Pedicle screw accuracy in thoracolumbar fractures- is routine postoperative CT scan necessary?

Background While several studies report on accuracy rates of pedicle screws, risk factors associated with inaccurate pedicle screw positioning in patients with thoracolumbar fractures are reported rarely. CT scan as a routine postoperative control is advocated by various authors, however its necessity remains unclear. Methods Two hundred forty-five patients were included in this retrospective study. Percutaneous dorsal instrumentation was most commonly performed (n = 201). Classification of Zdichavsky et al. and Rao et al. were used to classify screw misplacement and anterior perforation was further evaluated according to the extent of perforation (< 2 mm; > 2 mm). Multivariate analysis was performed to identify risk factors for misplacement of screws. Results One thousand sixty-eight pedicle screws were inserted in 245 patients. Misplacement was found in 51 screws (4.8%) in 42 patients (17.1%) according to the classification of Zdichavsky et al. and in 75 screws (7.0%) in 64 patients (26.1%) according to the classification of Rao et al.. An anterior perforation of the vertebral cortex was found in 56 screws (5.2%). Multivariate analysis showed fracture location in the upper thoracic (p = 0.048) and lumbar spine (p = 0.013) to be the only independent predictors for screw misplacement. In addition a significant correlation between pedicle diameter and the occurrence of screw malposition was found (p = 0.003). No consequences were drawn from postoperative routine CT in asymptomatic patients. Conclusion An overall low rate of screw misplacement was found with fracture location in the upper thoracic and lumbar spine being the only factors independently associated with the risk of screw misplacement. No consequences were drawn from postoperative routine CT in asymptomatic patients. Therefore its use has to be discussed critically.

Freehand screw insertion technique without image guidance for the cortical bone trajectory screw in posterior lumbar interbody fusion: what affects screw misplacement?

OBJECTIVE Cortical bone trajectory (CBT) screw insertion using a freehand technique is considered less feasible than guided techniques, due to the lack of readily identifiable visual landmarks. However, in posterior lumbar interbody fusion (PLIF), after resection of the posterior anatomy, the pedicles themselves, into which implantation is performed, are palpable from the spinal canal and neural foramen. With the help of pedicle wall probing, the authors have placed CBT screws using a freehand technique without image guidance in PLIF. This technique has advantages of no radiation exposure and no requirement for expensive devices, but the disadvantage of reduced accuracy in screw placement. To address the problem of symptomatic breaches with this freehand technique, variables related to unacceptable screw positioning and need for revisions were investigated. METHODS From 2014 to 2020, 182 of 426 patients with single-level PLIF were enrolled according to the combined criteria of L4–5 level, excluding cases of revision and isthmic spondylolisthesis; using screws 5.5 mm in diameter; and operated by right-handed surgeons. We studied the number of misplaced screws found and replaced during initial surgeries. Using multiplanar reconstruction CT postoperatively, 692 screw positions on images were classified using previously reported grading criteria. Details of pedicle breaches requiring revisions were studied. We conducted a statistical analysis of the relationship between unacceptable (perforations > 2 mm) misplacements and four variables: level, laterality, spinal deformity, and experiences of surgeons. RESULTS Three screws in L4 and another in L5 were revised during initial surgeries. The total rate of unacceptable screws on CT examinations was 3.3%. Three screws in L4 and another in L5 breached inferomedial pedicle walls in grade 3 and required revisions. The revision rate was 2.2%. The percentage of unacceptable screws was 5.2% in L4 and 1.7% in L5 (p < 0.05), whereas other variables showed no significant differences. CONCLUSIONS A freehand technique can be feasible for CBT screw insertion in PLIF, balancing the risks of 3.3% unacceptable misplacements and 2.2% revisions with the benefits of no radiation exposure and no need for expensive devices. Pedicle palpation in L4 is the key to safety, even though it requires deeper and more difficult probing. In the initial surgeries and revisions, 75% of revised screws were observed in L4, and unacceptable screw positions were more likely to be found in L4 than in L5.

Versatile Usage of the Modified Lateral Mass Screw as an Alternative to Cervical Pedicle Screw Fixation

Objective Posterior subaxial cervical screw fixation is commonly performed using the cervical pedicle screws (CPS) and lateral mass screws (LMS); however, their compatibility is low. Modified lateral mass screws (mLMS, also called paravertebral foramen screw) fixation was introduced as a salvage technique for LMS fixation and has features of both LMS and CPS techniques. In the present study, the use of mLMS as an alternative to CPS was analyzed based on clinical results. Methods Seventy-eight screws (38 CPSs and 40 mLMSs) were inserted into 12 patients. The misplacement of the screws was evaluated by computed tomography (CT). The failure of instrumentation and instability were evaluated using plain radiographs. Results The total number of CPS misplacements was 3 (10.5%); however, neurologic complications were not observed. mLMSs were used in the middle segments of the fusion in 10 patients and 2 patients had mLMS fixation for single-level fusion. An additional bridging implant was not required for connecting both CPSs and mLMSs. Instability was not observed during the observation period (4–51 months). Complete fusion was seen in 10 patients. Conclusions The alternative mLMS fixation can decrease the risk of screw misplacement compared with CPS fixation alone and achieves adequate stability leading to fusion.

Safety, Effect and Feasibility of Percutaneous SI-Screw with and without Augmentation—A 15-Year Retrospective Analysis on over 640 Screws

Background: Minimally invasive sacroiliac-screw (SI-screw) fixation of the pelvis is used in energy trauma (Arbeitsgemeinschaft für Osteosynthesefragen (AO) classified) and fragility fractures (Fragility Fracture of the Pelvis (FFP) classified). However, available clinical data are based on small case series and biomechanical data seem to be contradictory. Methods: The present single center retrospective cohort study investigated percutaneous SI-screw fixation and augmentation over 15 years. Groups were compared concerning the general epidemiological data, mobilization, complication rates, duration of stay, and safety of SI-screw insertion. Multivariable analyses were performed using logistic regression. Results: Between 2005 and March 2020, 448 patients with 642 inserted SI-screws were identified. Iatrogenic neurological impairment was documented in 2.47% and correlated with screw misplacement. There was an increased complication risk in patients with AO type C over patients with AO type B and in FFP II over FFP III/IV patients. Cement-augmented FFP patients showed a 25% reduced stay in hospital and a reduced complication risk. Cement-associated complications were seen in 22% without correlation to neurologic impairment. Conclusions: The present study confirms the safety and usability of percutaneous SI-screw fixation, despite specific risks. Cement augmentation seems to reduce the complication risk in FFP patients and shorten hospital stay for some reasons, without increased specific complications or correlated neurological impairment.

Complications rate of and risk factors for the unplanned reoperation of degenerative lumbar spondylolisthesis in elderly patients: a retrospective single-centre cohort study of 33 patients

Background: The study aimed to investigate the complications rate of and risk factors for unplanned reoperation among elderly patients who underwent posterior lumbar fusion (PLF) for degenerative lumbar spondylolisthesis (DLS).Methods: A total of 1100 DLS patients who were older than 60 years were reviewed from January 2006 to December 2016; 33 patients underwent unplanned reoperations and were analysed and divided into two groups (group A: posterolateral fusion, 650 patients; group B: intervertebral fusion, 450 patients). Sex, body mass index (BMI), radiographic data and clinical outcome data were analysed to evaluate the complications rate of and the risk factors for unplanned reoperations.Results: A total of 33 patients underwent unplanned reoperations (3%). The patients were followed for an average of 4.20±2.25 years (group A) and 4.32±2.54 years (group B) without a significant difference. Significant differences were found in mean age, levels of involvement, hospital stay, surgery time, and blood loss between the groups. The causes of unplanned operation were wound infection, screw misplacement, neurological deficit, nonunion, and screw fracture, which were significant except for wound infection between the groups. Higher BMI (obesity), diabetes mellitus (DM), more bleeding and sex (female) were risk factors for complications. Cases of screw misplacement, neurological deficit, nonunion and screw fracture in group A were more significant than those in group B.Conclusion: Patients with higher BMI, DM, older age, posterolateral fusion, and female sex predicted a higher incidence of unplanned reoperations. Spine surgeons may need to pay more attention to their preoperative training and to improving surgical techniques that could reduce the reoperation rate.

Complications rate and risk factors in unplanned reoperation of degenerative lumbar spondylolisthesis in geriatric patients: a retrospective single-center cohort study of 33 patients

Background: The study aimed to investigate the complications rate and risk factors in unplanned reoperation among geriatric patients who underwent posterior lumbar fusion(PLF) for degenerative lumbar spondylolisthesis(DLS).Methods: 1100 DLS patients who were older than 60 years were reviewed from January 2006 to December 2016 and 33 patients underwent unplanned reoperations who were analyzed and divided to two groups(Group A: posteriolateral fusion, Group B: intervertebral fusion). Gender, body mass index (BMI), radiographic data and clinical outcomes data were analyzed to evaluate complications rate and the risk factors for unplanned reoperations.Results: 33 patients were performed by the unplanned reoperations(3%).The patients were followed up for an average of 4.20±2.25 years (Group A)and 4.32±2.54 years(Group B)without significant difference. The significant difference was found in mean age, levels involved levels, hospital stay, surgery time, blood loss between the groups. The causes of unplanned operation were: wound infection, screw misplacement, neurological deficit, nonunion, screw fracture which were significant except the wound infection between the groups. Higher BMI (obesity), diabetes mellitus(DM), more bleeding and gender(female) were the risk factors of the complications. The cases of the screw misplacement, neurological deficit, nonunion and screw fracture in group A were more significantly than in group B.Conclusion: The patients of higher BMI, DM, age, posteriolateral fusion, female predicted higher incidence of unplanned reoperations. The spine surgeons maybe need to pay more attention in their preoperative training and in improving surgical technique which could reduce the reoperation rate.

The Anteromedial Cortex of the Calcaneus: A Cadaveric Study

Category: Hindfoot Introduction/Purpose: The irregular morphology of the calcaneus obstructs its clear visualization on radiographic imaging. Particularly challenging is identifying the medial cortex given its concavity and bony overlap of the calcaneal body. Iatrogenic screw penetration of the medial wall of the calcaneus comes with increased risk of injuring the neurovascular bundle and the flexor hallucis longus tendon. Despite all intraoperative precautions, it is not infrequent to see misplaced screws in postoperative imaging. The objective of the present study is to evaluate the normal proportion of the calcaneus width to radiographically define the extent of the medial cortex on axial fluoroscopic imaging. Methods: Eight left sided fresh-frozen below-the-knee amputated cadaveric specimens were utilized for this study. Each specimen was dissected on the medial side of the hindfoot to allow visualization of the medial cortex of the calcaneus. A partial cuboid ostectomy was performed to visualize the calcaneocuboid joint and to install radiopaque markers on the borders of the anterior calcaneal facet. Finally, Harris axial views were obtained. Two independent observers measured the widths of the calcaneus on digital fluoroscopic Harris views at two levels: the maximal width at the sustentaculum tali and the maximal width at the anterior process. A ratio was calculated between these measurements. Results: The ratio between the maximal width at the anterior process and the sustentaculum ranged between 0.42 and 0.52 with an average ratio of 0.47 +/- 0.04. Conclusion: Calcaneal screw misplacement, particularly from lateral to medial, can lead to damage of the neurovascular bundle and the flexor hallucis long tendon ultimately affecting clinical outcomes. The measurements in the present study suggest a lower risk of violating the medial cortex when the length of the screw placed in the anterior process of the calcaneus is less than half of the maximal width of the calcaneus at the sustentaculum tali. As the medial cortex is difficult to visualize on intraoperative fluoroscopy, the clinical use of this normal ratio in axial views could help surgeons to avoid calcaneal screw misplacement.