Although a C2 pedicle screw and a C1–2 transarticular screw are the most rigid anchors, these screws cannot be used in cases with bilateral high-riding vertebral arteries. The authors describe their recent experience using a novel method of C2–3 transuncovertebral joint screw placement for occipitocervical fixation.
Methods
A 67-year-old patient suffered myelopathy due to instability at C1–2. The patient had bilateral high-riding vertebral arteries that precluded the use of a C2 pedicle screw or a C1–2 transarticular screw.
Results
A C2–3 transuncovertebral joint screw was applied bilaterally under 3D navigation guidance. The patient’s postoperative course was uneventful, and his neurological status improved after the surgery. Bony fusion was achieved after the surgery.
Conclusions
This is the first report to describe the technique of transuncovertebral joint screw. Using a C2–3 transuncovertebral joint screw, a long screw could be used, and it provided an anchor at C3 and C2 from a posterior approach.
Despite proven biomechanical superiority and resultant superior clinical outcomes, pedicle instrumentation in cervical spine is not widely practiced due to technical difficulties, steep learning curve, and possible potential catastrophic complications due to screw misplacement. This study was undertaken with the purpose to evaluate the feasibility, accuracy, and complications of cervical pedicle screw instrumentation solely using O-arm-based 3D navigation technology.
Methods
Prospectively maintained data from a single-surgeon case series were retrospectively analyzed. All the patients had undergone cervical pedicle instrumentation under O-arm 3D navigation. Screw placement accuracy was analyzed and compared among different vertebral levels and also between different patient groups.
Results
A total of 241 cervical pedicle screws were inserted in 44 patients. Out of the 241 screws, 197 (81.74%) were inserted at the level of C3–C6 vertebrae with nearly equal distribution among the 4 vertebrae, followed by 32 (13.28%) and 12 (4.98%) screws at C2 and C7 vertebrae, respectively. After the analysis of screw placement as per Gertzbein classification, the overall breach rates were found to be 7.05% (17 screws) with 52.94% (10 screws) Grade I, 47.06% (7 screws) Grade II, and nil Grade III screw breaches.
Conclusion
The use of O-arm-based intra-operative 3D scans for navigation can make cervical pedicle screw placement reliable. High accuracy and better intra-operative control can increase surgeon’s confidence in using cervical pedicle instrumentation on more regular basis.
Graphical abstract
These slides can be retrieved under Electronic Supplementary Material.
The purpose of this study was to evaluate the efficacy and safety of percutaneous pedicle screw fixation at the fractured vertebra in the treatment of thoracolumbar fractures.
Methods
Thirty-two consecutive patients were enrolled in the study. All patients received percutaneous pedicle screw fixation, and they were randomly divided into two groups to undergo either the placement of pedicle screws into the fractured vertebra (fractured group) or not (control group). The operation time and intra-operative blood loss were recorded. Oswestry disability index (ODI) questionnaire and visual analogue scale (VAS) as clinical assessments were quantified. Radiographic follow-up was defined by the vertebral body index (VBI), anterior vertebral body height (AVBH), and Cobb angle (CA).
Results
No significant difference was observed in the operation time and intra-operative blood loss between the two groups. Clinical results (VAS and ODI scores) showed no significant difference during all the follow-up periods. In the fractured group, there were better correction and less loss of AVBH and VBI compared with the control group. However, post-operative correction of the CA immediately after surgery and the correction loss at the final follow-up showed no significant difference between the two groups.
Conclusion
Percutaneous screw fixation combined with intermediate screws at the fractured vertebra could more effectively restore and maintain fractured vertebral height, and is an acceptable, minimally invasive surgical choice for patients with type A thoracolumbar fractures.
Traditional open exposure for posterior instrumentation requires significant soft tissue mobilization and causes significant blood loss and increased recovery time. Mal-placed screws can injure nerve roots, the spinal cord, viscera, vasculature and the cardiopulmonary system. Placement of pedicle screws using a minimally invasive technique can decrease bleeding risk, damage to soft tissues, and post-operative pain. The purpose of this study is to compare the radiographic accuracy of open free-hand versus percutaneous technique for pedicle screw placement.
Methods
Consecutive patients undergoing thoracolumbar surgery from September 2006 to October 2011 with post-operative CT imaging were included in this study. Three-dimensional screw positioning within the pedicle and the vertebral body was assessed on CT. The magnitude and location of violations were measured and recorded. Facet breaches at the cephalad and caudad ends of the construct were documented and graded.
Results
Two-hundred and twenty-three patients met the inclusion criteria for a total of 1609 pedicle screws. Seven-hundred and twenty-four screws were placed using a standard open free-hand technique and 885 were placed percutaneously. There was a significant difference in overall pedicle breach rates: 7.5 % for open and 4.7 % for percutaneous techniques. The magnitude of breach was greater for the percutaneous technique compared to the open technique: 5.4 versus 3.7 mm, respectively. The difference in vertebral body breaches was also significant: 11.3 % for open and 3.6 % for percutaneous. The rates of facet breach did not significantly differ.
Discussion and conclusion
This is the largest series comparing the accuracy of percutaneous to open pedicle screw placement. The rates of pedicle, vertebral body, and facets breaches in the percutaneous group were similar to the rates in the open technique group as well as rates reported in the literature. This demonstrates that the percutaneous technique described here is an accurate alternative to standard open free-hand technique.
Pedicle screw placement is an increasingly common procedure for the correction of spine degenerative disease, deformity and trauma. However, screw placement is demanding, with complications resulting from inaccurate screw placement. While several different techniques have been developed to improve accuracy, they all have their limitations.
Methods
We examined the MySpine (Medacta International SA, Castel San Pietro, CH) patient-matched pedicle targeting guide in three cadaveric spine specimens operated on by three surgeons. A three-dimensional (3D) preoperative plan was constructed from spinal computed tomography scans, from which individualised guides were developed for the placement of Medacta Unconstrained Screw Technology pedicle screws. Following screw placement, the 3D positioning of the screws was compared to the preoperative plan against a series of pre-defined criteria.
Results
Of 46 inserted screws eligible for assessment, 91.3 % were fully inside the pedicle. There were no cases of Grade B (2–4 mm) or C (>4 mm) pedicle perforation. The mean deviation between the planned and actual screw position at the midpoint of the pedicle was 0.70 mm, the mean horizontal deviation was 0.60 mm and the mean vertical deviation was 0.77 mm. The mean angular deviation in the sagittal plane was 1.74°, versus 1.32° in the transverse plane. The mean deviation in screw depth was 1.55 mm. On all measures, the accuracy of screw placement was within the predefined criteria.
Conclusions
Our cadaver study indicates that pedicle screw placement with the system is accurate and should be investigated in larger in vitro and in vivo studies.
To assess and compare the efficacy of two minimally invasive techniques (percutaneous pedicle screw with intermediate screw vs. percutaneous pedicle screw with kyphoplasty) for spinal fracture fixation by comparing the segmental kyphosis and vertebral kyphosis angles after trauma before surgery, after surgery, and at 4-month and 12-month follow-up.
Methods
Data from 49 patients without neurological deficit treated by either percutaneous pedicle screw with intermediate screw or percutaneous pedicle screw with kyphoplasty were retrospectively analysed. The segmental kyphosis and vertebral kyphosis angles over time were calculated and correlated with the type of procedure, AO classification, lumbar or thoracic site and the age and sex of the patients.
Results
After surgery, both techniques were found to be efficacious means of bringing about a significant correction of the segmental kyphosis angle (p = 0.002) and a just significant correction of the vertebral kyphosis angle (p = 0.06), although less effectively in thoracic fractures (p = 0.004). At follow-up, the vertebral kyphosis angle was stable in both groups, while there was a significant loss of segmental kyphosis angle stability in the percutaneous pedicle screw with kyphoplasty group at 1 year (p = 0.004); fractured thoracic vertebrae maintained a greater vertebral kyphosis angle (p = 0.06) and segmental kyphosis angle (p < 0.001), than the lumbar.
Conclusion
At 1 year after surgery, the use of intermediate screws in fractured vertebrae seemed to maintain a more efficacious correction with respect to kyphoplasty, although thoracic fracture sites appear to be associated with greater post-traumatic segmental kyphosis and lesser stability in the long term after both percutaneous surgical techniques.
We evaluated the trajectory and the entry points of anterior transpedicular screws (ATPS) in the cervicothoracic junction (CTJ).
Objective
This study aimed at investigating the feasibility of ATPS fixation in the CTJ.
Summary of background data
Application of an ATPS in the lower cervical spine has been reported; however, there were no reports exploring the feasibility of anterior transpedicular screw fixation in the CTJ.
Methods
CT scans were performed in 50 cases and multiplanar reformation was used to measure the related parameters on pedicle axis view at C6–T2. Transverse pedicle angle, outer pedicle width, pedicle axis length, distance transverse intersection point (DtIP), sagittal pedicle angle, anterior vertebral body height, outer pedicle height, and distance sagittal intersection point (DsIP) were measured. The prozone of CTJ was divided into three different regions, which were named as the “manubrium region”, the region “above” and “below” the manubrium. The distribution of the trajectory of sagittal pedicle axes was recorded in the three regions and the related data were statistically analyzed.
Results
There was no statistical difference in gender (P > 0.05). The transverse pedicle angle decreased from C6 (46.77° ± 2.72°) to T2 (20.62° ± 5.04°). DtIP increased from C6 to T2. DsIP was an average of 7.17 mm. The sagittal pedicle axis lines of the C6 and C7 were located in the region above the manubrium. T1 was mainly in the manubrium region followed by the region above the manubrium. T2 was mainly located in the manubrium region followed by the region below the manubrium.
Conclusion
Implantation of ATPS at C6, C7, and some T1 is feasible through the low anterior cervical approach, while it is almost impossible to approach T2 that way.
To assess the pedicle morphology in the lower thoracic and lumbar spine in an Indian population and to determine the causes of pedicle wall violation by pedicle screws.
Methods
Computerised tomographic scans of 135 consecutive patients with thoracolumbar and lumbar spine fractures were prospectively analysed to determine the pedicle morphology. The transverse pedicle angle, pedicle diameter and screw path length at 527 uninjured levels were measured. Post-operative CT scans of 117 patients were analysed to determine the accuracy of 468 pedicle screws at 234 vertebrae.
Results
The lowest (mean ± SD) transverse pedicle width in the lower thoracic spine was 5.4 ± 0.70 mm, whereas in the lumbar spine it was 7.2 ± 0.87 mm. The shortest (mean ± SD) screw path length in lower thoracic pedicles was 35.8 ± 2.10 and 41.9 ± 2.18 mm in the lumbar spine. The mean transverse pedicle angle in the lower thoracic spine was consistently less than 5°, whereas it gradually increased from L1 through L5 from 8.5° to 30°. Forty-one screws violated the pedicle wall, due to erroneous angle of screw insertion.
Conclusions
In the current study, pedicle dimensions were smaller compared to the Western population. In Indian patients, pedicle screws of 5 mm diameter and 30 mm length, and 6 mm diameter and 35 mm length can safely be used in the lower thoracic and lumbar spine, respectively. However, it is important to assess the pedicle morphology on imaging prior to pedicle fixation.
Patients with severe spinal deformities often have small pedicle diameters, and pedicle dimensions vary between segments and individuals. Free-hand pedicle screw placement can be inaccurate. Individualized drill guide templates may be used, but the accuracy of pedicle screw placement in severe scoliosis remains unknown. The accuracy of drill guide templates and free-hand technique for the treatment of adolescent patients with severe idiopathic scoliosis are compared in this study.
Methods
This study included 37 adolescent patients (mean age 16.4 ± 1.3 years) with severe idiopathic scoliosis treated surgically at a single spine center between January 2014 and June 2017. Spinal deformities were corrected using posterior pedicle screw fixation. Patients in group I were treated with rapid prototype drill guide template technique (20 patients; 396 screws) and patients in group II were treated with free-hand technique (17 patients; 312 screws). Outcomes that included operative time, correction rate, and the incidence and distribution of screw misplacement were evaluated.
Results
Operative time in group I was 283 ± 22.7 min compared to 285 ± 25.8 min in group II (p = 0.89). The scoliosis correction rate was 55.0% in group I and 52.9% in group II (p = 0.33). Based on both axial and sagittal reconstruction images, the accuracy rate of pedicle screw placement was 96.7% in group I and 86.9% in group II (p = 0.000).
Conclusion
The drill guide template technique has potential to offer more accurate and thus safer placement of pedicle screws than free-hand technique in the treatment of severe scoliosis in adolescents.
Transpedicular screw fixation of the cervical spine provides excellent biomechanical stability. The feasibility of inserting a 3.5-mm screw in the pedicle requires a minimum pedicle diameter of 4.5 mm. This diameter allows at least 0.5 mm bony bridge medially and laterally in order to avoid pedicle violation which can result in neurovascular complications. We aim to evaluate the feasibility of this technique in Arab people since no data are available about this population.
Materials and methods
This cross-sectional study involved a retrospective review of computed tomography scans of normal cervical spines of 99 Arab adults. Ten morphometric measurements were obtained. Data were analyzed using a p value of ≤0.05 as the cut-off level of statistical significance.
Results
Our sample included 63 (63.6 %) males and 36 (36.4 %) females, with a mean age of 35.5 ± 16.5 years. The morphometric parameters of C3–C7 spine pedicles were larger in males than in females. The outer pedicle width (OPW) was <4.5 mm in >25 % of all subjects at C3–C6 vertebrae. Statistically significant differences in the OPW between males and females were noted at C3 (p = 0.032) and C6 (p = 0.004).
Conclusions
Inserting pedicle screws in the subaxial cervical spine is feasible among the majority of Arab people.
The osteoporosis prevalence in population is age related. The aim of this single-center observational study was evaluate the middle- to long-term performance of cement (PMMA) augmented fenestrated pedicle screws in elderly patients with thoraco-lumbar compressive fractures by osteoporosis.
Materials and methods
From 2011 to 2015 we treated 52 patients (20 males and 32 females) suffering from somatic osteoporotic fractures (T10–L2). The average age was 73.4 years, with an age range between 65 and 82 years. The treatment consisted of stabilization with pedicle screw augmentation with PMMA cement. Patients were clinically evaluated with Visual Analyzing System scale (VAS scale) and with low back disability questionnaire Oswestry, in pre and post surgery and during the follow up at 12 and 24 months.
Results
A total of 410 fenestrated pedicle screws with PMMA augmentation were implanted. No cases of loosening or pulling out of screws were recorded. There have been n 3 cases of thrombophlebitis, treated with oral anticoagulant drugs and 1 case of post-operative death due to ventricular fibrillation. No neurological complications occurred during the study. The mean VAS score decreased from 8.5 to 4.8 and the result remained stable during follow up. Oswestry questionnaire showed a mean decrease of low back pain of 24% in post-op period.
Conclusion
Fenestrated screws with PMMA augmentation offers a possibility to treat patients with reduced bone quality due to severe osteoporosis.
The O-arm-based navigation increases the accuracy of pedicle screw positioning and offers the possibility of performing a 3D scan before wound closure. However, repeating the 3D scan exposes the patient to additional radiation. We combined O-arm navigation with pedicle screw (PS) stimulation followed by a 3D scan to evaluate their accuracy and aimed for the creation of a protocol that maximizes the safety and minimizes radiation.
Methods
Patients had pedicle screws insertion using O-arm spinal navigation, then had PS triggered electromyography (EMG), and finally a 3D scan to evaluate the accuracy of screw position.
Results
447 screws were inserted in 71 patients. In 10 patients, 11 screws needed repositioning. Comparing results of PS triggered EMG responses to the 3D scan, we found: (a) negative stimulation response with negative 3D scan findings, corresponding to 432 acceptable screw position (96.6 %) in 58 patients (81.7 %). In these cases, the redo 3D scan could be avoided. (b) Positive stimulation response with positive 3D scan findings, corresponding to 7 unacceptable screw position (1.5 %) in 6 patients (8.4 %). In these cases, PS stimulation detected malpositioned screws that would be missed without a redo 3D scan.
Conclusion
We propose a protocol of routinely performing PS stimulation after screw insertion using spinal navigation. In case of positive stimulation, a 3D scan must be performed to rule out a probable screw mal position (6 patients 8.4 %). However, in case of negative stimulation, redo 3D scan can be avoided in 81.7 % of patients.
The aim of this study is to evaluate the effectiveness of percutaneous short fixation (PSFx) plus kyphoplasty (BP) for thoracolumbar fractures.
Methods
Thirty-six consecutive selected patients, aged 59 ± 17 years, with fresh single thoracolumbar A2, A3, and B2 AO-type fracture, received PSFx plus BP. The primary outcomes pain, and vertebral body deformity; and the secondary outcomes screw malposition, facet violation, PMMA leakage, adjacent segment degeneration (ASD) and loss of correction were evaluated. The f/up was 31 ± 7 months.
Results
Pain and kyphosis decreased and vertebral body heights increased significantly postoperation. PMMA leakage occurred in five cases; 6 (4 %) screws were grades III malpositioned in relation to pedicle; facet violation occurred in 8 (5.5 %) facets; loss of kyphosis correction was 3.68°; ASD occurred in two cases; interfacet fusion in ten (28 %) patients; Three patients were reoperated for different reasons.
Conclusions
PSFx plus BP for thoracolumbar fractures reduces significantly spinal deformity and pain with few complications.
A multi-detector computed tomography (CT) imaging system with a mobile scanner gantry in the operating room can provide intraoperative reconstructed images with a high resolution. We devised a technique for cervical pedicle screw (CPS) placement using the mobile CT system and evaluated the accuracy of this technique.
Methods
Forty-eight patients who underwent cervical fixation using CPSs were prospectively enrolled in this study. Initial pedicle probing was performed approximately to the depth of the posterior aspect of the vertebral body using fluoroscopic lateral view, and a marking pin was put in place. Intraoperative CT images were obtained to confirm whether the position of the marking pin was accurate. After adequate modification of the trajectory was performed, an appropriately sized CPS was inserted. The accuracy of the CPS was evaluated using postoperative reconstructed CT images, and compared with a historical control group of 22 patients (CPS insertion using only fluoroscopy).
Results
A total of 193 CPSs were inserted. Intraoperative CT images demonstrated that 12.4 % of the initial probings were not accurate, and modification of the trajectory was required. On postoperative CT, 92.7 % of the CPSs were found to be placed accurately: the accuracy was significantly higher than the control group (80.9 %). In the cases using intraoperative CT images, only 1.0 % of the screws were judged to show grade 2 screw misplacement; no neurovascular complications associated with screw placement were observed.
Conclusions
The technique of CPS placement using mobile CT was shown to be safe and effective in preventing catastrophic complications associated with CPS insertion.
The free-hand technique carries a higher risk of pedicle weakening and neurovascular injuries in comparison with pedicle screw placement using a drill guide. Due to this evidence and because of some variances in the surgical method, different outcome can be expected. The objective of the study was to evaluate the disability, the back and leg pain before and at least 3 years after the surgery between examined groups.
Materials and methods
Eleven patients in drill guide and 13 in control group were randomly assigned for vertebral fusion in the lumbar and first sacral regions. Pre- and post-operative CT scans, Oswestry disability index (ODI) and visual analogue scale (VAS) for back and leg pain were taken. Post-operative evaluations of cortex perforation and statistical analysis between studied groups have been performed.
Results
Seventy-two screws were inserted in each group. All patients completed a 3-year follow-up. Comparing groups, there was no statistical significant difference in VAS and ODI before or after surgery. Cortex perforation incidence in drill guide group was 6 and in free-hand group 29 (p < 0.05). In each group, pain and disability were significantly lower as before the procedure.
Conclusions
The application of a drill guide template for pedicle screw placement is not more effective in reducing pain and disability after midterm follow-up in comparison with the free-hand technique. However, it reduces the cortex perforation incidence. Concerning this evidence, a drill guide is still an additional tool that could in the future potentially compete with other screw placement techniques.
Accurate implantation of pedicle screw in spinal deformity correction surgeries is always challenging. We have developed a method of pedicle screw placement in severe and rigid scoliosis with a multi-level 3D printing drill guide template.
Methods
From November 2011 to March 2015, ten patients (4 males and 6 females) with severe and rigid scoliosis (Cobb angle >70° and flexibility <30%)were included. Multi-level template was designed and manufactured according to the part (two or three levels) of the most severe deformity. The drill template was then placed on the corresponding vertebral surface. Then, pedicle screws were carefully inserted along the trajectories. The other screws were placed in free hand. After surgery, the positions of the pedicle screws were evaluated by CT scan and graded for validation.
Results
48 screws were implanted using templates, other 104 screws in free hand, and the accuracies were 93.8 and 78.8%, respectively, with significant difference. The deformity correction ratio was 67.1 and 41.2% in coronal and sagittal plane post-operatively, respectively. The average operation time was 234.0 ± 34.1 min, and average blood loss was 557 ± 67.4 ml.
Conclusions
With the application of multi-level template, the incidence of cortex perforation in severe and rigid scoliosis decreased and this technology is, therefore, potentially applicable in clinical practice.
The technique of pedicle screw stabilization is finding increasing popularity for use in the cervical spine. Implementing anterior transpedicular screws (ATPS) in cervical spine offers theoretical advantages compared to posterior stabilization. The goal of the current study was the development of a new setting for navigated insertion of ATPS, combining the advantage of reduced invasiveness of an anterior approach with the technical advantages of navigation.
Methods
20 screws were implanted in levels C3 to C6 of four cervical spine models (SAWBONES® Cervical Vertebrae with Anterior Ligament) with the use of 3D fluoroscopy navigation system [Arcadis Orbic 3D, Siemens and VectorVision fluoro 3D trauma software (BrainLAB)]. The accuracy of inserted screws was analyzed according to postoperative CT scans and following the modified Gertzbein and Robbins classification.
Results
20 anterior pedicle screws were placed in four human cervical spine models. Of these, eight screws were placed in C3, two screws in C4, six screws in C5, and four screws in C6. 16 of 20 screws (80 %) reached a grade 1 level of accuracy according to the modified Gertzbein and Robbins Classification. Three screws (15 %) were grade 2, and one screw (5 %) was grade 3. Grade 4 and 5 positions were not evident. Summing grades 1 and 2 together as “good” positions, 95 % of the screws achieved this level. Only a single screw did not fulfill these criteria.
Conclusion
The setting introduced in this study for navigated insertion of ATPS into cervical spine bone models is well implemented and shows excellent results, with an accuracy of 95 % (Gertzbein and Robbins grade 2 or better). Thus, this preliminary study represents a prelude to larger studies with larger case numbers on human specimens.
The Harms technique is now considered as the gold standard to stabilize C1–C2 cervical spine. It has been reported to decrease the risk of vertebral artery injury. However, the risk of vascular injury does not totally disappear, particularly due to the proximity of the trans-isthmic C2 screw with the foramen transversarium of C2. In order to decrease this risk of vertebral artery injury, it has been proposed to use a shorter screw which stops before the foramen transversarium.
Object
The main objective was to compare the pull-out strength of long trans-isthmic screw (LS) versus short isthmic screw (SS) C2 screw. An additional morphological study was also performed.
Method
Thirteen fresh-frozen human cadaveric cervical spines were included in the study. Orientation, width and height of the isthmus of C2 were measured on CT scan. Then, 3.5-mm titanium screws were inserted in C2 isthmus according to the Harms technique. Each specimen received a LS and a SS. The side and the order of placement were determined with a randomization table. Pull-out strengths and stiffness were evaluated with a testing machine, and paired samples were compared using Wilcoxon signed-rank test and also the Kaplan–Meier method.
Results
The mean isthmus transversal orientation was 20° ± 6°. The mean width of C2 isthmus was less than 3.5 mm in 35 % of the cases. The mean pull-out strength for LS was 340 ± 85 versus 213 ± 104 N for SS (p = 0.004). The mean stiffness for the LS was 144 ± 40 and 97 ± 54 N/mm for the SS (p = 0.02).
Discussion
The pull-out strength of trans-isthmic C2 screws was significantly higher (60 % additional pull-out resistance) than SSs. Although associated with an inferior resistance, SSs may be used in case of narrow isthmus which contraindicates 3.5-mm screw insertion but does not represent the first option for C2 instrumentation.
Current methods of measuring vertebral rotation by plain radiographs rely on anatomic landmarks that are not present in the postoperative spine or require advanced imaging. Furthermore, there are few studies on the incidence of crankshaft with modern pedicle instrumentation.
Questions/Purposes
We sought to (1) describe and validate a method of vertebral rotation measurement using plain radiographs and (2) measure postoperative rotation in a series of patients treated for adolescent idiopathic scoliosis.
Methods
Patients with adolescent idiopathic scoliosis treated with surgery over a 6-year period were reviewed. Patients with computed tomography (CT) scans and radiographs within 60 days of another were included. Vertebral rotation was calculated by radiographic measurements and measured directly by CT scan. As an internal control, patients with two apical pedicle screws on all radiographs were analyzed. Rotation was measured for all patients with at least 1 year of radiographic follow-up.
Results
Three thousand five hundred fifty-two instrumented spinal levels in 308 consecutive patients were reviewed. Ten patients with 93 screws were analyzed by CT and radiographs. The average discrepancy between computed tomography (CT) and radiographs was 3.3?±?1.9°, with 81.7% (76/93) within 5°. Intra- and inter-rater reliabilities for measured axial rotation were excellent (intra-class correlation coefficient (ICC)?=?0.879 and 0.900, respectively). One hundred swventy-eight patients were eligible with an average follow-up of 2.3?±?1.2 years; 84.8% (151/178) had screw(s) visible on all images at the major curve apex. The average postsurgical rotation was 3.5?±?2.9°; 19.2% (29/151) were measured to have a rotation over 5°, and 4.0% (6/151) demonstrated a rotation over 10°. Only 4.6% (7/151) of patients demonstrated a postoperative Cobb angle change over 10°.
Conclusions
Most major curves have apical pedicle screw instrumentation that can be followed by radiographs alone to measure rotation. Vertebral rotation measurement requires only plain radiographs and is a more sensitive determination for subtle postoperative crankshaft than change in Cobb angle.
