed conservatively. Three patients who did not achieve union with conservative management were treated with delayed anterior screw fixation. Twenty-four cases of odontoid fractures were associated with AA instability; 17 of them could be reduced with skeletal traction and were managed with posterior fusion and fixation. Of the seven cases that were irreducible, the initial three cases were treated by odontoid excision followed by posterior fusion and fixation; however, in the later four cases, intra operative reduction was achieved by a manipulation procedure, and posterior fusion and fixation was performed.
Twenty-six of 29 cases of odontoid fracture without AA instability achieved fracture union with conservative management whereas the remaining three patients achieved union following delayed anterior odontoid screw fixation. 17 out of 24 odontoid fracture with atlantoaxial dislocation could be reduced on traction and these patients underwent posterior fusion and fixation. Optimal or near optimal reduction was achieved by on table manipulation in four cases which were irreducible with skeletal traction. Atlantoaxial stability was achieved in all cases. All cases were noted to be stable on evaluation with x-rays at six months.
The initial conservative management and use of odontoid screw fixation only in cases where conservative management for 6–12 weeks has failed to provide fracture union have shown good outcome in type II odontoid fracture without AA instability rates. Intraoperative manipulation and reduction in patients where AA subluxation failed to reduce on skeletal traction followed by posterior fusion obviates the need for transoral odontoid excision.
Atlantoaxial dislocation; cervical spine injuries; odontoid fractures
Different navigation procedures (based on 2D-, 3D-fluoroscopy or CT modalities) with their respective limitations are established in orthopedic surgery. The hypothesis is that intraoperative matching of different modalities (fluoro and CT) increases the precision of navigated screw placement and reduces the fluoroscopy time. Vertical unstable pelvic ring fractures of 12 patients were treated with vertebro-pelvic fixations (6 in the standard technique and 6 using the fluoro-CT navigation). An optimal osseous corridor could be determined by the navigation procedure increasing the overall precision of screw placement (no misplacement in the second group as compared to one malplaced pedicle screw in the standard group). The achieved screw lengths were [(mean ± SE) 78 ± 5 vs. 53 ± 4 mm, p < 0.001). Less invasive open approaches and a reduction of fluoroscopy time (time per screw in seconds: 121 vs. 62 s) were observed. CT-fluoro-matched navigation improves the intraoperative visualization of osseous structures and increases the precision of screw placement with less radiation exposure.
Computer-assisted surgery; CT-fluoro matching; Navigation; Spino-pelvic dissociation; Pelvic fracture; Vertebro-pelvic fixation
Technical errors during navigation-assisted bone tumor resection may occur by: (1) incorrect registration of images and corresponding anatomic points of bone sent to the navigation system; and (2) incorrect fusion of two or more images that have been transported to the navigation system.
We investigated new methods of navigation surgery to minimize technical errors during the registration and image fusion processes and specifically asked whether a navigated cannula probe would reduce unnecessary soft tissue dissection, and allow percutaneous registration and implantation of a reference base tracker in the margin of bone to be resected.
We performed direct MRI-guided navigation surgery without image fusion on a patient with osteosarcoma using absorbable pins as temporary implanted bone markers that prevent artifacts on MR images.
Direct MRI-guided navigation surgery was possible using bone markers. A navigated cannula probe allowed percutaneous registration and a navigated blade-shaped probe provided a real-time check on the narrow osteotomy gap. The surgical procedure was facilitated by implantation of a reference base tracker on the margin of bone to be resected.
Our modified technique of MRI-guided navigation surgery for patients with a malignant bone tumor may reduce processing errors by increased accuracy and be helpful for joint preserving surgery.
Studies revealed that navigation systems that provided intraoperative assistance might improve pedicle screw insertion accuracy, and also implied that different systems provided different pedicle screw insertion accuracy. A systematic review and meta-analysis was conducted to focus on the pedicle screw insertion accuracy with or without the assistance of image-guided system, and the variance among the different navigation systems. Comparative studies were searched on pedicle screw insertion accuracy between conventional and navigated method, and among different navigation systems. A total of 43 papers, including 28 clinical, 14 cadaveric and 1 model studies, were included in the current study. For clinical articles, there were 3 randomized clinical trials, 4 prospective comparative studies and 21 retrospective comparative studies. The incidence of pedicle violation among computer tomography-based navigation method group was statistically significantly less than that observed among the conventional group (OR 95% CI, in vivo: 0.32–0.60; in vitro: 0.24–0.75 P < 0.01). Two-dimensional fluoroscopy-based navigation system (OR 95% CI, in vivo: 0.27–0.48; in vitro: 0.43–0.88 P < 0.01) and three-dimension fluoroscopy-based navigation system (OR 95% CI, in vivo: 0.09–0.38; in vitro: 0.09–0.36 P < 0.01) also obtained significant reduced screw deviation rate over traditional methods. Between navigated approaches, statistically insignificant individual and pooled RR values were observed for all in vivo subgroups. Pooled estimate of in vitro studies show that computer tomography-based and three-dimension fluoroscopy-based navigation system provided more accurate pedicle screw insertion over two-dimension fluoroscopy-based navigation system. Our review showed that navigation provided a higher accuracy in the placement of pedicle screws compared with conventional methods. The superiority of navigation systems was obvious when they were applied to abnormal spinal structure. Although no strong in vivo evidence has detected significantly different pedicle screw placement accuracy among the three major navigation systems, meta-analysis revealed the variance in pedicle screw insertion accuracy with different navigation methods.
Navigated spine surgery; Pedicle screw; Computer tomography; Fluoroscopy; Accuracy
Use of a pedicle screw at the level of fracture, also known as an intermediate screw, has been shown to improve clinical results in managing lumbar fracture, but there is a paucity of biomechanical studies to support the claim. The aim of this study was to evaluate the effect of adding intermediate pedicle screws at the level of a fracture on the stiffness of a short-segment pedicle fixation using monoaxial or polyaxial screws and to compare the strength of monoaxial and polyaxial screws in the calf spine fracture model.
Materials and Methods:
Flexibility of 12 fresh-frozen calf lumbar spine specimens was evaluated in all planes. An unstable burst fracture model was created at the level of L3 by the pre-injury and dropped-mass technique. The specimens were randomly divided into monoaxial pedicle screw (MPS) and polyaxial pedicle screw (PPS) groups. Flexibility was retested without and with intermediate screws (MPSi and PPSi) placed at the level of fracture in addition to standard screws placed at L2 and L4.
The addition of intermediate screws significantly increased the stability of the constructs, as measured by a decreased range of motion (ROM) in flexion, extension, and lateral bending in both MPS and PPS groups (P < 0.05). There was neither any significant difference in the ROM in the spines of the two groups before injury, nor a difference in the ROM between the MPSi and PPSi groups (P > 0.05), but there was a significant difference between MPS and PPS in flexion and extension in the short-segment fixation group (P < 0.05).
The addition of intermediate screws at the level of a burst fracture significantly increased the stability of short-segment pedicle screw fixation in both the MPS and PPS groups. However, in short-segment fixation group, monoaxial pedicle screw exhibited more stability in flexion and extension than the polyaxial pedicle screw.
Monoaxial or polyaxial; pedicular screw; lumbar spine; burst fracture; intermediate screw at fracture level
Screw fixation of pelvic ring fractures is a common, but demanding procedure and navigation techniques were introduced to increase the precision of screw placement. The purpose of this case series was the evaluation of screw misplacement rate and functional outcome of percutaneous screw fixation of pelvic ring disruptions using a 2D navigation system.
Between August 2004 and December 2007, 44 of 442 patients with pelvic injuries were included for closed reduction and percutaneous screw fixation of disrupted pelvic ring lesions using an optoelectronic 2D-fluoroscopic based navigation system. Operating and fluoroscopy time were measured, as well as peri- and postoperative complications documented. Screw position was assessed by postoperative CT scans. Quality of live was evaluated by SF 36-questionnaire in 40 of 44 patients at mean follow up 15.5 ± 1.2 month.
56 iliosacral- and 29 ramus pubic-screws were inserted (mean operation time per screw 62 ± 4 minutes, mean fluoroscopy time per screw 123 ± 12 seconds). In post-operative CT-scans the screw position was assessed and graded as follows: I. secure positioning, completely in the cancellous bone (80%); II. secure positioning, but contacting cortical bone structures (14%); III. malplaced positioning, penetrating the cortical bone (6%). The malplacements predominantly occurred in bilateral overlapping screw fixation. No wound infection or iatrogenic neurovascular damage were observed. Four re-operations were performed, two of them due to implant-misplacement and two of them due to implant-failure.
2D-fluoroscopic navigation is a safe tool providing high accuracy of percutaneous screw placement for pelvic ring fractures, but in cases of a bilateral iliosacral screw fixation an increased risk for screw misplacement was observed. If additional ramus pubic screw fixations are performed, the retrograde inserted screws have to pass the iliopubic eminence to prevent an axial screw loosening.
The current surgical therapy of midfacial fractures involves internal fixation in which bone fragments are fixed in their anatomical positions with osteosynthesis plates and corresponding screws until bone healing is complete. This often causes new fractures to fragile bones while drilling pilot holes or trying to insert screws. The adhesive fixation of osteosynthesis plates using PMMA bone cement could offer a viable alternative for fixing the plates without screws. In order to achieve the adhesive bonding of bone cement to cortical bone in the viscerocranium, an amphiphilic bone bonding agent was created, analogous to the dentin bonding agents currently on the market.
The adhesive bonding strengths were measured using tension tests. For this, metal plates with 2.0 mm diameter screw holes were cemented with PMMA bone cement to cortical bovine bone samples from the femur diaphysis. The bone was conditioned with an amphiphilic bone bonding agent prior to cementing. The samples were stored for 1 to 42 days at 37 degrees C, either moist or completely submerged in an isotonic NaCl-solution, and then subjected to the tension tests.
Without the bone bonding agent, the bonding strength was close to zero (0.2 MPa). Primary stability with bone bonding agent is considered to be at ca. 8 MPa. Moist storage over 42 days resulted in decreased adhesion forces of ca. 6 MPa. Wet storage resulted in relatively constant bonding strengths of ca. 8 MPa.
A new amphiphilic bone bonding agent was developed, which builds an optimizied interlayer between the hydrophilic bone surface and the hydrophobic PMMA bone cement and thus leads to adhesive bonding between them. Our in vitro investigations demonstrated the adhesive bonding of PMMA bone cement to cortical bone, which was also stable against hydrolysis. The newly developed adhesive fixing technique could be applied clinically when the fixation of osteosynthesis plates with screws is impossible. With the detected adhesion forces of ca. 6 to 8 MPa, it is assumed that the adhesive fixation system is able to secure bone fragments from the non-load bearing midfacial regions in their orthotopic positions until fracture consolidation is complete.
Operative therapy of intraarticular fractures of the calcaneus is an established surgical standard. The aim is an accurate reduction of the fracture with reconstruction of Boehler’s angle, length, axis and subtalar joint surface. Intraoperative 3D-fluoroscopy with the Siremobil Iso-C 3D® mobile C-arm system is a valuable assistant for accurate reconstruction of these anatomical structures. Remaining incongruities can be recognized and corrected intraoperatively. The achieved reduction can be fixed by the advantages of an internal fixator (locked-screw plate interface). In the period of October 2002 until April 2007 we operated 136 patients with intraarticular fractures of the calcaneus by means of anatomical reduction, and internal plate fixator under intraoperative control of 3D-fluoroscopy. All patients were supplied with an orthesis after the operation which allowed weight bearing of 10 kg for 12 weeks for the patients operated between October 2002 and October 2004 (Group A). Transient local osteoporosis was observed in all X-Rays at follow-up after an average of 8,6 months. Therefore we changed our postoperative treatment plan for the patients operated between November 2004 and April 2007 (Group B). Weight bearing started with 20 KG after 6 weeks, was increased to 40 KG after 8 weeks and full weight bearing was allowed after 10 weeks for these patients. In no case a secondary dislocation of the fracture was seen. No bone graft was used. At follow up the average American Foot and Ankle Society Score (AOFAS) were 81 for Group_A, compared to 84 for Group B, treated with earlier weight bearing. Autologous bone graft was not necessary even if weight bearing was started after a period of six weeks postoperatively. The combination of 3D-fluoroscopy with locked internal fixation showed promising results. If the rate of patients developing subtalar arthrosis will decrease by this management will have to be shown in long term follow up.
Computer-assisted surgery; early weight bearing; calcaneal fracture; locked plate.
The purpose of this study was to determine the efficacy of bone cement-augmented short segment fixation using percutaneous screws for thoracolumbar burst fractures in a background of severe osteoporosis.
Sixteen patients with a single-level thoracolumbar burst fracture (T11-L2) accompanying severe osteoporosis treated from January 2008 to November 2009 were prospectively analyzed. Surgical procedures included postural reduction for 3 days and bone cement augmented percutaneous screw fixation at the fracture level and at adjacent levels without bone fusion. Due to the possibility of implant failure, patients underwent implant removal 12 months after screw fixation. Imaging and clinical findings, including involved vertebral levels, local kyphosis, canal encroachment, and complications were analyzed.
Prior to surgery, mean pain score (visual analogue scale) was 8.2 and this decreased to a mean of 2.2 at 12 months after screw fixation. None of the patients complained of pain worsening during the 6 months following implant removal. The percentage of canal compromise at the fractured level improved from a mean of 41.0% to 18.4% at 12 months after surgery. Mean kyphotic angle was improved significantly from 19.8° before surgery to 7.8 at 12 months after screw fixation. Canal compromise and kyphotic angle improvements were maintained at 6 months after implant removal. No significant neurological deterioration or complications occurred after screw removal in any patient.
Bone cement augmented short segment fixation using a percutaneous system can be an alternative to the traditional open technique for the management of selected thoracolumbar burst fractures accompanied by severe osteoporosis.
Burst fracture; Fusion; Percutaneous